Muscular System (copy)

Skeletal, Cardiac and Smooth

Types of Muscles

Skeletal and Cardiac

striated

Cardiac Muscles

Contraction is autorhythmic (establishes its own heartbeat)

Intercalated Disks

Cardiac muscle cells are connected to one another by desmosomes and gap junctions called______

Skeletal Muscle

voluntary contractions

Cardiac and Smooth Muscle

involuntary contractions

movement, maintain posture, respiration, production of body heat, communication, constriction of organs and vessels and contraction of heart

Functions of the Muscular System (MMRPCCC)

40%

skeletal muscles contains ____ of body weight

Muscle Fiber

aka muscle cell

Muscle, Fascicle, Myofibril, Myofilaments

Organization of the Skeletal Muscle

Epimysium, Perimysium and Endomysium

3 Layers of the Connective Tissue Coverings

Epimysium

surrounds each skeletal muscle

Fascicle

subdivides each skeletal muscles into groups of muscle fibers

Perimysium

covers each fascicle

Perimysium

Serves as passageways for blood vessels and nerve fibers that supply each fascicle.

Endomysium

layer that separates the individual muscle fiber within each fascicle.

Endomysium

Passageways for nerve and blood vessels that supply each separate muscle fiber.

Muscle Fiber

a single cylindrical cell, with several nuclei located at its periphery.

Sarcolemma, T tubules and Sarcoplasmic Reticulum

3 Muscle Fiber components that respond to and transmit electrical signals to:

Sarcolemma

(cell membrane of muscle fibers) has many tubelike inward folds, called transverse tubules, or T tubules.

T tubules

tubelike inward folds that extend into the muscle fiber and it carries electrical impulses into the center of the muscle fiber

Sarcoplasmic Reticulum

highly specialized smooth endoplasmic reticulum in the skeletal muscle that stores high levels of Ca ions.

Sacroplasmic Reticulum

t tubules are associated with enlarged portions of the smooth endoplasmic reticulum called the ______

Terminal Cisternae

t tubules lie next to enlarged portions of the sacrcoplasmic reticulum called the ______

Triad

2 terminal cisternae and one t tubule form a critical structure for muscle contraction called the _____

Sacroplasm

cytoplasm of a muscle fiber is called the _______ which contains many bundle of protein filaments

Myofibrils

Bundles of protein (myo) filaments

Actin and Myocin

Myofibrils consists of two myofilaments called _____

Sarcomeres

actin and myosin are arranged in a repeating units called the _____

Myofilaments in the sarcomeres

provides the mechanical aspect of muscle contraction

Sarcomere

Basic structural and functional unit of a skeletal muscle

Z disks

networks of protein fibers that serve as an anchor for actin myofilaments and separate one sarcomere from the next.

Sarcomeres or the organization of actin and myosin myofilaments

What gives skeletal muscle its straited appearance and the ability to contract?

I bands

two lighter staining regions that contain only actin myofilaments

A band

central darker staining region which contains both the actin and myosin myofilaments overlapping

H band

contains only myosin myofilaments

M line

consists of delicate protein filaments that hold the myosin filaments in place.

Actin, Troponin and Tropomyosin

Actin myofilaments are made up of three components:

Troponin

these molecules have binding sites for Ca ions

Tropomyosin

these filaments block the myosin myofilament binding sites on the actin myofilaments

Myosin heads

_____ have binding sites for ATP

Motor Neuron

nerve cell that stimulates muscle cells.

Synapse

a cell to cell junction between a nerve cell and either another nerve cell or an effector cell such as in a muscle or organ

Neuromuscular Junction

a synapse where a neuron connects with a muscle fiber

Motor Unit

a group of muscle fibers that a single motor neuron stimulates

Presynaptic Terminal

end of a neuron cell axon fiber

Synaptic Cleft

the space between the presynaptic terminal and the postsynaptic membrane

Postsynaptic membrane

muscle fiber membrane (sarcolema)

Synaptic Vesicle

a vesicle in the presynaptic terminal that stores and releases neurotransmitter chemicals

Neurotransmitters

chemicals that stimulate or inhibit postsynaptic cellss

Acetylcholine

neurotransmitter that stimulates skeletal muscles

Polarized

Electrically excitable cells are ____

Negatively

the inside of the cell membrane is _____ charged than the outside

Resting Membrane Potential

The electrical charge difference across the cell membrane of an unstimulated cell is called the _______

Leak Channels

In resting or unstimulated cells, _______ allow for the slow leak of ions down the concentration gradient.

