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Question 1

describe how a heartbeat is initiated and coordinated

Answer 1

The SAN produces an electrical impulses similar to those produced by nerve cells
This travels through the cardiac muscle, causing the atria to contract
The wave of excitation is delayed at the non-conductive tissue
The only route through this non- conductive tissue via the AVN
The AVN passes the wave at the base of the ventricles along the bundle of HIs
The wave then passes to purkinje fibres which branch up the outer walls of the ventricles
Which causes the ventricles to contract from the base upwards

Question 2

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Answer 2

1 SAN sends waves of electrical activity.

2 Causes atrial to contract.

3 Non conducting tissue prevents immediate contraction of ventricles.

4 AVN delays impulse whilst blood leaves atria and ventricles fill

5 AVN sends waves of electrical activity down the bundle of HIS

6 Causing ventricles to contract from base up

Question 3

What is the role of baroreceptors

Answer 3

Baroreceptors (blood pressure) in walls of aorta and carotid artery.
If pressure increases - increase in action potentials to decelerator region of medulla oblongata- results in more parasympathetic activity, decreased heart rate and cardiac output.
If pressure decreases - increase in action potentials to accelerator region of medulla oblongata - results In more sympathetic activity - increased heart rate and cardiac output

Question 4

What is the pulmonary circulation

Answer 4

deoxygenated blood is pumped from the right ventricle of heart to the lungs, where it is oxygenated and then returns to the left atrium

Question 5

What is the difference between the sympathetic and parasympathetic nervous system?

Answer 5

Autonomic nervous system controls involuntary responses in the body sympathetic- increases activity e.g. heart rate (fight and flight responses)
Parasympathetic - reduces activity, e.g. Heart rate (rest, refuel and reproduce responses)

Question 6

What is the systemic circulation?

Answer 6

Deoxygenated blood is pumped from the right ventricle of heart to the lungs, where it is oxygenated and then returns to the left atrium - the pulmonary circulation

Question 7

what is the name of the blood vessel leaving the left atrium?

Answer 7

Aorta

Question 8

What blood vessel supplies the heart?

Answer 8

Coronary arteries

Question 9

Name of the blood vessels associated with the kidneys?

Answer 9

Renal

Question 10

What part of the heart is responsible for controlling HR

Answer 10

Changes to heart rate controlled by cardiovascular centre in the medulla oblongata (region of brain)

Question 11

What happens in ventricular systole?

Answer 11

Higher pressure in ventricles than atria or arteries
Blood moves into the arteries
Increase arterial volume, decrease ventricular volume, ventricle walls contract
Atrioventricular values close, semi- lunar valves open

Question 12

How does the heart beat control the cardiac cycle?

Answer 12

SAN spontaneously depolarises, producing wave of excitation across atria, causing atria contraction
Non- conductive tissue in atrio - ventricular septum prevents wave of excitation passing directly to ventricles
AVN causes pause in conduction, allowing time for atria to empty.
Wave of excitation passes from AVN down bundle of HIs and out into purkyne fibres.
Causing contraction of ventricles from apex upwards

Question 13

What happens in diastole

Answer 13

higher pressure in atria and arteries than ventricles.
Blood flows away in the arteries
Blood flows into the atria (venous return) and then into ventricles
Increase atrial and ventricular volumes decrease arterial volume
Semi- lunar valves close, AV valves open

Question 14

What motor neurones are involved in the sympathetic and parasympathetic nervous system?

Answer 14

Increase in action potentials along accerlator nerve (sympathetic) causes increase in rate of SAN depolarisation
Increase in action potentials along decelerator nerve (parasympathetic causes decrease in rate of SAN depolarisation

Question 15

What happens in atrial systole?

Answer 15

higher pressure in atria than ventricles
blood moves into the ventricles
Increase ventricular volume, decreases atrial volume,
atrial walls contract
AV values open, semi lunar close

Question 16

what is the blood vessel supplying blood to the right atrium

Answer 16

vena cava

Question 17

Outline what happens with a high co2 levels in the blood

Answer 17

Chemoreceptos in walls of aorta and carotid artery are sensitive to changes in pH, caused by changes in CO2 conc. e.g. during exercise..
Fall in pH, due to increased co2 conc
Increase in action potentials along sensory neurone to medulla oblongata
Increase in action potential along accelerator nerve
Increase cardiac output and excretion of CO2.
As PH increases, the frequency of action potentials along sensory neurone decreases.

Question 18

What is the blood vessel supplying the lungs from the right ventricle?

Answer 18

Pulmonary artery

Question 19

What is the blood vessel supplying the left atrium?

Answer 19

Pulmonary vein

Question 20

Tissue fluid is formed from blood at the arteriole end of a capillary bed.
Explain how water from tissue fluid is returned to the circulatory system.

Answer 20

1. (Plasma) proteins remain;
2. (Creates) water potential gradient
   OR
   Reduces water potential (of blood);
3. Water moves (to blood) by osmosis;
4. Returns (to
   blood) by lymphatic system;

Question 21

Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

Answer 21

(b) 1. Atrium has higher pressure than ventricle (due to filling / contraction) causing atrioventricular valves to open;
Start anywhere in sequence, but events must be in the correct order.
1. Accept bicuspid, reject tricuspid
1. Allow: blood passes through the valve = valve open / blood stopped from passing through the valve = valve closed
2. Ventricle has higher pressure than atrium (due to filling / contraction) causing atrioventricular valves to close;
3. Ventricle has higher pressure than aorta causing semilunar valve to open;
Points 1, 2 and 3 must be comparative: eg higher 3. Allow aortic valve
4. Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close;
4. Allow aortic valve
5. (Muscle / atrial / ventricular) contraction causes increase in pressure;

Question 22

a) Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.

Answer 22

1. permeable capillary wall / membrane;
   2. single cell thick / thin walls, reduces diffusion distance;
   3. flattened (endothelial) cells, reduces diffusion distance;
   4. fenestrations, allows large molecules through;
   5. small diameter / narrow, gives a large surface area to volume / short diffusion distance;
   6. narrow lumen, reduces flow rate giving more time for diffusion;
2. red blood cells in contact with wall / pass singly, gives short diffusion distance / more time for diffusion;

Question 23

Explain how tissue fluid is formed and how it may be returned to the circulatory system.

Answer 23

1. (hydrostatic) pressure of blood high at arterial end;
   2. fluid / water / soluble molecules pass out (reject plasma);
   3. proteins / large molecules remain;
   4. this lowers the water potential / water potential becomes more negative;
   5. water moves back into venous end of capillary (reject tissue fluid) by osmosis / diffusion;
   6. lymph system collects any excess tissue fluid which returns to blood / circulatory system / link with vena cava / returns tissue fluid to vein;