Transcript ANATOMICAL ORGANIZATION of the NERVOUS SYSTEM

ORGANIZATION OF THE
NERVOUS SYSTEM
FUNCTIONS
SENSORY
 MOTOR
 COGNITIVE

ANATOMICAL ORGANIZATION of the
NERVOUS SYSTEM
Nervous
System
CNS
PNS
ANS
BRAIN
CRANIAL
NERVES
SYMPATHETIC
SPINAL
CORD
SPINAL
NERVES
PARASYMPATHETIC
Central Nervous System (CNS)
Unpaired, bilaterally symmetrical
structures extending along the longitudinal
axis of the midsagittal plane of the body.
 Structures arising directly from the neural
tube.
 Includes:

Brain
Spinal cord
Peripheral Nervous System
(PNS)
 Made up of transmission pathways
carrying information between the CNS and
external/internal environments.
 Afferent (sensory) pathways:

Carry information to the CNS.

Efferent (motor) pathways:
Carry information from the CNS.
Peripheral Nervous System

Includes:
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)
Also includes sensory receptors in skin
and wall of gut tube as well as in tendons
and skeletal muscles.
 Also includes motor end plates between
motor neurons and skeletal muscle fibers.

Autonomic Nervous System
May be considered a subdivision of the
PNS.
 Entirely motor.
 Innervates smooth muscle and glands
(viscera)

ANS Subdivisions

Sympathetic system
(fight or flight)
Also called thoracolumbar

Parasympathetic system
(feed and breed)
Also called craniosacral
Parts of a Neuron

Cell body:
Trophic unit
Perikaryon

Dendrites:
Receptive unit

Axon:
Conductive unit
Cell Body
 That
part of a neuron that encloses
the nucleus and other organelles
necessary to maintain and repair
neuron.
Cell Body Organelles
Nucleus
 Golgi apparatus
 RER

Ribosomes
=Nissl substance
Dendrites
Branches off the cell body that carry
information to the cell body.
 Usually several to many.
 Relatively short.
 Often branched.
 Have receptors for neurotransmitters.
 Conduct local potentials.

Axon
That part of the neuron that carries
information to another neuron or muscle
cell.
 Usually relatively long.
 Single.
 Conducts action potential (nerve impulse)

Axon

Ends in short branched processes called:
Telodendria:
Give off endings called terminal boutons.
Terminal boutons contain synaptic vesicles of
neurotransmitters.

May have collateral branches.
Axon

Cell membrane is called the axolemma.

Cytoplasm is called the axoplasm.
Axon

Contains:
Mitochondria
Neurofilaments
Neurotubules
Axonal Transport
Anterograde
 Retrograde
 Slow transport
 Fast transport

Axon

Covered by neurolemma:
Made up of Schwann cells.

Often myelinated:
Myelin is formed by Schwann cells.

Note: axon is only part of neuron that is
ever myelinated.
General Terminology

Nucleus:
Aggregation of dendrites and nerve cell
bodies in the CNS.

Ganglion:
Aggregation of dendrites and nerve cell
bodies in the PNS.
General Terminology

Nerve:
Bundle of fibers (axons) in the PNS.

Tract:
Bundle of fibers (axons) in the CNS.

Commissure:
Tract in the CNS that crosses from one side
to the other.
General Terminology

White matter:
Areas of myelinated axons.

Gray matter:
Areas of unmyelinated axons, cell bodies,
and dendrites.
Functions of the CNS

Refer to p. 63 in syllabus
Spinal Nerve Branches
Dorsal primary ramus
 Ventral primary ramus
 Ramus recurrens
 White ramus communicans
 Gray ramus communicans

Spinal Nerve Branches
Paravertebral ganglion
 Splanchnic nerve
 Prevertebral ganglion

Reflex Arc

Afferent (sensory) pathways:
Somatic.
Visceral (splanchnic).

Efferent (motor) pathways:
Somatic.
Visceral (splanchnic).

Association neurons (interneurons).
Synapse

Components:
Presynaptic membrane:
With synaptic vesicles filled with
neurotransmitters.
Synaptic cleft:
Postsynaptic membrane:
With receptors for neurotransmitters.
Monosynaptic pathways.
 Polysynaptic pathways.