Gated Channels

In stimulated cells, this governs the production of action potentials.

Gated Channels

Action potentials are due to the membrane having

higher

In the resting membrane potential, the concentration of K ion inside the cell membrane is ____ than that outside.

higher

In the resting membrane potential, the concentration of Na ion outside the cell membrane is ____ than that inside

Action Potential

occurs when the excitible cell is stimulated

Depolarization and Repolarization

two phases of Action Potential

Depolarization Phase

inside of the cell becomes more positively charged (Na goes intracellularlly)

Threshold

membrane potential at which gated Na channels open

Repolarization Phase

return of the membrane potential to its resting value. Also occurs when Na gated channels close and K gated channels open.

Acetylcholine

these are released from the synaptic vesicles then diffuses across the cleft and bind to ligand gated Na channels in the sarcolemma causing them to open.

Acetylcholesterase

breaks downs acetylcholine into acetic acid and choline

Cross-bridge cycling

mechanical component of muscle contraction is called ____

Power Stroke

movement of teh myosin head

Recovery Stroke

myosin head return to resting position; from high energy to low energy

Muscle Twitch

single contraction of a muscle fiber in response to a stimulus

Lag (Latent), Contraction and Relaxation Phase

a muscle twitch has three phases:

Lag or Latent Phase

time between the application of a stimulus and the beginning of contraction

Contraction Phase

time during contraction

Relaxation Phase

time during which the muscle relaxes

Potassium and Sodium

What is the most common intracellular ion?

reverses the resting membrane potential

What does an action potential do so that the inside of the cell becomes positive and the outside negative?

threshold

If the depolarization changes the membrane potential to a value called blank an action potential is triggered.

An action potential

a rapid change in charge across the cell membrane.

sarcolemma

The action potential travels across the

Repolarization

“the positive charge causes gated Na+ channels to close and gated K+ channels to open” where does this occur?

Cell membrane

Opening of gated K+ channels starts repolarization of the

Repolarization

is due to the exit of K+ from the cell

Muscle contraction

In a muscle fiber, an action potential results in

Depolarization

change in charges inside becomes more + and outside more – Na+ channels open

Repolarization

Na+ channels close change back to resting potential

Twitch

refers to the contraction of a single muscle fiber, a motor unit, or a whole muscle.

Latent Phase

Time during which the neuron potential is traveling along the axon; events at the neuromuscular junction occur and the action potential travels along the sarcolemma

Contraction Phase

Commences once Ca2+ is released from the sarcoplasmic reticulum and cross-bridge cycling occurs

Relaxation phase

Longer than the contraction phase; concentration of Ca2+ in the sarcoplasm decreases slowly due to active transport into the sarcoplasmic reticulum

Action Potential

• electrochemical event

• Measured in volts; completed in less than 2 milliseconds

Contraction

• mechanical event

• measured as force, called tension; reported as number of grams lifted or distance the muscle shortens; requires 1 second to occur

Tension

reported as number of grams lifted or distance the muscle shortens; requires 1 second to occur. measured as force called

Isomeric and Isotonic

Two types of muscle contraction

Isometric

increase in muscle tension, no change in length

Isometric

Lift an object that is too heavy; muscles do not shorten due to bones not moving

Isotonic

increase in muscle tension, decreases the length

Isotonic

Lift an object and move it; muscles shorten thanks to movement of limb

Summation and Recruitment

The strength of muscle contraction strength depends on two factors:

Summation

The amount of force in an individual muscle fiber is called