The Autonomic Nervous System

Flashcards about the Autonomic Nervous System

Autonomic nervous system

Regulates fundamental processes and maintains body homeostasis, also known as the Visceral Motor Division.

Sympathetic

Fight or Flight

Parasympathetic

Rest and Digest

Somatic Nervous System (SNS)

Operates under conscious control and controls skeletal muscles

Autonomic Nervous System (ANS)

Operates without conscious instruction, controls visceral effectors, and coordinates system functions

Target effectors Autonomic Nervous System

Innervates cardiac muscle, smooth muscle, and glands.

Somatic (motor) Nervous System

Upper neurons originate in the Cerebrum(Primary Motor cortex), control skeletal muscles (Voluntary), amount of myelination = neurons are highly myelinated.

Autonomic Nervous System

For autonomic activity originates in the Hypothalamus, controls visceral effectors (cardiac, respiratory, digestive, etc), amount of myelination = preganglionic neurons are lightly myelinated while postganglionic neurons are unmyelinated.

Sympathetic division

Increases alertness, metabolic rate, and muscular abilities; active during exertion, stress, or emergency also known as "Fight or flight".

Parasympathetic division

Reduces metabolic rate and promotes digestion, controls during resting conditions also known as "Rest and digest".

Preganglionic Neurons of the Sympathetic Division

Originate in the thoracolumbar(T1-L2) area and synapse in ganglia near spinal cord.

Postganglionic Neurons of the Sympathetic Division

Run from the ganglion (along the spinal cord) to the organs effected.

E division (Sympathetic Effects)

Exercise, excitement, emergency, embarrassment

Preganglionic neurons of the Parasympathetic Division

Originate in the brain stem and sacral segments of spinal cord; (craniosacral) and synapse in ganglia on or in the organ effected

Postganglionic neurons of the Parasympathetic Division

Run from the ganglia near or in the organ to the organ

D division (Parasympathetic Effects)

Digest, defecate, diuresis(urinating)

Enteric Nervous System(ENS)

The nervous system of the digestive tract.

Sympathetic Ganglia

Collection of MOTOR cell bodies outside of the CNS that carry out visceral motor functions.

Sympathetic Chain Ganglia

Are on both sides of vertebral column.

Sympathetic Collateral Ganglia

Contain ganglionic neurons that innervate tissues and organs in the abdominopelvic cavity.

Sympathetic Adrenal Medullae

Long preganglionic neurons that run all the way to the adrenal medulla. Adrenal Medulla are modified neurons – Neuroendocrine cells. Release neurotransmitters when stimulated: Epinephrine (mainly) and Norepinephrine (some)

Sympathetic Activation

Activation of the entire sympathetic division during a crisis (fight or flight situation).

Adrenergic neurons

Release Norepinephrine NE

Alpha 1 Receptor

Many nasal decongestants cause constriction of nasal blood vessels to decrease congestion because Alpha 1 is their mechanism of action…Thus resulting in a “clear head.”

Autonomic Varicosities

The connection between autonomic fibers and target effectors is not the same as the typical synapse, such as the neuromuscular junction.

Adrenal Medulla Releases Epinephrine

Picked up by blood stream and Stimulates Beta (β) Receptors.

Parasympathetic Division

Returns body to normal state "rest and digest" – Relaxation – Food processing - Energy absorption and storage.

Dual innervation

Most viscera receive nerve fibers from both parasympathetic and sympathetic divisions.

Visceral Reflexes

Provide automatic motor responses, can be modified, facilitated, or inhibited by higher centers, especially hypothalamus.

Short and Long Reflexes

Sensory input can stimulate either a short or a long reflex.

Sensor for Visceral Reflex ARC for High BP

Baroreceptor

Afferent Nerve for Visceral Reflex ARC for High BP

Glossopharyngeal(IX) Nerve

Integrator for Visceral Reflex ARC for High BP

Medulla Oblongata

Efferent Nerve for Visceral Reflex ARC for High BP

Vagus Nerve

Central Control of Autonomic Function with Cerebral Cortex Influence

Powerful emotions influence the ANS because of the connections between our limbic system and the hypothalamus.

Visceral Sensory

Delivers sensory information from Internal Organs Ex. Bladder is full

Broad Autonomic Effects of Nicotine

All Postganglionic neurons of the autonomic system are activated by ACh. Nicotine is ACh analog. Causes depolarization of neurons.

Sympathomimetic drugs

Enhance sympathetic activity. Act at postganglionic terminals / synapses: Sympathetic efferent pathway. Binds to adrenergic receptors and mimic norepinephrine. Increase production/release of norepinephrine

Sympatholytic Drugs

Suppress sympathetic activity. Work as an antagonist to adrenergic receptors. Block ability of norepinephrine or epinephrine to bind

Parasympathomimetic drugs

Enhance cholinergic(Parasympathetic) effects

Parasympatholytic(Anticholinergic) drugs

Inhibit cholinergic effects

Caffeine

Amplifies the sympathetic response by prolonging the effects of epinephrine and norepinephrine, turns down the receptor that inhibits acetylcholine.