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Homework

Student Study Guide Homework #3

Back of Study Guide in “Homework” section

Front and back

Homework #4 Handout

Both are due in lab this week

Week 3 Summary

Cranial and spinal nerves

Spinal nerve organization

Dermatomes

Plexuses

Spinal reflex components

Specific reflex types

Stretch reflex

Withdrawal reflex

Crossed extensor reflex

Thought Question’s

1. What are 2 ways to assess whether or not a particular spinal nerve has been damaged?

2. If you cut a dorsal root, what would the result be?

P E R I P H E R A L N E R V E D I S E A S E S

N E R V E R E G E N E R A T I O N

A N S

R E C E P T O R S A N D P H A R M A C O L O G Y

The Nervous System

Peripheral Nerve Regeneration

Possible if cell body has not been damaged

Axon underlying myelin sheath can regenerate

Figure 13.4 (1 of 4)

Endoneurium

Droplets

of myelin

Fragmented

axon

Schwann cells

Site of nerve damage

The axon

becomes

fragmented at

the injury site.

1


Schwann cell Macrophage Macrophages

clean out the

dead axon distal

to the injury.

2


Fine axon sprouts

or filaments

Aligning Schwann cells

form regeneration tube

3 Axon sprouts,

or filaments,

grow through a

regeneration tube

formed by

Schwann cells.


Schwann cell Site of new

myelin sheath

formation

4 The axon

regenerates and

a new myelin

sheath forms.

Single enlarging

axon filament

Neuritis

Inflammation of a nerve

Sciatica

Bell’s Palsy

Shingles

Herpes Zoster virus

Dorsal root ganglia

Consistent with dermatome

Vaccine

Multiple Sclerosis

Loss of myelin in CNS scleroses

Visual disturbances

Muscle weakness

Autoimmune disorder

Remissions

Progressive

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

Motor (efferent) division Sensory (afferent)

division

Somatic nervous

system

Autonomic nervous

system (ANS)

Sympathetic

division

Parasympathetic

division

Figure 14.1

Autonomic Nervous System (ANS)

Involuntary

Visceral reflex system

Sensory (afferent) neurons

Motor (efferent) neurons

Innervate smooth and cardiac muscle and glands

Operate via subconscious control

Skeletal muscle

Cell bodies in central

nervous system Peripheral nervous system Effect

+

+

Effector

organs

ACh

ACh Smooth muscle

(e.g., in gut),

glands, cardiac

muscle

Ganglion

Adrenal medulla Blood vessel

ACh

ACh

ACh

NE

Epinephrine and norepinephrine

Acetylcholine (ACh) Norepinephrine (NE)

Ganglion

Heavily myelinated axon

Lightly myelinated

preganglionic axon

Lightly myelinated preganglionic axons

Neuro-

transmitter

at effector

Unmyelinated

postganglionic

axon

Unmyelinated

postganglionic axon

Stimulatory

Stimulatory

or inhibitory,

depending

on neuro-

transmitter

and

receptors

on effector

organs

Single neuron from CNS to effector organs

Two-neuron chain from CNS to effector organs

SO

MA

TIC

NE

RV

OU

S

SY

ST

EM

AU

TO

NO

MIC

N

ER

VO

US

S

YS

TE

M

PA

RA

SY

MP

AT

HE

TIC

S

YM

PA

TH

ET

IC

Figure 14.2

Figure 14.7

Spinal cord

Dorsal root ganglion

Autonomic ganglion

Stimulus

Response

Visceral sensory

neuron

Integration center • May be preganglionic neuron (as shown) • May be a dorsal horn interneuron • May be within walls of gastrointestinal tract

Sensory receptor

in viscera

2

3

1

5 Visceral effector

Efferent pathway (two-neuron chain) • Preganglionic neuron • Ganglionic neuron

4

ANS Sensory Pathway

Visceral interoceptors (visceroceptors)

