Homeostasis

1. Feedback Systems

1.1. DYNAMIC EQUILIBRIUM

1.1.1. Condition that remains stable with fluctuating limits

1.2. SENSOR

1.2.1. Detects a change in the internal environment

1.2.2. Sends a signal to the control centre

1.3. CONTROL CENTRE

1.3.1. Sets the range with which conditions should be maintained

1.3.2. Receives information from the sensor

1.3.3. Sends signals to effectors when needed

1.4. EFFECTOR

1.4.1. Receives signals from the control centre and responds

1.4.2. Results in a change to an internal variable

1.5. NEGATIVE FEEDBACK

1.5.1. Process by which a mechanism is activated to restore conditions to their original state

1.5.2. The change in the variable being monitored triggers the control mechanism to counteract any further change in the same direction

1.5.3. Prevents small changes from becoming too large

1.5.4. Ex) Household Thermostat

1.6. POSITIVE FEEDBACK

1.6.1. Less common in the body

1.6.2. Reinforce the change

1.6.3. Move the controlled variable even from a steady state

1.6.4. Allows a discrete physiological event to be accomplished rapidly

2. Nervous System

2.1. CENTRAL NERVOUS SYSTEM

2.1.1. The body's coordination centre for mechanical and chemical actions

2.1.2. Made up of the brain and spinal cord

2.2. PERIPHERAL NERVOUS SYSTEM

2.2.1. All parts of the nervous system outside of the brain and spinal cord

2.2.2. Relays informations between the CNS and other parts of the body

2.2.3. AFFERENT SYSTEM

2.2.3.1. Component of the PNS that sense and relay information(or stimuli) from the environment to the CNS for processing

2.2.3.2. Sensory neutrons

2.2.4. EFFERENT SYSTEM

2.2.4.1. STOMATIC NERVOUS SYSTEM

2.2.4.1.1. A subdivision of the efferent system within the PNS

2.2.4.1.2. Composed of motor neurons that carry signals to skeletal muscles in response to external stimuli

2.2.4.1.3. Under conscious or voluntary control

2.2.4.1.4. Ex) Walking

2.2.4.2. Component of the PNS that carries signals away to the effectors(muscles and glands)

2.2.4.3. AUTOMATIC NERVOUS SYSTEM

2.2.4.3.1. SYMPATHETIC NERVOUS SYSTEM

2.2.4.3.2. A subdivision of the efferent system within the PNS

2.2.4.3.3. Regulates the internal environment

2.2.4.3.4. Consists of motor neutrons that control involuntary and automatic activities

2.2.4.3.5. Ex) Digestion, heart beat, breathing and smooth muscle contractions

2.2.4.3.6. PARASYMPATHETIC NERVOUS SYSTEM

3. Cells of the Nervous System

3.1. NEURON

3.1.1. Conduct nerve impulses between the different parts of the nervous system

3.1.2. Respond to stimuli

3.1.3. Release neurotransmitters

3.2. NERVES

3.2.1. Bundles of neurons surrounded by connective tissue

3.3. GLIAL CELLS

3.3.1. Nourish, protect, functionally assist, and structurally support neurons

3.3.2. Help to maintain the balance of ions surrounding the neurons and form insulating layers around the axons

3.4. GANGLIA

3.4.1. Singular; ganglion

3.4.2. Collections of nerve cell bodies located outside of the CNS

3.4.3. Sensory neurons are located in ganglia located outside of the spinal cord

3.4.4. Typically linked by synapses

3.4.5. Often forming a swelling on a nerve fibre

4. Classifying Neurons

4.1. UNIPOLAR NEURONS

4.1.1. Sensory input

4.1.2. Has a single process that extends from the cell body

4.1.3. Dendrite and axon are fused

4.1.4. Found in the PNS

4.1.5. Sensory receptors receives information in the form of a nerve impulse

4.1.6. Sensory neurons transmit impulses from the sensory receptors to the CNS

4.2. BIPOLAR NEURONS

4.2.1. Integration

4.2.2. Have one axon and one dendrite

4.2.3. Found entirely within the CNS

4.2.4. Acts as a link between sensory and motor neurons

4.2.5. Process and integrate incoming sensory information

4.2.6. relay outgoing motor information

4.3. MULTIPOLAR NEURONS

4.3.1. Motor output

4.3.2. Have one axon and many dendrites

4.3.3. Found in CNS

4.3.4. Transmit information from the CNS to effectors that respond to impulses from motor neurons

5. Nerve Impluse

5.1. neurons use electrochemical signals to communicate with other neurons, muscles and glands

