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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