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Physiology > Autonomic Nervous System > Flashcards

Autonomic Nervous System Flashcards

1
Q

What is another name for the autonomic nervous system?

A

visceral efferent system

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2
Q

What are the two branches of the autonomic nervous system?

A

sympathetic and parasympathetic

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3
Q

Autonomic Nervous System Characteristics

A

independent. Composed of efferent fibers forming a reflex pathway responding to visceral afferents.

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4
Q

What are the actions of the ANS controlled by?

A

hypothalamus and reticular formation

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5
Q

Parasympathetic NS

A

conserves and restores energy (rest and digest)

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6
Q

Sympathetic NS

A

prepared the body for emergency situations (fight or flight)

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7
Q

SNS and PNS activity

A

parasympathetic is continuously active

Sympathetic has low resting tone but is capable of bouts of great activity

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8
Q

Anatomy of the ANS

A

is a 2 neuron system.
1. 1st neuron in cell body
2 . 2nd neuron on ganglion in the peripheral NS

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9
Q

1st Neuron Cell Body

A

preganglionic Neuron

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10
Q

2nd Neuron Cell Body

A

postganglionic neuron

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11
Q

Where do preganglionic ANS nerve fibers leave the CNS?

A 
parasympathetic= craniosacral nervous system
Sympathetic= thoracolumbar nervous system
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12
Q

Anatomy of the Preganglionic Cell Bodies

A

all pre-ganglionic cell bodies are in the lateral horn of T1-L3. Short axons run to sympathetic trunk ganglia. Form the sympathetic trunk

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13
Q

Sympathetic Trunk

A

some individual ganglion have fused together. Head supplied by spinal nerves from C8-T5. Part of the vagosympathetic trunk

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14
Q

Anatomy of post-ganglionic neuron

A

has long axon. Leaves the ganglion to reach its target organ via a spinal nerve or separate nerve

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15
Q

Targets of sympathetic nervous system

A
  1. dilate pupil
  2. constrict blood vessels in skin and gut
  3. bronchodilation
  4. increase heart rate and force of contraction
  5. piloerection
  6. decrease peristaltic activity and secretion in gut
  7. stimulation of secretion from sweat glands
  8. stimulate release of norepinephrine and epinephrine from adrenal medulla
  9. close the internal urethral sphincter
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16
Q

First neuron in parasympathetic NS

A

originates from the brainstem or from the sacral spinal cord= craniosacral system. Has a long preganglionic axon. Parasympathetic ganglia are located close to or within the wall of their target organ. 2nd neuron has small postganglionic axon in target organ wall

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17
Q

Origin of the first parasympathetic NS Neuron

A

in cranial nerves nuclei in brainstem (long preganglionic axon leaves CNS via cranial nerves 3, 7, 9, and 10 to reach ganglia in the viscera of head region. or via cranial nerve 10 to reach the cervical, thoracic, or abdominal viscera)or in sacral spinal cord (neuronal cell bodies in S1-S3. Long preganglionic axon leaves CNS via segmental spinal nerves. Terminates on cell body of 2nd neuron in ganglion in pelvic viscera)

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18
Q

Target Organs of Parasympathetic Fibers

A

pupil size via CN III (oculomotor nerve)
salivary glands via CN VII (facial n.) and IX (glossopharyngeal n.)
Lacrimal glands via CN VII (facial nerve)

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19
Q

Cranial Nerve X

A

vagus nerve. Projects to parasympathetic ganglia in or close to thoracic and abdominal organs- in cardiac muscles to regulate heart rte, gastrointestinal tract to regulate motility and secretions, and lungs to regulate secretion

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20
Q

Where do sacral preganglionic neurons exit the CNS?

