Chapter 14- The autonomic nervous system Flashcards

1
Q

Somatic nervous system

A

Branch of the PNS, it’s a system responsible for voluntary muscle movements and reflex arcs. Mostly efferent.

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2
Q

Somatic refers to

A

Skeletal muscle tissue

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3
Q

Which neurotransmitter is released by the SNS?

A

Acetylcholine, it has an excitatory effect at is released at all synapses in the SNS

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4
Q

Autonomic nervous system

A

A branch of the PNS, almost all effectors are visceral (involuntary). Branches into the sympathetic and parasympathetic divisions

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5
Q

Autonomic nervous system function

A

Helps maintain a stable internal environment. Regulation of heart rate, blood vessel diameter, pupil size, body temperature, increases/decreases stomach secretions

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6
Q

Effector organs of the SNS

A

Skeletal muscle tissue

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7
Q

Effector organs of the ANS

A

Cardiac muscle, smooth muscle, and glands

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8
Q

SNS efferent pathways

A

A single neuron extends from CNS to effector. Motor neuron cell bodies are located in the CNS, axons in PNS extend to skeletal muscle. Thick and heavily myelinated fibers.

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9
Q

ANS efferent pathways

A

The ANS has a two neuron chain to reach effector, consists of preganglionic and postganglionic neurons.

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10
Q

Preganglionic neuron (ANS)

A

Cell body is located in the CNS, preganglionic axon synapses with second motor neuron. Thin, lightly myelinated fibers

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11
Q

Postganglionic neuron (ANS)

A

Cell body is located outside the CNS, postganglionic axon extends to effector organ. Thin, nonmyelinated fibers

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12
Q

ANS ganglia

A

Ganglia in the ANS are sites of synapse between the preganglionic neuron and the postganglionic neuron. Entirely motor ganglia.

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13
Q

Which neurotransmitters are released by the ANS?

A

Releases norepinephrine or acetylcholine- effect can be excitatory or inhibitory depending on receptors on the effector organ in ANS.

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14
Q

Parasympathetic division function

A

“Rest and digest”- keeps body energy use as low as possible when we are relaxed. Directs “housekeeping” activities- digestion, elimination of waste, low blood pressure and heart rate, constricted pupils.

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15
Q

Where do the fibers of the parasympathetic nervous system originate?

A

The brain and sacral spinal cord. Preganglionic fibers are long, postganglionic fibers are short. The ganglia will always be closer to the effector organ than they are to the nervous system

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16
Q

Cauda equina

A

Sacral spinal cord

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17
Q

Cranial portion of the parasympathetic nervous system

A

Will serve the head, neck, thorax, and abdomen. Preganglionic fibers run in oculomotor, facial, glossopharyngeal, and vagus cranial nerves

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18
Q

Oculomotor nerve

A

Innervates smooth muscle in the eyes and muscle associated with the lens. Effect- lens is stimulated to become thicker

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19
Q

Facial nerve

A

Stimulates large glands of the head (salivary glands, nasal glands, lacrimal glands)

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20
Q

Glossopharyngeal nerve

A

Activates parotid salivary gland. The parotid salivary gland is the largest one

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21
Q

Vagus nerve

A

Provide fibers to neck and almost every organ in the thoracic and abdominal cavities. The vagus nerve is large and complex, so we see plexus formation

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22
Q

Cardiac plexus

A

supplies fibers to the heart, division of the vagus nerve

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23
Q

Pulmonary plexus

A

supplies fibers to the lung, division of the vagus nerve

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24
Q

Esophageal plexus

A

Serves the esophagus. The fibers from the esophageal plexus also extend into the abdominal cavity- innervates liver, gallbladder, stomach, small intestine, pancreas, and proximal half of large intestine

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25
Q

When is the sympathetic nervous system activated?

A

“Fight or flight”: activated when we are excited/scared/embarrassed

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26
Q

Sympathetic nervous system function

A

Mobilizes the body- constriction of visceral blood vessels, dilates bronchioles of lungs, increases glucose release to blood, pupils dilate, etc.

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27
Q

Where do the fibers of the sympathetic nervous system originate?

A

Thoracolumbar region of spinal cord (T1-L2)
Preganglionic fibers are short, postganglionic fibers are long. Cell bodies of this division form lateral horns of spinal cord

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28
Q

Where are the ganglia of the SNS located?

A

Close to the spinal cord

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29
Q

What areas does the sympathetic nervous system innervate?

A

Innervates smooth muscle, cardiac muscle, and glands in body cavities. It also innervates smooth muscle and glands in superficial regions. Sweat glands, arrector pili, smooth muscle in blood vessel walls

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30
Q

Sympathetic trunk

A

Allows nerve fibers to travel to spinal nerves that are superior and inferior to the one in which they originated. Found on both sides of the spinal cord

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31
Q

What happens to preganglionic fibers when they leave the spinal cord (SNS)?

