Download autonomic and somatic nervous systems

Nerve Tissue & The
Nervous System
David L. McWhorter, Ph.D.
NERVOUS SYSTEM ORGANIZATION
CONSISTS OF TWO OVERLAPPING
PAIRS OF SUBSYSTEMS…
CENTRAL AND PERIPHERAL
NERVOUS SYSTEMS WHICH ARE
DEFINED BY LOCATION:

1.


CNS INCLUDES THE BRAIN AND
SPINAL CORD
PNS INCLUDES ALL OTHER NERVE
TISSUE (CRANIAL NERVES,
PERIPHERAL NERVES, GANGLIA,
NERVE PLEXUSES)
AUTONOMIC AND SOMATIC
NERVOUS SYSTEMS WHICH ARE
DEFINED BY FUNCTION & HAVE CNS
AND PNS COMPONENTS:
2.


ANS CONTROLS INVOLUNTARY
VISCERAL FUNCTIONS (EG, SMOOTH
MUSCLE CONTRACTION)
SOMATIC NERVOUS SYSTEM
CONTROLS SOMATOSENSORY
PERCEPTION (EG, TOUCH, HEAT,
COLD) AND VOLUNTARY
SOMATOMOTOR FUNCTIONS (EG,
SKELETAL MUSCLE CONTRACTION)
There are two cell types that
make up nervous tissue…
1.
2.
Neurons
Glial cells
NERVOUS SYSTEM CELLS: NEURONS
FUNDAMENTAL
STRUCTURAL &
FUNCTIONAL UNIT OF
NERVOUS SYSTEM

> 100 MILLION

SPECIALIZED TO RECEIVE,
INTEGRATE, & TRANSMIT
ELECTROCHEMICAL
MESSAGES

NERVE IMPULSES OR
ACTION POTENTIALS


THREE MAIN PARTS:
1.
2.
3.
CELL BODY
DENDRITES
AXON
MAIN TYPES OF NEURONS
(NUMBER OF NEURITES [PROCESSES])

BIPOLAR



MULTIPOLAR




1 DENDRITE AND 1 AXON
UNCOMMON AND FOUND ONLY IN
SPECIAL SITES: COCHLEAR &
VESTIBULAR GANGLIA OF CN XIII,
OLFACTORY NERVE, RETINA
MOST NEURONS IN BODY
MORE THAN TWO PROCESSES
EXAMPLES INCLUDE: MOTOR
NEURONS AND AUTONOMIC
NEURONS
PSEUDOUNIPOLAR

SINGLE PROCESS CLOSE TO
CELL BODY DIVIDED INTO 2
BRANCHES




PERIPHERAL PROCESS (top)
CENTRAL PROCESS
CELL BODY NOT INVOLVED IN
IMPULSE CONDUCTION
FOUND IN SPINAL DORSAL ROOT
GANGLIA AND SENSORY
GANGLIA OF CRANIAL NERVES V,
VII, IX, AND X
NEURON: CELL BODY (SOMA, PERIKARYON
[G. AROUND + NUCLUEUS)



CONTAINS NUCLEUS
AND SURROUNDING
CYTOPLASM,
EXCLUSIVE OF CELL
PROCESSES
NUCLEUS IS LARGE,
CENTRAL, AND
EUCHROMATIC
(PROMINENT
NUCLEOLUS)
ABUNDANT FREE AND
RER-ASSOCIATED
POLYRIBOSOMES
APPEAR AS CLUMPS
OF BASOPHILIC
MATERIAL
COLLECTIVELY CALLED
NISSL BODIES
CNS CELL BODIES
(POLYGONAL SHAPE)
PNS CELL BODIES
(ROUND SHAPE)
NEURON: DENDRITES (G., TREE)



USUALLY SHORT AND DIVIDE LIKE
BRANCHES OF A TREE
PRINCIPAL SIGNAL RECEPTION AND
PROCESSING SITES ON NEURONS
MOST SYNAPSES BETWEEN NEURONS
OCCUR AT DENDRITIC SPINES


