Neurotransmitters in Autonomic Nervous System
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Questions and Answers

Which of these statements accurately describes the neurotransmitters involved in the autonomic nervous system?

  • All parasympathetic postganglionic neurons release norepinephrine (NE).
  • Chromaffin cells of the suprarenal medullae release only acetylcholine (ACh).
  • All sympathetic and parasympathetic preganglionic neurons release acetylcholine (ACh). (correct)
  • Most sympathetic postganglionic neurons release norepinephrine (NE), while most sweat glands release acetylcholine (ACh). (correct)

    • The autonomic nervous system operates entirely independently of conscious control.

    False (B)

    What is the primary neurotransmitter released by somatic motor neurons?

    Acetylcholine (ACh)

    The autonomic nervous system controls the function of ______ , ______ , and ______ .

    <p>smooth muscle, cardiac muscle, glands</p> Signup and view all the answers

    Match the following terms with their corresponding descriptions:

    <p>Somatic motor neurons = Synapse directly with effector organs Preganglionic neurons = Release acetylcholine (ACh) at the synapse Postganglionic neurons = Relay signals between preganglionic neurons and effector organs Chromaffin cells = Release epinephrine and norepinephrine into the bloodstream</p> Signup and view all the answers

    What is the primary function of beta blockers?

    <p>Reduce blood pressure (C)</p> Signup and view all the answers

    Beta blockers help to narrow veins and arteries to improve blood flow.

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

    What hormone do beta blockers block to lower blood pressure?

    <p>epinephrine</p> Signup and view all the answers

    The two divisions of the autonomic nervous system are the _____ and _____ divisions.

    <p>sympathetic, parasympathetic</p> Signup and view all the answers

    Where are the cell bodies of preganglionic neurons in the sympathetic division located?

    <p>Thoracolumbar spinal cord (C)</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Sympathetic Division = Wide distribution across the body Parasympathetic Division = Limited distribution to specific areas Preganglionic Neurons = Initiate the autonomic response Ganglia = Location of synapse between neurons</p> Signup and view all the answers

    The sympathetic division is also referred to as the craniosacral division.

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

    Name one medication that is classified as a beta blocker.

    <p>propranolol</p> Signup and view all the answers

    Which receptor type is activated by norepinephrine?

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

    Alpha-2 adrenergic receptors lead to vasodilation in blood vessels.

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

    What effect does the activation of alpha-1 receptors have on salivary gland cells?

    <p>Secretion of K+ and water</p> Signup and view all the answers

    Alpha-1 receptors cause __________ of smooth muscle in blood vessels.

    <p>contraction</p> Signup and view all the answers

    Which of the following effects is caused by the activation of alpha-2 adrenergic receptors?

    <p>Inhibition of digestive enzyme secretion (A)</p> Signup and view all the answers

    Adrenergic receptors can be found in smooth muscle fibers and blood vessels.

    <p>True (A)</p> Signup and view all the answers

    Alpha-2 receptors lead to __________ of pancreatic beta cells.

    <p>decreased insulin secretion</p> Signup and view all the answers

    Match the receptor type with its associated effect:

    <p>Alpha-1 = Vasoconstriction Alpha-2 = Decreased insulin secretion Beta-1 = Increased heart rate Beta-2 = Vasodilation</p> Signup and view all the answers

    What neurotransmitter do cholinergic neurons release?

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

    Adrenergic neurons release acetylcholine.

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

    Name the two types of cholinergic receptors.

    <p>Nicotinic and Muscarinic</p> Signup and view all the answers

    Adrenergic neurons release ___________.

    <p>norepinephrine</p> Signup and view all the answers

    Where are nicotinic receptors located? (Select all that apply)

    <p>Postganglionic neurons (B), Skeletal muscle fibers (D)</p> Signup and view all the answers

    Muscarinic receptors can result in both excitation and inhibition.

    <p>True (A)</p> Signup and view all the answers

    What effect do nicotinic receptors have on skeletal muscle fibers?

    <p>Excitation leads to contraction</p> Signup and view all the answers

    Match the receptor type with their major location:

    <p>Nicotinic = Skeletal muscle fibers Muscarinic = Sweat glands</p> Signup and view all the answers

    What type of response is primarily associated with the parasympathetic nervous system?

    <p>Rest-and-digest (C)</p> Signup and view all the answers

    Postganglionic neurons in the sympathetic nervous system primarily release acetylcholine.

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

    What are the axon lengths of preganglionic neurons in the sympathetic nervous system?

    <p>Short axons</p> Signup and view all the answers

    Preganglionic neurons in the parasympathetic nervous system have ______ axons that usually pass to ______ visceral effectors.

    <p>long, four to five</p> Signup and view all the answers

    Which neurotransmitter is primarily released by postganglionic neurons in the parasympathetic nervous system?

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

    The sympathetic nervous system has longer preganglionic axons compared to the parasympathetic nervous system.

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

    What is the primary physiological response associated with the sympathetic nervous system?

    <p>Fight-or-flight</p> Signup and view all the answers

    What is autonomic tone primarily governed by?

    <p>The hypothalamus (A)</p> Signup and view all the answers

    Sympathetic stimulation decreases the rate and strength of the heartbeat.

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

    What acronym describes the responses of the parasympathetic nervous system?

    <p>SLUDD</p> Signup and view all the answers

    The autonomic reflex arc is composed of a receptor, a sensory neuron, an integrating center, ______, and an effector.

    <p>motor neurons</p> Signup and view all the answers

    Which of the following is NOT a response of the sympathetic nervous system?

