Lecture 7: Muscle

T-tubules (transverse tubules)

What branch to surround myofibrils?

intercalated discs of cardiac muscle

What cell-cell attachments are indicated in this slide?

T tubule + 2 terminal cisternae

What composes triad in the sarcoplasmic reticulum?

-actin and myosin present but in different structure -filaments crisscross cell and attach to sarcolemma at "focal densities" {also called "dense bodies"}

What comprised the contractile apparatus in smooth muscle?

allow instantaneous dissemination of membrane depolarization

What does sarcoplasmic reticulum allow which enable response to stimulus to contract?

smooth muscle cells have different functional stages (contracting {green} vs. relaxed{orange})

What is this image an indication of?

Single centrally located nucleus

What kind of nucleus does cardiac muscle have?

-cardiac muscle fibers -short (individual) cells -striations are present (with A bands, I band, H band and Z and M lines) -single nucleus located in the middle of the cell

What muscle is indicated in this image? How do you know?

-skeletal muscle fibers -striations are present (sarcomeres with A bands, I band, H band and Z lines) -nuclei are located at the peripheral sides

What muscle is indicated in this image? How do you know?

-individual "smooth muscle cells" -spindle shaped nucleus; located in middle of the cell -NO striations (NO myofibrils) -multi-unit

What muscle is indicated in this slide? How do you know?

-individual "smooth muscle cells" -spindle shaped nucleus; located in middle of the cell -NO striations (NO myofibrils) -unitary muscle (bundle cells working together)

What muscle is indicated in this slide? How do you know?

cardiac muscle and smooth muscle

What muscle(s) are involuntary?

smooth muscle

What muscle(s) are non-striated?

skeletal muscle and cardiac muscle

What muscle(s) are striated?

skeletal muscle

What muscle(s) are voluntary?

Hematoxylin and eosin stain

What stain is used in this slide?

-silver stain -reticular fibers

What stain is used in this slide? What is this an indication of?

Hematoxylin and eosin stain

What stain is used on this slide?

Weigerts stain

What stain is used on this slide?

-Acetylcholine released into synaptic cleft from synaptic vesicles (located in nerve end piece) -Sarcolemma depolarization (Na influx) initiates calcium release around myofibrils -acetylcholinesterase --> breakdown of acetylcholine

What steps are involved in the motor end plate of voluntary muscle?

external lamina

analogous to a basement membrane

Sarcomere

area, or portion, of myofibril between 2 adjacent Z-lines

Sarcomere

basic functional unit of contraction

voluntary muscle

can be controlled by conscious thought and require an intact nerve supply to perform a function

Acetylcholinesterase

causes breakdown of acetylcholine

Sarcolemma

cell membrane of a muscle fiber

Sarcoplasm

cytoplasm of a muscle fiber

Endomysium

delicate layer of connective tissue (collagen) around each muscle fiber (cell)

striated muscle

derived from the appearance of a repeating register of bands (or striations) that transversely cross the muscle cell

terminal cisternae

dilated segments adjacent to T tubule

Sarcosome

mitochondria of muscle fiber

muscle fascicle(s)

small groups of cells found in skeletal muscle

motor unit

1 motor nerve and the myofibers it innervates

-Troponin -open binding sites on actin filaments {allows myosin binding to actin}

In smooth muscle, binding of calcium to _________________ changes conformation of tropomyosin to open what?

-round -nucleus has "w" shape

In smooth muscle, the cell becomes ____________ when contracts; nucleus becomes what shape?

endothelial cells

In smooth muscle, the small black or dark purple dots along the luminal surface of both blood vessel are the nuclei of flat cells called ____________________ that cover the surface of all blood vessels.

external lamina

In smooth muscle, what is known to attach cells together?

external lamina or basement membrane (basal lamina)

In smooth muscle, what is located around the sarcolemma (cell membrane)?

coordinated manner

The two tension monitoring structures {tendon organs and muscle spindles} in skeletal muscle work in a _____________________________________.

1. Motor unit 2. Motor end plate

What are the TWO components of direct nerve supply?

1. Striated muscle 2. Non-striated muscle

What are the TWO classifications of muscle based on their morphology?

atrophy

Denervation or inadequate demands require of a skeletal muscle results in decreased size of the muscle called what?

troponin T, I and C

A troponin complex typically consists of what THREE different subunits?

heals by fibrosis {deposition of connective tissue}

Because there are NO satellite cells present in cardiac muscle, how does cardiac muscle heal?

-shorter -one -center -branch

Cardiac muscle cells are ________________ than skeletal muscle cells and contain _______ nucleus with blunt ends that is located in the __________ of the cell. Also, unlike skeletal muscle, cardiac muscle cells can ______________.

