My Neurophysiology Concept Map

1. SENSORY PATHWAYS

1.1. Important Ascending Pathway

1.2. Dorsal Column Medial-Lemniscal Pathway

1.2.1. mainly group 1 and 2 nerve fibers

1.2.2. 1st order neurons:dorsal root ganglion

1.2.3. 2nd order neurons:nucleus gracilis & nucleus cuneatus of the medulla

1.2.4. 3rd order neurons: VPL of thalamus

1.2.5. 4th order neurons: Postcentral gyrus /primary somatosensory cortex

1.3. Anterolateral Spinothalamic Tract

1.3.1. transmits information about pain, thermal sensations, including both warm and cold sensations, sexual sensation, crude touch, tickle and itch sensations

1.3.2. mainly group 3 and 4 nerve fibers

1.3.3. 1st order neurons: dorsal root ganglion

1.3.4. 2nd order neurons: dorsal horn laminae

1.3.5. 3rd order neurons: VPL of thalamus

1.3.6. 4th order neurons: post central gyrus/ primary somatosensory cortex

1.4. Pathways for Pain

1.4.1. Neospinothalamic Tract

1.4.1.1. transmits fast type of pain

1.4.1.2. mechanical and acute thermal pain transmitted by A-delta fibers that terminate in lamina I of the dorsal horns -> anterior commissure to anterolateral pathway

1.4.1.3. some fibers terminate in the reticular areas of the brainstem but most end up in the thalamus then to the somatosensory cortex

1.4.1.4. neurotransmitter is glutamate

1.4.2. Palespinothalamic Tract

1.4.2.1. transmits slow type of pain mainly from type C pain fibers but may also transmit some signals from A-delta fibers

1.4.2.2. terminate in laminae II and III of the dorsal horns (substantia gelatinosa) -> short fibers to lamina V -> anterior commissure to anterolateral pathway

1.4.2.3. terminates widely in the brainstem before reaching the thalamus

1.4.2.4. probable neurotransmitter for slow chronic pain is substance P

1.5. Surgical Interruption of Pain Pathway

1.5.1. cordotomy

1.5.1.1. pain conducting tracts of the spinal cord on the side opposite to the pain are cut in its antolateral quadrant to interrupt the anterolateral sensory pathway

1.6. Pain Suppression

1.6.1. Analgesia System

1.6.1.1. capacity of the brain to suppress pain signals to the nervous system by activating its descending pain control system

1.6.2. Gate Control Theory

1.6.2.1. stimulation of mechanoreceptors (touch and pressure) via A-beta fibers activate inhibitory interneurons at the spinal cord that causes inhibition of small diameter A-delta and C-fibers

1.7. Referred Pain

1.7.1. a person feels pain in a part of the body that is fairly remote from the tissue causing the pain

1.7.2. branches of visceral pain fibers are shown to synapse in the spinal cord on the same second-order neurons (1 and 2) that receive pain signals from the skin

1.8. Sensory receptors

1.8.1. transduces stimulus to electrical signal

1.9. first-order neurons

1.9.1. cell body:dorsal root or cranial nerve ganglia

1.10. second-order neurons

1.10.1. cell body: spinal cord or brainstem

1.10.2. axons may decussate

1.11. third-order neurons

1.11.1. cell body: relay nucleus of the thalamus

1.12. fourth-order neurons

1.12.1. cell body: sensory cortex

1.12.2. results in conscious perception of stimulus

1.13. bradykin

1.13.1. primarily responsible for pain from tissue damage

1.14. Prostaglandins and substance P: enhance the sensitivity of the receptors

1.15. localization of referred pain via transmitted visceral pathways

1.15.1. when visceral pain is referred to the surface of the body, the person generally localizes it is in the dermatomal segment from which the visceral organ originated in the embryo

1.16. visceral pain

1.16.1. pain is felt as being deep to the body surface

1.16.2. diffuse and poorly localized and the margins of the painful zone are not well delineated; primarily transmitted through small type C fibers hence the chronic aching suffering type of pain

2. CLINICAL CORRELATIONS (1)

2.1. Sensory Alterations

2.1.1. Dyesthesia

2.1.1.1. any abnormal sensation describes as unpleasant by the patient

2.1.2. Hyperalgesia

2.1.2.1. exaggerated pain response from a normally painful stimulus

2.1.3. Hyperpathia

2.1.3.1. abnormally painful and exaggerated reaction to a painful stimulus; related to hyperalgesia

2.1.4. Hyperesthesia

2.1.4.1. exaggerated perception of touch stimulus

2.1.5. Allodynia

2.1.5.1. abnormal perception of pain from a normally nonpainful mechanical or thermal stimulus

2.1.6. Hypoalgesia

2.1.6.1. decreased sensitivity and raised threshold to painful stimuli

2.1.7. Anesthesia

2.1.7.1. reduced perception of all sensation, mainly touch

2.1.8. Analgesia

2.1.8.1. loss of perception of pain stimulus

2.1.9. Paresthesia

2.1.9.1. spontaneous positive, prickling sensation that is not unpleasant

2.1.10. Causalgia

2.1.10.1. burning pain in the distribution of one or more nerves

2.1.11. pallanesthesia

2.1.11.1. loss of perception of vibration

2.2. Herpes Zoster

2.2.1. virus infects the dorsal root ganglion

2.2.2. severe pain in the dermatomal segment subserved by the ganglion

3. CONTROL OF MOTOR FUNCTION AT THE LEVEL OF SPINAL CORD

3.1. Anterior Motor Neurons

3.1.1. located in each segment of the anterior horns of the cord gray matter

3.1.2. Two types

3.1.2.1. alpha motor neurons

3.1.2.1.1. give rise to alpha motor fibers that may branch many times after they enter the muscle and innervate the large skeletal, extramural muscle fibers

