Muscle - Lecture 3 Flashcards
What happens when calcium leaves the sarcoplasmic reticulum (SR)
Binds to troponin (bound on thin filaments - actin). Troponin part of calcium binding familiy of protein and becomes active.
What happens after troponin becomes active (has bound calcium)
Change in conformation releases tropomyosin that was wrapped around the actin
What the release of tropomyosin from actin filaments allows
Liberates the actin molecule’s binding site for myosin head groups
How muscle comes back to a relaxed state after release of calcium from the SR
Calcium is pumped back into the SR so troponin and tropomyosin back in place
What is a twitch
A contraction of a muscle fiber in response to a single AP
Why a twitch lags (little gap before AP and contraction)
Because of the series of events that must happen between AP and muscle contraction
What is reflected by the duration of contraction (from a single AP)
The time that it takes for calcium concentration to return to baseline
Name of the force generated by a muscle and the two things that control it
Tension.
Is controlled by Recruitment and Summation
Skeletal muscle what it is adapted for (how much force and how large its functional range is)
Adapted for large force generation over a narrow operating range
Recruitment def.
Varying the number of muscle fibers involved in a contraction
By what mechanism do muscles vary the force of their actions
By recruitment
Motor units can be _____ or ______ but recruitment would involve putting more _______ to work and not _________ them
small or large. (more or less muscle fibers for a single motor neuron).
Recruitment : Put more motor units (so motor neurons) to work and not more muscle fibers per motor unit
Summation def. + what it applies to
Additive effects of several closely spaced twitches. APPLIES TO ONE MUSCLE FIBER
The closest the twitches, the higher the ___________
relative muscle tension
What is called the sustained contraction of a muscle fiber and what is necessary to get to it
Fused tetanus. Need close enough APs
What is the converse of a fused tetanus and when does it happen
Unfused tetanus : Happens when close twitches but not close enough. APs fired a little more frequently than the duration of the twitch
In an active muscle, individual fibers can either be ______ or _______
relaxed or contracted
Fused tetanus tension how much greater than twitch tension
3x greater
How ATP rate in muscle fiber changes over multiple twitches and why
Stays the same because rate of use = rate of production
What molecule changes ADP back to ATP and what it happens to it after this change
Creatine phosphate. Is a Pi storage molecule. After putting a phosphate on ADP to make it ATP, becomes creatine
Which enzyme is involved in creatine phosphate -> creatine / ADP –> ATP
Creatine kinase
How long creatine phosphate can sustain ATP formation in the cell and why
only a couple seconds because of the amount of creatine phosphate in the cell.
What does the creatine phosphate mechanism lasting a couple seconds serve for
Provides time for a more standard metabolic system to take over and produce ATP
Which molecule does the muscle fiber use for a sustained source of energy
Glucose
Where does the muscle fiber take its glucose from (2)
From glycogen that it stores and when runs out of it, from the glucose in the blood
2 processes that use glucose to produce ATP in the muscle fiber
Glycolysis and oxidative phosphorylation
Glycolysis where and what + O2 or not
Cytoplasm. Uses glucose to convert ADP + Pi into ATP. NO O2 REQUIRED
Oxidative phosphorylation where and what + O2 or not + waste
Mitochondria. Uses glucose to convert ADP + Pi into ATP. Waste : Lactic acid. Uses O2 !!
What other substance oxidative phosphorylation can use to convert ADP + Pi to ATP and where does it take it
Fatty acids. From blood
Types of SKELETAL muscle fibers (3)
Fast glycolytic fibers.
Slow oxidative fibers
Fast oxidative fibers
Slow oxidative fibers : Duration and relative tension + why
Low levels of force over long time. Myosin with low ATPase activity
Special molecule found in slow oxidative fibers + what it does
Myoglobin : Facilitates OXYGEN transport from blood to muscle fiber. Is an oxygen-binding molecule
Colour of slow oxidative fibers and why
Red because of myoglobin
Fast glycolytic fibers : Force/Time of tension + why called fast
Large forces over short periods of time. Fast because myosin with high ATP activity
What fast glycolytic fibers use (which mechanism and which resource)
Use only glycogen from the muscle fiber (no glucose from blood) and use only glycolysis
Consequence of fast glycolytic fibers using only glycolysis + colour and why
Lot of lactic acid produced.
Have a white colour because no myoglobin is used
Fast oxidative fibers what they use/why this name
Intermediate properties. Fast myosin (high ATPase activity myosin) and oxidative metabolism
Muscle fibers are generally a _______ of different types of _________ but there is usually _______ that is/are higher in proportion
mixture. skeletal muscle fibers. Usually one in higher proportion
Muscle fatigue : Why and what DOES NOT cause it.
To protect muscle from damage. Not caused by depletion of ATP because that would cause rigor mortis
Possible explanations (2) for fatigue in high intensity short duration activity
1) Change in ion gradients (increase in extracellular potassium)
2) Reduction of pH due to lactic acid build up
Possible explanation for fatigue in low intensity long duration activity
Depletion of glycogen
Other possible explanation for muscle fatigue
Central command fatigue. Failure of command signals from CNS
Change in muscle physiology after high-intensity short duration exercise + which type of skel. fiber used
Fibers make more myofibrils : muscle fatter abd stronger. Fast glycolytic fibers are the ones used
Change in muscle physiology after low-intensity long duration exercise + which type of skel. fiber used
Development of the structures like myoglobin/mitochondria that increase the efficiency of ATP extraction from oxidative metabolism. Slow oxidative fibers used
Smooth muscle diff. with skeletal muscle
No stripes cause not highly ordered arrangement of actin/myosin, no sarcomere. Not as much force as rapidly as skel.
Smooth muscle similarity with skel. muscle
Still uses actin and myosin (just not organized)
Smooth muscle : Cell shape + Actin/myosin organization
Look like normal cells. Not elongated like muscle fiber
Actin stretched on cell length and myosin walks along thin filaments to pull cell shorter
What ANS does and 2 types of muscle it controls
Controls internal organs. Controls cardiac muscle and smooth muscle
ANS is intimately connected to the process of __________. It is a ___________ system because it has a ____________ component (BP, Temp, etc.)
homeostasis. sensory motor system. monitoring component
3 major divisons of ANS
sympathetic system, parasympathetic system, enteric system
What sympathetic system does (think about stress)
Fight or flight : Increased heart beat, sweaty palms, fast breathing, dilated pupils
What parasympathetic system does
Rest and digest : Contractions of gut, slow breathing/heart rate
Symp. and parasymp. when each works
Both are always active and work in contrast. Balance of both allows ANS to regulate internal milieu (homeostasis)
What enteric system is / does
Complex network of neurons that line the digestive tract. Peristaltic contractions.
Something particular about the enteric system (why is not simply an extension of the ANS)
Can operate by itself, independently
2 kinds of peristaltic contractions
1) Mixing contraction
2) Movement contraction
What are mixing contractions in the digestive tract
Intestines getting longer and shorter
What are movement contractions in the digestive tract
Waves that occur all the way down through the digestive tract -> move the content down
how symp./parasymp. and enteric systems linked together + consequence
Sympathetic and parasympathetic send inputs to the enteric system so they do not directly interact with the intestine
