SET 10 - Harris Lash PDF

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Harris Lash...

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SET 10 muscle • 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

skeletal muscle • 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

basic feature of skeletal muscle • 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

striated

myofibrils and sarcromeres • 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

Cardiac muscle • heart • striated • involuntary control

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

nonstriated

Brachialis Flexes forearm

muscle tissue • 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

Contractility shorten and generate force

excitability respond to chemicals

conductivity propagate electrical signals over membrane

extensibility ability to be stretched

elasticity ability to return to original shape after stretch

fascicle

fiber

myofibril

epmysium

permysium dense irregular connective tissue covering the muscle fiber bundle

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

the proteins of muscle • contractile proteins • myosin and actin • regulatory proteins • turn contraction on & off • troponin and tropomyosin

• structural proteins • provide proper alignment, elasticity and extensibility • titin

sarcomere • 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

sarcomere structure • 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 and T tubules • 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

the neuromuscular junction 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.

muscle tone 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

mechanism of contraction 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

Excitability is the special functional feature of muscle tissue that __________. allows electrical impulses to travel along the cells' sarcolemma, leading to contraction

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

The property of skeletal muscle function that allows recoil after being stretched is ______. elasticity

This type of muscle makes up the walls of hollow organs, such as the stomach and uterus. smooth

This type of muscle is found in large vessels leading to and from the heart. smooth

A cell of this type of muscle is striated and can be uninucleated or binucleated. cardiac muscle

cardiac and smooth muscle are? involuntary

This type of muscle attaches to bone, but may also attach to skin, cartilage, fascia or a raphe. skeletal

The biceps and the deltoid muscle are of this type. skeletal

Which type of muscle fiber has no myofibrils? smooth

aponeurosis a sheet of dense connective tissue.

The type of attachment in which the muscle fibers seem to attach directly to a bone is a fleshy attachment

Sarcoplasmic reticulum lies between myofibrils but in fibers.

Titin is a protein that __________. holds thick filaments in place, thus maintaining the organization of the A band

myofibrils specialized contractile organelles found in muscle cells

Endomysium, perimysium, and epimysium __________. are each continuous with tendons, so they can work together to produce force

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

What specific event triggers the uncovering of the myosin binding site on actin? Calcium ions bind to troponin and change its shape.

How does the myosin head obtain the energy required for activation? The energy comes from the hydrolysis of ATP.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? ATP binds to the myosin head.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? Calcium ions are stored in the sarcoplasmic reticulum.

What structure is the functional unit of contraction in a skeletal muscle fiber? sarcomere

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? A myosin head bound to actin

In a sarcomere, the thin filaments are __________. the region where calcium ions bind it also stores calcium

How does the sliding filament mechanism result in concentric contraction of skeletal muscle? 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.

The region of thin filaments only that is part of two adjacent sarcomeres is the __________.

I band

During contraction, which of the following occurs in a sarcomere? The lengths of the I bands and the H zone decrease.

Z discs (Z lines) are ______. the boundaries of two adjacent sarcomeres

If you could not see the H zone in a photomicrograph of a sarcomere in skeletal muscle, ______. the sarcomere is fully contracted

The area that contains no thin filaments is known as the H zone

When the distance between two adjacent Z disks grows shorter, the muscle fiber is experiencing concentric contraction

In striated muscle, the I band is where thin filaments occur

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction? Acetylcholine is released by axon terminals of the motor neuron.

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Calcium entry into the axon terminal triggers which of the following events? Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Acetylcholine binds to its receptor in the sarcolemma and triggers __________. the opening of ligand-gated cation channels

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

__________ is the neurotransmitter that signals a single contraction of a muscle cell. Acetylcholine

motor unit 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

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

The point at which a nerve ending and skeletal fiber meet is called a(n) ______. neuromuscular junction

Why are there fewer muscle fibers per motor unit in the fingers than in the muscles of the thighs? Fewer muscle fibers per motor unit allows for fine control of muscle action....