Lecture 12 - Musculoskeletal physiology Flashcards
What are the four shared characteristics of muscles
- excitability
- contractability
- extensibility
- elasticity
What are the four important functions of muscle
- produce movement
- maintain posture and body position
- stabilize joints
- generate heat through contraction
What is the appearance and characteristics of:
skeletal muscle
striated, multi-nucleated peripherals
voluntary movement
Sarcolemma
muscle fiber plasma membrane that triggers action potentials
Sarcoplasm
muscle fiber cytoplasm
Myofibrils
Actin and myosin
Actin filaments
thin filaments containing troponin and tropomyosin
Myosin filaments
thick filaments
How are skeletal muscle fibers categorized
speed of contraction (slow or fast) and metabolic pathway (oxidative or glycolytic)
Myoglobin
protein within muscle that binds and stores oxygen; released and causes damage in rhabdomyolysis
What kind of job are slow oxidative fibers meant for? give an example
low-intensity endurance
distance walking
What kind of job are fast oxidative fibers meant for? give an example
medium intensity activities
sprinting
What kind of job are fast glycolytic fibers meant for? give an example
short term intense, powerful movements
hitting a grand slam
What is the appearance and characteristics of:
cardiac muscle
branched, uninucleated cells, connected by intercalated discs
involuntary movement
What cell junctions are in cardiac muscle
gap junctions (electrically couple cells) and desmosomes (hold together)
what muscle contains large numbers of mitochondria and why?
cardiac muscle; resistant to fatigue
What is the appearance and characteristics of:
Smooth Muscle
central nuclei in sheets, spindle-like cells
involuntary movement
T/F: Smooth muscle typically contains two layers - longitudinal and circular
True
What does the longitudinal layer of smooth muscle do
causes organ to shorten
What does the circular layer of smooth muscle do
lumen of the organ constricts
Varicosity
neuro-transmitter filled bulges that release neurotransmitters into the synaptic cleft in smooth muscles
Pacesetter cell
can spontaneously trigger action potentials and contractions in the smooth muscle
Summarize its role in contraction:
sarcolemma
site of action potential conduction that triggers contraction
Summarize its role in contraction:
sarcoplasmic reticulum
regulates levels of ionic calcium - releases when the muscle is stimulated
Summarize its role in contraction:
T Tubule
inward invagination of sarcolemma that allows for membrane potential to rapidly penetrate deep into the muscle fiber
Summarize its role in contraction:
Myosin
forms cross bridge and acts as a motor to generate force
Summarize its role in contraction:
ATP
prepares myosin for binding with actin by moving it to a higher-energy state and a “cocked” position
Where is the main storage site of glycogen
liver and muscle
Summarize its role in contraction:
Actin
covered by regulatory proteins (tropomyosin and troponin) until released and then binds to myosin for contraction
Summarize its role in contraction:
Troponin
3 subunits bind to tropomyosin, actin, and then calcium ions
Summarize its role in contraction:
Tropomyosin
stiffens and stabilizes actin
Summarize its role in contraction:
Calmodulin
SMOOTH MUSCLE
calcium-binding site
What are the four steps needed for skeletal muscle to contract
1 - nerve stimulation
2 - action potential generated in the sarcolemma
3 - action potential propagated
4 - intracellular calcium rises briefly
What is excitation-contraction coupling
link electrical signals to contraction (steps 3 and 4)
Myosin ____ and Actin _____
pulls; slides
What are the 4 steps of the cross-bridge cycle
Formation - myosin attaches to actin
Working (power) stroke - myosin pivots and pulls
Detachment - ATP attaches to myosin and causes detachment
Cocking - energy from hydrolysis of ATP puts myosin into a high-energy state
What is rigor mortis regarding contraction
absence of ATP that allows the release of cross-bridge
What are the 3 major differences in EC coupling between smooth and skeletal muscle
1 - calcium comes from the extracellular fluid
2 - calmodulin binds to calcium to active myosin
3 - slow contraction
T/F: Prior to successful cross bridge formation, calcium must bind to troponin in all muscle types.
False
Which of the following is NOT a characteristic of muscle:
a. flexible
b. excitable
c. rigid
c. rigid