3.1.2.2. gamma motor neurons

3.1.2.2.1. transmits impulses through alpha beta motor fibers which go to the intrafusal muscle fibers that are found within muscle spindles

3.2. Other Neurons of the Spinal Cord

3.2.1. renshaw cells

3.2.1.1. inhibitory cells that transmit inhibitory signals to the surrounding motor neurons; also located in the anterior horns of the spinal cord close to motor neurons

3.2.2. interneurons

3.2.2.1. present in all areas of the cord gray matter

3.2.2.2. interconnections among the interneurons and anterior motor neurons are responsible for most of the integrative functions of the spinal cord

3.3. Spinal Cord Reflexes

3.3.1. basic unit of integrated reflex activity is the reflex arc which consist of:

3.3.1.1. afferent neuron

3.3.1.2. sense organ

3.3.1.3. one or more synapse within a central integrating station

3.3.1.4. efferent neuron

3.3.1.5. effector

3.4. Reflex Arc

3.4.1. sense organ -> afferent neuron -> synapse -> efferent neuron -> neuromuscular junction -> muscle

3.4.2. activity in the reflex arc starts in a sensory receptor with a receptor potential

3.4.3. the alpha motor neurons that supply the extrafusal fibers in the skeletal muscles are the efferent side of many reflex arcs

3.5. Clasp-knife Reflex

3.5.1. sequence of resistance followed by a sudden decrease in resistance when a limb is moved passively

3.5.1.1. examples are:

3.5.1.1.1. passive extension of the elbow

3.5.1.1.2. further stretch activates the inverse stretch reflex

3.5.1.1.3. the resistance to extension suddenly collapses and the arm extended

3.6. Flexor Reflex and the withdrawal Reflex

3.6.1. Flexor/nociceptive/pain

3.6.1.1. elicited by stimulation of pain endings, resulting in withdrawal of the limb from the stimulating object

3.6.2. Crossed extensor reflex

3.6.2.1. extension of the opposite limb to maintain balance, enabling the contralateral limb to support the additional load that is transferred to it when the flexed limb is lifted

3.7. Organization of the spinal cord for motor functions

3.7.1. The cord gray matter is the integrative area for the cord reflex

3.7.2. Sensory signals enter the cord almost entirely through the sensory roots

3.7.3. every sensory signals travels to two separate destinations: one branch of the sensory nerve terminates almost immediately in the gray matter of the cord and elicits local segmental while other branch transmits signals to higher levels of nervous systems

3.8. motor unit

3.8.1. refers to single alpha nerve fiber and all of the skeletal muscle fibers that its axon supplies

3.8.2. stimulation of a single alpha nerve fiber excites from three to several hundred skeletal muscle fibers

4. GOLGI TENDON ORGANS

4.1. Transmission of Impulses

4.1.1. signals from the tendon organs are transmitted through large, rapidly conducting type Ib nerve fibers that average 16 micrometers in diameter

4.1.2. local cord signal excites a single inhibitory interneuron that inhibits the anterior motor neuron

4.2. Golgi Tendon Reflex/Inverse Stretch Reflex

4.2.1. when the Golgi tendon organs of a muscle tendon are stimulated by increased tension in the connecting muscle; signals are transmitted to the spinal cord to cause reflex effects in the respective muscle

4.2.2. lengthening reaction

4.2.2.1. this reflex is entirely inhibitory: provides a negative feedback mechanism that prevents the development of too much tension on the muscle

4.2.2.2. a protective mechanism to prevent tearing of the muscle or avulsion of the tendon from its attachment to the bone

4.3. Transmit information about tendon tension or rate of change of tension

4.4. stretch receptors which sense contraction of muscle and activates group Ib afferent nerves

5. CLINICAL CORRELATIONS (2)

5.1. Upper motor neuron syndrome

5.1.1. Syndromes

5.1.1.1. atrophy is rare

5.1.1.2. weakness

5.1.1.3. absence of fasciculations

5.1.1.4. absence of fibrillations

5.1.1.5. hypertonia

5.1.1.6. hyperreflexia

5.1.1.7. clonus

5.1.1.8. spasticity

5.1.1.9. babinski sign

5.1.2. Damage to any part of the motor system hierarchy above the level of alpha motor neurons; some of these symptoms are opposite of those of lower motor neuron disorders

5.2. Acute Paralytic Poliomyelitis

5.2.1. a disease of the motor neuron, causing denervation of affected muscle fibers and flaccid asymmetric weakness and muscle atrophy, resulting in varying degrees of reduced mobility.

5.3. Amyotrophilic Lateral Sclerosis

5.3.1. is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control.

5.4. Central Cord Syndrome

5.4.1. is an incomplete traumatic injury to the cervical spinal cord – the portion of the spinal cord that runs through the bones of the neck

5.5. Anterior Cord Syndrome

5.5.1. is an incomplete cord syndrome that predominantly affects the anterior 2/3 of the spinal cord, characteristically resulting in motor paralysis below the level of the lesion as well as the loss of pain and temperature at and below the level of the lesion.

5.6. Brown Sequard Syndrome

5.6.1. is a rare neurological condition characterized by a lesion in the spinal cord which results in weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side.

