Circulatory Notes
K1. HEART STRUCTURE AND FUNCTION
Key to Heart Diagram
P. septum - separates left and right ventricles
Q. posterior vena cava - drains blood from lower body into left ventricle
R. anterior vena cava - drains blood from upper body into left ventricle
S. pulmonary trunk - unoxygenated blood from r. ventricle to lungs, branches into l. and r. pulmonary arteries
T. aorta - oxygenated blood from l. ventricle to body
U. right atrium - pumps blood into right ventricle
V. left atrium - pumps blood into left ventricle
W. left ventricle - pumps blood into aorta to systemic system
X. a semi lunar valve, one at the exit of ech ventricle, prevents backflow of blood into ventricle
Y. right ventricle - pumps unoxygenated blood into pulmonary artery to lungs
Z. an atrioventricular valve - one between each atrium and ventricle, prevents backflow of blood from ventricles into atria.
Not shown on diagram
chordae tendineae - fibres running from the atrioventricular valves to the bottom of the ventricles, prevent the atrioventricular valves from collapsing backwards
coronory arteries and veins - on the outside of the heart. Arteries branch off the aorta and supply the heart muscle with oxygenated blood. Veins return to vena cava .
K.2 NODES
The left and right side beat in syncronization (together).
- both atrium contract, then both ventricles.
- the heartbeat is independent, it can beat without nervous stimulation.
There are two nodes (comb. of muscle and nervous tissue)
i) S - A (sino atricular) node on upper right atrium .
- initiates heratbeat
- sends out signal every 0.85 seconds
- causes atria to contract
ii) A - V (atrio ventricular) node on lower right atrium .
- when signal from S-A node reaches here, the A - V node causes the ventricles to contract.
- ventricles contract from the bottom, upwards.
Perkinje fibres transfer the impulses to the bottom of the ventricle and spread them upwards over the surface of the ventricles.
K3. REGULATION OF HEARTBEAT - NERVES
Autonomic control
a) Heartbeat
- The heartbeat is also under nervous control.
- The heartbeat centre is in the brain (medulla oblongata) and it controls the pulse rate via the autonomic nervous system.
- can speed up the heart (via sympathetic nerves) or slow it down (via parasympathetic nerves).
- many factors (O2, blood pressure, emergency etc.) can determine which system is activated.
K5. & K6. BLOOD PRESSURE
- Systole - contraction of the ventricles
- pumping action
- highest blood pressure / normal = 120 (mm of Hg)
- Diastole - relaxation of the ventricles
- chambers refilling
- lowest blood pressure / normal = 80
Blood pressure is given as a ratio of systole over diastole
- 120/80 is normal, in the brachial artery of the arm.
- varies considerably throughout the body.
K4. BLOOD PRESSURE - HYPER AND HYPOTENSION
Hypertension is when blood pressure is higher than expected.
- usually an indication of cardiovascular disease.
- eg. 150/100
Hypotension is when blood pressure is lower than expected.
-eg. 100/60
Pressure
- a number of factors contribute
- sympathetic nerves increase blood pressure
- inc. Na+ by kidneys or diet increase blood pressure
- arterioles constricting increase blood pressure
- atherosclerosis increases blood pressure
Atherosclerosis - accumulation of soft masses of fatty material, esp. cholesterol, beneath inner linings of arteries. These protrude and interfere with blood flow and increase blood pressure. The presence of hard plaque on artery walls can cause blood to form clots. If the clots stay in place they will block blood flow in the artery (thrombus). An embolus occurs if the clot moves. An embolus causes an embolism when it stops and blocks off a smaller blood vessel. This causes a heart attack if the artery is a coronary artery or a stroke if it is an artery in the brain.
P. septum - separates left and right ventricles
Q. posterior vena cava - drains blood from lower body into left ventricle
R. anterior vena cava - drains blood from upper body into left ventricle
S. pulmonary trunk - unoxygenated blood from r. ventricle to lungs, branches into l. and r. pulmonary arteries
T. aorta - oxygenated blood from l. ventricle to body
U. right atrium - pumps blood into right ventricle
V. left atrium - pumps blood into left ventricle
W. left ventricle - pumps blood into aorta to systemic system
X. a semi lunar valve, one at the exit of ech ventricle, prevents backflow of blood into ventricle
Y. right ventricle - pumps unoxygenated blood into pulmonary artery to lungs
Z. an atrioventricular valve - one between each atrium and ventricle, prevents backflow of blood from ventricles into atria.
Not shown on diagram
chordae tendineae - fibres running from the atrioventricular valves to the bottom of the ventricles, prevent the atrioventricular valves from collapsing backwards
coronory arteries and veins - on the outside of the heart. Arteries branch off the aorta and supply the heart muscle with oxygenated blood. Veins return to vena cava .
K.2 NODES
The left and right side beat in syncronization (together).
- both atrium contract, then both ventricles.
- the heartbeat is independent, it can beat without nervous stimulation.
There are two nodes (comb. of muscle and nervous tissue)
i) S - A (sino atricular) node on upper right atrium .
- initiates heratbeat
- sends out signal every 0.85 seconds
- causes atria to contract
ii) A - V (atrio ventricular) node on lower right atrium .
- when signal from S-A node reaches here, the A - V node causes the ventricles to contract.
- ventricles contract from the bottom, upwards.
Perkinje fibres transfer the impulses to the bottom of the ventricle and spread them upwards over the surface of the ventricles.
K3. REGULATION OF HEARTBEAT - NERVES
Autonomic control
a) Heartbeat
- The heartbeat is also under nervous control.
- The heartbeat centre is in the brain (medulla oblongata) and it controls the pulse rate via the autonomic nervous system.
- can speed up the heart (via sympathetic nerves) or slow it down (via parasympathetic nerves).
- many factors (O2, blood pressure, emergency etc.) can determine which system is activated.
K5. & K6. BLOOD PRESSURE
- Systole - contraction of the ventricles
- pumping action
- highest blood pressure / normal = 120 (mm of Hg)
- Diastole - relaxation of the ventricles
- chambers refilling
- lowest blood pressure / normal = 80
Blood pressure is given as a ratio of systole over diastole
- 120/80 is normal, in the brachial artery of the arm.
- varies considerably throughout the body.
K4. BLOOD PRESSURE - HYPER AND HYPOTENSION
Hypertension is when blood pressure is higher than expected.
- usually an indication of cardiovascular disease.
- eg. 150/100
Hypotension is when blood pressure is lower than expected.
-eg. 100/60
Pressure
- a number of factors contribute
- sympathetic nerves increase blood pressure
- inc. Na+ by kidneys or diet increase blood pressure
- arterioles constricting increase blood pressure
- atherosclerosis increases blood pressure
Atherosclerosis - accumulation of soft masses of fatty material, esp. cholesterol, beneath inner linings of arteries. These protrude and interfere with blood flow and increase blood pressure. The presence of hard plaque on artery walls can cause blood to form clots. If the clots stay in place they will block blood flow in the artery (thrombus). An embolus occurs if the clot moves. An embolus causes an embolism when it stops and blocks off a smaller blood vessel. This causes a heart attack if the artery is a coronary artery or a stroke if it is an artery in the brain.