SMALL "DOOR KNOB" SHAPED
EXTENSIONS FROM THE SURFACES OF
THE DENDRITIC PROCESSES
INVOLVED IN PLASTIC CHANGES THAT
UNDERLIE ADAPTATION, LEARNING, AND
MEMORY
NEURON: AXON (G., AXIS)


USUALLY VERY LONG, SINGLE
PROCESS WITH A CONSTANT
DIAMETER
SPECIALIZED TO CONDUCT NERVE
IMPULSES TO OTHER CELLS



ORIGIN HAS A SHORT PYRAMIDSHAPED REGION CALLED THE AXON
HILLOCK
DISTAL PORTION USUALLY BRANCHED
(COLLATERAL BRANCHES) AND ITS
TERMINAL PORTIONS ARE CALLED END
BULBS OR BOUTONS


MAY ALSO RECEIVE INFORMATION FROM
OTHER NEURONS…MAINLY MODIFIES
TRANSMISSION OF ACTION POTENTIALS
TO OTHER NEURONS
FORM INTERACTIONS WITH OTHER
NEURONS OR NON-NERVE CELLS
CALLED SYNAPSES
PLASMA MEMBRANE AND CYTOPLASM
OF AN AXON ARE CALLED AXOLEMMA
AND AXOPLASM, RESPECTIVELY
DENDRITE VERSUS AXON
HISTOLOGY


ENTIRE AXON USUALLY NOT VISIBLE IN
SECTIONED MATERIAL
ABSENCE OF NISSL-RELATED BASOPHILIA AT
ORIGIN DISTINGUISHES AXON FROM DENDRITES
NERVOUS SYSTEM CELLS: NEUROGLIA
(GLIAL CELLS OR SUPPORTING CELLS)

CNS NEUROGLIA:

ASTROCYTES



OLIGODENDROCYTES


PHAGOCYTIC CELLS
EPENDYMAL CELLS


FORM MYELIN IN CNS
MICROGLIA


MOST POPULOUS GLIAL
CELL
PART OF BLOOD- BRAIN
BARRIER
HELP MAKE UP
CHOROID PLEXUS
PNS NEUROGLIA:

SCHWANN CELLS

FORM MYELIN IN PNS

CNS TERMS
NUCLEUS IS A GROUP OF CELL BODIES
INVOLVED IN A COMMON FUNCTION


TRACT: (PATHWAY)



LOCATED IN THE GRAY MATTER
COLLECTIONS OF MYELINATED AXONS
CONNECTING NEIGHBORING OR DISTANT
NUCLEI
LOCATED IN THE WHITE MATTER
MENINGES:

C.T. LAYERS BETWEEN CNS AND SKULL &
VERTEBRAL CANAL
CNS TERMS: BLOOD-BRAIN
BARRIER
CNS TISSUE
RECEIVES OXYGEN
AND NUTRIENTS
FROM CAPILLARIES
IN PIA MATER
STRUCTURAL AND
FUNCTIONAL
BARRIER THAT
PROTECTS CNS
NEURONS FROM
MANY EXTRANEOUS
INFLUENCES: (i>o)


1.
2.
3.
NONFENESTRATED
ENDOTHELIAL
CELLS JOINED BY
TIGHT JUNCTIONS
Basement
membrane
(basolamina)
CYTOPLASMIC
PNS COMPONENTS

PERIPHERAL (SPINAL) NERVES (31 PAIRS):






8-CERVICAL
12-THORACIC
5-LUMBAR
5-SACRAL
1-COCCYGEAL
CRANIAL NERVES (12 PAIRS)



EMERGE FROM FORAMINA IN SKULL &
COVERED BY MENINGES
NUMBERED I THROUGH XII FROM ANTERIOR
TO POSTERIOR
11 OF 12 PAIRS ARISE FROM BRAIN


GANGLIA:


CLUSTERS OF NEURON CELL BODIES
TWO MAJOR TYPES
1.
2.