5.7. Posterior Cord Syndrome

5.7.1. is a rare type of incomplete spinal cord injury that affects the dorsal or posterior columns of the spinal cord, which are responsible for the perception of vibration, fine-touch and body positioning

6. POSTURINGS

6.1. Decerebrate

6.1.1. rigidity occurs in the antigravity muscles -muscles of the neck, trunk, and legs and they are held in stiff extension

6.2. Decorticate

6.2.1. lesions below the midbrain but above the pontine reticular formation and lateral vestibular nucleus

7. BASAL GANGLIA

7.1. Caudate nucleus

7.1.1. head lies on the floor of the lateral ventricle and its body arches over the thalamus in the C shape tapering off into a tail lying in the roof go the inferior horn of the lateral ventricle

7.2. Putamen

7.2.1. is the most lateral of the basal ganglia and embryologically is connected to the caudate nucleus

7.3. Globus pallidus

7.3.1. output nucleus of the basal ganglia, sending inhibitory projections to the thalamus

7.4. Subthalamic nucleus

7.4.1. is a biconvex nucleus that lies inferior to the thalamus and the output nucleus of the basal ganglia

7.5. Substantia nigra

7.5.1. contains dopaminergic neurons that project to the putamen and caudate nucleus as well as the STN

7.5.1.1. Divided into:

7.5.1.1.1. pars compacta

7.5.1.1.2. pars reticulata

7.6. Pathways

7.6.1. overall effect of direct pathway is excitatory

7.6.2. overall effect of indirect pathway is inhibitory

7.7. Neurotransmitters

7.7.1. Glutamate

7.7.2. Acetylcholine

7.7.3. GABA

7.7.4. Dopamine

7.8. Direct Pathway

7.8.1. sometimes known as the direct pathway of movement, is a neural pathway within the central nervous system (CNS) through the basal ganglia which facilitates the initiation and execution of voluntary movement.

7.9. Indirect Pathway

7.9.1. sometimes known as the indirect pathway of movement, is a neuronal circuit through the basal ganglia and several associated nuclei within the central nervous system (CNS) which helps to prevent unwanted muscle contractions from competing with voluntary movements

7.10. function of the basal ganglia

7.10.1. Putamen circuit: controls complex patterns of motor activity executed by the corticospinal tract

7.10.2. Caudate circuit: plays a role in the cognitive control of motor activity

7.11. Abnormal movement from basal ganglia lesions

7.11.1. athetosis

7.11.2. hemiballismus

7.11.3. chorea

7.11.4. dystonia

7.11.5. akinesia

7.11.6. bradykinesia

7.12. Clinical correlation

7.12.1. Parkinsons Disease

7.12.1.1. a degenerative, progressive disorder that affects nerve cells in deep parts of the brain called the basal ganglia and the substantia nigra. Nerve cells in the substantia nigra produce the neurotransmitter dopamine and are responsible for relaying messages that plan and control body movement

7.12.2. Huntington Disease

7.12.2.1. is a condition that stops parts of the brain working properly over time. It's passed on (inherited) from a person's parents. It gets gradually worse over time and is usually fatal after a period of up to 20 years

8. CEREBRAL CORTEX

8.1. functional thin layer of neurons covering the convolutions of the brain

8.2. Cells of the Cerebral cortex

8.2.1. Granular cells

8.2.1.1. aka stellate cells; is a large polygonal, oval, or bipolar cell with abundant, fine, or coarsely granular eosinophilic cytoplasm, and a small, pale-staining or vesicular nucleus eccentrically located in the cell

8.2.2. Pyramidal cells

8.2.2.1. found in layers III, V & VI and are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract

8.2.3. Fusiform cells

8.2.3.1. are usually placed in the deepest cortical layer. Their dendrite projects towards the cortical surface, whereas the axon also has the possibility to be commissural, association or projection oriented

8.3. Layers I-VI

8.3.1. Layer I

8.3.1.1. Molecular layer ; has few neuronal cell bodies, contains mostly axon terminals and synapses on dendrites

8.3.2. Layer II

8.3.2.1. External granular layer ; contains mostly stellate cells

8.3.3. Layer III

8.3.3.1. External pyramidal layer ; consists of small pyramidal cells

8.3.4. Layer IV

8.3.4.1. Internal granular layer ; contains mostly stellate cells including the excitatory type

8.3.5. Layer V

8.3.5.1. Internal pyramidal layer ; dominated by large pyramidal cells

8.3.6. Layer VI

8.3.6.1. Multiform layer ; contains pyramidal, fusiform, and other types of cells. This layer is also an important origin of cortical efferents, those that target thalamic nuclei

8.4. Functions of specific cortical areas

8.4.1. Primary motor areas have direct connections with specific muscles for causing discrete muscle movements

8.4.2. primary sensory areas detect specific sensations such as:

8.4.2.1. visual

8.4.2.2. auditory

8.4.2.3. somatic

8.5. Association areas

8.5.1. includes such as:

8.5.1.1. Pareto-occipitotemporal association area

8.5.1.1.1. is the analysis the spatial coordination of body parts. This area receives visual sensory information from the periphery occipital cortex and somatic sensory information from the anterior parietal cortex

8.5.1.1.2. functional subarea

8.5.1.2. pre-frontal association area

8.5.1.2.1. functions in close association with the motor cortex to plan complex patterns and sequences of motor movements

8.5.1.2.2. important for elaboration of thoughts

8.5.1.2.3. functional subarea

8.5.1.3. limbic association area

8.5.1.3.1. found in the anterior pole of the temporal lobe, in the ventral portion of the frontal lobe, and in the cingulate gyrus lying deep in the longitudinal fissure on the mid surface of each cerebral hemisphere

8.6. Area for recognition of faces

8.6.1. prosopagnosia is the inability to recognize faces ; occurs in people who have extensive damage on the medial undersides of both occipital lobes and along the medioventral surfaces of the temporal lobes

8.7. Language

8.7.1. The means of symbolic representation of objects, actions and events therefore mirror of all higher mental activity

