Learning Targets Chapter 9 (Muscles)

**4 Functions of skeletal muscles**

* Movement
* Posture
* Stabilize 
* Body heat

Epimysium

surrounds entire muscle (keeps shape)

Tendon

connects muscle to bone

Perimysium

wraps muscle fibers into fascicles 

Endomysium

surrounds each muscle fiber

Fascicle

 bundle of muscle fibers

Fiber

muscle cell

Myofibril

contractile organelles, makes up 80% of fiber, contains sarcomeres

Sarcomere

multiple units of myofilaments, contractile unit of actin and myosin 

Actin

thin protein filament

Myosin

thick protein filament 

Myofilament

one unit of actin/myosin filaments

Z-line

connects each myofilament

Order of muscle fiber parts from largest to smallest

1\. muscle fibers

2\. myofibrils

3\. sarcomeres

4\. myofilaments 

Myoglobin

is the protein used to store oxygen in the muscle

Glycosomes

storage unit of glycogen (glucose)

T-tubules

an extension of the sarcoplasmic reticulum, continue to carry the electrical signal, allow communication so all sarcomeres contract at the same time

Sarcoplasmic Reticulum

 help to carry the electrical impulse into the muscle, stores calcium

Neuromuscular Junction

where one nerve ending and one muscle fiber meet

Sodium

the sodium enters the muscle fiber and results in depolarization (loss of resting membrane potential)

Calcium

 binds to troponin to allow myosin to connect to actin

1st step of muscle contraction

The neurotransmitter releases ach into the synaptic cleft

2nd step of muscle contraction

Ach binds to receptors on sarcolemma an creates action potential

3rd step of muscle contraction

Action potential travel to the t-tubules

4th step of muscle contraction

Electrical signal causes sarcoplasmic reticulum to release calcium

5th step of muscle contraction

Calcium binds to troponin on actin

6th step of muscle contraction

Myosin is able to bind to actin and create power stroke

7th step of muscle contraction

Sarcomeres shorten causing muscle contraction

8th step of muscle contraction

Signal ends and calcium is reabsorbed into sarcoplasmic reticulum

9th step of muscle contraction

Myosin disconnect from actin

10th step of muscle contraction

Actin returns to original position (lengthening)

11th step of muscle contraction

Muscle relaxes

Latent phase

when nothing is occurring (at beginning)

Contraction phase

when muscle is depolarized (the peak of the graph)

Relaxation phase

when the muscle relaxes (the down slope of the graph, after the peak)

Muscle twitch

is a brief contraction, most common in body, homeostasis

Sustained (tetanus)

 the muscle does not relax, not sustainable in the body

Large motor unit

Large muscle, for board movements

Small motor unit

Small muscles, the finer movements (fingers)

Muscle tone

The healthy state of muscle, always semi-contracted, firm and ready to respond

Wave summation

muscle does not fully relax between each contraction, so beach contraction is stronger

Multiple motor unit summation (recruitment)

multiple motor units acting at the same time within a muscle

Muscle fatigue

The muscle can not contract, it has a lack of ATP, cramp

Aerobic exercise

an exercise that uses oxygen to make ATP(running)

Anaerobic exercise

does not use oxygen to make ATP, instead uses glucose/glycogen  (swimming)

Isometric

muscle contraction occurs but stays the same length (wall sits, plank)

Isotonic

muscle contracts and shortens (running, walking, bench press)

Muscles have 3 types of fibers

* Slow oxidative
* Fast oxidative
* Fast glycolytic

Muscle fibers

* some areas have more of a certain type
* activated at different times, when needed

Slow oxidative

* used all the time
* found in the back, neck, spine, posture
* thin

Slow oxidative

* slow contraction speed
* lots of mitochondria

Slow oxidative

* high blood flow
* high myoglobin

Slow oxidative

* small motor units
* high aerobic endurance (low fatigue)

Fast oxidative

* twitch movements, fast
* lots of mitochondria

Fast oxidative

* uses some glycogen
* high blood flow

Fast oxidative

* high myoglobin
* medium motor units

Fast oxidative

* not much endurance (medium rate of fatigue)
* legs, arms

Fast glycolytic

* very fast, fight or flight reaction
* legs and arms
* thick

Fast glycolytic

* not many mitochondria
* low blood flow

Fast glycolytic

* low myoglobin
* large motor unit
* high fatigue (no endurance)

Benefits of exercise

\-More oxygen flows to the muscle which means better endurance in those muscles and muscle tone

**Endurance training** 

* Grow more blood vessels to supply more oxygen 
* Make more myoglobin

**Strength Training** 

* More myofibrils (muscle stronger)
* Contractions stronger
* Muscle fibers swell

Muscle Twitch

Tetanus

Treppe

Wave Summation

Excitability

ability to respond to stimuli, ex. shivering

Contractility

ability to shorten forcibly (flexing)

Extensibility

ability to extend or stretch

Elasticity

ability to recoil and resume its resting length after stretching

Functions of connective tissue coverings

1. transmit the contraction from muscle fibers to the bone
2. contribute to muscle elasticity and reinforce/hold muscle together
3. provide route for blood vessels and nervous to and from the muscle (typically one artery and one nerve per muscle which branch once inside)

Functions of connective tissue coverings

2. contribute to muscle elasticity and reinforce/hold muscle together

Functions of connective tissue coverings

3. provide route for blood vessels and nervous to and from the muscle (typically one artery and one nerve per muscle which branch once inside)

Origin

less movable part of muscle attachment point, stationary

Insertion

movable part of a muscle attachment point

1st source of energy used

ATP

2nd source of energy used

Creatine

3rd source of energy used

Glucose

Oxygen Debt

difference of oxygen needed and oxygen given to muscles, owe muscle oxygen (causes deep breathing)

Oxygen Debt example

need 6.1 oxygen, only take in 1.2L, have a debt of 4.8L

Muscular dystrophy

group of muscle destroying disease

Steroids

enhance mass (raise oxygen carrying capability of muscles)