-short, branched cells -striated (A, I, H and M bands, Z line)

Cardiac muscle is ____________, ________________ cells that are ___________________________.

involuntary

Cardiac muscle is an ______________________ muscle meaning that it is automatic (independent/without conscious thought) contraction of muscle.

-dystrophin -external lamina -endomysium -endomysium

Contraction is transferred from sarcomere to tendon. First actin filaments are attached to protein called ___________________. Complex of several glycoproteins links dystrophin to ________________________. External lamina is attached to ____________________________. _________________________ transfers force of contraction to tendon.

tropomyosin and troponin complex

Control and contraction of smooth muscle is mediated by ____________________________ and ________________ ______________________.

Myoglobin

Cytoplasm of the muscle cell also contains __________________ which is a protein responsible for the transport of oxygen.

always the same

During a relaxed state or during contraction the width of the A band is _________________.

-actin filaments are attached to protein called dystrophin -complex of several glycoproteins links dystrophin to external lamina (adhesive coat on outside of cell) -external lamina is attached to endomysium -endomysium transfers force of contraction to tendon

How is a contraction transferred from sarcomere to tendon?

-Z line moves closer together -results in the I band and the H band becoming smaller and may disappear until the muscle relaxes at which time the I and H bands increase in length

During contraction, Z lines move ____________________ which results in what?

the structural framework ("stroma" composed of connective tissue)

For muscle tissue to capitalize on its contractile ability to perform work, muscle cells must be attached to what of an organ?

-red fibers -"slow twitch" contractile behavior and oxidative metabolism

Generally, skeletal muscles as organs are associated with maintenance of posture have a high proportion of __________________________; which are categorized by ______________________________________________.

by the protein dystrophin

How are actin filaments anchored to the sarcolemma?

by specialized membrane modifications called intercalated disc

How are cardiac muscle cells attached to one another?

by the external lamina on their surface and delicate reticular fibers within the external lamina

How do smooth muscle cells adhere to one another?

remain the same length

How do the A band and M band change during contraction?

become smaller or disappear

How do the I band and H band change during contraction?

by the presence of individual erythrocytes (red blood cells) or rows of erythrocytes

How will you identify capillaries in cardiac muscle?

deposition of collagen and adipose tissue

In addition to satellite cells in skeletal muscle, deposition of what is commonly associated with the repair process?

Purkinje fibers

In cardiac muscle, the endocardium contains scatter islands of large faintly stained (acidophilic) modified cardia muscle cells called what?

-gap junctions -produces synchronized contractions

In cardiac muscle, these allow communication between cells? What does this produce?

large diameter and located at Z line

In cardiac muscle, what are T tubules like/where are they located?

desmosomes and adherens junctions

In cardiac muscle, what are located at the top of projections and bottom of pits (irregular topography)?

gap junctions

In cardiac muscle, what are located on the sides of projections (irregular topography)?

striated or non-striated

In consideration of its microscopic morphology, muscle tissue is classified as either ____________ or _________________.

satellite cells

In response to injury of skeletal muscle, an inactive pool of stem cells called ______________________________________ (located between the sarcolemma and external lamina) can be stimulated to divide and can be incorporated into muscle cells thus assisting with repair of damage.

inhibit

In response to tension, tendon organs _______________ the action of motor neurons to reduce the tension on a tendon.

syncytium

In skeletal muscle, "muscle fiber" is a true ________________ meaning many nuclei/cells.

nuclei located at periphery of cell

In skeletal muscle, multinucleated cells are present meaning what?

-terminal cisternae -troponin

In skeletal muscle, sarcoplasmic reticulum has calcium released from ________________________. Calcium binds with ___________________ to open binding sites on actin for myosin.

-"all or none law" -when stimulated an entire muscle fiber (cell) contracts

In skeletal muscle, voluntary muscle has the "_____________________ law" which means what?

provide regenerative potential for damaged muscle fibers

In skeletal muscle, what do satellite cells provide?

intercalated discs

Individual cardiac muscle cells are united end to end by an attachment site called _____________ form long chains.

many myoblasts

Muscle fibers {cells} are formed by the fusion of ___________________________.

mesodermal origin

Muscle is primarily of what origin?

-white fibers -"fast twitch" contractile properties and glycolytic metabolism

Muscles capable of short bursts of great power contain abundant ____________________ which have _________________________________________________________.

-thin (f-actin) filaments formed from G-actin molecules {anchored together by a-actinin at Z-line (or Z-disc)} -thick filaments (myosin) interdigitate between the thin filaments

Myofibrils are composed of what?