5.2. MEMBRANE POTENTIAL

5.2.1. The electrical charge separation across the neural membrane

5.2.2. the potential difference across the membrane in a neuron that is not transmitting a nerve impulse

5.2.3. this is usually -70mV in an inactive/unstimulated neuron (+ve ions outside wanting to travel inside)

6. Sodium Potassium Pump

6.1. the carrier protein has a shape that allows it to take up 3 Na+ ions

6.2. Na+ binding stimulates phosphorylation by ATP and the energy is used to pump across the 3 Na+ ions

6.3. the altered shape permits the uptake of 2 K+ ions from outside the cell

6.4. K+ binding triggers release of the Pi group which restores the original conformation and release of 2 K+ ions inside the cell

7. The Brain

7.1. HINDBRAIN

7.1.1. involved with coordination and homeostasis

7.1.1.1. CEREBELLUM

7.1.1.1.1. maintenance of balance

7.1.1.1.2. receives information from the sensory stem, spinal cord and other parts of the brain

7.1.1.1.3. regulates motor movement

7.1.1.1.4. coordinates voluntary movement like posture, balance coordination and speech

7.1.1.1.5. results in smooth motor activity

7.1.1.2. MEDULLA OBLONGATA

7.1.1.2.1. controls automatic functions like breathing, digestion, heart/blood vessel function, swallowing, sneezing, coughing, hiccup, vomiting, breathing, heart rate and vasoconstriction reflex centres

7.1.1.3. PONS

7.1.1.3.1. acts as a bridge between the cerebellum and the rest of the CNS

7.1.1.3.2. assists the medulla oblongata in regulating breathing rate

7.2. MIDBRAIN

7.2.1. a small central part of the brainstem that sits above the pons

7.2.2. coordinated visual, auditory and tactile information from the eyes, ears and nose

7.2.3. acts as a relay station between the hindbrain and forebrain

7.3. FOREBRAIN

7.3.1. "cerebrum"

7.3.2. deals with thoughts, learning and emotion

7.3.2.1. THALAMUS

7.3.2.1.1. receives sensory information from the organs, coordinates signals and relays information to the cerebrum

7.3.2.1.2. involved in consciousness and sleep

7.3.2.2. HYPOTHALAMUS

7.3.2.2.1. regulates body temperature, blood pressure, heart rate, thirst, hunger, sleep, water balance and emotions

7.3.2.2.2. coordinates hormone production by the pituitary gland

7.3.2.3. CEREBRUM

7.4. CEREBRUM

7.4.1. CEREBRAL CORTEX

7.4.1.1. outer layer of the cerebrum

7.4.1.2. composed of convoluted (folded) grey matter

7.4.1.3. superficial aspect of the cerebrum

7.4.1.4. the cerebrum has two halves known as the left and right cerebral hemisphere

7.4.1.5. the left side of the brain controls the right side of the body and vice versa

7.4.1.6. the right side of the brain is associated with the intuitive thinking, visual-spatial skills, creativity, music and artistic abilities

7.4.1.7. the left side of the brain is associated with sequential and logistical ways of thinking, language and math skills

7.4.2. FRONTAL LOBES

7.4.2.1. control reasoning, critical thinking, memory, language and personaility

7.4.2.2. coordinate motor responses

7.4.3. PARIETAL LOBES

7.4.3.1. involves sensation and perception

7.4.3.2. integrates sensory input primarily from the visual system

7.4.3.3. cognition

7.4.4. divided into the right and left central hemispheres

7.4.5. contains centres for higher thought processes, learning, memory, consciousness, speech and language

