Chapter 10 Human Anatomy

• Name comes from a Latin word for "little mouse" • The main tissue in the heart and walls of hollow organs • Makes up nearly half the body's mass

• Each muscle is an organ • Consists mostly of muscle tissue • Skeletal muscle also contains -Connective tissue -Blood vessels -Nerves • attaches to bone • voluntary control • multinucleated • striated

• Muscle attachments • Most skeletal muscles run from one bone to another • One bone will move • Insertion • Other bone remains fixed • Origin • by connective tissue • Fleshy attachments - connective tissue fibers are short • Indirect attachments - connective tissue forms a tendon or aponeurosis • Bone markings present where tendons meet bones • Tubercles, trochanters, and crests

• Striations result from internal structure of myofibrils • Myofibrils • Long rods within cytoplasm • Make up 80% of the cytoplasm • Specialized contractile organelle found in muscle tissue • A long row of repeating segments called sarcomeres

• heart • striated • involuntary control

• in walls of hollow organs • blood vessels • digestive tract • nonstriated • involuntary

Flexes forearm

• Functions of muscle tissue • Body movements • Movement of substances within body • blood, lymph, urine, air, food and fluids • Stabilizing body positions • Posture • Producing heat • shivering

shorten and generate force

respond to chemicals

propagate electrical signals over membrane

ability to be stretched

ability to return to original shape after stretch

dense irregular connective tissue covering the muscle fiber bundle

(within muscle) a whispy sheath of connective tissue that surrounds each individual muscle fiber

• contractile proteins • myosin and actin • regulatory proteins • turn contraction on & off • troponin and tropomyosin • structural proteins • provide proper alignment, elasticity and extensibility • titin

• The basic unit of contraction of skeletal muscle • Z disc (Z line) • boundaries of each sarcomere • Thin (actin) filaments • extend from Z disc toward center of sarcomere • Thick (myosin) filaments • in center of sarcomere • overlap inner ends of the thin filaments • contain ATPase enzymes

• A bands • full length of the thick filament • includes inner end of thin filaments • H zone • center part of A band • no thin filaments • M line • in center of H zone • tiny rods that hold thick filaments together • I band • only thin filaments • lies within two adjacent sarcomeres

• Sarcoplasmic reticulum • Specialized smooth ER • Contains calcium ions • released when muscle is stimulated to contract • Calcium ions diffuse through cytoplasm • trigger the sliding filament mechanism

1. Nerve impulse stimulates the release of the neurotransmitter acetylcholine (ACh) into the synaptic cleft. 2.ACh stimulates changes in the sarcolemma that excite the muscle fiber. This stimulus is carried down the T tubules to initiate fiber contraction. 3.Enzymes in the synaptic cleft break down ACh and thus limit its action to a single muscle twitch.

Involuntary contraction • small number of motor units • asynchronous activation • goal is not to produce movement • Maintains • posture • head upright • blood pressure • smooth muscles in walls of blood vessels

1. ATP is hydrolyzed when myosin head is attached 2. ADP and P are bound to myosin head attaches to actin 3. ADP and P release caused head to change position and actin filament to move 4. Binding of ATP causes myosin head to return to resting position

allows electrical impulses to travel along the cells' sarcolemma, leading to contraction

are responsible for shortening muscle cells include actin and myosin are specific types of microfilaments

elasticity

smooth

smooth

cardiac muscle

involuntary

skeletal

skeletal

smooth

a sheet of dense connective tissue.

a fleshy attachment

between myofibrils but in fibers.

holds thick filaments in place, thus maintaining the organization of the A band

specialized contractile organelles found in muscle cells

are each continuous with tendons, so they can work together to produce force

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

Calcium ions bind to troponin and change its shape.

The energy comes from the hydrolysis of ATP.

ATP binds to the myosin head.

Calcium ions are stored in the sarcoplasmic reticulum.

sarcomere

A myosin head bound to actin

the region where calcium ions bind it also stores calcium

Myosin heads of thick filaments attach to thin filaments at both ends of a sarcomere and pull the thin filaments toward the center of the sarcomere.

I band

The lengths of the I bands and the H zone decrease.

the boundaries of two adjacent sarcomeres

the sarcomere is fully contracted

H zone

concentric contraction

thin filaments occur

Acetylcholine is degraded by acetylcholinesterase.

Acetylcholine is released by axon terminals of the motor neuron.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

the opening of ligand-gated cation channels

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

Acetylcholine

a single motor neuron and all muscle fibers it innervates Motor unit = • one somatic motor neuron & • all the skeletal muscle fibers the motor neuron innervates • approximately 10 cells to 2,000 cells

are clusters of enlarged endings of an axon that may contain neurotransmitters

neuromuscular junction

Fewer muscle fibers per motor unit allows for fine control of muscle action.