Human Anatomy and Physiology Chapters 10/11

Epimysium

Surrounds whole skeletal muscle, dense irreg tissue

Functions of body muscles

Move body, maintain posture, protect/support, regulate eliminations, produce heat

Perimysium

Surrounds each fascicle

Endomysium

areolar connective tissue, surrounds each muscle cell or fiber

Excitability

ability for a cell to respond to a stimulus

Conductivity

Ability to propogate an action potential down the sarcolemma

Contractibility

slide past one another, cause body movement

Extensibility

Stretch or lengthen

Elasticity

ability for a cell to return to its normal length

Tendon

connects muscle to bone

Aponeurosis

flattened tendo, absorb energy

Sarcolemma

Plasma membrane of muscle cell - contains Sodium and Potassium voltage gated channels

T-tubules

deep invaginations of sarcolemma - contains voltage gated channels of sodium and potassium

What does the sarcoplasmic reticulum do?

stores calcium ions required for contractions

What channels/pumps are present in the membrane of sarcoplasmic reticulum?

Calcium release channels

What voltage gated channel is found in the end-plate?

Sodium release channels

Thick filament

Contains myosin, has globular head and elongated tail, the head is the binding site for actin of thin filaments and ATPase site where ATP attaches

Thin Filaments

2 intertwined strands of actin, has myosin binding site

What does a sarcomere contain?

I Band, A Band, H Zone, M line

What happens to a sarcomere during contraction?

Shortens (Z discs slide closer together)

What causes the release of acetylcholine?

Action potential reaches the end of the neuron and triggers the opening of voltage gate calcium channels

What happens when acetylcholine binds to the acetylcholine receptors?

When it binds, it changes the receptor’s structure

Skeletal Muscle Resting Membrane Potential

-90 mV, more sodium inside the cell, more potassium outside the cell

End Plate Potential (EPP)

minimum threshold in the motor end plate that can trigger the opening of sodium and potassium channels in sarcolemma which initiates an action potential

At action potential,

sodium rushes in, and potassium rushes out of the cell

Depolarization

opening of voltage-gated Na channels, moves in to change charge to 30mV to -90mV

Repolarization

Opening of K voltage-gated channels (30 to -90mV)

How is the action potential propagated?

Electrical signal is propagated along sarcolemma with sequential opening of channels

How is Ca released from the sarcoplasmic reticulum?

T-tubes changes shape which stimulate Ca release channels of the SR to open into cytosol of muscle fiber

Crossbridge

Connection between myosin head and actin filament during muscle contraction

What does calcium bind to and how does it affect the thin filament and crossbridge formation?

Ca binds to troponin in thin filaments, The troponin changes shape and entire troponin-tropomyosin complex is moved, so that tropomyosin no longer covers the myosin binding site

Crossbridge Formation

myosin heads attach to exposed myosin binding sites of actin in thin filaments, the binding of each myosin head of thick filament results in formation of crossbridge between thick and thin filaments

Power Stroke

Swiveling of myosin head pulls thin filament past the thick filament toward the center of the sarcomere - ADP and P are released and the ATP binding site becomes available again

Release of Myosin Head

ATP then binds to the ATP binding site of a myosin head, which causes the release of the myosin head from the binding site on actin

Resetting of Myosin Head

Myosin ATPase splits ATP into ADP and P, providing the energy to reset the myosin head into crossbridge ready position

Excitation-Contraction Coupling

Excitation at NMJ and contraction

What are the three events of Excitation-Contraction Coupling

Development of end plate potential at motor end plate

Initiation of action potential and propagation of electrical signal

Release of Calcium from sarcoplasmic reticulum

Motor Unit

one motor neuron and all the skeletal muscle fibers it innervates - size determines the degree of control and there is an inverse relationship between the size of motor unit and degree of control (small muscles in eye)

ATP in muscle contraction

ATP is in the mitochondria which is needed for aerobic cellular respiration

Glycogen

Stores fuel for molecules

Creatine Phosphate

supplies ATP anaerobically

Myoglobin

provides additional oxygen to enhance aerobic cellular respiration

Oxygen Debt

Amount of additional oxygen consumed to restore pre-exercise conditions

Why does the body continue to breathe heavily after exercise?

Replace oxygen on myoglobin molecults, replenish ATP through aerobic cell respiration and replace glycogen stores (return body to pre-exercise state)

Slow Oxidative Fibers (SO)

Type 1, contain slow myosin ATPase, slower and less powerful contractions, appear dark red because of large amounts of mitochondria and myoglobin

Fast Oxidative Fibers (FO)

Type IIa, least common, fast myosin ATPase, produce fast, powerful contraction with ATP through aerobic cellular respiration, light red

Fast Glycolytic Fibers (FG)

Type IIx, more prevalent, largest, fast myosin ATPase and provide both power and speed, contract through short bursts bc ATP is provided through glycosis, white fibers bc lack of mitochondria and myoglobin

Latent

Action potential travels down axon, across NMJ, and triggers calcium release from SR to sarcolemma

Contraction

Calcium binds to troponin, myosin binds to action and sarcomere shortens

Relaxation

Calcium is pumped into SR which makes myosin detach from action

Wave Summation

Multiple stimuli in rapid sucession - created progressively stronger contractions, nerve impulse adds more calcium into sarcoplasm (actin to myosin)

Incomplete Tetany

Tension increases and the distance between waves decreases

Tetany

Sustained muscle contraction without relaxation

Resting Muscle Tone (Muscle Tone)

Resting tension in skeletal muscle, establish constant tension of tendon

Isotonic Muscle Contraction

Muscle contraction during which tension exceeds the resistance

Isotonic Concentric Muscle Contraction

Shortening of muscle

Isotonic Eccentric Muscle Contraction

Lengthening of muscle

Isometric Muscle Contractions

Length does not change because tension does not exceed resistance (no movement)

Length-Tension Relationship

Amount of tension a muscle can generate when stimulated is influenced by amount of overlap of thick and thin filaments when muscle begins to contract

Hypertrophy

increase in size of cells in tissue

Hyperplasia

Increase in number of cells in tissue

Body undergoes ______ during exercise

hypertrophy

Skeletal Muscle

Striated, multinucleated, voluntary movement, contractions

Smooth Muscle

Non-striated, uninucleated, involuntary movements, innervation

Origin

Less movable during muscle contraction

Insertion

More movable during muscle contraction

The sternocleidomastoid is attached to the sternum and clavicle at one end, and to the mastoid process at the other end. What is the insertion?

Mastoid Process

Agonist

Prime mover, contracts to produce a particular movement

Antagonist

Opposes agonists

When flexing the arm, the biceps brachii contracts and the triceps brachii relaxes. What is the agonst?

Biceps Brachii

Synergist

Structure, muscle, agent, or process that aids the action of another (most useful at the start of movement), assists by stabilizing agonist

When flexing the elbow joint, what is the synergist to the brachialis?

Biceps brachii