Motor System

Question 1

Anatomy of muscle fibres

Answer 1

Skeletal muscle fibre

made up of sarcolemma and sarcoplasm

one sarcolemma is a myofibril, made up of filaments

both thin and thick filament

Actin- Thin (ac-thin)
Myosin- Thick

Actin and myosin overlap and make up a sarcomere and Z lines

Question 2

what happens in the sarcomere during muscle contraction

in terms of fibres and filaments

Answer 2

Myosin heads Need atp

bond to binding sites on actin with their head,

troponin and tropomyosin moves off binding sites and the heads use ATP and pull Actin closer together to the M line and shorten the Sarcomere

POWER STROKE

then the heads detach and release ADP and get a new ATP

the myofibril and sarcomere shorten, but no the filaments

Question 3

Excitation contraction coupling

Basic and talking about myosin binding site, troponin

Answer 3

Ca2+ binds with Troponin, conformationally changing it and moving tropomyosin aside,

exposing actin myosin binding site,

allows head of myosin to attach and power stoke

pulls the sarcomere together and actin closer together

uses ATP then loses a P and detaches- relaxed
before next contraction get a P

Question 4

Exitation Contraction coupling

focusing on action potential, Ca2+ releasing, Sarcolemma

Answer 4

Sarcolemma wraps around a sarcomere and the muscle fibre

action potential reaches a muscle
ACh diffuses into motor plate open voltage Na channels which propagates action potential in sarcolemma

Action potential travels down sarcolemma and into the muscles via T tubules, where it reaches the triad

it reaching the triad released Ca2+ from the terminal cisternae in the sarcoplasmic reticulum into the sarcoplasm

The CONTRACTION CYCLE begins, and will continue to occur as long as ATP is available for myosin to pull the actin together

sarcomeres shorten and muscle contraction occur

Question 5

Different types of muscle fibres

Answer 5

There is a spectrum between the two extremes
Type 1
- slow twitch, light forces, quick recovery
Type 2A
- fast twitch, uses little energy and oxygen
Type2AB
- Fast twitch, less fatigue resistant
Type 2B
- Fast twitch, fatigue quick, recover slow

Question 6

What is a motor unit

Answer 6

A single alpha motor neuron innervates many muscle fibres

Question 7

what is a motor pool

Answer 7

all of the motor units innervating an entire muscle

distribution of lower motor neurons span multiple spinal segments

Question 8

Twitch contraction

Answer 8

Single Twitch:
When your brain sends a signal (an action potential) to a muscle, it activates a motor unit (a motor neuron and the muscle fibers it controls).
This signal causes the release of calcium in the muscle, leading to a brief contraction called a twitch.
After this quick contraction, the muscle relaxes.
Multiple Twitches = More Force:

If the brain sends more action potentials quickly, the twitches don’t have time to fully relax before the next one happens.
These twitches add up, or summate, making the muscle contract more forcefully.
The faster the signals come, the stronger the muscle contraction becomes. When the signals come very rapidly, the muscle stays contracted without relaxing. This is called tetanus and is a much stronger, sustained contraction.