Please enable JavaScript.
Coggle requires JavaScript to display documents.
Anatomy and Physiology lesson 8 onwards (Muscle fibres (Motor unit…
Anatomy and Physiology lesson 8 onwards
Muscle fibres
Motor unit
Consists of a motor neurone and the muscle fibres it stimulates
Muscle fibres work with nervous system so that a contraction can occur
Motor neurone transmits nerve impulse to each muscle fibre
Each muscle is made up of many motor units that vary in size and type
Only one type of muscle fibre can be found in one particular motor unit
Small muscle, motor units with few fibres per neurone
Large muscle, motor units with a motor neurone feeding 100s fibres
All or none law
A minimum amount of stimulation
the threshold
is required to start contraction
If sequence equal or more than threshold all fibres will contract
Cant partially contract
If sequence less than threshold, no muscle action will occur
Once stimulated all muscles fibres contract or none
Types of muscle fibres
Type I(Slow twitch
Functional characteristics
Slow motor neurone conduction speed
Low force production
Slow contraction speed
Low fatigability
Metabolic characteristics
Low ATP ASE activity
Very high aerobic capacity
Low glycogen stores
Low anaerobic capacity
Low PC stores
Structural characteristics
High mitochondrial density
High capillary density
Small diameter
High myoglobin content
Type IIA(Fast twitch)
Functional characteristics
Fast motor neurone conduction speed
High force production
Fast contraction speed
Intermediate fatigability
Metabolic characteristics
High ATP ASE activity
Intermediate aerobic capacity
High glycogen stores
High anaerobic capacity
High PC stores
Structural characteristics
Intermediate mitochondrial density
Intermediate capillary density
Intermediate myoglobin content
Large diameter
Type IIX(Fast twitch)
Functional characteristics
Fast motor neurone conduction speed
High force production
Fast contraction speed
High fatigability
Metabolic characteristics
Very high ATP ASE activity
Low aerobic capacity
Very high glycogen stores
Very high anaerobic capacity
Very high PC stores
Structural activity
Low capillary density
Low myoglobin content
Low mitochondrial density
Large diameter
How to vary force of muscular contraction
3. Types of muscle fibres recruited
- Fast twitch for powerful actions rather than slow twitch
4. All or none law
-Once a threshold is reached all contract, if less than threshold none will contract
2.Number of motor units recruited
-
Multiple unit summation
- more recruited for more powerful actions
5.Frequency of impulse
-
Wave summantion
- greater force, muscle repeatedly stimulated, unable to relax. Produces forceful contraction called
Tectanic contraction
Spatial summation
- Some contract some relax, delaying fatigue
1. size of motor units recruited
-larger motor units recruited for larger more powerful actions
6. Proprioceptors
-
Muscle spindles
detect change in muscle length/speed of contraction. Then send info to brain which compares info to memory to ensure correct force applied based on past experiences
PNF
CRAC Technique
Hold stretch for 30 seconds
Contract muscle group isometrically for 10 seconds
Stretch target muscle to full range of movement
Allow muscles to relax
Find a partner
Stretch target muscles again
Role of proprioceptors
Muscle spindles
Detect increase in muscle length.
CNS sends back to muscle telling it to contract, causing stretch reflex
Muscle contracts preventing over stretching, reducing risk of injury
Role in PNF
- Detect change in muscle length, causes stretch reflex
Golgi tendons
Cause muscle to relax- autogenic inhibition
Stretch reflex inhibited
Detect increase in tension of muscle
Allows greater range of movement which is greater than initial stretch
Benefits of PNF
Better range of motion, greater flexibility
Looks more aesthetically pleasing
Helps prevent injury-overstretching
Muscular skeletal
Types of muscle contraction
Eccentric
This is when the muscle lengthens under tension and does not relax. Downwards phase of a bicep curl, bicep contract eccentrically to lower the weight slowly resisting gravity
Isometric
Muscle contracts with no movement occurring, holding weight part way through a bicep curl. Isometric contraction by bicep, holding weight, resisting gravity.
Concentric
This is when a muscle shortens under tension. E.g upwards phase of a bicep cur, bicep performs concentric contraction to flex at elbow
Joint action
Abduction
- Movement of limb away from midline
Adduction
-Movement of limb towards midline
Hyper extension
- Increasing angle above 180 degrees
Horizontal adduction
- Movement of arm to front of body horizontally
Extension
- Increasing angle at joint
Horizontal abduction
-Movement of arm towards back of body horizontally
Flexion
- Decreasing angle at joint
Plantar flexion
- Pointing toes/standing on tip toes
Dorsi flexion
Pulling toes upto sky
Planes
Frontal
Divides body into front and back
Movements: Adduction, abduction
Transverse
Divides body into upper and lower
Movements: Horizontal adduction, Horizontal abduction
Sagittal
Divides body into left and right
Movements: Flexion, extension, plantar flexion, dorsi flexion, hyper extension
Axes
Sagittal
Runs front to back
Adduction, abduction
Transverse
Runs side to side
Flexion, extension, hyper extension, dorsi flexion, plantar flexion
Longitudinal
Runs top to bottom
Horizontal adduction, horizontal abduction
STF, FSA, TLH