CNS

Question 1

Explain Stretch reflex:

Answer 1

• hammer stroke causes stretch in quadriceps muscle
• stretch detected by muscle spindle(stretch receptor)
• stretch reflex causes muscle contraction to maintain muscle length
• monosynaptic arc through dorsal root, and out ventral root. –> contracts muscle
• polysynaptic arc through dorsal root, 2 out of ventral root, contracts muscle and relaxes opposing muscle.

Question 2

Explain withdrawal reflex:

Answer 2

• pain is detected by a sensory neuron
• motor response to move away from the painful stimulus.

Two simultaneous responses
- Ipsilateral: flexors active & extensors relax–> limb withdraws
- Controlateral: extensors active & flexors relax–> opposing limb extends, takes weight.

Question 3

movements activated by central generation patterns;

Answer 3

locomotion, breathing, chewing, swallowing.

Question 4

What brain centres are involved in movements?

Answer 4

premotor cortex - plans movement
cerebellum - balance
basal ganglia - initiating movement.

Question 5

Corticospinal pathway

Answer 5

output from motor cortex to the spinal neurons that carries signals to control movements
(mostly controlateral - spinal cord cross)

Question 6

Brainstem pathway

Answer 6

output form brainstem to the spinal neurons. co-ordinated activity in large muscle groups for posture and balance,
(mostly ipsolateral)

Question 7

coding of sensory information

Answer 7

modality, intensity, duration, location

Question 8

Dorsal column pathway

Answer 8

fine touch, proprioception
synapses in dorsal column nucleus, and in thalamus.
contralateral (brainstem cross)
3rd axon terminates at sensory cortex.

Question 9

anterolateral pathway

Answer 9

pain, temperature
synapses in spinal cord and thalamus.
contralateral (spinal cord cross)
3rd axon terminates at sensory cortex

Question 10

Pain nerve fibres

Answer 10

c-fibres: chemosensitive nociceptors
- smallest diameter, slow, large receptive fields
- signal ongoing damage

a-gamma fibres: thermal & mechanical stimuli.
- small diameter, fast, small receptive fields
-signal acute onset of pain stimulus

a-B fibres
- largest diameter, fast,
- mechanoreceptor fibres(no pain)

Question 11

Pain types

Answer 11

local
referred
neurogenic
muscle

Question 12

Sleep-wake cycle

Answer 12

suprachiasmatic nucleus generates sleep waking cycle of about 24 hrs. - intrinsic pacemaker

stages;
beta - awake
alpha - restful
theta - drowsiness
delta - deep sleep
REM sleep - occurs during light sleep, skeletal muscles are most relaxed, HR + respiration are highest.

Question 13

taxi drivers have;

Answer 13

enlarged grey matter in the right hippocampus.

Question 14

Language areas

Answer 14

b b bb Broca
- constructs language,
- pathology causes lack of fluency

words words Wernickes
- language comprehension
pathology causes lack of meaning

Question 15

Memory stages:

Answer 15

Short-term(working) memory; continued activity in brain circuits,
- when interrupted, memory is lost
- involves prefrontal cortex

Long term memory;
more permanent changes in brain function and structure. involves changes of strength –in specific synapses(long-term potentiation, LTP)
-stored in hippocampus.

Question 16

Memory types;

Answer 16

Declarative; things that can be declared
- Episodic(recollection snapshots of life events & experiences
- Semantic(knowledge, words and their meanings)
- stored in hippocampus and temporal lobe

Procedural memory: how to do things,
- patients with dementia tend to retain this longer than declarative.
- stored in cerebellum