8.8. Cerebral Hemispheres

8.8.1. left handed individuals ; left hemisphere is still dominant of the time and co-dominance in about 15 %

8.8.2. Right handed individuals ; the left hemisphere is dominant in 90 to 95 %

8.8.3. Dominant hemisphere functions in handedness, perception of language, speech, mathematical ability

8.8.4. Non-dominant hemisphere functions in spatial perception, recognition of faces, forms and body images, music interpretation

8.9. Anatomy of language

8.9.1. language depends on the activity of a distributed neocortical network located around the Sylvian fissure

8.9.2. left-cerebral hemisphere is dominant for language in almost all right-handed persons and in more than two-thirds of left handed persons

8.9.3. perisylvian language network has two epicenters

8.9.4. posterior epicenter is wernicke area

8.9.5. anterior epicenter includes Broca area

8.9.6. Cortical areas for language

8.9.6.1. Broca's area

8.9.6.2. Wernickes area

8.9.6.3. Arcuate Fasciculus

8.9.6.4. Angular gyrus

8.9.6.5. Heschl gyri

8.10. Learning and memory

8.10.1. Non associative learning

8.10.1.1. Habituation

8.10.1.1.1. a repeated stimulus causes a response, but that response gradually diminishes as it is "learned" that the stimulus is not important

8.10.1.2. Dishabituation

8.10.1.2.1. the recovery of responsiveness to a stimulus that has undergone habituation training due to the recent occurrence of an extraneous stimulus

8.10.1.3. Sensitization

8.10.1.3.1. a stimulus results in a greater probability of a subsequent response when it is learned that the stimulus is important

8.10.2. Associative learning`

8.10.2.1. Classical conditioning

8.10.2.1.1. there is a temporal relationship between a conditioned stimulus and an unconditioned stimulus that elicits an unlearned involuntary response

8.10.2.2. Conditioned reflex

8.10.2.2.1. a reflex response to a stimulus that previously elicited little or no response; acquired by repeatedly pairing the stimulus with another stimulus that normally does produce the response

8.11. Pavlov's classic experiment

8.11.1. Pavlov found that for associations to be made, the two stimuli had to be presented close together in time (such as a bell). He called this the law of temporal contiguity. If the time between the conditioned stimulus (bell) and unconditioned stimulus (food) is too great, then learning will not occur.

8.12. Operant Conditioning

8.12.1. sometimes referred to as instrumental conditioning, is a method of learning that employs rewards and punishments for behavior. Through operant conditioning, an association is made between a behavior and a consequence (whether negative or positive) for that behavior.

8.13. Classification of memories

8.13.1. Declarative memory

8.13.1.1. memory of the various details of an integrated thought such as the memory of an important experience

8.13.2. Skills memory

8.13.2.1. frequently associated with motor activities of the person's body

8.14. Temporal categories of memories

8.14.1. Short-term (immediate)

8.14.1.1. last for seconds

8.14.2. intermediate long-term (recent)

8.14.2.1. last for days to weeks but then fade away

8.14.3. long-term memory (remote)

8.14.3.1. can be recalled up to years or even a lifetime later

8.15. Facilitation and synaptic inhibition

8.15.1. when the sensory terminal is stimulated repeatedly but without stimulation of the facilitator terminal, signal transmission at first is great but becomes less and less intense with repeated stimulation until transmission ends

8.16. Consolidation of memory

8.16.1. conversion of short term to long term memory

8.17. The case of HM: Defining a link between brain function and memory

8.17.1. his case led to greater understanding of the link between the temporal lobe and declarative memory

8.18. Memory loss/amnesia

8.18.1. is a general term that describes memory loss. The loss can be temporary or permanent, but 'amnesia' usually refers to the temporary variety. Causes include head and brain injuries, certain drugs, alcohol, traumatic events, or conditions such as Alzheimer's disease

8.19. Two anatomic structures that are of central importance in memory function

8.19.1. diencephalon (thalamus)

8.19.1.1. lesion can cause retrograde amnesia

8.19.2. hippocampal formation

8.19.2.1. lesion can cause an anterograde amnesia

8.20. two main types of amneisa

8.20.1. anterograde

8.20.1.1. ability to memorize new things is impaired or lost because data does not transfer succesfully from the conscious short-term memory into permanent long-term memory

8.20.2. retrograde

8.20.2.1. type of amnesia tends to affect recently formed memories first. Older memories, such as memories from childhood, are usually affected more slowly. Diseases such as dementia cause gradual retrograde amnesia

8.21. Clinical correlates

8.21.1. Korsakoff syndrome

8.21.1.1. is a disorder that primarily affects the memory system in the brain. It usually results from a deficiency of thiamine (vitamin B1), which may be caused by alcohol abuse, dietary deficiencies, prolonged vomiting, eating disorders, or the effects of chemotherapy

8.21.2. Alzheimer disease

8.21.2.1. the most common type of dementia. It is a progressive disease beginning with mild memory loss and possibly leading to loss of the ability to carry on a conversation and respond to the environment. Alzheimer's disease involves parts of the brain that control thought, memory, and language

8.22. Limbic system

8.22.1. is the part of the brain involved in our behavioural and emotional responses, especially when it comes to behaviours we need for survival: feeding, reproduction and caring for our young, and fight or flight responses

8.22.2. Functional anatomy

8.22.2.1. The limbic system is a collection of structures involved in processing emotion and memory, including the hippocampus, the amygdala, and the hypothalamus. The limbic system is located within the cerebrum of the brain, immediately below the temporal lobes, and buried under the cerebral cortex (the cortex is the outermost part of the brain).

8.22.3. Vegetative and endocrine control functions of the hypothalamus

8.22.3.1. Cardiovascular regulation

8.22.3.2. Body temperature regulation

8.22.3.3. Body water regulation

8.22.3.4. Gastrointestinal and feeding regulation

8.22.3.5. Hypothalamic control of endocrine hormone secretion by the anterior pituitary gland

8.22.4. Functions of the hypothalamic nuclei

8.22.4.1. synthesizing and secreting neurohormones, the nuclei of the hypothalamus act as a conduit between the nervous and endocrine systems via the pituitary gland (hypophysis), regulating homeostatic functions such as hunger, thirst, body temperature, and circadian rhythms.

8.22.5. Important components

8.22.5.1. hippocampus

8.22.5.1.1. receives sensory signals and relay them to the other areas of the limbic system to initiate behavioral reactions

8.22.5.2. amygdala

8.22.5.2.1. regulates similar autonomic functions and secretion of hormones as the hypothalamus

8.23. Electroencephalogram (EEG)

8.23.1. is a test that detects electrical activity in your brain using small, metal discs (electrodes) attached to your scalp. Your brain cells communicate via electrical impulses and are active all the time, even when you're asleep. This activity shows up as wavy lines on an EEG recording. An EEG is one of the main diagnostic tests for epilepsy. An EEG can also play a role in diagnosing other brain disorders.

8.23.2. Cortical Evoked Potentials

8.23.2.1. EEG change that can be elicited by a stimulus and best recorded from the part of the skull located over the cortical being activated

8.23.2.2. visual evoked potential

8.23.2.3. somatosensory evoked potential

8.23.2.4. auditory evoked potential

8.23.3. Awake EEG

8.23.3.1. Most waves of 8 Hz and higher frequencies are normal findings in the EEG of an awake adult. Waves with a frequency of 7 Hz or less often are classified as abnormal in awake adults, although they normally can be seen in children or in adults who are asleep

8.24. Sleep

8.24.1. NREM Sleep

8.24.1.1. Stage 1 (5%)

8.24.1.2. Stage 2 (45%)

8.24.1.3. Stage 3 & 4 (25%)

8.24.2. Rapid Eye movement sleep (25%)

8.24.2.1. Autonomic Changes

8.24.2.2. Active form of sleep

8.24.2.3. Not understood why REM sleep occurs

8.24.3. Other features during sleep

8.24.3.1. stage 2 ; bruxism (teeth grinding)

8.24.3.2. stage 3 and 4 (slow wave sleep) ; somnambulism or sleep walking, night terrors, nocturnal enuresis or bedwetting

8.24.3.3. REM sleep ; memory processing and consolidation

8.24.4. Mechanism of sleep

8.24.4.1. Now viewed as an active process, affected by neurotransmitters including serotonin, norepinephrin, acetylcholine, histamine and GABA

8.24.5. Circadian rhythm

8.24.5.1. are physical, mental, and behavioral changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark and affect most living things, including animals, plants, and microbes. Chronobiology is the study of circadian rhythms

8.24.6. Pineal gland

8.24.6.1. main function is to receive information about the state of the light-dark cycle from the environment and convey this information to produce and secrete the hormone melatonin

8.24.6.2. Diurnal rhythms of compounds involved in melatonin synthesis in the pineal gland

8.24.6.2.1. Pinealocytes synthesize melatonin from serotonin and maintained at a low-level during daylight hours

8.24.6.2.2. Locus ceruleus-Norepinephrine , Raphe nuclei- Serotonin , Pontine reticular formation- Acetylcholine, Posterior hypothalamic nuclei- Histamine , Preoptic nuclei -GABA

8.24.7. Importance of sleep

8.24.7.1. Neural maturation

8.24.7.2. facilitation of learning and memory

8.24.7.3. cognition

8.24.7.4. conservation of metabolic energy

8.24.8. Clinical correlates

8.24.8.1. Jet lag

8.24.8.1.1. is a temporary sleep problem that can affect anyone who quickly travels across multiple time zones. Your body has its own internal clock (circadian rhythms) that signals your body when to stay awake and when to sleep

8.24.8.2. Insomnia

8.24.8.2.1. is a sleep disorder in which you have trouble falling and/or staying asleep. The condition can be short-term (acute) or can last a long time (chronic). It may also come and go. Acute insomnia lasts from 1 night to a few weeks. Insomnia is chronic when it happens at least 3 nights a week for 3 months or more.

8.24.8.3. Narcolepsy

8.24.8.3.1. is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep. People with narcolepsy often find it difficult to stay awake for long periods of time, regardless of the circumstances. Narcolepsy can cause serious disruptions in your daily routine

8.24.8.4. Parasomnias

8.24.8.4.1. is a sleep disorder that involves unusual and undesirable physical events or experiences that disrupt your sleep. A parasomnia can occur before or during sleep or during arousal from sleep. If you have a parasomnia, you might have abnormal movements, talk, express emotions or do unusual things

9. SOMATOSENSORY SYSTEM

9.1. Sensory Receptors

9.1.1. mechanoreceptors

9.1.2. proprioceptors

9.1.3. thermoreceptors

9.1.4. nociceptors

9.1.5. electromagnetic receptors

9.1.6. chemoreceptors

9.2. Adequate Stimulus

9.2.1. neurons called rods in the retina of the eye capture photons of light

9.2.2. photons of light activate a chemical process in rods that triggers neural signals

9.3. Differential Sensitivity of Receptors

9.3.1. rods and cones of eyes responsive to light

9.3.2. non-responsive to normal changes of heat, cold,pressure on the eyeballs, or chemical changes in the blood

9.3.3. osmoreceptors of the supraoptic nuclei in the hypothalamus detect minute changes in the osmolality of body fluids

