TAMU BIOL 319 Lab 7

Frequency

The number of occurrences of a repeating event per unit of time.

Amplitude

the height of the wave from baseline to crest

Waveform

shape and form of a signal

Wavelength

the length from the crest of one peak to the crest of the next peak

What is the percentage of skeletal muscle that makes up the cell mass of the body?

40%

Upper motor neuron lesions

loss of muscle function as a consequence of strokes damaging neurons in the brain

Muscle fibers

muscle cells; organized into fascicles

Skeletal muscle is controlled

voluntary

Excitability

ability to receive and respond to stimuli

Contractility

ability to shorten when stimulated

Extensibility

ability to be stretched

Elasticity

ability to be stretched and recoil to the resting cell length

Tendons

connective tissues that attaches muscle to bone

mostly collagen, rope-like extensions

Direct attachment

epimysium fused to periosteum of bone or perichondrium of cartilage

Indirect attachment

muscle attachment in which the epimysium form a tendon that merges into the periosteum

more durable, smaller, common

Ex: aponeurosis (sheet-like)

2 or more muscles usually work

Antagonistically

Sarcolemma

plasma membrane of a muscle fiber

Sarcoplasm

cytoplasm

Myoglobin

stores oxygen in muscle cells

Glycosomes

granules of stored glycogen that can be broken down to supply ATP from glucose for energy

Myofibrils

repeating units of sarcomeres

Takes up most of the intracellular volume of skeletal muscle cells

Sarcomeres

smallest "atomic" contractile units of skeletal muscle fibers

runs from Z line to Z line

runs from each half I band to half I band with an A band in the middle

A band

dark band

I band

light band

H zone (band)

each A band has a middle region that is slightly light

Z line (disc)

dark midline of the I band

Thick filaments

composed of myosin; run the length of the A band

Thin filaments

helix of 2 actin subunit strands; tropomyosin and troponin

Troponin

composed of 3 globular polypeptides each with a different function

One binds to actin, another binds to tropomyosin, calcium ions binds to the third

Titin

what elastic filaments are made of

runs from the Z line to the thick filaments to hold them in place and provide flexible recoil to the sarcomere as it contracts, relaxes, and stretches.

Once titin reaches its normal extension, it stiffens and resists further over-stretching of the muscle

sarcoplasmic reticulum

Controls, stores, releases calcium to controlmuscle fiber contraction

T tubules

At the A and I band junction

elongated tubular extensions of the sarcolemma dive deeply into the cell

Triad

T tubule + terminal cisterns

Polarization

inside of cell is more negative compared to outside

Depolarization

less negative

Repolarization

membrane becomes more negative

potassium exits the cell down its concentration gradient

Refractory period

during repolarization, the cell cannot be stimulated again until the membrane is sufficiently negative