23 nervous system

Question 1

central nervous system components

Answer 1

brain
spinal cord
relay neurons

Question 2

peripheral nervous system components

Answer 2

cranial nerves
spinal nerves
peripheral nervs
sensory neurons
motor neurons

Question 3

grey matter

Answer 3

peripheral in brain called nuclei
central in spinal cord, butterfly shape
consists of : enrve cell bodies, dendrites, axons terminals, non-myelinated axons and neuroglia

The anterior and posterior prongs are referred to as ventral
horns (VH) and dorsal horns (DH), respectively. They are
connected by the grey commissure (GC)

Question 4

white matter

Answer 4

cnetarl in brain and peripheral in spina cord
consists of myelinated material

contains nerve fibres that form ascending
and descending tracts

Question 5

where the blood vessels

Answer 5

on outer connective layers at ventral fissure

Question 6

neurons

Answer 6

many dendrites, single axon
main body called soma
witnin the PNS

often myelinated

Question 7

Myelin in PNS and CNS

Answer 7

In the CNS, the myelin for the axon is produced by, and is
part of, an oligodendrocyte
• in the PNS, the myelin is produced by, and is part of, a
Schwann cell

Question 8

4 types of neurons

Answer 8

Motor
Location: CNS to periphery
Function: to send signals to effector tissues

Sensory
Location: Periphery towards CNS
Function: to send environmental signals to integrative
centre

Integrative
Location: CNS
Function: collate all information

Anaxonic
Location: retina (some parts of CNS)
Function: act as relays

Question 9

neuron structure

Answer 9

multipolar neuron: 1 axon multiple dendrites. most common.

bipolar: one axon one dendrite.
unipolar: sinle process leading away from the soma.

anaxonic neuron: many dendrites but no axon

Question 10

neurons

Answer 10

pseudounipolar (unipolar), bipolar, and
postsynaptic autonomic neuron cell bodies are
located outside the CNS
• Purkinje and pyramidal cells are restricted to the
CNS; many of them have elaborate dendritic
arborisations that facilitate their identification
• The majority of nerves in the CNS are interneurons

Question 11

movement in neuron

Answer 11

uses kinesin forward and dyenin backward. microtubule took off end and added on to front for movement down axon.

Anterograde and retrograde vesicles use microtubule
‘shuttle’ system to move from soma to synapse and back.

Question 12

5 different types of synapses

Answer 12

a. Axodendritic or axosomatic
- directly to the plasma membrane of nerve or cell
b. Axodendritic
- axon terminal synapses with a dendritic spine
c. Axoaxonic
- synapse at the axonic bouton
- The axoaxonic synapse may enhance or inhibit the
axodendritic (or axosomatic) synapse
d. Dendro-dendritic
e. Axo-axonal
- impinging dendritic/axonal synapse usually inhibits
other inputs

Question 13

peripheral nerves connective tissue layers

Answer 13

Paraneurium
Fascia that separates nerves from surrounding structures
Epineurium
Dense irregular connective tissue
Separates different types of nerves and fills spaces between
fascicles
Perineurium
Specialised connective tissue – transport proteins
Maintains ionic composition
Surrounds clusters of axons (fascicle)
Endoneurium
Loose connective tissue
Surrounds single nerve cells

Question 14

peripheral nerves 3 types

Answer 14

sensory, integrative and motor

Question 15

THE BIGGER THE DISTANCE BETWEEN NODES OF RANVIER

Answer 15

THE FASTER THE CONDUCTION

Question 16

myelination

Answer 16

1. The axon sitting in a groove is surrounded by a Schwann cell
2. The mesaxon membrane initiates myelination by
   surrounding the embedded axon
3. A sheet-like extension of the mesaxon membrane then wraps
   around the axon, forming multiple membrane layers
4. Cytoplasm is extruded from between the two apposing
   plasma membranes of the Schwann cell, which then become
   compacted to form myelin (19-20 rounds)

Question 17

inner and outer mesaxon

Answer 17

Outer mesaxon: invaginated plasma membrane extending
from the abaxonal surface of the Schwann cell to the myelin

Inner mesaxon: extends from the adaxonal surface of the
Schwann cell (the part facing the axon) to the myelin

Question 18

oligodendracyte in CNS

Answer 18

Cytoplasmic processes from the oligodendrocyte cell
body form flattened cytoplasmic sheaths that wrap
around each of the axons
• The relationship of cytoplasm and myelin is
essentially the same as that of Schwann cells
• Difference: wraps around more than one axon
simultaneously

Question 19

unmyelinated nereve cells

Answer 19

slwoer propagation of action potential

Question 20

astrocytes

Answer 20

control flow of nutrients in the CNS
star like
have perineural feet that contain gap junctions
regulate nerve ipulses by releasing glutamate near to node of ranvier

contributes to BBB

Question 21

microglial cell

Answer 21

large cell with elongated nucleus. mop up damaged nerve cells when they sense an increase in potassium. associated with alz

Question 22

ependymal cell

Answer 22

line the spinal canal

look similar to comulmnar epithelial cells

Question 23

ependymal cell functions

Answer 23

• Synthesise and secrete CSF in the ventricles (choroid plexus)
• Cilia move cerebrospinal fluid (CSF) through the ventricles to
the spinal cord
• Microvilli absorb CSF for removal of pathogens
- Present to microglial cells and astrocytes
- Modified tight junctions between epithelial cells control fluid
release into brain
- Molecular and cellular contents of brain can be monitored – ‘spinal
tap’

Question 24

MS

Answer 24

• Remitting and relapsing disease
• Caused by autoimmune degradation of myelin
- [Probably against EBV]

Question 25

MS symptoms

Answer 25

Fatigue
Vision problems (diplopia)
Slurred speech (dysarthria)
Numbness and tingling sensations (paraesthesia)
Mobility issues (muscle spasms)

–> symptoms caused by loss of conduction velocity