Osmolarity

Pressure

Temperature

Blood gases

Chemical composition of plasma and body fluids

ANS Sensory Pathway

Sensory neuron from organ to CNS

Cell body in dorsal root ganglion

Synapse with association neurons

Figure 12.32

Somatic sensory neuron

Dorsal root (sensory)


Visceral sensory neuron

Somatic motor neuron

Spinal nerve

Ventral root (motor)

Ventral horn (motor neurons)

Dorsal horn (interneurons)

Visceral motor neuron

Interneurons receiving input from somatic sensory neurons

Interneurons receiving input from visceral sensory neurons

Visceral motor (autonomic) neurons

Somatic motor neurons

ANS Motor Pathway

Two motor neurons between CNS and effector

Preganglionic neuron

Cell body in CNS

Postganglionic neuron

Cell body in autonomic ganglion (outside CNS)

Skeletal muscle

Cell bodies in central

nervous system Peripheral nervous system Effect

+

+

Effector

organs

ACh

ACh Smooth muscle

(e.g., in gut),

glands, cardiac

muscle

Ganglion


ACh

ACh

ACh

NE



Ganglion

Heavily myelinated axon

Lightly myelinated

preganglionic axon

Lightly myelinated preganglionic axons

Neuro-

transmitter

at effector

Unmyelinated

postganglionic

axon

Unmyelinated

postganglionic axon

Stimulatory

Stimulatory

or inhibitory,

depending

on neuro-

transmitter

and

receptors

on effector

organs

Single neuron from CNS to effector organs


SO

MA

TIC

NE

RV

OU

S

SY

ST

EM

AU

TO

NO

MIC

N

ER

VO

US

S

YS

TE

M

PA

RA

SY

MP

AT

HE

TIC

S

YM

PA

TH

ET

IC

Figure 14.2



division

Somatic nervous

system

Autonomic nervous

system (ANS)

Sympathetic

division

Parasympathetic

division

Figure 14.1

Divisions at a glance

Sympathetic

“Fight or Flight”

Epinephrine and acetylcholine

Thoracolumbar

Parasympathetic

“Rest and Digest”

Acetylcholine

Craniosacral

Dual Innervation

Salivary glands

Eye

Skin*

Heart

Lungs

Liver and gallbladder

Genitals

Pancreas

Eye

Lungs

Bladder


Pancreas

Stomach

Cervical

Sympathetic ganglia

Cranial

Lumbar

Thoracic

Genitals

Heart

Salivary glands

Stomach

Bladder

Adrenal gland

Parasympathetic Sympathetic

Sacral

Brain stem

L1

T1

Figure 14.3

Dual Innervation

Cranial Outflow

Nerve Ganglia (Terminal Ganglia)

Effector Organ(s)

Oculomotor (III) Ciliary Eye

Facial (VII) Pterygopalatine Submandibular

Salivary, nasal, and lacrimal glands

Glossopharyngeal (IX)

Otic Parotid salivary glands

Vagus (X) Within the walls of target organs

Heart, lungs, and most visceral organs

Sacral

Outflow

S2-S4

Within the walls of target organs

Large intestine, urinary bladder, ureters, and reproductive organs

Parasympathetic Division Outflow

Parasympathetic Division

Neurons leave spinal cord through ventral root

splanchnic nerves inferior hypogastric plexus

terminal ganglia

Pterygopalatine

ganglion

Eye

Lacrimal

gland

Nasal

mucosa

Ciliary

ganglion

Pterygopalatine

ganglion

Submandibular

ganglion Submandibular

and sublingual

glands

CN III

CN VII CN IX CN X

Otic ganglion

Parotid gland

Heart

Lung

Liver and

gallbladder

Stomach

Pancreas

Urinary

bladder

and ureters

Small

intestine

Large

intestine

S2

Pelvic

splanchnic

nerves

Genitalia

(penis,

clitoris, and vagina)

Rectum

Celiac

plexus

Inferior

hypogastric

plexus

Cardiac and

pulmonary

plexuses

S4

Preganglionic

Postganglionic

Cranial nerve

Figure 14.4

Parasympathetic

Division

= Craniosacral



division

Somatic nervous

system

Autonomic nervous

system (ANS)

