Autonomic Nervous System

lecture: 2/5

I. Somatic vs. Autonomic Nervous Systems A. Effectors

What are the effectors of the somatic nervous system?

Skeletal muscle; the somatic nervous system is voluntary

1. What are the effectors of the autonomic nervous system?

2. What types of involuntary muscle are controlled by the autonomic nervous system?

1. Involuntary muscle and glands

2. Smooth muscle and cardiac muscle

What types of glands are controlled by the autonomic nervous system?

Exocrine and endocrine glands

B. Efferent Pathways Somatic

1. What type of nerve fibers are found in the somatic nervous system's efferent pathway?

2. Does the somatic nervous system's efferent pathway contain a ganglion?

1. Thick, myelinated nerve fibers

2. No, there is no ganglion

Autonomic

1. What are the two neurons involved in the autonomic nervous system's efferent pathway?

2. Where is the cell body of a preganglionic neuron located?

3. What are the characteristics of a preganglionic neuron's axon?

1. A preganglionic neuron and a postganglionic neuron.

2. In the CNS

3. It is thin and slightly myelinated

1. Where is the cell body of a postganglionic neuron located?

2. What are the characteristics of a postganglionic neuron's axon?

1. In a ganglion outside the CNS

2. it is unmyelinated

1. Where are autonomic ganglia located?

2. What three types of autonomic ganglia are listed in the lecture?

1. Outside the CNS

2. Chain ganglia, collateral ganglia, and terminal ganglia

C. Neurotransmitters

Somatic

1. What neurotransmitter does the somatic nervous system use?

2. What effect does acetylcholine have in the somatic nervous system?

1. Acetylcholine

2. Stimulatory effects

Autonomic

1. What neurotransmitter does the preganglionic autonomic neuron release?

2. What neurotransmitters can the postganglionic autonomic neuron release?

3. What effects can autonomic postganglionic neurotransmitters have?

1. Acetylcholine

2. Norepinephrine or acetylcholine

3. They can stimulate or inhibit

II. Sympathetic vs. Parasympathetic Divisions

A. Systemic Effects

Sympathetic Division

1. What does the sympathetic division prepare the body for?

2. What does the sympathetic division increase blood flow to?

1. Action — the fight-or-flight response

2. The heart and muscles

1. What happens to the bronchioles during sympathetic activation?

2. What happens to glucose secretion by the liver during sympathetic activation?

1. They dilate

2. It increases

Parasympathetic Division

1. What does the parasympathetic division prepare the body for?

2. What happens to heart rate during parasympathetic activation?

3. What happens to respiratory rate during parasympathetic activation?

1. Conserving energy — the rest-and-digest response

2. It decreases

3. It decreases

1. What happens to blood pressure during parasympathetic activation?

2. What happens to pupil size during parasympathetic activation?

3. What happens to digestive tract activity during parasympathetic activation?

1. It decreases

2. It decreases

3. It increases

B. Anatomical Differences

Sympathetic Division

1. Where does the sympathetic division originate?

2. What is another name for the sympathetic division based on its origin?

1. The thoracic and lumbar regions, T1–L2, of the spinal cord

2. Thoracolumbar

1. How long are sympathetic preganglionic fibers compared with postganglionic fibers?

2. Where are sympathetic ganglia located?

1. Preganglionic fibers are short and postganglionic fibers are long

2. Close to the spinal cord, in chain ganglia

Parasympathetic Division

1. Where does the parasympathetic division originate?

2. What is another name for the parasympathetic division based on its origin?

1. In the brain and spinal cord

2. Craniosacral

1. How long are parasympathetic preganglionic fibers compared with postganglionic fibers?

2. Where are parasympathetic ganglia located?

1. Preganglionic fibers are long and postganglionic fibers are short

2. Close to the effector organs, in terminal ganglia

C. Neurotransmitter Differences

Sympathetic Division

1. What does the sympathetic postganglionic neuron release?

2. What type of receptors respond to sympathetic norepinephrine?

1. Norepinephrine

2. Adrenergic receptors

• What do alpha adrenergic receptors cause?

  • What do beta adrenergic receptors cause?

