Anatomy and Physiology Dr. Brown Exam 3

Sodium Potassium Pump

moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, regulating ion concentration of both sides of the cell membrane

Voltage-gated ion channel

a channel that responds to changes in the electrical properties of the membrane in which it is embedded

ligand-gated ion channel

opens because a signaling molecule, a ligand, bonds to the extracellular region of the channel

Stimulus gated ion channel

when a neurotransmitter or a sensory stimulus binds to a receptor protein to signal channel opening

Resting membrane potential

when ions are distributed across the membrane, the difference in charge is -70 mV

Polarized

a charged particle with oppositely charged ends

polarized membrane

a charged membrane having a positive outside and a negative inside (unequal charges)

Depolarized

change in a cell membrane potential from rest toward zero

repolarization

return of the membrane potential to its normally negative voltage at the end of the action potential

threshold

membrane voltage at which an action potential is initiated

threshold voltage

-70mv to -55mV

Hyperpolarization

returns membrane volage to the resting value when repolarization continues past the resting membrane potential

action potential

change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers

synapse

narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell

Excitability

ability to undergo neural stimulation

Irritability

ability to respond to a stimulus

Contractility

ability to shorten (contract) forcibly

Extensibility

ability to lengthen (extend)

Endomysium

loose, and well-hydrated connective tissue covering each muscle fiber in a skeletal muscle

Perimysium

connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle

Epimysium

outer layer of connective tissue around a skeletal muscle

Tendon

Connects muscle to bone

Fascicle

bundle of muscle fibers within a skeletal muscle

Origin

end of a skeletal muscle that is attached to another structure (usually a bone) in a fixed position

Insertion

end of a skeletal muscle that is attached to the structure (usually a bone) that is moved when the muscle contracts

Myofiber

skeletal muscle cell

Myofibril

long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres

Myocyte

muscle cell

Sarcomere

longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction

A band

when a sarcomere contracts, it stays the same length

A band

I band

when a sarcomere contracts, it becomes smaller

I band

Z line

when a sarcomere contracts, these move closer together

Z-line

Thick filament

the thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all to way to, the Z-discs

Thick filament

Role of thick filament in sarcomere contraction

pulls on thin filaments to bring z-lines closer together

Thin filament

thin strands of actin and its troponin-tropomyosin complex projecting from the Z-discs toward the center of the sarcomere

Thin filament

Role of thin filament in sarcomere contraction

pulled by the myosin heads to slide past the thick filaments toward the center of the sarcomere.

Sarcolemma

plasma membrane of a skeletal muscle fiber

T-tubule

projection of the sarcolemma into the interior of the cell

Sarcoplasmic reticulum

specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++

Myosin

protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber

Actin

protein that makes up most of the thin myofilaments in a sarcomere muscle fiber

Troponin

regulatory protein that binds to actin, tropomyosin, and calcium

Tropomyosin

regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin

Motor end plate

sarcolemma of muscle fiber at the neuromuscular junction, with receptors for the neurotransmitter acetylcholine

Neuromuscular junction

synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal

Acetylcholine

neurotransmitter that binds at a motor end-plate to trigger depolarization

Cardiac muscle

striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the circulatory system. Is under involuntary control.

Intercalated disks

part of the sarcolemma that connects cardiac tissue, and contains gap junctions and desmosomes

Functional syncitium

The wave of contraction that allows the heart to work as a unit- begins with the pacemaker cells.

Smooth muscle

nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal passageways

Tetany

a symptom that involves involuntary muscle contractions and overly stimulated peripheral nerves

membrane potential is established and maintained

Proteins in the membrane or leakage channels allow Na+ to slowly move into the cell or K+ to slowly move out, and the Na+/K+ pump restores them.

mechanism of action potential generation

starts at -70mV with a Na+ channel opening, and Na+ atoms will flood inside the cell causing the cell to become less negative (depolarization), as membrane potential reaches +30mV, a K+ channel will open allowing K+ to flood out of the cell in a process called repolarization- this pushes the membrane potential below -70mV which will result in a period hyperpolarization.

