Central Processing of Sensory Signals

Question 1

descending inhibition

Answer 1

activity from higher areas in the brain can “screen out” certain sensory information

Question 2

2 types of descending inhibition

Answer 2

1. presynaptic inhibition

2. postsynaptic inhibition

Question 3

what does presynaptic inhibition inhibit

Answer 3

specific sensations

Question 4

what does postsynaptic inhibition inhibit

Answer 4

all synaptic inputs

Question 5

how long does presynaptic inhibition last? postsynaptic?

Answer 5

presynaptic = several milliseconds
postsynaptic = less than 1 millisecond

Question 6

presynaptic inhibition

Answer 6

reduces transmitter release at synapse between 1st and 2nd order sensory neurons

Question 7

postsynaptic inhibition

Answer 7

hyperpolarises membrane of 2nd order sensory neurons

Question 8

convergence

Answer 8

multiple afferent neurons synapse with each interneuron

Question 9

divergence

Answer 9

each afferent neuron synapses with multiple interneurons

Question 10

how are pain receptors activated

Answer 10

damaged tissue releases prostaglandins and histamine

Question 11

what does pain fiber activity cause

Answer 11

release of substance P in spinal cord

Question 12

what is caused by the release of substance P

Answer 12

signals in projection neurons ascend to brain pain centers

Question 13

aspirin function

Answer 13

inhibits prostaglandin synthesis and release from damaged tissues

Question 14

opioid function

Answer 14

opioid receptors block substance P release

Question 15

analgesia

Answer 15

suppression of pain

Question 16

endogenous opiates

Answer 16

opiates created by the brain during the fight or flight response

Question 17

endogenous opiate production pathway

Answer 17

1. periaqueductal grey matter
2. reticular formation
3. opiates produced

Question 18

what else can inhibit projection neurons

Answer 18

the firing of large sensory afferents

Question 19

example of large sensory afferents

Answer 19

1. rapid movement
2. acupuncture
3. transcutaneous electrical stimulation
   4, rubbing the skin

Question 20

gabapentin function

Answer 20

blocks conduction in C-fibre axons (inhibits pain)

Question 21

referred pain

Answer 21

feeling somatic pain due to visceral pain

Question 22

what causes referred pain

Answer 22

convergence of visceral and somatic afferents on ascending projection neurons in the spinal cord

Question 23

how do pain and temperature afferents form tracts in the spinal cord

Answer 23

synapse 2nd order interneurons that cross within 2 segments and ascend in spinothalamic tracts

Question 24

spinothalamic tracts

Answer 24

anterolateral tracts

Question 25

how do mechanoreceptive afferents form tracts in the spinal cord

Answer 25

afferents ascend in dorsal columns and THEN synapse 2nd order interneurons and cross in the brainstem

Question 26

where do all ascending pathways synapse (except smell)

Answer 26

in the thalamus

Question 27

how are motor commands transmitted from higher brain areas

Answer 27

through the brainstem to the spinal cord

Question 28

how do sensory afferents contribute to motor control

Answer 28

1. mediate spinal reflexes

2. ascend to brainstem, cerebellum, and cerebral cortex to provide feedback

Question 29

what other area does motor feedback come from

Answer 29

visual and balance centers

Question 30

desired state

Answer 30

a motor command issued to neuronal networks in the spinal cord

Question 31

what creates a desired state

Answer 31

brain, cerebellum, brainstem

Question 32

what type of motoneurons send signals to muscles

Answer 32

alpha motoneurons

Question 33

actual state

Answer 33

sensory receptors communicate this back to the CNS to compare to the desired state

Question 34

error signal

Answer 34

signal outputted to the muscles to reduce difference between actual state and desired state

Question 35

where are Ia and II sensory axons located

Answer 35

in parallel with muscle fibers

Question 36

what do Ia and II sensory axons respond to

Answer 36

changes in muscle length

Question 37

where are Ib sensory endings located

Answer 37

in tendons

Question 38

what to Ib sensory endings respond to

Answer 38

muscle force

Question 39

what else do muscle spindle endings respond to

Answer 39

vibration