Muscle Tissue (lecture)

What are the 4 characteristics of muscle tissue?

1. Excitability (responds to stimulus)

2. Contractibility

3. Distendability (stretch to limits without damage)

4. Elasticity (stretch + recoil) - titin

Is skeletal tissue voluntary or involuntary?

Voluntary (can be controlled)

What are the 6 functions of skeletal muscle tissue?

1. Produce skeletal movement (only pull, NOT push)(Please)

2. Maintain posture and body position (muscles contract to hold body in place)(Make)

3. Support soft tissues (Snacks)

4. Guard entrances and exits(Gremlins)

5. Maintain body temperature (energy not converted=heat, shivering=rapid contraction)(Might)

6. Store nutrient reserves(Starve)

What are the 4 components of skeletal muscle?

• Muscle tissue (cells or fibers)

• Connective tissues

• Nerves

• Blood vessels

Myo-, Mys-, and Sacro- refer to what?

Muscle

Hypo- means is what?

Below

Hyper- means what?

Above

Epimysium is made up of what, connected to what, and surrounds what?

• Collagen layer

• Deep fascia

• Muscles (to separate from surrounding tissue)

Perimysium surrounds what and contains what?

• Muscle fiber bundles (fascicles)

• Blood vessel and nerve supply to fascicles

A bundle of muscle fibers is what?

A fascicle

Endomysium surrounds what and contains what?

• Individual muscle cells (muscle fibers) - may fuse together

• Capillaries and nerve fibers (contacting muscles cells)

• Myosatellite cells (stem cells) repair damage

Endomysium, perimysium, and epimysium come together to form what?

Tendons or aponeurosis (sheets, flat)

• Connective tissue attachment to bone matrix

Skeletal muscle cells develop through fusion of what cells?

Myoblasts

The cell membrane is known as what?

Sarcolemma

The cytoplasm is known as what?

Sarcoplasm

Transverse tubules (T tubules) are similar to what and perform what?

• Sarcolemma properties

• Transmit surface action potential (electrical charges) through deep cell

Myofibrils can be compared to cigarettes in what way?

• Box holding cigarettes=muscle cell

• Cigarettes=myofibrils, specialized organelle running through muscle fiber

• Tobacco=myofilaments, bundles of protein filaments that make up myofibrils

Thin filaments are made up of what?

Actin

Thick filaments are made up of what?

Myosin

The Sarcoplasmic Reticulum (SR) surrounds what, what is its structure, and what is it attached to?

• Myofibrils

• Web-like

• Chambers (terminal cisterna) attached to T tubules

A triad is a part of what and formed by what?

• Sarcoplasmic Reticulum (SR)

• Formed by T tubule (in middle) and two terminal cisternae (on sides)

What is cisternae apart of and what does it do?

• Triad

• Store/concentrate calcium via ion pumps

• Release calcium into sarcomeres for muscle contraction

What are the dark, thick of myofibrils?

A bands

What are the light, thin filaments of myofibrils?

I bands

Sarcomeres do what in myofibrils?

• Contract (structural)

• Z line to Z line

The A band is the darker or lighter filament?

Darker

What line is found in the center of the A band and midline of sarcomere?

M line

What is the area of no overlap around the M line with thick filaments no thin filaments?

H band

What is the densest, darkest area on a light micrograph where thin and thick filaments come together? This allows for what and what happens to the sarcomere?

• Zone of overlap

• Allows for muscle contraction

• Shortens sarcomere

Z lines are in the center of what bands and where are they in relation to sarcomeres?

• I bands

• AT the ends

Titin are made up of what, function to do what, and are found where?

• Strands of protein

• Between tips of thick filaments and Z line (horizontal)

• Stabilize filaments and provide elasticity to muscle tissue

F-actin is like a pearl necklace in what way?

G-actin is twisted into two rows as the pearls of the necklace, F-actin

The active sites on G-actin bind to what?

Myosin

F-actin is a thick or thin filament?

Thin (needs all the help to stabilize)

What structure holds F-actin together (runs down the middle horizontally)?

Nebulin

Tropomyosin looks like what and prevents what?

• Double twisted strand

• Prevents actin-myosin interactions by covering active/binding sites

Troponin is made up of what kind of protein and binds what to what?

• Globular protein

• Binds tropomyosin to G-actin

Troponin is made up of what 3 structures?

• TnI

• TnT

• TnC

TnI is what?

Inhibitory (last in line)

TnT attached to what?

Attaches troponin to tropomyosin (first in line)

TnC is where what binds?

Calcium (in the middle of line)

How does troponin change shape and allow for muscle contraction?

1. Calcium comes from SR and binds to TnC (changing troponin shape)

2. Causes tropomyosin to pull off from active site and allow for contraction

Thick filaments contain what kind of subunits?

Myosin

What does the tail of myosin do?

Bind to other myosin molecules

The head of a myosin molecules is made up of what?

Two globular protein subunits, actin binding site, ATP binding site, and ATPase (breakdown ATP for energy)

What is the function of dystrophin?

• Links actin in outermost myofilament to transmembrane proteins and eventually to fibrous endomysium (surrounding entire muscle cell)

• Transfers force of muscle contraction to connective tissue around muscle cell

• Genetic defects produce diseases, muscular dystrophy

In the sliding filament theory, what zone stays the same, decreases, and what line moves closer?

• A zone stays the same

• I band and H zone decrease

• Z lines move closer together

What is the synapse?

Point where nerve fiber meets its target cell (sometimes a muscle fiber, neuromuscular junction)

The swollen end of nerve fiber containing synaptic vesicles filled with acetylcholine (ACh)

Synaptic knob

Tiny gab between synaptic knob and sarcolemma

Synaptic cleft

This cell envelops and isolates NMJ from surrounding tissue fluid

Schwann

They undergo exocytosis releasing ACh into synaptic cleft

Synaptic vesicles

A lack of ACh receptors in the muscle cell plasma membrane leads to what?

Paralysis in disease myasthenia gravis