Anatomy and Physiology Test 3

Skeletal Muscle Tissue

long, multinucleated and connected to nerves (innervated)

Cardiac Muscle Tissue

shorter, uni or binucleated, branched, involuntary, connected to each other by gap  junctions

Skeletal Muscle Tissue

long, multinucleated and connected to nerves (innervated)

Cardiac Muscle Tissue

shorter, uni or binucleated, branched, involuntary, connected to each other by gap  junctions

Smooth Muscle Cells

short, spindle-shaped, uninucleated, connected to each other by gap junctions

Myocyte

Muscle Cell

Sarcoplasm

Myocyte’s cytoplasm

Sarcolemma

Myocyte’s plasma membrane

Sarcoplasmic Reticulum

modified endoplasmic reticulum; forms web-like network around myofibrils

Myofibrils

Unique cylindrical organelles found in myocytes; makes up 50-80% of cell’s volume

T-Tubules

Found in skeletal and cardiac muscle; a deep tunnel network made up of sarcolemma; facilitates muscle contraction by allowing rapid transmission of electrical signals and distribution of ions throughout muscle fibers

Terminal Cisternae

enlarged sections of sarcoplasmic reticulum that store and release calcium when action potential travels down T-tubules

Thin Filaments

Multiple actin subunits string together and form two intertwining strands in functional thin filament; Each bead-shaped actin has an active site that binds with myosin heads;

Thick Filaments

made up of bundles of contractile protein, myosin

Elastic Filaments

spindle like fibers made up of titin; stabilizes myofibril’s structure to give muscles elasticity

Myosin

Globular head at each end linked by intertwining tails; myosin heads bind with actin’s active site

Tropomyosin

Twist around actin blocking the active site; when tropomyoisn covers the active site, your muscle is relaxed

Troponin

Holds tropomyosin in place

I Band

Only thin filaments and elastic filaments

Z Disc

In the middle of the I band; composed of structural proteins ; anchor thin filaments and elastic cilaments to each other

Sarcomere

Space between Z discs

A Band

Dark band; where thin and thick filaments are contained

H Zone

Middle of A-Filament where only thick filaments exist

M Line

Dark line in the middle of A band; structural proteins that hold thick filaments in place

Perimysium and epimysium come together at the end of muscle to form what?

tendons that bind muscle to bone

Fascia

Thick connective tissue that binds that encloses skeletal muscles; anchors them to surrounding tissues and holds groups of muscle together

Membrane Potential

gradient of negatively charged cytosol and positively charged outside of cells

Leak Channels

Ion channel that’s always open and continuously allows ions to flow down concentration gradients between cytosol and ECF

Gated Channels

Closed at rest, but open in response to a stimulus

Ligand Gated Channels

open in response to a chemical or ligand binding to a receptor

Voltage Gated Channels

Open in response to changes in voltage across membrane

Mechanically Gated Channels

Open in response to mechanical stimulation (pressure, stretch, vibration, etc.)

Sodium Potassium Pump

For every one ATP hydrolyzed, it pumps 3 sodium ions out a 2 potassium ions in

Action Potential

quick, local temporary change in membrane potential; rapid and dramatic changes of concentration of sodium and potassium

Motor Neuron’s Action Potential Length

2 millisenconds

Skeletal Muscle’s Action Potential Length

5 milliseconds

Resting Membrane Potential

-85 millivolts

Stages of Action Potential

Resting phase, depolarization, repolarization

Resting Potential

Gated channels are closed and sodium and potassium gradietns are maintaned by pumps and leak channels

Depolarization Phase

Sodium channels open in response to depolarizing stimulus; sodium enters the cell down its gradient and further depolarizes the membrane

Repolarization

Sodium channels close, potassium channels open, and potassium flows down its gradient and repolarizes the membrane

Motor Neurons

stimulate skeletal muscles to contract

Synapse

where a single motor neuron communicates with multiple muscle fibers

Axon Terminal

Contains synaptic vesicles filled with neurostrasnmitters

Neurotransmitters

chemicals that trigger changes in a tissue; allows for cell to cell communication

Acetylcholine (ACH)

secreted into synaptic cleft and interacts with receptors; opens gates that allows sodium to flow into muscle cell

Synaptic Cleft

Space between axon terminal and muscle fiber; filled with collagen and gel that anchors the neuron in place

Motor End Plate

specialized structure at neuromuscular junction where a motor neuron connects with a muscle fiber; chemical

Phases of Muscle Contraction

1. Excitation

2. Excitation Contraction Coupling

3. Prep for Contraction

4. Contraction

5. Relaxation

Excitation

acetylcholin is released into synaptic cleft and hits ligand gated channels and gets into sarcolemma

Excitation Contraction Coupling

Resulting action potential goes down sarcolemma to trigger t tubules to release calcium

Prep for Contraction

Calcium binds to troponin which moves tropomyosin away from active sites of actin

Contraction

Actin and myosin bind and mysoin under goes a power stroke; contrinues to contract until nuerotransmitter stops

Relaxation

ACH is no longer present and calcium in sarcoplasm returns to normal

Energy sources for muscle contraction

5 creatine phosphate molecules for 1 ATP (immediate sources); anaaerobic glucose metabolism; aerobic glucose catabolism (Krebs Cycle)