Autonomic Nervous System

Question 1

Does the autonomic nervous system function inside or outside of our conscious awareness?

Answer 1

Functions outside of our conscious awareness

Question 2

What are the main functions of the autonomic nervous system?

Answer 2

Makes routine adjustments in our body’s systems
- Regulates body temperature
- Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions

Question 3

Compare the somatic and autonomic nervous systems in terms of types of neurons and what is innervated.

Answer 3

Autonomic nervous system
- Has afferent and efferent neurons
- Efferent axons innervate the visceral organs

Somatic nervous system
- Has afferent and efferent neurons
- Efferent axons innervate the skeletal muscles
- Somatic motor neurons do not involve ganglia

Question 4

What is the difference between afferent and efferent?

Answer 4

Afferent- Sensory
Efferent- Motor

Question 5

Where do afferent pathways originate in the autonomic and somatic nervous systems?

Answer 5

Autonomic nervous system
- Afferent pathways originate in visceral sensory receptors

Somatic nervous system
- Afferent pathways originate in the skeletal muscles, joints, and skin

Question 6

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

Answer 6

Sympathetic division and parasympathetic division

Question 7

What is the purpose of the sympathetic division of the ANS?

Answer 7

Fight or flight
- Also called the thoracolumbar division
- Most active during times of exertion, stress, or emergency

Question 8

What is the purpose of the parasympathetic division of the ANS?

Answer 8

Rest and digest
- Also called the craniosacral division
- Most active during resting conditions

Question 9

Which neurotransmitters are secreted at which points. What are the comparative lengths of the preganglionic and postganglionic neurons when comparing sympathetic and parasympathetic pathways.

Answer 9

Sympathetic
o____ ACh O_____________ NE

Parasympathetic
o___________ACh O_____ ACh

For the sympathetic pathway, the preganglionic neuron is short. Acetylcholine is released. The postganglionic neuron is long and norepinephrine is released.

For the parasympathetic pathway, the preganglionic neuron is long. Acetylcholine is released. The postganglionic neuron is short and acetylcholine is released.

Question 10

What is the other name for the sympathetic division of the ANS?

Answer 10

Thoracolumbar division

Question 11

What is the other name for the parasympathetic division of the ANS?

Answer 11

Craniosacral division

Question 12

What is the third division of the autonomic nervous system?

Answer 12

The enteric nervous system (ENS)

Question 13

Where is the ENS (Enteric) located?

Answer 13

Neurons located in the walls of the digestive tract
- Many visceral reflexes are initiated by the ENS, but receive input from the ANS.

Question 14

What does the sympathetic division of the ANS consist of?

Answer 14

• Preganglionic neurons between T1 and L2
  The ganglionic neurons are in three locations:
• Sympathetic chain ganglia
• Collateral ganglia
• Adrenal medulla

Question 15

Which ganglionic neurons are innervated by postganglionic fibers?

Answer 15

Sympathetic chain ganglia and collateral ganglia

Question 16

Which ganglionic neuron is not innervated by postganglionic fibers? What does it do instead?

Answer 16

Adrenal medulla. Releases hormones into bloodstream.

Question 17

What is the purpose of the adrenal medulla?

Answer 17

Releases neurotransmitters
- Epinephrine (E) and norepinephrine (NE)
- Epinephrine is also called adrenaline
- Norepinephrine is also called noradrenaline
The circulating blood distributes these hormones throughout the body

Question 18

What is the relationship of an adrenal gland to a kidney?

Answer 18

Adrenal glands are located on top of each kidney. They are composed of a cortex (outer portion) and medulla (inner portion). The adrenal medulla is where neurotransmitters are released.

Question 19

What are the effects of sympathetic stimulation?

Answer 19

Fight or flight
- Increased alertness
- A feeling of energy and euphoria
- Increased cardiovascular activity
- Increased respiratory activity
- Elevation in muscle tone
- Mobilization of energy reserves

Question 20

What does the parasympathetic division consist of?

Answer 20

• Preganglionic neurons located in the brainstem and in sacral segments of the spinal cord
• Ganglionic neurons located in peripheral ganglia within or adjacent to the target organs

Question 21

What nerves do preganglionic fibers leave the brain in?

Answer 21

N III
N VII
N IX
N X
Sacral parasympathetic outflow
- Preganglionic fibers form distinct pelvic nerves

Question 22

What are the effects of parasympathetic stimulation?

Answer 22

• Constriction of the pupils
• Secretion by digestive glands
• Secretion of hormone promoting nutrient absorption
• Increased smooth muscle activity along the digestive tract
• Stimulation and coordination of defecation
• Contraction of the urinary bladder during urination
• Reduction in heart rate and force of contraction
• Constriction of the respiratory passageways
• Sexual arousal

Question 23

Most vital organs are innervated by both the sympathetic and parasympathetic divisions. What is this known as?

Answer 23

This is known as DUAL INNERVATION.
The two divisions often have opposite, or antagonistic, effects.