Introduction to Sympathetic Nervous System Functions Quiz

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Questions and Answers

What is another name for the autonomic nervous system (ANS)?

Involuntary nervous system (correct)

Central nervous system

Somatic nervous system

Peripheral nervous system

Where are the cell bodies of preganglionic neurons located?

In the CNS

In the ganglia

In the effector organs

In the brainstem or spinal cord (correct)

What do postganglionic neurons terminate on?

Effector organs (correct)

Spinal cord

Brainstem

Ganglia

Which type of neurons make synaptic connections in ganglia?

Preganglionic neurons Signup and view all the answers

What is the function of ganglia in the autonomic nervous system?

To function as relay stations between preganglionic and postganglionic neurons Signup and view all the answers

Which of the following is under the control of the autonomic nervous system?

Exocrine glands Signup and view all the answers

Which division of the nervous system is involved in maintaining homeostasis within the body?

Parasympathetic division Signup and view all the answers

During which type of situations does the sympathetic nervous system discharge as a complete system?

Severe exercise or reactions to fear Signup and view all the answers

Which hormones are released by the adrenal medulla and directly enter the bloodstream?

Epinephrine and norepinephrine Signup and view all the answers

In which type of situations is the parasympathetic division expected to predominate over the sympathetic nervous system?

"Rest-and-digest" situations Signup and view all the answers

What is the main function of the sympathetic nervous system?

To prepare the body for uncertain situations and unexpected stimuli Signup and view all the answers

How do hormones released by the adrenal medulla affect effector organs?

They enter the bloodstream and promote responses in effector organs with adrenergic receptors Signup and view all the answers

What is the primary characteristic of neurotransmitters that requires them to bind to specific receptors on the cell surface of target organs?

Binding specificity Signup and view all the answers

Which of the following is a common neurotransmitter involved in the actions of therapeutically useful drugs?

Histamine Signup and view all the answers

In chemical signaling between cells, a receptor is best defined as a recognition site for a substance that is coupled to processes leading to:

Binding specificity Signup and view all the answers

Which neurotransmitter is primarily involved in transmitting signals in the autonomic nervous system (ANS)?

Acetylcholine Signup and view all the answers

What distinguishes cholinergic neurons based on the type of neurotransmitter released?

Mediation by acetylcholine Signup and view all the answers

Which family of receptors do chemical signals like acetylcholine and norepinephrine bind to?

Protein receptors Signup and view all the answers

Where do the parasympathetic preganglionic fibers arise from?

Cranial nerves and sacral region of the spinal cord Signup and view all the answers

What neurotransmitter stimulates the adrenal medulla to secrete epinephrine and norepinephrine into the blood?

Acetylcholine Signup and view all the answers

What is the role of the vagus nerve in the parasympathetic system?

Accounts for 90% of preganglionic parasympathetic fibers Signup and view all the answers

In the parasympathetic system, are the preganglionic or postganglionic fibers longer?

Preganglionic fibers Signup and view all the answers

What type of connection exists between preganglionic and postganglionic neurons in the parasympathetic system?

One-to-one connection Signup and view all the answers

Which division of the autonomic nervous system includes the enteric neurons?

Enteric Nervous System Signup and view all the answers

Which division of the nervous system is more circumscribed with mostly one-to-one interactions?

Parasympathetic division Signup and view all the answers

In which nerve supply to the GI tract does one preganglionic neuron interact with 8000 or more postganglionic fibers?

Parasympathetic nerves Signup and view all the answers

Which nervous system innervates skeletal muscles?

Motor nerves Signup and view all the answers

What characteristic leads to the formation of a motor unit in the somatic nervous system?

Myelination of the motor nerves Signup and view all the answers

What enables a fast response by the somatic nervous system?

Myelination of the motor nerves Signup and view all the answers

Which form of neurotransmission is an example of chemical signaling between cells in the autonomic nervous system?

Neurotransmission in the ANS Signup and view all the answers

Which type of receptors are further classified as nicotinic or muscarinic?

Cholinergic receptors Signup and view all the answers

Which receptors are directly linked to membrane ion channels and are known as ionotropic receptors?

Cholinergic nicotinic receptors Signup and view all the answers

Which group of receptors mediate the effects of ligands by activating a second messenger system inside the cell?

