UA PSIO EXAM 3

3 Types of Muscle

Skeletal, Cardiac, Smooth

Basic function of all muscles

Generate tension

Functions of Skeletal Muscle

Locomotion, facial expression, posture and body position, regulation of body temp

Skeletal muscle contraction is voluntary or involuntary?

voluntary

T or F: All skeletal muscles are automatic

False, some are automatic but we can change their ability like the diaphragm

Muscles ____ on bones

pull

Origin

the place where the muscle starts on a bone

Insertion

the place where the muscle ends on a bone

Muscle Action

The insertion moves towards the origin

Flexion

Decreasing the angle between two bones

Extension

Increasing the angle between two bones

Plane where extension and flexion mostly occur:

Sagittal plane

T or F: In standard anatomical position everything is extended

False, the feet arent

Abduction

Moving away from the midline of the body

Adduction

Moving toward the midline of the body

Abduction and Adduction occurs on which plane?

frontal plane

Reverse muscle action (RMA)

when the insertion is anchored, the origin moves towards the insertion

Agonist

muscle primarily responsible for movement

Antagonist

muscle which opposes the action of the agonist

Synergist

assists the agonist in making a movement more efficient

Fixator

special synergists which help to prevent movement at muscle origin

Lever

a rigid bar that is free to move around a fixed point, the rigid bar in this case is bone.

Fulcrum

the fixed point around which a lever can move, in this case a joint

muscles act to facilitate movement at a _____ by exerting force on the ____ to move a load

fulcrum, lever

First Class Levers (LFE)

Opening of the mouth (not very common movement) sorta like a scissor movement

Second Class Levers (FLE)

Lifting up on your toes and concentric movement of the calf kinda like a wheelbarrow

Third Class Levels (FEL)

Most common type of lever system in the body like how tongs work

Structural organization of skeletal muscle (deep - superficial)

muscle fibers, fascicles, muscles, groups of muscles

Muscle fibers

individual muscle cells made of myofibril can span 100 micrometers in diameter covered by endomysium

fascicles

bundles of muscle fibers covered with perimysium

Muscles

bundles of fascicles covered by the epimysium

Muscle fibers cannot undergo ____ after birth

mitosis

Hypertrophy

increase in cell size

Hyperplasia

Increase in cell number

Satellite cells

undergo mitosis after birth for aid in muscle regeneration

Functional units of organization

Conduction, Control, Contraction (CCC)

Conduction of electrical signals

Sarcolemma surrounds cytoplasm, T-tubules arise from sarcolemma

Control of muscle contraction

sarcoplasmic reticulum stores calcium, close proximity to t-tubules, surrounds myofibrils

Contraction

myofibrils, long bundles of protein filaments of actin and myosin organized into units called sarcomeres

Sarcomere

functional unit of muscle contraction

D

Sarcoplasmic Reticulum

(Organelle of the muscle fiber that stores calcium.)

Triad

Contains T-Tubule and Terminal Cisternae

T

Mitochondrion

Myofibril

tightly packed filament bundles found within skeletal muscle fibers

Sarcoplasm

cytoplasm of a muscle cell

Sarcolemma

muscle cell membrane

Purple Blob

Nucleus (Control center of the cell)

Thick Filament

the thick myosin strands

Thin filament

thin strands of actin, troponin, and tropomyosin

Z-Disc

Separates the sarcomeres from each other Z line

E

M-Line (middle)

H-Zone

thick filaments only

Zone of Overlap

where thick and thin filaments overlap

G

(A BAND) dark area; extends length of the thick filaments

1

(I BAND) light area, contains only thin filaments

E

(Titin Filament) Stabilizes the thick protein, span from Z-M

Crossbridge

Myosin heads bind to actin

Sliding Filament model of Muscle Contraction

1. Myosin 'heads' bind to actin to form a 'crossbridge'

2. Conformational change, energized by ATP hydrolysis, causes thin filaments to slide along thick filaments

3. Myosin head groups release, form new crossbridges, and the sliding cycle repeats...

As thick/thin overlap increases?

