BIO 220 Ch 16: Autonomic Nervous System

Autonomic Nervous System

• Somatic nervous system (SNS)

○ Voluntary control of _______ muscles

• Autonomic nervous system (ANS)

○ Involuntary control of _______ effectors

- Smooth muscle, cardiac muscle, glands, adipocytes

○ __________ contains integrative centers

○ Motor neurons of CNS synapse on visceral motor neurons in autonomic ganglia

skeletal, visceral, Hypothalamus

Autonomic Nervous System

• Visceral motor neurons

○ Preganglionic neurons in brainstem and spinal cord

○ Preganglionic fibers—_____ of preganglionic neurons

- After leaving CNS, they synapse on ganglionic neurons (postganglionic neurons)

○ _________ ganglia

- Contain many ganglionic neurons that innervate visceral effectors

- Postganglionic fibers—axons of ganglionic neurons

axons, Autonomic

Autonomic Nervous System

• Responses to increased sympathetic activity

1. Heightened mental alertness

2. Increased metabolic rate

3. Activation of energy reserves

4. Reduced digestive and urinary functions

5. Increased respiratory rate and dilation of respiratory passageways

6. Increased heart rate and blood pressure

7. Activation of sweat glands

Two divisions of ANS

Sympathetic and Parasympathetic

Sympathetic division "Fight or flight"

- Prepares the body to deal with emergencies

- ________ alertness, metabolic rate, and muscular abilities

- Most active during times of stress, exertion, or emergency

- Also called the _________ division

Increases, thoracolumbar

Parasympathetic division "Rest and digest"

- ________ energy and maintains resting metabolic rate

- Most active during resting conditions

- Also called the _________ division Conserves, craniosacral

Sympathetic and parasympathetic divisions

○ Usually have _______ effects

- If sympathetic division causes excitation, the parasympathetic causes inhibition

○ May work _________, with each controlling one stage of a complex process

○ May also work independently

- Only one division innervates some structures

opposing, together

Sympathetic division (thoracolumbar division)

○ Short preganglionic fibers in ________ and ________ segments of spinal cord

- Preganglionic neurons located between segments T1 and L2

- Cell bodies in _______ gray horns

- Axons enter anterior (ventral) roots - white ramus ...

○ Ganglionic neurons in ganglia near spinal cord

○ Long postganglionic fibers to target organs

thoracic, lumbar, lateral

Ganglionic neurons synapse in three locations:

1. Sympathetic chain ganglia

2. Collateral ganglia

3. Adrenal medullae

Sympathetic chain ganglia

○ On both sides of __________ column (paravertebral)

○ One preganglionic fiber synapses on many ganglionic neurons

○ Each ganglion innervates a particular effectors in

- Body wall

- _________ cavity

- Head

- Neck

- Limbs

vertebral, Thoracic

The Sympathetic Division

• Collateral ganglia

○ _________ to vertebral bodies (prevertebral)

○ Contain ganglionic neurons that innervate ___________ tissues and viscera

- ________ ganglion

- Superior mesenteric ganglion

- Inferior mesenteric ganglion

Anterior, abdominopelvic, Celiac

The Sympathetic Division

○ There are three collateral ganglia

Celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion

Celiac ganglion

Innervates stomach, duodenum, liver, gallbladder, pancreas, spleen, and kidney

Superior mesenteric ganglion

Innervates small intestine and initial segments of large intestine

Inferior mesenteric ganglion

Innervates terminal portions of large intestine, the kidney, urinary bladder, and sex organs

The Sympathetic Division

• Collateral ganglia (unpaired)

○ Preganglionic fibers

- Pass through sympathetic chain without ________

- Form __________ nerves

- In _________ wall of abdominal cavity

synapsing, splanchnic, posterior

The Sympathetic Division

• Adrenal medulla

○ ________ of each adrenal gland

○ Modified sympathetic ganglion

○ Ganglionic neurons have very short axons

○ When stimulated, they release ___________ into bloodstream (not at synapse)

- Epinephrine and norepinephrine (adrenaline)

- Function as hormones to affect target cells throughout body

Center, neurotransmitters

Fibers in sympathetic division

○ __________ fibers (cell bodies in lateral gray horn)

- Relatively short

- Ganglia located near spinal cord

○ Postganglionic fibers

- Relatively long, except at ________ medullae

Preganglionic, adrenal

The Sympathetic Division

• Preganglionic neurons are limited to spinal cord segments __-__

○ These spinal nerves have

- White rami (________ preganglionic fibers)

