1. conducting system of the heart
1.1. Direction of impulse
1.1.1. Superior Vena Cava
1.1.2. Sinoatrial (SA) Node
1.1.3. Atrioventricular (AV) Node
1.1.4. Atrioventricular bundle (AV) bundle / bundle of His
1.1.5. Left Atrioventricular (LAV) bundle
1.1.6. network of Purkinje Fibres
1.2. posses the property of autorhythmicity (generates its own electrical impulses and beats independently of nervous or hormonal control)
1.2.1. Heart rate
1.2.1.1. supplied with both sympathetic and parasympathetic nerve fibres
1.2.1.1.1. sympathetic increases heart rate
1.2.1.1.2. parasympathetic decreases heart rate
1.2.1.1.3. other factors affecting heart rate are
1.2.1.2. Heart responds to circulation hormones eg Adrenaline and thyroxine
1.3. small groups of specialised neuromuscular cells in the myocardium initiate and conduct impulses
1.3.1. causes coordinated and synchronised contraction of the heart muscle
1.4. Sino atrial (SA) node
1.4.1. is a small mass of specialised cells that lies in the wall of the right atrium
1.4.2. these cells generate these regular impulses because they are electrically unstable
1.4.2.1. this instability leads them to discharge (depolarise) regularly
1.4.2.1.1. around 60 to 80 times a minute
1.4.2.1.2. this dispoloarisation is followed by recovery (repolarisation)
1.4.2.1.3. because this node discharges quicker than any other part of the heart it normally sets the heart rate and is often referred to as the pacemaker
1.5. Atrioventricular (AV) node
1.5.1. is a small mass of neuromuscular tissue situated in the wall of the atria septum near the atrioventricular valves
1.5.2. normally merely transmits electrical signals from the atria to the ventricles
1.5.2.1. there is a 0.1 second delay here to pass through the ventricles
1.5.2.1.1. allows atria to finish contracting before ventricles start
1.5.3. has a secondary pacemaker function
1.5.3.1. takes over this role if there is a problem with the SA node or with transmission of impulses from the atria
1.5.3.1.1. discharges around 40-60 times a minute
1.5.4. atrioventricular bundle bundle (AV bundle / bundle of HIS)
1.5.4.1. this is a mass of specialised fibres that originate from the AV node
1.5.4.2. it divides into the right and left bundle branches
1.5.4.3. withing the ventricular myocardium the branches break up into fine fibres called the purkinje fibres
1.5.4.4. these fibres transmit electrical impulses from the AV node to the apex of the myocardium where the wave of ventricular begins
1.5.4.4.1. pumping blood into the pulmonary artery and the aorta
2. Direction of blood flow
2.1. Inferior vena cava
2.1.1. largest veins of the body
2.2. Superior vena cava
2.2.1. largest veins of the body
2.3. Right Atrium
2.3.1. and left atrium both contract at the same time
2.3.2. walls are thinner
2.3.2.1. assisted by gravity to pump blood to ventricles
2.4. Tricuspid Valve / Right atrioventricular valve
2.5. Right Ventricle
2.5.1. and left ventricle simultaneously contract after the artias
2.5.2. walls are thicker
2.5.2.1. work against gravity to pump blood into pulmonary artery and to the lungs
2.6. Pulmonary Valve
2.6.1. formed by 3 semilunar cusps
2.6.2. prevents backflow of blood to the right ventricle when it relaxes
2.7. Pulmonary Arteries
2.7.1. left
2.7.1.1. carry venous blood to the lungs
2.7.1.1.1. CO2 excreted
2.7.1.1.2. O2 absorbed
2.7.2. right
2.7.2.1. carry venous blood the the lungs
2.7.2.1.1. CO2 excreted
2.7.2.1.2. O2 absorbed
2.8. Lungs
2.9. Pulmonary Veins
2.9.1. two pulmonary veins from each lung
2.9.2. carr oxygenated blood back to theheart
2.10. Left Atrium
