Ch.15 - The Autonomic Nervous System

Question 1

Somatic Nervous System

Answer 1

innervate skeletal muscles of the body and contains both sensory and motor neurons. It is voluntary.

Sensory input: From somatic and special senses

Control of motor output: Voluntary control from cerebral cortex, with contributions from corpus striatum, cerebellum, brainstem, and spinal cord.

Motor neuron pathway: One-neuron pathway: Somatic motor neurons extending from CNS synapse directly. with effector

Neurotransmitters and hormones: All somatic motor neurons release only acetylcholine (ACh).

Effectors: Skeletal Muscles

Responses: Contraction of skeletal muscle.

Question 2

The Autonomic Nervous System

Answer 2

the part of the nervous system that regulates cardiac muscle, smooth muscles, and glands. It contains both autonomic sensory and motor neurons. It is involuntary.

Sensory input: Mainly from interoceptors (sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitors conditions in the internal NS); some from somatic senses and special senses.

Control of motor output: Involuntary control from hypothalamus, limbic system, brainstem, and spinal cord: limited control from cerebral cortex.

Motor neuron pathway: Usually two-neuron pathway: Preganglionic neurons extending from CNS synapse with postganglionic neurons in autonomic ganglion, and postganglionic neurons extending from ganglion synapse with visceral effector. Alternatively, preganglionic neurons may extend from CNS to synapse with chromaffin cells of adrenal medullae.

Neurotransmitters and hormones: All sympathetic and parasympathetic preganglionic neurons release ACh. Most sympathetic postganglionic neurons release norepinephrine (NE); those to most sweat glands release ACh. All parasympathetic postganglionic neurons ACh. Chromaffin cells of suprarenal medullae release epinephrine and norepinephrine (NE).

Effectors: Smooth muscle, cardiac muscle, and glands

Responses: Contraction or relaxation of smooth muscle; increased or decreased rate and force of contraction of cardiac muscle; increased or decreased secretions of glands.

Question 3

Type of interoceptors

Answer 3

Chemoreceptors - monitor blood CO2 level

Mechanoreceptors - detect the degree of stretch in the walls of organs or blood vessels

Question 4

Sympathetic Nervous System

Answer 4

Promotes fight-or-flight responses , which prepares the body for emergency situations

Question 5

Parasympathetic Nervous System

Answer 5

Enhances rest-and-digest activities by conserving and restoring the body’s energy during times of resting and digesting

Question 6

Dual Innervation

Answer 6

When organs receive impulses from both sympathetic and parasympathetic fibers

Question 7

Enteric Plexuses

Answer 7

Part of the ANS; involuntary; contains:

1. sensory neurons - monitor changes within the digestive canal and the stretching of its walls
2. interneurons - integrate information from sensory neurons and provide input to motor neurons
3. motor neurons - govern contraction of digestive canal smooth muscle and secretion of digestive canal glands

Question 8

Preganglionic Neuron

Answer 8

The first of the two autonomic motor neurons

• Cell body is in the brain or spinal cord
• Has a preganglionic fiber, or myelinated axon, that passes out of the CNS as a part of the cranial or spinal nerve
• Type B fiber

Question 9

Postganglionic Neuron

Answer 9

The second neuron in the autonomic motor pathway that lies entirely outside the CNS

• Cell body and dendrites are located int he autonomic ganglion where it makes synapses with one or more preganglionic fibers
• Its axon is unmyelinated and terminates in a visceral effector
• Type C fiber

Question 10

Sympathetic Preganglionic Neurons

Answer 10

• Cell bodies are located in the lateral gray horns of the 12 thoracic and first L2 or L3 segments, this division is known as the Thoracolumbar Division
• Axons of the sympathetic preganglionic neurons are known as the Thoracolumbar Outflow

Question 11

Parasympathetic Preganglionic Neurons

Answer 11

• Cell bodies are located in cranial nerve nuclei (III, VII, IX, and X) in the brain stem and lateral gray horns of S2 - S4 segments of the cord, this division is known as the Craniosacral Division
• Axons of the preganglionic parasympathetic neurons are known as the craniosacral outflow

Question 12

There are 2 types of autonomic ganglia

Answer 12

Sympathetic Ganglia
- sites of synapse between sympathetic ganglionic and postganglionic neurons

Parasympathetic (intramural) Ganglia
- Preganglionic axons of the parasympathetic division synapse with postganglionic neurons in parasympathetic ganglia

Question 13

There are 2 major types of sympathetic ganglia

Answer 13

Sympathetic Trunk Ganglia (Vertebral or Paravertebral)

• Lie in a vertical row on either side of the vertebral column and extend from the base of the skull to the coccyx
• There are superior, middle, and inferior cervical ganglia
• Primarily innervate organs above the diaphrgam

Prevertebral or Collateral Ganglia

• Lie anterior to the spinal column and close to large abdominal arteries
• Includes: (1) Celiac, (2) Superior mesenteric, (3) Inferior mesenteric, (4) Cortical, and (5) Renal ganglia
• Innervate organs below the diaphragm

Question 14

Parasympathetic (intramural) Ganglia

Answer 14

Parasympathetic ganglia in the head: (1) Ciliary ganglion (2) Pterygopalatine ganglion (3) Submandibular ganglion (4) Otic ganglion

Question 15

Axons that form tangled networks of sympathetic and parasympathetic neurons are called

Answer 15

autonomic plexuses

Question 16

The major plexuses in the thorax are the

Answer 16

Cardiac Plexus, which supplies the heart, and Pulmonary Plexus which supplies the bronchial tree

Question 17

The major plexuses in the abdomen and pelvis are often named after the artery along which they are distributed

Answer 17

Celiac Plexus

• Largest autonomic plexus that surrounds the celiac trunk
• Contains 2 large celiac ganglia, two aorticorenal ganglia, and a dense network of autonomic axons
• Distributed to the stomach, liver, spleen, pancreas, gallbladder, kidneys, suprarenal medullae, testes, and ovaries

Superior Mesenteric Plexus
- Contains superior mesenteric ganglion and supplies the small and large in intestines

Inferior Mesenteric Plexus
- Contains the inferior mesenteric ganglion and innervates the large intestine

Hypogastric Plexus

• Axons of some sympathetic postganglionic neurons from the inferior mesenteric ganglion also extend through the hypogastric plexus
• Supply the pelvic viscera

Renal Plexus
- Contains renal ganglion and supplies renal arteries within the kidneys an ureters

Question 18

The major plexuses in the abdomen and pelvis are often named after the artery along which they are distributed

Answer 18

Celiac Plexus

• Largest autonomic plexus that surrounds the celiac trunk
• Contains 2 large celiac ganglia, two aorticorenal ganglia, and a dense network of autonomic axons
• Distributed to the stomach, liver, spleen, pancreas, gallbladder, kidneys, suprarenal medullae, testes, and ovaries

Superior Mesenteric Plexus
- Contains superior mesenteric ganglion and supplies the small and large in intestines

Inferior Mesenteric Plexus
- Contains the inferior mesenteric ganglion and innervates the large intestine

Hypogastric Plexus

• Axons of some sympathetic postganglionic neurons from the inferior mesenteric ganglion also extend through the hypogastric plexus
• Supply the pelvic viscera

Renal Plexus
- Contains renal ganglion and supplies renal arteries within the kidneys an ureters

Question 19

Structure of the Sympathetic Division

Answer 19

Pathways from sympathetic trunk ganglia to visceral effectors

• Enter spinal nerves
• Form cephalic periarterial nerves
• Form sympathetic nerves
• Form splanchnic (relating to viscera, especially on the abdomen) nerves