Autonomic Nervous Syetem

Question 1

What is the general function of the autonomic nervous system?

Answer 1

The autonomic nervous system (ANS) regulates the activities of cardiac muscle, smooth muscle, and glands.

Question 2

Visceral afferent (sensory) neurons

Answer 2

– provide a continual flow of information to

the CNS from the viscera and blood vessels

Question 3

Visceral efferent (motor) neurons

Answer 3

provide motor innervation to the various

effectors (cardiac muscle, smooth muscle, glands

Question 4

How does the ANS operate? What controls it?

Answer 4

The ANS operates without conscious control, relying upon reflex arcs that are dependent upon the hypothalamus and medulla for overriding control.

Question 5

somatic receptors

Answer 5

cutaneous receptors
proprioceptors
special senses

Question 6

is the somatic nervous system concious

Answer 6

may become conscious

Question 7

is the somatic N.S excitatory or inhibitory

Answer 7

excitatory for skeletal muscles only

Question 8

how many motor neurons are in somatic nervous system

Answer 8

single motor neuron

Question 9

what are the receptor types for the autonomic system

Answer 9

chemoreceptors
baroreceptors
mechanoreceptors

Question 10

Is the autonomic system conscious?

Answer 10

unconscious

Question 11

is the Autonomic nervous system excitatory or inhibitory?

Answer 11

excitatory or inhibitory for cardiac muscle, smooth, and glands

Question 12

number of motor neurons for autonomic nervous system

Answer 12

two motor neurons

Question 13

Name the two separate divisions of the ANS.

Answer 13

sympathetic and parasympathetic nervous systems

Question 14

What is meant by the concept of dual innervation?

Answer 14

In general, if one division starts or increases the activity of an organ, the
other division will stop or decrease the activity. This is called dual innervation

Question 15

Name the two types of visceral motor neurons by the divisions of the ANS?

Answer 15

preganglionic and postganglionic

Question 16

Where is the cell body of a preganglionic neuron located?

Answer 16

The cell body is located in gray matter of the spinal cord or brain.

Question 17

How does the axon of a preganglionic neuron pass from the CNS?

Answer 17

The preganglionic axon passes from the CNS in a spinal or a cranial nerve

Question 18

Where does the preganglionic axon terminate?

Answer 18

The preganglionic axon terminates in a ganglion

Question 19

What is a ganglion?

Answer 19

A ganglion is a collection of nerve cell bodies located in a specific site within the body, but outside the CNS

Question 20

Where is the cell body of a postganglionic neuron located?

Answer 20

The cell body is located in a specific ganglion. The location of the ganglion is dependent upon the division of the ANS to which the neuron belongs and which organ it will innervate

Question 21

Where does the axon of the postganglionic neuron terminate?

Answer 21

The postganglionic axon passes from the ganglion to the effector

Question 22

What effect does the postganglionic neuron have on the effector?

Answer 22

The peripheral effector (cardiac muscle, smooth muscle, or gland) is either stimulated or inhibited, depending upon which division of the ANS is being discussed

Question 23

What is the origin of the sympathetic division?

Answer 23

Sympathetic preganglionic neurons originate from the lateral gray horns of spinal cord segments T1-L2. Their axons travel in the spinal nerves of these segments. Therefore, the sympathetic division is called the thoracolumbar division and the preganglionic axons are called the thoracolumbar outflow.

Question 24

What is the origin of the parasympathetic system?

Answer 24

Parasympathetic preganglionic neurons arise from the nuclei of cranial nerves III, VII, IX, and X, and the lateral gray horns of spinal cord segments S2-4. For this reason, the parasym-pathetic division is also called the craniosacral division and the preganglionic axons are the craniosacral outflow.

Question 25

Sympathetic chain ganglia

Answer 25

Sympathetic chain (vertebral 
chain or paravertebral) ganglia are located in a series that lie in a vertical row on either side of the vertebral column, extending from the base of the skull to the coccyx.

Question 26

Prevertebral ganglia

Answer 26

Prevertebral (collateral) ganglia lie as
three clusters associated with the three unpaired arteries arising from the abdominal aorta (celiac, superior mesenteric, and inferior mesenteric). These ganglia are used by the sympathetic division.

