Extrinsic regulation of heart pumping. Control of the heart by the sympathetic and parasympathetic nerves. Effect of some humoral factors on heart function. Ventricular function curves Flashcards
SYMPATHETIC NERVOUS SYSTEM - activation
sympathetic nerves release noradrenaline located on cardiac b adrenergic receptors located on SA node, atria, ventricles
SYMPATHETIC NERVOUS SYSTEM
function 1
positive chronotropy effect = increased HR
- noradrenaline binds to SA node
- SA node starts AP firing causing atria to contract fully + fill ventricles with blood
SYMPATHETIC NERVOUS SYSTEM
function 2
positive ionotropy effect = increase force of contraction
noradrenaline causes voltage gated calcium ion channels to open for ca2+ influx
SYMPATHETIC NERVOUS SYSTEM
function 3
positive dromotropy effect = increased speed of electrical conductance
noradrenaline stimulates AV node to make rate of AP firing faster as it travels through rhythmic excitation of heart
PARASYMPATHETIC NERVOUS SYSTEM - activation
vagus nerve released Ach at M receptors
- located on SA node, AV node, atria
PARASYMPATHETIC NERVOUS SYSTEM
function 1
negative chronotropy effect = decrease heart rate
Ach decreases depolarisation on SA node = less AP firing
PARASYMPATHETIC NERVOUS SYSTEM
function 2
negative ionotropy effect = decrease force of contraction
Ach reduces Ca2+ influx = less contraction
PARASYMPATHETIC NERVOUS SYSTEM
function 3
negative dromotropy effect = decrease speed of electrical conductance through heart
Ach decreases AP firing through AV node to purkyne fibres
NEURAL - OTHER 1
baroreceptor reflex:
- found in carotid sinus/ arcus aorta
detected by baroreceptors which detect increase in tension/ stretch/ pressure
high BP = less signals sent to medulla oblongata = vasodilation
low BP = more signals sent to medulla oblongata = vasoconstriction
NEURAL - OTHER 2
PERIPHERAL CHEMORECEPTOR REFLEX
- found in carotid body/ aortic body
- detect low oxygen (hypoxia) + high co2 (hypercapnia) + low pH (acidosis)
NEURAL - OTHER 3
CENTAL CHEMORECEPTOR REFLEX
- detect carbon dioxide
- detect pH of CSF
NEURAL - OTHER 4
BAINBRIDGE REFLEX
1 - more bloodflow to right atria
2 - stretch receptors activate
3 - signals sent to medulla oblongata
4 - higher HR
Endocrine System Regulation 1
adrenaline/ noradrenaline
released from adrenal medulla during stress response
amplifies SNS functions
Endocrine System Regulation - 2
RAAS
En3ocrine System Regulation - 4
ANP
- released from atria
increase h2o/Na+ EXCRETION in kidneys
vasodilation
inhibits RAAS
= reduce volume/ pressure
