By: Kendra Iverson & Sarah Bender

Muscle- fibrous tissue with the ability to contract, producing movement in or maintaining the position of an animal body System- organized arrangement; network …. Set of connected fibrous tissue that work together to produce movement

Provide muscle tone Propel body fluids and food Generate the heartbeat Distribute heat throughout the body

Skeletal muscle Moves majority of the body Smooth muscle Helps most with digestive system Cardiac muscle Controls the heartbeat

Location: all skeletal muscles- attach to bones Function: movement of bones at joints and maintaining posture Voluntary Contracts and relaxes quickly Transverse tubule system is well-developed

Composed of: skeletal muscle tissue nervous tissue blood connective tissue

Fascia- layers of fibrous connective tissue covers and separates each muscle surface Epimysium- lies beneath the fascia Perimysium- surrounds individual bundles of fibers (fascicles) Endomysium- connective tissue layer that separates individual muscle fibers

Cells that contract in response to stimulation and then relax after the stimulation ends Thin and elongated cylinders with rounded ends Can extend full length of a muscle

Sarcolemma- muscle fiber membrane ↓ Sarcoplasm- cytoplasm ↓ Myofibrils- protein filaments which lie parallel and play great role in contraction Types: Myosin- thicker, called A bands (dark) Actin- thinner, called I bands (light) ↓ Sarcomere- space from center of one I band to the next I band

Sarcoplasmic Reticulum- network of membranous channels that surround each myofibril and run parellel Transverse Tubules (T tubules)- network of membranous channels between sarcoplasm that open outside Both- activate muscle contraction mechanism when the fiber is stimulated

Site where the motor neuron and muscle fiber meet Muscle fiber is specialized to form a motor end plate End branches, has many mitochondria and contains synaptic vesicles that store chemicals Neurotransmitter stimulates muscle fibers to release acetylcholine Travels down a motor neuron axon and stimulates muscle fiber contraction

Includes one motor neuron and several muscle fibers The motor neuron transmits an impulse, which allows all the linked muscle fibers to contract at the same time

Sarcomeres shorten and the muscle is pulled against its attachments Sliding Filament Model Myosin cross-bridge attaches to the binding site on the actin filament and bends, causing a pull on the actin filament Myosin releases and attaches to the next binding site on the actin, causing a pull ATP converts to ADP Repeats this cycle as long as the energy source ATP is available and the muscle fiber is stimulated to contract

Stimulated by acetylcholine (neurotransmitter) Motor neuron releases acetylcholine into the synaptic cleft to initiate contraction Motor end plate has protein receptors which detect acetylcholine Muscle impulse travels over sarcolemma surface and into T tubules, reaching the sarcoplasmic reticulum

Stored calcium ions in the sarcoplasmic reticulum get released into the sarcoplasm Troponin and tropomyosin (proteins associated with actin) move to expose the myosin binding sites on the actin filaments due to the concentration of calcium Muscle shortens because myosin binds and pulls on actin After received- acetylcholinesterase breaks down acetylcholine, calcium returns to sarcoplasmic reticulum, and myosin and actin links break

ATP molecules provides the energy Must be regenerated because it has a limited supply Creatine phosphate Energy can be transferred to ADP molecules, converting them back ATP molecules as ATP is decomposing

Cellular respiration makes a few ATP molecules in early phases Muscles require oxygen Glucose in broken down completely in mitochondria Blood carries oxygen, bound to the pigment hemoglobin The pigment myoglobin stores the oxygen in muscle tissue

The amount of oxygen that liver cells need to convert lactic acid into glucose, and the amount muscle cells must have to recreate the original concentration of ATP and creatine phosphate Develops during strenuous activity Pyruvic acid builds up during anaerobic respiration and diffuses out of muscle cells into the liver May take hours to repay

When a muscle can no longer contract Usually from a build up of lactic acid in the muscle, which lowers pH and results in muscle fibers to not respond to stimulation Cramps- a muscle has a sustained involuntary contraction

