Chapter 6 - Muscular system

skeletal

attached to the bone

attached by tendons to bones

cardiac

walls of heart

smooth

walls of hollow organs (not heart

muscles ….. never ……

pull & push

myo/mys

muscle

sacro

flesh

movement of microfilaments

contraction and shortening of muscles

epimysium, perimysium, endomysium

voluntary via nervous system

skeletal (characteristics)

endomysium

involuntary due to internal pace maker

cardiac (characteristics)

endomysium

involuntary nervous system controls

smooth (characteristics)

endomysium

inside

encloses a single muscle fiber

perimysium

between

wraps around fascicle (bundle) of muscle fibers

epimysium

covers entire skeletal muscle

• fascia: on the outside of epimysium

tendons

cordlike structure

aponeuroses

sheetlike structures

• wrist

smooth muscle

• no striations

• involuntary

• mainly in walls of hollow visceral organs (stomach, bladder, respiratory passages)

• NOT IN HEART

cardiac muscle

• striations

• involuntary

• found ONLY in walls of heart

• contracts at a steady rate set by pacemaker

I band

• light band

• thin filaments

• no myosin

• Z disc - mid interruption

A band

• dark band

• has myosin (makes dark)

• entire length thick filaments

• H zone - lighter central area

• M line = center of H zone

sarcomere

contractile unit of a muscle fiber

• structural and functional unit of skeletal muscle

During contraction ?

H zones disappear as actin and myosin filaments overlap

Sacroplasmic reticulum (SR)

• store and releases calcium

• calcium provides the final “go” for contraction

irritability (responsiveness)

ability to receive and respond to a stimulus

contractility

ability to forcibly shorten when an adequate stimulus is received

extensibility

ability of muscles to be stretched

elasticity

ability to recoil and resume resting length after stretching

skeletal muscle must be stimulated by ???? to contract

motor neuron (never cell)

*the skeletal muscle cells stimulated by that neuron

neuromuscular junction

• association site of axon terminal of the motor neuron and sacrolemma of a muscle

neurontransmitter

• chemical related by nerve upon arrival of nerve impulse in the axon terminal

• Acetylcholine (ACh) is the neurotransmitter that stimulates skeletal muscle

synaptic cleft

• gap between nerve (neuron and sarcomere) and muscle filled with interstitial fluid

• nerve and muscle DO NOT TOUCH

Events of Neuromuscular Junction (1)

nerve impulse reaches the axon terminal of the motor neuron

Events of Neuromuscular Junction (2)

calcium channels open and calcium ions enter the axon terminal

Events of Neuromuscular Junction (3)

calcium ion entry comes some synaptic vesicles to release acetylooocholine (ACh)

Events of Neuromuscular Junction (4)

ACh diffuses across the synaptic cleft and attaches to receptors on the sarcolemma of the muscle cell

Events of Neuromuscular Junction (5)

if enough ACh is released, the sarcolemma becomes temporarily more permeable to sodium ions

• more sodium ions enter than potassium ions leave

• entry of sodium ions produces an imbalance in which interior how more positive ions (depolarization) thereby opening more Na+ channels

Events of Neuromuscular Junction (6)

depolarizations opens more sodium channels that allow sodium ions to enter the cell

• action potential is created

• once begun the action potential is unstoppable

• conducts the electrical impulse from one end of the cell to the other

Events of Neuromuscular Junction (7)

acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and choline

• ACHE ends muscle contraction

• a single nerve impulse produces only one contraction

Cell returns to resting state when

• potassium ions (K+) diffuse out of cell

• sodium-potassium pump moves sodium and potassium ions back to original positions

• restores ionic balance

sliding filament theory

• calcium ions bind regulatory proteins on thin filaments and expose myosin binding sites, allowing the myosin heads on thick film to attach

• cross bridge pivots, causing the thin file to slide toward the center of the sarcomere

• contraction occurs and cell shortens

• during contraction, cross bridge attaches and detaches several times

• ATP provides energy for sliding process which continues a long as calcium ions are present

3 ways to generate ATP

1. direct phosphorylation of ADP by creatine phosphate (CP) FASTEST

2. aerobic respiration

3. anaerobic glycolysis and lactic acid formation

direct phosphorylation of ADP by creatine phosphate (CP) FASTEST

• 1 atp is produced

• ADP + CP = ATP

aerobic respiration

• glucose broken down to carbon dioxide and water - releasing energy (about 32 ATP)

• slower delivery of sugar nutrients and carbs

anaerobic glycolysis and lactic acid formation

• makes 2 ATP

• breaks down glucose without oxygen

• lactic acid

oxygen deficit

is repaid by rapid, deep breathing

isotonic contractions

• Same

• slide past each other, muscle shortens, makes movement

isometric

• muscles try, BUT muscles pitted against immovable object

• tension increase, muscle does not shorten

5 rules of skeletal muscle activity

1. exceptions/all skeletal muscles cross at least one joint

2. bulk of skeletal muscles lies proximal to joint crossed

3. all skeletal muscle have 2 attachments - the organ and the insertion

4. CAN ONLY PULL NEVER PUSH

5. during contraction, skeletal muscle insertion moves toward origin I - O

origin

• attachment to an immovable or less movable bone

insertion

• attachment to movable bone

• contraction = insertion - origin

• body movement occurs when muscles contract across joints

flexion

• Decreases the angle of the joint

• Brings two bones closer together

• Typical of bending hinge joints

extension

• Increases the angle between two bones

• Typical of straightening the elbow or knee

•  Extension beyond 180 o is hyperextension
  

rotation

• Movement of a bone around its longitudinal axis

• common in ball-and-socket joints

abduction

away from mid

adduction

toward midline

(adding)

circumduction

combination of flexion, extension, abduction, adductions

• wrap around movement

dorsiflexion

• flexing foot

• toes toward shin

plantar flexion

pointing toes

inversion

turning sole of foot medially

eversion

turning foot laterally

supination

palms up

• holding soup

pronation

palm down

opposition

thumb to finger

• okay sign

• counting finger s

prime mover

• muscle with major responsibility for a movement

antagonist

muscle that opposed or reverse a prime mover

synergist

muscle that aids prime mover in movement or reduces undesirable movements

fixator

specialized synergists that hold a bone still or stabilize the organ of a prime mover