lecture2

Question 1

history

hippocrates, aristotle

Answer 1

brain is seat of sensation though action

Question 2

descartes

Answer 2

clockword motors responding to stimuli with predetermined motor outputs

Question 3

galvani & volta

Answer 3

involving electricity

Question 4

flourens, goltz

Answer 4

lesion studies - brainstem and spinal cord can generate motor acts.

Question 5

sechenov, pavloc

Answer 5

innate and conditioned reflexes

Question 6

eccles

Answer 6

intracellular recording

- synaptic transmission involved NT

Question 7

neher & sakkman =

Answer 7

patch clamping

Question 8

muscle
- how many neurons to muscle fibers
how many sensory axons signal force, how many signal pressure, temp rate

Answer 8

• 200 axons of 1 -MN activate msucle fibers
  200 sensory signal force
  200 sensory signal pressure, temp rate

Question 9

what is motor unit

Answer 9

one nerve and all the muscle fibers it innervates

Question 10

innervation ratio

smaller?

Answer 10

smaller = finer gradation of control

Question 11

muscle force controlled by?

Answer 11

varying number of active motor units and varying their individuals firing rates

Question 12

define passive force

active force

Answer 12

p: due to stretching of elastic
a: myosin cross-bridge attach to actin and swivel, generating “power stroke”

Question 13

sliding filament theory

Answer 13

cross-bridge attachs, swivel, release, swivel back and re-attach
AKA cross-bridge cycle

Question 14

isometric
eccentric
concentric

Answer 14

I: force produced without muscle length change
E: force produced during muscle lengthening
C: force producd during muscle sortening

Question 15

total force

elastic elements

Answer 15

T: sum of active and passive forces
E: force produced by elastic resistance of connectin and tendon

Question 16

force depends non-linearly on muscle length

- experiments

Answer 16

1. slow stretch from shortest length = produce passive length-force curve.
2. stimulating muscles nerve, activate muscle & measure force.
   = after certain force, cross bridges too far extended. cant produce force.

Question 17

force depends non-linearly on velocity

Answer 17

stimulate muscle via nerve and measure force at given length.
- repeat for different lengthening and shortening velocities.
= force highest during rapid lengthenin and lowest during rapid shortening.
* velocity = time for crossbridge to attach, detach swing.
- shorter cycle = larger relative duration of unattached phase (consistent)

Question 18

length-force depends on level of muscle activation

experiment

• larger sitmulation amplitude = MN’s =?
• MU?

Answer 18

force vs length at different amplitudes of stimulation of muscle nerve.
larger stimulation amplitude, the more MNs are recruited, so the greater the active force. slope increase
- depends on MU, recruited in order of size.

Question 19

force depends non-linearly on MN firing rates

- muscular wisdom

Answer 19

isometric - stimulated with increasing pulse rate. ratte increases = twitch force becomes smooth = tetanic contraction

• CNS matches MN firing rates to musce properties

Question 20

force and its many relationships

Answer 20

A force depends non-linearly on muslce length
B non-linearly on velocity
C length-force depends on level of muscle activation
D force depends non-linearly on MN firing rates.

Question 21

3 types of neurons

Answer 21

S = small, slow, fatigue-resistant
FFR= fast, fatigue-resistant
FF = fast, fatiguable

Question 22

% MUS recruited & force

Answer 22

90% of MUS recruited generate first 50% of force.

remaining 10% of force = 2nd 50% of force.

Question 23

fatigue of muscle,

rate of decline depends on?

Answer 23

muscle activated by long train to its nerve, force declines.
- rate of decline depends on muscle fibre types.

Question 24

muscle order of stimulation in voluntary contractiong

- vs how nerves stimulated electrically

Answer 24

• voluntary = S, FFR, FF
  electrically = FF FFR, S

this is why electrically-evoked fatigue more rapidly than voluntary contractions.

Question 25

CNS control actuator that are so nonlinear?
solution:
what areas of CNS?
sensory receptors?
delay?

Answer 25

feedback control. - feedback minimze error between desired and actual output.
- mediated thru brain, cerebellum, brainstem
-sensory give feedback, singal position. output compared to desired - difference is minimized
delay = instability/ oscillation

Question 26

reflex control of leg movments

Answer 26

1. sensory organ stretched
2. feedback from sense to NS, activate MN = activate muscle to move leg.
3. neuromuscular delay results in increasing phas lag as frequency of stretches increases