pain, movement, mood

Question 1

both pain and touch sensory pathway

Answer 1

synapse in thalamus

sensations perceived in primary somatic sensory cortex

contralateral (stimulated on R –> shift to L side)

Question 2

thalamus

Answer 2

central switch station of brain
sorts out incoming physical signs (2* –> 3* thalamus)

Question 3

where does pain pathway cross to contralateral side

Answer 3

• pain: spinothalamic pathway (1* cross at dorsal horn in spinal cord)

Question 4

where does touch pathway cross to contralateral side

Answer 4

• touch: dorsal column pathway (1* crosses in medulla)

Question 5

touch vs pain

Answer 5

touch nerves send signals more quickly than pain nerves

(feel pierce before pain)

• thicker myelin sheath

Question 6

somatosensory relays of spinothalamic pathway

Answer 6

1) relay signal to tissue damage, pain sensation
2) signal generated at nociceptors in region of damage
3) nociceptors are free nerve ending. merge into afferent nerve fibre (Ad, C type)
4) fibre carry signal from periphery –> spinal cord
synapse at dorsal horm

5) spinothalamic neruon (2*, receiving neuron) sends long axon to thalamus.

6) thalamus (3* neuron) relay info to cortex (4* neuron)
variety of cortical regions receive pain info

Question 7

pathway that affects sensory processing
(how do we know the location)

Answer 7

signal travels along topographic lines

reach primary somatosensory cortex (L hemisphere = right body)

Question 8

signal travels along labeled line

Answer 8

receptor and its primary afferent (1* neuron) labeled because only respond to only 1 type of stimulus

chain of neurons relaying sensory info of particular modality

Question 9

modalities

Answer 9

modalities represent a class of stimuli (eg lead to somatosensation)

some are non-overlapping (vision and sound)

some are submodalities which overlaps (touch, pain)

Question 10

unimodal receptors

Answer 10

only 1 adequate stimulus

not have manifold adequate stimuli

Question 11

polymodal receptor

Answer 11

nociceptors: free nerve endings in the skin are called polymodal nociceptors because they contain multiple receptors and thus respond to various combinations of the above mentioned stimulus.

eg: mechano-heat C fibers

Question 12

large representation of face compared to trunk on cortical map

Answer 12

relay of info from face region more extensive than from trunk

high density of receptors in face region, more precise sensory experience.

Question 13

3 factors of sensation

Answer 13

1) location
2) intensity
3) quality

Question 14

location of sensation

Answer 14

location of receptor (receptive field)
duration of stimulus

Question 15

intensity of sensation

Answer 15

a) freq code (the more intense the stimulus, more AP per unit time (FREQ)

b) population code (number of receptors excited)

Question 16

quality of stimulus

Answer 16

nature of stimulus

vision (photo receptors)
mechanoreceptors
chemoreceptors
osmoreceptors
thermoreceptors
proprioceptors (position in space)
nociceptors (noxious stimuli)

Question 17

what is pain?

Answer 17

unpleasant feeling

felt acutely to warn indiv of the damage and prompt indiv to take remedial measures

• pain that outlast tissue damage/ after tissue recovered does not serve any USEFUL PURPOSE

Question 18

3 features of pain

Answer 18

1) intensity
2) unpleasantness (subjective)
3) duration (acute vs chronic)

Question 19

pain pathophysiology

Answer 19

allodynia: pain to normally non-pain stimulus

hyperalgesia: incr pain to noxious stimuli

Question 20

allodynia explained in 2parts

Answer 20

1) human sensory exp (lower threshold for excitation + POTENTIATES, higher intensity for given stimuli)

2) neural activity (incr AP response per unit time)
- central sensitization (spinal cord)
- peripheral (nociceptors neurons)

Question 21

spontaneous pain

Answer 21

spontaneous activity in pain pathway especially in nociceptors

Question 22

central sensitisation

Answer 22

sensitised spinal neurons strongly excited by touch.

• excited wide dynamic range neuron (grey column of spinal cord) along spinothalamic pathway –> sensation of pain
• potentiate freq of pain signal

Question 23

peripheral sensitisation

Answer 23

nociceptor terminals become more sensitive to the same quantity of the chemical mediators

potentiates pain intensity

Question 24

inhibitory neuron function

Answer 24

excitation of Ab fiber 1* (touch) will inhibit spinal-thalamic tract neuron 2* (pain)

rmb: pain crosses at dorsal column

Question 25

possible MOA of allodynia

Answer 25

1) degeneration of inhibitory neuron

2) inhibitory neuron is now activatory neuron. phenotypic alteration

3) spinal thalamic tract becomes sensitised, more easily excitable. tissue damaged, more neurotransmitters, incr freq so there is decr in threshold