-smaller -contributes to the red color of gross muscle tissue -important factor in the physiological classification

Myoglobin is ______________ then hemoglobin. Myoglobin contributes to what of gross muscle tissue, and it an important factor in what?

-linear region (light meromysin) -head (heavy meromysin)

Myosin molecules of thick filaments contain a _________________________________ and ___________________ --> parallel, staggered alignment.

1. Contractility (cells change shape during contraction) 2. Irritability (cells are able to respond to a stimulus) 3. Conductivity (cells are able to transmit a wave of excitation)

Regarding muscle, what THREE properties of protoplasm are amplified?

1 or more myofibers

Regarding voluntary muscle {in skeletal muscle}, direct nerve supply is when 1 nerve may supply how many myofibers?

ATP

Rigor mortis occurs after depletion of ____________; therefore unable to prevent binding of myosin to actin.

1. Unitary smooth muscle 2. Multi-unit smooth muscle

Since smooth muscle may or may not be direct innervation of smooth muscle cells, what are the TWO categories of separation?

-endomysium -perimysium -epimysuium

Skeletal muscle cells are unified by a hierarchy of connective tissue coverings (_____________________ around individual myocytes, __________________ around a group of myocytes, ______________ around a muscle belly) that ultimately transfer the contract force to the tendon.

hypertrophy

Skeletal muscle cells enlarge, called ___________________, in response to increased loading or work.

1. Red fibers (type 1) 2. White fibers (type 2) 3. Intermediate fibers

Skeletal muscle cells have been classified based on its physiological and metabolic properties into what THREE categories?

syncytium

Skeletal muscle is a true ______________ that is formed by the fusion of many cells into one cell.

hypertrophy, hyperplasia or atrophy

Smooth muscle can undergo _____________________, ________________________, or _______________ in response to mechanical demands placed on them.

1. Collagen fibers 2. Elastin 3. GAGs 4. Proteoglycans

Smooth muscle cells can secrete components of extracellular matrix such as what FOUR things?

hyperplasia

Smooth muscle cells retain the ability of cell division and thus can increase in number called _______________, in response to increased physiological and mechanical demands placed on smooth muscle tissue.

-NO striations -spindle shaped cell (tapered ends) -1 nucleus {cigar-shaped}

Smooth muscle has _______________________________. How is smooth muscle shaped? Describe the nucleus.

involuntary

Smooth muscle is known as _____________________ muscle; meaning it is automatic (independent/without conscious thought) contraction of muscle.

contraction

Smooth muscle nuclei can appear to be "wrinkled" and frequently have the appearance of a "W", this morphology of the nucleus is typically of a smooth muscle cell during what?

-invaginations -2 sets -carry membrane depolarization into myofibrils

T-tubules are __________________________ in sarcolemma (____ sets per sarcomere). What do they carry into the myofibrils?

-stimulates -increase

Tension on muscle spindles _______________ the actions of motor neurons to contract muscle cells and __________________ tension in the muscle.

neuromuscular junction

The _____________________ corresponds to the muscle fiber and nerve end piece.

-myofilaments {actin and myosin} -sarcomeres -myofibrils

The bands observed in striated muscle result from a specific alignment of ____________________________ into contractile units called ____________________ which compose _________________.

endomysium (connective tissue layer)

The cells indicated by the blue arrows are surrounded by what?

perimysium (connective tissue layer)

The group of muscle fibers indicated within the yellow dotted line is surrounded by what?

-tendon organs -muscle spindles

The normal tone and tension (a measure of magnitude of contraction) of a skeletal muscle as an organ are continually monitored by encapsulated nerve endings in tendons, called what? And by spiral afferent sensory nerve fibers associated with specialized skeletal muscle fibers in what?

Calcium

The sarcoplasmic reticulum is storage sites for what?

-peripheral sided -myofibrils -composed of myofilaments

The skeletal muscle fibers indicated by the blue arrows have a nucleus that is ___________________. The many pink granules are an indication of __________________, composed of _____________________________.

endomysium (connective tissue layer)

The structures outlined in orange are surrounded by what?

True

True/False: Cardiac muscle cells can NOT divide.

True

True/False: Cardiac muscle has abundant mitochondria {large and MORE than in skeletal muscle}.

True

True/False: Involuntary muscle can function with OUT an intact nerve supply (thus an autonomous control mechanism).

True

True/False: Once formed, adult skeletal muscle fibers can NOT undergo cell division.

True

True/False: Regarding voluntary muscle {in skeletal muscle}, individual can direct action (conscious control) of muscle.

