Nervous system

Question 1

What do Afferent and Efferent mean?

Answer 1

Afferent - signal sent into CNS
Efferent - signal sent out of CNS

Question 2

Describe the PNS (2)

Answer 2

• Detects internal/external stimuli
• Controls conscious (somatic) movement and autonomic function

Question 3

Describe the CNS (3)

Answer 3

• Consists of brain and spinal cord
• Processes internal/ external information relayed
• Communicates with PNS to act on effectors

Question 4

Describe Neurons and how they communicate (2)

Answer 4

• Fundamental cell units of nervous system
• Use electrical/chemical signalling to communicate

Question 5

What are the 3 types of communication neurons perform?

Answer 5

1. Input
2. Computation
3. Output

Question 6

What are the 3 main classes of neuron?

Answer 6

1. Sensory neurons
2. Interneurons (process/relay)
3. Motor neuron (effectors)

Question 7

Describe how neurons communicate (3)

Answer 7

1. Neurons sends electrical impulse (action potential) along axon to terminals
2. Action potential release chemical neurotransmitter into synapse (acetylcholine)
3. Neurotransmitter can initiate action potential in subsequent neuron

Question 8

What are the 2 types of nerve fibres exiting the CNS to the PNS?

Answer 8

• Spinal nerves
• Cranial nerves

Question 9

Describe nerve fibres, and what they contain (3)

Answer 9

Axons bundled together (contains axons, connective tissue and blood vessels etc)

Question 10

Describe spinal nerves

Answer 10

nerve fibres exiting spinal cord

Question 11

how many pairs of spinal nerves exit the spinal cord to innervate regions of the body?

Answer 11

31

Question 12

Describe a dermatome and what it provides

Answer 12

• Regions of body innervated by given spinal nerve
• Provides motor control + sensation

Question 13

Name the 5 dermatomes (Can The Lorax Say Cheese)

Answer 13

1. Cervical
2. Thoracic
3. Lumbar
4. Sacral
5. Coccygeal

Question 14

How many cranial nerve pairs are there?

Answer 14

12

Question 15

Where do the cranial nerves send signals from?

Answer 15

brain/brainstem

Question 16

What are cranial nerves responsible for? (5)

Answer 16

1. Sensation + motor control in face, neck and eyes
2. Autonomic function(vagus nerve)
3. vision
4. Olfaction (smell)
5. Audition (hearing)

Question 17

Describe sensorimotor circuits (reflexes) (3)

Answer 17

1. Detection of stimuli (sensory afferent neurons)
2. Processing info (interneurons)
3. Output (motor efferent neurons)

Question 18

Describe the withdrawal reflex (doesn’t require brain)

Answer 18

1. Sensory neuron (afferents) detect painful stimuli
2. Signal projected to spinal cord via dorsal root (cell bodies in dorsal root ganglion, PNS)
3. Motor neuron efferents travel via ventral root to muscle effectors (motor neuron cell bodies in spinal cord grey matter (CNS)

Question 19

What is the spinal cord divided into? (2)

Answer 19

1. grey matter (cell bodies)
2. white matter (axons)

Question 20

Name the 2 main sensorimotor tracts in the spinal cord

Answer 20

1. Spinothalamic tracts
2. Pyramidal tracts

Question 21

What are the functions of the spinothalamic and pyramidal tracts?

Answer 21

Spinothalamic tracts - pain, temp and light touch (afferent)

Pyramidal tracts - motor neurons (muscle movement) (efferent)

Question 22

Describe the pathway of the spinothalamic tract (3)

Answer 22

1. sensory neurons cross to contralateral (opposite) side at spinal cord
2. Ascending sensory fibres pass up via medulla to thalamus
3. neurons pass from thalamus to somatosensory areas in brain to process sensory info

Question 23

Describe the pathway of the pyramidal tract (3)

Answer 23

1. Upper motor neurons from motor cortex to medulla
2. Motor neurons cross at medulla to contralateral side
3. Lower motor neurons exit spinal cord to control skeletal muscle

Question 24

What causes Brown-Sequard syndrome?

Answer 24

Hemi-section (half-cut) of spinal cord

Question 25

What are the symptoms of Brown-Sequard syndrome? (2)

Answer 25

1. Ipsilateral (same-side) loss of motor control 2. Contralateral loss of sensory function

Question 26

What are the effects of sympathetic nervous system activation? (4)

Answer 26

1. Increase heart/breathing rate 2. Inhibits digestion 3. Stimulates glucose release (glucocorticoid) 4. Redirects blood flow to heart, lungs and muscles (most blood vessels only controlled by SNS)

Question 27

Where does the sympathetic nervous system originate?

Answer 27

Thoracic-lumbar spine (chain ganglia - collection of cell bodies just outside spinal cord)

Question 28

What are the effects of the parasympathetic nervous system? (3)

Answer 28

1. Decrease heart/breathing rate 2. Stimulates digestion 3. Stimulates glucose storage

Question 29

Where does the parasympathetic nervous system originate? (2)

Answer 29

- Cranial nerves and sacral spine (ganglia net to target organs, no chain ganglia) - Vagus nerve (key ParasympatheticNS nerve)

Question 30

what is a ganglia?

Answer 30

Collection of cell bodies of the postganglionic neurons

Question 31

Define pre/postganglionic and describe the order (3)

Answer 31

Postganglionic - neurons after ganglia preganglionic - neurons before ganglia Order = preganglionic -> postganglionic -> target organ

Question 32

Name the neurotransmitters used by pre/postganglionic fibres of ANS (sympathetic/parasympathetic)

Answer 32

1. Sympathetic - pre = acetylcholine, post = noradrenaline 2. Parasympathetic - pre + post = acetylcholine

Question 33

Why is the ANS an important drug target?

Answer 33

Powerful regulatory effects on organ systems

Question 34

Name the effects of Beta blockers (3)

Answer 34

1. Block noradrenergic receptors 2. Reduce effects of SympatheticNS 3. Decrease blood pressure, can alleviate physiological anxiety symptoms

Question 35

Name the effects of lesions on autonomic and sensorimotor function (medullary syndrome - often caused by stroke of arteries supplying medulla) (3)

Answer 35

1. Vertigo 2. Impaired facial sensorimotor control 3. Autonomic dysfunction (eg. pupil constriction, eyelid drooping and lack of facial sweating)

Question 36

Name the effect of lesion dependant on location (Lateral/Medial) (2)

Answer 36

1. Lateral - pyramidal tract (motor) function spared 2. Medial - pyramidal tract (motor) function impaired