Chapter 15: Autonomics

Somatic sensory

sensation from special senses(touch, pain, pressure), skin, and proprioceptors
*Aware of what is happening, Conscious, perceive.

Somatic motor

skeletal muscles, Voluntary, Aware, Can control
*You have full control.

Autonomic motor or Visceral Motor

1. Automatic, Involuntary, Does it on its own.
2. Efferent signals to Cardiac muscles, Smooth muscle, or gland.
Example= Don't have to tell heart to keep beating.
3. Regulated unconsciously(involuntary)
-Respond to visceral sensory= input, for this branch, constriction of sugar in blood, body unaware but body knows.
-Maintains homeostasis.

Somatic Lower motor neurons

-Single neuron from CNS to skeletal muscle
-Cell body in brainstem or anterior horn of spinal cord.
-Releases acetylcholine at synapse= Always acetylcholine receptor at motor end plate
*Happen in skeletal muscle, Start in brain and going to peripheral limbs.

Autonomic Lower motor neurons

Cardiac, smooth muscle, and glands
-Chain of 2 lower motor neurons
1st= preganglionic
2nd=postganglionic

1st autonomic lower motor neuron?

Preganglionic= cell body sits in lateral horn in brainstem/spinal cord
-Releases acetylcholine at synapse

2nd autonomic lower motor neuron?

Postganglionic= unmylinated axon, cell body in autonomic ganglion located in peripheral ganglia.
-Release acetylcholine or norepinephrine(can have either)

Hypothalamus

Autonomic nervous system
-"control center"= sensations, concentration of chemicals
-Integration and command center

Brainstem

Autonomic nervous system
-Reflex center= vomitting

Spinal cord

Autonomic nervous system
-Reflex center= defecation and micturition

Parasympathetic division

"Rest and Digest"
-Function= Conserving energy, replenish nutrients
-Control secretions in digestive system, Localized
-Long preganglionic axon, Short postganglionic axon
*Send signals locally, one organ only at a time*

Sympathetic division

"Fight or Flight"
-Function= Exercise, excitement, emergency
-Short preganglionic axon, long postganglionic axon
*Send signals easier, can activate multiple structures at the same time.

Parasympathetics degree of response

"Rest and digest"
-Localized response
-Long preganglionic axon and short postganglionic axon

Sympathetics degree of response

"Fight or Flight"
-Mass activation, many branches= more effectors
-Short preganglionic axon and long postganglionic axon

Parasympathetic division cranial components

4 cranial nerves carry parasympathetic signals, come off brain.
1) CN III Oculomotor
2) CN VII Facial
3) CN IX Glossopharyngeal
4) CN X Vagus

CN III Oculomotor

-Effector: ciliary muscles of the eye, sphincter pupilae muscle(controls pupil size)
-Response: Focus lens, constrict the pupil

CN VII Facial

-Effector: Submandibular and sublingual glands(increase salivary generation)
-Response: Increase salivary secretions

CN IX Glossopharyngeal

-Effector: Parotid gland
-Response: increase salivary secretions

CN X Vagus

-Effector: digestive organs, bronchi, heart
-Response: increase digestive secretions, constrict bronchi, decrease heart rate.

Pelvic splanchnic nerves

1. Preganglionic cell bodies located in lateral horn of S2-S4
2. Postganglionic cell bodies located in wall of effector organ
3. Effects: Smooth muscle constriction, increase digestive activity, increase urinary output

Sympathetic division

1. Preganglionic cell bodies in lateral horn T1-L2
2. Sympathetic trunk
-Chain of ganglia(cluster of cell bodies) bordering vertebral column
-House postganglionic cell bodies
-Hangs off anterior ramus
*White ramus communicans= "on ramp"
*Gray ramus communicans= "off ramp"

Sympathetic splanchnic nerves

-Do Not synapse in the sympathetic trunk
-Synapse below the diaphragm on pre vertebral ganglia
-Prevertebral ganglia:
*Celiac ganglia
*Superior mesenteric ganglia
*Inferior mesenteric ganglia

Celiac ganglia

stomach, duodenum, liver, spleen, gallbladder, pancreas

Superior mesenteric ganglia

small intestine, large intestine, pancreas, kidney, ureters

Inferior mesenteric ganglia

large intestine, rectum, bladder, ureters, reproductive organs

Spinal nerve pathway

Sympathetic pathway
1. Anterior root
2. Spinal nerve
3. Anterior ramus
4. White ramus communicans
5. Synapse on cell body of postsynaptic neuron
6. Gray ramus communicans
7. Anterior/posterior ramus to effector
-Integumentary structures in neck, torso, limbs

