A&P Topic 9

Study for final

The three muscle types of the muscular system

• Skeletal muscle tissue

• Cardiac muscle tissue

• Smooth muscle tissue

Function of the muscular system

• Skeletal movement

Function of the muscular system

• Maintains posture

Function of the muscular system

• Supports/shields soft tissues

Function of the muscular system

• Guards openings

Function of the muscular system

• Maintains body temperature

Function of the muscular system

• Provides nutrients

What CT is fascia?

• Dense regular CT

What makes us tendons and aponeurosis at the end of muscles?

Fascia

Fascia: Epimysium

• Entire muscle

Fascia: Perimysium

• Separates fascicles (bundles of cells)

• Nerves/veins/arteries

• Stretch receptors

Fascia: Endomysium

• Separates each muscle fiber

• Capillaries

• Neurons

• Myosatellites (from myoblasts)

Another word for a muscle fiber

• Muscle cell

A muscle cell is made up of

• Myofibrils

  • Parallel & thread-like

Myofibril

• Bundle of myofilaments

  • Think & thin

  • Contractile proteins

Myofibrils are made of

• A bundle of myofilaments (thick & thin)

A sarcomere is

• The functional unit of a muscle fiber

A sarcomere contains:

• Z line

• A band

• I band

• M line

• H band

T-tubules are the?

• Tubes of the sarcolemma

Where are T-tubules located?

• At zones of overlap

Sarcoplasmic Reticulum (SR) - what do the Ca-ion pumps do/have?

• Sequester Ca2+

• Transmembrane potential

Sarcoplasmic Reticulum (SR) - has what channels?

• Gated channels

Structure of thin filaments: Filamentous actin is

• Two twisted rows

Structure of thin filaments: Globular actin has ?

• Active sites

Structure of thin filaments: Tropomyosin does ?

• Covers the active sites

Structure of thin filaments: Troponin does ?

• Binds

300 myosin molecules have what that bind to other molecules?

• Tails

300 myosin molecules tails have what heads?

• Free globular heads that pivot

  • Heads form cross-bridges with G-actin

300 myosin molecules tails have elastic titin that runs from ?

• The core of the filament to the Z line

Sliding filament theory:

• Myofilaments overlap

• Sarcomere shortens

Sarcolemma is polarized because ?

• Unequal distribution of charges across membrane

  • Membrane potential (mV)

What is the resting potential of a muscle fiber

• -85 mV

Neuromuscular Junction (NMJ)

• Voluntary

• Motor neuron

  • Action potential

    • Change in transmembrane potential

Synaptic terminals have ?

• Synaptic vesicles

Synaptic cleft is a ?

• Narrow gap

Motor end plate has

• Junctional folds of sarcolemma

• Many receptors, nuclei, & mitochondria

What is a neurotransmitter?

Acetylcholine (ACh)

When ACh is released, what does it stimulate?

• Muscle contractions

Where is Acetylcholinesterase found?

• The synaptic cleft

What does Acetylcholinesterase break ACh down into?

• Acetic acid + choline

Contraction cycle order

1. Active-site exposure

2. Cross-bridge formation

3. Myosin head pivoting

4. Cross-bridge detachement

5. Myosin reactivation

Active-site exposure

• Ca2+ binds

• Troponin moves tropomyosin from active sites

Cross-bridge formation

• Myosin heads bind to active sites

Myosin head pivoting

• “Power stroke” pulling actin toward center of sarcomere

• ADP + P are released

Cross-bridge detachment

• ATP removes the myosin-actin links

Myosin reactivation

• Myosin ATPase in myosin head

• Myosin head “recocks”as ATP —> ADP

Energy sources for contraction (3)

• Free ATP from cellular respiration (from fatty acids)

• Creatine phosphate (immediate energy)

• Glycogen —> glucose

Oxygen Supply: At rest or moderate exercise, what respiration can take place?

• Cellular respiration

Oxygen Supply: Strenuous activity —> what respiration must take place?

• Anaerobic respiration

Oxygen sources

• Diffuses from hemoglobin (Hb) in RBCs

• Myoglobin (Mb) in muscle

  • Redding-brown pigment

  • Temporary storage

Oxygen debt

• Oxygen is needed to restore normal conditions

Muscle fatigue

• Muscle fibers do not respond to stimuli

Cramps

• Involuntary muscle contractions

  • Electrolyte imbalance

  • Lack of ATP

Myogram

• Representation of a fibers response

A Motor unit

• A single motor neuron & all its muscle fibers

• Helps avoid fatigue during sustained contraction

Muscle tone

• Partially contracted

Concentric muscle contraction

• Muscle contracts with force greater than resistance and shortens

Eccentric muscle contraction

• Muscle contracts with force less than resistance and lengthens

Isometric muscle contraction

• Muscle contracts but does not change length