Podcast
Questions and Answers
Which part of the hypothalamus primarily controls the parasympathetic nervous system?
Which part of the hypothalamus primarily controls the parasympathetic nervous system?
The adrenal medulla is primarily involved in the control of the somatic nervous system.
The adrenal medulla is primarily involved in the control of the somatic nervous system.
False
What type of muscles does the autonomic nervous system control?
What type of muscles does the autonomic nervous system control?
Smooth and cardiac muscles
In the sympathetic nervous system, the preganglionic neuron arises from the ________ segments of the spinal cord.
In the sympathetic nervous system, the preganglionic neuron arises from the ________ segments of the spinal cord.
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Match the following components with their correct characteristics:
Match the following components with their correct characteristics:
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What is the primary function of the sympathetic nervous system during stress?
What is the primary function of the sympathetic nervous system during stress?
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The postganglionic fibers of the sympathetic nervous system are shorter than preganglionic fibers.
The postganglionic fibers of the sympathetic nervous system are shorter than preganglionic fibers.
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What do we call the nerve exit locations of the parasympathetic nervous system?
What do we call the nerve exit locations of the parasympathetic nervous system?
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In the sympathetic nervous system, the divergence ratio of preganglionic to postganglionic fibers is _____ .
In the sympathetic nervous system, the divergence ratio of preganglionic to postganglionic fibers is _____ .
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Match the following aspects of the parasympathetic and sympathetic nervous systems:
Match the following aspects of the parasympathetic and sympathetic nervous systems:
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Study Notes
Autonomic Nervous System (ANS) Introduction
- The ANS controls involuntary functions, impacting smooth and cardiac muscles and visceral organs.
- It comprises two main divisions: sympathetic and parasympathetic, each with distinct functions and pathways.
- The Hypothalamus and Cingulate Gyrus play crucial roles in regulating the ANS, and both are influenced by other parts of the brain and spinal cord.
- Posterior hypothalamus controls sympathetic nerves, while anterior hypothalamus controls parasympathetic nerves.
Objectives
- Students should understand the arrangement and higher control centers of the sympathetic and parasympathetic systems.
- They should know how these systems affect different body organs.
- Critical neurotransmitters (acetylcholine, norepinephrine, and epinephrine) and their secretion sites should be identified.
- Students should be familiar with the adrenal medulla's role and the working of adrenergic and cholinergic receptors.
ANS Anatomy and Functioning
- The ANS employs a two-neuron chain: a preganglionic fiber whose cell body is inside the CNS and a postganglionic fiber whose cell body is located outside the CNS in a ganglion.
- Preganglionic fibers are myelinated, while postganglionic fibers are not.
- Sympathetic division has preganglionic fibers originating from the thoracic and lumbar regions (thoracolumbar outflow)
- Parasympathetic division has preganglionic fibers originating from the brain (cranial nerves) and sacral regions (craniosacral outflow).
Neurotransmitters
- Acetylcholine (ACh) is released by all preganglionic neurons and most postganglionic parasympathetic neurons.
- Some postganglionic sympathetic neurons (e.g., those innervating sweat glands) also release ACh.
- The majority of postganglionic sympathetic neurons release norepinephrine (NE), while the adrenal medulla releases predominantly epinephrine (E).
Autonomic Receptor Effects
- Sympathetic stimulation often leads to fight-or-flight responses, involving increased heart rate, blood pressure, and metabolic rate.
- Parasympathetic stimulation promotes rest-and-digest functions, such as decreased heart rate, increased gut motility, and glucose uptake.
Specific Organ Effects
- Detailed tables illustrate the effects of sympathetic and parasympathetic stimulation on various organs (pupils, heart, blood vessels, lungs, glands, bladder, blood sugar, GIT, blood vessels, etc)
Adrenal Medulla
- The adrenal medulla is an integral part of the sympathetic nervous system, releasing epinephrine (80%) and norepinephrine (20%) into the bloodstream.
- Postganglionic sympathetic neurons can't produce epinephrine; the adrenal medulla synthesizes it.
Receptors
-
Adrenergic receptors (for norepinephrine and epinephrine): Alpha (a) and Beta (β) subtypes.
- Alpha receptors typically cause constriction, beta receptors typically cause dilation.
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Cholinergic receptors: Nicotinic and muscarinic subtypes.
- Found in various locations throughout the body; mediate responses in both sympathetic and parasympathetic divisions.
Cholinergic Receptors
- These receptors respond to acetylcholine
- Nicotinic receptors are found in all autonomic ganglia
- Muscarinic receptors are found on the effector cells of the parasympathetic division and some sympathetic postganglionic neurons (e.g., those innervating sweat glands).
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Description
This quiz provides an overview of the Autonomic Nervous System (ANS), highlighting its role in controlling involuntary bodily functions. Explore the sympathetic and parasympathetic divisions, their functions, and the critical neurotransmitters involved. Test your understanding of the higher control centers and their impact on various organs in the body.