More than half of energy released in cellular respiration becomes heat All active cells generate heat, but muscle cells make up a large majority of a bodies total mass Blood moves heat from muscle to other tissues, maintaining body temperature

Location: walls of hollow internal organs, blood vessels Function: to move food through the digestive system and constrict blood vessels Involuntary Contracts and relaxes slowly Rhythmic No transverse tubules

Major types: Multiunit: muscle fibers are separate Usually contract in response to stimulation by certain hormones or motor nerve impulses Visceral: organized in sheets Are found in walls of hollow organs Can stimulate others, displaying rhythmically Responsible for involuntary wavelike motion called peristalsis

Reactions of actin and myosin Triggered by membrane impulses and increased intracellular calcium ions Uses energy from ATP Neurotransmitters are acetylcholine and norepinephrine Affected by hormones Fibers can change length without changing tension

Location: wall of the heart ONLY Function: pumping action of the heart Involuntary Network of cells contract as a unit Rhythmic Transverse tubule system is well-developed Intercalated discs separating adjacent cells

Intercalated discs communicate a muscle impulse throughout entire heart Allows the hearts muscle fibers to beat as a single unit Network responds in an all-or-none manner

Threshold Stimulus- the minimal strength required to cause a contraction Muscle fibers remain unresponsive until reached

All-or-None Response- if a muscle fiber contracts at all, it contracts fully There is no partial contraction Once threshold stimulus is reached, fiber responds to fullest contraction

Recording a Muscle Contraction: Myogram- the pattern resulting from a movement when connected to a device Twitch- a single contraction that lasts only a fraction of a second Latent period- the delay between the time of stimulation and the time the fiber responds

(a) Series of twitches (b) Summation (c) Tetanic Contraction

Summation- when the stimulus of the next series arrives before the muscle fiber can completely relax Tetanic Contraction- when a forceful, sustained contraction lacks any relaxation

Recruitment of Motor Units: Recruitment- the number of motor units activated as a result of a higher intensity of stimulation The addiction of muscle fibers to take part in a contraction

Sustained Contractions: Produced by summation and recruitment together Increasing strength Muscle tone- fibers undergo some sustained contraction even when muscles appear to be relaxed Keeps posture maintained

Muscular hypertrophy: muscles enlarging in size and strength due to forceful exercise Muscular atrophy: muscles decreasing in size and strength due to lack of exercise Size is relative to strength Capillary networks, actin and myosin filaments, and number of mitochondria

Slow twitch fibers: lower intensity and able to resist fatigue, but may not increase muscle size Running or swimming Fast twitch fibers: higher intensity and increase muscle size, but are fatigable Lifting weights

Variety of movements Movement depends on: The kind of joint How the muscle attaches

Origin: the immovable end of a muscle Insertion: the movable end of a muscle The insertion is pulled towards the origin when contraction occurs Flexion and extension tell about the angle between bones that meet at a joint

Almost always function in groups Must will movement to occur and nervous system allows correct muscles to stimulate Prime Mover/Agonist: muscle responsible for a particular movement Synergist: muscles that contract and assist the prime mover Antagonists: muscles that resist the action of the prime mover

Tendinitis- a tendon (attaches muscle to bone) becomes inflamed and swollen after injury or repeated stress during activity Muscle strain- connective tissues are overstretched and the degree of damage and seriousness varies

Botulinum toxin- blocks stimulation of muscle fibers, paralyzing muscles “Botox” to temporarily smooth wrinkles by not allowing to move facial muscles Steroids- (+) increase muscular strength and used for medical purposes, (-) cause changes of opposite sex and damage internal organs

Muscular Dystrophies Missing proteins Muscles weaken and degenerate Charcot-Marie-Tooth Disease A duplicate gene Weakens hands and feet, and tendon reflexes Myotonic Dystrophy An extending gene Muscle weakness and irregular heartbeats Hereditary Idiopathic Dilated Cardiomyopathy A glitch Rare form of heart failure in actin

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