Autonomic Nervous System Explained

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Questions and Answers

Which of the following is a characteristic of the autonomic nervous system (ANS)?

  • It primarily uses sensory neurons to relay information.
  • It sends impulses to cardiac muscle, smooth muscle, and glands. (correct)
  • It directly controls skeletal muscle movement.
  • It is under voluntary control.

The 'fight or flight' response is primarily associated with which division of the autonomic nervous system?

  • Somatic nervous system
  • Sympathetic division (correct)
  • Parasympathetic division
  • Sensory division

Which of the following best describes the function of the parasympathetic division of the autonomic nervous system?

  • Increasing heart rate during emergencies
  • Dilating pupils to improve vision
  • Conserving energy and promoting 'rest and digest' functions (correct)
  • Mobilizing energy stores during exercise

Which of the following is true regarding the efferent pathway of the somatic nervous system compared to the autonomic nervous system?

<p>The somatic nervous system has one motor neuron extending to the effector, while the autonomic uses two motor neurons synapsing at a ganglion. (D)</p> Signup and view all the answers

Which neurotransmitter is exclusively used in the somatic nervous system?

<p>Acetylcholine (ACh) (B)</p> Signup and view all the answers

Where do the preganglionic neurons of the parasympathetic division originate?

<p>Brainstem and sacral region of the spinal cord (D)</p> Signup and view all the answers

In the sympathetic division, where are the preganglionic neurons located?

<p>Thoracic and lumbar spinal cord (B)</p> Signup and view all the answers

Which anatomical feature distinguishes the parasympathetic division from the sympathetic division?

<p>Longer preganglionic fibers and shorter postganglionic fibers (D)</p> Signup and view all the answers

The sympathetic trunk is primarily involved in which function?

<p>Serving as a location for sympathetic division synapsing (B)</p> Signup and view all the answers

Which of the following describes the effect of the parasympathetic division on heart rate?

<p>Decreases heart rate (A)</p> Signup and view all the answers

What effect does the sympathetic division have on the pupils?

<p>Dilates pupils (C)</p> Signup and view all the answers

Which neurotransmitter is released by postganglionic fibers of the sympathetic division?

<p>Norepinephrine (NE) (D)</p> Signup and view all the answers

What type of receptor binds acetylcholine released by postganglionic fibers in the parasympathetic division?

<p>Muscarinic receptors (D)</p> Signup and view all the answers

Which of the following is primarily innervated by the sympathetic nervous system?

<p>Sweat glands (B)</p> Signup and view all the answers

If a person is experiencing increased heart rate and bronchodilation, which division of the autonomic nervous system is likely activated?

<p>Sympathetic division (C)</p> Signup and view all the answers

In the autonomic nervous system, which type of receptors are found on all postganglionic neurons?

<p>Nicotinic receptors (B)</p> Signup and view all the answers

What is the primary function of adrenergic receptors?

<p>Binding norepinephrine in the sympathetic system (C)</p> Signup and view all the answers

Which of the following actions is associated with the α (alpha) adrenergic receptors?

<p>Vasoconstriction in blood vessels serving the viscera (B)</p> Signup and view all the answers

What is the effect of activating beta (β) adrenergic receptors in the heart?

<p>Increased heart rate (D)</p> Signup and view all the answers

Which of the following best describes why the sympathetic division can have body-wide effects?

<p>Preganglionic axons have many branches and extensive divergence (D)</p> Signup and view all the answers

Flashcards

Autonomic Nervous System (ANS)

Part of the peripheral nervous system that controls involuntary functions, sending motor impulses to organs and glands.

Sympathetic Division

The division of the ANS responsible for the "fight or flight" response and mobilizing body systems during activity.

Parasympathetic Division

The division of the ANS that conserves energy and promotes housekeeping functions during rest; "rest and digest".

Efferent Pathway

In Somatic nervous system, it's a single motor neuron extending from the CNS to skeletal muscle; in Autonomic, it involves two neurons synapsing at an autonomic ganglion.

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Autonomic Neurotransmitters

Preganglionic fibers release Acetylcholine (ACh); postganglionic fibers release ACh (parasympathetic) or Norepinephrine (NE, sympathetic).

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Sympathetic Trunk

Paired chains of ganglia located laterally on either side of the spinal cord, serving as a location for sympathetic division synapsing.

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Parasympathetic Division

Division of the ANS promoting rest and digest responses. Nerves arise from the brain and sacral spinal cord.

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Sympathetic Division

Division of the ANS promoting fight or flight responses. Nerves arise from the thoracic and lumbar regions of the spinal cord.

