Muscle Physiology Flashcards
What is the structure of skeletal muscle?
whole muscle< fascicles< muscle cells/fibres< myofibrils< myofilaments
What are the two types of myofilaments?
thin and thick
What is the structure of skeletal muscle?
diagram page 148
What is the sarcolemma?
surrounds the cell membrane
What do the transverse tubules do?
- continuation of the sarcolemma that travels down into the muscle cell and wrap around each myofibrils
- allow the AP to travel from the surface of the sarcolemma into the muscle cell where the contractile proteins are located
What do the sarcoplasmic reticulum do? (SR)
wrap around myofibrils
- Ca is stored
- the portion of the SR that comes in contact with the T-tubule is called the lateral sac
What is the structure of a thin myofilament?
diagram page 150
What are the 3 contractile proteins in thin myofilaments?
- G- Actin: contains myosin binding sites
- tropomyosin: partially covers myosin binding sites
- troponin: positions tropomyosin over binding sites until Ca++ arrives and rips it off
What is the structure of a thick myofilament?
diagram page 151
What is the actin/myosin relationship?
diagram page 152
What is the smallest functional unit of the muscle cell?
sarcromere
When does a cross bridge form?
when a myosin head attaches to an actin molecule, when this occurs a power stroke is initiated and a contraction will occur
What events happen during the sliding filament theory?
- when myosin head binds to an actin a cross-bridge is formed
- myosin then changes shape and a peer stroke occurs
- actin slides past myosin
What is the sliding filament theory?
the only structure that changes length in the muscle during a contraction is the sarcomere, not the thin or thick myofilaments
What happens during neuromuscular transmission?
1 AP in the motor nerve will always produce 1 AP on the muscle cell membrane (sarcolemma)
steps and diagram page 155-156
What is excitation- contraction coupling?
process by which an AP in the sarcolemma leads to the release of Ca++ from the SR, cross bridge activity and contraction
-the AP triggers the release of Ca++ from the lateral sac of the SR
What are the events that occur during excitation- contraction coupling?
diagram and steps page 158
What are the steps in the actin-myosin ATP cycle?
diagram page 159
What is rigor mortis?
stiffening of muscles after death
-begins 3-4 hours after death and is complete about 12 hrs after death
What is the cause of rigor mortis?
No O2-> no ATP
no ATP-> no Ca++ being pumped back into the SR
no ATP-> actin and myosin can’t dissociate, muscle is permanently fused into muscle starts decomposing
What are the 2ways that the muscle can alter the force of contraction?
- summation of twitch contraction- when you increase the frequency of AP, each muscle twitch has less time to relax causing a sustained contraction
- recruitment of motor units- as you increase the amount of motor units firing the contractile forces increase giving you a larger muscle twitch
What is a single muscle twitch?
muscle contraction in réponse to 1 AP on the motor neuron
