Homeostasis Of Blood Pressure Flashcards
Describe the feedback loop for a person with hypertension, in terms of blood pressure.
Stimulus - increased blood pressure and cardiac output.
Receptor - baroreceptors in aortic and carotid bodies.
Modulator - cardiac centre in medulla via parasympathetic fibres.
Effector - SA and AV nodes.
Response - decreased heart rate/stroke volume due too reduced firing rate of SA and AV nodes.
Describe the feedback loop for a person feeling faint in terms of their blood pressure?
Stimulus - decreased blood pressure and cardiac output.
Receptor - baroreceptors in aortic and carotid bodies.
Modulator - cardiovascular centre in medulla via sympathetic fibres.
Effector - hearts sa and av nodes and blood vessel walls.
Response - increased heart rate/stroke volume due to increased firing rate of sa and av nodes. Vasoconstriction and increased venous return.
What is heart rate?
Number of times the heart beats per minute.
What is stroke volume?
Blood forced from heart with each contraction.
What is blood pressure?
Force with which blood presses on the walls of blood vessels.
What factors affect stroke volume?
Force of contraction of ventricles.
Length of diastole - the longer the diastole, the ore time available for ventricles to fill.
Venous return- contraction of muscle fibres is more forceful wen fibres are stretched.
What factors affect heart rate?
Age - fast at birth, slows as we age.
Sex - males slower than females.
Emotional state - fear and stress increase heart rate.
What are sinoatrial and atrioventricular nodes?
Bundles of specialised cells capable of initiating nerve impulses to stimulate muscle contraction in the heart.
How do sympathetic fibres increase heart rate/stroke volume?
Release noradrenaline.
How do parasympathetic fibres decrease heart rate/stroke volume?
Releases acetylcholine.
What sort of changes to blood flow occur during exercise?
Contracting muscles require extra blood.
Blood is redirected from organs to muscles. Eg: blood vessels in alimentary canal constrict and those in muscles dilate.
CO2 and lactic acid act as vasodilator = increased blood flow.
During exercise, blood flow to the muscle cells increases ensuring sufficient nutrients and oxygen are supplied to meet demands and wastes are removed. What two aspects of the heart cause this increased blood flow?
Heart rate and stroke volume.
What parts of the nervous and endocrine system are involved in increased blood flow?
Autonomic (sympathetic) and nor/adrenaline form adrenal glands.
