muscles booklet Flashcards
(40 cards)
3 purposes the refractory period serves
AP can only travel in one direction - discrete (separate) impulses are produced - limited number of APs produced
ATP use in sliding filament theroy
ATP binding is required for the myosin heads to release the actin filament. Hydrolysis of ATP provides the energy required to change the angle of the myosin head causing the actin filament to slide along (the power stroke)
All or nothing meaning
If stimulus is not large enough to open enough sodium gates for the generator potential to reach threshold no action potential will be generated. * If stimulus is large enough to result in the generation of the threshold potential then an action potential will be generated.
EPSP meaning
(excitatory post synaptic potential).
EPSP role/how it works
A single action potential will result in a small depolarisation EPSP. This may not be sufficient to generate an action potential. Multiple AP in presynaptic neurone may be required to produce an action potential in the post synaptic neurone.
IPSP meaning
inhibitory post synaptic potentials
Relay neurone role
Relay neurone role / connect sensory and motor neurones inside the CNS
axon diameters effect on speed of action potential / The larger the axon diameter the faster the transmission. * Reduced ion leakage
description of saltatory conduction
- the myelin sheath is an insulating layer of fatty material made up of from Schwann cells. The gaps between these cells, called nodes of ranvier, are the only places that iconic exchange may occur - in myelinated neurones the Na+ ions diffuse from one node of ranvier to the next in elongated local currents - meaning AP appears to jump from one node to the next Lone as saktatory conductions
divergence description plus example / events occuring during an action potential
- The membrane starts polarised with the inside of the cell being -65 mV compared to the outside (resting potential).
- Sodium channels open and some sodium ions diffuse into the cell and create a generator potential.
- The membrane depolarises as it becomes less negative and reaches the threshold potential value (-50 mV).
- Voltage-gated sodium ion channels open and more sodium ions diffuse in and the cell becomes positively charged inside compared with the outside.
- The potential difference across the plasma membrane reaches +40 mV.
- The sodium ion channels close and potassium ion channels open. 7. Potassium ions diffuse out of the cell bringing the potential difference back to negative – repolarisation.
- The potential difference overshoots slightly before the potassium channels close, making the cell hyperpolarised. This creates a refractory period during which time it is not possible to create another action potential.
- The original resting potential is restored by the sodium potassium pump.
events that reasult in relaxation of muscle following a conctraction
When the action potentials stop ACh is broken down by acetylcholinesterase The sarcolemma returns to its polarised state Calcium ions are pumped back into the SR Myosin heads are no longer able to form crossbridges with the actin The sarcomere returns to its original length.
events that reasultin relaxation of muscels following a conctraction
when AP stops - ACh is broken down by acetylcholinestererase - sarcolemma returns to its polarised state - Ca 2+ ions are pumped back into SR - myosin heads no longer able to form crossbriges with actin - sarcomere returns to its orininal length
evidence supporting sliding filament theory
- transmission electron microscope (TEM) - differences in bands of the sarcomere + Z lines will move closer - I bands will get shorted - A will stay the same - H will get shorter
fast twitch fibre roles
Faster, more powerful contractions. Brief, intense periods of exercise such as weight lifting, sprinting etc. Located in muscles more likely to perform these tasks (biceps). Anaerobic respiration
fast twitch fibres adaptions
Thicker more numerous actin and myosin fibres. Higher glycogen concentrations Higher concentrations of enzymes involved in anaerobic respiration (rapid production of ATP). Phosphocreatine source (donates phosphate group to regenerate ATP)
how does size of stimulus change AP
size of stimulis is reflected by the frequency of the action potential it generates
how is ACh recycled
ACh ——> ethanoic acid + choline (by acetylcholinesterase) an ezyme - stops tranmission of signals/production of AP - then Ethanoic acid + choline recycled with ATP forms ACh which is an active process so lots of mitrochondria needed
if finer motor control needed…
less fibres are needed (like eye movements)
if greater strength of contraction required…
there will be multiple muscle fibres controlled by a single motor neurone (like quadriceps)
inhibitory neurotransmitters effect/description
Some neurones produce inhibitory post synaptic potentials that might reduce the effect of action potentials arriving from other neurones. The neurotransmitter GABA binds receptors on Cl- ion channels which open andallow the Cl- ions to diffuse in by facilitated diffusion. This opens the K+ channels and the K+ diffuse out. reasulting in hyperpolarisation
mV of threshold of AP
-50 mV
main advantage of saltatory conduction
it a lot faster
motor neurone role
carry action potential from relay neurone in the CNS to effectors
motor unit definition
the number of muscle fibres stimulated by a single motor neurone
myelinated neurone role
- High speed saltatory conduction (100-120m/s)
- Carry signals from sensory receptor to CNS
- Carry signals from CNS to effectors
- Carry signals over long distances (up to 1m)
- Enable rapid response to stimulus
