Muscle Physiology/Histology [COMPLETE]

Flashcard set created to help GAC students with ANAT exam 2 with Harbitz.

Name the 3 types of muscle.

• Skeletal (striated, voluntary)

• Cardiac (striated, involuntary)

• Smooth (non-striated, involuntary)

What are three functions of the skeletal muscle?

• Produce joint movement

• Support soft tissues

• Store nutrient reserves

Connective tissue in muscles.

Dense regular connective tissue proper — becomes tendon at the end of muscle.

• Epimysium - surrounds outside of muscle (separates muscle from other structures)

• Perimysium - surrounds fascicles (bundles of cells)

• Endomysium - surrounds fibers

Organization of a skeletal muscle (from biggest to smallest)

Muscle — fascicles — fibers (cells) — myofibrils (multiple sarcomeres) — myofilaments (actin and myosin)

What are skeletal muscle fibers?

Very long cells, with hundreds of nuclei, and made through the fusion of myoblasts in utero

Muscle terminology - Fiber =

Cell

Muscle terminology - Sarcoplasm = ?

Cytoplasm

Muscle terminology - Sarcolemma = ?

Plasma membrane

Muscle terminology - Sarcoplasmic reticulum = ?

Ca++ storage organelle

What is a sarcomere? What is it made of?

Sarcomere is the smallest/basic functional unit of skeletal muscle. It is made up of 2 Z-discs and the actin and myosin filaments between them.

Muscle terminology - Myofilament = ?

Multiple sarcomeres connected end to end.

ATP production.

Muscle cells store enough ATP for a second contraction. After that, it must be made.

ATP can be recycled with the use of creatine phosphate.

ADP + creatine phosphate = ATP + creatine (enzyme used is creatine phosphokinase)

ATP + creatine = ADP + creatine phosphate

How long can last the production of ATP?

About 15 seconds.

Anaerobic glycolisis

Production of ATP from glucose without the use of oxygen. 

Produces enough ATP to keep muscle functioning a little while longer.

Causes build up of lactic acid.

Aerobic metabolism.

Production of ATP from glucose, fat, or protein with the use of oxygen.

Uses the Kreb’s Cycle to produce a lot of ATP

Can sustain muscle fiber contraction for long periods of time

Slow twitch and fast twitch muscle fibers.

Slow Twitch fibers - have high aerobic capacity, slow contraction, less powerful than Ft fibers, small motor units.

Fast Twitch A fibers - medium aerobic capacity and high anaerobic capacity, fast contraction speed.

Fast Twitch B fibers - low aerobic capacity and high anaerobic capacity, fast contraction speed, and large motor units

Muscle hypertrophy.

Muscle growth from heavy training

• Increases diameter of muscle fibers

• Increases number of myofibrils (actin and myosin)

• Increases mithochondria, glycogen reserves

Muscle atrophy

Lack of muscle activity. Reduces muscle size, tone, and power

Motor unit

Motor neuron and muscle fibers it innervates 

What do small motor units control?

Fine motor control

What do large motor units control?

Strength

Length-tension relationship of skeletal muscles.

• If a muscle and its fibers and sarcomeres are overly shortened at the beginning of contraction, less force (tension) can be produced. 

• If a muscle and its fibers and sarcomeres are overly stretched at the beginning of contraction, less force (tension) can be produced. 

If a muscle and its fibers and sarcomeres are just the right length with some overlap of actin and myosin, but not too much, then the maximal amount of tension can be produced. “The Goldylocks zone”

What are the 3 phases of a muscle fiber twitch?

• Latent phase

• Contraction phase

• Relaxation phase

What is the relationship between stimulus frequency and tension production?

Higher stimulus frequency = more tension production

What are the parts of a muscle?

• Origin - fixed end 

• Belly - where all the fibers are (middle)

• Insertion - movable end 

What are the skeletal muscle shapes?

• Parallel

• Convergent

• Circular

• Pennate

  • Unipennate

  • Bipennate

  • Multipennate

** Bipennate produces more tension because there are more muscle fibers/unit area

Describe muscles and their actions.

• Agonist (prime-mover) does the action. E.g., biceps brachii - flexes elbow 

• Synergist helps the prime mover to do the action (brachialis)

• Antagonist is the muscle that opposes the action and must relax for action to occur (e.g, triceps brachii)

• Fixator prevents movement at another joint (rotator cuff, deltoid, rhomboids)

Describe the types of muscle contraction.

• Isometric - tension production without a change in length

• Isotonic - tension production with a change in length

  • Concentric - shortening of the muscle

  • Eccentric - lengthening of the muscle

Define intrinsic muscles.

Intrinsic muscles are located within the structure or region they act on.

Define extrinsic muscles.

Extrinsic muscles are located outside the structure or region they act on.

Common flexor and extensor origin for wrist and hand muscles.

Flexor - medial epicondyle of humerus

Extensor - lateral epicondyle of humerus

Anterior muscles acting on the hip.

Ilipsoas - primary hip flexor

Lateral thigh muscles

Tensor fasciae latae

• Iliotibial band

  • Gerdy’s tubercle

Flexors of the knee

Hamstring muscles

• biceps femoris

• semitendinosis

• semimembranosis

Extensors of the knee

Quadriceps muscles

• Rectus femoris

• Vastus lateralis

• Vastus medialis

• Vastus intermedius

Sartorius - “tailor’s muscle”

Crosses leg

Gracilis

Adductor muscle of hip

Define Pes Anserine.

A structure on the inner side of the knee where three tendons converge and attach to the Tibia.

It is the point of insertion of three muscles: Sartorius, Gracilis, and Semitendinosis.

Define Pes Anserine Bursitis.

Occurs when the bursa inside your knee joint becomes irritated and inflamed.

Compartments of the leg.

• Anterior

• Lateral

• Deep posterior

• Superficial posterior