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Effects of Sympathetic Division

Causes pupil dilation, increases heart rate & blood pressure, and decreases activity of digestive organs & glands.

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Parasympathetic Effects

Slows heart rate, constricts pupils, increases activity of digestive organs/glands, constricts lung air passages.

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Parasympathetic Anatomy

Arise from the brain and sacral spinal cord, synapsing occurs at autonomic ganglia in or near the effector, very short postganglionic fibers.

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Sympathetic Anatomy

Short preganglionic fibers that arise from thoracic and lumbar spinal cord, synapsing at autonomic ganglia in the sympathetic trunk.

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Acetylcholine (ACh)

Secreted by cholinergic fibers (all somatic, preganglionic ANS fibers, postganglionic parasympathetic fibers).

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Cholinergic Receptors

Found in the autonomic ganglia and on organs with parasympathetic innervation.

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Norepinephrine

Secrete by adrenergic fibers (all postganglionic sympathetic fibers). Adrenergic receptors are on organs with sympathetic innervation.

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Adrenergic Receptors

On organs with sympathetic innervation. Alpha causes constriction and Beta is found in the heart and vessels.

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Somatic Efferent Pathway

One neuron extends from CNS to effector.

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Origin of Parasympathetic Neurons

Located in brainstem nuclei and S2-S4 segments of the spinal cord.

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Origin of Sympathetic Neurons

Located in lateral horns of T1-L2 segments of the spinal cord.

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Sensory Input, Somatic Nervous System

Special senses, skin, proprioceptors.

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Study Notes

  • The autonomic nervous system (ANS) sends motor impulses to organs and glands.

Divisions of the ANS

  • Sympathetic division initiates the "fight or flight" response
  • Parasympathetic division controls the "rest and digest" response

Effectors

  • Somatic nervous system targets skeletal muscle
  • Autonomic nervous system targets smooth and cardiac muscle, and glands

Efferent Pathway

  • Somatic nervous system uses one motor neuron to reach the effector
  • Autonomic nervous system uses two motor neurons synapsing at an autonomic ganglion

Neurotransmitters

  • Somatic nervous system exclusively uses acetylcholine (ACh)
  • Autonomic nervous system preganglionic fibers secrete ACh, postganglionic fibers secrete ACh (parasympathetic) or norepinephrine (NE) (sympathetic)

Parasympathetic Division

  • Promotes "rest and digest" functions
  • Nerves originate from the brain and sacral region of the spinal cord
  • Preganglionic fibers are longer than postganglionic fibers

Sympathetic Division

  • Promotes the "fight or flight" response
  • Nerves originate from the thoracic and lumbar regions of the spinal cord
  • Postganglionic fibers are longer than preganglionic fibers

The Parasympathetic Division Anatomy

  • Long preganglionic fibers originate from the brain and sacral spinal cord
  • Synapses occur at autonomic ganglia located in or near the effector organs
  • Very short postganglionic fibers then innervate the target organ/gland

The Parasympathetic Division Effects

  • Decreases heart rate
  • Constricts pupils
  • Increases actvitiy of digestive organs and glands
  • Constricts air passages in the lungs

Sympathetic Division Anatomy

  • Short preganglionic fibers originate from the thoracic and lumbar spinal cord
  • Synapses occur at autonomic ganglia located in the sympathetic trunk
  • Long postganglionic fibers then innervate the target organ/gland

Sympathetic Division Effects

  • Increases heart rate and blood pressure
  • Dilates pupils
  • Decreases activity of digestive organs and glands
  • Dilates air passages in the lungs

Sympathetic Trunk

  • Consists of paired chains of ganglia located laterally on either side of the spinal cord
  • Location of sympathetic division synapsing
  • Nerve impulses may ascend or descend within the trunk before synapsing

Neurotransmitters and Receptors: Acetylcholine

  • Secreted by cholinergic fibers (all somatic fibers, all preganglionic ANS fibers, all postganglionic parasympathetic fibers).
  • Cholinergic receptors are in autonomic ganglia and on organs with parasympathetic innervation; these are nicoticic and muscarinic

Nicotinic

  • Found at the neuromuscular junction (NMJ) and autonomic ganglia

Muscarinic

  • Found at organs under parasympathetic innervation

Neurotransmitters and Receptors: Norepinephrine

  • Secreted by adrenergic fibers (all postganglionic sympathetic fibers).
  • Adrenergic receptors are on organs with sympathetic innervation, with two types

Alpha

  • Found in blood vessels serving viscera; cause constriction

Beta

  • Found in the heart (increasing rate) and blood vessels serving lungs and skeletal muscles (causing dilation)

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