A&P Slideshow Chapter 9

_____ make up nearly half of body’s mass.

• muscles

Muscles make up nearly _____ of body’s mass.

• half

Muscle tissue can transform _____ energy into _____ energy, which is capable of exerting force.

• chemical energy (ATP)

• directed mechanical energy

What are 3 prefixes for muscle?

• myo-

• mys-

• sarco-

What are the 3 types of muscle tissue?

• skeletal

• cardiac

• smooth

What are muscle fibers?

• are elongated muscle cells found in skeletal and smooth muscle, but not cardiac

• an elongated multinucleate cell; it has a banded (striated) appearance

• surrounded by endomysium

What is skeletal muscle?

• skeletal muscle tissue is packaged into skeletal muscles: organs that are attached to bones and skin

• skeletal muscle fibers are longest and have striations (stripes)

• also called voluntary muscle: can be consciously controlled

• contract rapidly; tire easily; powerful

• key words for skeletal muscle: skeletal, striated, and voluntary

What are skeletal muscles?

• organs that are attached to bones and skin

Why is skeletal muscle also called voluntary muscle?

• can be consciously controlled

What type of muscle is also called voluntary muscle?

• skeletal muscle

What type of muscle tissue contracts rapidly, tires easily, and is powerful?

• skeletal muscle

What is cardiac muscle?

• is found only in heart

  • makes up bulk of heart walls

• striated

• involuntary: cannot be controlled consciously

  • contracts at steady rate due to heart’s own pacemaker, but nervous system can increase rate

• key words for cardiac muscle: cardiac, striated, and involuntary

Is cardiac muscle voluntary or involuntary? (Why?)

• involuntary because it cannot be controlled consciously

What is smooth muscle?

• found in walls of hollow organs

  • ex: stomach, urinary bladder, and airways

• not striated

• involuntary: cannot be controlled consciously

• key words for smooth muscle: visceral, nonstriated, and involuntary

Where is smooth muscle found?

• found in walls of hollow organs

• ex: stomach, urinary bladder, and airways

Is smooth muscle voluntary or involuntary? (Why?)

• involuntary because it cannot be controlled consciously

All muscles share 4 main characteristics?

• excitability (responsiveness): ability to receive and respond to stimuli

• contractility: ability to shorten forcible when stimulated

• extensibility: ability to be stretched

• elasticity: ability to recoil to resting length

What is muscle excitability?

• (responsiveness) ability to receive and respond to stimuli

What is muscle contractility?

• ability to shorten forcibly when stimulated

What is muscle extensibility?

• ability to be stretched

What is muscle elasticity?

• ability to recoil to resting length

What are 4 important muscle functions?

• produce movement: responsible for all locomotion and manipulation

  • ex: walking, digesting, pumping blood

• maintain posture and body position

• stabilize joints

• generate heat as they contract

Each muscle receives a _____, _____, and _____.

• nerve

• artery

• veins

Consciously controlled skeletal muscle has _____ supplying every fiber to control activity.

• nerves

Contracting muscle fibers require huge amounts of _____ and _____.

• oxygen and nutrients

Each skeletal muscle, as well as each muscle fiber, is covered in _____.

• connective tissue

Name the skeletal muscle sheaths from external to internal.

• epimysium

• perimysium

• endomysium

What is the epimysium?

• dense irregular connective tissue surrounding entire muscle; may blend with fascia

• (skeletal muscle sheath)

What is the perimysium?

• fibrous connective tissue surrounding fascicles (groups of muscle gibers)

• skeletal muscle sheath

What is the endomysium?

• fine areolar connective tissue surrounding each muscle fiber

• skeletal muscle sheath

What are fascicles?

• groups of muscle fibers

• a discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath

• surrounded by perimysium

Muscles span _____ and attach to _____ or other sutures.

• joints

• bones

Attachments can be _____ or _____.

• direct

• indirect

What are direct (fleshy) attachments?

• epimysium fused to periosteum of bone or perichondrium of cartilage

• (e.g., intercostal muscles, abdominal wall)

What are indirect attachments?

