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CVR Week 1 > Autonomic Control in the Cardiovascular system, > Flashcards

Autonomic Control in the Cardiovascular system, Flashcards

1
Q

what is the autonomic nervous system?

A

responsible for controlling many physiological functions. induces the force of contraction of the heart and its heart rate. it controls the peripheral resistance of blood vessels.

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2
Q

what is the parasympathetic division?

A

-input into the heart is via the vagus nerve
-forms synapses with postganglionic cells in SAN and AVN
-when stimulated Ach binds to M2 receptors which act to decrease the slope of the pacemaker potential
-decrease in heart rare

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3
Q

how does the parasympathetic NS affect heart rate?

A

decreases HR

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4
Q

what is the sympathetic input into the heart?

A

post ganglionic fibres from the sympathetic trunk which innervate the SAN and AVN.
-release noradrenaline, acts on B1 adrenoreceptors to increase the slope of pacemaker potential
-increases HR and force of contraction

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5
Q

what effect does the sympathetic NS have on the heart?

A

increases heart rate
increases the force of contraction

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6
Q

what is chronotropic effect?

A

changes in heart rate

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7
Q

what is an intropic effect?

A

force of contraction

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8
Q

which branch of the ANS dominates at rest?

A

The parasympathetic input on the SAN dominates at rest, giving a normal resting heart rate of around 60bpm. A reduction in parasympathetic outflow results in an initial increase in heart rate, reaching over 100bmp. This is further brought about by an increase in sympathetic outflow.

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9
Q

how does the sympathetic NS work?

A

Capillaries receive no innervation. Activation of vascular sympathetic nerves causes contraction of the vascular smooth muscle and vasoconstriction of arteries and veins mediated by alpha-adrenoceptors.

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10
Q

where are the parasympathetic fibres found?

A

associated with blood vessels in certain organs such as salivary glands, GI glands and in genital erectile tissue

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11
Q

where are the sympathetic NS nerves found?

A

along arteries and nerves and are found in the adventitia (outer wall of blood vessel).

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12
Q

what Are varicosities?

A

small enlargements along the nerve fibers, are the site of neurotransmitter (norepinephrine) release.

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13
Q

what happens when ACh is released from parasympathetic nerves?

A

binds to muscarinic ACh receptors, has a direct vasodilatory action (coupled to nitric oxide formation and guanylyl cyclase activation). ACh release can stimulate the release of kallikrein from glandular tissue that acts upon kininogen to form kinins (e.g., bradykinin). Kinins cause increased capillary permeability and venous constriction, along with arterial vasodilation in specific organs.

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14
Q

what are baroreceptors?

A

mechanoreceptors located in both the carotid sinus and aortic arch. sensitive to changes in stretch and tension in the arterial wall.
they can detect changes in the arterial pressure and communicate this to the medulla oblongata in the brain stem

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15
Q

what are the medullary centres in the Brain responsible for?

A

overall output of the autonomic NS and use the information did back from the baroreceptors to coordinate a response

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16
Q

what happens when an increase in arterial pressure is detected by baroreceptors?

A

the parasympathetic pathway Is activated to reduce HR. this along with increasing vasodilation of vessels acts to reduce arterial pressure

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17
Q

what happens when a decrease in the arterial pressure is detected by baroreceptors?

A

the sympathetic pathway is activated to increase the heart rate and the contractility of the heart. This, along with increasing vasoconstriction of vessels, acts to increase the arterial pressure.

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18
Q

which 3 neurotransmitters would you expect to find in the smooth muscle of a blood vessel (the sympathetic triad)

A

noradrenaline
ATP
neuropeptide-Y

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19
Q

what does noradrenaline do in smooth muscle of a blood vessel?

A

stimulate a-1 adrenoceptors

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20
Q

what does ATP do in smooth muscle of a blood vessel?

A

stimulate P2X receptor

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21
Q

what does Neuropeptide-Y do in smooth muscle of a blood vessel?

A

stimulate Y receptor

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22
Q

why do we need 3 different neurotransmitters acting on 3 different receptors?

A
  • Fine control of blood vessel so fine control of blood pressure
  • P2X activate Sodium channels to initiate fast response
  • a1 activate G-protein coupled receptors
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23
Q

what is the onlyneurotransmitter used in the motor division of the somatic nervous system and the principal neurotransmitter at autonomic ganglia?

A

ACh

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24
Q

what are some roles of ACh?

A

-plays a role in synaptic plasticity, including learning and short term memory
-may bind to either muscarinic or nicotinic receptors

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25
Q

what is the cholinergic system?

A

-made up of neurons that release and respond to ACh
-causes anti-excitatory effects

26
Q

whee is Ach synthesised?

A

cholinergic neurons (such as those in the nucleus basalis of Meynert) from choline and acetyl-CoA using an enzyme called choline acetyltransferase.

27
Q

what is the role of choline acetyltransferase?

A

to join Acetyl-CoA to choline, resulting in the formation of the neurotransmitter acetylcholine.

28
Q

what is choline acetyltransferase?

