Muscular Study Guide Flashcards
Define myofiber
A muscle cell
Define sarcoplasmic reticulum
The smooth endoplasmic reticulum of a muscle cell
Define sarcoplasm
The cytoplasm of skeletal muscle cells
Define sarcolemma
The cell membrane of a muscle
Define sarcomere
1 contractile unit. Makes up muscle cells
What is excitability?
The ability to receive and respond to a stimulus
What is contractility?
The ability to shorten forcibly
What is extensibility?
The ability to be stretched/ extended
What is elasticity?
The ability to recook to resting length
What are the 4 main functions of the muscular system?
Producing movement, maintaining posture and position, stabilizing joints, and generating heat
What are 4 other functions of the muscular system?
Protect viscera, form valves, dilate pupils, and form the arrector pili
What are the characteristics of skeletal muscle?
Striated, multi-nucleated, and voluntary
What are the characteristics of cardiac muscle?
Striated, branched, uni-nucleated, and involuntary
What are the characteristics of smooth muscle?
Not striated, uni-nucleated, involuntary, and visceral.
What tissue does a muscle have?
Contractile and connective tissues
What does it mean that each muscle is an organ?
It’s served by one nerve and an artery, and one or more veins.
Why is blood supply important to a muscle?
So it can have enough oxygen and nutrients to continue aerobic respiration
What is the A band?
The part of the sarcomere where the myosin is
What is the I band?
In a sarcomere, it’s the space between where it’s only actin
What is the Z line?
The line between two sarcomeres
What’s a motor unit?
A motor neuron and all the fibers it supplies
What’s muscle tension?
The force exerted by contracting muscle
What’s load?
The force opposing muscle contraction
Define isometric
When the load is greater than the tension
Define isotonic
When the tension is greater than the load
What’s the difference between thin and thick filaments?
Thin filaments have actin as their primary protein, whereas thick filaments are composed of myosin protein and have a rodlike tail attached to a flexible hinge
Explain the relationship between actin, troponin, and tropomyosin
Actin is the primary protein of thin filaments. Tropomyosin, which is rope-like, covers up the myosin binding sites when relaxed. Troponin binds to tropomyosin, actin, and calcium.
Describe the steps leading up to the cross bridge cycle/ sliding filament theory
Troponin changes shape and moves tropomyosin to expose the bonding site. Myosin is attracted to the actin and binds to it.
What does acetylcholine do?
During nervous stimulation, acetylcholine (ACH) molecules bind to receptors in order to generate potential on the sarcolema
Describe the sliding filament theory/ cross bridge cycle in detail
ADP and phosphorus that are associated with the myosin head release, bending the head and causing the filament to slide. ATP then binds to the myosin head which releases it from the actin. Finally, ATP turns into ADP and phosphorus, which allows binding to a new site
Calcium released into the sarcomere. Where is it released from and what does it bind to?
Calcium is released from the sarcoplasmic reticulum and binds to troponin
What triggers calcium to be released into the sarcomere?
An electrical signal passes down the motor nerve to a muscle and triggers a depolarization of the sarcolemma, which then triggers calcium to be released
How does the contraction impulse stop?
Acetylcholinesterase
Describe the process of muscular relaxation in detail
The sarcoplasmic reticulum reclaims calcium ions from the cytosine pump. Calcium releases from troponin, and troponin changes shape and returns tropomyosin to ties place covering the myosin binding sites. Myosin releases from the actin and the muscle fiber relaxes.
What’s a muscle twitch?
The response of a motor unit to a single action potential
What would the graph of a single muscle twitch look like?
It would look like a flat line, a bump, then back down to a flat line
What would the graph of a summation muscle twitch look like?
Lots of bumps and dips slowly getting higher and higher
What would the graph of a tetanic muscle twitch look like?
Rapidly goes up and then down
During which period is the sarcomere contracted?
The period of contraction
What are the three ways we can get energy to the muscles to energize ATP?
Creatine phosphate, glycolysis, and aerobic respiration
What happens when a muscle fatigues?
It can’t contract
What’s the usual cause of muscle fatigue?
The buildup of K+ (potassium) in the t-tubules, which halts the release of calcium
What causes oxygen debt?
Anaerobic respiration/ glycolysis, and a general lack of oxygen.
How do we repay oxygen debt?
By getting more oxygen
How are the cardiovascular and respiratory systems involved in oxygen debt?
The blood from the cardiovascular system delivers oxygen from the respiratory system to the muscles
What percentage of muscle activity is lost as heat?
60%
How are muscle responses graded?
Smallest fibers to biggest
How does the frequency of a stimulus affect the force of a muscle contraction?
The more frequent the stimulus the stronger the force. Single twitch < summation < tetanus.
What are the three things that can directly impact the force of a muscle contraction?
The size of the fibers that are stimulated, the number of fibers, and the frequency of the stimulation
How are motor units recruited?
By multiple motor unit summation from smallest to largest. If everything happens in order, the contraction will be smooth.
What happens to a muscle during endurance exercises?
The body creates more capillaries, mitochondria, and myoglobin
What happens to a muscle during resistance training exercises?
The body increases the fiber size, creates more mitochondria, myofilaments, and stores more glycogen
Where is smooth muscle found?
Lining hollow organs
How is smooth muscle organized?
Diffuse junctions/ loosely organized
How do neurons interact with smooth muscle compared to skeletal muscle?
Things happen a lot more slowly with smooth muscle
What things is smooth muscle missing that skeletal muscle has?
Smooth muscle lacks tissue sheaths, doesn’t have t-tubules, and doesn’t have any striations
What cells set the rhythm that allows smooth muscle to contract as a unit?
Pacemaker cells
What’s the difference in the energy benefits of smooth muscle over skeletal muscle? What are the cons to this?
Contracting and relaxing smooth muscle takes a lot less energy because it happens 30 times slower
What is the Russian doll scenario?
The idea that parts of a muscle layer on top of each other
What are the layers of the muscle?
Muscle > fascicle > fiber > (myo)fibril > filament/sarcomere
What are the connective tissues of the muscle? Describe them.
The outermost connective tissue is the epimysium. Tendons are found throughout. The perimysium surrounds the fascicle, and the endomysium is located inside the fascicles surrounding the fibers
What are the connective tissues of the muscle in order from outermost to innermost?
Epimysium > tendons > perimysium > endomysium
