Autonomic nervous system | Organ Systems | MCAT | Khan Academy

Summary

This video introduces the autonomic nervous system (ANS), explaining its role in controlling involuntary functions like heart rate, blood flow, and digestion. The ANS consists of two branches: the sympathetic nervous system (SNS), responsible for the 'fight or flight' response, and the parasympathetic nervous system (PNS), responsible for 'rest and digest.' The video explains how these systems work in tandem to regulate bodily functions, with the SNS preparing the body for action and the PNS promoting relaxation and digestion. The video highlights key physiological changes driven by these systems in response to different situations.

Takeaways

• 😀 The autonomic nervous system (ANS) is a functional division of the nervous system, not a structural one, and it controls smooth muscle, cardiac muscle, and gland cells.
• 😀 The ANS operates without conscious involvement, performing autonomously to regulate various body functions.
• 😀 The ANS is divided into two main subsystems: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).
• 😀 The SNS begins in the middle of the spinal cord and has short axons that synapse close to the spine, with longer axons reaching the target cells.
• 😀 The PNS begins in the brain stem or the bottom of the spinal cord and has long axons to synapse with neurons at a distance from the first neuron, followed by short axons to the target cells.
• 😀 The SNS is associated with 'fight or flight' responses, preparing the body for stressful situations by increasing heart rate, redirecting blood flow, and activating sweat glands.
• 😀 The PNS is associated with 'rest and digest' responses, promoting body functions that aid in relaxation, digestion, and energy conservation.
• 😀 In the gastrointestinal system, the SNS decreases blood flow to the intestines during stressful situations, while the PNS increases it during resting states to support digestion.
• 😀 The heart is influenced by both the SNS and PNS; the SNS increases heart output during stress, while the PNS decreases it during rest.
• 😀 The SNS activates sweat glands to help regulate body temperature during stress, whereas the PNS stimulates salivary glands to support digestion during restful states.

Q & A

What is the autonomic nervous system?

The autonomic nervous system (ANS) is a functional division of the nervous system that controls involuntary bodily functions like smooth muscle movement, cardiac muscle contraction, and gland secretion.

How is the autonomic nervous system different from the central and peripheral nervous systems?

Unlike the central and peripheral nervous systems, which are structural divisions, the autonomic nervous system is a functional division, specifically responsible for regulating involuntary functions in the body.

What are the three primary types of cells controlled by the autonomic nervous system?

The autonomic nervous system controls three types of cells: smooth muscle cells, cardiac muscle cells, and gland cells.

What is the difference between autonomic neurons and lower motor neurons?

Autonomic neurons control smooth and cardiac muscle as well as glands, whereas lower motor neurons control skeletal muscle, which moves the body.

What are the two major subsystems of the autonomic nervous system?

The two major subsystems of the autonomic nervous system are the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).

Where do the neurons of the sympathetic nervous system originate?

The first neurons of the sympathetic nervous system originate in the middle part of the spinal cord, and they synapse in ganglia located near the spine.

How does the sympathetic nervous system affect blood flow to the intestines?

When the sympathetic nervous system is activated, blood flow to the intestines decreases as blood is diverted to skeletal muscles to prepare for fight-or-flight responses.

How does the parasympathetic nervous system affect blood flow to the intestines?

When the parasympathetic nervous system is activated, blood flow to the intestines increases to facilitate digestion and the rest-and-digest functions of the body.

What is the primary function of the sympathetic nervous system?

The sympathetic nervous system's primary function is to prepare the body for 'fight or flight' situations by increasing heart rate, blood flow to muscles, and sweat production, while reducing blood flow to non-essential organs like the intestines.

What is the role of the parasympathetic nervous system?

The parasympathetic nervous system promotes 'rest and digest' functions, conserving energy by reducing heart rate, increasing digestion, and maintaining homeostasis in non-threatening situations.