7.4.6. receives and interprets sensory information

7.4.7. coordinates voluntary motor responses

7.4.8. CORPUS CALLOSUM

7.4.8.1. band of white matter connecting the left and right hemispheres

7.4.8.2. allows the two sides of the brain to communicate with each other

7.4.8.3. the cerebral cortex is divided into regions called lobes

7.4.9. OCCIPITAL LOBES

7.4.9.1. receive and process visual information

7.4.9.2. affect the ability to recognize the objects that are seen

7.4.9.3. verbal and visual memories

7.4.10. TEMPORAL LOBES

7.4.10.1. responsible for auditory reception and understanding speech

7.4.10.2. associated with accessing verbal and visual memories

8. Pituitary Gland

8.1. gland at the base of the brain that together with the hypothalamus, functions as a control centre coordinating the endocrine and nervous system

8.2. often referred to as the "master gland"

9. Anterior Pituitary

9.1. connected to the hypothalamus by special blood vessels only a few millimetres long

9.2. RELEASING HORMONES

9.2.1. trophic hormones

9.2.2. produced in hypothalamus

9.2.3. received by anterior pituitary

9.2.4. command the anterior lobe of the pituitary to initiate the production (release) of specific hormones in distant endocrine glands

9.2.5. the distant endocrine glands release their hormones into the general circulation once manufactured in response to releasing hormones

9.2.6. for each releasing hormone secretes by the hypothalamus there is a corresponding hormone synthesized by the anterior lobe of the pituitary

9.3. THYROD GLAND

9.3.1. endocrine gland on the neck

9.3.2. has two lobes

9.3.3. found at the front of the neck below the Adam's apple

9.3.4. secretes thyroid hormones which primarily influence the metabolic rate and protein synthesis

9.3.5. created from iodide and tyrosine

9.3.6. produces calcitonin which plays a role in calcium homeostasis (decreases calcium levels in blood)

9.4. though these vessels pass a group of regulating hormones produced in the hypothalamus (releasing hormones)

9.5. PITUITARY HORMONE

9.5.1. hormones produced by the anterior pituitary in response to releasing hormones

9.5.2. there are 6 principal pituitary hormones

9.5.2.1. THYROID-STIMULATING HORMONE

9.5.2.1.1. stimulates the thyroid gland

9.5.2.1.2. results in increased metabolism (oxidative respiration) of almost every tissue in the body

9.5.2.2. LUTEINIZING HORMONE

9.5.2.2.1. plays an important role in the female menstrual cycle

9.5.2.2.2. stimulates the male gonads to produce testosterone (initiates/maintains male secondary sex characteristics)

9.5.2.3. FOLLICLE STIMULATING HORMONE

9.5.2.3.1. stimulate the release of an egg in females

9.5.2.3.2. stimulates cells in male testes to produce a hormone that regulates the development of sperm

9.5.2.4. PROLACTIN

9.5.2.4.1. stimulates the breasts to produce milk

9.5.2.4.2. has many other reproductive roles

9.5.2.5. HUMAN GROWTH HORMONE

9.5.2.5.1. stimulates the growth of muscle and bone throughout the body

9.5.2.5.2. too much gigantism

9.5.2.5.3. too little dwarfism

9.5.2.6. ADRENOCORTICOTOPIC HORMONE

9.5.2.6.1. stimulates the adrenal cortex to produce corticosteroid hormones in response to stress

9.5.2.6.2. Corticosteroid hormones result in fat breakdown, Na+ and K+ blood breakdown, male secondary sex characteristics

9.5.3. each releasing hormone has a corresponding pituitary hormone

9.6. THYROXINE

9.6.1. secreted by thyroid into the intracellular space

9.6.2. does not work until it enters the intracellular space (becomes functional)

9.6.3. travels through the bloodstream

9.6.4. regulates the rate of fat/protein/carbohydrate metabolism

9.6.5. increases the rate of cellular respiration in heart/liver/skeletal muscle cells

9.6.6. plays a role in growth and development

9.7. PARATHYROID GLANDS

9.7.1. calcium homeostasis

9.7.2. the four parathyroid glands are attached to the back surface of the thyroid

