Anatomy: Nerves Flashcards Preview

Principles > Anatomy: Nerves > Flashcards

Flashcards in Anatomy: Nerves Deck (90)
Loading flashcards...
1

What is a group of nerve cell bodies in the CNS called?

A nucleus

2

What is a group of nerve cell bodies in the PNS called?

A ganglion

3

What is an axon?

A nerve fibre conveying action potentials

4

What are bundles of axons travelling together in a) the CNS and b) the PNS called?

a) A tract
b) A peripheral nerve

5

What is a myelin sheath?

A cover round the nerve which is an electrical insulator. A myelinated nerve conducts faster

6

What happens at a synapse?

one neurone communicates with another neurone in a ganglion in the PNS or in a nucleus in the CNS.
electrical signal (AP) becomes a chemical signal (neurotransmitter) then an electrical signal again

7

What are the folds in the brain called?

Gyri (single gryus)

8

What are the spaces in between the gyri called?

Sulci (plural sulcus)

9

What is the cerebral neocortex/cortex?

the outermost layer of the cerebral hemispheres, consisting of all the gyri and sulci

10

How many lobes does each cerbral hemisphere consist of?

4

11

How are the 4 lobes of each cerebral hemisphere named?

approximately according to the bone of the cranial vault they lie deep to:
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe

12

What fissure separates the two lobes of the brain sagitally?

The longutidinal fissure

13

Name the 12 cranial nerves

1. CN I the olfactory nerve
2. CN II the optic nerve
3. CN III the oculomotor nerve
4. CN IV the trochlear nerve
5. CN V the trigeminal nerve
6. CN VI the abducent nerve
7. CN VII the facial nerve
8. CN VIII the vestibulocochlear nerve
9. CN IX the glossopharyngeal nerve
10. CN X the vagus nerve
11. CN XI the spinal accessory nerve
12. CN XII the hypoglossal nerve

14

What are the indents in the floor of the cranium called?

The anterior, middle and posterior cranial fossae

15

Name the foraminae for the cranial nerves

Cribriform plate of the ethmoid bone
Optic canal
Superior orbital fissure
Foramen rotundum
Foramen ovale
Internal acoustic meatus
Jugular foramen
Hypoglossal canal
Foramen magnum

16

What type of matter is in the cerebral cortex of the brain?

Grey matter- contains cell bodies

17

What type of matter is deep to the grey matter?
What gives it this appearance?

White matter
It contains many axons which are myelinated
Myelin gives the whiter appearance

18

What is different about the structure in the spinal cord in terms of the matter?

The white matter is superficial and the grey matter is deep

19

How does the spinal cord connect with the brain?

It passes through the foramen magnum of the occipital bone

20

Where does the spinal cord lie?

In The vertebral canal

21

What are the 4 segments of the spinal cord?

cervical
thoracic
lumbar
sacral/coccygeal

22

What are the two enlargements (wider parts) of the spinal cord?

cervical enlargement due to all the upper limb nerves
lumbosacral enlargement due to all the lower limb nerves

23

How many pairs of spinal nerves does the spinal cord connect bilaterally with?

31

24

Where does the spinal cord end as a solid structure?

At the conus medullaris
At the level of L1/L2 intervertebral disc

25

What is the cauda equina?

lumbar and sacral spinal nerve ROOTS have to descend in the vertebral canal to their respective intervertebral foraminae

26

How many pairs of cervical spinal nerves are there?

8

27

How many pairs of thoracic spinal nerves are there?

12

28

How many pairs of lumbar spinal nerves are there?

5

29

How many pairs of sacral spinal nerves are there?

5

30

How many pairs of coccygeal spinal nerves are there?

1

31

What is the spinal nerve?

the part that is located within the intervertebral foramen BELOW* the vertebra of the same number (*except cervical region)

32

What connects the spinal cord to the spinal nerves?

The roots and rootlets

33

What connects the spinal nerve to the structures of the soma?

The rami

34

What is a dermatome of a spinal nerve?

the dermatome of the spinal nerve is the area of skin (strip) supplied by both the anterior and the posterior rami

35

What do the posterior rami supply?

the posterior paramedian strip of the dermatome

36

What do the anterior rami supply?

the larger anterior rami supply the remainder of the posterior part, the lateral and the anterior parts of the dermatome and ALL of the limb dermatomes (there are no posterior rami in limb dermatomes)

37

What supplies the limbs?

ONLY anterior rami supply the limbs via plexi

38

What are nerve plexi?

networks of intertwined anterior rami axons

39

What is the right cervical plexus and what does it supply?

C1-C4 anterior rami
supplies mainly neck wall

40

What is the right brachial plexus and what does it supply?

C5-T1 anterior rami
supplies upper limb

41

What is the right lumbar plexus and what does it supply?

L1-L4 anterior rami
supplies lower limb

42

What is the right sacral plexus and what does it supply?

L5-S4 anterior rami
supplies pelvis/perineum & lower limb

43

What is the left musculocutaneous nerve?

a named nerve branch from the brachial plexus
made from axons from both C5 & C6 anterior rami

44

What are named nerves?

containing axons from more than 1 spinal cord segment/spinal nerve result from a plexus

45

What are the 5 named nerves that result from the brachial plexus?
What do they supply?

axillary nerve
median nerve
musculocutaneous nerve
radial nerve
ulnar nerve
They supply the upper limb

46

Which segments of the spinal cord have lateral horns?
What are they for?

T1 to L2 segments
for cell bodies of the next sympathetic neurones in the chain

47

Where do sympathetic axons from the brain descend?