three connective tissues that coordinate a muscle's activity

endomysium- covers each muscle fiber (cell), perimysium- covers fascicles/bundled groups, epimysium- covers the entire muscle

characteristics of muscle tissue

excitability (irritability), contractility, extensibility

step 1 of the molecular events of contraction

Attachment: myosin head (along with ADP and P molecules) binds with actin on a thin filament (other molecules include tropomyosin, Ca2+, and troponin)

step 2 of the molecular events of contraction

Power stroke: myosin head bends releasing ADP and P molecules

step 3 of the molecular events of contraction

Detachment: ATP enters cycle allowing myosin head to be released from actin

step 4 of the molecular events of contraction

Reactivation: myosin moves itself back to the cocked position utilizing energy from the transfer of ATP to ADP and P

Characteristics of cardiac muscle

tubular-shaped, found only in the heart, striated, involuntary control, less SR, myocytes are connected by intercalated discs, doesn't get fatigued, syncytium

syncytium

cells working together like a single functional cell

Characteristics of skeletal muscle

tubular-shaped, striated, voluntary, more SR, gets fatigued

Characteristics of smooth muscle

spindle-shaped, unstriated, involuntary, overlaps tapering cells, interconnected cells, thick and thin filaments crisscross cell, cell "scrunches" during contraction, doesn't contain sarcomeres

step 1 of sliding filament theory

an electrical impulse travels down a nerve fiber

what does an electrical impulse travel down in the sliding filament theory?

a nerve fiber

step 2 of the sliding filament theory

the nerve impulse reaches the end of the nerve and causes it to release acetylcholine (Ach)

Sliding Filament Theory: when the nerve impulse reaches the end of a nerve, what is released?

acetylcholine (Ach)

step 3 of the sliding filament theory

Ach binds to receptors on the muscle cell membrane and causes the electrical impulse to be transmitted to the muscle cell

Sliding filament theory: what happens when Ach binds to receptors on the muscle cell membrane?

the electrical impulse is transmitted to the muscle cell

step 4 of the sliding filament theory

the electrical impulse inside the muscle cell causes the release of calcium ions from the endoplasmic reticulum

the release of calcium ions from the ER

Sliding filament theory: the electrical impulse inside the cell causes...

step 5 of the sliding filament theory

calcium ions bind to troponin causing it to rotate

sliding filament theory: what do calcium ions bond to? what does this cause?

troponin, causes it to rotate

step 6 of the sliding filament theory

rotation of troponin move tropomyosin off the myosin binding site on actin

sliding filament theory: what does the rotation of troponin move?

tropomyosin off the myosin binding site on actin

step 7 of the sliding filament theory

the myosin head binds the myosin binding domain of actin

sliding filament theory: what does the myosin head bind?

the myosin binding domain of actin

step 8 of the sliding filament theory

myosin bends in two places, releasing ADP and pulling on the thin filament

sliding filament theory: what happens when myosin bends in 2 places?

ADP is released and myosin pulls on the thin filament

step 9 of the sliding filament theory

the Z-lines are pulled closer together and the A-band shrinks

sliding filament theory: what happens when the Z-lines are pulled closer together?

the A-bands shrink

step 10 of the sliding filament theory

the myofibril gets shorter (contracts)

step 1 of the NMJ

Action potential (electrical impulse) travels down nerve fiber

step 2 of the NMJ

Acetylcholine (Ach) is released from end of nerve

step 3 of the NMJ

Ach binds to receptor protein on muscle cell

step 4 of the NMJ

action potential is generated inside muscle cell

step 5 of the NMJ

Ca2+ is released from the sarcoplasmic reticulum

what is the effect of calcium on the thin filament?

when calcium binds to troponin, troponin rotates tropomyosin to reveal myosin binding sites on actin

step 1 of the molecular events of the contraction cycle

attachment

myosin head binds to the binding site on actin

what happens during attachment

step 2 of the molecular events of the contraction cycle

power stroke

Myosin head bends and ADP and phosphate are released.

what happens during the power stroke

step 3 of the molecular events of the contraction cycle

detachment

ATP enters the cycle allowing myosin to detach from actin

what happens during detachment

step 4 of the molecular events of the contraction cycle

reactivation