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Flashcards in Nerves Deck (88):
0

What are the three gross level components of the nervous system?

-Brain
-Spinal cord
-Nerves

1

How many pairs of cranial nerves are there?

-12

2

How many pairs of segmental (spinal) nerves are there?

-31

3

What are the two cells of the nervous system?

-Glia cells (90%)
-Neurones (10%)

4

What are the two groups of neurones and in which direction do the carry impulses?

-Sensory/afferent fibres carrying impulses towards the CNS
-Motor/efferent fibres carrying impulses away from CNS

5

What is the function of the neuroglia?

-They are the 'glue' of the nervous system

6

What two divisions of neuroglia are they?

-Macroglia
-Microglia

7

What is the structure of neuroglia?

-Highly branched cells

8

What three groups can macroglia be divided into?

-Astrocytes
-Oligodendrocytes
-Schwann cells

9

What are the functions of the astrocytes?

-Support cellular matrix of the nervous system
-Give shape to the brain and spinal cord
-Act as phagocytes
-Breakdown glucose->lactate for neuronal nourishment
-Comprise the blood brain barrier

10

What is the function of the oligodendrocytes?

-Myelinate CNS axons (upto 250 axons/cell)

11

What is the function of schwann cells?

-Myelinate PNS axons (one axon/schwann cell)

12

When are microglia present in the nervous system?

-When there is inflammatory insult to the CNS

13

What are the functions of microglia?

-Act as immune surveillance cells of CNS
-Act as phagocytes

14

What are ependyma?

-Cilia-like projections which line the ventricles and central canal of the spinal cord for circulation of CSF

15

What is the function of the satellite cells?

-Provide physical support of PNS neurones

16

What is a dendrite?

-Projections from the cell body which receive stimuli from environment or other neurones and carry impulse to cell body

17

Where is the nucleus located in the cell body?

-Centre

18

What is nissl substance?

-aggregations of rER

19

What is the function of the rER and golgi in the cell body of a neurone?

-rER for protein synthesis
-Golgi for packaging of transmitters into vesicles

20

Are all axons myelinated?

-No

21

When would an unmyelinated neurone be better?

-When the axon has a diameter<1um the impulse will travel faster

22

Where is the initial segment of an axon located?

-Directly next to the cell body

23

What is the conduction of electrical impulse correlated to?

-The level of axonal myelination-> CV=6FD

24

What makes up grey matter in the CNS?

-Collections of cell bodies

25

What are ganglia?

-Collections of cell bodies in the PNS

26

Do schwann cells just wrap themselves around an axon once?

-No it can be up 100x around

27

Where is the electrical impulse generated from?

-The initial segment

28

What makes up white matter?

-Collections of ascending and descending axons as well as glial cells

29

How are neurones arranged in the spinal cord?

-The grey matter takes a butterfly shape inside white matter and has dorsal and ventral horns which contain large cell bodies

30

What two roots serve the grey matter?

-Dorsal nerve root
-Ventral nerve root

31

What is the ventral median fissure?

-The central point at which white matter converges

32

What neurones do the ventral cell bodies belong to?

-Spinal motor neurones which innervate muscle

33

What does the dorsal nerve root do?

-Carries sensory fibre impulses to the grey matter

34

Why is white matter white?

-Due to its high myelin content

35

How are the peripheral nerves anatomically arranged?

-Axons are arranged into fascicles which make up the peripheral nerve

36

What is epineurium?

-Connective tissue which ensheaths the entire nerve

37

What is perineurium?

-Connective tissue which ensheaths fascicles and between fascicles carrying interfascicular blood vessels

38

What is endoneurium?

-Connective tissue which surrounds a single axon and carries capillaries

39

How does a nerve react to an axon being severed?

-Proximal segment seals up to prevent leakage of contents
-A nerve stump is formed
-Distal segment is cut off from nutritional support
-Distal segment dies and undergoes wallarian degeneration with infiltration of microglia
-Cell body puffs up with increased contents
-Nucleus is displaced from the central position to the periphery (known as chromatolysis)

40

What is multiple sclerosis characterised by?

-Selective and patchy loss of myelin sheath
-Axonal destruction and overgrowth of glial tissue

41

Name some diseases of degenerative changes in peripheral nerves

-Peripheral neuropathy (non-inflammatory disease of peripheral nerves)
-Neuritis (Inflammatory disease)

42

What are the results of degenerative changes in peripheral nerves?

-Sensory loss
-Motor weakness
-Both

43

Can nerves be regenerated?

-They do not undergo mitosis but damaged peripheral nerves with axons still attached to the cell body can undergo regeneration

44

Define afferent neurone

-Neurone which carries signals from periphery to CNS, ie a sensory neurone

45

Define efferent neurone

-Neurone which carries impulse from CNS to periphery/effector, ie a motor neurone

46

Define ganglion

-Collection of neuronal cell bodies in the PNS

47

Define pre-ganglionic neurone

-Neurone immediately proximal to the ganglion

48

Define post-ganglionic neurone

-Neurone immediately distal to the ganglion

49

Define effector

-Target organ through which the nervous system exerts its action

50

State the divisions of the nervous system

-CNS and PNS both have Afferent and Efferent
-Efferent split into Somatic and Autonomic
-Autonomic split into sympathetic, parasympathetic and enteric

51

Which of the efferent divisions is voluntary/involuntary?