2.10.1. and right atrium both contract at the same time
2.10.2. walls are thinner
2.10.2.1. assisted by gravity to pump blood to ventricles
2.11. Mitral Valve / Left atrioventricular valve
2.12. Left Ventricle
2.12.1. and right ventricle simultaneously contract after the artias
2.12.2. walls are thicker
2.12.2.1. work against gravity to pump blood into aorta and round the body
2.13. Aortic valve
2.13.1. formed by 3 semilunar cusps
2.14. Aorta
2.14.1. first artery of general circulation
3. Arteries, Veins and Capillaries
3.1. Arteries
3.1.1. Have 3 layers
3.1.1.1. Tunica intima / Inner layer; Endothelium
3.1.1.2. Tunica media / Middle layer; Smooth muscle and Elastic tissue
3.1.1.2.1. More Elastic tissue than smooth muscle
3.1.1.3. Tunica adventitia / Outer layer; Fibrous tissue
3.1.2. Have thick walls
3.1.2.1. needed to withstand the the high pressure blood flow
3.1.2.1.1. means when cut blood spurts out
3.1.3. Arteries = Away from the heart
3.1.4. Types of artery
3.1.4.1. Arterioles
3.1.4.1.1. Small arteries
3.1.4.1.2. 3 Layers
3.1.4.1.3. also know as resistance vessles
3.1.4.2. Anastomoses
3.1.4.2.1. Form a link between main arteries supplying an area eg palm of the hand, soles of the feet or brain
3.1.4.2.2. can provide collateral circulation
3.1.4.2.3. provide adequate blood supply when artery is occluded
3.1.4.3. End arteries
3.1.4.3.1. Sole source of blood supply to tissues eg central artery to the retina of the eye
3.1.4.3.2. when occluded tissue it supply dies as no alternative blood supply
3.1.5. Main arteries
3.1.5.1. Renal
3.1.5.1.1. kidney
3.1.5.2. Hepatic
3.1.5.2.1. liver and gall bladder
3.1.5.3. Gastric
3.1.5.3.1. Stomach
3.1.5.4. Splenic
3.1.5.4.1. spleen and pancreas
3.1.5.5. Carotid
3.1.5.5.1. neck and brain
3.1.5.6. Coronary
3.1.5.6.1. heart
3.1.5.7. Peripheral
3.1.5.7.1. limbs
3.2. Veins
3.2.1. 3 layers
3.2.1.1. Tunica intima / Inner layer; Endothelium
3.2.1.2. Tunica media / Middle layer; Smooth muscle and Elastic tissue
3.2.1.2.1. not as much as in arteries as they don't need to stretch
3.2.1.3. Tunica adventitia / Outer layer; Fibrous tissue
3.2.2. Have thin walls
3.2.2.1. withstand the low pressure blood
3.2.2.1.1. when cut slow, steady blood flow escapes
3.2.3. Veins = Carry blood towards the heart
3.2.4. also know as capacitance vessels
3.2.4.1. distensible
3.2.4.2. have capacity to hold a large proportion of the bodies blood
3.2.4.2.1. 2/3 of the body's blood is in the venous system
3.2.4.2.2. allows vascular system to absorb sudden changes in blood volume
3.2.5. Have valves
3.2.5.1. prevent backflow
3.2.5.1.1. ensuring blood flows to the heart
3.2.5.1.2. assisted by skeletal muscles surrounding the veins
3.2.5.2. formed by fold of endothelium and strengthened by connective tissue
3.2.5.3. semilunar in shape
3.2.5.3.1. concave toward the heart
3.2.5.4. abundant in veins of the limbs
3.2.5.4.1. especially lower limbs where blood has to travel a considerable distance against gravity
3.2.5.5. absent in very small and very large veins in the thorax and abdomen
3.2.6. types of vein
3.2.6.1. venules
3.2.6.1.1. small veins
3.3. Capillaries
3.3.1. Wall consists of one single layer of endothelial cells
3.3.1.1. allows water and other small molecules pass through it
3.3.1.2. blood cells and plasma proteins are usually too big to pass through the capillary wall
3.3.2. form a network that joins small arterioles to small venules
3.3.3. they are the site of exchange of substances between the blood and tissue fluid that bathes the body cell
3.3.4. Entry capillary beds are guarded by precapillary sphincters (rings of smooth muscle)
