Cells & Tissues of The Nervous System

Question 1

What are the 2 different cell types that make up the nervous system?

Answer 1

Neurones and glial cells

Question 2

What is a neurone?

Answer 2

Structural and functional unit, excitable cells and impulses carries as action potentials - typical neurone has multiple dendrites, a cell body, an axon which ends in synaptic terminals - high metabolic rate - long living and amitotic (lives entire life without being replaced so if lost is lost forever)

Question 3

What are glial cells?

Answer 3

Non-excitable supporting cells and are much smaller than neurones

Question 4

What are the different types of neurone?

Answer 4

Multipolar, pseudounipolar and bipolar

Question 5

Describe a multipolar neurone.

Answer 5

Typical neurones seen in diagrams- all motor neurones carrying impulses from the CNS to periphery and interneurones =multipolar - their cell bodies are situated within the CNS

Question 6

Describe a pseudounipolar neurone.

Answer 6

The action potential can go straight through bypassing the cell body so from dendrite to axon - these are sensory neurones and their cell bodies form ganglia of spinal and cranial nerves

Question 7

Describe a bipolar neurone.

Answer 7

Found in cranial nerve 1 (olfactory) and 2 (optic)= 1 dendrite, 1 cell body and 1 axon

Question 8

What is the myelin sheath?

Answer 8

Speeds up conduction in axons called ‘saltatory conduction’ by action potentials jumping from node to node - it is formed by Schwann cells in the PNS and olgidendrocytes in the CNS

Question 9

What is the importance of the myelin sheath?

Answer 9

without it conduction would be too slow and patchy loss/scarring of the myelin sheath causes abnormal conduction which will appear as white plaques on an MRI

Question 10

What is the difference between white and grey matter in the spinal cord?

Answer 10

White matter surrounds the central H-shaped grey matter
White= myelinated axons
Grey= neuronal cell bodies

Question 11

How is the white matter arranged?

Answer 11

Tracts= specific bundles of axon carrying specific information to a specific part of the brain or periphery- can be descending (from brain/brain stem to periphery) or ascending (sensory information from the periphery)

Question 12

Describe the dorsal and ventral roots of the spinal cord.

Answer 12

Dorsal (posterior) root is sensory and the ventral (anterior) root is motor - motor= multipolar so cell body is in the ventral root of the spinal cord and the axon leaves through the ventral root into either the ventral or dorsal ramus

Question 13

Describe the distribution of grey and white matter in the brain.

Answer 13

Grey matter is around the edge and surrounds the white matter but there are also collections of grey matter found in the cerebral hemispheres called nuclei

Question 14

What are the types of glial cell?

Answer 14

CNS= astrocytes, microglia, ependymal cells, oligodendrocytes
PNS= Schwann cells, satellite cells

Question 15

What are astrocytes?

Answer 15

Most common glial cell, have a central nucleus and multiple feet-like processes called end-feet which surround synapses and capillaries and help in K+ buffering and maintaining the BBB

Question 16

What’s are microglia?

Answer 16

the WBCs of the brain (as normal WBCs cannot cross the BBB)- phagocytosis and scar tissue formation

Question 17

What are ependymal cells?

Answer 17

Have a single process which projects upwards, they line the ventricles and central canal of the spinal cord

Question 18

What are oligodendrocytes and Schwann cells?

Answer 18

Oligodendrocytes= myelination in the CNS

Schwann cells= myelination in the PNS

Question 19

What are satellite cells?

Answer 19

Found in the neuronal cell bodies in ganglia and probably help in protecting the neuronal cell bodies in the ganglia

Question 20

What is the blood brain barrier?

Answer 20

a barrier created between blood flowing through the capillaries and the brain tissue surrounding these capillaries = protective mechanism that helps maintain a stable environment for the brain and prevents harmful amino acids and ions present in the bloodstream and blood cells from entering the brain

Question 21

What can cross the BBB?

Answer 21

Only lipid molecules or substances can move freely across the capillaries and water soluble molecules like glucose and AA need to pass through pumps

Question 22

Where is the BBB absent?

Answer 22

in a few ‘circumventricular’ organs= parts of the hypothalamus and posterior pituitary are they are endocrine organs so this would impair their function

Question 23

What do drugs to manage conditions in the brain need to be?

Answer 23

lipid soluble or use suitable vectors in order to get past the BBB

Question 24

Describe the folds of dura matter which separate the brain.

Answer 24

falx cerebri= separates the 2 cerebral hemispheres
falx cerebelli= separates the 2 cerebellar hemispheres
tentorium cerebelli= separates the cerebral hemispheres from the cerebellum

Question 25

What are ventricles and describe their locations.

Answer 25

cavities within the brain containing CSF and are all connected:
lateral ventricles= c-shaped cavities which lie in the cerebral hemispheres
interventricular foremen= connects the lateral to the 3rd ventricles which is in the diencephalon
cerebral aqueduct= lies in the midbrain
4th ventricle= diamond-shaped and lies in the hindbrain

Question 26

What is CSF?

Answer 26

fluid inside the brain in the ventricles and central canal of the spinal cord and between the pia and arachnoid layers of the meninges - it is important for helping the brain float to prevent the cranial cavity from crushing itself with its own weight

Question 27

Describe the circulation of the CSF.

Answer 27

formed in the choroid plexus inside each ventricle (mostly lateral) then goes to the 3rd and 4th and a little to the central canal but most enters the subarachnoid space - it is absorbed by arachnoid villi into the sagittal sinus

Question 28

What are the meninges?

Answer 28

3 coverings of the CNS:
dura matter= tough, fibrous and has dural folds
arachnoid matte= middle layer
pia matter= vascularises and dips into folds of the brain
subdural space= potential space which is transverse by blood vessels penetrating into the CNS
subarachnoid space= contains CSF