The Nervous system - Introduction to CNS and reflexes (lecture 1)

Question 1

What is the central nervous system comprised of ?

Answer 1

brain and spinal cord

Question 2

What two types of cells are found in the nervous system ?

Answer 2

neurons and neuroglia

Question 3

What are the four types of neuroglia cells in the CNS ?

Answer 3

Illustration of the four different types of glial cells found in the central nervous system: ependymal cells (light pink), astrocytes (green), microglial cells (red), and oligodendrocytes (light blue).

Question 4

What are the two types of neuroglia cells in the peripheral nervous system ?

Answer 4

schwann cells and satillite cells

Question 5

How many neurones are in the CNS ?

Answer 5

10 to the power of 12 - millions !!

Question 6

whats makes up the grey matter of a spinal cord cross section ?

Answer 6

dendrites, cell bodies, axon terminals

Question 7

What happens in the grey matter of the spinal cord ?

Answer 7

Synapses

Question 8

Whats the white matter composed of ? why white ?

Answer 8

axons - because myelin is white

Question 9

what are the two types of wings in the spinal cord ?

Answer 9

posterior (dorsal horns) and the anterior (ventral horns)

Question 10

What are propriospinal neurons?

Answer 10

i have no idea?

Question 11

What are ascending tracts ?

Answer 11

organised axons that pass information from the spinal cord to higher centres in the brain

Question 12

What are descending tracts ?

Answer 12

axons that relay commands from the brain and the spinal cord

Question 13

Where does the term nuclei refer to ?

Answer 13

within the brain, neurones which work together functionally are found in groups known as nuclei.

Question 14

How do bundles of axons in the brain run ?

Answer 14

longitudinally as well as transversely and thus divides the grey matter into discrete lumps

Question 15

What does the forebrain, cerebellum and the centrally located grey matter have in common ?

Answer 15

they have a peripheral layer of neurons known as the cortex

Question 16

What do afferent neurons do ?

Answer 16

sensory fibres relay information to the CNS

Question 17

What do efferent neurons do ?

Answer 17

motor fibres leave the CNS relaying commands to effectors such as muscle (skeletal, smooth or cardiac )

Question 18

What do sensory receptors do ?

Answer 18

monitor the external and internal environments for example the visual field or blood pressure

Question 19

What does the term reflex describe ?

Answer 19

Automatic, reproducible and goal directed responses of an organism to stimuli

Question 20

What are reflexes involved in ?

Answer 20

homestasis, postural stability others are protective in function

Question 21

Give me two examples of reflexes ?

Answer 21

cardiovascular reflexes, stretch reflex, the flexor withdrawal reflex

Question 22

Describe short-loop reflexes refer to ?

Answer 22

reflexes that only require spinal circuitry for example stretch and cutaneous reflexes

Question 23

Describe long-loop reflexes do ?

Answer 23

reflexes that involve higher centres (i.e. centres in the brain)

Question 24

How central modulation of reflex arcs occur ?

Answer 24

via descending pathways from higher centres

Question 25

What does a reflex arc involve ?

Answer 25

sensory receptors, afferent (sensory) neurons, central neurons and efferent (or motor neurons)

Question 26

What do motor neurons do ?

Answer 26

Excite effectors (skeletal muscle, smooth muscle, cardiac muscle or a gland)

Question 27

How is the stretch reflex unique ?

Answer 27

it is monosynaptic - i.e one synapse no central neurones involved. The afferents synapse directly onto motoneurons.

Question 28

What does the stretch reflex act to maintain ?

Answer 28

muscle length and is important in the control of posture

Question 29

What are the stretch receptors ?

Answer 29

muscle spindles which lie to parallel to the muscle fibres (known as extrafusal fibres)

Question 30

What are intrafusal fibres ?

Answer 30

muscle fibres contained within the muscle spindle s ?

Question 31

Tell me a characteristic of intrafusal fibres ?

Answer 31

they are thinner than extrafusal fibres

Question 32

What do muscle spindles contain ?

Answer 32

intrafusal muscle fibres and stretch receptors

Question 33

How many types of sensory endings do spindles have | ?

Answer 33

two, primary and secondary

Question 34

What are the primary endings associated with ?

Answer 34

large diameter afferent axons and are sensitive to both the length of the muscle and the rate of the change of length

Question 35

What are secondary endings sensitive to ?

Answer 35

only muscle length

Question 36

What do the primary afferents synapse directly with ?

Answer 36

motoneurons of the homonomous (same) muscle (and to a lesser extent onto motoneurons of synergistic muscles) and bring about reflex contraction . the same afferents also synapse with inhibitory interneurones which inhibit those motoneurons which innervate antagonistic muscles (reciprocal inhibition)

Question 37

what happens to antagonistic muscles ?