3.3.4.1. they direct blood flow
3.3.4.2. Hypoxia (low oxygen levels in the tissue) and high levels of tissue waste dilate the sphincters
3.3.4.2.1. this increases blood flow through affected beds
3.3.5. types of capilllary
3.3.5.1. Sinusoids
3.3.5.1.1. significantly wider and leakier capillaries
3.3.5.1.2. found in the liver and bone marrow
3.3.5.1.3. walls are incomplete and have larger lumens than normal
3.3.5.1.4. can come directly into contact with cells outside sinusoid walls
3.3.6. capillary refill time
3.3.6.1. when area of skin is pressed it turn white
3.3.6.1.1. because blood has been squeezed out the capillary
3.3.6.2. should take less than 2 seconds for capaillary to refill (skin to turn pink again)
3.3.6.2.1. if takes longer can suggest poor perfusions or dehydration
4. Control of blood vessel diameter
4.1. Baseline, Vasoldilation and vasoconstriction
4.1.1. vasodilation
4.1.1.1. caused by decrease nerve stimulation
4.1.1.1.1. relaxes the smooth muscle thinning the vessel wall and enlarging the lumen
4.1.1.2. increase blood flow at low pressure
4.1.2. Baseline (resting)
4.1.3. sympathetic activity / Vasoconstriction
4.1.3.1. diameter of vessel lumen and tone of the smooth muscle are determined by the degree of sympathetic activity
4.1.3.2. generally constricts vessels
4.1.3.2.1. vasoconstriction
4.1.3.2.2. this increases pressure inside the vessel
4.1.4. Relationship between sympathetic stimulation and blood vessel diameter
4.1.4.1. baseline ( Resting)
4.1.4.1.1. Sympathetic stimulation
4.1.4.1.2. smooth muscle
4.1.4.1.3. thickness of vessel wall
4.1.4.1.4. diameter of lumen
4.1.4.1.5. peripheral resistance in arterioles
4.1.4.2. Vasodilation
4.1.4.2.1. Sympathetic stimulation
4.1.4.2.2. smooth muscle
4.1.4.2.3. thickness of vessel wall
4.1.4.2.4. diameter of lumen
4.1.4.2.5. peripheral resistance in arterioles
4.1.4.3. Vasoconstriction
4.1.4.3.1. Sympathetic stimulation
4.1.4.3.2. smooth muscle
4.1.4.3.3. thickness of vessel wall
4.1.4.3.4. diameter of lumen
4.1.4.3.5. peripheral resistance in arterioles
4.2. smooth muscle in the tunica media of both veins and arteries are supplied with nerves from the autonomic nervous system
4.2.1. they arise from the vasometer centre in the medulla oblongata
4.2.2. they change the diameter of the blood vessel controlling volume of blood they can contain
4.3. What vessels does it effect?
4.3.1. Mainly arterioles as their walls contain more smooth muscle
4.3.1.1. responds to sympathetic stimulation
4.3.2. Large arteries such as the aorta contain more elastic tissue meaning they can expand and recoil depending on the volume of blood passing through
4.3.3. Veins also respond to nerve stimulation but only have little smooth muscle in their tunica media
4.4. Blood flow
4.4.1. resistance to flow fluids along a tube is determined by three factors
4.4.1.1. the diameter of the tube
4.4.1.2. the length of the tube
4.4.1.3. the viscosity of the fluid
4.4.2. the diameter of the resistance vessel is known as the peripheral resistnace
4.4.2.1. major factor in blood pressure regulation
4.4.2.2. Constant adjustment of blood vessel diameter helps regulate peripheral resistance and systemic blood pressure
5. Heart
5.1. Postion
5.1.1. lies in the thoracic cavity
5.1.2. in the mediastinum (space between the lungs)
5.1.3. lies slightly more on the left than the right
5.2. organs associated with the heart
5.2.1. Inferiorly
5.2.1.1. apex rests on the central tendon of the diaphram
5.2.2. superiorly
5.2.2.1. the great blood vessels
5.2.2.1.1. aorta
5.2.2.1.2. superior vena cave
