nervous tissue Flashcards
what is a nerve cell?
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
what are the 3 main components of a neuron?
. dendrites
. cell body ( nucleus )
. axon
what is the function of dendrites ?
. 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
what is the function of cell body ( soma ) ?
. main site of metabolic support for a neuron
. most protein synthesis occurs in the cell body
-Sums electrical signals coming from dendrites
what is the function of axon ?
. this is where electrical signals leave the cell body
. axons end in terminal arborizations where neuron contacts other nerve cell or muscle cell
what is the point of contact where axon terminals contacts other nerve cell or muscle cell ?
. synapse
what are the four basic morphological types of nerve cells?
- anaxonic - no axon e.g retinal amacrine cell
- unipolar - one neurite emanating from the cell body
e. g. sensory neurons - bipolar - one dendritic process and one axon leave cell body
e. g. retina - multipolar - multiple neurite emanating from the cell body
what is the size of soma ?
10-25um
what are the stringy bits you can see in the soma ?
axon + dendrites ( neurite )
what are CNS grey and white matter ?
grey - numerous cell bodies and few myelinated axon
white - few cell bodies and more myelinated axon - more myelin causing white appearance
what are the PNS and CNS glial cells ?
CNS - oligodendrocytes , astrocytes and ependymal cell, microglia
PNS - schwann cell , satellite cell and macrophage
function of schwann cell ?
. produce myelin in the PNS.
. can provide one neuron with myelin
. neuron can receive myelin from many schwann cell
. wrap itself around axon
function of oligodendrocytes ?
. produce myelin in the CNS
. can provide several neurons with myelin
. wrap itself around a neuron
function of astrocytes ?
. important for blood:brain barrier .have a role in damage repair . store nutrients(glucose) .astrocytes replicate - main source of CNS tumours .isolate synapes
function of ependymal cells ?
line the ventricles of brain and central canal of spinal cord
involved in secretion of CSF
function of microglia ?
.normally 'dormant' . involved in CNS injury/inflammation .move to damage site .phagocytose pathogens .release cytokines to attract other immune cells
what are nerve cells ?
. they are collection of neurons.
. nerve cells can be sensory , motor or both
what do sensory and motor neurons innervate within the eye ?
motor neurons - innervate muscles and glands
sensory neurons - optic nerve which takes messages from the retina to brain
describe the structure of nerves?
. 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
what are the functional consequences of the variation of diameter in axon ?
Larger diameter axons have a higher conduction velocity, which means they are able to send electrical signals faster.
What is the diameter of axons?
What is the length of axon?
1um
up to 20um
in giant squid axons- 1mm
Length- 1mm-1m
What is neuroglia?
supporting cells of the nervous system
What are the functions of various classes of glial cell?
- is to provide different forms of mechanicals, biochemical and physiological support for different parts of the neuron.
- glial cells do not generate electrical impulses.
How does myleination provided by 2 cell types differ?
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.
Which glial cells line the cerebral ventricles and why?
Ependyml cells- secrete the cerebrospinal fluid
What are the dark areas between the fasciles?
blood vessels
What are the vast majoirity of CNS neruons?
Multipolar
What is the best example of bipolar neruon?
retina
Where does unipolarity occur?
only exist in some sensory neurons of the PNS
-not in the eye
What is the ventral horn of the spinal cord stained with?
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.
What does the cell body appear as in the spinal cord?
in the grey matter- which in the spinal cord is the darker area in the middle- that appears like the letter H
What is the orbital nerve- which shows cross sections of cranial nerves stained with?
toludine blue.
These are a part of the CNS and innervate specific ocular structures.
In this section axons have a circular profile.
