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Cardiology > 2.3.1 Autonomic Nervous System and Cardiovascular Control Mechanisms > Flashcards

2.3.1 Autonomic Nervous System and Cardiovascular Control Mechanisms Flashcards

1
Q

How could difficulty swallowing, constipation or fecal incontinence be symptoms of MSA?

A

If there is sympathetic denervation, there will be hyperactive motility and loss of sphincter tone - increased parasympathetic response leading hyperactive peristalsis and relaxation of the sphincter causing fecal incontinence

If there is parasympathetic denervation, there will be a reduction in the mobility and increase in the sphincter tone. This is due to sympathetic response not favoring peristalsis and favoring contraction of the sphincter

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2
Q

What is the effect of the parasympathetic system on nitrergic receptors?

A

Activation through these will always cause relaxation of vascular smooth muscle.

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3
Q

Upon standing what happens to plasma hormones in autonomic failure (MSA)?

A
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4
Q

What are the early symptoms of MSA?

A

erectile dysfunction

urinary retention or incontinence

pupil constriction (miosis)

loss of sweating (anhydrosis)

dry mouth (xerostomia)

swallowing difficulty (dysphagia)

airway obstruction

HR disturbance

constipation or fecal incontinence

orthostatic hypotension/supine hypertension

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5
Q

What are the two primary transmitters of the sympathetic ANS? Synthetic enzymes? Termination of signal? Receptor? Effects?

A
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6
Q

What is the role in the renin-angiotension system in regulating pressure in the body?

A

Plasma renin is increased by diminished renal blood flow and by sympathetic activation.

Angiotensin II has intermediate effects on CV control by direct actions on increasing arteriolar smooth muscle contraction.

Ang II mediates long-term volume increases by directly suppressing urine formation and indirectly causing aldosterone release from the adrenal cortex.

Ang II augments (increases) NE release from sympathetic varicosities via Ang II heteroceptors.

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7
Q

What is the body’s response to sympathetic activation of Beta 3 receptors?

A

Excitation of adipocytes

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8
Q

Describe sympathetic noradrenergic transmission.

A
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9
Q

What can happen to the pupil with denervation of the sympathetic and parasympathetic nerve fibers?

A

If there is sympathetic denervation, not enough NE will act on the dilator muscle to overcome ACh acting on constricting muscle - leading to a smaller pupil

If parasympathetic denervation occurs, the opposite will occur and there will be a dilated pupil.

Either could be a symptom of MSA

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10
Q

What enzyme present in the adrenal medulla makes it different from sympathetic axons (otherwise they have the same enzyme profile)?

A

Phenylethanolamine N-methyl transferase (PNMT), allows for the production of epinephrine

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11
Q

What are the excitatory muscarinic receptors? Inhibitory?

A

Excitatory: M1, M3, M5

Inhibitory: M2, M4

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12
Q

How do nerves influence vascular function? How is this achieved through arteries and veins?

A

Nerves innervate arterial and venous smooth muscle. Excitatory innervations contract vascular smooth muscle leading to decreased vessel diameter. Inhibitory innervation relaxes smooth muscle thus increasing the diameter.

Arteriolar contraction increases the resistance. Vein/venule contraction increases venous return

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13
Q

What is the pathway by which baroreceptors will act to compensate for decreased arterial pressure or venous return?

A
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14
Q

What does the parasympathetic system mediate?

A

Feed and breed - characterized by discrete changes in actiity to selected organs

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15
Q

What is the mechanism by which erectile dysfunction can be a symptom of MSA?

A

Parasympathetic denervation leads to less NO acting on guanyl cyclase to produce cGMP.

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16
Q

Why would it be important to change blood vessel diameter in order to change TPR?

A

If arterial blood pressure decreases due to pooling of blood or loss, this could impair brain profusion which could lead to syncope.

Decreasing diameter of arterial vessels in certain vascular beds will increase TPR, which will increase arterial pressure. If TPR increases and CO does not change MAP will increase.

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17
Q

In which two structures do sympathetic ganglia form?

A

Paravertebral chain and prevertebral ganglion

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18
Q

Describe the selectivity of eprinephrine, isoproterenol, phenylephrine, clonidine, norepinephrine for the adenoreceptors (α1,2 and β1,2,3)

A
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19
Q

Why might changing tone be important in a person going from supine to standing?

A

Changes in pressure results in decreased venous return leading to decreased CO and thus decreased MAP. If arterial pressure falls below a certain point it can result in syncope.