5.2.2.1.3. pulmonary artery
5.2.2.1.4. pulmonary veins
5.2.3. posteriorly
5.2.3.1. oesophagus
5.2.3.2. trachea
5.2.3.3. left and right bronchus
5.2.3.4. descending aorta
5.2.3.5. inferior vena cava
5.2.3.6. thoracic vertibrae
5.2.4. laterally
5.2.4.1. the lungs
5.2.4.1.1. left lung overlaps the left side of the heart
5.2.5. anteriorly
5.2.5.1. the sternum
5.2.5.2. ribs
5.2.5.3. intercostal muscle
5.3. roughly cone shaped, hollow muscular organ
5.4. about 10cm long
5.4.1. about the size of a fist
5.5. Structure
5.5.1. the heart wall
5.5.1.1. composed of three layers of tissue
5.5.1.1.1. Pericardium
5.5.1.1.2. myocardium
5.5.1.1.3. endocardium
5.6. Blood supply to the heart
5.6.1. Arterial Supply
5.6.1.1. heart is supplied with arterial blood from fight and left coronary arteries
5.6.1.1.1. branches from the aorta
5.6.1.1.2. they recieve 5% of the blood pumped from the heart
5.6.1.1.3. traverse the heart eventually forming a vast network of capillaries
5.6.2. Venous drainage
5.6.2.1. most venous blood is collected into a number of cardiac veins
5.6.2.1.1. these join together forming coronary sinus which opens into the right atrium
5.6.2.1.2. the remainder passes directly into the heart chambers through venus channels
6. The cardiac cycle
6.1. at rest healthy heart beat for an adult is roughly 60-80 beats per min
6.2. during each hear beat the heat contracts (Systole) and then relaxes (Diastole)
6.3. stages of the cardiac cycle
6.3.1. each cycle lasts about 0.8 of a second
6.3.2. consists of 3 components
6.3.2.1. Atrial Systole
6.3.2.1.1. contraction of the artia
6.3.2.1.2. last rougly 0.1 seconds
6.3.2.2. Ventricular Systole
6.3.2.2.1. contraction of the ventricles
6.3.2.2.2. lasts roughly 0.3 seconds
6.3.2.3. Complete cardiac diastole
6.3.2.3.1. relaxation of the atria and ventricles
6.3.2.3.2. lasts roughly 0.4 seconds
6.3.3. Direction of blood flow
6.3.3.1. Atrial systole
6.3.3.1.1. Atria contract
6.3.3.1.2. AV valves open
6.3.3.1.3. Ventricles relaxed
6.3.3.1.4. Aortic/ pulmonary valves closed
6.3.3.2. Ventricular systole
6.3.3.2.1. Atria relaxed
6.3.3.2.2. AV valves closed
6.3.3.2.3. Ventricles contract
6.3.3.2.4. Aortic / pulmonary valves open
6.3.3.3. Complete cardiac diastole
6.3.3.3.1. Atria and ventricles relaxed
6.3.3.3.2. AV valves open
6.3.3.3.3. Aortic / pulmonary valves closed
6.4. Heart sounds
6.4.1. 'Lub'
6.4.1.1. Fairly loud
6.4.1.2. Due to closure of the atrioventricular valves
6.4.1.3. corresponds with start of ventricular systole
6.4.2. 'Dup'
6.4.2.1. softer sound
6.4.2.2. due to closure of aortic and pulmonary valves
6.4.2.3. corresponds with ventricular diastole
7. Electrical changes in the heart
7.1. body tissues and fluid can conduct electricity well this allows electrical activity in the heart to be recorded on the skin surface using electrodes
7.1.1. this recording is called and Electrocardiagram (ECG)
7.2. ECG
7.2.1. recording of electrical activity in the heart
7.2.2. shows the spread of electrical signals produced by the pacemaker as it travels through the atria, the AV node and the ventricles
7.2.3. normal ECG tracing
7.2.3.1. Shows five waves
7.2.3.1.1. P wave
7.2.3.1.2. QRS complex
7.2.3.1.3. T wave
7.2.3.2. originates from the SA node
7.2.3.2.1. called Sinus rhythm
7.2.3.2.2. the rate of sinus rhythm is usually 60-100 b.p.m
7.2.4. ECG abnormalities
7.2.4.1. Faster heart rate is called tachycardia
7.2.4.2. slower heart rate is called is called bradycardia
8. Cardiac Output
8.1. amount of blood ejected from each ventricle every minute
8.1.1. expressed in Litres per min (L/min)
