unit 3 notecards

Function of muscle tissue

Movement, posture, heat protection

Smooth muscle

Involuntary control, in hallow organs (stomach/intestines), spindle shaped cells, non striated, single nucleus

Cardiac muscle

voluntary control, in the heart, striated, usually single nucleus, intercalated discs facilitate communication

Skeletal muscle

Voluntary control, attached to bones, striated, long cylindrical fibers, multiple nuclei

Whole muscle

Composed of multiple fascicles

Muscle fascicle

Bundle of muscle fibers

Muscle fiber

Individual muscle cell, functional unit

Deep fascia

Connective tissue surrounding muscles; separates muscle groups

Epimysium

Connective tissue that envelopes the entire muscle

Perimysium

Connective tissue surrounding each fascicle

Endomysium

Connective tissue surrounding individual muscle fibers

Tendon

Connects muscle to bone, transmits force

Aponeuroses

Slat sheets of connective tissue that anchor muscles or bones to other muscles

Muscle fiber (cell)

Basic unit of muscle, multi nucleated

Sarcolemma

Plasma membrane of the muscle fiber

Sarcoplasm

Cytoplasm of muscle fiber containing organelles

T-tubules

Extensions of the sarcolemma that enhance conduction of muscle action potential

Nucleus

Contains genetic material, multiple nuclei per muscle fiber

Neuromuscular junction

Synapse between a motor neuron and muscle fiber

Sarcoplasmic reticulum

Specialized, endoplasmic reticulum stores, calcium ions

Terminal cisternae

Enlarge areas of the sarcoplasmic reticulum adjacent to T-tubules

Myofibrils

Long thread, like structures within muscle fibers, consisting of acting in myosin

Myofiliments

Protein filaments involved in muscle contraction

Actin

Send filaments facilitate contraction

Myosin

Thick filaments interact with acting for contractions

sarcomere

The functional unit of muscle contraction

Z disc

Boundary between adjacent sarcomeres

M line

Middle line that bisect the a band

A band

Area containing both thick and thin filaments

I band

Area containing only thin filaments

H zone

Central region of the a band where there is no overlap of filaments

Zone of overlap

Region were actin and myosin filaments overlap

Titin

Elastic protein that stabilizes the position of myosin filaments and contributes to muscle elasticity

Cross bridges

Protrusions from myosin filaments that bind to Actin

Actin-binding sites

Sites on Actin where cross bridges can attach

troponin

Complex that finds calcium and regulates contraction via tropomyosin

Tropomyosin

Obstructs actin binding sites when muscle is relax

ATP-binding sites

Site on myosin where ATP binds and hydrolysis occurs to drive muscle contraction

Sliding filament. Model of contraction.

Describes how muscle fibers contract through the sliding of Acton over myosin sarcomeres, shortened as myosin pulls on Actin towards the M line contraction occurs without changing the length of the filaments

Motor neuron activation

Release of acetylcholine (ACh) at neuromuscular junction

Muscle action potential

ACh Binds to postsynaptic receptors triggering an action potential

T-tubule activation

Action potential travels down T-tubules

Calcium release

Sarcoplasmic, reticulum releases, calcium into the sarcoplasm

Cross bridge formation

Calcium binds to troponin exposing binding sites on Actin

The power stroke

Myosin, heads, pivot, pulling Acton filaments towards the center of the sarcomere

Crossbridge detachment

ATP binds to myosin causing detachment from actin

Cocking of myosin head

ATP hydrolysis repositioned the myosin head for the next cycle

Muscle twitch

A single contraction and relaxation cycle of muscle fiber

Latent period

Time between stimulus and contraction onset

Contraction phase

Muscle shortens as tension increases

Relaxation phase

Muscle tension decreases as calcium is reabsorbed

Threshold stimulus

Minimum stimulus required to fire an action potential in a muscle fiber

All or none principal

Muscle fibers contract fully or not at all when threshold is reached

Motor unit

A motor neuron and all fibers it innervates, regulates force of contraction

recruitment

activation of additional motor units to increase muscle tension

wave summation

increase tension of muscle fibers when stimuli are repeated

incomplete tetanus

no muscle partially relaxes between stimuli

complete tetanus

no relaxation occurs between stimuli, maximum tension

muscle tone

slight tension in resting muscle stabilizes joints

atrophy

decrease in muscle mass due to disuse

hypertrophy

increase in muscle mass due to exercise

Fast glycolytic fibers

Large diameter, high force, fatigue quickly, anaerobic

Fast oxidative fibers

Intermediate diameter, moderate force, resistance to fatigue, aerobic

slow oxidative fibers

Smaller diameter, low force, fatigue resistant, highly aerobic

ATP cycle

Continuous turnover of ATP during muscle contraction and relaxation

Aerobic respiration

Occurs in mitochondria utilizing oxygen to metabolize glucose for ATP

Anaerobic respiration

Occurs outside of mitochondria producing ATP without oxygen results in lactic acid

Glycogen

Stored glucose energy source for muscle contraction

Creatine phosphate

Rapid ATP regeneration during short bursts of activity donates phosphate to ADP

Myoglobin

Oxygen storage molecule within muscle cells, enhances aerobic capacity

Lactic acid

Byproduct of anaerobic respiration can lead to muscle fatigue

Muscle fatigue

Temporary inability to maintain muscle contraction due to various factors, including energy depletion

Isotonic contractions

Muscle changes length while maintaining constant tension

Concentric isotonic contraction

Muscle shortens while producing tension

Eccentric isotonic contraction

Muscle lengthens while producing tension

Isometric contraction

Muscle length remains the same while tension increases no movement occurs

Parallel

Muscle fibers run parallel to each other example biceps brachii

Convergent

Fiber is conferred towards a single tendon example pectoralis major

Pennate

Fibers are arranged at an angle to the tendon example rectus femoris

circular

fibers arranged in concentric rings example orbicularis oris

naming of muscles

Based on shape, size, location, and direction of fibers, number of origins, action

Prime movers (agonists)

Primary muscles for particular movement (biceps brachii in elbow flexion)

Synergists

Assist the prime mover in performing a movement (brachialis aids biceps in flexion)

Fixators

Stabilize joints during movement (rotator cuff muscles stabilize the shoulder)

Antagonists

Muscles that oppose the action of the prime mover (triceps brachii in elbow flexion)