2. Divisions of the Nervous System

The nervous system is divided into specialized divisions that ____ ____ _____. What are they?

mediate distinct functions

Somatic and autonomic nervous systems

What does the somatic NS contain?

• All the exteroreceptors and voluntary motor neurons

  • circuits that produce all voluntary behavior

  • somatic reflexes by regulating skeletal muscle contractions

What does the autonomic NS include?

• Most interoreceptors and all involuntary effector neurons

  • regulates smooth and cardiac muscles and glands

  • these circuits produce most involuntary behaviors and regulate internal homeostasis

What are the distinct circuits in the autonomic nervous system comprised of?

Sympathetic and parasympathetic subdivisions

What does sympathetic activity promote?

Fight-or-flight responses

What does parasympathetic activity promote?

“Rest-and’digest” responses

Parasympathetic and sympathetic activity are often conceptualized as ?

as controlling two opposing physiological states in organs that receive innervation from both divisions (“dual innervation”)

What are associated with somatic, parasympathetic, and sympathetic output?

Distinct neurotransmitters and receptors

What is the pathway, number of neurons, and neurotransmitters used in the somatic nervous system? Include locations.

Only 1 neuron

• the cell body is in the CNS and the axon travels out of the CNS to the PNS

• the axon terminal will release acetylcholine (ACh) to the skeletal muscle and cause contractions

What is the pathway, number of neurons, and neurotransmitters used in the autonomic nervous system, particularly the parasympathetic system? Include locations.

There are only 2 neurons

• the cell body of the first neuron is in the CNS and the axon travels from the CNS to PNS to release ACh to the second neuron

• the second neuron travels to the smooth/cardiac muscles, glands, or other cells and release ACh

What is the pathway, number of neurons, and neurotransmitters used in the autonomic nervous system, particularly the sympathetic system? Include locations.

There are two neurons

• the first neuron’s cell body is in the CNS and the axon travels out of the CNS to the PNS and releases ACh to the second neuron

• the second neuron is in the PNS and travels to the smooth/cardiac muscles, glands, or other cells and release norepinephrine

  

What is another neurotransmitter that can be used in the autonomic nervous system, particularly the sympathetic division? How is this possible?

Epinephrine, and this is possible because epinephrine and norepinephrine are structually-related, and activate the same family of adrenergic receptors

The enteric division of the autonomic nervous system is largely _____. It is also localized to ____ and regulates ______. It is also very poorly understood

Largely autonomous and is localized to the walls of the gut and regulates gut contractions that move food through the gut during digestion