8a Autonomic Nervous System Notes

8/12/2019 8a Autonomic Nervous System Notes

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AUTONOMIC NERVOUSSYSTEM


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Central nervous system (CNS) Peripheral nervous system (PNS)

Sensory (afferent)division

Motor (efferent) division

Somatic nervoussystem

Autonomic nervoussystem (ANS)

Sympatheticdivision

Parasympatheticdivision

Autonomic Nervous System (ANS)

Motor neurons that innervate smooth and cardiac muscle and glands.

Also called INVOLUNTARY NERVOUS SYSTEM.


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Figure 14.2 Comparison of motor neurons in the somatic and autonomic nervous systems.

Cell bodies in centralnervous system Peripheral nervous system

Neurotransmitterat effector

Effectororgans Effect

S O M A

T I C

N E R V O U S

S Y S T

E M

A U T O N O M I C N E R V O U S S Y S T E M

S Y M P A T H E T I C

P A R A S Y M P A T H

E T I C

Single neuron from CNS to effector organs

Heavily myelinated axon

ACh

Skeletal muscleStimulatory

Two-neuron chain from CNS to effector organs

Lightly myelinatedpreganglionic axons

Ganglion

Nonmyelinated

postganglionic axon

Epinephrine andnorepinephrine

ACh

ACh

Adrenal medulla Blood vessel

Lightly myelinatedpreganglionic axon

Ganglion

ACh

Nonmyelinatedpostganglionicaxon

ACh Smooth muscle(e.g., in gut), glands,cardiac muscle

Stimulatoryor inhibitory,dependingon neuro-transmitterand receptorson effector

organs

Acetylcholine (ACh) Norepinephrine (NE)

NE

+

+


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Somatic Nervous System vs.Autonomic Nervous System

Somatic NS Autonomic NS

Effectors

Neurons to effectors

Neurotransmitter(effects)

Ganglia ?

Skeletal Muscle Cardiac muscleSmooth muscleGlands

1 2: preganglionic neuron postganglionic neuron

Acetylcholine (stimulatory) Preganglionic: Ach

Postganglionic: Ach or NE (stimulatory or inhibitory)


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Central nervous system (CNS) Peripheral nervous system (PNS)

Sensory (afferent)division

Motor (efferent) division

Somatic nervoussystem

Autonomic nervoussystem (ANS)

Sympatheticdivision

Parasympatheticdivision

Dual innervation Visceral organs served by both divisions, but causeopposite effects

Autonomic Nervous System Divisions


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Dual Innervation


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Friday Night Scenario


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Role of the Parasympathetic Division

Promotes maintenance activities andconserves body energy Directs digestion, defecation Blood pressure, heart rate, and respiratory

rates are low Gastrointestinal tract activity high Pupils constricted Lenses accommodated for close vision


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Role of the Sympathetic Division

Exercise, excitement, emergency,embarrassment

Increased heart rate

Dry mouth Cold, sweaty skin Dilated pupils

Fight or flight system


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Role of the Sympathetic Division

During vigorous physical activityConstricts visceral blood vessels -> shunts blood to skeletal muscles and heartDilates bronchioles -> increases ventilation

Causes liver to release glucose


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Parasympathetic Sympathetic

Eye Eye

Salivaryglands

Brain stem

Cranial

Sympatheticganglia

Salivaryglands

Heart Cervical

Lungs

T1

Lungs

Heart

StomachThoracic

PancreasStomach

PancreasLiverand gall-bladderL1

Liver andgall-bladder

LumbarAdrenalgland

Bladder Bladder

Genitals Sacral Genitals

Skin*

Figure 14.3 The subdivisions of the ANS.


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Sympathetic NS Parasympathetic NS

Summary

Site of Origin

Fiber length

Ganglia location

Fight or Flight Rest and Digest

CNS:


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CN III Ciliaryganglion

Eye

Lacrimalgland

Pterygopalatineganglion

Nasalmucosa

Submandibularganglion

Submandibularand sublingualglands

Otic ganglionParotid gland

Heart

Cardiac andpulmonaryplexuses

Lung

Celiacplexus

Liver andgallbladder

Stomach

Pancreas

Largeintestine

Smallintestine

Rectum

Pelvicsplanchnicnerves

Inferiorhypogastricplexus

Urinarybladderand ureters

Genitalia (penis, clitoris, and vagina)

Preganglionic

PostganglionicCN Cranial nerveS Sacral nerve

CN VII

CN IXCN X

S 2

S 4

Figure 14.4 Parasympathetic division of the ANS.


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Cranial Part of Parasympathetic Division

Cell bodies in brain stem Preganglionic fibers in III,

VII, IX supply PSinnervation to head

supplies 90% of preganglionic PS fibersSupplies thoracic and abdominal viscera


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Sacral Part of Parasympathetic DivisionServes pelvic organs and distal half of large intestine


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Sympathetic (Thoracolumbar) Division

Preganglionicneurons arise inspinal cord segmentsT1 L 2

Preganglionic fiberssynapse close tospinal cord:

- in sympathetic trunk gagnlion or -collateral ganglion


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Adrenal medulla cells secrete NE and E are considered equivalent to postganglionic sympathetic neurons.


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Stimulus

Receptor in viscera

Visceral sensoryneuron

Integration center May be preganglionic

neuron (as shown)

May be a dorsal horninterneuron

May be within wallsof gastrointestinaltract

Motor neuron

(two-neuron chain) Preganglionic neuron Postganglionic neuron

Visceral effector

1

2

4

5

3

Response

Dorsal root ganglion

Spinal cord

Autonomic ganglion

Figure 14.7 Visceral reflexes.


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Cholinergic Receptors

Two types of receptors bind Ach:


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Nicotinic Receptors

Found on Sarcolemma of skeletal muscle cell Sympathetic and parasympathetic

postganglionic neurons Cells of the adrenal medulla

Effect of ACh at nicotinic receptors


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Nicotinic Receptors


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Muscarinic Receptors


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Adrenergic Receptors

Bind NE Two major classes

Effects of NE (& E)


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Adrenergic Receptors

Eff f ANS di i i


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Effects of ANS divisions:

Heart (rate)

Organ Sympathetic Parasymp.

Most bloodvessels

Heart

blood vessels

Eff t f ANS di i i


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Eye


Adipose

Glands (nasal,lacrimal, gastricpancreas)

Eff t f ANS di i i


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Respiratory


Digestivesystem

Urinary system

S h i T


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Sympathetic Tone

Sympathetic tone (vasomotor tone)

Sympathetic division controls bloodpressure

P h i T


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Parasympathetic Tone

Parasympathetic division normally dominates:

The sympathetic division can override theseeffects during times of stress

L li d V Diff Eff


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Localized Versus Diffuse Effects

Parasympathetic division: short-lived,highly localized control over effectors

Sympathetic division: longer-lasting,bodywide effects

Communication atLevels of ANS control


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Communication atsubconscious level

Cerebral cortex(frontal lobe)

Limbic system(emotional input)

Hypothalamus The boss

: Overallintegration of ANS

Brain stem(reticular formation, etc.)

Regulates pupil size, heart,blood pressure, airflow,

salivation, etc.

Spinal cord Reflexes for urination,defecation, erection,

and ejaculation

Figure 14.8 Levels of ANS control .


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8a Autonomic Nervous System Notes