9.3.4. never been known to respond to sound

9.4. Receptive Field

9.4.1. excitatory

9.4.2. inhibitory

9.4.3. localization

9.4.3.1. lateral inhibition

9.4.3.2. blocks spread of excitatory signals

9.4.3.3. increases the degree of contrast in the sensory pattern perceived in the cerebral cortex

9.4.4. Type 1 units

9.4.4.1. small receptive fields with well defined borders

9.4.4.2. more precise perceptions

9.4.4.3. receptive field is circular or ovoid within or which there is relatively uniform and high sensitivity to stimuli that decreases sharply at the border

9.4.5. Type 2 units

9.4.5.1. wider perceptive fields with poorly defined border

9.4.5.2. less precise perception

9.4.5.3. only a single point of maximal sensitivity from which there is a gradual reduction in sensitivity with distance

9.5. Sensory Transduction

9.5.1. process by which an environmental stimulus activates a receptor

9.5.2. conversion typically involves opening or closing of ion channels

9.5.3. current flow then leads to a change in membrane potential called a receptor potential

9.6. Receptor Potential

9.6.1. leads to a change in membrane potential

9.6.1.1. depolarization

9.6.1.2. hyperpolarization

9.6.2. mechanisms of receptor potentials

9.6.2.1. mechanical deformation of the receptor, opens ion channels

9.6.2.2. application of a chemical to the membrane, also open ion channels

9.6.2.3. change of the temperature of the membrane, which alters the permeability of the membrane

9.6.2.4. allows ions to flow through membrane channels

9.7. "Labeled line" Principle

9.7.1. nerve fibers are specific for transmitting only one modality of sensation

9.7.1.1. modality of sensation

9.7.1.1.1. pain

9.7.1.1.2. touch

9.7.1.1.3. sight

9.7.1.1.4. sound

9.7.2. each nerve tract terminates at a specific point in the central nervous system, and the type of sensation felt when a nerve fiber is stimulated

9.8. Receptor Adaptation

9.8.1. adapt either partially or completely to any constant stimulus after a period of time

9.8.2. when a continuous sensory stimulus is applied, the receptor responds at a high impulse rate at first then progressively slower rate until the rate of action potentials decreases

9.9. Patterns of Adaptation

9.9.1. Phasic receptors

9.9.1.1. pacinian corpuscles

9.9.1.2. meissner's corpuscles

9.9.1.3. hair receptors

9.9.2. Tonic receptors

9.9.2.1. merkel's receptors

9.9.2.2. Ruffini endings

9.9.2.3. pain receptors

9.9.2.4. chemoreceptors

9.9.2.5. baroreceptors

9.9.2.6. joint capsule receptors

9.9.2.7. muscle spindle

10. SOMATIC SENSATIONS

10.1. Classifications of Somatic Sensations

10.1.1. mechanoreceptive somatic senses

10.1.2. thermoreceptive senses

10.1.3. pain sense

10.2. Mechanoreceptors

10.2.1. free nerve endings

10.2.2. meissner's corpuscle

10.2.3. merkel's receptors

10.2.4. hair follicle receptors

10.2.5. Ruffini's corpuscles

10.2.6. pacinian corpuscles

10.3. Thermoreceptors

10.3.1. cold receptors

10.3.1.1. quiescent above 36 degrees celsius

10.3.1.2. involves TRPM8

10.3.1.3. menthol

10.3.1.4. transmitted by both A-delta and C fibers

10.3.2. warm receptors

10.3.2.1. inactive above 45 degrees celsius

10.3.2.2. involves TRP channels in the family of vanilloid receptors

10.3.2.3. capsaicin

10.3.2.4. transmitted mainly by C fibers

10.4. Nociceptors

10.4.1. mechanical/thermal

10.4.1.1. sharp pain

10.4.1.2. pricking pain

10.4.2. polymoidal/chemical

10.4.2.1. high-intensity mechanical

10.4.2.2. chemical stimuli or mechanical stimuli

10.4.2.3. hot and cold stimuli

10.5. Segmental Fields of Sensation

10.5.1. dermatomes

10.5.1.1. each spinal nerve innervates a "segmental field" of the skin

10.5.2. determine the level in the spinal cord at which a cord injury has occurred when the peripheral sensations are disturbed by the injury

10.6. Somatosensory Cortex

10.6.1. map of the human cerebral cortex, showing that it is divided into about 50 distinct areas called Brodmann's areas

10.6.2. neurologists and neurophysiologists utilize this map to refer to different functional areas

10.7. Somatosensory Areas

10.7.1. primary somatosensory cortex

10.7.1.1. brodmann's area 3,2,1

10.7.1.2. somatosensory area 1 has a higher degree of localization of the different parts of the body

10.7.1.3. somatosensory area 2 localization is poor

10.7.2. somatosensory association area

10.7.2.1. Brodmann's area 5&7A

10.7.2.2. receives input from the primary somatosensory cortex, thalamus, visual and auditory cortex

10.7.2.3. for higher level of somatosensory interpretation

10.7.2.4. has poor localization

10.8. Types of Pain

10.8.1. fast pain

10.8.1.1. felt within 0.1 second after the stimulus is applied

10.8.1.2. A-delta fibers

10.8.1.3. sharp, pricking, acute and electric pain

10.8.2. slow pain

10.8.2.1. begins only after 1 second, increases slowly over many seconds, sometimes even minutes

10.8.2.2. C fibers

10.8.2.3. slow burning pain, aching pain, throbbing pain, nauseous pain, chronic pain

11. MUSCLE SENSORY RECEPTORS

11.1. Receptor Function of the Muscle Spindle

11.1.1. stretch receptors that detect changes in muscle length when extramural muscle fibers are either shortened or lengthened

