511 Midterm 3 - Muscles

What are the 3 Muscle types?

Striations?

Nucleus/Nuclei

In/Voluntary

Skeletal - striated, multi-nucleated, voluntary

Smooth - not striated, 1 nucleus, involuntary, spindle-shaped

Cardiac - striated, 1 nucleus, involuntary, branched w/intercalated disks

One muscle fiber/cell is surrounded by:

Sarcolemma

A bundle of muscle fibers/cells is called:

Fascicle

Each fascicle is connected by:

And surrounded by:

Endomysium - reticular fibers

Perimysium - reticular + collagen fibers

What is the outermost membrane holding all of the fascicles together?

Epimysium - collagen fibers

Tendons are an extension of what part of the muscle?

All of the collagen fibers of the connective tissue casings

Muscle fobers (cells) are composed of many Myofibrils

What are these Myofibrils made of?

Actin

Myosin

Describe the A-band, I-band, Z-disk, Sarcomere

A-band = Dark band = Myosin + actin overlap

I-band = Light band = Actin only, overlaps z-disk

Z-disk = connection of neighboring sarcomeres

Sarcomere = single contractile unit

Define Motor Unit

A neuron and all of the muscle fibers it innervates

Describe the Physiological process of a Muscle Contraction

1. Motor nerve impulse arrives
2. Acetylcholine is released, transferring impulse across synaptic cleft to sarcolemma
3. Impulse continues along sarcolemma surface then in through T-tubule (line up with z disks)
4. Impulse reaches sarcoplasmic reticulum (which wraps around the sarcomeres) and calcium is released
5. Myosin can now bind actin - “Crossbridging”
6. Energy from ATP allows myosin to pull actin —> sarcomere shortens

What do you call the portion of the SR thats thickened, right along the T-tubule?

Cistern

What steps of muscle contraction require ATP?

Crossbridging (Myosin binding to actin)

Release of Myosin Head

Pump Ca back into Sarcoplasmic Reticulum for relaxation/next contraction

How is the actin and myosin arranged differently in smooth muscle vs. skeletal muscle?

Instead of parallel lines (sarcomere —> striated appearance), filaments/contractile units crisscross around the cell

Instead of Z-disks, Smooth Muscle has…?

Dense Bodies - anchor the actin

What are the 2 types of Smooth Muscle?

Visceral (Single unit) - 1 neuron, multiple muscle cells

-For entire organs/structures that want to contract as a single unit

-Influenced by ANS, or able to contract w/o external stimulation (i.e stretching due to food entering the stomach, intestine, etc)

Multiunit smooth muscle - 1 neuron, 1 or few muscle cells

-Enables individually contracting certain cells/small groups within a larger area/structure

-Contractions require an impulse from the ANS

The Autonomic Nervous System (ANS) is divided into two sub divisions. Which response does each trigger? How does it affect cardiac and smooth muscle contraction?

Sympathetic (SNS) —> “Fight or Flight” —> inc CV, dec GI

Parasympathetic (PSN) —> “Rest and Digest” —> dec CV, inc GI

What are the 3 methods of ATP Synthesis used by the body?

1. Aerobic metabolism (sufficient O2)

- Aka Oxidative Phosphorylation

- Max energy extracted from glucose

2. Anaerobic metabolism (lack O2)

- Incomplete glucose breakdown

- Lactic acid byproduct (later metabolized when O2s back)

3. Creatine Phosphate - MUSCLES ONLY

- CT is used to convert ADP back to ATP

- Glucose breakdown + O2 —> ATP + CP

What 3 resources do muscles store for themselves? Why?

CP, Glucose as glycogen, O2 as myoglobin (only for a few sec)

Enables muscle to function whenever needed and not depend on the blood stream’s timing

How do muscles play into temperature regulation?

When ATP is burned, Heat is a byproduct (transported via bloodstream)

• Eliminating excess heat:

  • Panting/sweating ; water evaporation uses energy in the form of heat (endothermic), removing heat through the skin surface

  • Behavioral choices; sit in the shade or only come out at night

• Creating heat when cold:

  • Shivering = Spasmodic muscle contractions that increase heat productions

  • Tends to occur in larger muscles (skeletal) for most heat production

Side note: Liver = main thermos - heating the body when skeletal muscle contractions aren’t