Physiology Lecture 4 Flashcards
ICU patients can lose up to _% every __ hours.
1% every 24 hours
The sooner they are mobilized, the less muscle mass lost
Difference between exercise and physical activity
Exercise is planned, structured, repetitive and purposeful activity.
Physical activity is any movement of the body that requires energy expenditure
7 functions of muscle
- Produces body movement
- Helps to maintain posture
- Powers respiration
- Produces body heat (shivering)
- Communicates with other organs and organ systems
- Constricts organs and blood vessels (smooth muscle)
- Produces cardiac contraction (cardiac muscle)
What is contractility?
Ability of a muscle to shorten or attempt to shorten.
What is excitability?
Capacity of muscle to respond to a stimulus.
What is extensibility?
Muscle can be stretched to its normal resting length and beyond to a limited degree
What is elasticity?
Ability of a muscle to recoil to original resting length after stretched
What are contractures?
A condition of shortening and hardening of muscles, tendons, or other tissue, often leading to deformity and rigidity of joints.
Too much internal scar tissue.
Reduces extensibility
Explain skeletal muscle
- Attached to and causes bones to move
- Multiple nuclei
- Striated
- Voluntary and involuntary
Explain cardiac muscle
- Found in heart
- Single central nucleus
- Striated
- Involuntary
What is a functional syncytium?
intercalated disks and gap junctions
Does every muscle cell in the heart have to be innervated?
No, but skeletal muscle cells do
Explain smooth muscle
- Lines walls of hollow organs
- Single nucleus
- Lacks striation
- Involuntary
- Fatigue resistant
Does every smooth muscle cell have to be innervated?
No
What is an isotonic contraction?
muscle changes length under a constant load
Concentric vs Eccentric
Conc- muscle shortens while contracting
Ecce- muscle lengthens while contracting
What is an isometric contraction?
Muscle length does not change while contracting
What is an isokinetic contraction?
Muscle shortens at a constant speed
Epimysium and perimysium
Epi- covers the surface of muscle and has a role in force transmission and insulation
Projects into muscle itself
Peri- divides the muscle fibers into functional groups called fascicles
Continuous with the epimysium
Individual muscle fibers are surrounded by what?
Endomysium
What is the endomysium connected to?
Basement membrane, which plays a role in force production
What is the Myotendinous Junction?
Weak point in the muscles, where muscle connects to tendon
Where is force generated?
By the cross-bridges in the sarcomere
Force is then transmitted to the costamere
What happens with rigor mortus?
there is no ATP to release crossbridging and calcium ions cant be pumped out of the cell
When does force production go down?
When thin filaments overlap, crossbridges cant attach to thick filament
List the order in which force gets to the tendon.
Sarcomere Costomere Endomysium Perimysium Epimysium Tendon
Increased force production comes from what?
Increase in sarcomeres
Difference between Type I and Type II muscle fibers
Type I- slow twitch, more mitochondria for aerobic
Type II- fast twitch, glucose storers for anaerobic capacity
What is the longest muscle in the body?
Sartoris
What do the I,A and H band consist of
I band has the thin filaments only
A band contains thick filaments with some thin filament overlap
H band is within the A band and only has the thick filament
What forms the boundary of a sarcomere?
Z disc
Thick filaments are composed of?
Thin filaments are composed of?
Myosin
Actin
What prevents myosin from binding at rest?
Tropomyosin and troponin
General movement of AP to a muscle cell
L5S4
-Presynaptic nerve cell synapses with a muscle cell
-ACh is released and binds with receptors on motor end plate of muscle cell
-AP propogates down t-tubule
-Binds to a receptor in the tubule that induces the release of calcium from the sarcoplasmic reticulum
-Calcium seeks binding sites on thin filaments
Crossbridges can now bind to the thin filaments
What reabsorbs calcium so crossbridges can relax?
Sarcoplasmic reticulum