11.1.2. each muscle spindle is built of 3-12 intrafusal muscle fibers

11.1.3. central region of intrafusal muscle fiber has few or no contractile components, it functions more as a sensory receptor

11.1.4. central region of intrafusal muscle fiber has few or no contractile components; it functions more as a sensory receptor

11.1.5. end portions do contract and are stimulated by type A alpha gamma motor fibers

11.1.6. remember type A alpha nerve fibers innervate the extramural skeletal muscle

11.2. Excitation of the Muscle Spindle

11.2.1. can be excited in two ways

11.2.1.1. lengthening the whole muscle stretches the mid-portion of the spindle and therefore, excites the receptor

11.2.1.2. even if the length of the entire muscle does not change, contraction of the end portions of the spindle's intrafusal fibers stretches the midportion of the spindle and therefore excites the receptor

11.3. Division of the Intrafusal Fibers

11.3.1. two types:

11.3.1.1. nuclear bag muscle fibers

11.3.1.1.1. several muscle fiber nuclei are congregated in expanded "bags" in the central portion of the receptor area

11.3.1.2. nuclear chain fibers

11.3.1.2.1. half as large in diameter and half as long as the nuclear bag fibers and have nuclei aligned in a chain throughout the receptor area

11.4. Innervations of the Muscle Spindle

11.4.1. Sensory innervation

11.4.1.1. Group Ia (primary) afferent nerves

11.4.1.1.1. innervate the central region of both nuclear bag and nuclear chain fibers

11.4.1.1.2. detect the velocity of length change

11.4.1.2. Group II (secondary) afferent nerves

11.4.1.2.1. innervate the nuclear chain fibers only

11.4.1.2.2. detect the length of muscle fiber

11.4.2. Motor innervation

11.4.2.1. Dynamic gamma motor neurons

11.4.2.1.1. synapse on nuclear bag fibers in plate endings

11.4.2.2. static gamma motor neurons

11.4.2.2.1. synapse on nuclear chain fibers in trail endings

11.5. Primary and Secondary Ending Response

11.5.1. Static Response

11.5.1.1. when the receptor portion of the muscle is stretched slowly, the number of impulses transmitted from both the primary and the secondary endings increases and the endings continue to transmit these impulses for several minutes

11.5.2. Dynamic Response

11.5.2.1. when the length of the spindle receptor increases suddenly, the primary ending (only) is stimulated

11.5.2.2. means that the primary ending responds extremely actively to a rapid rate of change in spindle length

11.6. Muscle Stretch Reflex/Myotatic Reflex

11.6.1. simplest manifestation of muscle spindle function

11.6.2. whenever a muscle is stretched suddenly, excitation of the spindles causes reflex contraction of the large skeletal muscle fibers of the stretched muscle

11.6.3. monosynaptic pathway

11.7. Smoothing Muscle Contraction

11.7.1. important function of the stretch reflex is its ability to prevent oscillation or jerkiness of body movements or its damping or smoothing function

11.7.2. signals from the spinal cord are often transmitted in an unsmooth form, increasing in intensity then decreasing and so on and forth.

11.8. Two special types of sensory receptors:

11.8.1. muscle spindles

11.8.1.1. distributed throughout the belly of the muscle

11.8.1.2. send information to the nervous system about muscle length or rate of change of length

11.8.2. Golgi tendon organs

11.8.2.1. located in the muscle tendons

11.8.2.2. transmit information about tendon tension or rate of change of tension

11.8.3. purpose of muscle sensory receptors

11.8.3.1. intrinsic muscle control at a subconscious level through the spinal cord, cerebellum and cerebral cortex

12. CONTROL OF MOTOR FUNCTION AT THE LEVEL OF THE CORTEX

12.1. descending pathways

12.1.1. Pyramidal tract

12.1.1.1. refers to the corticospinal tract

12.1.1.2. most important output pathway from the motor cortex

12.1.1.3. fibers originate from giant pyramidal cells called Betz cells from layer V of the primary motor cortex

12.1.2. extrapyramidal tract

12.1.2.1. used to denote all portions of the brain and brainstem that contribute to motor control but are not part of the pyramidal system

12.1.2.2. include pathways through the basal ganglia, the reticular formation, the vestibular nuclei and red nuclei

12.1.3. First-order neuron: cell body in the cerebral cortex

12.1.4. Second-order neuron: internuncial neuron situated in the anterior gray column of the spinal cord

12.1.5. Third-order neuron: lower motor neuron in the anterior gray column, with its axon innervating the skeletal muscle through the root and spinal nerve

12.2. motor cortex

12.2.1. anterior to the central cortical sulcus

12.2.2. occupies approximately the posterior one third of the frontal lobes

12.2.3. divided into three subareas:

12.2.3.1. primary motor cortex

12.2.3.2. premotor area

12.2.3.3. supplementary motor area

12.3. primary motor cortex

12.3.1. lies in the first convolution of the frontal lobes anterior to the central sulcus

12.3.2. corresponds to Brodmann's area 4

12.3.3. responsible for voluntary movement of the body

12.4. topographical representation

12.5. premotor area

12.5.1. lies 1 to 3 centimeters anterior to the primary motor cortex

12.5.2. extends inferiorly into the Sylvia fissure and superiorly into the longitudinal area

12.5.3. generates a motor image and subsequent pattern of muscle activity required to achieve the motor image

12.5.4. contains motor neurons

12.6. supplementary motor area

12.6.1. lies mainly in the longitudinal fissure but extends a few centimeters onto the superior frontal cortex

12.6.2. functions in concert with the premotor area to provide body-wide attitudinal movements, fixation movements of the different segments