- Gray rami (unmyelinated postganglionic fibers)

○ Preganglionic fibers through white rami - innervate ________ _______ viscera

○ Postganglionic fibers innervate thoracic cavity through sympathetic nerves

○ Postganglionic fibers innervate dorsal/ventral rami through gray rami

T1, L2, myelinated, abdominal pelvic

The Sympathetic Division

• Paths of unmyelinated postganglionic fibers depend on targets

○ Those that control visceral effectors in body wall, head, neck, or limbs

- Enter ______ ramus

- Return to spinal nerve for distribution Dorsal/ventral rami

- Innervate sweat glands, arrector pili muscles, etc.

○ Those that innervate visceral organs in thoracic cavity such as heart and lungs

- Form ________ (sympathetic nerves)

gray, bundles

The sympathetic division can change the activities of specific effectors

○ Sympathetic activation

○ Occurs during a crisis

○ The entire division responds

○ Controlled by sympathetic centers in __________

○ Affects peripheral tissues and CNS _______

hypothalamus, activity

Changes caused by sympathetic activation

○ ________ alertness

○ Feelings of energy and euphoria

○ _________ blood pressure, heart rate, breathing rate, and depth of respiration

○ Elevation in muscle ______

○ Mobilization of energy reserves

Increased, Increased, tone

Sympathetic Activation and Neurotransmitter Release

○ __________ Sympathetic fibers release acetylcholine (ACh) at the synapse with ganglionic neurons

- These are cholinergic synapses

- Effect is always excitatory

○ _____________ Sympathetic fibers release norepinephrine at the neuroeffector junction

- These terminals are adrenergic

Preganglionic, Postganglionic

Sympathetic Varicosities

• Postganglionic neurons release neurotransmitters at target ______.

○ Each swollen segment is a ________

○ Packed with neurotransmitter vesicles

○ Membrane receptors scattered across target _____

organs, varicosity, cells

Sympathetic Effects

• Plasmalemma Receptors and Sympathetic Function

○ There are two classes of __________ adrenergic membrane receptors

- _______ receptors

□ Stimulated by epinephrine

□ Stimulated by norepinephrine

- Beta receptors

□ Stimulated by __________

plasmalemma, Alpha, epinepherine

Sympathetic Division Summary

• Consists of parallel chains on either side of the spinal cord (T1 - L2), shows considerable divergence

○ Preganglionic fibers are short and extend from the spinal cord to the __________ ______

- Release ACh

○ Postganglionic fibers are long and extend from the ganglion to the ______ _______

- Most release NE

- Effector response depends on the presence of either alpha or beta receptors

sympathetic chain, body organs

Autonomic Nervous System

Responses to increased parasympathetic activity

1. _________ metabolic rate

2. _________ heart rate and blood pressure

3. Increased secretion by salivary and digestive glands

4. Increased motility and blood flow in digestive tract

5. _________ of urination and defecation

Decreased, Decreased, Stimulation

Parasympathetic division (craniosacral division)

○ Long preganglionic fibers in ________ and ______ segments of spinal cord

- Autonomic nuclei are in all parts of brainstem and lateral horns of S2-S4

○ Preganglionic neurons do not diverge as much as the sympathetic division

○ Short postganglionic fibers in (intramural) or near (terminal) target _____

brainstem, sacral, organ

Organization of parasympathetic division

○ Parasympathetic preganglionic fibers leave brain in cranial _______

- CN ____ (oculomotor - to the intrinsic eye muscles, pupil, and lens)

- CN ___ (facial - to the lacrimal (tear) glands and salivary glands)

- CN __ (glossopharyngeal - to the parotid salivary glands)

- CN __ (vagus - to the visceral organs of the thoracic cavity and abdominal cavity = 75% of parasym. output)

○ Preganglionic fibers leave the sacral region via:

- Pelvic nerves S2-S4 to the visceral organs in the inferior portion of the abdominopelvic cavity

nerves, III, VII, IX, X

Major effects of parasympathetic division

○ ________ of pupils and focusing on near objects

○ Secretion by digestive glands

○ Absorption and use of nutrients by peripheral cells

○ Changes associated with sexual ________

○ _________ smooth muscle activity in digestive tract

○ Stimulation and coordination of defecation

○ Contraction of urinary bladder during urination

○ Constriction of ________ passageways

○ Reduction in heart rate and force of contraction

Constriction, arousal, Increased, respiratory

Parasympathetic Effects

• All parasympathetic neurons release ____ (cholinergic)

