Skeletal Muscle Function Flashcards
What are 5 aspects of skeletal muscle
Striated or visibly layered
Voluntary
Very fast to medium contraction speed
Causes physical movement or locomotion
Main muscle groups of the body
What does skeletal muscle move
Bones by operating as levers with muscle pairs
How much body mass is skeletal muscle
40%
What happens during contraction
All muscle types use ATP for energy and change Ca 2+ concentration stimulus to contact
What does Ca 2+ bind to
Troponin and causes conformational changes which exposes the myosin binding sites of actin (thin) allowing the myosin heads (thick) to bind, pulling the thick filament over the thin
What are the 4 steps during skeletal muscle function
Myosin cross bridge attaches to the actin myofilament
Working stroke - the myosin head pivots and bends as it pulls on the actin filament sliding it towards the M line
As new ATP attaches to the myosin head the cross bridge detaches
As ATP is split into ADP and Pi cocking of the myosin head occurs
What does ATP do during skeletal muscle function
Energising the power stroke on myosin cross bridge
Returning of myosin head to the resting position
Active transport of Ca 2+ into SR
What are the sensory receptors in skeletal muscle reflexes
Proprioceptors in skeletal muscle, joints and ligaments
Role is monitoring the position of our limbs in space and our movements
What do sensory neurons do in skeletal muscle reflexes
Carry the signal from proprioceptors to CNS
What does the CNS do during skeletal muscle reflexes
Spinal cord or cerebral cortex integrates signals
What does the somatic motor neurons do during skeletal muscle reflexes
Carry the output signal
Motor neurons that innervate contractile extrafusal fibres are called a motor neurons
What do effectors do during skeletal muscle reflexes
Are contractile elements called extrafusal fibres
What are the 5 stages in skeletal muscle reflexes
Sensory receptors
Sensory neurons
The CNS
Somatic motor neurons
Effectors
What are 4 constituents of proprioceptors
Muscle spindles
Golgi tendon organs
Joints
Skin sensors
What are the 2 types of skeletal muscle fibres
Intrafusal
Extrafusal
What does extrafusal generate
The force for contraction
What does intrafusal do
Are sensory and monitor changes in muscle length they can contract but don’t contribute much to force of contraction
What do muscle spindles contain
Intrafusal fibres
What are intrafusal fibres surrounded by
Extrafusal (contractile fibres)
Where are the Golgi tendon organs (GTOs) located
At the junction between skeletal muscle and a tendon (tendons tether muscles to bones) and respond to muscle tension
What are Golgi tendon organs made of
Connective tissue capsule filled with collagen fibres interwoven with sensory nerve endings
What happens to the Golgi tendon organs during muscle contraction
Collagen fibres are pulled tight compressing nerve endings, opening mechanosensitive channels and increasing firing rates of inhibitory interneurons in the spinal cord
What are 4 autonomic reflex control muscle movements
Stretch reflex - myotatic or deep tendon reflex
Golgi tendon reflex - inverse myotatic
Flexion reflex - withdrawal
Flexion and crossed extension reflex
What does the stretch reflex prevent
Inappropriate changes in muscle length, maintaining posture
Which organ helps with muscle contraction
Muscle spindle is stretched
Which organs helps with muscle relaxation
GTO in contracting muscle
What does the Flexion reflex do
Pulls limbs away from painful stimuli
Nociceptors send signal to spinal cord
A motor neurons cause contraction of flexors
Antagonistic muscle is inhibited and relaxes
Resulting in Flexion of the limb and withdrawal form stimulus = reciprocal inhibition
What does postural reflex do
Maintain balance
What happens when the left leg is braced and extended
Flexors relax and extensors contract
What are a - alpha nerve fibres carried by
Proprioception
What are a - beta nerve fibres carried by
Touch
What are a - delta nerve fibres carried for
Pain mechanical and thermal
What are C nerve fibres carried for
Pain mechanical, thermal and chemical
Which nerve fibre type is non myelinated
C fibres
Which cranial nerve if damaged will alter gag and swallowing reflexes
Glossopharyngeal