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20
Q

What makes epinephrine different from norepinephrine?

A

Epinephrine activates all adrenoreceptors including beta 2 receptors - this elicits skeletal muscle vasodilation. TPR and MAP may not be changed

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21
Q

Draw a concept map for the baroreflex response to increased venous return or increased arterial pressure

A
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22
Q

What is cardiac tone determined by?

A

Concurrent discharge of excitatory sympathetic and inhibitory parasympathetic

HR is increased by increasing sympathetic or decreasing para

HR is decreased by decreasing sym or increasing para

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23
Q

What is vascular tone determined by?

A

It is determined by the balance between vasoconstrictor influences (mainly sympathetic nerves acting on alpha 1 receptors) and vasodilatory factors.

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24
Q

What is vaso-vagal syncope?

A

Abnormally robust response to emotional stimuli leading to withdrawl of vasomotor tone and vagal parasympathetic activation.

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25
Q

What is different about autonomic motor pathways, voluntary motor pathways, sensory pathways?

A

autonomic motor pathways: final interneuronal synapse b/t CNS preganglionic neuron and a peripheral postganglionic neuron

Voluntary motor pathways: neurons aren’t in ganglia; CNS neurons project directly to muscle

Sensory pathway: Neurons in ganglia, but no synapse (pseudo-unipolar neurons project axons to both the periphery and CNS)

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26
Q

What is the body’s response to sympathetic activation of beta 2 receptors?

A

Relaxation of smooth muscle (found mainly in skeletal muscle)

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27
Q

Where is the parasympathetic ANS innervate the spinal cord?

A

Cranial Nerves (CN III, VII, IX, X) and Sacral

Cranio-Sacral

28
Q

What is multiple systems atrophy? What famous person had it?

A

Progressive neurodegenerative condition, degeneration of autonomic preganglionic neurons, can lead to disturbances in motor function and balance

Johnny Cash

29
Q

When a person goes from laying down to standing, how can arterial vasoconstriction, venoconstriction, and increasing cardiac tone work to maintain BP?

A

Arterial vasoconstriction - Sympathetic activation which will increase TPR - increased TPR will increase MAP

Venoconstriction - Sympathetic contraction of venous smooth muscle reduces compliance and capacitance. Increased venous pressure forces blood back to the heart increasing venous return and CO.

Increased cardiac tone - by increasing tone and decreasing vagal parasympathetic ton, HR and force of contraction increase, making the heart a more effective pump (increasing CO)

30
Q

Describe parasympathetic transmission

A
31
Q

How does the chemoreflex differ from the baroreflex?

A
32
Q

How do sympathetic nerves act to constrict and decrease blood vessel diameter?

A

Sympathetic nerves are the only constrictor nerves. Normally sympathetic nerves only constrict. They excite vascular smooth muscle primarily by NE acting on alpha 1 receptors.

33
Q

What is atrial natriuretic peptide?

A
34
Q

Draw a concept map of the baroreflex response pathway to decreased venous return or decreased arterial pressure

A
35
Q

What are some factors that can override the baroreflex?

A

Mild pain, anxiety and excitement can raise blood pressure beyond the normal set point

Intense pain and fear can lead to markedly decreased cardiac output (vaso-vagal syncope)

36
Q

What are cardiopulmonary baroreceptors?

A

These measure venous return. They are located in the RA, vena cava, and pulmonary vessels and stretch with more venous return. The venous pressure range is from 0-20mmHg, and more pressure means more nerve firing.

37
Q

Why would changing blood vessel diameter be important to changing cardiac output?

A

Venules and veins store roughly 2/3rds of total blood volume.

Venous smooth muscle contraction forces blood back to the heart. Increased venous return will increase CO.

Increase in CO if TPR doesnt change will increase MAP.

38
Q

What is tone?

A

Level of activity of nerves and targets.

High nerve discharge rate or contractile state = high tone

39
Q

After transmission of an excitatory signal from the preganglionic axon to the ganglion, through what structure does the postganglionic axon distribute the signal to effector cells?

A

Varicosities found in the ground plexus

40
Q

What is denervation supersensitivity?

A

A process whem many autonomic axons degenerate, and there is a needed compensation to increase the target response to reduced amounts of transmitter. In both parasympathetic and sympathetic targets, numbers and sensitivity of receptors increase.

