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SMP - Neurophysio Exam 1 > Lecture 12 - Visceral Motor System > Flashcards

Lecture 12 - Visceral Motor System Flashcards

1
Q

What is the efferent division of the visceral NS?

A

Autonomic NS

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2
Q

Does the autonomic NS have both CNS and PNS components?

A

YUP

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3
Q

Main function of autonomic NS?

A

Regulate the activity of vital organs

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4
Q

If consciousness of a patient is greatly affected, can the autonomic NS still be functioning?

A

YUP

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5
Q

What are the 3 branches of the autonomic NS?

A
  1. Sympathetic NS
  2. Parasympathetic NS
  3. Enteric NS
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6
Q

Sympathetic stimulation on heart?

A
  1. Increased heart rate

2. Increase in force of contraction

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7
Q

Sympathetic stimulation on blood vessels?

A

Constriction

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8
Q

Sympathetic stimulation on lungs?

A

Bronchodilation

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9
Q

Sympathetic stimulation on GIT?

A
  1. Decreased motility
  2. Sphincter contraction
  3. Decreased secretions
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10
Q

Parasympathetic stimulation on heart?

A
  1. Decreased heart

2. Decreased force of contraction (weak effect)

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11
Q

Parasympathetic stimulation on blood vessels?

A

No effect except in genitalia (dilation)

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12
Q

Parasympathetic stimulation on lungs?

A

Bronchoconstriction

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13
Q

Parasympathetic stimulation on GIT?

A
  1. Increased motility
  2. Sphincter relaxation
  3. Increased secretions
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14
Q

Describe the autonomic NS pathway.

A

Preganglionic (CNS) neuron bodies in brainstem and spinal cord -> Preganglionic fibers (CNS) => Postganglionic (PNS) primary motor neurons (bodies and fibers) -> viscera

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15
Q

Are the preganglionic neuron bodies in the CNS sympathetic or parasympathetic?

A
  1. Brainstem: parasympathetic

2. Spinal cord: both

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16
Q

Where are the preganglionic neuron bodies found in the spinal cord?

A

Ventral horn

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17
Q

What are the 3 autonomic ganglia of the PNS?

A
  1. Paravertebral (chain) ganglia
  2. Prevertebral ganglia
  3. Intramural ganglia
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18
Q

What are the 2 main differences between the somatic efferent pathway and the autonomic pathway?

A
  1. LMNs synapse directly onto skeletal muscle allowing for precise innervation vs autonomic pathways involve 2 neurons and is diffuse with divergent targeting and indirect control
  2. LMNs are heavily myelinated therefore have faster conduction vs ANS preganglionic neurons are slightly myelinated and postganglionic ones are not at all, therefore have slower conduction
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19
Q

Describe the sympathetic outflow pathway.

A

Preganglionic neuron in spinal cord => paravertebral or prevertebral ganglion => postganglionic axon => viscera

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20
Q

What is the difference between paravertebral and prevertebral ganglia?

A

Paravertebral ganglia are closer to the spinal cord vs prevertebral ganglia are closer to the end organs

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21
Q

Describe the parasympathetic outflow pathway.

A

Preganglionic neuron => intramural ganglion => postganglionic axon => viscera

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22
Q

Does the autonomic system have myotomes?

A

NOPE

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23
Q

Where do the sympathetic preganglionic neurons synapse along the spinal cord? What do we call this part?

A

T1 to L2 spinal segments = Intermediolateral column

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24
Q

Where do the parasympathetic preganglionic neurons synapse along the spinal cord?

A
  1. Brainstem cranial nerve nuclei (III, VII, IX, X)

2. S2 to S4 spinal segments (sacral spinal cord)

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25
Q

What part of the spinal cord horns are sympathetic preganglionic neurons found?

A

Lateral horns

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26
Q

What part of the spinal cord horns are parasympathetic preganglionic neurons found?

A

Intermediate zone

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27
Q

Where are the intramural ganglia of the parasympathetic NS located?

A

Generally near target tissues (often on blood vessel)

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28
Q

What is the NT released by both pre and post ganglionic parasympathetic neurons?

A

ACh

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29
Q

Do most organs have dual sympathetic/parasympathetic innervation?

A

YUP with a few exceptions

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30
Q

Parasympathetic NS: how does the length of the preganglionic axons compare to the postganglionic axon?

A

Longer preganglionic axon

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31
Q

What is the primary control center of the autonomic NS?

A

Hypo

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32
Q

Sympathetic NS: how does the length of the preganglionic axons compare to the postganglionic axon?

A

Longer postganglionic axons

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33
Q

What is the NT released by preganglionic sympathetic neurons?

A

ACh

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34
Q

What is the NT released by postganglionic sympathetic neurons?

A

NE, except for sweat glands (ACh)

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35
Q

What is the vagus nerve made of? What does it innervate?

A

Preganglionic fibers from the dorsal motor nucleus in the medulla synapsing on postganglionic neurons in intramural ganglia near many viscera in thorax and abdomen

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36
Q

What part of the autonomic system is the vagus nerve part of?