12.6.3. concerned with bimanual movements

12.7. specialized areas of motor control

12.7.1. Broca's area (motor speech area)

12.7.2. voluntary eye movement field

12.7.3. head rotation area

12.7.4. area for hand skills

12.7.5. closely associated with the eye movement field, it directs the head toward different objects

12.8. corticobulbar tract

12.8.1. tract arises primarily from areas of the motor cortex related to the head and face

12.9. cranial nerve nuclei

12.10. extrapyramidal tracts

12.10.1. reticulospinal tract

12.10.1.1. pontine reticulospinal tract

12.10.1.1.1. arises from nuclei in the medial pontine reticular formation, descends ipsilaterally, and projects to the medial and anterior motor neurons of the spinal cord

12.10.1.2. medullary reticulospinal tract

12.10.1.2.1. arises from the medullary reticular formation, descends bilaterally and projects to motor neurons in the lateral spinal cord

12.11. vestibulospinal tract (medial)

12.11.1. the medial vestibulospinal tract, also called the descending medial longitudinal fascicles, arises mainly in the medial vestibular nucleus

12.12. vestibulospinal tract (lateral)

12.12.1. it descends ipsilaterally in the anteromedial area of the brainstem and travels in the anterior white column of the spinal cord

12.13. rubrospinal tract

12.13.1. functions closely with the corticospinal tract and together forms the lateral motor system of the spinal cord

12.14. tectospinal tract

12.14.1. the tectospinal tract originates in the superior colliculus of the midbrain and responsible for orienting the head and neck during eye movements

12.15. corticospinal tract

12.15.1. pathway for voluntary,discrete,skilled movements, especially those of the distal part of the limbs

12.15.2. downward through the brain stem, forming the pyramids of the medulla

12.15.3. most of the pyramidal fibers then cross in the lower medulla to the opposite side and descend into the lateral corticospinal tracts (80%) of the cord

13. MOTOR NEURON SYNDROME

13.1. LOWER MOTOR NEURON SYNDROME symptoms

13.1.1. the effects can be limited to small group of muscles

13.1.2. muscle atrophy

13.1.3. weakness

13.1.4. fasciculation

13.1.5. fibrillation

13.1.6. hypotonia

13.2. LOWER MOTOR NEURON SYNDROME damage to alpha motor neurons results in a characteristic set of symptoms called the lower motor neuron syndrome

13.2.1. This damage usually arises from certain diseases that selectively affect motor neurons (such as polio) or from localized lesions near the spinal cord

13.3. UPPER MOTOR NEURON SYNDROME symptom

13.3.1. spastic or increased muscle tone

13.3.2. hyperactive tendon reflexes and positive extensor plantar reflex (babinski sign)

13.4. UPPER MOTOR NEURON SYNDROME damage to any part of the motor system hierarchy above the level of alpha motor neurons

14. CEREBELLUM

14.1. Is a major structure of the hindbrain that is located near the brainstem. This part of the brain is responsible for coordinating voluntary movements. It is also responsible for a number of functions including motor skills such as balance, coordination, and posture.

14.2. Three main lobes

14.2.1. anterior lobe

14.2.2. posterior lobe

14.2.3. flocculonodular lobe

14.2.3.1. oldest; developed along with the vestibular system for equilibrium

14.3. hemispheres are subdivided into intermediate zones and lateral zones

14.3.1. vermis (midline structure)

14.3.2. intermediate zone

14.3.3. lateral zone

14.4. layers of the cerebellar cortex

14.4.1. molecular layer

14.4.1.1. contains two main types of neurons: stellate cells and basket cells, which are scattered among dendritic ramifications and numerous thin axons that run parallel to the long axis of the folia.

14.4.2. purkinje layer

14.4.2.1. They are the only cells that emit signals from the cerebellar cortex that is the outer layer of the cerebellum, though they can receive input from hundreds of thousands of cells

14.4.3. granule cell layer

14.4.3.1. Cerebellar granule cells form the thick granular layer of the cerebellar cortex and are among the smallest neurons in the brain. (The term granule cell is used for several unrelated types of small neurons in various parts of the brain.)

14.5. neuronal circuit of the functional unit is from a deep nuclear cell

14.6. deep cerebellar nuclei

14.6.1. dentate nucleus

14.6.2. globose and emboli form

14.6.3. fastigial nucleus

14.7. functional divisions of the cerebellum

14.7.1. cerebrocerebellum

14.7.1.1. is concerned with the regulation of highly skilled movements, especially the planning and execution of complex spatial and temporal sequences of movement (including speech).

14.7.2. spinocerebellum

14.7.2.1. receives somatosensory input from the spinal cord; it uses this information to modify descending motor commands to facilitate movement, maintain balance, and control posture.

14.7.3. vestibulocerebellum

14.7.3.1. region of the cerebellum found in the flocculonodular lobe that receives vestibular and visual information; it is involved with balance, vestibular reflexes, and eye movements.

14.8. efferent cerebellar pathways

14.8.1. globose-emboliform-rubral pathway

14.8.1.1. influences ipsilateral motor activity

14.8.2. dentatothalamic pathway

14.8.2.1. influences ipsilateral motor activity

14.8.3. fastigial vestibular pathway

14.8.3.1. influences ipsilateral extensor muscle tone

14.8.4. fastigial reticular pathway

14.8.4.1. influences ipsilateral muscle tone

14.9. clinical manifestations of cerebellar lesions

14.9.1. ataxia

14.9.2. dysmetria

14.9.3. intention tremor

14.9.4. dysdiadochokinesia

14.9.5. dysarthria

14.9.6. nystagmus

14.9.7. hypotonia

14.9.8. cognitive affective syndrome