9.7.3. secrete hormones that control calcium levels

10. Pancreas and Blood Sugar

10.1. PANCREAS

10.1.1. has exocrine cells that secrete digestive enzymes that break down nutrients in the small intestine

10.1.2. has endocrine cells that secrete two hormones directly into the bloodstream to maintain homeostasis and normal blood glucose level

10.2. ISLETS OF LANGERHANS

10.2.1. secrete 2 hormones that have opposite effects

10.2.2. each islet includes beta cells (produce insulin) and alpha cells (produce glucagon)

10.3. INSULIN

10.3.1. remove glucose from the blood

10.3.2. decreases blood glucose levels

10.3.3. store glycogen or fat

10.4. GLUCAGON

10.4.1. stimulates the liver to breakdown glycogen into glucose

10.4.2. glucose is released back into the blood

10.4.3. both insulin and glucagon are regulated by negative feedback mechanisms

10.5. DIABETES MELLITUS

10.5.1. chronic condition

10.5.2. inability to produce enough insulin or respond properly to insulin

10.5.3. blood glucose levels remain high after a meal because of this

10.5.4. lead to hyperglycaemia

11. The Central Nervous System

11.1. consists of the brain and spinal cord

11.2. receives sensory input, integrates the information, and initiates motor control of the body

11.3. there are two types of tissue

11.3.1. GREY MATTER

11.3.1.1. "unmylinated"

11.3.1.1.1. pinkish-grey colour

11.3.1.2. contains cell bodies

11.3.1.3. dendrites

11.3.1.4. axon terminals

11.3.1.5. where synapses are

11.3.2. WHITE MATTER

11.3.2.1. "militated"

11.3.2.2. made up of axons connecting different parts of grey matter to each other

12. Protective Mechanism

12.1. the brain is protected by bones (skull), membranes, and fluids

12.1.1. MENINGES

12.1.1.1. three layers of connective tissue surrounding the brain

12.1.1.2. cushion the brain

12.1.1.3. prevent direct circulation of blood through the cells of the CNS

12.1.2. ASTROCYTES

12.1.2.1. plural; astroglia

12.1.2.2. star-shaped

12.1.2.3. surrounded neurons in the brain and spinal cord

12.1.3. BLOOD-BRAIN BARRIER

12.1.3.1. separation of the blood and CNS

12.1.3.2. allows the brain to receive O2 and nutrients

12.1.3.3. protects the brain from the passage of toxins and pathogens

12.1.4. CEREBROSPINAL FLUID

12.1.4.1. clear, colourless liquid that fills and surrounds the brain and spinal cord

12.1.4.2. provides a mechanical barrier against shock

12.1.4.3. formed primarily in the ventricles of the brain

12.1.4.4. supports the brain

12.1.4.5. provides lubrication between surrounding bones, brain and spinal cord

12.1.4.6. ex) protects brain from head injury

13. The Spinal Cord

13.1. outside is made up of white matter

13.2. core is made up of grey matter

13.3. cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum, coccygeal vertebrae

14. Reflex Arc

14.1. A neutral circuit that travels through the spinal cord but does not require the coordination of the brain

14.2. Allows for reflex actions

14.3. Pain receptors and thermoreceptors --> afferent neutron stimulated --> impulse transmitted to spinal interneurons --> impulse relayed to efferent neuron --> rapid withdrawal of hand

15. Factors Affecting Membrane Potential

15.1. negatively charged proteins that are found only on the cytoplasmic side of the cell membrane contribute to the -ve charge in the interior of the cell

15.2. ion channels in the cell membrane allow K+ ions to passively move out of the cell more readily than Na+ moving into the cell - this makes the interior more negative overall

15.3. the inside of the cell is -vely charged compared to the outside becausee of the Na+/K+ pump activity transports Na+ and K+ to leave in

16. Action Potential

16.1. POLARIZATION

16.1.1. charge difference

16.1.2. exists because of the difference in ion distribution on either side of the cell membrane

