nervous tissue

Question 1

what is a nerve cell?

Answer 1

collection of neurons - responsible for generating and transmitting electrical signals
.type of nerve cell- neuroglia ( glial cells ) - cells that play essential supporting roles in nerve cell function

Question 2

what are the 3 main components of a neuron?

Answer 2

. dendrites
. cell body ( nucleus )
. axon

Question 3

what is the function of dendrites ?

Answer 3

. receives incoming electrical signals from nerve cell or environment .
. branches on dendrites ( arborizations ) vary from one dendrite to other they can be simple or elaborate- increase surface area

Question 4

what is the function of cell body ( soma ) ?

Answer 4

. main site of metabolic support for a neuron
. most protein synthesis occurs in the cell body
-Sums electrical signals coming from dendrites

Question 5

what is the function of axon ?

Answer 5

. this is where electrical signals leave the cell body

. axons end in terminal arborizations where neuron contacts other nerve cell or muscle cell

Question 6

what is the point of contact where axon terminals contacts other nerve cell or muscle cell ?

Answer 6

. synapse

Question 7

what are the four basic morphological types of nerve cells?

Answer 7

1. anaxonic - no axon e.g retinal amacrine cell
2. unipolar - one neurite emanating from the cell body
   e. g. sensory neurons
3. bipolar - one dendritic process and one axon leave cell body
   e. g. retina
4. multipolar - multiple neurite emanating from the cell body

Question 8

what is the size of soma ?

Answer 8

10-25um

Question 9

what are the stringy bits you can see in the soma ?

Answer 9

axon + dendrites ( neurite )

Question 10

what are CNS grey and white matter ?

Answer 10

grey - numerous cell bodies and few myelinated axon

white - few cell bodies and more myelinated axon - more myelin causing white appearance

Question 11

what are the PNS and CNS glial cells ?

Answer 11

CNS - oligodendrocytes , astrocytes and ependymal cell, microglia
PNS - schwann cell , satellite cell and macrophage

Question 12

function of schwann cell ?

Answer 12

. produce myelin in the PNS.
. can provide one neuron with myelin
. neuron can receive myelin from many schwann cell
. wrap itself around axon

Question 13

function of oligodendrocytes ?

Answer 13

. produce myelin in the CNS
. can provide several neurons with myelin
. wrap itself around a neuron

Question 14

function of astrocytes ?

Answer 14

. important for blood:brain barrier
.have a role in damage repair
. store nutrients(glucose)
.astrocytes replicate - main source of CNS tumours
.isolate synapes

Question 15

function of ependymal cells ?

Answer 15

line the ventricles of brain and central canal of spinal cord
involved in secretion of CSF

Question 16

function of microglia ?

Answer 16

.normally 'dormant' 
. involved in CNS injury/inflammation
.move to damage site
.phagocytose pathogens
.release cytokines to attract other immune cells

Question 17

what are nerve cells ?

Answer 17

. they are collection of neurons.

. nerve cells can be sensory , motor or both

Question 18

what do sensory and motor neurons innervate within the eye ?

Answer 18

motor neurons - innervate muscles and glands

sensory neurons - optic nerve which takes messages from the retina to brain

Question 19

describe the structure of nerves?

Answer 19

. divided into bundles of neurons ( fasicles ) by connective tissue
.connective tissue between individual neurons (endoneurium)
. perineurium surrounds each bundle of neurons
. epineurium encloses the whole cell

Question 20

what are the functional consequences of the variation of diameter in axon ?

Answer 20

Larger diameter axons have a higher conduction velocity, which means they are able to send electrical signals faster.

Question 21

What is the diameter of axons?

What is the length of axon?

Answer 21

1um
up to 20um
in giant squid axons- 1mm
Length- 1mm-1m

Question 22

What is neuroglia?

Answer 22

supporting cells of the nervous system

Question 23

What are the functions of various classes of glial cell?

Answer 23

• is to provide different forms of mechanicals, biochemical and physiological support for different parts of the neuron.
• glial cells do not generate electrical impulses.

Question 24

How does myleination provided by 2 cell types differ?

Answer 24

A single oligodendrocyte provides myelin to several neurons
A single schwann cell provides myelin to one single neuron- however one single neuron can recieve its myelin from several different schwann cells.

Question 25

Which glial cells line the cerebral ventricles and why?

Answer 25

Ependyml cells- secrete the cerebrospinal fluid

Question 26

What are the dark areas between the fasciles?

Answer 26

blood vessels

Question 27

What are the vast majoirity of CNS neruons?

Answer 27

Multipolar

Question 28

What is the best example of bipolar neruon?

Answer 28

retina

Question 29

Where does unipolarity occur?

Answer 29

only exist in some sensory neurons of the PNS

-not in the eye

Question 30

What is the ventral horn of the spinal cord stained with?

Answer 30

holmes silver stain (Red.brown)
triple stain (blue)
-shows the grey matter- mostly filled with cell bodies
-the stains help identify the cells bodies of multipolar neurones.

Question 31

What does the cell body appear as in the spinal cord?

Answer 31

in the grey matter- which in the spinal cord is the darker area in the middle- that appears like the letter H

Question 32

What is the orbital nerve- which shows cross sections of cranial nerves stained with?

Answer 32

toludine blue.
These are a part of the CNS and innervate specific ocular structures.
In this section axons have a circular profile.