nervous tissue structure and function - why we need a nervous system Flashcards
what is grey matter and where is it located
grey matter contains dendrites, cell bodies, axon terminals, non myelinated axons and all support cells. located in centre of spinal chord and on edge of brain
what is white matter and where is it located
contains axons and myelinated material. is located on the outside of the spinal chord and in the centre of the brain. it is white because the myelinated material contains lots of lipids
what produces the myelin sheath
in CNS= produced by oligodendriytes and in PNS= by shcwann cells
structure of neurone
draw with dendrites, cell body, axon and end plate labelled. cell body and dendrites are located in the CNS
variations of neurone structure in the CNS
pyramiding and purkinje neurones both have very extensive dendrite network. their function is to collate information and they the sub type of neurone called integrative
types of neurone in the PNS (variations)
multipolar- 1 axon and multiple dendrites (cell body at the end)
unipolar- look at pic but cell body then dendrites and axon
bipolar- 1 axon and 1 dendrite with cell body in the middle
psuedounipolar - cell body coming off in the middle
what are nissil bodies
A Nissl body, also known as Nissl substance and Nissl material, is a large granular body found in neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis
how is information passed so quickly along neurone
atugrade and retrograde use microtubules to shuttle from the soma (cell body) to the synapse
how is neurotransmitter synthesised
vesicles are transported using microtubules. each vesicle contains just 1 enzyme and as it travels the length of the axon it starts to synthesis its neurotransmitter. vesicles without neurotransmitter will be transported back to the cell body or lost to the neurolemma
structure of a nerve
epineurium- covers outside holding the fascicles together
perineurium - on the outside of a fascicle (paraneurium)
endoneurium covers the outside of a nerve fibre
within each fascicle there are the same type of nerve e.g myelinated or non myelinated
how to recognise nerves with myelin on a microscope slide
toluidine blue stains fat and if there is a large blue ring around the nerve = myelin
difference between myelinated and unmyelinated structure
in unmyelinated multiple nerve fibres are surrounded by a Schwann cell. here the impulse will travel along the outer edge. whereas in myelinated each nerve fibre is surrounded by a myelin sheath, here the impulse will travel down the centre. look at pics
how does myelination occur
axon is sitting in grove surrounded by Schwann cell. the mesaxon membrane surrounds axon and wraps itself around it forming multiple layer. the cytoplasm is extorted from between the layers and it becomes compact to form myelin
what is an oligodendrocyte
does the same thing as a Schwann cell but in the CNS however it wraps more the 1 axon simultaneously
what is an astrocyte
star like structure. Have perineural diet which contain gap junctions. regulate nerve impulses by releasing glutamate and contribute to blood brain barrier
what is a microglial cell
large cell with elongated nucleus acting as a resident macrophage removing damaged nerve cells and acting as an immune cell
what is an ependymal cell
they line the spinal chord and ventricles of brain producing cerebral fluid which is moved with their villi. microvilli absorb the cerebral fluid for the removal of pathogens. look at pic of them
what is multiple sclerosis
autoimmune degradation of myelin = loss of conduction velocity and therefore symptoms such as fatigue, vision problems, slurred speech, numbness/tingling and mobility issues
name the support cells of the CNS
oligodendrocytes, astrocytes, microglial cell and ependymal cell
what is myelin and what does it do
many layers of plasma membrane without the cytoplasm. acts as an insulating material preventing action potentials from being generated. speed up rate of conduction by saltatory conduction
what are satellite/glial cells and where are they found
Found in the PNS they cover the cell bodies in the ganglia
glial cells?
cell present in the CNS
nerves that carry impulses towards CNS and away from CNS
towards= sensory or afferent away = motor or efferent
what is a ganglion
an accumulation of neurone cell bodies outside the CNS
why do we need a nervous system
can’t rely on diffusion alone for communication
how can the motor output of nervous system be divided
somatic (voluntary) and autonomic (involuntary). And then autonomic is divided into sympathetic (fight or flight, affects whole body) or parasympathetic (rest and digest, selectively targets cells/organs)
where are the parasympathetic spinal chord segments found and the sympathetic spinal chord segments found
para- top and bottom
sympa- in the middle
draw myosynaptic reflex arc
draw?
difference between structure of para and sympathetic
both have 2 chains of neurones and a synapse between them at the autonomic ganglion. sympathetic has short axon and long dendron whereas para has a long axon and a ganglia found in the wall of target organ with therefore a short axon
how spinal chord communicates with autonomic NS
draw it
how does the sympathetic nervous system supply the skin - 1 spinal chord doesn’t add up to 1 dermatome?
from the entry level segment it will ascend and descend the chain and the impulse will be sent out from the spinal chord
how are the viscera supplied by the sympathetic nervous system because this dermatome lines up to the parasympathetic spinal chord segment
go straight through chain and the no the aorta where there are specialised ganglion called splachic nerves. This is the example with the heart as a part of the viscera. can also be for other organs in viscera
targets of the parasympathetic nervous system
supplies visera via vagus nerve and the head also has 4 specialised ganglia found in the target organs - cilary to eye, pterygopalatine to facial nerves and lacrimal gland in eye, submandibular to salivary gland and otic to parotid gland