A

via spinal nerves (S1-S3) and form the pelvic nerces to end in the pelvic viscera (rectum, bladder, genitalia)

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21
Q

Target Organs of the Parasympathetic Fibers

A
  1. constriction of pupil
  2. accomodation of the lens
  3. bronchoconstriction
  4. decrease heart rate
  5. increase peristaltic activity and secretion in gut
  6. release of saliva
  7. contracts the bladder
  8. stimulates erection
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22
Q

Neurotransmitter

A

molecule released by a neuron at the level of the synapse following an action potential. Acts as a chemical messenger, binds to post-synaptic receptors, generates a change in function of the target cell

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23
Q

Adrenal Medulla

A

innervated by sympathetic fibers. Preganglionic neuron secreted acetylcholine. Postganglionic chromaffin cells acting like 2nd neurons secrete epinephrine (and a small amount of norepinephrine). The epinephrine is released in the blood circulation allowing diffuse systemic effects following sympathetic stimulation

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24
Q

General Visceral Afferent System

A

receptors to pressure, stretch, and chemical changes

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25
Q

Specific Visceral Afferent System

A

receptors to taste and olfaction

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26
Q

What only receives sympathetic innervation?

A

vessels

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27
Q

Functions of the Sympathetic Nervous System

A
  1. response to an emergency situation
  2. response to physical or emotional stress
  3. secretion of epinephrine by adrenal glands prolongs the effect
  4. digestion and urination are inhibited
  5. helps with thermoregulation and allows pupils to dilate in low ambient light in less stressful situations
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28
Q

Functions of the Parasympathetic Nervous System

A
  1. digestion and food absorption
  2. pupillary constriction
  3. decreases heart rate
  4. urination
  5. defecation
  6. lacrimation
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29
Q

How to Increase Blood Pressure

A
  1. less stretching of the baroreceptors
  2. sympathetic stimulation
  3. peripheral vasoconstriction and increase vascular resistance
  4. increase blood pressure
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30
Q

How to Decrease Blood Pressure

A
  1. increased blood pressure
  2. increased stretching of the baroreceptors
  3. inhibition of sympathetic-mediated vasoconstriction
  4. decreases vascular resistance
  5. decreases blood pressure
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31
Q

How does the Sympathetic NS increase Heart Rate?

A

by increasing SA node discharges, conduction of impulses, and contraction of the ventricles and atria

32
Q

What are the effects of an increase in BP and HR?

A

increased blood flow and oxygen supply to skeletal muscles

33
Q

Where is the sinoatrial node?

A

right atria

34
Q

Where are the stretch receptors?

A

the wall of the internal carotid artery and aorta

35
Q

How does the Parasympathetic NS decrease heart rate?

A

by decreasing SA node discharges

36
Q

What is pupillary constriction mediated by?

A

parasympathetic activation (pupillary light reflex pathway)

37
Q

What is pupillary dilation mediated by?

A

sympathetic activation (Horner’s Pathway)

38
Q

Pupil Constriction

A
  1. light into eyes
  2. goes through optic nerve to optic chiasm.
  3. crossover to pretectal nucleus
  4. to CN III
  5. Leaves prasympathetic nucleus to oculomotor nerve to constrict eyes
39
Q

Pupil Dilation

A
  1. Comes from hypothalamus
  2. follows tectotegmental spinal pathway to preganglionic sympathetic neurons (T1-T3)
  3. Through cervical spinal cord
  4. sympathetic nerve goes to smooth muscles of periorbital area, eyelids
40
Q

Ability to urinate

A

micturition

41
Q

Storage phase (urine)

A

regulated by sympathetic NS; thoracolumbar region

42
Q

Micturition

A

regulated by parasympathetic NS; craniosacral region

43
Q

Sympathetic Bladder Innvervation

A

Hypogastric nerve

44
Q

Location of Hypogastric Nerve

A

L1-L4 in dog, L2-L5 in cat

45
Q

Receptors of Hypogastric Nerve

A
  1. beta receptor- stimulation relaxes detrusor muscle to store urine
  2. alpha receptor-stimulation constricts internal urethral sphincter (smooth muscle)
  3. sensory branches to perceive pain
46
Q

Parasympathetic Bladder Innervation

A

pelvic nerve

47
Q

Location of Pelvic Nerve

A

S1-S3

48
Q

Receptor to Pelvic Nerve

A

acetylcholine receptor. Stimulation contracts detrusor to evacuate urine. Sensory branches sense bladder wall stretch and transmit information to pontomedullary micturition center

49
Q

Somatic Innervation of the Bladder

A

pudendal nerve

50
Q

Location of Pudendal Nerve

A

S1-S3

51
Q

Receptor to Pudendal Nerve

A

acetylcholine receptor. Simulation constricts external urethral sphincter. Sensory and motor to external urethral sphincter (skeletal muscle)

52
Q

Brainstem control of micturition

A

Pontine Micturition center

53
Q

Where is the pontine micturition center?