Question 26

neurochemicals involved in sensitisation

Answer 26

CGRP
5HT
ATP
Sub P
glutamate

Question 27

drugs that inhibit neurochemicals that are involved in sensitisation

Answer 27

1) aspirin (NSAID, inhibit COX, block PG prod)

2) acetaminophen (reduce COX, antagonist TRPV receptor)

3) ubrogepant (CGRP RA)

Question 28

eg of allodynia

Answer 28

sprained ankle
neuropathy (nerve damage)
surgery (trauma and nerve damage)
sunburnt

• affects 1* nociceptive neurons and spinal neurons (interneuron)

Question 29

types of pain modulation

Answer 29

• decr pain: regulate signal along pain pathway, stress, morphine, context , PAG
• enhance pain: anxiety

Question 30

methods to modulate pain

Answer 30

1) descending - stimulates PAG, stimulate interneuron to inhibit transmission

2) segmental modulation

Question 31

PAG (periaquefuctal grey) and pain inhibition pathway

Answer 31

in midbrain
1) neurons in prefrontal cortex can activate PAG regions

2) medulla (in nuclues raphe magnus)

3) excites another neuron in spinal cord (interneuron = produce enkephalin)

4) inhibits transfer of signal to spinothalamic neuron (opioid receptors on axons of C, Ad fibers) : 5HT, enkephalin

• inhibit sub P

1st —-INHIBITED—-> 2nd order (spinothalamic neuron)

Question 32

morphine and enkephalin

Answer 32

morphine mimics enkephalin

binds to opioid receptors of axons (pain 1*)

Question 33

1. segmental modulation of pain
   (gate theory)

Answer 33

stimulate large diameter afferents (Ab, touch)
excite inhibitory interneuron

decr transmission of pain signal in spinal cord

• gate closed = local analgesic effect at spinal cord

Question 34

2. descending pathway

Answer 34

stimulate mid-brain PAQ

activate nucleus raphe magnus –> stimulate interneuron in spinal cord

release opioids (endorphin, 5HT, NA, enkephalin)

• inhibit the presynaptic form releasing sub P
• inhibit the post synapse of 2* neuron from transmitting signals.

Question 35

types of movements generated

Answer 35

1) reflexes - involuntary, withdrawal

2) rhythmic motor patterns (require vol initiation and termination) : walk, breathe, swim

3) voluntary - goal directed

Question 36

cortex – voluntary movement

Answer 36

premotor area and primary motor cortex

(left brain controls right muscle)

Question 37

brain stem (rhythmic motor patterns)

Answer 37

from mid brain –> medulla

brainstem and cortex influence execution of behaviour (via neurons that send long axons from site of origin –> spinal cord)

Question 38

spinal cord

Answer 38

reflexes, site of motor neurons to control muscle activity

Question 39

sensorimotor cortex contains

Answer 39

somatosensory cortex (parietal) vs somatomotor cortex (frontal lobe)

Question 40

neurons in basal ganglia

Answer 40

dopamine neurons
degeneration leads to Parkinson’s disease

interacts with cortex and affects initiation & selection of motor program

Question 41

damage to basal ganglia

Answer 41

1) disorder of movement - tremor, rapid flicking, dystonia, bradykinesia (slow) eg PARKINSON’S

2) disorder of posture - rigidity

Question 42

parkinson’s marked by 3 features

Answer 42

tremor
rigidity
bradykinesia

Question 43

descending control of efferent

Answer 43

corticospinal brainstem pathways for voluntary motor function

descending spinal tract system that originate from cortex/ brainstem

upper motor neurons travel in corticospinal tract
synapse in spinal cord (lower motor neurons)

contact with skeletal muscle (contraction)

Question 44

steps for voluntary movements

Answer 44

1) knowledge where body is in space (relative to obstructions)

2) where it intends to go

3) selection of a plan to get there (diff ways,selects fastest/ safest)

4) plan held in memory until the appropriate time

5) instruction to implement the plan

Question 45

1) knowledge where body is in space

Answer 45

mental body image generated by SOMATOSENSORY proprioceptive and visual inputs to

posterior parietal cortex (converge info – relative idea of where you are at)

Question 46

1) knowledge where body is in space

Answer 46

mental body image generated by SOMATOSENSORY proprioceptive and visual inputs to

posterior parietal cortex (converge info – relative idea of where you are at)

• proprioceptor stimulated

Question 47

2) where it intends to go and what to do

Answer 47

anterior frontal lobes

abstract thought, decision making, anticipate consequences for action

weight factors, risk vs benefits

Question 48

3) selection of a plan and held till execution

Answer 48

premotor cortical areas

cerebellum – coordinate movement
basal ganglia – decision, selection

Question 49

4) implementation

Answer 49

go command implemented by primary motor cortex

in participation of basal ganglia and cerebellum
“rhythmic motor movement”