    <p>Increased digestion (B)</p> Signup and view all the answers

    Match the parasympathetic responses to their effects:

    <p>Salivation = Increased salivation Lacrimation = Tears production Urination = Increased urination frequency Digestion = Enhanced digestion activity Defecation = Facilitated bowel movement</p> Signup and view all the answers

    Raynaud phenomenon results from excessive sympathetic stimulation, causing vasodilation in the digits.

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

    What occurs when there is increased sympathetic input?

    <p>Decreased parasympathetic input</p> Signup and view all the answers

    Study Notes

    Autonomic Nervous System

    • The autonomic nervous system (ANS) is responsible for involuntary functions
    • It has two divisions: sympathetic and parasympathetic
    • The purpose of this chapter is to examine the structure and function of the ANS, compare and contrast the somatic and ANS, examine ANS neurotransmitters and compare and contrast the sympathetic and parasympathetic nervous systems
    • The somatic nervous system includes sensory and motor neurons, it's involved in sensory perceptions and voluntary movements
    • Motor neurons innervate skeletal muscles either excitatory or inhibitory
    • This system is voluntary
    • The autonomic nervous system receives input from sensory receptors located in organs, blood vessels, and muscles
    • The axon of a single, myelinated somatic motor neuron extends from the central nervous system to the skeletal muscle fiber it innervates
    • The ANS usually operates without conscious control, with centers in the hypothalamus and brain stem regulating reflexes
    • Interoceptors are sensory receptors located in blood vessels, visceral organs, and muscles that monitor conditions within the internal environment
    • Examples of interoceptors include chemoreceptors, monitoring blood CO2 levels and mechanoreceptors that detect stretch in organ or blood vessel walls
    • Autonomic motor neurons regulate visceral activities by either increasing or decreasing activities in effector tissues
    • Autonomic responses aren't consciously altered and serve as the basis for polygraph tests
    • Yoga and biofeedback techniques can regulate autonomic function

    Comparison of Somatic and Autonomic Nervous Systems

    • Most autonomic motor pathways consist of two motor neurons in series.
    • A preganglionic neuron has its cell body in the central nervous system and the axon extends to an autonomic ganglion.
    • A postganglionic neuron has its unmyelinated axon extending from the ganglion to the effector.
    • Most body organs have dual ANS innervation, receiving impulses from both sympathetic and parasympathetic neurons.
    • Sympathetic stimulation often leads to a "fight-or-flight" response, increasing alertness and metabolism
    • Parasympathetic stimulation promotes "rest-and-digest" activities, slowing down most body functions
    • There are two types of autonomic ganglia, sympathetic and parasympathetic

    Anatomy of Autonomic Motor Pathways

    • Each division of the autonomic nervous system (ANS) has two motor neurons, preganglionic and postganglionic
    • Preganglionic neurons have their cell bodies in the brain stem or spinal cord, and axons innervate autonomic ganglia
    • Postganglionic neurons have their cell bodies within the ganglia, and axons innervate the effectors (target organs)
    • Sympathetic division neurons have cell bodies in the lateral horns of the gray matter, in T1-L2 spinal cord segments
    • Parasympathetic neurons have cell bodies in nuclei of cranial nerves III, VII, IX, X and lateral gray matter of S2-S4 spinal cord segments.
    • 80% of parasympathetic flow travels through the vagus nerve.
    • Four ways sympathetic preganglionic neurons can connect with postganglionic neurons
    • Major autonomic plexuses in abdomen and pelvis: celiac, superior mesenteric, inferior mesenteric, renal, and hypogastric plexuses; named after the artery through which they are distributed.

    ANS Neurotransmitters and Receptors

    • Autonomic neurons are classified as cholinergic or adrenergic based on the neurotransmitter they release
    • Cholinergic neurons release acetylcholine (ACh), which acts on either nicotinic or muscarinic receptors.
    • Adrenergic neurons release norepinephrine (noradrenaline), which acts on alpha and beta receptors
    • Nicotinic receptors are excitatory and found at synapses between pre- and postganglionic neurons and at the neuromuscular junction.
    • Muscarinic receptors are excitatory or inhibitory, depending on the target tissue and are activated by ACh.
    • Alpha and beta adrenergic receptors can be excitatory or inhibitory, their effects are varied.

    Physiology of the ANS

    • Autonomic tone is the balance between sympathetic and parasympathetic activity and it's regulated by the hypothalamus
    • Sympathetic stimulation leads to secretion of norepinephrine, an increase in heart rate and strength, blood vessel constriction of non-essential organs, and dilation of vessels in essential organs.
    • Parasympathetic stimulation promotes rest and digest/ relaxation. A mnemonic for responses associated with parasympathetic activity is SLUDD (Salivation, Lacrimation, Urination, Digestion, Defecation).

    Integration and Control of Autonomic Functions

    • Functions like heart rate and blood vessel diameter are controlled by autonomic reflexes involving a receptor, sensory neuron, integrating center, motor neuron, and effector.

    Stress Response

    • The stress response involves the activation of the sympathetic nervous system, a complex cascade of hormone releases, and long-term responses for adaptation

    Comparison of Sympathetic and Parasympathetic

    • Sympathetic is "fight-or-flight", and parasympathetic is "rest-and-digest".
    • Key differences such as the length of axons, axon divergence, presence of white and gray communicating rami; the neurotransmitters released at different synapses

    Raynaud Phenomenon

    • Excessive sympathetic stimulation of blood vessels in the extremities, causing vasoconstriction and ischemia, resulting in numbness and color changes (e.g., in the fingers).

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    This quiz explores the key neurotransmitters involved in the autonomic nervous system, including their functions and impacts. Test your knowledge on beta blockers, their mechanisms, and the divisions of the autonomic nervous system. Perfect for students studying physiology or pharmacology.

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