I band length decreases, A band length remains constant, H zone length decreases, Zone of overlap increases

Muscle Proteins

Contractile, Regulatory, Structural

Contractile proteins

Actin, Myosin

Regulatory Proteins

Troponin, Tropmyosin

Structural Proteins

Titin, dystrophin, myomesin, nebulin, alpha-actinin

Actin

Found in thin filament, has myosin binding sites for crossbridge formation

Myosin

found in thick filaments, has myosin head that binds to the myosin binding sites for crossbridge formation

Thin Filaments

composed of two strands of actin + regulatory proteins

Tropomyosin

Found in thin filaments, covers the myosin binding sites when relaxed

Troponin

found in thin filaments, holds tropomyosin in place when relaxed, calcium binds to troponin to shift tropomyosin away from binding sites to allow crossbridge formation

Thick filament

made of myosin, myosin head has ATPase activity when bound to actin, spans the distance between and overlaps thin filaments

Titin

spans half of each sarcomere from Z disc to M line

stabilizes the position of the thick filament; gives muscle its elasticity and extensibility; and helps the sarcomere return to resting length after contraction

Dystrophin

Cytoskeletal protein that links the thin filament to the sarcolemma, helps transmit tension from sarcomeres to tendons

Nebulin

spans the length of thin filaments, anchors thin filament to z-disc

Alpha-actinin

- found in the Z disc

- binds to actin molecules of the thin filaments and to titin

Myomesin

-found in the M line

-binds to titin and thick filaments to connect them together at the M line

Crossbridge Cycling

begins when myosin binding sites on actin filaments become exposed (Ca 2+ serves as the signaling molecule)

How does the myosin head get ready before a muscle contraction starts?

ATP Binds to the myosin head, ATP changes to ADP and Pi, cocks back like a pistol ready to shoot

Contraction Cycle Step 1

Myosin binding sites on actin become exposed when Ca2+ binds to troponin

Contraction Cycle Step 2

Myosin heads bind to actin forming crossbridges

Contraction Cycle Step 3

myosin heads pivot toward the center of the sarcomere (power stroke)

Contraction Cycle Step 4

As myosin heads bind ATP, the cross bridges detach from actin

Contraction Cycle Step 5

cross-bridge detachment; ATP binds to myosin head; link to actin broken

Contraction Cycle Step 6

the contraction cycle repeats until the myosin binding sites on actin are no longer available

Rigor Complex

the attached head group after the power stroke

Rigor Mortis

the rigor of death that happens due to lack of ATP to detach the crossbridge

T or F: ATP is not needed to detach the crossbridge

FALSE, ATP is needed

Crossbridge Neural Control (SOE)

Excitation, Excitation-Contraction Coupling, Contraction, Relaxation

Excitation (SOE)

electrical signal transmitted from motor neuron to skeletal muscle fiber

Excitation-Contraction Coupling (SOE)

Ca2+ is released from sarcoplasmic reticulum

Contraction (SOE)

Ca2+ binds to troponin on the thin filament, forms crossbridges

Relaxation (SOE)

removal of CA2+

The Electrical Signal

CNS sends an electrical impulse to the Neuromuscular Junction (NMJ) to the muscle fibers

Neuromuscular transmission

transmitting an electrical impulse from the motor neuron to muscle fibers across the NMJ

Neuromuscular Junction

synapse where a motor neuron transmits a signal to a skeletal muscle fiber, causing it to contract

Motor End Plate

specialized region of sarcolemma with receptors that respond to neurotransmitters

Neuromuscular transmission at the NMJ step 1

Action potential arrives at the synaptic end bulb of a motor neuron and causes opening of voltage-gated Ca2+ channels

Neuromuscular transmission at the NMJ step 2

Synaptic vesicles containing acetylcholine (ACh) undergo exocytosis

Neuromuscular transmission at the NMJ step 3

ACh is released into the synaptic cleft and binds to ACh receptors on the motor end plate

Neuromuscular transmission at the NMJ step 4

ACh receptors open and allow Na+ to enter the muscle fiber, generating an action potential on the sarcolemma

Neuromuscular transmission at the NMJ step 5

ACh is quickly broken down to acetate and choline by acetylcholinesterase (AChE)

Release of Ca2+ from the sarcoplasmic reticulum step 1

Action potential runs along sarcolemma and continues into T-Tubules