Brain Cells

8/2/2019 Brain Cells

1/37


2/37

The Cells of the Nervous

SystemThe human nervous system is comprisedof two kinds of cells:

Neurons

Glia

The human brain contains approximately

100 billion individual neurons.

Behavior depends upon the

communication between neurons.


3/37


4/37


SystemLike other cells in the body, neurons

contain the following structures:

Membrane

Nucleus

Mitochondria

Ribosomes

Endoplasmic reticulum


5/37

The Cells of the Nervous System

Neuron cells are similar to other cells ofthe body but have a distinctive shape.

A motor neuron has its soma in the

spinal cord and receives excitation fromother neurons and conducts impulses

along it axon to a muscle.

A sensory neuron is specialized at oneend to be highly sensitive to a particular

type of stimulation (touch, temperature,

odor etc.)


6/37

Fig. 2-5, p. 32


7/37

Fig. 2-6, p. 33


8/37


SystemAll neurons have the following majorcomponents:

Dendrites.Soma/ cell body.

Axon.

Presynaptic terminals.


9/37


SystemDendrites- branching fibers with a surface

lined with synaptic receptors responsible

for bringing in information from other

neurons.

sSome dendrites also contain dendritic

spines that further branch out and

increase the surface area of the dendrite.


10/37

Fig. 2-7, p. 33


11/37


SystemSoma - contains the nucleus, mitochondria,

ribosomes, and other structures found in

other cells.

Also responsible for the metabolic work of the

neuron.


12/37


SystemAxon - thin fiber of a neuron responsible

for transmiting nerve impulses away to

other neurons, glands, or muscles.

Some neurons are covered with an

insulating material called the myelin

sheath with interruptions in the sheathknown as nodes of Ranvier.


13/37


SystemPresynaptic terminals refer to the end points

of an axon responsible for releasing

chemicals to communicate with other

neurons.


14/37


SystemTerms used to describe the neuron include

the following:

Afferent axon - refers to bringing informationinto a structure.

Efferent axon - refers to carrying information

away from a structure.

Interneurons orIntrinsic neurons are thosewhose dendrites and axons are completely

contained within a structure.


15/37

Fig. 2-8, p. 34


16/37


17/37


18/37

Glial cells

Support cells of the CENTRAL NERVOUS

SYSTEM

Special types of connective tissue cells thathelp support and protect neurons.

other major component of the nervous

system


19/37

Types of Glial cells

Non nervous or glial cells

1). Astrocytes

2). Microglia3). Ependymal

4). Oliodendrocytes

5). Satellite cells6). Schwann cells form myelin sheaths


20/37

Schwann cells

Support cells in

peripheral nerves

Myelinating Schwanncells wrap around

axons of motor and

sensory neurons to

sheathmyelinform the


21/37


22/37


23/37

Function of Schwann cells

alongnervous impulsesthe conduction of,axons

,regenerationnerve development and

,neuronstrophic support for

production of the nerve extracellular matrix,modulation of neuromuscular synaptic

activity,-Ttoantigensand presentation of

..lymphocytes


24/37

Fig. 2-10, p. 35


25/37

Astrocytes

most abundant type of macroglial cell

also called astroglia

extend branching cytoplasmicprocesses in all directions (yielding thestar-like shape suggested by theirname; astro = star).

helps synchronize the activity of theaxon by wrapping around thepresynaptic terminal and taking upchemicals released by the axon.


26/37

Fig. 2-11, p. 36


27/37

Functions of Astrocytes

endothelial cellsbiochemical support of

,brain barrier-bloodwhich form the

provision of nutrients to the nervous

tissue,

maintenance of extracellular ion balance,

and a principal role in the repair and

scarring process of the brain and spinalcord following traumatic injuries.


28/37

Microglia

are small cells, comprisingabout 10% of the total brain

cell populaton,

believed to represent the

brain's immune system (i.e.,macrophage-equivalents

residing within the brain).

remove waste material

and othermicroorganisms that

could prove harmful to

the neuron.


29/37

Functions of microglia

Scavenging

Phagocytosis

CytotoxicityAntigen presentation

Synaptic stripping

Promotion of repair

Extracellular signaling


30/37

Ependymal cells

Ependyma is the thinliningepithelial membrane

ofventricular systemthe

spinaland thebrainthe .cord

It is involved in thecerebrospinalproduction of

(CSF).fluid

Ependyma is made up ofependymal cells


31/37

Ependymal cells

-that line the CSFcellsepithelialin the brain andventriclesfilled

of the spinalcentral canalthecord.

are coveredapical surfacesTheir, which circulateciliaa)In a layer of

CSF around the central nervoussystem

, which absorbmicrovillib) withCSF

CSF producing cells


32/37


33/37

Oliodendrocytes

oligo = few

form no basementmembrane

more susceptible to ischemicdamage than areastrocytes, but less sothan neurons.

oligodendrocyte wrap

themselves aroundportions of the surroundingaxons.


34/37

Function of Oliodendrocytes

myelin producing cells of CNS

form myelin in the CNS and hence are

responsible for normal propagation ofaction potentials

can myelinate more than one axon.

unlike Schwann cells of the PNS, formsegments of myelin sheaths of numerous

neurons at once


35/37


36/37


37/37

Satellite cells

that line the exteriorglial cell A type of

peripheralin theneuronssurface of

(PNS)nervous system

Satellite glial cells (SGCs) also surround

.neuron cell body within gangliaThey are thought to have a similar role

central nervousin theastrocytesto

(CNS)system

Date post:	06-Apr-2018
Category:	Documents
Upload:	neela-chand
View:	216 times
Download:	0 times

Brain Cells

Documents