16.1.3. due to the actions of the Na+/K+ pump

16.2. THRESHOLD POTENTIAL

16.2.1. the level of depolarization required to initiate an action potential

16.2.2. occurs when a stimulus opens voltage gated channels

16.2.3. an action potential is triggered when the threshold potential is reached

16.2.4. Na+ channels open at -50mV

16.2.5. Na+ rushes into the cell and depolarizes the membrane

16.2.6. Na+ channels are inactivated at +40mV

16.2.7. K+ channels open at +40mV

16.2.8. K+ exit the cell and hyper polarize the membrane to slightly below the resting membrane potential

16.2.9. the strength of an action potential does not change based on how strong the stimulus is

16.2.10. a strong stimulus can trigger an action potential more often than a weak stimulus

16.3. ACTION POTENTIAL

16.3.1. change in polarity across the cell membrane of an axon as the nerve impulse occurs

16.3.2. all-or-nothing phenomenon

16.4. REFRACTORY PERIOD

16.4.1. Na+ channels are unable to open and an action potential will not occur

16.4.2. action potential can't move backwards because of the refractory period

16.5. SALTATORY CONDUCTION

16.5.1. nodes of ranvier are exposed areas of unmyelinated axon

16.5.2. voltage-gated Na+ channels that initiate an action potential are concentrated at the nodes of ranvier

16.5.3. the action potential jumps from node to node

16.5.4. faster transmission

16.5.5. neurotransmitters with an excitatory effect will trigger ion channels that open to allow positive ions (Na+) to flow into the postsynaptic neuron -> membrane depolarized

16.5.6. neurotransmitters with an inhibitory effect will trigger K+ channels to open -> allow K+ to flow out -> more negative membrane potential -> hyper polarization

16.6. ACETYLCHOLINE

16.6.1. primary neurotransmitters of both the somatic and parasympathetic nervous system

16.6.2. excitatory

16.6.3. Neuromuscular junction

16.6.4. causes depolarization and contraction of a muscle fibre

17. Endoctine System

17.1. ENDOCRINE GLANDS

17.1.1. organs secrete hormones directly into the bloodstream

17.2. in vertebrates and most other animals

17.3. the CNS coordinates and regulates the diverse activities of the body using chemical signals to effect long-lasting changes in physiological activities

17.4. these hormones maintain physiological conditions within narrow bounds

17.5. consists of the endocrine glands and the hormones they secrete

17.6. HYPOTHALAMUS

17.6.1. regulates body temperature, blood pressure, heart rate, thirst, hunger, sleep, water balance and emotions

17.6.2. coordinates hormone production by the pituitary gland

17.6.3. neuroendocrine control is vested in the hypothalamus (part of the forebrain about the pituitary gland)

17.6.4. information about the body's many internal functions is processes and regulatory commands are issued

17.6.5. these commands involve matters like body temperature regulations, food/water intake, reproductive behaviour, response to pain/emotion

17.6.6. commands are issued to the pituitary gland

17.6.7. the pituitary gland sends chemical signals to various hormone-producing glands of the body

17.7. HORMONES

17.7.1. STERIOD HORMONES

17.7.1.1. steroid hormones are produced from cholesterol

17.7.1.2. they are lipid-soluble and can diffuse across the lipid bilayer of their target cell

17.7.1.3. they bind to a period receptor protein located in the cytoplasm or nucleus

17.7.1.4. the hormone receptor complex activates genes and mRNA transcription in the nucleus

17.7.1.5. ex) testosterone

17.7.1.5.1. primary male sex hormone

17.7.1.5.2. anabolic steroid

17.7.1.5.3. plays a key role in the development of male reproductive tissues (testes and prostate)

17.7.1.5.4. promotes secondary sexual characteristics (increased muscle/bone mass and body hair)

17.7.1.5.5. prevents osteoporosis

17.7.1.6. ex) estrogen or oestrogen

17.7.1.6.1. primary female sex hormones

17.7.1.6.2. responsible for the development and regulation of the female reproductive system

17.7.1.6.3. promote secondary sexual characteristics

17.7.1.6.4. synthesized from androgens by the enzyme aromatase

17.7.2. chemical messengers that are transported by the blood throughout the body to their specific target cells

17.7.3. regulating chemicals that are made at one place in the body and exert their influence at another

