heart test no Flashcards
describe how a heartbeat is initiated and coordinated
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
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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
What is the role of baroreceptors
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
What is the pulmonary circulation
deoxygenated blood is pumped from the right ventricle of heart to the lungs, where it is oxygenated and then returns to the left atrium
What is the difference between the sympathetic and parasympathetic nervous system?
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)
What is the systemic circulation?
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
what is the name of the blood vessel leaving the left atrium?
Aorta
What blood vessel supplies the heart?
Coronary arteries
Name of the blood vessels associated with the kidneys?
Renal
What part of the heart is responsible for controlling HR
Changes to heart rate controlled by cardiovascular centre in the medulla oblongata (region of brain)
What happens in ventricular systole?
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
How does the heart beat control the cardiac cycle?
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
What happens in diastole
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
What motor neurones are involved in the sympathetic and parasympathetic nervous system?
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
What happens in atrial systole?
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
what is the blood vessel supplying blood to the right atrium
vena cava
Outline what happens with a high co2 levels in the blood
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.
What is the blood vessel supplying the lungs from the right ventricle?
Pulmonary artery
What is the blood vessel supplying the left atrium?
Pulmonary vein
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.
- (Plasma) proteins remain;
- (Creates) water potential gradient
OR
Reduces water potential (of blood); - Water moves (to blood) by osmosis;
- Returns (to
blood) by lymphatic system;
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.
(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;
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.
- 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; - red blood cells in contact with wall / pass singly, gives short diffusion distance / more time for diffusion;
Explain how tissue fluid is formed and how it may be returned to the circulatory system.
- (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;