• connective tissue wrappings extend beyond muscle

  • ropelike tendon

  • sheetlike aponeuosis

What is a muscle?

• a muscle consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and axons (nerve fibers)

• covered externally by the epimysium

______ muscle fibers are long, cylindrical cells that contain multiple nuclei.

• skeletal

What is the sarcolemma?

• muscle fiber plasma membrane (skeletal muscle fiber)

What is the sarcoplasm?

• muscle fiber cytoplasm

• contains many glycosides for glycogen storage, as well as myoglobin for O2 storage

What are 3 specialized structures within skeletal muscle cells?

• myofibrils

• sarcoplasmic reticulum

• T tubules

What are myofibrils?

• densely packed, rodlike elements

• single muscle fiber can contains 1000s

• accounts for ~80% of muscle cell volume

• rodlike contractile elements that occupy most of the muscle cell volume

  • composed of sarcomeres arranged end to end, they appear banded, and bands of adjacent myofibrils are aligned

What are some features of myofibrils?

• striations

• sarcomeres

• myofilaments

• molecular composition of myofilaments

What are striations?

• stripes formed from repeating series of dark and light bands along length of each myofibril

  • A bands: dark regions

    • H zone: lighter region in middle of dark A band

      • M line: line of protein (myosin) that bisects H zone vertically

  • I bands: lighter regions

    • Z disc (line): coin-shaped of proteins on midline of light I band

What are the A bands and I bands of striations?

• A bands: dark regions

• I bands: lighter regions

What is the H zone of striations?

• lighter region in middle of dark A band

What is the M line of striations?

• line of protein (myosin) that bisects H zone vertically

What is the Z disc of striations?

• (line) coin-shaped sheet of proteins on midline of light I band

What is the sarcomere?

• smallest contractile unit (functional unit) of muscle fiber

• contains A band with half of an I band at each end

  • consists of area between Z discs

• individual sarcomeres align end to end along myofibril, like boxcars of train

• the contractile unit, composed of myofilaments made up of contractile proteins

What are myofilaments?

• orderly arrengement of action and myosin and myofilaments within sarcomere

• actin myofilaments: thin filaments

• myosin myofilaments: thick filaments

• sarcomere cross section shows hexagonal arragnement of one thick filament surrounded by 6 thin filaments

What are actin myofilaments?

• thin filaments

• extend across I band and partway in A band

• anchored to Z discs

What are myosin myofilaments?

• thick filaments

• extend length of A band

• connected at M line

What is the molecular composition of myofilaments?

• thick filaments: composed of protein myosin that contains 2 heavy and 4 light polypeptide chains

• thin filaments: composed of fibrous protein actin

• tropomyosin and troponin: regulatory proteins bound to actin

Heavy chains intertwined to form myosin _____.

• tail

Light chains form myosin globular _____.

• head

During contraction, heads link thick and thin filaments together, forming _____.

• cross bridges

Myosin’s are offset from each other, resulting in _____ of heads at different points along _____ filament.

• staggered array

• thick

_____ is a popylpeptide made up of kidney-shaped G actin (globular) subunits.

• actin

Actin is a polypeptide made up of kidney-shaped _____ subunits.

• G actin

G actin subunits bears active sites for myosin _____ attachment during contraction.

• G actin

_____ bears active sites for myosin head attachment during contraction.

• G actin subunits

G actin subunits link together to form long, fibrous _____.

• F actin (filamentous)

_____ link together to form long, fibrous F actin (filamentous).

• F actin

Two _____ strands twist together to form a thin filament.

• F actin

_____ and _____ are regulatory proteins bound to actin.

• tropomyosin

• troponin

What is elastic filament?

• composed of protein titan

• holds thick filaments in place; helps recoil after stretch; resists excessive stretching

Elastic filaments are composed of protein _____.

• titin

What does dystrophin do?

• links thin filaments to proteins of sarcolemma

What do nebula, myomesin, and C proteins do?

