Heart Flashcards
Describe the first part of the cardiac control system
Electrical signal in the sinoatrial node, the electrical impulse spreads through the walls of the atria leading to atrial systole
Describe the 2nd part of the cardiac conduction system
Signal then transmitted to the atrioventricular node, which delays the transmission of the impulse by 0.1 seconds to allow atria to contract fully, pushing blood into ventricles
Describe the 3rd part of the cardiac conduction system
The impulse is then transmitted to the bundle of his followed by the purkinje fibres, which conduct the impulse to the ventricles causing ventricular systole (blood forced out)
Describe the cardiac cycle
Impulse from SA node —> atrial systole —> blood forced into ventricles (ventricular diastole) - av valves open, semi-lunar valves shut —> atrial diastole (fill with blood) —> impulse spreads to ventricles +they contract (ventricular systole) , av valves shut, semi-lunar valves open —> blood forced into aorta and pulmonary artery —> ventricles relax and cycle begins again
Difference between ventricular systole and ventricular diastole
Systole - contraction of ventricles, forcing blood out of ventricles into aorta + p.a
Diastole - relaxation of ventricles, fill with blood from atria
2 factors that determine an individuals stroke vol.
Starlings law - increased venous return —> greater diastolic filling of heart —> stretches cardiac muscles —> more forceful contraction —> increased ejection fraction
Ejection fraction - percentage of blood in heart that leaves the heart per beat - increased ejection fraction increases stroke vol
Relationship between stroke vol cardiac output and hr
Q (l/m3) = sv x hr
What do chemoreceptor detect and what occurs when they do
Detect change in blood ph levels (decrease due to increase in co2 and decrease of o2) inform cardiac control centre which stimulate the sympathetic nervous system leading to an increase in hr due to san being stimulates
What do mechanoreceptors detect and what occurs when they do
Detect muscle contractions, inform cardiac control centre, stimulate sympathetic nervous system, stimulate san, increase in hr
What do proprioreceptors dectect and what happens when they do
Detect joint movement, informs cardiac control centre, stimulates sympathetic nervous system, stimulates san, increases hr
What do baroreceptors detect and what occurs when they do
Detect decrease in blood pressure when exercise stops or an increase, inform cardiac control centre which stimulate the parasympathetic nervous system which stimulates the San to reduce number of impulses, reducing hr
What are the three other factors that influence the cardiac control centre
- Venous return - (due to skeletal muscle pump) increase leads to an increase in hr
- Adrenaline- stimulates San increases hr
- Temp. - increase leads to an increase in hr
What is the a in the hr time graph
Why does it happen
A = anticipatory rise due to hormonal action of adrenaline which causes San to increase hr
Body is anticipating + preparing for exercise
What is the b in the hr time graph
Why does it happen
B = sharp rise in hr due to mainly aerobic work
Keep up with increased o2 demand of muscles + removes co2 quicker
What is the c in the hr time graph
Why does it happen
C = hr continues to rise due to maximal workloads stressing the anaerobic systems
Sympathetic nervous system overrides parasympathetic system
What is the d in the hr time graph
Why does it happen
D = steady state as the athlete is able to meet with the o2 demand with the o2 supply
O2 requirements are being met
What is the e in the hr time graph
Why does it happen
E = rapid decline in hr as soon as the exercise stops
Muscles/body don’t require as much o2
What is the f in the hr time graph
Why does it happen
F = slower recovery as body systems return to resting levels. Hr needs to remain elevated to rid the body of waste products (lactic acid)
O2 requirements are almost normal again
How does the body facilitate a (anticipatory rise)
Release of adrenaline (from sympathetic nerves) increase hr
How does the body facilitate b (sharp rise in hr)
Chemoreceptors detect an increase in co2
Baroreceptors detect an increase in arterial pressure
Proprioreceptors detect muscle movements
How does the body facilitate c (hr continues to rise)
The San release impulses as fast as possible to maximise cardiac output + amount of o2 delivered
How does the body facilitate d (steady state)
Receptors signal to ccc that hr isn’t increasing (parasympathetic starts to override sympathetic)
How does the body facilitate e (rapid decline in hr)
Receptors stop signals to ccc so parasympathetic system overrides sympathetic system and hr falls
How does the body facilitate f (slower recovery)
Co2 levels are normal, blood pressure is normal + parasympathetic system is in control
