Physiology - Intro to the heart Flashcards
What is compliance?
Measure of expandibility of a vessel
Describe the compliance of a vein
More compliant than arteries => act as a reservoir
Have much lower venous pressure
What is Darcy’s law?
Arterial pressure = Cardiac output * total peripheral resistance
What are the two phases of the cardiac cycle?
Diastole = chambers are relaxed and filling
Systole = ventricles are contracting and ejecting
Which valves are open and close during diastole and why?
Tricuspid and mitral valves open
Pulmonary and aortic valves are close
- Atrial pressure > ventricular pressure
Which valves are open and closed during systole and why?
Tricuspid and mitral = closed
Pulmonary and aortic = open
- Ventriculuar pressure > atrial pressure
What is the purpose of valves?
To ensure unidirectional flow
What is the end-diastolic volume?
The volume filling a ventricle before contraction
What is stroke volume?
The blood volume ejected by a ventricle on contraction
What is end-systolic volume?
Volume of blood remaining in ventricle after systole
What is the general concept of the baroreceptor reflex?
Short term response occuring when:
Increased stretch felt by baroreceptors => increased impulse
Where are the four main baroreceptors located and which nerve innervates them?
Vagus nerve
- Atrial stretch receptors
- Left ventricle/coronary artery
- Arch of aorta
Glossopharyngeal
- Carotid sinus
Describe the pathway of the baroceptor reflex?
Baroceptors -> medulla -> ANS -> SA node
Describe the effect of the baroreceptors in response to increased and decreased pressures?
Increased pressure => increased impulses => increased medullary stimulation => increased parasymp activity through vagus nerve => reduced HR through action on SAN => vasodilation
Decreased pressure => decreased impulses => decreased medullary stimulation => increased sympathetic activity through sympathetic chain => increased HR through SAN => increased contraction + vasoconstriction
What is the long term control of blood pressure?
Osmoregulation
Pressure natriuresis
Renin-Angiotensin-Aldosterone system
What are the three layers of the wall in larger blood vessels?
Tunica intima
Tunica media
Tunica adventitia
Describe the tunica intima
A layer of flat endothelial cells overlying thin connective tissue
Endothelial cells in direct contact with blood
Seperated from the tunica media by the internal elastic lamina
Describe the tunica media
A circular layer of smooth muscle containing elastin and collagen
Innervated by sympathetic nerve fibres
Provides mechanical strength to vessel
Describe the tunica adventitia
Loosely formed layer of elastin and collagen fibres
Anchors blood vessel in place
Seperated from tunica media by the external elastic lamina
What are the different types of blood vessels?
Elastic (Windkessel) arteries
- aorta, pulm artery, main branches of these
Muscular arteries
- large/medium arteries with high prop. of smooth muscle
Arterioles
- resistance vessels
Capillaries
- exchange vessels
Veins
- reservoir/capacitance vessels