In the spinal cord in white matter

48

Describe the sympathetic supply to the soma

Sympathetic axons travel from autonomic centres in brain
There are connections with T1 to L2 spinal nerves via rami communicans
sympathetic trunks run the full length of vertebral column
sympathetic nerve fibres enter ALL spinal nerves and then ALL anterior and posterior rami

49

Which cranial nerves contain parasympathetic axons?
What are they for?

cranial nerves III, VII, IX & X
for organs of the head/neck/chest and abdomen as far as the midgut

50

Apart from some cranial nerves, which other nerves contain parasympathetic axons?
What are they for?

the sacral spinal nerves contain parasympathetic axons for organs of the hindgut/pelvis/perineum

51

Where do nerves containing parasympathetic axons travel to?

to ONLY the internal organs - not the body wall

52

How many parasympathetic ganglia are in the head?

4

53

How is the nervous system subdivided on the basis of function?

The SOMATIC NERVOUS SYSTEM
the body wall senses and responds to the external environment

The AUTONOMIC NERVOUS SYSTEM (ANS)
(also called the visceral motor system)
body organs sense and respond to the internal environment

54

What are the body wall organs?
What supplies them?

sweat glands in the skin
arrector smooth muscles for hairy skin
arterioles are everywhere
- all supplied by the autonomic NS

55

What is a) the sensory supply and b) the motor supply of the body wall?

a) Somatic sensory
b) somatic motor

56

What is a) the sensory supply and b) the motor supply of the body organs?

a) visceral afferent
b) Sympathetic and parasympathetic

57

What is a) the sensory supply and b) the motor supply of the special sense organs?

a) Special sensory
b) sympathetic and parasympathetic

58

What is in a peripheral nerve?

nerve fibres (axons), wrapped up in connective tissue, travelling together to/from the same region of the body or structure

59

Are all of the axons in a peripheral nerve the same type?

They may be, in which case the peripheral nerve would be classified as e.g.
a somatic motor nerve
a somatic sensory nerve
a special sensory nerve
a sympathetic nerve
a parasympathetic nerve

there is normally a mixture of neuronal types:
a “mixed nerve”
spinal nerves & their branches are usually mixed nerves containing:
somatic sensory, somatic motor & sympathetic axons

60

How many of the cranial nerves are mixed nerves?

5

61

Are there sympathetic axons in any cranial nerves?

No

62

What sensations can our body wall perceive?

coarse touch
fine touch
vibration
position sense (proprioception)
temperature – hot & cold thermoreceptors
pain – nociceptors

63

Where does a sensory axon from the left thumb (e.g. in the C6 anterior ramus) join with the spinal cord?

It passes into the posterior root ganglion of the left c6 spinal nerve, then into the posterior root, then into the posterior rootlet, then enters the posterior root horn.

64

What happens to the sensory action potential in the posterior root horn of spinal nerve 6?

It synapses in the posterior horn spinal cord nucleus onto the second sensory neurone in the chain.
The second sensory neurones axon then crosses the midline onto a spinal cord tract ascending towards the right thalamus then the right side of the cerebral cortex.
sensory AP arrives at the location in the right cerebral cortex specific to the part of the left body wall stimulated

65

How many neurones are in the somatic sensory pathway for temperature?

3

66

Where is the right primary somatosensory area?
Where are the sensory action potentials that arrive here from?

In the right parietal lobe.
sensory APs arriving here bring left sided body wall sensations into “consciousness"

67

Where is the right primary somatomotor area?

In the right frontal lobe

68

What do motor APs originating here cause to happen?

contractions of left sided skeletal muscles to make a consciously planned movement.

69

How many neurones are in a somatic motor pathway?
Where do the axons cross over to the other side?

2
In the brainstem

70

What are the first neurones in a somatic motor pathway called?

The upper motor neurones

71

How do somatic sensory action potentials travel from the head wall to the brain?

In a cranial nerve

72

How do somatic motor action potentials travel to skeletal muscle in the head/neck?

In a cranial nerve

73

What are the second neurones in a somatic motor pathway called?

Lower motor neurones

74

In a somatic Motor Pathway to the skeletal muscles of the left upper limb, which horn in the brainstem to the upper motor neurone axons descend to?

Left anterior horn

75

Which spinal nerves are involved in supplying the left upper limb?

C5-T1

76

What is a reflex?

a reflex is an extremely rapid (missing out the pathway to the brain) involuntary response to a (potentially harmful) stimulus

77

What is a paralysed muscle?

a muscle without a functioning lower motorneurone

78

What can a paralysed muscle not do?

a paralysed muscle cannot contract
caused by an injury to the muscle’s motor nerve

79

How would a paralysed muscle appear on examination?

on examination the muscle would have reduced tone (reduced resistance to stretch – “floppy”)

80

What is spasticity?

the muscle has an intact and functioning lower motorneurone
the descending controls from the brain are not working
- the muscle is essentially being allowed to “over-contract” continuously
caused by an injury to the descending controls

81

How would a spastic muscle appear on examination?

the muscle would have increased tone (increased resistance to stretch – “tight”)

82

What does the ANS do?

senses and responds to the internal environment

83

What are sensory axons of the organs called?

Visceral afferents

84

Which organs do the sympathetic and parasympathetic axons supply?

All of them

85

What is the effect of sympathetic stimulation on the pupils?

They dilate

86

What is the effect of sympathetic stimulation on the GI tract?

motility is reduced/sphincters close

87

What is the effect of sympathetic stimulation on arterioles?

In skeletal muscle: dilate
In skin: constrict

88

What structures in the body wall are supplied by sympathetic axons?

skin sweat glands
skin arrector muscles
ALL arterioles (sympathetic tone)

89

Do parasympathetic axons supply the body wall organs?

No

90

Do parasympathetic axons supply arterioles?

No