A

Parasympathetic

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37
Q

Where is the dorsal motor nucleus of the vagus nerve found?

A

Cranial nerve nucleus for the vagus nerve in the medulla

38
Q

What is the vagovagal reflex?

A

Stomach becomes distended as it fills with food => vagus nerve afferent stimulates medulla => medulla stimulates vagus nerve efferent to stimulate parasympathetic responses like HCl and gastrin secretion in stomach and increased gut motility

39
Q

Doe the vagus nerve only have an efferent component?

A

NOPE, afferent also

40
Q

What is vasovagal syncope? What causes this? For who is it most common?

A

Vagus nerve hyperactivation associated fainting due to stimulation by GI illness, pain, or stress leading to low BP and heart rate which causes fainting

Most common in young people

41
Q

What is a rare symptom of vasovagal syncope?

A

Localized seizure-like activity

42
Q

What part of the autonomic system are the pelvic splanchnic nerves part of?

A

Parasympathetic

43
Q

What are the pelvic splanchnic nerves made of?

A

Preganglionic fibers from the sacral spinal cord synapsing on postganglionic neurons in intramural ganglia near viscera in abdomen and pelvis

44
Q

What 2 physiological processes do the pelvic splanchnic nerves control?

A
  1. Urination

2. Erection

45
Q

What are the 5 types of nerves of the bladder? Function for each?

A

3 efferents:

  1. Sympathetic NS: contracts internal sphincter = KEEP PEE IN
  2. Parasympathetic NS (splanchnic nerves): contracts wall muscles and relaxes internal sphincter = PEE
  3. Somatic motor: controls external sphincter

2 afferents:

  1. Sympathetic NS: stimulation of efferent neurons due to mild stretch
  2. Parasympathetic NS (splanchnic nerves): stimulation of efferent neurons due to full stretch
46
Q

Why do newborns and infants pee themselves?

A

They have not yet developed the ability to control the bladder’s external sphincter

47
Q

What are the drugs Viagra, Cialis, and Levitra used to treat? How do they work? Side effects?

A
  1. Urine retention due to prostate enlargement
  2. Erectile dysfunction

Cause release of ACh from parasympathetic NS => NO release by endothelial cells => increase in cGMP in smooth muscles => decrease in [Ca++] => relaxation

Side effects: decrease in BP and heart rate leading to fainting

48
Q

What organ releases norepi/epi as hormones instead of NTs? What is it composed of? What is it innervated by?

A

Adrenal medulla composed of modified postganglionic neurons = chromaffin cells innervated by preganglionic sympathetic neurons

49
Q

Where is the adrenal medulla located in the body?

A

Right on top of each kidney

50
Q

Are visceral reflexes mono or polysynaptic?

A

Always polysynaptic

51
Q

What are the 2 visceral reflexes pathways? Describe each.

A
  1. Long reflex: afferent neuron => interneuron in gray matter of the brain or spinal cord => preganglionic neuron => autonomic postganglion (sympathetic or parasympathetic) => postganglionic neuron
  2. Short reflex: afferent neuron => interneuron in autonomic postganglion (sympathetic or parasympathetic) => postganglionic neuron
52
Q

What is the main function of the baroreceptor reflex?

A

Regulation of heart rate and BP

53
Q

Describe the pathway of the baroreceptor reflex.

A

Stretch receptors in walls of internal carotid arteries and aorta => visceral afferents of cranial nerves 9 and 10 (accessory and hypoglossal) => cardioregulatory center in medulla => parasympathetic (cranial nerve X) and sympathetic efferent fibers synapse on heart and SNS on adrenal medulla CV center

54
Q

What autonomic NS is activated by a BP increase? How does it reduce it?

A

Parasympathetic NS => decreased heart rate => decreased BP

55
Q

What autonomic NS is activated by a BP decrease? How does it increase it?

A

Sympathetic NS => increased heart rate => increased BP

56
Q

What type of receptors are autonomic postganglionic ones?

A

Ionotropic ACh receptors

57
Q

What type of receptors are visceral autonomic ones? What do they regulate?

A

GPCRs

Regulate intracellular signaling and glycogenolysis

58
Q

Describe the parasympathetic NT pathway.

A

Preganglionic neuron releases ACh =>
postganglionic
nicotinic receptors leading to ACh release =>
target structure
muscarinic receptors => inhibition or excitation of target structure

59
Q

How can parasympathetic innervation on a target structure lead to either inhibition or activation? Example?

A

Muscarinic receptors can have different effects depending on location

Example:

  • Heart is inhibited via hyperpolarization leading to bradycardia
  • Digestive tract smooth muscle is excited by depolarization leading to contractions
60
Q

What is bradycardia?

A

Abnormally slow heart action

61
Q

List the 5 types of parasympathetic muscarinic receptors on target tissues and their effect.

A 
M1: contraction
M2: relaxation
M3: contraction 
M4: ?
M5: ?
62
Q

Describe the sympathetic NT pathway.