• Vasoconstriction

  • Vasodilation

Parasympathetic Division

1. What does the parasympathetic postganglionic neuron release?

2. What receptors does acetylcholine act on in the parasympathetic ganglion?

1. Acetylcholine

2. Nicotinic cholinergic receptors

1. What receptors does acetylcholine act on at the target tissue?

2. What inactivates acetylcholine?

3. Why is the parasympathetic response short-lived compared to the sympathetic response?

1. Muscarinic cholinergic receptors

2. Cholinesterase

3. Acetylcholine is inactivated by cholinesterase

III. Sympathetic Division

A. Preganglionic Neurons

1. Where are sympathetic preganglionic neurons located?

2. What do the sympathetic preganglionic neurons produce in the spinal cord?

1. In spinal cord segments T1–L2

2. The lateral horns

1. How do sympathetic preganglionic neurons enter the chain ganglia?

2. What happens when sympathetic preganglionic neurons synapse in the chain ganglia?

1. Through the white ramus

2. They synapse with postganglionic neurons

What happens to some sympathetic preganglionic fibers after entering the chain ganglia?

Some pass through the chain ganglia and form splanchnic nerves

1. What do some sympathetic preganglionic fibers form after passing through the chain ganglia?

2. What two collateral ganglia are listed in the lecture?

1. Collateral ganglia

2. Celiac and mesenteric ganglia

B. Postganglionic Neurons

• How do some sympathetic postganglionic neurons leave the chain ganglia?

  • Where do some sympathetic postganglionic neurons synapse?

• They synapse in the chain ganglia and exit through grey rami

  • in the collateral ganglia

1. What two significant exceptions are mentioned regarding sympathetic targets?

2. What structures in the skin are innervated by the sympathetic system?

• The skin and adrenal gland

• Sweat glands and arrector pili muscles

What does the sympathetic system cause the adrenal gland to release?

Epinephrine and norepinephrine

IV. Parasympathetic Division

A. Cranial Outflow

1. Which cranial nerves carry parasympathetic preganglionic fibers?

2. Which cranial nerve is associated with the cardiac plexus?

1. Oculomotor (III), facial (VII), glossopharyngeal (IX), and vagus (X)

2. Vagus nerve (X)

1. Which cranial nerve is associated with the pulmonary plexus?

2. Which cranial nerve is associated with the celiac plexus?.

1. Vagus nerve (X)

2. Vagus nerve (X)

B. Sacral Outflow

1. What spinal cord levels produce the parasympathetic sacral outflow?

2. What nerves carry the parasympathetic sacral outflow?

1. S2–S4

2. Pelvic splanchnic nerves

1. What plexus is associated with the parasympathetic sacral outflow?

2. What does the inferior hypogastric plexus innervate?

1. The inferior hypogastric plexus

2. The rectum, urinary bladder, and reproductive organs

Somatic

1. Effectors:

2. Pathway:

3. Fibers:

4. Neurotransmitter:

5. Effect:

1. Skeletal muscle

2. No ganglion

3. Thick, myelinated

4. Acetylcholine

5. Stimulatory

Autonomic

1. Effectors:

2. Pathway:

3. Fibers:

4. Neurotransmitter:

5. Effect:

1. Smooth muscle, cardiac muscle, glands

2. Preganglionic → ganglion → postganglionic

3. Preganglionic: thin/slightly myelinated;

   1. Postganglionic: unmyelinated

4. Preganglionic: ACh;

   1. Postganglionic: NE or ACh

5. Stimulatory or inhibitory

Sympathetic

1. Response

2. Origin

3. Name

4. Preganglionic fibers

5. Postganglionic fibers

6. Ganglia

7. Postganglionic NT

8. Receptors

1. Fight or flight

2. T1–L2

3. Thoracolumbar

4. Short

5. Long

6. Close to spinal cord

7. Norepinephrine

8. Adrenergic

Parasympathetic

1. Response

2. Origin

3. Name

4. Preganglionic fibers

5. Postganglionic fibers

6. Ganglia

7. Postganglionic NT

8. Receptors

1. Rest and digest

2. Brain + spinal cord

3. Craniosacral

4. Long

5. Short

6. Close to effector organs

7. Acetylcholine

8. Muscarinic at target tissue

Somatic vs. autonomic

• Somatic → ?

  • Autonomic → ?

• 1 neuron

  • 2 neurons (preganglionic + postganglionic)

Sympathetic

• T?–L?

  • Short → ?

  • NE (norepinephrine) → ?

    • Alpha receptors → ?

    • Beta receptors → ?

• T1–L2

  • Long

  • adrenergic

    • vasoconstriction

    • vasodilation

Parasympathetic

• Craniosacral

• Long → ?

• ACh → ?

• Short

• muscarinic at target

Parasympathetic cranial nerves

• III → ?

• VII → ?

• IX → ?

• X → ?

• Oculomotor nerve (3)

• Facial nerve (7)

• Glossopharyngeal nerve (9)

• Vagus nerve (10)

Parasympathetic sacral

• S?–S?

• Pelvic splanchnic nerves

• S2–S4