Autonomic Nervous System Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What distinguishes the anatomical origin of the parasympathetic nervous system?

Originates from the sacral and coccygeal regions

Originates from the thoracic and lumbar regions

Originates from cranial and sacral regions (correct)

Has its origins mainly in the cervical spine

Where do the sympathetic ganglia primarily reside?

Within the thoracic cavity

Alongside cranial nerves

Near the abdominal organs

Close to the spinal cord (correct)

Which of the following regions significantly regulates autonomic nervous system activity?

Cerebellum and limbic system

Hypothalamus and brainstem (correct)

Cortex and basal ganglia

Medulla and thalamus

What is one key feature of both the somatic and autonomic nervous systems?

Both systems are tonically active Signup and view all the answers

Which type of neurons connect the central nervous system to the autonomic ganglia?

Preganglionic neurons Signup and view all the answers

What is the primary role of the sympathetic nervous system during emergency situations?

To prepare the body for physical activity Signup and view all the answers

Which of the following describes dual innervation?

Innervation of organs by both sympathetic and parasympathetic fibers Signup and view all the answers

What is the effect of sympathetic stimulation on heart rate?

It increases heart rate Signup and view all the answers

During resting conditions, what is the dominant effect of the parasympathetic nervous system?

Energy conservation and regulation of basic functions Signup and view all the answers

Which organ is exclusively innervated by sympathetic nerve fibers?

Blood vessels Signup and view all the answers

What happens during sympathetic dominance of an organ?

Increased sympathetic nerve activity Signup and view all the answers

How do sympathetic and parasympathetic systems generally interact in terms of organ function?

They exert opposite effects in most organs Signup and view all the answers

What term describes the ongoing partial activity of both the sympathetic and parasympathetic nervous systems?

Tone Signup and view all the answers

Which of the following statements about sweat glands is true?

They are only innervated by sympathetic nerves Signup and view all the answers

What is the overall effect of parasympathetic activity on the digestive tract?

It enhances digestive motility Signup and view all the answers

Study Notes

Autonomic Nervous System Overview

A two-neuron system connects the central nervous system (CNS) to effector cells
The first neuron starts in the CNS
The synapse between neurons occurs outside the CNS, in a ganglion
Neurons connecting the CNS to the ganglia are preganglionic neurons
Neurons connecting ganglia to effector cells are postganglionic neurons
The autonomic nervous system (ANS) is made up of two major divisions: sympathetic and parasympathetic

General Organization of Efferent Divisions

The somatic nervous system uses a single neuron to connect to skeletal muscle.
The autonomic nervous system uses two neurons to innervate smooth or cardiac muscle, glands, or GI neurons.

General Organization of the Autonomic Nervous System

The ANS uses two neurons in series to connect the CNS to effector cells
The first neuron in the pathway begins within the central nervous system.
The synapse occurs outside the central nervous system in a cluster of nerve cells called an autonomic ganglion. The second neuron starts in this cluster (ganglion).
The neurons leading from the CNS to the ganglion are called preganglionic neurons, and the neurons leading out of the ganglion to the effector cells are called postganglionic neurons

Location of Ganglia

Sympathetic ganglia are located near the spinal cord, forming chains on either side
Collateral ganglia (e.g., celiac, superior mesenteric, inferior mesenteric) are located in the abdominal cavity, closer to target organs.
Parasympathetic ganglia are located within or very close to target organs

Regulation of Autonomic Nervous System Activity

The autonomic nervous system activity is controlled by the hypothalamus and brainstem.
Many variables, such as heart rate, blood pressure, gastrointestinal activity, body temperature, hunger, thirst, plasma volume, and plasma osmolarity, are monitored and regulated.

Two Important Features of Both Systems

Most tissues receive dual innervation from both sympathetic and parasympathetic systems.
Both systems are tonically active, meaning they exert some ongoing activity on tissues.
- An example of a tissue receiving only sympathetic innervation are blood vessels.
- Sweat glands are another example of a tissue receiving only sympathetic innervation.

Each System is Dominant Under Certain Conditions

Sympathetic: Active during exercise, fight or flight situations, emergency reactions. Prepares the body for strenuous activity (e.g., increased blood flow to muscles).
Parasympathetic: Active during quiet, resting conditions. Conserves energy and regulates basic body functions like digestion and urination.

Functions of the ANS

The sympathetic and parasympathetic systems innervate most visceral organs (through dual innervation).
The two systems often have opposing effects on the same organ (e.g., sympathetic increases heart rate, parasympathetic decreases).

Exceptions

Innervated blood vessels receive only sympathetic nerve fibers.
Sweat glands receive only sympathetic nerve fibers.
Salivary glands are innervated by both divisions but responses are not antagonistic and depend on which division is more dominant.

Neurotransmitters

Acetylcholine (ACh): Released at all preganglionic neurons in both sympathetic and parasympathetic divisions, all parasympathetic postganglionic neurons, and some sympathetic postganglionic neurons (to sweat glands).
Norepinephrine (NE): Primary neurotransmitter of postganglionic sympathetic neurons.
Epinephrine (Epi): Released by the adrenal medulla in response to stimulation by sympathetic fibers; plays an important role in fight or flight responses

Receptors

Cholinergic receptors: Respond to acetylcholine. Nicotinic receptors and muscarinic receptors.
Adrenergic receptors: Respond to norepinephrine and epinephrine. Alpha and beta subtypes (alpha 1, 2, beta 1, 2)

Drugs Acting on the Sympathetic and Parasympathetic Systems

Sympathomimetics and sympatholytics: Drugs influencing sympathetic function.
Parasympathomimetics and parasympatholytics: Drugs influencing parasympathetic function. Some examples are given.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Dive into the autonomic nervous system (ANS) and understand its organization, including the roles of preganglionic and postganglionic neurons. This quiz covers the two major divisions of the ANS: sympathetic and parasympathetic, and compares it to the somatic nervous system. Test your knowledge on how these systems interact with various effector cells.