Sarcomere

Tubules of sarcoplasmic reticulum pass over _________________________ to connect terminal cisternae.

-microfilaments (actin) -thick filaments (myosin) -mitochondria --> sarcomeres -endoplasmic reticulum --> sarcoplasmic reticulum -cell membrane --> sarcolemma {external lamina and T-tubules}

What are examples of amplification or specialization of organelles of muscles cells?

1. A band 2. I band 3. M band 4. H band

What are the FOUR different regimented alignment of myofilaments responsible for transverse striations?

1. Myofibril 2. T tubules 3. Sarcoplasmic reticulum

What are the THREE main components of the contractile apparatus in skeletal muscle?

1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle

What are the THREE types of muscle based upon their major functions and locations?

1. Voluntary muscle 2. Involuntary muscle

What are the TWO classifications of muscle based on their control of contraction?

their ability to secrete the subcomponents of the tissue (called connective tissue) that surrounds and supports them

What is a unique feature of smooth muscle?

projections and pits (increase surface area)

What is an irregular topography seen in cardiac muscle?

I band

What is indicated by #1?

H band

What is indicated by #2?

A band

What is indicated by #3?

Sarcomere

What is indicated by #4?

Z disk

What is indicated by #5?

skeletal muscle cells

What is indicated by the blue arrows?

myofibrils

What is indicated by the pink granules in this slide?

muscle fascicle

What is indicated within the yellow dotted line?

individual muscle fibers

What is outlined in orange?

-dark band -same length as thick filaments -contains actin and myosin filaments

What is the A band?

-light transverse region in A band -contains only myosin -M band in its center

What is the H band?

-light band -contains only actin filaments

What is the I band?

-dark transverse line in center of A band -site where thick filaments are anchored together -contains only myosin, as well as myosesin

What is the M band?

long, spindle-shaped cell with lightly acidophilic (pink) cytoplasm; single nucleus elongated and looks like a "cigar" with rounded ends and contains primarily euchromatin

What is the appearance of a smooth muscle cell?

-ATP bound to head of myosin {sarcomere relaxed} -ATP hydrolyzed to ADP and phosphate {myosin head binds loosely to actin at binding site} -Phosphate released and myosin head binds tightly to actin {release of energy induces a conformational change in myosin to occur} -ADP released and actin filament is pulled toward M band {center of sarcomere} -ATP attaches to head of myosin which causes release of myosin from actin **Then, process repeated (rapid and sequential)**

What is the process of contraction (shortening) of sarcomere in smooth muscle?

located at level of junction between I and A bands

Where are T-tubules located?

located at junction of I and A bands

Where are terminal cisternae located?

because of the elongated shape of muscle cells

Why is the term "fiber" (thus a muscle fiber or myofiber) frequently used as a synonym for an individual muscle cell?

intercalated discs

a junction between cardiac muscle cells to create physiological syncytium (many cells acting as one)

Epimysium

a layer of connective tissue that surrounds an entire muscle, thus encircling many fascicles, is called what?

Non-striated muscle

actin and myosin present but NOT aligned to produce visible cytoplasmic transverse bands

striated muscle

alignment of filaments (actin and myosin) produce isotropic and anisotropic transverse bands across muscle cell

external lamina

all muscle cells are coated with an adhesive layer on the outer surface called what?

multi-unit smooth muscle

innervation of each muscle cell with NO gap junctions (i.e., eye)

involuntary muscle

functions automatically and independent of thought

Myofibril

highly order alignment of filaments into cylindrical unit of contraction

intercalated discs

in cardiac muscle, these are known to join cells end to end

reticular fibers

known as ONE major component in basement membrane

non-striated {smooth} muscle

lacks these striations and thus the cytoplasm of the cell has a homogeneous or "smooth" appearance

Tropomyosin

linear protein that winds around actin filament

sarcoplasmic reticulum

smooth endoplasmic reticulum of muscle fibers

sarcoplasmic reticulum

smooth endoplasmic reticulum that surrounds myofibrils

unitary smooth muscle

sparse innervation; works as a syncytium via gap junctions (i.e., gut)

rigor mortis

stiffening of a body following death

Perimysium

surrounding each fascicle is a slightly heavier layer of connective tissue called what?

Endomysium

surrounding each individual muscle cells is a delicate layer of connective tissue supporting tissue) called what?

sarcomere

the portion of a myofibril from one Z line to the next Z line is a basic contractile unit striated muscle called what?

satellite cells

these cells in skeletal muscle are retained along surface of muscle fiber in adult with myoblastic potential