• bind filaments or sarcomeres together

  • maintain alignment of sarcomere

What is the sarcoplasmic reticulum?

• network of smooth endoplasmic reticulum tubules surrounding each myofibril

  • most run longitudinally

  • terminal cisterns form perpendicular cross channels at the A-I band junction

  • SR functions in regulation of intracellular Ca2+ levels

  • stores and releases Ca2+

What are T tubules?

• tube formed by protrusion of sarcolemma deep into cell interior

  • increase muscle fiber’s surface area greatly

  • lumen continuous with extracellular space

  • allow electrical nerve transmissions to reach deep into interior of each muscle fiber

• tubules penetrate cell’s interior at each A-I band junction between terminal cisterns

  • Triad: are formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere

What is a triad in T tubules?

• area formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere

What are triad relationships?

• T tubule contains integral membrane proteins that protrude into inter membrane space (space between tubule and muscle fiber sarcolemma)

• SR cistern membranes also have integral membrane proteins that protrude into inter membrane space

• when an electrical impulse passes by, T tubule proteins change shape, causing SR proteins to change shape, causing release of calcium into cytoplasm

T tubule contains _____ that protrude into inter membrane space (space between tubule and muscle fiber sarcolemma).

• integral membrane proteins

Tubule proteins act as _____ that change shape in response to an electrical current.

• voltage sensors

_____ also have integral membrane proteins that protrude into inter membrane space.

• SR cistern membranes

SR integral proteins control opening of _____ in SR cisterns.

• calcium channels

When an electrical impulse passes by, _____ proteins change shape, causing SR proteins to change shape, causing release of calcium into cytoplasm.

• T tubule

When an electrical impulse passes by, T tubule proteins change shape, causing SR proteins to change shape, causing release of _____ into cytoplasm.

• calcium

What is a contraction?

• the activation of cross bridges to generate force

• shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening

When does contraction end?

• when cross bridges become inactive

In the relaxed state, thin and thick filaments overlap only slightly at ends of _____ band.

• A

What is the sliding filament model of contraction?

• states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more

  • neither thick nor thin filaments change length, just overlap more

When nervous system stimulates muscle fiber, myosin heads are allowed to bind to actin, forming _____, which cause sliding (contraction) process to begin.

• cross bridges

_____ attachments form and break several times, each time pulling thin filaments a little closer toward center of sarcoma in a ratcheting action.

• cross bridge

Cross bridge attachments form and break several times, each time _____.

• pulling thin filaments a little closer toward center of sarcoma in a ratcheting action

The decision to move is activated by the _____.

• brain

The decision to move is activated by the brain; the signal is transmitted down the _____ to _____.

• spinal cord

• motor neurons

The decision to move is activated by the brain; the signal is transmitted down the spinal cord to motor neurons which then activate _____.

• muscle fibers

_____ cells are capable of changing resting membrane potential voltages.

• excitable

AP crosses from neuron to muscle cell via the neurotransmitter _____.

• acetylcholine (ACh)

What are ion channels?

• play the major role in changing of membrane potentials

• 2 classes of ion channels:

  • chemically gated ion channels— opened by chemical messengers such as neuretoransmitters

    • ex: ACh receptors on muscle cells

  • voltage-gated ion channels— open or close in response to voltage changes in membrane potential

What are the 2 class of ion channels?

• chemically gated ion channels

• voltage-gated ion channels

What are chemically gated ion channels?

• opened by chemical messengers such as neurotransmitters

  • example: ACh receptors on muscle cells

What are voltage-gated ion channels?

• open or close in response to voltage changes in membrane potential

Skeletal muscles are stimulated by _____.

• somatic motor neurons

_____ travel from central nervous system to skeletal muscle.

• axons

What are axons?

• long, threadlike extensions of motor neurons

Axon branches end on _____.

• muscle fiber

Axon branches end on muscle fiber, forming _____ or _____.

• neuromuscular junction

• motor end plate

Each muscle fiber has one _____ with one motor neuron.

• neuromuscular junction