Chapter 18: Autonomic Nervous System Flashcards

1
Q

Describe basic similarities and differences between the somatic nervous system (SNS) and the autonomic nervous system (ANS).

A

Somatic Nervous System (SNS)

  • Voluntary control
  • Uses one motor neuron; therefore faster
  • Myelinated (faster)
  • ACh

Autonomic Nervous System (ANS)

  • Involuntary Control
  • Sympathetic and Parasympathetic Divisions
  • Fight or Flight, Rest and Digest
  • Uses 2 motor neurons (pre- and post-ganglionic neuron), therefore slower
  • Unmyelinated (slower)
  • ACh and norepinephrine (NE)

Both SNS and ANS

  • Part of the PNS
  • Work together to regulate body organs and maintain normal internal functions
  • Use sensory and motor neurons
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2
Q

Discuss the location, structure, and basic function of pre and post ganglionic ANS neurons.

A

Parasympathetic

  • Preganglionic axon: Long
  • Postganglionic axon: Short
  • Preganglionic neuron cell bodies originate in brainstem or lateral gray matter of S2-S4

Sympathetic Division

  • Preganglionic axon: Short
  • Postganglionic axon: Long
  • Preganglionic neuron cell bodies originate in lateral horns of T1-L2
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3
Q

Explain the consequences of neuronal convergence and divergence

A

Convergence:

  • axons from numerous preganglionic cells synapse on a single ganglionic cell
  • “a lot to a little”

Divergence:

  • axons from one preganglionic cell synapse on numerous ganglionic cells
  • “A little to a lot”
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4
Q

List the 2 divisions of the ANS.

A

Parasympathetic Division

Sympathetic Division

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5
Q

Describe the Parasympathetic Division of the ANS.

A
  • “Rest and Digest” Division, “Craniosacral” Division
  • Most active when you are resting or digesting a meal
  • Primarily concerned with conserving energy and replenishing nutrient stores
  • Helps regulate/maintain homeostasis
  • Preganglionic axon: Long
  • Postganglionic axon: Short
  • Preganglionic neuron cell bodies originate in brainstem or lateral gray matter of S2-S4
  • Structurally more simple
  • Ganglionic neurons located close to, or within the walls of, the target organ
  • Lack of divergence prevents mass activation; more discrete and localized
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6
Q

Describe the Sympathetic Division of the ANS.

A
  • “Fight-or-flight” Division, “Thoracolumbar” Division
  • Mass activation; large # of ganglionic neurons activate many effector organs
  • Primarily concerned with preparing body for emergency
  • Increased alertness and metabolic activity; fear
  • Also helps regulate homeostasis
  • Preganglionic axon: Short
  • Postganglionic axon: Long
  • Preganglionic neuron cell bodies originate in lateral horns of T1-L2
  • More complex
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7
Q

Describe the right and left sympathetic trunks.

A
  • Located lateral to the vertebral column on both sides
  • “Chain ganglia”
  • String of pearls appearance
    • Pearls: sympathetic trunk ganglia
    • String: bundles of axons
  • One for each spinal nerve except C-spine only has 3 (superior, middle, and inferior)
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8
Q

Compare and contrast the white rami and the gray rami.

A

White Rami

  • myelinated preganglionic axons
  • “entrance ramps”

Gray Rami

  • unmyelinated axons
  • “exit ramps”
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9
Q

Discuss the structure and function of autonomic plexuses and list examples.

A
  • Collections of sympathetic postganglionic axons and parasympathetic preganglionic axons
  • Close to one another but DO not interact or synapse
  1. Cardiac Plexus
    - Increase sympathetic activity = increase HR, BP, etc
    - Increase parasympathetic activity = decreases HR, etc
  2. Pulmonary Plexus
    - Sympathetic activity = bronchiodilation
    - Parasympathetic activity = bronchioconstriction
  3. Esophageal Plexus
    - Parasympathetic activity = controls swallowing reflex
  4. Abdominal Aortic Plexus
  5. Hypogastric Plexus
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10
Q

List and describe the effects of the principle neurotransmitters in the ANS.

A

2 Neurotransmitters:

  1. Acetylcholine (ACh)
  2. Norepinephrine (NE)

Neurotransmitters:

  • Released by presynaptic cell
  • Bind to specific receptors on postsynaptic cell
  • Either excitatory or inhibitory effect on effector (depending on receptor)
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11
Q

Discuss neurotransmitters. (Which system uses which neurotransmitter?)

A
  • Parasympathetic division: pre and post ganglionic axons release ACh and are called “cholinergic”
  • ALL preganglionic axons release ACh as their neurotransmitter
  • Sympathetic division: Most postganglionic axons release NE and are called “adrenergic”
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12
Q

Discuss ways the ANS maintains homeostasis and describe the hierarchy that controls this system.

A
  • Dual innervation: many organs innervated by postganglionic axons from both ANS divisions and their effects oppose each other
  • Autonomic reflexes: contraction of smooth or cardiac muscle, secretion of glands, alteration of pupil diameter, HR, RR, BP, regulation of digestive activities, etc
  • Controlled by CNS: Cerebrum, hypothalamus, brainstem, spinal cord
  • Sensory processing in thalamus and emotional state in limbic system both effect hypothalamus
  • Hypothalamus: command center for ANS; controls visceral functions in both divisions of the ANS; communicates with other CNS regions; emotions
  • Brainstem: visceral reflexes
  • Spinal cord: ANS reflex center for defecation and urination
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