11TH PAIR ARISES MOSTLY FROM SUPERIOR
PART OF SPINAL CORD
CRANIOSPINAL
AUTONOMIC
NERVE PLEXUSES:


NETWORK OF PERIPHERAL NERVES
THREE MAJOR NERVE PLEXUSES…
PERIPHERAL (SPINAL) NERVE (31
PAIRS)
ARISES FROM SPINAL
CORD VIA NERVE
ROOTLETS


CONVERGE TO FORM
TWO NERVE ROOTS:
1.
2.
VENTRAL ROOT
DORSAL ROOT
VENTRAL AND DORAL
ROOTS UNITE TO
FORM PERIPHERAL
NERVE
PERIPHERAL NERVE
DIVIDES INTO TWO
RAMI:


1.
2.
ANTERIOR RAMUS
POSTERIOR RAMUS
PERIPHERAL NERVES
CONSISTS OF:


BUNDLES OF NERVE
FIBERS (AXONS) HELD
TOGETHER BY C.T.
SHEATHS
NEURONS BETWEEN SENSORY
AND MOTOR NEURONS THAT
GOVERN COORDINATED ACTIVITY
PERIPHERAL (SPINAL) NERVE: FOUR
TYPES OF NERVE FIBERS
SOMATIC SENSORY AND MOTOR
FIBERS:

1.
GENERAL SOMATIC AFFERENT (GSA)
FIBERS

2.
TRANSMIT SENSATIONS FROM BODY
TO SPINAL CORD (EG., PAIN,
TEMPERATURE, TOUCH, & PRESSURE)
GENERAL SOMATIC EFFERENT (GSE)
FIBERS

TRANSMIT IMPULSES TO SKELETAL
MUSCLES
VISCERAL SENSORY AND MOTOR
FIBERS:

3.
GENERAL VISCERAL AFFERENT
(GVA) FIBERS

4.
TRANSMIT REFLEX OR PAIN FROM
MUCOUS MEMBRANES, GLANDS, AND
BLOOD VESSELS BACK TO CNS
GENERAL VISCERAL EFFERENT
(GVE) FIBERS

TRANSMIT IMPULSES TO SMOOTH
AND CARDIAC MUSCLE AND
GLANDULAR TISSUES
PERIPHERAL
(SPINAL) NERVE:
HISTOLOGY

LONGITUDINAL OR
OBLIQUE SECTION:


“WAVINESS” OF BUNDLES
LIGHTER STAINING THAN
CONNECTIVE TISSUE


DUE TO MYELIN
CROSS-SECTION:


BUNDLES OF DARKSTAINING AXONS
SURROUNDED BY
LIGHT/ABSENT MYELIN
SHEATH
PRESENCE OF DARKSTAINING CT SHEATHS



ENDONEURIUM
PERINEURIUM
EPINEURIUM
PNS: CRANIOSPINAL GANGLIA


DORSAL ROOT
GANGLIA (SPINAL
GANGLIA)
CRANIAL NERVE
GANGLIA
GANGLIA HISTOLOGY


CELL BODIES
ARE
USUALLY
ROUND
WHAT ARE
THE
“YELLOWBROWN
PATCHES?”
PNS: AUTONOMIC
GANGLIA (3)
SYMPATHETIC GANGLIA:



PARAVERTEBRAL (CHAIN) GANGLIA
PREVERTEBRAL GANGLIA
PARASYMPATHETIC GANGLIA:


WITHIN WALL OF ORGAN THEY SUPPLY
AUTONOMIC NERVOUS SYSTEM

DESCRIBED AS “VISCERAL
MOTOR (EFFERENT) SYSTEM”
THAT SUPPLIES:





CONSISTS OF TWO NEURONS
THAT SYNAPSE IN AN
AUTONOMIC GANGLION
CELL BODY OF FIRST NEURON
IS IN CNS


PREGANGLIONIC FIBER
CELL BODY OF SECOND
NEURON IS IN PNS
(AUTONOMIC GANGLION)


SMOOTH MUSCLE
CONDUCTION SYSTEM OF
HEART
GLANDS
POSTGANGLIONIC FIBER
ANS SUBDIVIDED INTO:


SYMPATHETIC NERVOUS
SYSTEM
PARASYMPATHETIC NERVOUS
SYSTEM
ANS: SYMPATHETIC
NERVOUS SYSTEM

PREGANGLIONIC CELL BODIES:


SPINAL CORD GRAY MATTER (T1-L3 SPINAL
SEGMENTS)
POSTGANGLIONIC CELL BODIES:

PARAVERTEBRAL & PREVERTEBRAL
GANGLIA
ANS: PARASYMPATHETIC
NERVOUS SYSTEM

PREGANGLIONIC
CELL BODIES:

BRAINSTEM GRAY
MATTER


GRAY MATTER OF
SPINAL SEGMENTS
S2-S4


CRANIAL DIVISION
SACRAL DIVISION
POSTGANGLIONIC
CELL BODIES:


CRANIAL GANGLIA
TARGET ORGANS
ANS SUMMARY
SOMATIC NERVOUS SYSTEM

CONTROLS SOMATOSENSORY PERCEPTION



CONTROLS SOMATOMOTOR (VOLUNTARY)
FUNCTIONS



TOUCH, HEAT, COLD
TAKES 3 neurons
SKELETAL MUSCLE CONTRACTION
Takes 2 neurons
ACETYLCHOLINE IS MOST COMMON SOMATIC
NEUROTRANSMITTER
CONCLUSION: IMPORTANT POINTS OF
LECTURE (SLIDE 1 OF 2)










WHAT DO BRAIN AND SPINAL CORD COMPRISE?
WHAT DO CRANIAL NERVES, PERIPHERAL NERVES,
GANGLIA, NERVE PLEXUSES COMPRISE?
WHAT ARE COLLECTIONS OF CELL BODIES CALLED IN
THE CNS? PNS?
WHAT ARE COLLECTIONS OF AXONS IN THE CNS? PNS?
WHAT ARE THE TWO CHIEF COMPONENTS OF THE
BLOOD BRAIN BARRIER?
WHAT ARE A NETWORK OF PERIPHERAL NERVES? LIST
THE FIRST TWO YOU WILL ENCOUNTER?
WHAT IS THE CHIEF COMPONENT OF A PERIPHERAL
NERVE?
WHICH CELL(S) MAKE MYELIN IN THE CNS AND PNS?
WHICH STRUCTURE CONTAINS ONLY SENSORY FIBERS?
MOTOR FIBERS? BOTH SENSORY AND MOTOR?
WHERE ARE SENSORY CELL BODIES LOCATED?
CONCLUSION: IMPORTANT POINTS OF
LECTURE (SLIDE 2 OF 2)






WHAT IS LOCATED IN THE SPINAL CORD GRAY MATTER
(T1-L3 SPINAL SEGMENTS)?
WHAT IS THE SECOND NEURON OF THE MOTOR
COMPONENT OF THE ANS CALLED AND WHERE IS IT
LOCATED?
WHERE ARE THE POSTGANGLIONIC SYMPATHETIC CELL
BODIES LOCATED?
WHAT IS LOCATED IN THE MEDULLA AND MIDBRAIN
NUCLEI (CNS GRAY MATTER) AND GRAY MATTER OF
SPINAL SEGMENTS S2-S4?
WHERE ARE POSTGANGLIONIC PARASYMPATHETIC CELL
BODIES LOCATED?
WHICH AUTONOMIC FIBER TYPE HAS A SHORT
PREGANGLIONIC AXON AND A LONG POSTGANGLIONIC
AXON THAT SECRETES NOREPINEPHRINE?