8.1.1.1. Calculated by multiplying Stroke volume by the heart rate (b.p.m)
8.1.1.1.1. Cardiac Output = Stroke volume x Heart rate
8.1.1.1.2. This can increase during exercise this is called cardiac reserve
8.2. Stroke volume
8.2.1. amount of blood expelled by each contraction of each ventricle
8.2.2. is determined by the volume of blood in the ventricles immediately before they contract
8.2.2.1. ie the ventricular end-diastolic volume (VEDV)
8.2.2.1.1. Sometimes called the preload
8.2.3. in healthy adult stroke volume is approx. 70 mL
8.2.4. Summary of affacting factors
8.2.4.1. VEDV
8.2.4.2. Venous return
8.2.4.2.1. Position of the body
8.2.4.2.2. skeletal muscle pump
8.2.4.2.3. respiratory pump
8.2.4.3. strength of myocardial contraction
8.2.4.4. blood volume
9. Blood Pressure (bp)
9.1. Blood pressure is the force / pressure that blood exerts on the walls of blood vessels
9.2. systemic arterial bp maintains the essential flow of blood into and out of organs of the body
9.2.1. result of discharge of blood from left ventricle into the already full aorta
9.3. can vary according to
9.3.1. time of day
9.3.1.1. bp falls at rest and during sleep
9.3.2. posture
9.3.3. gender
9.3.3.1. usually higher in women
9.3.4. age
9.3.4.1. increases with age
9.4. if bp gets to high it can
9.4.1. damage blood vessels
9.4.2. cause clots
9.4.3. bleed from sites of blood vessel rupture
9.5. if bp gets too low
9.5.1. blood flow through tissue bed can be inadequate
9.5.1.1. dangerous for essential organs
9.5.1.1.1. heart
9.5.1.1.2. kidneys
9.5.1.1.3. brain
9.6. Systolic
9.6.1. when the left ventricle contracts and pushes blood into the aorta
9.6.2. in adults this can be about 120 mmHg
9.7. diastolic
9.7.1. in complete cadiac diastole the pressure in the arteries is much lower
9.7.2. in adults this can be about 80 mmHg
9.8. Arterial blood pressure
9.8.1. measured using a sphygmomanometer
9.8.2. written as systolic pressure written above the diastolic pressure
9.9. Control of blood pressure
9.9.1. Short term regulation
9.9.1.1. on a moment to moment basis
9.9.1.2. Cardiovascular centre
9.9.1.2.1. Baroreceptors
9.9.1.2.2. Chemoreceptors
9.9.1.2.3. higher centres in the brain
9.9.1.2.4. cardiovascular centre is a collection of interconnected neurones in the medulla and pons of the brain stem
9.9.2. long term regulation
9.9.2.1. slower longer lasting changes in blood pressure
9.9.2.1.1. affected by renin-angiotensin-aldosterone system
9.9.2.1.2. also action antidiuretic hormone
10. Pulse
10.1. normally represents the heart rate
10.2. measured in bpm
10.3. averaging 60-80 bpm at rest
10.4. info obtained by pulse
10.4.1. rate at which the heart is beating
10.4.2. regularity of the heart beats
10.4.2.1. intervals between beats should be equal
10.4.3. volume / strenght of the beat
10.4.3.1. should be possible to compress the artery with moderate pressure
10.4.4. the tension
10.4.4.1. artery should feel soft and pliant under fingers
10.5. factors affecting pulse
10.5.1. when arteries supplying peripheral tissues are blocked or narrowed
10.5.2. cardiac contraction disorders
10.5.2.1. atrial fibrillation
10.6. main pulse points
10.6.1. Temporal artery
10.6.1.1. by the eye
10.6.2. Facial artery
10.6.2.1. by the jaw
10.6.3. Common carotid artery
10.6.3.1. on the neck
10.6.4. Brachial artery
10.6.4.1. about halfway up on the inside arm
10.6.5. Radial artery
10.6.5.1. on inside of the wrist
10.6.6. Femoral artery
10.6.6.1. around the hip
10.6.7. popliteal artery
10.6.7.1. behind the knee
10.6.8. posterior artery
10.6.8.1. by the ankle
10.6.9. dorsalis pedis artery
10.6.9.1. by the toes