17.7.4. are not themselves enzymes

17.7.5. act by regulating preexisting processes

17.7.6. are recognized by specific receptors that only their target glands or tissues possess

17.7.7. constitute a chemical extension of the NS because they are produced by endocrine glands which are under the direct of the NS

17.7.8. permit the NS to issue long-term commands

17.7.9. WATER-SOLUBLE HORMONES

17.7.9.1. composed of amino acids or peptides

17.7.9.2. cannot pass through the cell membrane or their target cell

17.7.9.3. bind to a receptor protein on the cell surface

17.7.9.4. they enter the cell by receptor-mediated endocytosis

17.7.9.5. this activities a second messenger in the cell and triggers a response to the hormone

17.7.9.6. ex) epinephrine or adrenalin

17.7.9.6.1. produced by adrenal glands and certain neurons

17.7.9.6.2. plays an important role in the fight-or-flight response

17.7.9.6.3. increases blood flow to muscle, output of heart, pupil dilation and blood sugar

17.8. REGULATING THE REGULATORS

17.8.1. homeostasis requires the close cooperation of the hypothalamus and pituitary glands

17.8.2. the hypothalamus secretes releasing hormones directly into the blood

17.8.3. hormones travel to the pituitary gland where they control the production and release of other hormones

17.8.4. TROPIC HORMONES - stimulate endocrine glands to release hormones that act on other endocrine glands

17.8.5. the endocrine system is regulated by positive and negative feed back mechanisms

17.8.6. the functions of the endocrine and nervous systems often overlaps as they work closely to maintain homeostasis

18. Posterior Pituitary

18.1. linked directly to the hypothalamus by neutral connections

18.2. secretes hormones into the general blood circulation

18.3. stores and releases 2 hormones

18.3.1. ANTIDIURETIC HORMONE (ADH)

18.3.1.1. "vasopressin"

18.3.1.2. involved in regulating the rate of water reabsorption in the kidneys and intestines

18.3.1.3. constricts arterioles and raises arterial blood pressure

18.3.2. OXYTOCIN

18.3.2.1. "love hormone"

18.3.2.2. released in response to nipple stimulation (breastfeeding) to help with bonding and milk production

18.3.2.3. plays a role in social bonding

18.3.2.4. sexual reproduction (orgasm, ejaculation)

18.3.2.5. causes the uterus to contract during the labour associated with childbirth (why a nursing mother's uterus returns to normal size more quickly)

18.4. does not produce/manufacture any hormones

18.5. ADH and oxytocin are produced in the hypothalamus

18.6. transported within nerve axons to the nerve endings of the posterior lob of the pituitary

19. Adrenal Glands

19.1. ADRENAL CORTEX

19.1.1. outer region

19.1.2. regulated by hormones

19.1.3. regulates long-term stress response

19.1.4. produces 3 different types of hormones

19.1.4.1. GLUCOCORTICOIDS

19.1.4.1.1. various hormones

19.1.4.1.2. produced to help the body meet the demands of stress

19.1.4.1.3. affect blood sugar levels

19.1.4.1.4. ex) cortisol

19.1.4.2. MINEALOCORTICOIDS

19.1.4.2.1. important for regulation of salt-water balance

19.1.4.2.2. ex) aldosterone

19.1.4.3. small amounts of sex hormones

19.2. pyramid-shaped structures that sit on top of the kidneys

19.3. ADRENAL MEDULLA

19.3.1. inner gland

19.3.2. regulated by the nervous system (neurotransmitters)

19.3.3. regulates short-term stress response ("fight-or-flight")

19.3.4. produces 2 hormones; EPINEPHRINE and NOREPINEPHRINE

19.3.4.1. promotes conversion of glycogen to glucose

19.3.4.2. brings about an increase in blood sugar

19.3.4.3. brings about an increase in heart rate and cell metabolism

19.3.4.4. increase heart rate, blood pressure, blood flow to and muscles

19.3.4.5. increases breathing rate to increase the intake of O2 for energy-demanding cells

19.3.4.6. stimulates the conversation of glycogen to glucose in the liver to produce a burst of energy

19.3.4.7. effects are similar but longer lasting to those of neurotransmitters in the sympathetic NS