cardiovascular control mechanisms Flashcards
sympathetic nervous system: recall the organisation and role of the sympathetic nervous system, and recall neurotransmitters acting within the sympathetic nervous system including receptors and effects
branches of autonomic nervous system
parasympathetic and sympathetic
where does the parasympathetic arise from
cranial and sacral part of spinal cord
where does the sympathetic arise from
thoracic and lumbar vertebra
parasympathetic: pre-ganglion: length, neurotransmitter and receptor
pre-ganglionic neurone long, acetylcholine, nicotinic receptor
parasympathetic: post-ganglion: length, neurotransmitter and receptor
post-ganglionic neurone short, acetylcholine, muscarinic receptor
sympathetic: pre-ganglion: length, neurotransmitter and receptor
pre-ganglionic neurone short, sympathetic chain, acetylcholine and nicotitic receptors
sympathetic: post-ganglion: length, neurotransmitter and receptor
post-ganglionic neurone long, noradrenaline, muscarinic receptor
why is response from sympathetic innervation to blood vessels difficult to predict
different receptors so difficult to predict as it is variable
what nervous system has no innervation to blood vessels
parasympathetic
where does sympathetic innervation occur
innervates heart and all vessels except capillaries, precapillary sphincters and some metarterioles
sympathetic innervation: where is heavily innervated
kidneys, gut, spleen, skin
sympathetic innervation: where is poorly innervated
skeletal muscle, brain
sympathetic innervation: where does noradrenaline preferentially bind to on vessels and what does it cause
a1 adrenoreceptors to cause smooth muscle contraction and vasoconstriction
vasomoter centre: where is it located
bilaterally in reticular substance of medulla and lower third of pons
vasomoter centre: what is it composed of
vasoconstrictor (pressor) area, vasodilator (depressor) area and cardioregulatory inhibitory area
vasomoter centre: what do high centres of brain exert; specifically lateral and medial
e.g. hypothalamus; exert powerful excitatory or inhibitory effects on vasomotor centre (e.g. preparing for exercise); lateral control heart activity influencing HR and contractility, medial control traffic down vagus nerve to change HR
nervous control of vessel diameter: what neurotransmitter allows for SNS post-ganglionic innervation
noradrenaline
nervous control of vessel diameter: define tonic activity
frequency of firing of action potential
nervous control of vessel diameter: why is there baseline constriction
to allow both vasoconstriction and vasodilation
nervous control of vessel diameter: effect of more tonic activity
vasoconstriction
nervous control of vessel diameter: effect of less tonic activity
vasodilation
cardiac innervation: parasympathetic effect on heart rate
decrease heart rate (decrease speed of depolarisation towards threshold of SAN)
cardiac innervation: sympathetic effect on heart rate
increase heart rate (increase speed of depolarisation towards threshold of SAN)
cardiac innervation: sympathetic effect on circulating plasma adrenaline
increase circulating plasma adrenaline
what happens if both parasympathetic and sympathetic neurones are cut and significance
slight increase in heart rate, so always some parasympathetic nerve activity on heart at rest
how does sympathetic nervous system influence force of contraction (pathway) when binding to heart
noradrenaline binds to B1 receptor → increases cAMP and PKA → L-type Ca2+ channels open → more Ca2+ influx → bind to SR Ca2+ release channel → more Ca2+ act in muscle contraction → greater force of contraction → increases Ca2+ uptake into IC stores
controlling stroke volume: extrinsic (hormonal and neuronal) methods
increase SNS efferents to heart, increase plasma adrenaline
controlling stroke volume: intrinsic methods
increase atrial pressure, increase venous return (Starling’s law of heart)
what increases both stroke volume and heart rate to increase cardiac output
increasing plasma adrenaline and SNS efferents to heart
what is reciprocal innervation
where increased afferent input from increased baroreceptor activity stimulates parasympathetic nerves to heart
effect of reciprocal innervation
increases parasympathetic nerve activity, decreases sympathetic nerve activity, causing vasodilation and decrease in heart rate
in reciprocal innervation, how is sympathetic nerve activity decreased
inhibitory neurone inhibits tonic activity
4 ways to increase venous return and atrial pressure
increase blood volume, SNS activation of veins (vasoconstriction), increase skeletal muscle pump, increase respiratory movements
