Functional Anatomy Flashcards
Order of Layers within a muscle belly
- Epimysium
- Muscle Belly
- Perimysium
- Fascicle
- Endomysium
- Muscle Fibres
- Myofibrils
- Sarcomere
- Myofilaments
Epimysium
Outer connective tissue that surrounds the muscle belly
Perimysium
Middle connective tissue that surrounds the fascicle
Endomysium
Inner connective tissue that surrounds the muscle fibres
Muscle Belly
The muscle as a whole
Fascicle
Bundle of muscle fibres surrounded by the perimysium
Muscle Fibres
Individual muscle cells
Myofibril
Individual strands of the muscle cell
Sarcomere
Contractile unit of skeletal muscle, from one z-line to another
Myofilament
Proteins of the myofibril (actin and myosin)
Z-lines
Ending of one sarcomere, beginning of another
Actin
Thin myofilament, attached to z-lines
Myosin
Thick myofilament
Myosin Crossbridges
Projections from myosin
H-ZOne
contains just myosin
I-Band
Contains just actin
A-Band
COntains both (length of myosin)
M-Line
Centre of the sarcomere
Eccentric
Muscle length extends
Concentric
Muscle length shortens
Outline the steps in sliding filament theory
- Neurochemical stimulations (acetylcholine) releases calcium from the Sarcoplasmic Reticulum
- Calcium ions bind to troponin, changing the shape of actin, which moves tropomyosin exposing actin binding sites
- Myosin heads attach to actin binding sites forming crossbridges
- The breakdown of ATP releases energy causing the crossbridges to pull actin towards the m-line (power stroke)
- Sarcomere shortens causing z-lines and h-zones to shorten as actin ‘slides’ over myosin.
- Crossbridges attach and reattach to produce movement and maintain tension
- When muscle impulse ends, muscle relaxes
Force-velocity relationship
Force produced is dependant on the velocity of the contraction, this is due to the amount of crossbridges. When there is slow velocity, a high amount of force is produced due to high numbers of crossbridges and a slow sarcomere contraction. When there is high velocity, a low amount of force is produced as there is low crossbridge numbers and a fast sarcomere contraction.
Force-muscle length relationship
Force produced is dependant on the starting length of a muscle. When a muscle is resting (in resting postition) there is optimal tension resulting in the greatest genertion of force, this is because there is optimal overlap between myosin and actin myofilaments. When a muscle is full contraction there is a lower generated force as overlap is too great and there is less crossbridge attachment. When a muscle is in full extension there is a lower generated force as overlap is too little and there is insufficient numbers of cross bridges.
Nervous System functions
-recieves information from the body and environment and sends this information to the brain and spinal cord
-brain determines most suitable response
-brain sends commands to muscles to carry out selected response
Central Nervous System is made up of?
Spinal Cord - sends information from the body to the brain and vice versa
Brain - analyses information recieved from a sensory neruon
- determines most suitable response
- sends a message to targeted muscles
What is the peripheral nervous system made of?
Sensory Division (Sensory Neurons) - carries meesages from the body and the environment to the CNS
Motor Division (Motor Neurons) - carries messages from the brain to the muscles to respond
All or none principle
When a motor unit receives a stimulus/action potential that exceeds their threshold, all associated muscle fibres contract to their maximum potential. Smaller units produce precise movements and require smaller AP’s. Larger units produce gross motor skills and require larger AP’s
Preferential Recruitment
1st - Slow Twitch
2nd - Fast Twitch IIa
3rd - Fast Twitch IIb
Ways to increase force production
- increase number of motor units recruited by increasing stimulus size
-increase frequency of impulses