Sympathetic

division

Parasympathetic

division

Figure 14.1

Figure 14.6

Superior

cervical

ganglion

Middle

cervical

ganglion

Inferior

cervical

ganglion

Sympathetic trunk

(chain) ganglia

Pons

L2

T1

White rami

communicantes

Liver and

gallbladder

Stomach

Spleen

Kidney

Adrenal medulla

Small

intestine

Large

intestine

Genitalia (uterus, vagina, and

penis) and urinary bladder

Celiac ganglion

Inferior

mesenteric

ganglion

Lesser splanchnic nerve

Greater splanchnic nerve

Superior

mesenteric

ganglion

Lumbar

splanchnic

nerves

Eye

Lacrimal gland

Nasal mucosa

Blood vessels;

skin (arrector pili

muscles and

sweat glands)

Salivary glands

Heart

Lung

Rectum

Cardiac and

pulmonary

plexuses

Preganglionic Postganglionic

Sacral

splanchnic

nerves

Sympathetic Division = Thoracolumbar

Sympathetic Division

Preganglionic neurons in T1 – L2

Thoracolumbar division

FYI: Lateral horns

Preganglionic fibers leave through ventral root

ventral rami white rami communicantes

sympathetic trunk (paravertebral) ganglia

Figure 14.5b (1 of 3)

To effector

Blood vessels

Skin (arrector

pili muscles

and sweat

glands)


Dorsal ramus of

spinal nerve

Dorsal root

Sympathetic

trunk ganglion

Lateral horn (visceral

motor zone)

Ventral root

Sympathetic trunk

Gray ramus

communicans White ramus

communicans

Ventral ramus of

spinal nerve

Figure 14.5a

Spinal cord

Dorsal root

Ventral root

Sympathetic

trunk ganglion

Sympathetic

trunk

Rib

Ventral ramus

of spinal nerve

Gray ramus

communicans

White ramus

communicans

Thoracic splanchnic nerves

(a) Location of the sympathetic trunk

Sympathetic Trunk Ganglia

Form longitudinal pathways adjacent to vertebral column

Each spinal nerve (except in cervical region)

has an associated ganglion

Figure 14.6

Superior

cervical

ganglion

Middle

cervical

ganglion

Inferior

cervical

ganglion

Sympathetic trunk

(chain) ganglia

Pons

L2

T1

White rami

communicantes

Liver and

gallbladder

Stomach

Spleen

Kidney

Adrenal medulla

Small

intestine

Large

intestine

Genitalia (uterus, vagina, and

penis) and urinary bladder

Celiac ganglion

Inferior

mesenteric

ganglion

Lesser splanchnic nerve

Greater splanchnic nerve

Superior

mesenteric

ganglion

Lumbar

splanchnic

nerves

Eye

Lacrimal gland

Nasal mucosa

Blood vessels;

skin (arrector pili

muscles and

sweat glands)

Salivary glands

Heart

Lung

Rectum

Cardiac and

pulmonary

plexuses

Preganglionic Postganglionic

Sacral

splanchnic

nerves

Sympathetic Division = Thoracolumbar

Sympathetic Trunks and Pathways

Upon entering a sympathetic trunk ganglion a preganglionic fiber may do one of the following:

1. Synapse with a ganglionic neuron within the same ganglion


To effector

Blood vessels

Skin (arrector

pili muscles

and sweat

glands)


Dorsal ramus of

spinal nerve

Dorsal root

Sympathetic

trunk ganglion

Lateral horn (visceral

motor zone)

Ventral root

Sympathetic trunk

Gray ramus

communicans White ramus

communicans

Ventral ramus of

spinal nerve

Synapse at the same level

(b) Three pathways of sympathetic innervation

1


2. Ascend or descend the sympathetic trunk to synapse in another trunk ganglion


To effector

Blood vessels

Skin (arrector

pili muscles

and sweat

glands)

