Nerve activates contraction - PDE SAS

© 2012 Pearson Education, Inc.

PowerPoint® Lecture Slides

Prepared by Patty Bostwick-Taylor,

Florence-Darlington Technical College

C H A P T E R 7

The Nervous

System


PNS: Spinal Nerves

•There is a pair of spinal nerves at the level of

each vertebrae for a total of pairs

•Formed by the combination of the ventral and

dorsal roots of the spinal cord

•Named for the region from which they arise


Cervicalnerves

Thoracicnerves

Lumbarnerves

Sacralnerves

Ventral rami formcervical plexus(C1 – C5)

Ventral rami formbrachial plexus(C5 – C8; T1)

No plexusformed(intercostalnerves)(T1 – T12)

Ventral rami formlumbar plexus(L1 – L4)

Ventral rami formsacral plexus(L4 – L5; S1 – S4)

(a)

C1

T1

L1

2345678

23456

7

8

9

10

11

12

2

3

4

5

S1

234

Figure 7.25a


PNS: Anatomy of Spinal Nerves

•Spinal nerves divide soon after leaving the

spinal cord

• — branch of a spinal

nerve; contains both motor and sensory fibers

• rami — serve the skin

and muscles of the posterior trunk

• rami — form a complex of

networks (plexus) for the anterior

© 2012 Pearson Education, Inc. Figure 7.25b

Dorsal root

Dorsal rootganglion

Spinalcord

Ventralroot

Spinal nerve

Ventralramus

Dorsalramus

(b)


PNS: Spinal Nerve Plexuses

• – networks of nerves serving motor and sensory needs of the limbs

•Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions

•Four plexuses:

•Cervical

•Brachial

•Lumbar

•Sacral



• Plexus

•Originates from ventral rami in C1 – C5

• Important nerve is the nerve

•Areas served:

• diaphragm, shoulder and neck



• Plexus

•Originates from ventral rami in C5 – C8 and T1

• Important nerves:

•

•

•

•

•

• Areas served: shoulder, arm, forearm, and hand

© 2012 Pearson Education, Inc. Figure 7.26a

Axillary nerve

Humerus

Radialnerve

Musculocutaneous

nerve

Ulna

Radius

Ulnar nerve

Radial nerve(superficialbranch)

(a) The major nerves

of the upper limb

Median nerve



• Plexus

•Originates from ventral rami in L1 through L4


•

•

•Areas served:

• lower abdomen, anterior and medial thighs

© 2012 Pearson Education, Inc. Figure 7.26b

(b) Lumbar plexus,

anterior view

Femoral

Lateral

femoral

cutaneousObturator

Anterior

femoral

cutaneous

Saphenous



• Plexus

•Originates from ventral rami in L4 – L5 and S1 – S4


•

•

•Areas served:

• Lower trunk and posterior thigh

• Lateral and posterior leg and foot

•Gluteal muscles of hip area

© 2012 Pearson Education, Inc. Figure 7.26c

Superiorgluteal

Inferiorgluteal

Sciatic

Posteriorfemoralcutaneous

Commonfibular

Tibial

Sural (cut)

Deepfibular

Superficialfibular

Plantarbranches

(c) Sacral plexus, posterior view

© 2012 Pearson Education, Inc. Figure 7.2


PNS: Differences Between Somatic

and Autonomic Nervous Systems

Somatic Nervous

System

Autonomic Nervous

System

Nerves One-neuron; it

originates in the CNS

and axons extend to

the skeletal muscles

served

Two-neuron system

consisting of

preganglionic and

postganglionic

neurons

Effector organ Skeletal muscle Smooth muscle,

cardiac muscle,

glands

Subdivisions None Sympathetic and

parasympathetic

Neurotransmitter Acetylcholine Acetylcholine,

epinephrine,

norepinephrine


PNS: Somatic Nervous System

•Motor subdivision of PNS

•Affects skeletal muscles

•Also known as nervous system


PNS: Autonomic Nervous System

•Motor subdivision of the PNS

•Consists only of motor nerves

•Also known as the nervous system

•Regulates activities of cardiac and smooth

muscles and glands

•Two subdivisions

• division

• division


Central

nervous system Peripheral nervous system Effector organs

Somatic nervous system

Sympathetic

divisionAutonomic

nervous

system

Parasympathetic

division

KEY:

Preganglionic

axons

(sympathetic)

Postganglionic

axons

(sympathetic)

Myelination Preganglionic

axons

(parasympathetic)

Postganglionic

axons

(parasympathetic)

Acetylcholine

Acetylcholine

Acetylcholine

Epinephrine and

norepinephrineBlood

vesselAdrenal medulla

Acetylcholine

Ganglion

Ganglion

Norepinephrine

Skeletal

muscle

Smooth muscle

(e.g., in stomach)

Glands

Cardiac

muscle


(a) Parasympathetic Division

•Preganglionic neurons originate from the craniosacral

regions:

• The cranial nerves III, VII, IX, and X

• S2 through S4 regions of the spinal cord

•Due to site of preganglionic neuron origination, the

parasympathetic division is also known as the

craniosacral division

• Terminal ganglia are at the effector organs

•Neurotransmitter: acetylcholine


(b) Sympathetic Division

•Preganglionic neurons originate from T1 through L2

•Ganglia are at the sympathetic trunk (near the spinal cord)

•Short pre-ganglionic neuron and long post-ganglionic

neuron transmit impulse from CNS to the effector

•Neurotransmitters: norepinephrine and epinephrine

(effector organs)


Parasympathetic

Eye

Salivary

glands

Heart

Lungs

Cervical

Stomach

Thoracic

T1

Pancreas

Liver and

gall-

bladder

L1

Lumbar

Bladder

Genitals

Pelvic

splanchnic

nerves

Sacral nerves (S2 – S4)

Genitals

Bladder

Adrenal

gland

Liver

and gall-

bladder

Pancreas

Stomach

Heart

Lungs

Sympathetic

Eye

Skin

Salivary

glands

Brain stem

Cranial

nerves

Sympathetic

ganglia


Lateral horn of

gray matter

Sympathetic

trunk

Spinal

nerve

Sympathetic

trunk ganglion

Ventral root

Splanchnic

nerve

Collateral ganglion

(such as the celiac)

Gray ramus

communicans

Visceral effector organ

(such as small intestine)

White ramus

communicans

To effector:blood vessels,arrector pilimuscles, andsweat glandsof the skin

Dorsal ramus

of spinal nerve

Ventral ramus

of spinal nerve

Dorsal root

(b)

(a)

(c)


Sympathetic Functioning

•Sympathetic — “ ”

•Response to unusual stimulus

•Takes over to increase activities

•Remember as the “E” division

•exercise, excitement, emergency, and

embarrassment


Parasympathetic Functioning

• Parasympathetic — “ ” activites

•Conserves energy

•Maintains daily necessary body functions

•Remember as the “D” division

•digestion, defecation, and diuresis


Development Aspects of the Nervous

System

•No more neurons are formed after birth, but

growth and maturation continues for several

years

•The brain reaches maximum weight as a

young adult

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Nerve activates contraction - PDE SAS