A

Abbreviated as ChAT, this is an enzyme that is synthesized within the body of a neuron. It is then transferred to the nerve terminal via axoplasmic flow.

29
Q

what are autonomic ganglia?

A

Clusters of neuronal cell bodies and their dendrites that are a junction between the autonomic nerves originating from the central nervous system and the autonomic nerves innervating their target organs in the periphery.

30
Q

what are nicotinic receptors?

A

Also called nAChRs, these are cholinergic receptors that form ligand-gated ion channels

31
Q

where are nicotinic receptors found?

A

plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction

32
Q

what are the groups of adrenergic receptors?

A

consist of two main groups, α and β, multiple subgroups (α1, α2, β1, β2, β3), and several subtypes of the α2 subgroup (α2A, α2B, α2C).

33
Q

what adrenergic groups does epinephrine bind to?

A

both α and β adrenergic receptors to cause vasoconstriction and vasodilation.

34
Q

what happens when the a1 receptor is activated?

A

triggers smooth muscle contraction in blood vessels in the skin, gastrointestinal tract, kidney, and brain, among other areas.

35
Q

what happens when the a2 receptor is activated?

A

triggers inhibition of insulin and the induction of glucagon release in the pancreas, contraction of GI tract sphincters, and increased thrombocyte aggregation.

36
Q

what are adrenoreceptors?

A

These are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline).

37
Q

what happens when catecholamine binds to adrenoreceptors?

A

stimulation of the sympathetic nervous system

38
Q

what are G protein coupled receptors?

A

These comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. Any adrenergic effects on cells are generally mediated by G protein-coupled receptors.

39
Q

what is an adrenergic receptor?

A

Any of several sites in the surface membranes of cells innervated by adrenergic neurons

40
Q

how do acetylcholine receptor agonist and antagonists work?

A

-direct effect on the receptors
-indirectly affecting the enzyme acetylcholinesterase
-may target either the nicotinic or muscarinic receptors for ACh

41
Q

what is atropine?

A

an antagonist for muscarinic ACh receptors, Lowers the parasympathetic activity of muscles and glands in the parasympathetic nervous system.

42
Q

what is neostigmine?

A

indirect ACh receptor agonist that inhibits acetylcholinesterase, preventing the breakdown of acetylcholine.

43
Q

when is neostigmine used?

A

treatment of myasthenia gravis and to reverse the effects of neuromuscular blockers used for anesthesia.

44
Q

what is pehylephrine?

A

marketed as a substitute for Sudafed for decongestant purposes, is an α1- adrenergic receptor agonist.

45
Q

what are beta blockers?

A

block the action of epinephrine and norepinephrine on β-adrenergic receptors and are

46
Q

when are beta blockers used?

A

used for the management of cardiac arrhythmias, cardio-protection after a heart attack, and hypertension.

47
Q

what is acetylcholinesterase?

A

An enzyme that catalyzes the breakdown of the neurotransmitter acetylcholine.

48
Q

what do beta blockers do?

A

As beta-adrenergic receptor antagonists, they diminish the effects of epinephrine (adrenaline) and other stress hormones.

49
Q

what is atropine?

A

An alkaloid extracted from the plant deadly nightshade (Atropa belladonna) and other sources.

50
Q

how is atropine used?

A

used as a drug in medicine for its paralytic effects (e.g., in surgery to relax muscles, in dentistry to dry the mouth, in ophthalmology to dilate the pupils), though overdoses are fatal.

51
Q

what does B2 stimulation lead to?

A

vasodilation

52
Q

what does a1 stimulation cause?

A

vasoconstriction

53
Q

what does stimulation of B1 and B2 cause?

A

increase HR, contractility and speed

54
Q

What is the bidirectional sporadic capture for DCV delivery?

A

Neurotransmission requires anterograde axonal transport of dense core vesicles (DCVs) containing neuropeptides and active zone components from the soma to nerve terminals. However, it is puzzling how one-way traffic could uniformly supply sequential release sites called en passant boutons.

55
Q

what is PVAT?

A

Perivascular adipose tissue (PVAT) is fat which borders most vessels and signals to the vascular wall. In healthy conditions PVAT exercises an anti-contractile effect in the underlying vessels through PVAT-derived relaxing factors.

56
Q

what is the role of PVAT in neurotransmission?

A

can be pro-contractile or anti-contractile
release endocrine hormones that we don’t really understand

57
Q

what happens with PVAT in normal health?

A

PVAT secretes anti-contractile factors that relax the underlying artery. PVAT’s contributions to vascular function include more than production of vasoactive substances. We hypothesized that PVAT benefits the artery by assisting the function of stress (–induced) relaxation

58
Q

Which prejunxtional mechanism reduces the amount of noradrenaline released at a nerve terminal?

A

Stimulation of alpha 2 adrenoreceptors

59
Q

Where is noradrenaline located in a blood vessel?

A

At the border between the adventicia and the tunica media

60
Q

What is the consequence of aldosterone release from the adrenal cortex?

A

Retention of sodium and water in the kidneys

61
Q

Where is ADH synthesised and released?

A

Hypothalamus
Pituitary gland

CVR Week 1 (8 decks)

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