○ Effects on postsynaptic cell vary widely

- Due to different types of receptors

○ Effects of parasympathetic stimulation of cholinergic receptors are __________ and short lived

- Most ACh is _________ at synapse by acetylcholinesterase (AChE)

- ACh that diffuses into surrounding tissues is inactivated by tissue _____________

Ach, localized, inactivated, cholinesterase

Parasympathetic Effects

• Plasmalemma Receptors and Responses

○ Two types of Cholinergic receptors (ACh) are found on the postsynaptic _____________:

1. Nicotinic receptors

- On ________ cells of sympathetic and parasympathetic divisions

- Also occur at neuromuscular junctions of SNS

- Exposure to ACh causes _______ of ganglionic neuron or muscle fiber

plasmalemmae, ganglion, excitation

Parasympathetic Effects

• Cholinergic receptors

2. Muscarinic receptors

- At _________ neuromuscular or neuroglandular junctions in

- __________ division

- Effects are longer lasting than _________ receptors

- Response is excitatory or inhibitory depending on activation or inactivation of specific enzymes

cholinergic, parasympathetic, nicotinic

The Parasympathetic Division Summary

• Involves CN III, CN VII, CN IX, and CN X & sacral segments S2 to S4

• All parasympathetic neurons are cholinergic

○ Release of ACh stimulates ________ receptors on ganglionic neurons

○ Effect is always excitatory

○ Release of ACh on neuroeffector _________ stimulates muscarinic receptors

• Effect can be excitatory or inhibitory

• Parasympathetic stimulation are usually brief & localized

• Parasympathetic nerves innervate

○ _______, thoracic, abdominal, and pelvic organs

nicotinic, junctions, Head

Summary of ANS Divisions

• Sympathetic division has widespread effects

○ Visceral motor nuclei are associated with lateral gray horn T1-L2

○ ___ sets of sympathetic chain ganglia, ______ collateral ganglia, and ____ adrenal medullae

○ Short preganglionic fibers, long postganglionic fibers

○ Extensive _________

○ Preganglionic neurons release ACh

most postganglionic fibers release NE

Two, three, two, divergence

Summary of ANS Divisions

• Parasympathetic division has specific effects

○ Visceral motor nuclei are associated with cranial nerves III, VII, IX, and X, and with __-__

○ Ganglionic neurons are located in ganglia within or next to target organs

○ One-fifth the _________ of sympathetic division

○ All neurons are cholinergic

○ Effects are generally ____ and restricted

S2, S4, divergence, brief

Dual innervation

○ Most vital organs are innervated by both _______ of ANS

○ Commonly opposing (antagonistic) effects

divisions

Anatomy of dual innervation

○ Autonomic plexuses

- Nerve networks in the ________ and __________ cavities

- Formed by mingled sympathetic __________ fibers and parasympathetic preganglionic fibers

- Travel with blood and lymphatic vessels that supply visceral organs

thoracic, abdominopelvic, postganglionic

Dual Innervation

• Autonomic tone (baseline firing frequency)

○ Autonomic motor neurons have ______ level of activity

- Even without stimulation

○ Important aspect of ANS function

○ Because nerves maintain background level of activity, they can increase or decrease activity

- Provides greater range of control

○ Significant where ______ ________ occurs

- More important where it does not occur

resting, dual innervation

Dual Innervation

• The ______ receives dual innervation

○ ACh released by parasympathetic postganglionic fibers slows heart rate

○ NE released by varicosities of sympathetic division accelerates heart rate

- Small amounts of both are released continuously, producing autonomic _____

○ Parasympathetic division dominates at rest

○ Crisis speeds heart rate by stimulating sympathetic and ________ parasympathetic nerves

heart, tone, inhibiting

Dual Innervation

• Some organs are innervated by only one division

○ Example: sympathetic control of blood vessel diameter

○ NE is released from sympathetic fibers at smooth muscle cells in blood vessel _____

- Sympathetic tone keeps muscles partially _________

○ When more blood flow is needed,

- Rate of NE release ___________

- Smooth muscle cells relax and blood vessel ______

walls, contracted, decreases, dilates