Synapse at a higher or lower level


2


3. Pass through the trunk ganglion and emerge without synapsing


Splanchnic nerve

Collateral ganglion

(such as the celiac)

Target organ

in abdomen

(e.g., intestine)

Synapse in a distant collateral ganglion

anterior to the vertebral column


3

Figure 14.5a

Spinal cord

Dorsal root

Ventral root

Sympathetic

trunk ganglion

Sympathetic

trunk

Rib

Ventral ramus

of spinal nerve

Gray ramus

communicans

White ramus

communicans

Thoracic splanchnic nerves (a) Location of the sympathetic trunk

Division Origin of

Fibers Length of

Fibers Location

of Ganglia

Sympathetic Thoracolumbar region of the spinal cord

Short preganglionic and long postganglionic

Close to spinal cord

Parasympathetic Brain and sacral spinal cord (craniosacral)

Long preganglionic and short postganglionic

In visceral effector organs

Differences Between the Divisions

Neurotransmitters

Cholinergic fibers release the neurotransmitter ACh

All ANS preganglionic axons

All parasympathetic postganglionic axons

Adrenergic fibers release the neurotransmitter NE

Most sympathetic postganglionic axons

Exceptions: sympathetic postganglionic fibers secrete ACh at sweat glands and some blood vessels in skeletal muscles

Figure 14.2

+

ACh Smooth muscle

(e.g., in gut),

glands, cardiac

muscle

Ganglion


ACh

ACh

ACh

NE



Ganglion

Lightly myelinated

preganglionic axon

Lightly myelinated

preganglionic axons

Unmyelinated

postganglionic

axon

Unmyelinated postganglionic axon

Stimulatory

or inhibitory,

depending

on neuro-

transmitter

and

receptors

on effector

organs


AU

TO

NO

MIC

N

ER

VO

US

S

YS

TE

M

PA

RA

SY

MP

AT

HE

TIC

S

YM

PA

TH

ET

IC

Adrenal Medulla

“Sympathomimetic”

Receptors for Neurotransmitters

Cholinergic receptors for ACh

Adrenergic receptors for NE

Cholinergic Receptors

Two types of receptors bind ACh

1. Nicotinic

2. Muscarinic

Named after drugs that bind to them and mimic ACh effects

Remember G-protein linked receptors and second messengers?


Nicotinic receptors Blocked with curare

Effect of ACh at nicotinic receptors Always stimulatory


Muscarinic

Blocked by atropine

Effect of ACh at muscarinic receptors

Can be either inhibitory or excitatory

Depends on the receptor type of the target organ

Correct 2d. acetylcholine is not always stimulatory. It IS always stimulatory at nicotinic receptors.

Table 14.2

Adrenergic Receptors

Two types

Alpha () (subtypes 1, 2)

Beta () (subtypes 1, 2, 3)

Effects of NE depend on which subclass of receptor predominates on the target organ

Table 14.2

Cardiovascular Pharmacology

Heart

1 - Excitatory in heart

increases heart rate, conduction velocity, and contraction strength

Major blood vessels

2 – Inhibitory

Vasodilation

1 – Excitatory

Vasoconstriction

Cardiovascular Pharmacology

Adrenergic blockers

Used to treat hypertensive disease

blockers - produce vasodilation

1 blockers - decrease heart rate and blood pressure

Table 14.3

Interactions of the Autonomic Divisions

Most visceral organs have dual innervation

Dynamic and precise control of visceral activity

Sympathetic division increases heart and respiratory rates, and inhibits digestion and elimination

Parasympathetic division decreases heart and respiratory rates, and allows for digestion and the discarding of wastes

Salivary glands

Eye

Skin*

Heart

Lungs


Genitals

Pancreas

Eye

Lungs

Bladder


Pancreas

Stomach

Cervical

Sympathetic ganglia

Cranial

Lumbar

Thoracic

Genitals

Heart

Salivary glands

Stomach

Bladder

Adrenal gland

Parasympathetic Sympathetic

Sacral

Brain stem

L1

T1

Figure 14.3

Questions?

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