Muscle Physiology TEST 4

Interactions of skeletal muscles in the body

Muscles work together or in opposition to achieve a variety of movements

For every muscle, there is an opposing muscle doing the opposite

Muscles PULL not push

Origin

Immovable point of attachment

Insertion

Movable point of attachment

Deltoid Muscle

Origin - Clavicle & Acromion process and spine of scapula

Pectoralis Major Muscle

Origin - Sternal end of clavicle, sternum, ribs 1-6

Insertion - Intertubercular groove on humerus

Biceps Brachii Muscle

Origin - Coracoid process on scapula, Supraglenoid tubercle

Insertion- Radial tuberosity

4 Functional groups of muscles

Prime mover

Antagonist

Synergists

Fixator

Prime mover (agonist)

Leader, major muscle

Ex: Biceps

Antagonist

Opposing prime mover

Ex: Triceps

Synergists

Help prime mover

More force or stabilizes joint

Fixator

Stabilize bones like scapula, posture

We name the muscles based on their…

Location, shape, and size

Brevis

Short

Rectus

Straight

Transverse

90 degrees

Oblique

45 Degrees

Location of attachments

Origin first in name, insertion second

Ex: Sternocleidomastoid

Actions

Flex, extend, adbuct, adduct, etc

Muscle functions

Contractility

Posture

Stabilizing Joints

Heat

Excitability

Elasticity

Muscle cells are organized in…

Circles that get smaller and smaller

Muscle

Organ, 4 different tissues

Fascicles

Bundle of muscle cells

Muscle Cell

Equal to muscle fiber

Myofibril

Subunit of a muscle cell

Microfilaments

Myofilaments = Protein filaments - protein molecules

Tendon

Muscle to bone

Connective Epimysium

Muscle covering

Connective Perimysium

Fascicle covering

Connective Endomysium

Muscle cell covering

Myosin

Thick protein filament

Head attaches to actin

Pivots as muscle contracts

Actin

Thin protein filament

G action - Globular

Main part of the molecule

Tropomyosin

Blocks actins active site or attachment site

Troponin

Binding site for calcium

(Where the ice cream fits into)

Crossbridge

Place where actin (active site) and myosin (head) attach

Sarcomere

One contractile unit

One section of myofibril

Located from z line to z line

4 Regions (A band, I band, H zone, Z line)

A band

Length of myosin, dark band

Length stays the same when contracting

I band

Space between myosin, light band

Gets shorter when contracting

H zone

Space between actin, myosin only

Gets shorter when contracting

Z line

End of sarcomere, anchors actin

Sarcoplasm

Muscle cytoplasm

Sarcolemma

Muscle cell membrane

Sarcoplasmic reticulum (S.R.)

Stores calcium

Terminal cisternae

Enlarged ends of S.R. , stores calcium (calcium closet)

T-Tubules

Sarcolemma that extend deep into myofibril

Triad

2 Terminal cisternae and T-Tubule

Mitochondria

Makes ATP

Nucleus

Cells large and many per cell

Nerve Cell

Electricity (action potentials) travel down the nerve cell (1)

Synaptic cleft

Space between the nerve and muscle cell where a chemical (neurotransmitter) is released by the nerve cell to tell the muscle cell to contract (2)

Sarcolemma

The AP travels along sarcolemma down into T-Tubules (3)

Terminal cisternae

AP causes terminal cisternae to release calcium to sarcoplasm (4)

Calcium

Binds to troponin on actin (ice cream cone) (5)

Troponin

Moves tropomyosin so it’s not blocking active site on actin (6)

Cross bridges formed

Myosin heads attach to actin (7)

Power stroke

Myosin head binds and pivots pulling Z-lines closer (8)

Detach

ATP needed to break head of myosin (relaxes)

crossbridge detachment (9)

Ratchet action

Resetting myosin head, ATP (energy) returns head to original position (10)

Repeat

Repeat steps 7-10 over and over again (cross bridge, reset, repeat) (11)

Z lines

Z lines get closes together

I and H disapear (12)

Action potential

Action potential from nerve cell stop, actin potential from muscle cells stops (13)

(Low to High)

Calcium pump

Active transport mechanism returns Calcium to the terminal cisternae (14)

Tropomyosin

Blocks active site on actin and no more cross bridges can occur (15)

ATP

Breaks cross bridge for the last time and the muscle relaxes (16)

Motor Unit

1 Nerve and all muscle fibers it attaches to

Muscle twitch

Single brief stimulus

Summation

combined twitches

Tetanus

Constant stimulus over a period of time

Whole

The ___ muscle cell contracts. Not a part of the cell

Recruitment

Summation of motor units

Threshold stimulus

Minimal stimulus needed to start muscle contraction

Myogram

Muscle length

Latent period

After stimulation, leading up to contraction

Period of contraction

Crossbridges activate

Period of relaxation

Initiated by calcium, uptake back into S.R

We never ____ muscle cells

Loose or gain

Hypertrophy

Enlargement of a muscle due to exercise/work

Atrophy

Withering f a muscle due to lack of exercise or work

Muscle fatigue

Inability to contract (energy, nerve, muscle)

Rigor mortis

Happens after death. Stiffening of the body due to lack of ATP to break bonds

Fast twitch muscle fibers

Smaller fibers used to high force, short duration activities

Make ATP anaerobically (like push up)

Slow twitch muscle fibers

Bigger fibers used for low force, long duration activities

They posses more endurance enzymes (marathon)

Isometric contraction

Increase tension, muscle length stays same

Isotonic contraction

Increase tension, muscle length chances

Concentric

Muscle shortens

Eccentric

Muscle lengthens (most exercises and all sports)