A

Preganglionic neuron releases ACh => postganglionic nicotinic receptors leading to NE release => target strcuture adrenergic receptors (β1, α1) => β1: tachycardia OR α1: blood vessel constriction

63
Q

What is tachychardia?

A

Abnormally fast heart action

64
Q

What % of epi is released by the adrenal medulla?

A

70%

65
Q

What are beta blockers used for? What type?

A

Beta 1 blockers to treat hypertension (sometimes non-selective beta blockers are used, but not as safe, especially for asthmatics)

66
Q

Where are beta 1 adrenergic receptors located?

A

Heart

67
Q

Where are beta 2 adrenergic receptors located? What do they cause?

A

Lungs, uterus, gut: relaxation

68
Q

Do alpha adrenergic receptors have more affinity for norepi or epi?

A

Norepi

69
Q

Do beta adrenergic receptors have more affinity for norepi or epi?

A

Epi

70
Q

What is an example of a non-selective beta blocker?

A

Propanolol

71
Q

What is an example of a beta 1 blocker?

A

Metoprolol

72
Q

Is smooth muscle striated?

A

NOPE

73
Q

Why are smooth muscles unstriated?

A

Because their myosin (thick) and actin (thin) filaments are not organized the same way as in skeletal muscle

74
Q

What controls smooth muscles?

A
  1. Autonomic NS

2. Hormones

75
Q

Is cardiac muscle a smooth muscle?

A

NOPE

76
Q

4 functions of smooth muscles? Give an example for each.

A
  1. Motion (pilomotors = hair raising muscles)
  2. Expelling content of hollow organs (G.I. tract)
  3. Changing cross-section dimensions of tubular organs
    (airways, blood vessels)
  4. Changing dimensions of passive organs (ciliary
    muscles/lens)
77
Q

What are smooth muscles?

A

All internal contractile organs except the heart

78
Q

What are the 2 types of smooth muscle? 2 names for each

Which one is more prevalent?

A
  1. Multiunit = neurogenic

2. Unitary = myogenic (majority of smooth muscles)

79
Q

Where are multiunit smooth muscles found?

A

In areas that require fine motor movement: iris, hair follicles (pili erector), ciliary muscle, large blood vessels, airways

80
Q

Describe the cell membranes of multiunit smooth muscles. What does this allow?

A

They are electrically isolated to allow for finer muscle control.

81
Q

What does it mean for multiunit smooth muscle cells to be neurogenic?

A

They have few muscle fibers/cells per neuron

82
Q

What do unitary smooth muscle cells form?

A

Syncytium = functional group of interconnected cells

83
Q

What is the activity of unitary smooth muscle cells like?

A

Contraction INITIATED by the myocyte itself, not innervation or hormones

84
Q

Which smooth muscles have a higher innervation ratio: unitary or multiunit?

A

Multiunit

85
Q

Where are unitary smooth muscles found? 6 locations

A
  1. GI tract
  2. Uterus
  3. Urethra
  4. Arterioles
  5. Capillaries
  6. Sphincters
86
Q

What permits coordinated contraction of myogenic smooth muscles?

A

Gap junctions

87
Q

Can unitary smooth muscles be innervated by the autonomic nervous system as well?

A

Yup

88
Q

How do smooth muscle synapses differ from those at the NMJ? 2 ways

A
  1. They include varicosities that release NTs into a WIDE synaptic cleft, so the junction is more diffuse making the signaling less discrete and slower than at the NMJ
  2. The possynaptic receptors are GPCRs, allowing for graded potentials
89
Q

Describe the 3 different action potentials that go through smooth muscle cells.
What is each caused by?
For what type of smooth muscle does the 3rd one happen?

A
  1. Single spike: electrical stimulation, hormone, or stretch
  2. Plateau: due calcium influx through channels that inactivate poorly
  3. Slow wave: much slower, below threshold and due to intracellular calcium: unitary smooth muscle
90
Q

Describe the 7 steps for muscle contraction in smooth muscles.

A
  1. Calcium influx into muscle cell (or released from sarcoplasmic reticulum)
  2. Calmodulin binds calcium for Ca2+-CAM
  3. Ca2+-CAM binds and activates myosin light chain kinase (MLCK)
  4. Myosin hydrolyzes ATP recocking the myosin head for it to be perpendicular to actin = cross bridge release
  5. MLCK phosphorylates the myosin head activating it
  6. Myosin (bound to ADP + Pi) binds to actin
  7. Myosin releases ADP + Pi = contraction (crawling on actin filaments)
  8. ATP binds to myosin= actin release
  9. Myosin light chain phosphatase (MLCP) dephosphorylates myosin, inactivating it
  10. Calcium is resorbed by SR/sarcolemma by Ca-ATPase
91
Q

How does skeletal muscle contraction differ from smooth muscle contraction?

A
  1. Intracellular calcium is key
  2. Ca2+ causes a fast physical change with troponin on actin
  3. Contraction is more rapid
92
Q

Why is smooth muscle cell contraction slower than in skeletal muscle?

A

Because it’s a 2 step enzymatic process with calmodulin activating MLCK

SMP - Neurophysio Exam 1 (13 decks)

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