A

Fibers then pass through white ramus communicans, enter sympathetic trunk ganglion

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32
Q

White ramus communicans

A

White rami communicans carry preganglionic fibers to the sympathetic trunk

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33
Q

Sympathetic trunk ganglion

A

Sympathetic trunk ganglion are like a string of pearls going down both sides of the spinal cord

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34
Q

How can preganglionic and postganglionic fibers can form synapses at the trunk ganglion (3 possibilities)?

A
  1. Preganglionic neuron and postganglionic neuron synapse at the same level.
  2. Preganglionic neuron and postganglionic neuron synapse at a higher or lower level
  3. Preganglionic neuron and postganglionic neuron synapse at a distant collateral ganglion in the abdomen and pelvis
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35
Q

What happens when the preganglionic neuron and postganglionic neuron synapse at the same level?

A

Preganglionic neuron goes straight out through the side of the ventral root to synapse. This is the most simple way to form a synapse

36
Q

What happens when the preganglionic neuron and postganglionic neuron synapse at a higher or lower level?

A

Travels through the spinal nerve and white ramus communicans, travels up or down to a higher or lower ganglion and forms a synapse there.

37
Q

What happens when the preganglionic neuron and postganglionic neuron synapse at a distant collateral ganglion in the abdomen and pelvis?

A

At the sympathetic trunk, the fiber extends straight through the trunk to a distant location

38
Q

Sympathetic pathways with synapses in trunk ganglia

A

If synapse forms in trunk ganglia, postganglionic fibers enter ventral or dorsal ramus of adjoining spinal nerves via gray rami communicans- travel to effectors from here.

39
Q

Gray rami communicans

A

Carry postganglionic fibers from sympathetic trunk ganglion to periphery

40
Q

Superior cervical ganglion function

A

Serves skin and blood vessels of the head, stimulate dilator muscles of eyes, inhibits nasal and salivary glands, innervates muscle to upper eyelid, sends branches to heart

41
Q

Sympathetic pathways to the head

A

Preganglionic fibers emerge from T1-T4, synapse with postganglionic fibers at superior cervical ganglion

42
Q

Sympathetic pathways to the thorax

A

Preganglionic fibers emerge from T1-T6. Most postganglionic axons pass through cardiac, pulmonary, and esophageal plexuses to the effector organ. These plexuses are formed from the parasympathetic division, the sympathetic division is hitching a ride

43
Q

Sympathetic pathways with synapses in the collateral ganglia

A

Preganglionic fibers from T5-L2 synapse in collateral ganglia, form splanchnic nerves.

44
Q

Splanchnic nerves function

A

Serve abdominal viscera. These ganglia usually reach the effector organ by traveling with a blood vessel.

45
Q

Sympathetic pathways to the abdomen

A

Fibers T5-L2 innervate the abdomen. Function- serve the stomach, most of the intestines, liver, spleen, and kidneys

46
Q

Sympathetic pathways to the pelvis

A

Fibers T10-L2 innervate the pelvis. Function- serves the bladder, reproductive organs, and the distal half of the large intestine

47
Q

How does sympathetic innervation effect the abdominopelvic visceral organs?

A

The effect of sympathetic innervation on the abdominopelvic visceral organs is mostly inhibitory. Don’t want to digest things during the fight or flight response

48
Q

5 components of visceral reflex arcs?

A
  1. Receptor in viscera
  2. Sensory neurons
  3. Integration center
  4. Motor neurons
  5. Visceral effector
49
Q

Sensory neurons in visceral reflex arcs

A

These neurons are non-encapsulated nerve endings. Function- send sensory information about changes in chemical composition, stretch, temperature, and irritation of viscera.

50
Q

Motor neurons in visceral reflex arcs

A

These neurons are preganglionic neurons and postganglionic neurons

51
Q

What is the visceral effector in reflex arcs? (3)

A

Smooth muscle, cardiac muscle, and glands

52
Q

How are the brain and spinal cord involved in visceral reflex arcs?

A

The brain and spinal cord aren’t really involved, GI tract is pretty independent.

53
Q

Acetylcholine (ACh)

A

Effect is not entirely excitatory or inhibitory- depends on the receptor it binds. Released by cholinergic fibers at all ANS preganglionic axons and all parasympathetic postganglionic axons at synapse with effector.

54
Q

Cholinergic receptors that bind ACh (2)

A
  1. Nicotinic receptors

2. Muscarinic receptors

55
Q

Nicotinic receptors location

A

Found on all postganglionic neurons (sympathetic and parasympathetic), hormone producing cells of the adrenal medulla, and sarcolemma of skeletal muscle cells (skeletal muscle isn’t really part of the ANS).

56
Q

What is the effect of ACh on nicotinic receptors?

A

Binding of ACh here is always stimulatory

57
Q

Location of muscarinic receptors

A

Found on all parasympathetic effectors and some sympathetic effectors

58
Q

Effect of ACh on muscarinic receptors

A

Binding of ACh here is stimulatory or inhibitory. Binding of ACh to muscarinic receptors of the heart is inhibitory, but binding of ACh to muscarinic receptors of the smooth muscle of the gastrointestinal tract is stimulatory

59
Q

Where is norepinephrine released?

