Bio 1- L23- Muscle Physiology

types of muscles

1. skeletal- voluntary movement

2. smooth muscle- involuntary body activities

3. cardiac- contraction of the heart

how does skeletal muscle work?

• bundle of long fibres- a single cell along the length of muscle

• each fibre- bundle of myofibrils

• striped muscle- light and dark bands

• functional unit- sarcomere

what is locomotion

the movement through space

what are muscles dependent on

• ATP

• muscles fatigue from a lack of ATP

• glycolysis needed to make ATP- when exercising oxygen is limiting

what are muscle contractions dependent on?

• calcium

• regulatory uscke- tropomyosin- bind to actin on thin filaments at rest

• myosin binding sites are exposed by calcium- contraction

what else is skeletal muscle contraction dependent on?

• motor nerves

  1. contraction- action potential needed- synapse with muscle fibre

  2. synaptic- releases ACH- depolarisation and causes action potential

  3. action potential- makes sarcoplasmic reticulum release calcium

  4. calcium binds to troponin- exposes myosin

what does calcium bind to?

• troponin- exposes the myosin binding site for contraction

how does the nervous system produce graded contractions?

• varies the number of fibres contracting

• varies the rate at which fibres are stimulated

disorders related to the skeletal muscle

• motor neuron disease- muscles weaken

• myasthenia gravis- autoimmmune- attacks ACH on muscle- muscles weaken- cholinesterase treatment

• MS- disorder of CNS

• muscular dystrophy- X linked- no muscle protein

cardiac muscle- basic info

• striped cells- electrically connected- have gap junctions

• make action potentials without neural input

• does not fatigue

smooth muscle- basic info

• found in hollow organs- digestive, circulatory, reproductive

• stimulated by autonomic or initiated by muscles themselves

• aren’t arrayed regularly iike skeletal