Answer 37

they are relaxed

Question 38

What can occur during a slow stretch ?

Answer 38

the firing of secondary endings may also contribute to the reflex excitation

Question 39

what occurs during a withdrawal reflex ? where do the afferent fibres arise from ?

Answer 39

from cutaneous nociceptors

Question 40

what do the small diameter afferent fibres synapse with during withdrawal reflex ?

Answer 40

The small diameter afferent fibres synapse with a number of interneurons( much divergence) within the dorsal horn of the spinal cord which then synapse with and excite motoneurons of flexor muscles.

Question 41

Is reciprocal inhibition seen during the withdrawal reflex ?

Answer 41

yes; the afferents synapse with a second group of interneurons which in turn synapse with and inhibit the firing of motoneurons of extensor muscles( i.e muscles which are antagonistic in action to flexor muscles).

Question 42

What does the excitation of flexor muscles produce ?

Answer 42

A reflex withdrawal of the stimulated limb away from the offending stimulus, so this reflex is protective in function

Question 43

What are the three protective structures of the CNS ?

Answer 43

Bone, Meninges and cerebrospinal fluid, glial cells, bone, connective tissue

Question 44

What are meninges ?

Answer 44

the three membranes that line the skull and vertebral canal and enclose the brain and spinal cord.

Question 45

What are the three meninges ?

Answer 45

(the dura mater, arachnoid, and pia mater)

Question 46

What is the cranium? function ?

Answer 46

the skull, protects the CNS, i.e protects the brain

Question 47

What is the vertebrae ?

Answer 47

each of the series of small bones forming the backbone, having several projections for articulation and muscle attachment, and a hole through which the spinal cord passes. the needle is inserted between two of the vertebrae.

Question 48

What is the cerebrospinal fluid ?

Answer 48

clear, colourless fluid found in the brain and spine. Protects the brain

Question 49

properties of a unipolar neuron have ? Are they motor neurons ?

Answer 49

one process, one dendrite that splits and one axon. | no they are sensory neurons

Question 50

properties of a bipolar neuron ? where are they found ?

Answer 50

two processes, one dendrite, and one axon. | In the retina of the eye

Question 51

properties of pseudo-unipolar cell ? where is it found ?

Answer 51

two processes, one dendrite, and one axon. | Ganglion cell of dorsal root

Question 52

What are the the three types of multipolar cells ?

Answer 52

normal motor neuron of spinal cord. Pyramidal cell of hippocampus purkinje cell of cerebellum

Question 53

Which matter are the cell bodies and dendrites grouped in ?

Answer 53

gray matter

Question 54

Which matter are the axons grouped in ?

Answer 54

white matter

Question 55

What do you call cell bodies in the CNS?

Answer 55

Nuclei

Question 56

What do you call cell bodies in the PNS ?

Answer 56

Ganglia

Question 57

What are axons in the CNS referred to as?

Answer 57

pathway projections, tracts , commissures

Question 58

Axons in the PNS?

Answer 58

Nerves: sensory. motor, mixed

Question 59

What cell produces myelin in in the CNS ?

Answer 59

oligodendrocytes

Question 60

give me three examples of involuntary/ automatic motor activity ?

Answer 60

reflexes not under direct control of the brain postural activity learnt, skilled activity

Question 61

Give me two examples of voluntary motor activity ?

Answer 61

Well learnt movements due to practice e.g drinking, driving, sports Goal directed activity with a degree of conscious attention to the take

Question 62

Properties of reflexes ?

Answer 62

Simplest motor act Fast , automatic, stereotyped (reproducible) involuntary - not under direct control of brain, but often modulated by activity in the CNS Short loop and long loop ( short/ long latency) response to specific stimulus

Question 63

Function of reflexes ?

Answer 63

involved in homeostasis involved in control of movement can be protective

Question 64

after a painful encounter of your toe with a needle what contracts and is inhibited ?

Answer 64

Flexors contract moving painful stimulus away. Extensors on same leg inhibited. on other leg: flexors inhibited. extensors contract as weight shifts to left leg

Question 65

What are the components of a reflex arc ?

Answer 65

Receptor: sensor (requires an adequate, specific stimulus) Afferent neurons: sensory Interneurons - spinal cord: depends on the type of reflex. monosynaptic = no interneurone efferent neurons: motor effector: muscle: skeletal, cardiac, smooth Gland

Question 66

Give me an example of a monosynaptic reflex ?

Answer 66

Stretch reflex

Question 67

Describe the stretch reflex ?

Answer 67

has both a monosynaptic (no interneurone) and disynaptic component ( 1 interneurone ). This is called reciprocal innervation.

Question 68

What is the function of the stretch reflex ?

Answer 68

The stretch reflex (myotatic reflex) is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length. When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases.