What are the two stages of the cardiac cycle?
Diastole - where the heart relaxes and fills with blood
Systole - This is the process where the heart contracts and blood is ejected from the heart
What is the difference between atrial systole and ventricular systole ?
Atrial - Atria contracts to force blood into the ventricles
Ventricular - Ventricles contract which forces blood out of the heart and into the aorta and pulmonary artery then to body and lungs
What does myogenjc mean?
The ability for the heart muscle to generate its own impulse
What are the started of the cardiac conduction ?
1- impulse starts at SA node - pacemaker of heart. Impulse cause the atria to contacts - wave of excitation
2 - impulses stimulate atrial systole
3 - impulse travels down into AV node. Short delay - 0.1s in the signal at AV node - atria to fully empty and ventricles to fill with blood
4 - impulse then travels through the bundle of his
5 - pulse travels down the left and right branches through the Purkinje fibers in the walls of the ventricles
6 - ventricle systole occurs
What is the sympathetic nervous system and parasympathetic nervous system controlled by?
These two are coordinated by the cardiac control centre located in the medulla oblongata.
Sympathetic nervous system:
- During exercise it increases heart rate and cardiac output by sending impulses down the sympathetic nerve and releases adrenaline and norepinephrine into the heart.
- impulses are sent to stimulate SAN more frequently and there is a decrease in PN impulses so heart rate increases
Parasympathetic nervous system :
- decreases heart rate and cardiac output, through the vagus nerves by releasing acetylcholine onto the heart
What are the receptors in the cardiac control centre?
The CCC is stimulated by - baroreceptors, chemoreceptors, prioreceptors
-they detects some form of change and send imoulses to the CCC in the medulla oblongata which sends an impulse to the SA node either via the SNS or the PNS
Chemoreceptors
- detect chemical changes within the blood - eg an increase the in blood CO2 levels or a decrease in OH levels and more blood acidity,
- they relay information to the Medulla Oblongata which then uses the appropriate system, be it the SNS or PNS to regulate the heart rate and contractile force
- located in the carotid arteries and aortic arch writhing the heart
What are baroreceptors?
- detects an increase or decreases in blood pressure and signal is sent to the medulla oblongata to regulate HR
- decrease in BP - increase in HR vice versa
- at start of exercise - baroreceptor set point increase which is inportanr as the body doesn’t want HR to slow - negatively effect performance less o2 to WM
Proprioreceptors
- sensory nerve endings in the muscles, tendons and joints that detect changes in muscle movement and contractions
- at start if ex - detect increase in muscle movement. Send impulse to the medulla oblongata which then send impulse through the SNS to the SAN to increase HR
What is adrenaline
- a stress hormone that is released by the SN and cardiac nerve during exercise
- also known as fight or flight hormone. It is secreted by adrenal glas and makes the heart beat faster and stronger
What is the anticipatory rise?
- Prior to exercise -HR increase due to the release of adrenaline.
- helps prepare for exercise - causes an increase in O2 supply to muscles
- adrenaline - increases speed and quality of the impulses sent via the sympathetic system to the SAN
- results in increased CO as more blood pumped to WM so can recurve more P2 for energy they need
Intrinsic control:
Venous return - caused changes in cardiac performance. If more blood is returning allows more blood to eject per contraction
Thermo receptors - detects changes in blood, joint and muscle temperature which indicates exercise.
Neural control
- baroreceptors, proprioreceptors, chemoreceptors
Hormonal control
Adrenaline is released due to the stress and increased hr and contractile strength
Noradrenaline increases the transmission speed of nerve impulses
Acetylcholine decreases the transmission speed of nerve impulses
Redistribution of blood - typical question
- receptors send impulses to vasomotor centre in the medulla oblongata.
- increased sympathetic nervous impulses to cause both vasoconstriction to the blood vessels and contracting of the pre capillary sphincters surrounding the non essentials organs
- medulla decreases sympathetic nervous impulses to cause both vasodilation to the blood vessels and opening of precapillary sphincters surrounding the WM
Cardiac hypertrophy
- when the heart becomes bigger and stronger due to the thickening of the muscular wall
Bradycardia
A resting heart rate below 60 beats per min
Sub maximal exercise
- see a plateau in cardiac output when a steady state is reached as the CV system is able to supply the WM with adequate oxygen
- causes significant increase in venous return due to vas shunt mechanisms. Result - chambers if heart becomes bigger stretched increasing diastolic fill
Maximal exercise
- will result in a greater cardiac output than sub and this will peak and then rapidly decline as max can’t be sustained
- causes muscles to contract fully, which press on nearby blood vessels, restricting the blood flow through them. Sharp increase in BP. Cardiac muscle become stronger - adapt to eject blood against higher levels of resistance
