Chapter 10: Autonomic and Somatic Nervous System

BIOS 213

Autonomic Nervous System

involuntary; regulates the activity of smooth muscle, cardiac muscle, and glands

the ____ will either excite or inhibit ongoing activities

autonomic nervous system

Autonomic Nervous System branches:

Sympathetic, parasympathetic, enteric

Sympathetic branch

prepares body for emergencies; fight-or-flight response

Parasympathetic branch

conserves and restores body energy; rest and digest

Enteric branch

an extensive network of neurons confined to the wall of the gastrointestinal tract

Most organs receive ______

dual innervation (sympathetic and parasympathetic)

Main regulator of autonomic functions:

hypothalamus

Autonomic motor pathway:

preganglionic neuron and postganglionic neurons; visceral effector

Preganglionic neuron

extends from CNS to an autonomic ganglion

Postganglionic neuron

extends from the autonomic gaglion to the effector

Preganglionic neurons are located in the:

brain and spinal cord

Visceral effector:

smooth muscle, cardiac muscle, and glands

Cranio-

refers to the cranium; skull

Sacral-

related to the sacrum

The parasympathetic division is made up of:

the craniosacral division, preganglionic neurons, and terminal ganglia

Craniosacral division:

Cranium and sacrum

Preganglionic neurons of the craniosacral division exit the CNS at the:

brain stem and sacral spinal cord

Terminal ganglia

associated with the parasympathetic division of the autonomic nervous system

Preganglionic neurons synapse with postganglionic neurons in or near ____

visceral effector organ

4 cranial nerves that contain parasympathetic fibers:

Oculomotor (III), facial (VII), glossoparyngeal (XI), Vagus (X)

Oculomotor (III) nerve:

preganglionic fibers exit midbrain and synapse on the ciliary ganglion; post ganglionic fibers innervate the ciliary muscle of the eye

Facial (VII) nerve:

preganglionic fibers exit the pons and synapse in the pterygopalatine ganglion and in the submandibular ganglion

Pterygopalatine ganglion:

postganglionic fibers synapse on nasal mucosa, pharynx palate, and lacrimal glands

Submandibular ganglion:

postganglionic fibers synapse on salivary glands

Glossopharyngeal (IX):

preganglionic fibers synapse on optic ganglion; postganglionic fibers innervate salivary gland

Vagus (X) nerve:

preganglionic fibers exit medulla, branch into several plexi and nerves, and travel to ganglia within effector organs

Vagus nerve accounts for___ of parasympathetic fibers

75%

Effector organs:

heart, lungs, kidney, esophagus, stomach, pancreas, liver, and intestines

Sacral nerves are part of the _____

parasympathetic nervous system

Sacral Nerves:

preganglionic nerves from the sacral region of the spinal chord provide innervation to the lower part of the large intestine, rectum, urinary, and reproductive organs —> terminal ganglia are located within these organs

The sympathetic division is made up of the:

thoracolumbar division and preganglionic neurons

thoracolumbar

thorax and lumbar

preganglionic neurons located in the sympathetic division are:

cell bodies in throacic and lumbar regions of the spinal cord (T1-T12 and L1-L2)

4 types of sympathetic ganglion:

superior mesenteric ganglia, celiac ganglia, inferior mesenteric ganglia, and paravertebral ganglia

Paravertebral ganglia

ganglia within each row are interconnected, forming a sympathetic chain of ganglia —> nerve fibers that connect each ganglia form sympathetic trunk

Paravertebral ganglia mostly innervate organs above the _____

diaphragm and in the skin

Collateral (prevertebral) ganglia

synapse with splanchnic nerves

splanchnic nerves

formed by sympathetic neurons that exit the spinal cord below the diaphragm

3 branches of collateral ganglia:

celiac, superior mesenteric, and inferior mesenteric 

Collateral postganglionic neurons innervate:

digestive, urinary, and reproductive system organs

Celiac ganglion innervate the ____

stomach

Superior mesenteric ganglion innervate the ____

reproductive system organs

Inferior mesentaric ganglion innervate the ____

urinary system

The chromaffin cells of adrenal medulla are innervated by ____

sympathetic preganglionic neurons

chromaffin cells

modified sympathetic postganglionic neurons that lack dendrites and axons; release hormones into the blood

Chromaffin cells release the catecholamine hormones:

epinephrine and norepinephrine

Neuroeffector junction

synapse between autonomic postganglionic neuron and visceral effector organ

Neuroeffector junctions use:

varicosities and receptors located along entire effector cell

Varicosities

swollen regions found at the ends of axon terminals

Two types of neurotransmitters and receptors:

cholinergic; adrenergic

Cholinergic neurons

release acetylcholine

In the ANS, cholinergic neurons include:

all preganglionic neurons, Most parasympathetic postganglionic neurons (NOT male reproductive), and some sympathetic postganglionic neurons (sweat glands, skeletal muscle, and blood vessels)

Cholinergic recetpors

bind ACh

two kinds of cholinergic receptors:

Nicotinic and muscarinic

Cholinergic Nicotinc receptors are ____

ionotropic

Cholinergic Muscarinic receptors are ____

metabotropic (G-protein coupled)

Adrenergic Neurons release:

norepinephrine

norepinephrine

NT released by postganglionic cells of the sympathetic nervous system

epinephrine

hormone released by chromaffin cells of the adrenal medulla

two main types of adrenergic receptors:

alpha and beta

In the ANS, adrenergic receptors are found on:

visceral effectors innervated by most sympathetic postganglionic axons (NOT sweat glands)

The adrenergic receptors, Alpha and Beta, are both:

G-protein coupled (metabotropic) receptors

Autonomic tone

the balance between parasympathetic and sympathetic activity; regulated by hypothalamus

Autonomic reflexes

help maintain homeostasis

An autonomic reflex arc consists of a:

sensory receptor, sensory neuron, integrating center, motor neurons, and an effector

What centers control autonomic activities?

hypothalamus, brain stem, and spinal cord

Somatic nervous system

innervates the skeletal muscles of the body

The somatic nervous system is comprised of:

one single somatic motor neuron and skeletal muscle

neuromuscular junction

synapse between somatic motor neuron and skeletal muscle fiber

Neuromuscular junctions contain:

synaptic end bulb; motor end plate

motor end plate

part of the membrane in the skeletal muscle cell that contains nicotinic ACh receptors

If you removed the external Ca²⁺ at the neuromuscular junction, you would most directly affect:

acetylcholine exocytosis

Botulinum toxin

blocks exocytosis of ACh from synaptic end bulbs

alpha-latrotoxin

causes massive exocytosis of ACh from synaptic end bulbs —> paralysis of constant contraction

Curare

binds to and blocks nicotinic ACh receptors

Organophosphates

chemicals that inhibit acetylcholinesterase