Neurones, Nerve Fibres and Peripheral Nerves

Question 1

What does the nervous system comprise of at the gross level?

Answer 1

NAME?

Question 2

What are the main functional components of the nervous system?

Answer 2

Brain and spinal cord

Question 3

How are the brain, spinal cord and nerves related?

Answer 3

They are all interconnected

Question 4

What 2 units can the brain, spinal and nerve be reconstituted into?

Answer 4

NAME?

Question 5

How many pairs of cranial nerves are there?

Answer 5

12 pairs

Question 6

How many pairs of segmental nerves are there?

Answer 6

31

Question 7

What is the nervous system made up of?

Answer 7

Trillions of nervous system cells

Question 8

What does analysis show of nerve cells?

Answer 8

They can be broadly divided into 2 types

Question 9

What are the 2 cell types of the nervous system?

Answer 9

NAME?

Question 10

How much of the nervous system cells are glia?

Answer 10

90%

Question 11

Which type of nervous system cells are responsible for sophisticated brain function?

Answer 11

Neurones

Question 12

What is the purpose of neuroglia?

Answer 12

Brings form to nervous system

Question 13

How can neuroglia be divided?

Answer 13

Into microglia and macroglia

Question 14

Where does microglia come from?

Answer 14

Bone marrow

Question 15

Where does macroglia come from?

Answer 15

Nervous tissue

Question 16

How can glia be stained in micrographs?

Answer 16

By the Golgi-Silver Impregnation technique

Question 17

What do the sub-types of macroglia vary depending on?

Answer 17

Which division of nervous system in question

Question 18

How do the microglia sub-types vary throughout the body?

Answer 18

They probably don’t

Question 19

What are the characteristic neuroglia in the CNS?

Answer 19

• Astrocytes
• Oligodendrocytes
• Ependyma
• Microglia

Question 20

Which neuroglia in the CNS have the largest cell count?

Answer 20

Astrocytes

Question 21

What do the astrocytes constitute?

Answer 21

The blood-brain barrier

Question 22

What is the purpose of astrocytes?

Answer 22

NAME?

Question 23

What is the purpose of oligodendrocytes?

Answer 23

Myelination

Question 24

How many cells can oligodendrocytes myelinate at a time?

Answer 24

Up to 250

Question 25

What happens if an oligodendrocyte become damaged?

Answer 25

Lots of subsequent cells affected

Question 26

What do ependyma do?

Answer 26

Line the ventricles and central canal of the spinal cord for circulation of cerebrospinal fluid

Question 27

What is the purpose of microglia?

Answer 27

Immunity and inflammation

Question 28

How do microglia assist in immunity and infection?

Answer 28

They remove infected material

Question 29

What happens if the microglia are faulty?

Answer 29

It can affect the BBB, which can lead to infections in the brain

Question 30

What are the characteristic neuroglia of the PNS?

Answer 30

- The Schwann cell - Sattelite cells  - Microglia

Question 31

What are the main functions of Schwann cells?

Answer 31

Insulation of the peripheral nerve axons

Question 32

What is the purpose of insulation of peripheral nerve axons?

Answer 32

Speed up impulse conduction

Question 33

How many Schwann cells myelinate 1 axon?

Answer 33

1

Question 34

What do Satellite cells do?

Answer 34

Physical support of neurones in the PNS

Question 35

What is a neurone?

Answer 35

The specialised functional unit of the nervous system

Question 36

What are the main features of the neurone?

Answer 36

#NAME?

Question 37

What do some neurones have?

Answer 37

Specialisations of cell bodies called dendrites

Question 38

What does the neurone require when staining?

Answer 38

Different staining for different parts

Question 39

What is the purpose of the cell body?

Answer 39

The ‘engine’ of the neuroen

Question 40

How do cell bodies vary?

Answer 40

In size and shape

Question 41

What does the neurone cell body contain?

Answer 41

- Nucelus  - Nissl substance - Golgi apparatus

Question 42

What is the purpose of the Nissl substance?

Answer 42

Protein synthesis

Question 43

What is the purpose of the Golgi apparatus in the cell body of a neurone?