-Somatic-> voluntary
-Autonomic-> involuntary

52

What are the general actions of the autonomic nervous system?

-Constancy-> establishes and maintains homeostasis of the internal environment through regulating cardiovascular, digestive respiratory and thermoregulatory systems
-Control intermittent change in bias

53

What are the effector organs of the autonomic nervous system?

-Visceral organs
-Smooth muscle
-Secretory glands
-Cardiac muscle

54

How are the synapses divided between the sympathetic and parasympathetic nervous systems?

-Equally in a series arrangement

55

What is the general layout of the autonomic nervous system?

-Always 2 neurones arranges in series
-One with cell body in CNS and another with cell body in PNS

56

What are the pre-gangloinic neurones also called?

-White rami

57

What are the post ganglionic neurones also called?

-Grey rami

58

Which axon (pre or post ganglionic) is myelinated?

-Pre-ganglionic in the CNS

59

How many meninges are there?

-3

60

What is meant by organs receiving dual innervation?

-Receive innervation from both the parasympathetic and the sympathetic nervous systems

61

Which nervous system are most organs innervated by?

-Autonomic

62

How do the effects of the sympathetic and parasympathetic relate to each other?

-The effects are often reciprocal

63

What is autonomic tone?

-The balance of inputs and outputs between sympathetic and parasympathetic and the dominance that arises

64

Which glands receive only sympathetic innervation?

-Sweat glands

65

What is another name for the sympathetic nervous system?

-'fight or flight' system

66

When is the sympathetic nervous system dominant?

-During stressful situations

67

-What are the overall results of the sympathetic NS?

-Expenditure of energy
-Diversion of blood to heart and muscles
-Increase in heart rate, inotropic and chronotropic
-Increase in bp
-Reduced blood flow to gut and skin
-Increased sweating
-Dilation of retina

68

What is inotrpic?

-Increased strength

69

What is chronotropic?

-Increased rate

70

Where do nerve fibres of the sympathetic NS exit the CNS?

-Spinal cord only

71

Where are the cell bodies of the sympathetic NS located?

-All 12 thoracic segments of the spinal cord (T1-12)
-The first 2 lumbar segments

72

Where are the pre-ganglionic neurones of the sympathetic NS located?

-In the spinal cord

73

Pre-ganglionic sympathetic nerve fibres are under what kind of innervation?

-Cholinergic

74

What type of receptors do the post ganglionic neurones of the sympathetic nervous system express?

-Express nicotinic receptors

75

What kind of innervation are post ganglionic neurones of the sympathetic NS under?

-Mostly noradrenergic and some adrenergic

76

Describe the lengths of the pre/post ganglionic neurones of the sympathetic NS?

-Short pre-ganglionic neurones and long post-ganglionic neurones (for the majority)

77

What receptors do target organs of the sympathetic NS possess?

-a and b

78

What are the three possible levels of neurone termination in the sympathetic NS?

1) May synapse in chain at a level corresponding to the level of origin (paravertebral)
2)May synapse at a different level to origin up or down the chain
3)May not synapse in paravertebral chain but at effector organs (splanchnic nerves)

79

-What two exceptions of sympathetic post-ganglionic fibres are not noradrenergic?

-Perspiration
-Ejaculation

80

What are the general actions of the parasympathetic nervous system?

-Reduces heart rate and force of contraction
-Promotes digestion
-Promotes bodily functions such as bladder emptying
-Promotes sleep

81

Where do the nerve fibres of the parasympathetic NS leave the CNS

-Through 4 cranial nerves and the sacral segments S2-S4

82

Describe the lengths of the pre/post ganglionic neurones of the parasympathetic nervous system

-Long pre ganglionic neurones and short post ganglionic neurones

83

Under what type of innervation are pre-ganglionic neurones of the parasympathetic NS?

-Cholinergic

84

Where are most post-ganglionic neurones located?

-In the walls of the effector organ

85

What receptors do post-ganglionic neurones of the parasympathetic NS express?

-Nicotinic

86

Under what kind of innervation are the post-ganglionic neurones of the parasympathetic NS?

-Cholinergic

87

What effects do the sympathetic and parasympathetic have on the following structures, respectively:
-Eye
-Saliva
-Heartbeat
-Bronchi
-Peristalsis
-Liver
-Bladder
-Adrenal gland

-Dilates;Constricts
-Stop production;Increases production via medulla oblongata
-Inotropic + chronotropic increase; decreases via vagus nerve
-Dilates;Constricts via vagus nerve
-Inhibits via solar plexus;Stimulates via vagus nerve
-Stimulates glycogenolysis vua solar plexus;Stimulates glycogenesis and bile secretion
-Inhibits contraction;Contracts
-Stimulates adrenaline release via solar plexus