A

reticular formation

54
Q

What are the functions of the pontine micturition center?

A
  1. storage and evacuation
  2. receives information from spinal cord regarding bladder
  3. sends information to the bladder via spinal cord (reticulospinal tracts)
55
Q

Cerebrum control of micturition

A

conscious control of micturition

56
Q

Cerebellum control of micturition

A

inhibitory influence on micturition

57
Q

Spinal cord control of micturition

A

reticulospinal tracts. Terminate in ventral horn gray matter. LMN to bladder

58
Q

To store urine

A
  1. facilitation of pudendal nerve to contract the external sphincter muscle
  2. facilitation of hypogastric nerve to alpha receptors to contract internal sphincter muscle and beta receptors to relax detrusor muscle further
  3. Inhibition of pelvic nerve to detrusor muscle to allow relaxation
59
Q

Process of Micturition

A
  1. inhibition of hypogastric nerve (beta receptors on detrusor, alpha receptors on internal sphincter m.)
  2. inhibition of pudendal nerve to relax external sphincter
  3. facilitation of pelvic nerve to contract detrusor
60
Q

Sympathetic Innervation of Defecation

A

input from hypogastric nerve and L1-L4/L5 spinal cord segments. Innervated descending colon, rectum, and internal anal sphincter- excitatory to internal anal sphincter but inhibitory to descending colon and rectum

61
Q

Parasympathetic Innervation of Defecation

A

input from pelvic nerve, S1-S3 spinal cord segments. Innervates descending colon and rectum

62
Q

Somatic Innervation of Defecation

A

Input from pudendal nerve and S1-S3 spinal cord segments. Innervates striated muscle of the external anal spincter

63
Q

Fecal Continence

A
  1. As colon fills, pressure stimulates sensory branch of pelvic nerve and that sensory information is sent to spinal cord, and subsequently to the brainstem (pontomedullary centers) and cerebral cortex
  2. Facilitation of the pudendal nerve causing contraction of the external anal sphincter
  3. Facilitation of the hypogastric nerve causing contraction of the internal anal sphincter
  4. inhibition of the pelvic nerve, causing relaxation of the colon and rectum
64
Q

Defecation Process

A
  1. Full colon results in stretch of colon and rectum, which causes ascending sensory information to travel via pelvic nerve to spinal cord, brainstem, and cerebrum
  2. signal to activate defecation is sent to brainstem, descends spinal cord via reticulospinal tracts
  3. inhibition of the hypogastric nerve causing relaxation of colon and internal anal sphincter
  4. inhibition of pudendal nerve causing relaxation o the external anal sphincter
  5. facilitation of pelvic nerve, causing contraction of the colon and rectum
65
Q

Horner’s Syndrome

A

Loss of sympathetic supply to the eye

66
Q

Classical Signs of Horner’s Syndrome

A
  1. miosis
  2. ptosis
  3. enophthalmos
  4. 3rd eyelid protrusion/rpolapse
  5. +/- associated with loss of vascular tone on affected side vasodilation (warm skin, sweating)
67
Q

Causes of Horner’s Syndrom

A

any lesion along the path of the sympathetic innervation to the eye; can also be idiopathic

68
Q

Organophosphate Toxicity

A

causes irreversible inhibition of acetylcholinesterase

69
Q

Carbamate Toxicity

A

causes reversible inhibition of acetylcholinesterase

70
Q

Clinical signs of carbamate and organophosphate toxicity

A
  1. excessive parasympathetic stimulation (muscarinic crisis)
  2. bradycardia
  3. salivation
  4. lacrimation, miosis
  5. increase bronchial secretion
  6. urine dribbling
71
Q

Miosis

A

small pupil

72
Q

Ptosis

A

drooping of eyelid

73
Q

Enophthalmos

A

sunken eye

74
Q

Nicotinic Crisis

A

muscle twitching, tremors

75
Q

Central Stimulation

A

anxiety, restlessness, seizures

Physiology (16 decks)

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