Postganglionic sympathetic nerve pathway

1. Anterior root
2. Spinal nerve
3. Anterior ramus
4. White ramus communicans
5. Synapse on cell body of postsynaptic neuron
6. Postsynaptic neuron directly to effector
-Head, neck or thoracic viscera

Splanchnic nerve pathway

Sympathetic pathway
1. Anterior root
2. Spinal nerve
3. Anterior ramus
4. White ramus communicans
5. Exit sympathetic trunk WITHOUT Synapse
6.Head below diaphragm
7. Synapse on pre vertebral ganglion
8. Postsynaptic neuron to effector
-Abdominal or pelvic viscera

Adrenal Medulla pathway

Sympathetic pathway
1. Anterior root
2. Spinal nerve
3. Anterior ramus
4. White ramus communicants
5. Exit the Sympathetic trunk Without Synapse
6. No Postganglionic nerve
7. Synapse on cells in the adrenal medulla(adrenal gland)
8. Stimulates the release of epinephrine and norepinephrine into the blood to enhance and prolong Fight and Flight

Autonomic plexuses

Contain Sympathetic and parasympathetic axons
-Do the opposite of each other

Cardiac plexus

innervate heart, fight or flight
-Sympathetic innervations= increased heart rate
-Parasympathetic innervations= decreased heart rate.

Pulmonary plexus

Dilate lungs
-Sympathetic innervations= bronchodilator
-Parasympathetic innervations= bronchoconstriction

Esophageal plexus

Coordinate smooth muscle
-Sympathetic innervations= decrease motility
-Parasympathetic innervations= coordinate motility

Enteric nervous system

Coordinate smooth muscle contractions
1. Autonomic motor and visceral sensory neurons in the wall of the gastrointestinal tract
2. Innervates smooth muscle and glands
3. Coordinates peristalsis and digestive secretions
4. Includes 2 large plexus:
-Submucosal
-Myenteric

Two neurotransmitters in use...

Acetylcholine and Norepinephrine
1. Can cause either stimulation or inhibition
2. Cells that release acetylcholine= Cholinergic neurons
3. Cells that release norepinephrine= adrenergic neurons(adrenalin)

Cholinergic receptors

1. Receptors that bind to Acetylcholine
2. Nicotinic receptors= Nicotine can bind
-Found in both parasympathetic and sympathetic divisions and adrenal medulla
-Initiates an excitatory response
* Opens a protein channel for sodium diffusion
3. Muscarinic receptors
-Mostly found in parasympathetic division, limited in sympathetic
-Involve an indirect cell response via a G protein(complex)
-Can be either excitatory or inhibitory

Adrenergic receptors

1. Receptors that bind Norepinephrine
2. Alpha receptors= excitatory
-Typically excitatory and found in smooth muscle and blood vessels.
3. Beta receptors
-B1= Stimulatory, heart, and kidney
-B2= Inhibitory, smooth muscle, liver, skeletal muscle
-B3= Either, bladder and smooth muscle= depends on effector.

Cardiovascular reflex

-Stretch receptors in blood vessel walls sense stretch stimulus
-Stimulus causes action potential that travels on a visceral sensory neuron to the cardiac center in the medulla oblongata
-Inhibits sympathetic nervous system, and activates parasympathetic nervous system.
*How much blood, and force of blood.

Gastrointestinal reflex(defecation)

-Rectum responds to stretch signals sent to spinal cord
-Motor neurons stimulate contraction in smooth muscle

Micturition(urination)

-Stretch stimulus when bladder is full-signal sent to spinal cord
-Contraction of smooth muscle in the bladder and relaxation of sphincters.

Antagonistic effects

both divisions(parasympathetic and sympathetic) contribute to an overall response.
Ex: Heart rate control, GI tract control

Cooperative effects

both divisions(parasympathetic and sympathetic) contribute to an overall response.
Ex: Male sexual response and orgasm

Sympathetic innervation only...

-Opposing effects can be achieved without dual innervation
Ex: Blood vessels= constrict with increased activity, dilate with decreased activity

Autonomic tone

1. Most effectors are innervated by both divisions of the ANS(Parasympathetic and Sympathetic)
2. Both continuously release neurotransmitter
-Cause of autonomic tone-neither the "gas" or "breaks" is fully on