Question 27

Terminal ganglia

Answer 27

The parasympathetic division uses

terminal (intramural) ganglia located very close to or within the walls of the organ to be innervated

Question 28

Relative length of fibers

Answer 28

Because of the closeness of the
spinal cord to the sympathetic chain ganglia and the collateral ganglia, sympathetic preganglionic neurons are fairly short. Because of the distance between the brain or spinal cord and the innervated organs, parasympathetic preganglionic fibers are relatively long.

Question 29

Describe the postganglionic neurons of the two systems.

Answer 29

Because of the locations of ganglia, sympathetic postganglionic fibers are relatively long while parasympathetic postganglionic fibers are relatively short. Regardless, all postganglionic neurons of either system have their axons pass from their respective ganglia to the effector for innervation.

Question 30

Most effectors receive innervation from both divisions of the ANS, one causing excitation and the other causing inhibition. How is this possible?

Answer 30

This is possible because the postganglionic neurons use different neurotransmitters and the effectors bear different receptors.

Question 31

What is the ultimate controller of autonomic tone?

Answer 31

The hypothalamus regulates the balance of sympathetic versus parasympathetic activity or tone.

Question 32

Which ANS division is usually in control of autonomic tone

Answer 32

In general, we are in parasympathetic tone, except during states of emergency when we immediately switch to sympathetic tone

Question 33

Cholinergic neurtransmitters

Answer 33

acetylcholine

Question 34

adrenergic neurotransmitters

Answer 34

norepinephrine

Question 35

Which neurons use acetylcholine

Answer 35

all preganglionic neurons
all postganglionic para- 
     sympathetic neurons
a very few postganglionic
     sympathetic neurons

Question 36

which neurons use norepinephrine

Answer 36

most postganglionic

sympathetic neurons

Question 37

enzymes used to destroy acetylcholine

Answer 37

acetylcholinesterase

Question 38

enzyme used to destroy norepinephrine

Answer 38

catechol-O-methyltransferase

monoamine oxidase

Question 39

In general, describe the activities of the parasympathetic nervous system. What is meant by the name “rest and recovery” system?

Answer 39

The parasympathetic nervous system is an energy conservation-restorative system. It regulates those activities that conserve and restore body energy during times of rest and recovery.

The parasympathetic nervous system dominates over sympathetic activity in the glands and smooth muscle of the gut, stimulating glandular secretion and the gut movements necessary for food to be digested and absorbed.

The acronym SLUD stands for salivation, lacrimation, urination, and defecation, all controlled by the parasympathetic nervous system

Question 40

In general, describe the activities of the sympathetic nervous system. What is meant by the name “fight or flight” system?

Answer 40

The sympathetic system prepares the body to meet emergency demands and is primarily involved with processes that expend energy. During physical or emotional stress, the sympathetic division dominates the parasympathetic system, initiating a series of activities known as the fight-or-flight response.

This includes increased heart rate, force of contraction, and blood pressure; increased blood flow to essential structures (brain, lungs, heart, skeletal muscles) and decreased activity in nonessential ones; increased rate and depth of respiration.

In addition, there is activation of the adrenal medulla, causing secretion of norepinephrine and epinephrine as hormones to greatly heighten the response.

Question 41

In general. describe why parasympathetic responses are short-lived and very precise while sympathetic responses are much longer-lived and body wide.

Answer 41

The parasympathetic system has very little divergence in the connections between preganglionic and postganglionic fibers, so that only very small areas of effectors are stimulated at any given time. Also, acetylcholine is rapidly destroyed in the synaptic clefts, so that the response to neurotransmitter is very short-lived.

The sympathetic system has a good deal of divergence between preganglionic and postganglionic fibers (1:5-500), so that the sympathetic message is sent body-wide. Secondly, norepinephrine is poorly removed from the synapse, so that it diffuses into the bloodstream for delivery throughout the body. Lastly, activation of the sympathetic nervous system results in secretion of norepine-phrine and epinephrine, hormones that have stronger and body wide effects.