Flashcards in Ch 11 - Musculoskeletal System Deck (57)
Contraction of what kind of muscle compresses venous and lymphatic systems ?
What are sarcomeres?
Arrangements of actin and myosin in repeating units - appears striated when viewed microscopically
(in skeletal muscle)
Is skeletal muscle UNI or MULTI nucleated?
Because muscle cells dude in long rods during development
Fibers within skeletal muscle:
Contract slowly but last longer (or posture)
High myoglobin content
Contract quickly but fatigue quickly
Contain less myoglobin
(Hence less iron, light color)
What is myoglobin?
An oxygen carrier that uses iron in a heme group to bond to oxygen (imparting a red color)
How is smooth muscle nucleated?
Has one nucleus in the middle of the cell
What is tonus?
A constant state of-low level contraction, in smooth muscle (ie vessel walls).
Smooth muscle is capable of more SUSTAINED contractions than skeletal muscle
What is my myogenic activity?
Muscle that an contract without input from the nervous system
In smooth muscle, the muscle cells can respond directly to stretch or other stimuli
In cardiac muscle, cells are able to define and maintain their own rhythm.
What kind of nucleation does cardiac muscle have?!
Mostly uni-nucleated but some cells have two nuclei
How are cardiac muscle cells connected?
Intercalated discs which have many gap junctions (allows flow of ions directly between cells)
*this is key for depolarization and contraction of cardiac muscle
What three biological systems play a role in the contraction of cardiac muscle?
Nervous - vagus nerve (parasympathetic) to slow the heart down
Endocrine - norepinephrine (sympathetic neurons) or epinephrine can increase heart rate and contractility
How does EPINEPHRINE act on cardiac muscle?
Increases intracelullar calcium levels within the myocytes (contractions rely on calcium)
Results in increased heard rate and greater contractility
Thick versus thin fibers: what proteins are in each?
Thick - MYOSIN
Thin - ACTIN, troponin, tropomyosin
Troponin and tropomyosin help regulate the interactions between actin and myosin filaments.
Lines if the sarcomeres zones:
Z line: the end of the sarcomere
M line: runs in the middle
I-band: area of only thin filaments
H-zone: area of only thick filaments
A-band: thick filaments in their entirety (incl overlap with thin filaments)
How do lines in the sarcomeres change during contraction?
H-zone, I-band, Z lines and M-lines become shorter (closer together)
The A - band stays the same (the actins get smaller but the myosin don't change length during contraction)
What is a myofibril?
Made up of sarcomeres end to end
Surrounded by the sarcoplasmic reticulum (modified ER) that has a HIGH CONCENTRATION OF CALCIUM IONS
What are he sarcoplasm and sarcolemma ?
Sarcoplasm: modified cytoplasm just outside the sarcoplasmic reticulum
Sarcolemma: the cell membrane of a myocyte
What is the role of the SARCOLEMMA?
How do T-tubules relate to the sarcolemma?
It can propagate action potentials
Can spread the action potential to all sarcomeres in a muscle through the use of transverse tubules (T-tubules) that are oriented perpendicularly to the myofibrils.
What is rhabdomyolysis ?
Physical trauma (compression) that destroys skeletal muscle tissue
What is rigor mortis?
ATP production stops after death
There is no ATP to bind with myosin and release the actin filament, so the muscle cannot relax and lengthen.
What is a simple twitch?
A SINGLE muscle fiber responding to stimulus at threshold.
What is the latent period?
What happens during this time?
The time between reaching threshold and the onset of contraction.
During this time, action potential spreads along the muscle and allows calcium to be release from the SR
What does summation if frequent simple twitches lead to?
The contractions can combine and become stronger and more prolonged, without sufficient time to relax.
This is called FREQUENCY SUMMATION and if there is no time at all to relax, leads to TETANUS
What is tetanus?
Disease versus physiological condition
What causes it?
Caused by clostridium tetani
Release a toxin, tetanospasmin
Blocks the release of GABA which inhibits motor neurons - hence motor neurons are overly excitable
Leads to constant contractions
Muscle contraction unable to relax
Results in muscle fatigue
Can result from simple twitches in succession
How do red (slow-twitch) muscle fibers make ATP?
They have LOTS of mitochondria, and use oxidative phosphorylation to MAKE ATP.
What is creatine phosphate?
A supplemental energy reserve
Transferring of a phosphate group to creatine during times of rest - reverse the reaction to generate ATP as needed!
Creatine + ATP ADP + cr. phosph
How do white (fast-twitch) fibers make ATP?
They have a lot less mitochondria - rely on GLYCOLYSIS and FERMENTATION to make ATP
What happens when muscles use ANAEROBIC metabolism to make energy?
The muscles need more oxygen that they are reviving! (Oxygen debt)
Lactic acid is produced
Lactic acid accumulation fatigues he muscle
After exercise, the body converts lactic acid back to pyruvate which can then enter the citric acid cycle. (This requires more oxygen!)
What is oxygen debt?
The amount of oxygen needed by the muscle versus the actual amount present
The "debt" is the difference the body has to make up AFTER strenuous exercise.