A

Released by adrenergic fibers at sympathetic postganglionic axons

60
Q

Types of adrenergic receptors that bind NE (2)

A
  1. Alpha receptors

2. Beta receptors

61
Q

Alpha receptors

A

Locations- all sympathetic target organs

62
Q

Beta receptors

A

Locations- heart, adipose tissue, kidneys, lungs, blood vessels

63
Q

Effect of NE and epinephrine

A

Binding of NE or epinephrine can be stimulatory or inhibitory. Example- NE binding at beta receptors of the heart increases activity, but epinephrine binding at beta receptors of bronchioles causes dilation

64
Q

Antagonistic interactions of sympathetic and parasympathetic divisions

A

Divisions have opposite effects- whichever dominates will influence overall organ activity. Increased sympathetic activity= increased heart rate, dilated airways, decreased digestion and elimination. Increased parasympathetic activity= resting heart rate and airway diameter, increased elimination and waste.

65
Q

Vasomotor (sympathetic) tone

A

Continuous partial constriction of blood vessels. Sympathetic fibers supply blood vessels and control blood vessels diameter

66
Q

How does blood pressure influence the activity of vasomotor fibers?

A

If blood pressure is low, vasomotor fibers fire more rapidly, so blood vessels constrict to increase blood pressure. If blood pressure is high, vasomotor fibers fire less rapidly, so blood vessels dilate to decrease blood pressure

67
Q

Parasympathetic tone

A

Present mostly in cardiac muscle tissue, smooth muscle tissue of digestive and urinary organs . Effect- slows heart rate, maintains normal activity of digestive and urinary organs. Sympathetic division can override parasympathetic tone, however.

68
Q

Thermoregulatory response to heat

A

This is a unique role of the sympathetic division. In response to heat, blood vessels dilate and sweat glands are activated. Blood vessels will constrict in response to cold, so blood goes internally to warm the organs

69
Q

Renin release from kidneys

A

This is a unique function of the sympathetic division. Renin is a hormone produced by cells in the kidneys that increases blood pressure.

70
Q

How does the sympathetic division change the metabolism? (3)

A
  1. Increases metabolic rate of cells
  2. Raises blood glucose levels- to produce ATP and use skeletal muscle tissue
  3. Mobilizes fats used fuel use
71
Q

How does the parasympathetic division exerts highly localized, short lived control?

A

One preganglionic neuron synapses with one (or a few) postganglionic neurons. In addition, all parasympathetic fibers release ACh- quickly broken down by acetylcholine esterase

72
Q

How does the sympathetic division exert diffuse, long lasting control?

A

Preganglionic neurons synapse with multiple postganglionic neurons Also, NE and epinephrine prolong effects of sympathetic division activation. This is why is takes a while to come down from a stressful/traumatic event.

73
Q

What area of the brain controls the ANS?

A

Hypothalamus

74
Q

Anterior hypothalamic areas

A

Oversee parasympathetic division

75
Q

Posterior hypothalamic areas

A

Oversee sympathetic division

76
Q

What ANS functions does the hypothalamus control?

A

Coordinates heart activity, blood pressure, body temperature, water balance, endocrine activity

77
Q

Why do emotional reactions activate the sympathetic division?

A

The hypothalamus is a part of the limbic system. Therefore, emotional reactions to fear, danger, and stress activate the sympathetic division

78
Q

Hypertension is caused by

A

An overactive sympathetic vasoconstrictor response. This means that the heart must work harder to circulate blood through narrow blood vessels

79
Q

What other health problems can be caused by hypertension?

A

Heart disease, enlarged arteries, and kidney failure. Kidneys filter your blood to produce urine. If you have a high pressure of blood going through the capillaries in the kidneys, it will rip them open and the kidney will lose function

80
Q

How is hypertension treated?

A

Adrenergic receptor blocking drugs and diuretics (reduce blood volume). Adrenergic receptor blockers stop NE from binding from NE receptors at the heart, blocking sympathetic influence and lowering heart rate.

81
Q

Raynaud’s disease is caused by

A

Caused by exaggerated vasoconstriction response due to cold or emotional stress

82
Q

Effects of Raynaud’s disease

A

Effect- skin of fingers and toes becomes pale, skin can eventually become cyanotic and painful. Cyanotic tissue is not dead tissue- restoring blood flow will restore normal function. However, tissue will be black/necrotic if it goes without blood flow for too long. Severity can be minimal or more extreme

83
Q

What group of individuals are affected by autonomic dysreflexia?

A

Affects individuals who are quadriplegic or have spinal cord injuries above T6

84
Q

What causes autonomic dysreflexia?

A

Caused by uncontrolled activation of autonomic neurons. Usually triggered by some type of pain stimulus to the skin or overfilled visceral organ (like the bladder).

85
Q

What is the effect of autonomic dysreflexia?

A

Arterial blood pressure skyrockets to the point that it can become deadly within minutes. Can rupture blood vessels in the brain, causing hemorrhagic stroke. Symptoms- headache, flushed face, sweating above injury, cold/clammy skin below injury.