Answer 43

Packaging of transmitters into vesicles

Question 44

How do collections of cell bodies appear in fresh/unstained tissue?

Answer 44

Relatively grey

Question 45

What do collections of cell bodies in the nervous system make up?

Answer 45

The grey matter

Question 46

What makes up the white matter of the nervous system?

Answer 46

Axons

Question 47

What is a typical example of grey matter in CNS?

Answer 47

Nerve nuclei

Question 48

What are collections of nerve cell bodies in the PNS known as?

Answer 48

Ganglia

Question 49

What else is the term ganglion used to describe?

Answer 49

Cysts and raised inguinal lymph nodes

Question 50

What happens in the initial segment?

Answer 50

Where the action potential is initiated

Question 51

What is different about the initial segment?

Answer 51

It has a high volume of voltage-gated sodium channels

Question 52

How do axons of neurones differ from each other?

Answer 52

#NAME?

Question 53

Which axons are not myelinated?

Answer 53

Thin ones

Question 54

What do non-myelianted axons have?

Answer 54

Intermingling sodium and potassium channels

Question 55

What axons are myelinated?

Answer 55

Thick axons

Question 56

What is conduction of electrical impulses corrected to?

Answer 56

The level of axonal myelination

Question 57

How many times does a Schwann cell wrap itself around an axon on average?

Answer 57

100 times

Question 58

Give 4 diseases that demyelinate axons

Answer 58

- Multiple Sclerosis  - Guillain Barre - Diabetes - Polyneuropathies

Question 59

Where does demyelination result in faster conduction?

Answer 59

Axons of x-sectional diameter less the 1µm

Question 60

What happens in an unmyelinated axon?

Answer 60

There is depolarisation along entire length of axon

Question 61

What happens in a myelinated axon?

Answer 61

There is depolarisation only at Nodes of Ranvier

Question 62

How much does the myelin sheath of a single Schwann cell?

Answer 62

Average of 100µm

Question 63

How are any two successive Schwann cells separated?

Answer 63

By an unmyelinated axonal segment known as node of Ranvier

Question 64

How big is a node of Ranvier?

Answer 64

~1µm in length

Question 65

What is the appearance of nerves?

Answer 65

Reflective, shiny, whiteish

Question 66

What causes the appearance of nerves?

Answer 66

Their myelin sheathing

Question 67

What is a peripheral nerve a typical example of?

Answer 67

White matter of the PNS

Question 68

What is a nerve covered in?

Answer 68

Epineurium

Question 69

What does the nerve contain?

Answer 69

Blood vessels

Question 70

How are groups of nerves arranged?

Answer 70

In groups called fascicles

Question 71

What covers fascicles?

Answer 71

Perineurium

Question 72

What is found in fascicles?

Answer 72

Axons

Question 73

What covers axons?

Answer 73

Endoneurium

Question 74

How do metastases travel?

Answer 74

In the plane of the epineurium

Question 75

What are the membranous envelopes of cranial and spinal nerves?

Answer 75

- Epineurium  - Perineurium  - Endoneurium

Question 76

What attaches epineurium to the adjacent nerve fascicle?

Answer 76

Interfascicular bonds

Question 77

What are the membranous envelopes of fibres tracts continuous with ?

Answer 77

Coverings of the brain and spinal cord, called meninges

Question 78

What are the membranous envelopes of the fibre tracts?

Answer 78

#NAME?

Question 79

What happens to the proximal segment of a severed neurone?

Answer 79

- The proximal segment soon seals up the damage to prevent leakage, forming a nerve stump  - Its cell body suddenly swells with increased contents  - The nucleus is displaced from its central position to peripheral margins - The axon usually regrows

Question 80

What is the displacement of the nucleus to peripheral margins known as?

Answer 80

Chromotolysis

Question 81

What is the regrowing of the axon being severed known as?

Answer 81

Wallerian regeneration

Question 82

What happens to the distal segment of a severed neurone?

Answer 82

It undergoes Wallerian degeneration

Question 83

Why does the distal segment of a severed neurone undergo Wallerian degeneration?

Answer 83

Because the segment is cut off from the nutritional support of the cell body, and so dies