Movement 1&2 Flashcards
WHat types of movement do lower motor neurons control
both reflexive and voluntary
location of soma, axon and synapses of LMS
soma: gray matter of spinal cord
axon: dorsal root
synapses: muscle fibre
define: motor unit
LMN and all the muscle fibres it innervates
define: motor neuron pool
all LMNs innervating muscle fibres of a particular muscle.
describe rate coding, (un)fused tetanus
rate of AP determines force.
unfused tetanus: lower rate, so bumps in force/time graph
fused tetanus: faster rate, smooth
describe size principle
involves size of motor units
small vs large motor units
small: LMN which has small cell body and innervates fewer muscle fibres (<10)
large: large cell body, innervates many muscle fibres (,1000)
why are small motor units recruited first to generate graded forces
V=IR
I = current: same
R= resistance: larger for low SA hence small motor units
therefore, small motor units reach threshold easier and hence are recruited first
describe proportional control
many small motor units which generate less force, and fewer large motor units, which generate more force
what happens during excitation?
AP stimulates Acl release from presynaptic neuron, which binds to receptor on muscle fibre.
ions go in, then volage gated Na+ channels open.
AP goes along transverse tubules, opens up dihyropyridine receptors and then ryanodine receptors, triggering release of Ca2+ from lateral sac of sarcoplasmic reticulum.
what happens during contraction
Myosin head has ADP and Pi attached (energised)
Tropomyosin shields myosin from actin. Ca2+ causes troponin to move tropomyosin, enabling binding of myosin head to actin.
Power stroke happens, ADp and Pi released
ATP binds, breaking actin-myosin bond
ATP hydrolyses and cycle continues.
how does contraction stop
Ca2+-ATPase carries Ca2+ back into sarcoplasmic reticulum.
describe myofibril/sarcomere structure
LOL
describe the length/tension relationship
optimum tension at a medium length.
isotonic definition and graph of time vs distance shortened?
same tension, different lenght.
takes time for length to shorten, as enough cross bridges must be formed to counteract the load.
finishes as soon as load returns to resting position
isometric definition and time vs tension graph?
same length, increased tension.
increases tension right away
takes time for tension to return to normal as Ca2+ must be seuestered
describe concentric
muscle shortens as tension increases, as cross bridge forms further up actin, leading to shortening
describe eccentric
muscle increases in length as tension increases due to external pressure.
factors determining the three types of muscle fibres?
maximum shortening velocity
-type i: slow, low ATPase activity
-type ii: fast, high ATPase activity
whether glycolytic or oxidative
what are the three muscle fibre types
- Type I – slow oxidative
- Type IIa – fast oxidative-glycolytic
- Type IIb – fast glycolytic
order of recruitment of the 3 types of muscle fibres?
1 –> 11a –> 11b
because they correspond to small/large motor units.
muscle fibres of one motor unit are…
of the same type
a whole muscle tissue contains
different combinations of each muscle fibre type, depending on its needs.
what happens when slow motor neurons are forced to innervate fast muscle?
changed from type ii to type i fibres; hence changed from a coral colour to a deep red
what happens when muscle fibres are stimulated with a lower rate of AP?
diameter of muscle fibres decreased
effect of curare
nicotonic Acl receptor antagonist
effect of atropine
muscarinic Acl receptor antagonist
effect of Latrotoxin
massive release of Acl, norepinephrine and GABA
effect of botox?
prevents Acl release.
during experiment three, what nerve was stimulated, which affected which muscle?
ulnar nerve hypothenar muscle (moves little finger)
where is the ulnar nerve best stimulated and why
near funny bone/forearm - little fat and close to surface.
how is AP produced?
using a stimulating bar
how do we measure effect of AP?
EMG - detects, amplifies and records electircal activity of hypothenar muscle
transducer: detects force of little finger.
