Muscular System

Muscular system

is a system of the human body that provides motor power for all movements of the body.

myocytes, or muscle fibers.

Muscular system is composed of specialized cells called

Muscles

are body tissues that provide the force for all body movements.

700

639

There are more than ____ muscles in the body, with ____ known muscles with names.

Movement of the body

Maintenance of posture

Respiration

Production of body heat

Communication

Constriction of organs and vessels

Contraction of the heart

Functions of Muscular System

Skeletal muscles

Constitutes approximately 40% of the body weight. Attached to the skeletal system

voluntary and striated

Skeletal muscles are

involuntary, not striated

Smooth muscles are

Striated, involuntary

Cardiac muscles are

Cardiac Muscle

Located only in the heart

Smooth Muscle

Can be found on visceral hollow organs like the stomach, trachea, and urinary bladder

CONTRACTILITY

Ability of muscle to shorten forcefully or contract.

EXCITABILITY

Ability of muscle to respond to stimulus

EXTENSIBILITY

Muscles can be stretched beyond its normal resting length and still be able to contract

ELASTICITY

Ability of muscles to recoil to its original resting length after it has been stretched

Tendon

attachments between muscle and bone matrix

Epimysium

connective tissue surrounding entire muscle

Perimysium

connective tissue around muscle fascicles

Endomysium

connective tissue around muscle cells

Fascicles

Subdivides each muscle to numerous visible bundles of muscle fibers

muscle fiber (cell)

separates individual muscle fibers within each Fascicles

Tendon

the protein fibers of the three layers merge at the ends of most muscles to from ____

tendon

muscle

fascicle

muscle fiber

endomysium

perimysium

epimysium

cell membrane

Unique cells with several nuclei just under the

Alternating light and dark bands

gives the striated or stripped appearance

electrical component and mechanical component

main aspect to muscle contraction is

Sarcolemma

cell membrane of the muscle fibers

Transverse Tubules or T tubules

tubelike fold of the sarcolemma.

Transverse Tubules or T tubules

carry electrical impulses into the center of muscle fiber so that the muscle fiber contracts as a whole

Sarcoplasmic Reticulum

a highly specialized ER that stores high level of Ca2

T Tubules

1

Sarcolemma

2

Thin Filament

3

Thick Filament

4

triad

5

Sarcoplasmic Reticulum

6

Terminal Cisterna

7

Myofibrils

threadlike structures that extend the entire length of the muscle fiber.

actin and myosin

2 types of myofilaments

sarcomeres

They are arranged into highly ordered units called

Myofilaments

are the contractile proteins in the myofibers that are arranged into groups that cause the cytoplasm to appear repetitively banded (or striated

Terminal Cisterna

expanded form of t tubules

sarcomeres

functional unit of the skeletal muscles

ACTIN MYOFILAMENT

It is the relationship among the troponin and Tropomyosin that determines when the skeletal muscle will contract

tropomyosin

troponin

actin

attachment site

MYOSIN MYOFILAMEN

Composed of many elongated myosin molecules shaped like a golf clubs.

Myosin molecules

consist of rod portion and two myosin heads

myosin heads

binds to the active sites of actin molecules to form cross bridges to contract the muscles

myosin heads

Head binds to the rod portion by a hinge region that bends and straightens during contraction

myosin heads

Breaks down ATP

SARCOMERES

Smallest portion of muscle that can contract

actin myofilament

myosin myofilament

precise boundary.

Each sarcomere has a

Z disk to the next Z disk

Each sarcomere extends from

A BAND

Darker region ; contains both actin and myosin myofilament overlapping center except in the center

H ZONE

Contains only myosin myofilament

M LINE

hold myosin filaments in place

Z DISK

Forms a stationary anchor for actin myofilaments

I BAND

Lighter region; contains only actin myofilament

slide past one another and shorten the sarcomere.

When muscle fiber contracts the actin and myosin myofilaments in a sarcomere

SARCOMERE

The ends of actin are pulled to and overlap at the center of the

RELAXED SARCOMERE

VISIBLE

_____ The actin and myosin myofilaments overlaps slightly, and the H zone is ____

CONTRACTED SARCOMERE

ACTIN

SARCOMERE

NO LONGER VISIBLE

_____ The A band which is the same length of myosin filament does not change. The ends of____ are pulled to and overlap at the center of the _____. The H zone is ______

EXCITABILITY OF MUSCLE FIBER

Action potentials travel from brain to spinal cord to along the axons to muscle fibers and cause them to contract.

muscle fiber

is in contact with a branch of a motor neuron axon from the brain or spinal cord

acetylcholine

The primary stimulus for this action potential is the release of ______ from the motor neuron

YES

Do muscles have electrical Properties?

ION CHANNELS

contribute to the electrical properties of both resting cell and stimulated cell

Leak

Specific for a particular ions

RESTING CELLS

in ______the leak ion channels allow for the slow leak of ions down their concentration gradient.

GATED

Most important in stimulated cell, and it governs the production of action potential

RESTING MEMBRANE POTENTIAL

The charge difference in unstimulated/relaxed cells. (NEGATIVE)

(1)higher concentration of K+ inside; (2)Higher concentration of Na+ outside; (3)the cell membrane is more permeable to K+ than to Na

RESTING MEMBRANE 3 FACTORS

ACTION POTENTIAL

The charge difference of stimulated/ excitable cell. (POSITIVE)

STIMULATED

IN ACTION POTENTIAL This charge reversal occurs because ion channels open when a cell is

Acetylcholinesterase

Muscles stop contracting When motor neuron end release the enzyme _______ that rapidly breakdown Acetylcholine in the synaptic cleft to choline and acetic acid.

ISOMETRIC CONTRACTIONS

Muscle do not shorten

ISOMETRIC CONTRACTIONS

increases tension in the muscle, but the length of the muscle stays the same

ISOTONIC CONTRACTIONS

Muscles shorten

ISOTONIC CONTRACTIONS

decreases the length of the muscle.

Concentric

Results in increase in tension as the muscles shortens

Eccentric

Tension is maintained in a muscle but opposing resistance is great enough to cause muscle to increase in length

circular

fascicles arranged in a circle around an opening

circular

act as sphincters to close the opening

convergent

broadly distributed fascicles converge at a singe tendon

parallel

fascicles lie parallel to one another and to the long axis of the muscle

pennate

fascicles originate from a tendon that runs the length of the entire muscle

unipennate

fascicles on only one side of the tendon

bipennate

fascicles on both sides of the tendon

multipennate

fascicles arranged at many places around the central tendon