Download MBBS Nervous Tissue Lecture PPT

Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Nervous Tissue Lecture PPT


INTRODUCTION

? Nervous tissue--> Consists of two types of cells:

neurons (nerve cells) and neuroglial cell.

? Nervous tissue has property of irritability and

conductivity.

? Nerve cells are capable of receiving information from

external and internal environment.

? About 10 million neurons in human beings.
? Size of neuron 10 um to 120 um
? Neurons do not divide after birth, so their number

does not increases during lifetime.
COMPOSITION OF NERVOUS TISSUE

1)Neuron (nerve cell)--Structural and functional units

of nervous system.

2)Nerve cell processes--Many radiating processes

called dendrite and a single process called axon.

3)Neuroglia--Supporting function for neurons and

their processes.
? NEURON--
? Functional cell of nervous tissue.

? Consists of
Nerve Cell body -- Expanded portion.

Nerve cell processes-- Dendrite and axon,

emerges from cell body.
? Nerve cell body--
? Contains:--
? Nucleus--large, spherical and centrally located.

? Nissl bodies--large aggregations of rough

endoplasmic reticulum.

? Melanin pigments--dark brown granules in

substantia nigra.


Neurons (Nerve Cells)

6

Figure 11.4b
? Nerve cell processes--

? Elongated cytoplasmic processes originate from

the cell body

? Two types ? Axon (single)
- Dendrite (multiple)
? Nerve fibre term used for nerve cell process

(axon or dendrites).
? Dendrites--
? Multiple, short, branched and tapering processes

of nerve cell.

? Receive information from other cells (input

portion of neuron).

? Cytoplasm contains--Nissl bodies, microtubules,

microfilament and other organells.
? Axon--
? Single, long, cylindrical process of nerve cell.
? Send information away from nerve cell body to

another cell.

? Axon hillock-- Conical origin of axon from cell body
? Axon terminals are known as end bulbs (terminal

boutons).

? Axolemma--Plasma membrane of axon
? Axoplasm-- Cytoplasm of axon.
? Nissl bodies is absent in axon.


Neurons (Nerve Cells)

10

Figure 11.4b
DIFFERENCE BETWEEN AXON & DENDRITE

AXON

DENDRITE

SINGLE, LONG THIN PROCESS OF MULTIPLE, SHORT, THICK &

NERVE CELL

TAPERING PROCESSES OF NERVE

CELL

TERMINATES AWAY FROM NERVE TERMINATES NEAR THE NERVE

CELL BODY

CELL BODY

UNIFORM DIAMETER & SMOOTH NOT UNIFORM

FREE OF NISSL GRANULES

CONTAIN NISSL GRANULES

NERVE IMPULSE TRAVELS AWAY IMPULSE TRAVELS TOWARDS

FROM CELL BODY

CELL BODY
CLASSIFICATION OF NEURONS

? BASED ON SHAPE OF CELL BODY & NUMBER OF CELL PROCESSES

? UNIPOLAR NEURONS--
? Only one process (usually dendrite) extending from

cell body.

? Mesencephalic nucleus of trigeminal nerve.

? PSEUDOUNIPOLAR NEURON--
? Has one process that divide into axon and dendrite.
? Dorsal root ganglion and cranial nerve ganglion.
? BIPOLAR NEURONS--
? Has two processes(an axon and dendrite).
? Present in Retina.

? MULTIPOLAR NEURONS--
? Has many processes (an axon and many dendrite).
? These are most common type of neurons
? Depending upon shape of cell bodies they are called

stellate (star shaped), purkinje (flask shaped) or

pyramidal (triangular).

? Present in spinal cord, cerebrum & cerebellum.

? CLASSIFICATION BASED ON FUNCTION

? SENSORY (AFFERENT)--
? Receives stimuli from receptor and conduct impulse

to CNS.

? MOTOR (EFFERENT)--
? Conduct impulse from CNS to effector organs.

? INTERNEURON--
? Located only in CNS .
? Small size, interconnect other neuron.
Synapses

? A junction that mediates information transfer

from one neuron:

? To another neuron
? To an effector cell

? Presynaptic neuron ? conducts impulses

toward the synapse

? Postsynaptic neuron ? transmits impulses

away from the synapse

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Structure of synapse

Action

potential

Neurotransmitter

Na+

Ca2+

Axon terminal of

1

presynaptic neuron

Receptor

Postsynaptic

Mitochondrion

membrane

Axon of

Postsynaptic

presynaptic

membrane

neuron

Ion channel open

Synaptic vesicles

5

containing
neurotransmitter
molecules

Degraded

2

neurotransmitter

Synaptic
cleft

3

4

Ion channel closed

Ion channel

Ion channel (open)

(closed)

17

Figure 11.18
Types of Synapses

? Axodendritic ? between the axon of one

neuron and the dendrite of another.

Most common type.

? Axosomatic ? between the axon of one

neuron and the soma of another.

? Axoaxonic- between one axon to other axon .

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NEUROGLIA

? Neuroglia

? Provide structural and metabolic support for neurons.
? Segregate and insulate neurons.

? Neuroglial cells in CNS

a)Astocytes

b)Ependymal cell

c)Oligodendrocytes

d)Microglia

? Neuroglial cells in PNS

a)Schwann cells

b)Satellite cells
SIZE

LARGE

LARGE

MEDIUM

SMALL

NUCLEUS

OVAL

OVAL

SPHERICAL

ELONGATED

OCCURRENCE GREY MATTER

WHITE MATTER

WHITE MATTER

GREY AND

WHITE MATTER

FUNCTION

SUPPORTING,

MYELINATION

PHAGOCYTOSIS

REPAIR AND

BARRIER

ORIGINE

NEURONAL

NEURONAL

MESODERMAL

ECTODERM

ECTODERM
MYELIN SHEATH

? Myelin is an insulating sheath surrounding axons

of central and peripheral nervous system.

? CNS-- Oligodendrocytes cells
? PNS-- Schwann cells
? Between adjacent segment of myelin along each

axon, a gap occurs where axon is not covered by

myelin.

? These gaps are called are called nodes of Ranvier.
? Myelin sheath increases the velocity of

conduction of impulse.

? It provides insulating sheath surrounding fibres.

This post was last modified on 30 November 2021