Metabotropic receptors Signup and view all the answers

Which systems are the two most widely recognized second messengers in signal transduction?

Adenylyl cyclase and the calcium/phosphatidylinositol system Signup and view all the answers

Which mechanism involves neurotransmitter receptors that are membrane proteins providing a binding site for neurotransmitter molecules?

Affecting ion permeability through ion channels Signup and view all the answers

Which type of receptor is known to affect ion permeability through ion channels?

Ionotropic receptors Signup and view all the answers

Which receptors bind epinephrine and norepinephrine in the ANS effector cells?

Adrenergic receptors Signup and view all the answers

What is the classification of adrenergic or cholinergic receptors based on?

The hormones that bind to them Signup and view all the answers

Study Notes

Parasympathetic Nervous System

If the parasympathetic nervous system were to be activated simultaneously, it would produce massive and undesirable symptoms, such as involuntary urination and defecation.
Parasympathetic fibers innervate specific organs, such as the gut, heart, or eye, and are activated separately, affecting these organs individually.

Role of the CNS in the Control of Autonomic Functions

The autonomic nervous system (ANS) requires sensory input from peripheral structures to provide information on the body's current state.
Feedback is provided by streams of afferent impulses originating in the viscera and other autonomically innervated structures, which travel to integrating centers in the CNS, such as the hypothalamus, medulla oblongata, and spinal cord.
These centers respond to stimuli by sending out efferent reflex impulses via the ANS.

Reflex Arcs

Most afferent impulses are involuntarily translated into reflex responses.
A fall in blood pressure causes pressure-sensitive neurons (baroreceptors in the heart, vena cava, aortic arch, and carotid sinuses) to send fewer impulses to cardiovascular centers in the brain.

Sympathetic Neurons

The adrenal medulla receives preganglionic fibers from the sympathetic system and secretes epinephrine (adrenaline) and norepinephrine directly into the blood in response to stimulation.

Anatomy of the ANS

Parasympathetic preganglionic fibers arise from cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus), as well as from the sacral region (S2 to S4) of the spinal cord.
These fibers synapse in ganglia near or on the effector organs.
The vagus nerve accounts for 90% of preganglionic parasympathetic fibers and innervates most organs in the thoracic and abdominal cavity.

Enteric Neurons

The enteric nervous system is the third division of the ANS.

Sympathetic Innervation

Some effector organs, such as the adrenal medulla, kidney, pilomotor muscles, and sweat glands, receive innervation only from the sympathetic system.

Somatic Nervous System

The efferent somatic nervous system differs from the ANS in that a single myelinated motor neuron, originating in the CNS, travels directly to skeletal muscle without the mediation of ganglia.
The somatic nervous system is under voluntary control, whereas the ANS is involuntary.
Responses in the somatic division are generally faster than those in the ANS.

Summary of Differences Between Sympathetic, Parasympathetic, and Motor Nerves

Major differences in the anatomical arrangement of neurons lead to variations of functions in each division.
The sympathetic nervous system is widely distributed, innervating practically all effector systems in the body.
The parasympathetic division is more limited in its distribution.

Membrane Receptors

All neurotransmitters, and most hormones and local mediators, are too hydrophilic to penetrate the lipid bilayers of target cell plasma membranes.
Instead, their signal is mediated by binding to specific receptors on the cell surface of target organs.

Neurotransmitters

There are over 50 signal molecules in the nervous system, but norepinephrine (and epinephrine), acetylcholine, dopamine, serotonin, histamine, glutamate, and γ-aminobutyric acid are most commonly involved in the actions of therapeutically useful drugs.
Each of these chemical signals binds to a specific family of receptors.
Acetylcholine and norepinephrine are the primary chemical signals in the ANS, whereas a wide variety of neurotransmitters function in the CNS.

Acetylcholine

Autonomic nerve fibers can be divided into two groups based on the type of neurotransmitter released.
If transmission is mediated by acetylcholine, the neuron is termed cholinergic.

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Description

Test your knowledge on the functions of the sympathetic nervous system, including the fight or flight response triggered by direct sympathetic activation and adrenal medulla stimulation. Explore how hormones released by the adrenal medulla impact effector organs with adrenergic receptors.