AUTONOMIC NERVOUS SYSTEM

Biology 226Dr. M. KhanAmanuel Petros Debbie CornishAlka Jagatia Marie TsounguiCortni Rudolph Mariya Demidovich

Introduction

Autonomic Nervous SystemAuto (self) nom (govern)

We are not in control of the functions that are performed by the ANS

It is the involuntary nervous system

Organizational chart of the nervous system

ANS (Comparison)

Parasympathetic/Sympathetic

The ANS acts through a balance of its two separate subdivisions.

They serve many of the same target organs through dual innervation.

They work antagonistically to one another to maintain homeostasis.

Whatever one stimulates, the other inhibits.

Sympathetic

“fight-or-flight” Acts in emergency situations that cause

stress and require us to “fight” or “flight” Located to the sympathetic chain which

connects skin, blood vessels, organs in the body

The sympathetic chain is located in the spine and consists of ganglia

Parasympathetic

Responsible for the control of involuntary body functions

Known as the “rest and digest system” Works to counterbalance the sympathetic

nervous system to maintain the body in homeostasis

Comparison Sympathetic Structure Parasympathetic

Rate increase Heart Rate decrease

Force increase Heart Force decrease

Bronchial Muscle Relaxed

Lungs Bronchial muscle Contract

Pupil dilation Eye Pupil constriction

Motility reduced Intestine Digestion increased

Sphincter closed Bladder Sphincter relaxed

Decreased urine secretion

Kidneys Increased urine secretion

•The SNS is responsible for up and down regulating of many homeostatic mechanisms in living organisms

•Constantly active at a basal level to maintain homeostasis

•The hypothalamus is the main integration center of the ANS

•Two kinds of neurons involved in the transmission of any signal through the sympathetic system• Preganglion• Postganglion

•Preganglionic fibers are located in the spinal cord (T1-L2) known as the “Thoracolumbar Division”•Postganlionic fibers extend from the ganglion to the effector organs, “Craniosacral Division”

Cranial Outflow

Preganglion fibers come from the cranial and sacral division

Oculomotor Nerves (CIII) Smooth muscles in the eyes (pupil constriction)

Facial Nerves (CVII) Nasal glands Lacrimal glands Superior salivatory nuclei

Glossopharyngeal nerves (CIX) Inferior salivatory nuclei

Vagus Nerves (CX) Fibers to neck and nerve plexuses

Sacral Outflow

Most of the large intestine and pelvic organs

Distal half of large intestine Urinary bladder Ureters Reproductive organs

Thoracolumbar

Preganglionic fibers come from cell bodies of preganglionic neurons in spinal cord (T1-L2)

After leaving the cord via the ventral root, preganglionic fibers pass through a white ramus communicans to enter the sympathetic truck (chain) ganglia

The sympathetic trunks flank each side of the vertebral column

Neurotrasmitters

Substances released from neurons that influences the likelihood that an action potential in the presynaptic terminal will result in the postsynaptic cell

Effects of autonomic activity lies in knowing which neurotransmitters are released by the autonomic fibers and what kind of receptors occur on the target cells

Axon terminals of autonomic neurons release two neurotransmitters Norepinephrine (adrenergic fibers) Acetylcholine (cholinergic fibers)

Majority of sympathetic postganglionic fibers are adrenergic

Cholinergic fibers include all preganglionic fibers of both division Postganglionic fibers of parasympathetic Few sympathetic postganglionic fibers

Receptor Type

Norepinephrine affects visceral effectors by first binding to adrenergic receptors in their plasma

Adrenergic receptor types Alpha ( ) Beta ()βα

Subtypes of alpha and beta receptors include (B1, B2, B3, A1, A2)

ACh binds to cholinergic receptors Nicotinic Muscarinic

Subtypes Nicotinic-1, Nicotinic-2 Muscarinic-1, Muscarinic-2, Muscarinic-3

All Ach receptors are either nicotinic or muscarinic

Neurotransmitters

Autonomic Disorders

Most reflect exaggerated or deficient control of smooth muscle activity

Hypertension (high blood pressure) Results from an overactive sympathetic

vasoconstrictor response Makes the heart work harder to pump blood to

the body Contributes to arthrosclerosis (hardening of

arteries) Factors that contribute to hypertension;

smoking, weight, genetics, chronic kidney disease, thyroid disorders

Horner’s Syndrome Damage to SNS Major sign is drooping of the upper eyelid Due to loss of sympathetic innervation to the eye

(superior tarsal muscle) Raynauds Disease (Body limits blood flow to

hands and feet) Exaggerated vasoconstriction response Provoked by exposure to cold or emotional

stress In severe cases, blood circulation to fingers and

toes diminish leading to skin ulcers or gangrene Vasodilators are used as treatment

Autonomic neuropathy Common complication of diabetes mellitus Nerve damage occurs due to high blood glucose Symptoms include dizziness and urinary

discontinance Autonomic Dysreflexia (hyperreflexia)

Dangerous complication of spinal cord injury Uncontrolled activation of autonomic neurons Spinal cord injuries at T6 or higher are at rish Trigger is painful stimulus to the skin or

overfilling of visceral organs Elevated blood pressure can lead to stroke

Biofeedback

The use of instrumentation to monitor and feedback to the patient

Originally thought that the ANS could not be controlled voluntarily

Voluntary cortical control of visceral activities is possible through biofeedback

Physiological processes may be brought under voluntary control Visual imagery Diaphragmatic breathing (deep breathing to

slow the stress response)

Instrumentation used to train the patient EMG (electromyography) & temperature

trainer Tem. Training = hand warming through visual

imagery Leads to to vasodilation in the blood vessels of

the body EMG training = method of learning used

to achieve deep muscle relaxation through feedback