The nervous system presentation dawn part 1

THE NERVOUS SYSTEM

DAWN V TOMY M.Pharm

Asst.Professor

Dept. Of Pharmacology

St.JOSEPH’S COLLEGE OF PHARMACY,CHERTHALA.

Part -1

2

Divisions of the Nervous System

• Central Nervous System (CNS)

• Brain.

• Spinal cord.

• Peripheral Nervous System (PNS) consists of the cranial nerves

and spinal nerves. The 3 divisions of PNS are:

1. Somatic Nervous System (SNS)

2. Autonomic Nervous System (ANS) and

3. Enteric Nervous System.

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Divisions of Peripheral Nervous System

• Sensory Division

• Picks up sensory information and delivers it to the CNS

• Motor Division

• Carries information to muscles and glands

• Divisions of the Motor Neurons:

• Somatic Neurons – carries information to skeletal

muscle.

•Autonomic Neurons – carries information to smooth

muscle, cardiac muscle, and glands.

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Divisions Nervous SystemCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Sensory division Sensory receptors

Motor division

Skeletal muscle

Brain

(a) (b)

Spinal

cord Spinal

nerves

Cranial

nerves

Central Nervous System

(brain and spinal cord)

Peripheral Nervous System

(cranial and spinal nerves)

Smooth muscle

Cardiac muscle

Glands

Autonomic

Nervous

System

Somatic

Nervous

System

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Histology of Nerve cells

• Cell types in neural tissue:

• Neurons

• Neuroglial cells (also

known as neuroglia, glia,

and glial cells)

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Dendrites

Cell body

Axon

Nuclei of

neuroglia

© Ed Reschke

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The Neurons

• Neurons may vary in size and shape.

• They may differ in length and size of their axons and dendrites.

• Neurons share certain features:

• Dendrites

•A cell body

•An axon

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Neuron Structure

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Cell body

Nucleus

Dendrites

Impulse

Nodes of Ranvier

Myelin (cut)

Axon

Axon

Chromatophilic

substance

(Nissl bodies)

Axonal

hillock

Axon collateral

Schwann

cell

Synaptic knob of

axon terminal

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Classification of Neurons and Neuroglia

• Neurons vary in function

• They can be sensory, motor, or integrative neurons

• Neurons vary in size and shape, and in the number of axons

and dendrites that they may have

• Due to structural differences, neurons can be classified into

three (3) major groups:

• Bipolar neurons

• Unipolar neurons

• Multipolar neurons

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Classification of Neurons: Structural Differences

• Bipolar neurons

• Two processes

• Eyes, ears, nose

• Unipolar neurons

• One process

• Ganglia of PNS

• Sensory

• Multipolar neurons

• 99% of neurons

• Many processes

• Most neurons of

CNS

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Dendrites

Axon Axon

AxonDirection

of impulse

(a) Multipolar

Central

process

Peripheral

process

(c) Unipolar(b) Bipolar

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Classification of Neurons: Functional Differences

• Sensory Neurons

•Afferent

• Carry impulse to CNS

• Most are unipolar

• Some are bipolar

• Interneurons

• Link neurons

•Aka association neurons

or internuncial neurons

• Multipolar

• Located in CNS

• Motor Neurons

• Multipolar

• Carry impulses away from CNS

• Carry impulses to effectors

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Central nervous system Peripheral nervous system

Cell body

Interneurons

Dendrites

Axon

Axon

Sensory (afferent) neuron

Motor (efferent) neuron

Cell body

Axon

(central process)

Axon

(peripheral process)

Sensory

receptor

Effector

(muscle or gland)

Axon

terminal

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Types of Neuroglial Cellsin the CNS

2) Astrocytes

• CNS

• Scar tissue

• Mop up excess ions.

• Induce synapse formation

• Connect neurons to blood vessels

•Part of Blood Brain Barrier

3) Oligodendrocytes

• CNS

• Myelinating cell

4) Ependyma or ependymal

• CNS

• Ciliated

• Line central canal of spinal

cord

• Line ventricles of brain

1) Microglia

• CNS

• Phagocytic cell

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Types of Neuroglial Cells

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Microglial cell

Axon

Oligodendrocyte

Astrocyte

Capillary

Neuron

Myelin

sheath (cut)

Node of

Ranvier

Ependymal

cell

Fluid-filled cavity

of the brain or

spinal cord

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Types of Neuroglial Cellsin the PNS

1) Schwann Cells

• Produce myelin found on peripheral myelinated neurons

• Speed up neurotransmission

2) Satellite Cells

• Support clusters of neuron cell bodies (ganglia)

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Regeneration of A Nerve Axon

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AxonSite of injury Schwann cells

(a)

(b)

(c)

(d)

(e)

Changes

over time

Motor neuron

cell body

Former connection

reestablished

Schwann cells

proliferate

Schwann cells

degenerate

Proximal end of injured axon

regenerates into tube of sheath cells

Distal portion of

axon degenerates

Skeletal

muscle fiber

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General Functions of the Nervous System

• The three general functions of the nervous system:

• Receiving stimuli = sensory function

• Deciding about stimuli = integrative function

• Reacting to stimuli = motor function

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Functions of Nervous System

• Sensory Function

• Sensory receptors gather information

• Information is carried to the CNS

• Integrative Function

• Sensory information used to create:• Sensations

• Memory

• Thoughts

• Decisions

• Motor Function

• Decisions are acted upon

• Impulses are carried to effectors

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Myelination of Axons

• White Matter

• Contains myelinated

axons

• Considered fiber tracts

• Gray Matter

• Contains unmyelinated

structures

• Cell bodies, dendrites

Dendrite

Node of Ranvier

Myelinated region of axon

Axon

(a)

Unmyelinated

region of axon

Neuron

cell body

Neuron

nucleus

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(c)

Enveloping

Schwann cellSchwann

cell nucleus

Unmyelinated

axon

Longitudinal

groove