l15

Question 1

what is proprioception

Answer 1

sensing where parts of our bodys are in 3D space

Question 2

what are the 3 mechanoreceptors involved in proprioception

Answer 2

muscle spidndles
golgi tendon organs
ruffini endings

Question 3

piezo 2 in proprioception

Answer 3

mechano- only encodes transduction at low levels and doesnt do much at high
has much greater effect in proprioception, without it you lose ability to know where body is in space

Question 4

muscle spindles

Answer 4

extrafusal: buls of muscle, force generating
intrafusal: sense stretch of muscle
2 kinds- nuclear chain and bag

Question 5

glut role in afferants

Answer 5

found vesicular glutamate 1 (important for pumping glutamate in) - shouldnt need because its afferant
- turn sout glutamate doesnt act on muscle but instead amplifies response on nerve ending (increases afferant activity)

Question 6

FM labelling

Answer 6

found synaptic vesicles in primary afferants using FM dye labelling

• mechanosensitive channels open and cause vesicle release
• calcium dependant (without calcium there isnt release)

Question 7

how did they disprove Na selective channels

Answer 7

measured current and changed holding potential

if it were Na the reversal potential would be +60 but it was closer to 0

Question 8

how did they discover piezo

Answer 8

knocked out in mice and lost current

Question 9

is piezo2 requried for proprioception

Answer 9

yes- phenotype of knockout shows no sense of where legs are

Question 10

what is the role of y motor neurons

Answer 10

why send a motor neuron if they dont generate force?

- role is to control and restore tension of spindle in intrafusal muscle to keep 1a afferant near threshold

Question 11

monosynaptic stretch reflex circuitry

Answer 11

direct synapse with alpha motor neuron that comes back to same muscle (homonymous muscle)
there is also interneuron to antagonist muscle
- with passive stretch causes contraction to keep hand in constant position and also relax antagonistic muscle

Question 12

withdrawal circuitry

Answer 12

dont make monosynaptic contacts- not the same as reflexes because they go through several synapses first

Question 13

golgi tendon organ

Answer 13

bag and chain sit in parallel with eachother- GTO in series

• slowly adapting
• codes muscle TENSION
• insensitive to stretch

Question 14

regulation of muscle tension

Answer 14

relaxes muscle when heavy load encounter to prevent damage

• decrease activity in homogenous muscle
• for low levels of force helps maintain steady tone

Question 15

dorsal spinocerebellar pathway

Answer 15

proprioceptive pathway to cerebellum

• important for balance, posture and motor control
• synapse in Clarkes nucleus