Autonomic Nervous System (ANS) and Sympathetic Nervous System (SNS)

Autonomic Nervous System (ANS)

• The autonomic nervous system is a functional division of the nervous system, not a structural division.
• It consists of efferent neurons in the peripheral nervous system that control three types of cells:
  • Smooth muscle cells
  • Cardiac muscle cells
  • Gland cells
• The ANS is called "autonomic" because it controls these functions without conscious involvement.

Sympathetic Nervous System (SNS)

• The SNS is one of the two big subsystems of the ANS.
• It starts in the middle of the spinal cord.
• The first neuron in the SNS sends a short axon to synapse with a second neuron in a ganglia close to the spine.
• The second neuron then sends a longer axon to reach its target cell.
• The SNS is responsible for the "fight or flight" response, preparing the body to deal with threatening or dangerous situations.

Parasympathetic Nervous System (PNS)

• The PNS is the other big subsystem of the ANS.
• It starts in the brain stem or the bottom of the spinal cord.
• The first neuron in the PNS sends a long axon to synapse with a second neuron in a ganglia at a distance from the first neuron.
• The second neuron then sends a shorter axon to reach its target cell.
• The PNS is responsible for the "rest and digest" response, promoting homeostasis and maintenance of the body in non-threatening situations.

Functional Differences

• The SNS increases blood flow to skeletal muscle, decreases blood flow to the intestines, and increases heart output.
• The PNS increases blood flow to the intestines, decreases blood flow to skeletal muscle, and decreases heart output.
• The SNS activates sweat glands to secrete sweat, whereas the PNS activates salivary glands to produce saliva.

Key Concepts

• The ANS affects many structures and has many functions beyond what is covered in this introductory video.
• It is best to cover the ANS as you're studying each individual organ system, as it plays a role in many different bodily functions.

Autonomic Nervous System (ANS)

• Divided into functional, not structural, parts of the nervous system
• Controls smooth muscle cells, cardiac muscle cells, and gland cells through efferent neurons in the peripheral nervous system
• Functions without conscious involvement, hence "autonomic"

Sympathetic Nervous System (SNS)

• One of the two main subsystems of the ANS
• Originates in the middle of the spinal cord
• Neurons synapse in ganglia close to the spine, and then reach target cells
• Responsible for the "fight or flight" response, preparing the body for threatening situations

Parasympathetic Nervous System (PNS)

• The other main subsystem of the ANS
• Originates in the brain stem or lower spinal cord
• Neurons synapse in ganglia at a distance, and then reach target cells
• Responsible for the "rest and digest" response, promoting homeostasis and maintenance

Functional Differences

• SNS increases blood flow to skeletal muscle, decreases blood flow to intestines, and increases heart output
• PNS increases blood flow to intestines, decreases blood flow to skeletal muscle, and decreases heart output
• SNS triggers sweat glands, while PNS triggers salivary glands

Key Concepts

• ANS affects many structures and has various functions beyond the introductory material
• Study ANS in context with individual organ systems, as it plays a role in multiple bodily functions

Autonomic Nervous System (ANS)

• Divided into functional, not structural, parts of the nervous system
• Controls smooth muscle cells, cardiac muscle cells, and gland cells through efferent neurons in the peripheral nervous system
• Functions without conscious involvement, hence "autonomic"

Sympathetic Nervous System (SNS)

• One of the two main subsystems of the ANS
• Originates in the middle of the spinal cord
• Neurons synapse in ganglia close to the spine, and then reach target cells
• Responsible for the "fight or flight" response, preparing the body for threatening situations

Parasympathetic Nervous System (PNS)

• The other main subsystem of the ANS
• Originates in the brain stem or lower spinal cord
• Neurons synapse in ganglia at a distance, and then reach target cells
• Responsible for the "rest and digest" response, promoting homeostasis and maintenance

Functional Differences

• SNS increases blood flow to skeletal muscle, decreases blood flow to intestines, and increases heart output
• PNS increases blood flow to intestines, decreases blood flow to skeletal muscle, and decreases heart output
• SNS triggers sweat glands, while PNS triggers salivary glands

Key Concepts

• ANS affects many structures and has various functions beyond the introductory material
• Study ANS in context with individual organ systems, as it plays a role in multiple bodily functions

Autonomic Nervous System (ANS)

• Divided into functional, not structural, parts of the nervous system
• Controls smooth muscle cells, cardiac muscle cells, and gland cells through efferent neurons in the peripheral nervous system
• Functions without conscious involvement, hence "autonomic"

Sympathetic Nervous System (SNS)

• One of the two main subsystems of the ANS
• Originates in the middle of the spinal cord
• Neurons synapse in ganglia close to the spine, and then reach target cells
• Responsible for the "fight or flight" response, preparing the body for threatening situations

Parasympathetic Nervous System (PNS)

• The other main subsystem of the ANS
• Originates in the brain stem or lower spinal cord
• Neurons synapse in ganglia at a distance, and then reach target cells
• Responsible for the "rest and digest" response, promoting homeostasis and maintenance

Functional Differences

• SNS increases blood flow to skeletal muscle, decreases blood flow to intestines, and increases heart output
• PNS increases blood flow to intestines, decreases blood flow to skeletal muscle, and decreases heart output
• SNS triggers sweat glands, while PNS triggers salivary glands

Key Concepts

• ANS affects many structures and has various functions beyond the introductory material
• Study ANS in context with individual organ systems, as it plays a role in multiple bodily functions

Understand the autonomic nervous system and its subdivision, the sympathetic nervous system, including their functions and control over muscle cells and glands.