In postganglionic axon degeneration, there are fewer varicosities leading to less reuptake. This allows NE concentrations to stay higher for longer (prejunctional supersensitivity).

41
Q

What is the Cushing Reaction?

A

This occurs when intracranial pressure is abnormally high. If intracranial pressure exceeds venous pressure, cerebral perfusion is impaired. This can result in a central ischemic response even though systemic arterial pressure is normal or elevated.

42
Q

How do parasympathetic nerves act to dialate blood vessels?

A

Induce discrete dilation via nitric oxide

43
Q

How can urinary retention or incontinence be a symptom of MSA?

A

Sympathetic degeneration can lead to incontinence

Parasympathetic denervation can lead to retention

44
Q

The sympatho-adrenal system mediates what?

A

Fight or flight response - characterized by broad diffuse system activation

45
Q

Why would changing blood vessel diameter be important for changing local blood flow?

A

These are important for discrete reflexes, such as genital erection or gastrointestinal vasodilation during a meal. With local arterial dilation, local resistance is decreased so flow can increase. This does not change TPR significantly.

46
Q

What is different about the varicosity as compared to the rest of the ground plexus?

A

The varicosity is a portion where the ground plexus isn’t covered by a schwann cell allowing for signal transmission to a target cell

47
Q

What will ADH’s effect be on vascular smooth muscle?

A

This will lead to increased arterial resistance thus increasign blood pressure.

It will also decrease venous compliance subsequently increasing venous return.

48
Q
A
49
Q

Where is the sympathetic ANS innervate the spinal cord?

A

Thoracic and lumbar

Thoraco-lumbar

50
Q

What are the sites of autonomic neurotransmission?

A

Varicosities

51
Q

Nicotinic cholinergic ganglionic receptors are blocked by what? What are they not blocked by?

A

Hexamethonium, not curare

52
Q

What are some of the effects of the parasympathetic system on cholinergic receptors?

A

This will always cause:

  • Activation of non-vascular smooth muscle
  • Relaxation of sphincters
  • Inhibition of cardiac activity
  • Activation of glands
53
Q

How do baroreceptors affect adrenomedullary catecholamine release?

A

They do not affect it much

54
Q

What is carotid sinus syndrome?

A

Abnormal sensitivity of the carotid sinus baroreceptors to touch or stretch. Slight pressure to the neck is perceived as high blood pressure, leading to vagal slowing of the heart and fainting.

55
Q

What is orthostatic hypotension?

A

Inability to compensate for reduced CO associated with upright posture.

56
Q

What is the body’s response to sympathetic activation of alpha 1 receptors?

A

Contraction of smooth muscle

57
Q

What is the effect of ADH on the kidney?

A

This responds to decrease CO or BP. It will cause the decrease of urine production. This will lead to an increase in plasma volume and central venous pressure thus increasing venous return.

58
Q

Where does sympathetic nervous system tend to act to increase vasoconstriction?

A

Vasoconstriction by SNS primarily occurs in beds with alpha 1 adrenoreceptors.

This leads to increased renal and splanchnic arteriolar resistance.

Maybe a little but not as much cutaneous and skeletal muscle.

59
Q

What are arterial baroreceptors?

A

These are located in the aortic arch and carotid sinus, and assesses blood flow to the entire body and brain. Increasing pulse pressure and MAP result in increased discharge rates over a range of 60-180 mmHg.

60
Q

What are the two primary transmitters of the parasympathetic ANS? Synthetic enzymes? Termination of signal? Receptor? Effects?

A
61
Q

What morphology helps define the ANS?

A

Last interneuronal synapse in a peripheral ganglion

62
Q

What is the body’s response to sympathetic activation of beta 1 receptors?

A

Excitation of the heart and kidney

63
Q

This the main neurotransmitter of the parasympathetic system and comprises 5% of the sympathetic NT. What is its excitatory receptor?

A

Ach, nicotinic receptor

64
Q

What differs the sympathetic nervous system that uses Ach from the parasympathetic system?

A

The sympathetic nervous systems has convergence leading to a broad range of effects. Whereas the parasympathetic nervous system has a 1:1 relationship leading to discrete effects.

65
Q

What is the body’s response to sympathetic activation of alpha 1, beta 2 and M?

A

Increasing glandular secretion

66
Q

What is the Central Ischemic Response?

A

This is when reduced perfusion of the medulla results in discharge of sympathetic centers (C1). This is a last ditch effort to restore MAP and CO.

Cardiology (46 decks)

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