Flashcards in Physiology of Muscle Contraction Deck (79):
Sarcomeres end to end make up...
Many myofibrils make up the...
A single motor neuron and all of the muscle fibers it supplies
A single nerve cell
A bundle of neurons
Smallest recordable contraction, a response to a single threshold stimulus large enough to create Action Potential
First phase of muscle twitch between the stimulus and initiation of muscle twitch response
Time when excitation is recurring, action potential release of Ca and up to initial binding of myosin head to actin. No tension is generated yet
Phase where power stokes occur, onset of shortening to peak of tension development
Phase where Ca is taken back into terminal cysternae, ATP comes and and causes cross bridges to let go
Does twitch duration vary with muscle fiber type?
Which muscle have a slower twitch? Which ones have a faster?
Posturals have slower twitches
Rapid response muscles have faster twitches
Way to increase tension past the muscle twitch
Graded Muscle Response
This graded muscle response that increases the rate of stimulus delivery
What occurs when there is no relaxation from temporal summation, analagous to a charlie horse
Type of temporal summation that is good for daily activity
Graded muscle response where sequentially more units are recruited as stimulus intensity increases. Results in smooth steady increase in force.
Multiple Motor Unit Summation
Are smaller or larger units recruited first?
Smaller (less fiber associated with single nerve cell)
Graded muscle response of the warm up effect, with repeated stimuli, muscle warms up and enzymes (myosin ATPase, etc) become more efficient and stronger contraction ensues
How does treppe differ from temporal summation?
Treppe has COMPLETE relaxtion between stimuli
This is the force that is generated by cross bridge formation
Force on object
Weight on object
Type of contraction same tension but changing length of muscle
Type of isotonic contraction that shortens the muscle, only type explained by Huxley's theory (sarcomere shortening)
Type of isotonic contraction where the muscle lengthens
Ex: lift heavy weight and place it down on the table. Not explained by Huxley's theory
Contraction where the muscle stays same length but force changes.
Ex: Getting up out of chair and push against wall
Type of contraction that is mechanically induced, performed at same speed with a controlled angular velocity of joint. Doesn't happen in daily life.
Typically on exercise machines
What to type of contractions are performed in daily life?
Isotonic and Isometric contraction
Larger muscle means larger force
The 4 non-contractile elements of muscle cells that are elastic
Connective tissue covering
2 proteins that are non contractile in muscle
Titin and Nebulin
Tension in a muscle that is directed at overcoming non contractile element elasticity
In a twitch, most of stimulus is used as...
This type of tension is done first
Too much overlap gives how much contraction? Not much room to pull.
75%`of resting length
Resting length, sufficient overlap so that when stimulus arrives in sarcoplasm, a good overlap so that crossbridges can form
too little overlap, impossible for crossbridges to form because myosin heads cannot reach the actin. Happens if muscle is
Force that can be generated is related to two things about the contraction. What are they
Velocity and Duration of the Contraction?
Greater load = more or less muscle shortening = shorter or longer contraction
Greater load is slower or faster contraction?
Slower contraction (too heavy can't lift at all, v=0)
Most all human muscle is of mixed
Some cells/fibers that have slow myosin ATPase (takes a while to cleave ATP into ADP and inorganic phostphate during activation phase), have lots of myoglobin, many capillaries and mitochondria, O2 dependent, low glycogen stores
Slow Oxidative Fiber Types
Slow oxidative fiber type is commonly used in what type of exercise
Fast ATPase, less myoglobin, not O2 dependent with high glycogen storage
Fast glycolytic is commonly used for what type of exercise?
Fast ATPase, moderate glycogen stores, little endurance, some dependence on oxygen (in the middle of the other two)
Fast Oxidative Glycolytic
Does the amount of fibers types an individual have depend upon genetics?
Similar to skeletal muscle because it is excitable, stretches, contracts, and moves things. Different in shape and size of cell, lack of striations, and location.
Typically located within walls of different organs
The organization of smooth muscle consists of ____ of muscle cells
2 layers of smooth muscle
Longitudinal and Circular
What is the functional outcome of smooth muscle?
Can squeeze and push material through a tube
Innervation of skeletal muscle is different, every single smooth muscle cell has its own _____ _______ This directs every muscle when and how to contract
Because the smooth muscle is organized in sheets, it is generally supplied by the
Autonomic Nervous System
Is the neuromuscular junction of smooth muscle as tightly organized as skeletal muscle?
What is the neuromuscular junction in smooth muscle called?
What about terminal boutons?
What joins smooth muscle cells together to allow communication between the cells? (Unlike skeletal muscle)
What is the thin layer of connective tissue that surrounds each muscle cell?
This structure in the smooth muscle is less well developed than skeletal muscle and touches the plasma membrane.
Structure that smooth muscle has within plasma membrane that stores Calcium. It is also stored in sarcoplasmic reticulum
Are there T-Tubules in smooth muscle cells? Why?
No. The sarcoplasmic reticulum touches plasma membrane. No need
What is the ratio of thick to thin filaments in smooth muscle? Much greater than skeletal muscle
Thick filaments in smooth muscle are made of
Thin filaments are made of
Actin and Tropomyosin NO troponin
Are the thick and thin filaments arranged in bands like skeletal muscle cell?
No. Hence "smooth"
Where is neurotransmitter (NT) released from in smooth muscle?
This structure receives the NT stimulus directly
Sarcoplasmic Reticulum (SR)
SR stimulus allows what to enter the cytoplasm from the SR and caveoli, allowing contraction to occur.
For APs that are so far from bulbous varicosity that the AP doesn't go through, where does it receive AP from?
Therefore, smooth muscle contracts as a
Unit (or sheet)
Smooth muscle contraction is initiated by this which comes from SR and caveoli after AP goes into bulbous varicosity
Ca going into cytoplasm
Because there is no troponin/tropomyosin complex, Ca binds to what intracellular protein?
What does calmodulin activate, which typically phosphorilate something?
What does kinase transfer phosphate to using ATP?
What happens when ATP is phosphorilated, in other words, given energy to perform a contraction?
Cross bridges form bt myosin head and thin filaments
Type of smooth muscle where cells contract as a unit. It is rhythmical. Gap junctions allow current flow directly. This is typically found in organs
Single Unit (Unitary)
Muscle Fibers that are independent of one another. Rare gap junctions and rare spontaneous action potentials. Respond to hormones and have ANS innervation. Muscle that regulate pupil size, arrector pili, large airways to lungs and larger arteries
What neurotransmitters are important in regulating smooth muscle?
Acetylcholine and norepinephrine
The receptors that receive NT are either...
Results in increased or decreased contraction. Ex: sitting verse running when digesting
Inhibitory or excitatory
Smooth muscle, when stretched, results in more vigorous or less vigorous contraction?
More vigorous (opposite of skeletal muscle)
Hormones and local factors, like NTs, can be either....
Depends on receptor too
Inhibitory or excitatory
Unique feature of smooth muscle that stretch stimulates contraction
Increase in # of muscle (can grow or increase)
Ex: Uterus in pregnancy