Automatic Nervous System

Question 1

Describe the sensory arm of the ANS, noting the general types of receptors supplying input.

Answer 1

parasympathetic - promotes maintenance functions, conserves energy (rest and digest)
slow down heart rate

sympathetic - mobilizes body during stress and physical activity (fight or flight)
increases heart rate, dilates pupils, sexually aroused

Question 2

What effectors can be activated by a visceral reflex arc?

Answer 2

smooth muscle, cardiac or glands

Question 3

Compare and contrast the motor pathways of the somatic nervous system (SNS) and the autonomic nervous system (ANS).

Answer 3

BOTH begin the the CNS

SNS -

• consists of a single neuron (lower motor neuron)
• motor fibers are myelinated
• • effectors are skeletal muscles
• NT is ACh

vs

ANS
- two motor neurons

step 1) the first neuron in the pathway is the preganglion nerve

step 2) the preganglionic nervous synapses within an automatic ganglion with a postganglionic neuron

step 3) the postganglionic neuron is the second neuron in the pathway

step 4) postganglionic axons extend from the ganglion to the effectors

Question 4

What is a preganglionic neuron? a postganglionic neuron?

Answer 4

preganglionic fibers are myelinated and first neuron while postganglionic fibers are unmyelinated and second neuron

Question 5

Which division of the ANS is sometimes called the thoracolumbar division? the craniosacral? Explain these designations.

Answer 5

sympathetic ; parasympathetic

Question 6

Contrast the sympathetic and parasympathetic motor pathways, noting differences in origin, length of preganglionic and postganglionic fibers, location of ganglia, and neurotransmitter profiles.

Answer 6

in good notes

Question 7

What are the CNS origins of the parasympathetic division?

Answer 7

from neuron cell bodies in the brain stem and sacral regions of the spinal cord

Question 8

Which body regions and organs are served by parasympathetic preganglionic fibers originating with CNs III, VII, and IX?

Answer 8

CN 3- smooth muscles in the eye

CN 7 - stimulate the secretory activity of nasal, lacrimal, and salivary glands

CN 9- activate salivary glands (parotid glands)

Question 9

Which body regions and organs are served by parasympathetic preganglionic fibers originating with CN X?

Answer 9

vagus

• innervates the heart, lungs and esophagus
• passes into the abdominopelvic cavity where it innervates abdominal viscera

Question 10

Which body regions and organs are served by sacral parasympathetic outflow?

Answer 10

rectum, bladder and genitalia

Question 11

Where specifically does the sympathetic division arise?

Answer 11

the division arises from the ventral roots of the spinal nerves T1- L2 cell bodies of the preganglionic neurons are located in the lateral horn of these cord segments

Question 12

Trace the pathway of sympathetic preganglionic fibers from the spinal cord to a paravertebral ganglion

Answer 12

ventral roots —– ventral ramus —– white ramus communicans —- paravertebral ganglion

Question 13

What are the three things that can happen to a preganglionic fiber in a paravertebral ganglion?

Answer 13

1. It can synapse with a postganglionic neuron in the paravertebral ganglion at the same level
2. It can ascend/descend the chain and synapse in another chain ganglion at a higher/lower level
3. It can pass through the sympathetic trunk and synapse in a collateral ganglion anterior to the vertebral column

Question 14

Which is more numerous –white rami communicantes or gray rami communicantes? Explain your answer.

Answer 14

gray

Question 15

What is a cholinergic fiber? an adrenergic fiber?

Answer 15

cholinergic- fibers that release ACh

adrenergic - fibers that release Norepinephrine at a synapse

Question 16

Which fibers of the ANS are cholinergic? Which are adrenergic?

Answer 16

cholingeric- preganglionic and all parasympathetic postganglionic fibers at synapses with their effectors

adrenergic - fibers that release norepinephrine at a synapse; released by postganglionic fibers

Question 17

Identify the two types of cholinergic receptors. What is the general effect of activation (by ACh binding) of each receptor type.

Answer 17

1. ) nicotinic - the effect of ACh binding to nicotinic receptors is always stimulatory —- excitation of the neuron or effector cell
2. ) muscarinic - associated with ion channels, effect of AC binding to muscainic receptors depends on the type of ion channel that open/closes
   * short lived effect due to the present of AChE in the synapse

Question 18

Identify the classes and subclasses of adrenergic receptors.

Answer 18

Alpha :

    * a1 - located in blood vessels serving the skin, mouse, abdominal viscera, kidneys, salivary glands, almost all sympathetic effectors but the heart  - effects are generally EXCITATORY

    * a2 - located in some vascular smooth muscle, on blood platelets, on beta cells (secrete insulin) & acing cells (digestive secretions) of the pancreas  - effects are generally INHIBITORY 

Beta: acts y increasing intracellular cAMP levels

* B1 - located in cardiac muscles - effect is EXCITATORY 

* B2 - found in smooth muscle in walls of blood vessels, respiratory passages, digestive tract, bladder, urinary passages  - norepinephern binding is INHIBITORY --- relaxation of smooth muscle 

* B3- in adipose tissue  - effect is to stimulus lipolysis

Question 19

When activated, which of the receptor subclasses (#26) generally produce excitation of the target cell? which generally cause inhibition?

Answer 19

Excitation - a1, b1, b3

Inhibition - a2, b2

Question 20

Describe the physiologic effects of sympathetic activation.

Answer 20

Adrenal medullary cells secrete epinephrine and NE into the blood when the sympathetic division is mobilized

• increasing heart rate , raising blood glucose levels and metabolic rate

Question 21

Explain why blood vessels are said to exhibit sympathetic (vasomotor) tone.

Answer 21

it determines whether the blood vessels constrict (dilator)

Question 22

Explain why the heart at rest is said to exhibit parasympathetic (vagal) tone.

Answer 22

the parasympathetic is meant to control the body at rest