Muscle Tissue: Types, Structure, and Function 2/2

Terminal fibers pass through the endomysium and synapse with muscle fibers (MEP)

Nerves branch out in the perimysium, and their terminal fibers go where?

the axon has branches that reach every muscle fiber (covered by Schawnn cells)

How does one motor neuron innervate several muscle fibers?

form dilations located within trough of the muscle cell

The end of axonal branches form what?

Mitochondria and synaptic vesicles (stores Ach)

The axon terminal contains what key structures?

Sarcolemma

Plasma membrane of muscle fibers.

between axon and sarcolemma

What is the synaptic cleft?

Motor unit

One motor neuron and all its innervated muscle fibers is called a?

Junctional folds

Folds in sarcolemma with Ach receptors.

Proprioceptors

Sensory receptors providing body position awareness.

Muscle spindle

Stretch receptor within skeletal muscle.

Proprioceptor

Muscle spindle is a type of?

Modified perimysium (DCT)

What encapsulates a muscle spindle?

Intrafusal fibers (thin muscle cells)

What is found on the INSIDE of the muscle spindle?

Sensory axons

What surrounds the intrafusal fibers?

Found among collagen fibers of myotendinous junction.

Golgi tendon organ is a type of stretch receptor that is found where?

It is smaller than the muscle spindle

Compare the size of a golgi tendon organ to the muscle spindle

Slow oxidative fibers

Fatigue-resistant fibers with high mitochondria content.

Myoglobin and many surrounding capillaries

Aside from high mitochondria, slow oxidative fibers also contain an abundance of ?

Dark or red when fresh

Slow oxidative (slow contracting) muscle fibers stain what color?

Fast glycolytic fibers

Fatigable fibers relying on anaerobic glycolysis.

few mitochondria

few surrounding capillaries

Fast glycolytic muscle fibers contain few ________ and ________.

Rapid, short-term contractions and accumalates lactic acid

Describe the contractions of fast glycolytic fibers

White when fresh

What color do fast glycolytic muscle fibers stain?

Fast oxidative-glycolytic fibers

Intermediate fibers with mixed characteristics.

Cardiocytes or myocytes

Cardiac muscle cells with striated appearance and a single nucleus.

Intercalated discs

Connections between cardiocytes for synchronized contraction.

Thin endomysium

&

Thick perimysium

Subtypes of tissues in cardiac muscle

Surrounds myocytes

Thin endomysium surrounds what?

The thick perimysium that encloses the fasicles

What form the cardiac skeleton?

Desmosomes and adherens junctions

What is found in the transverse regions of intercalated discs?

Gap junctions (electrical synapses)

What is found in the longitudinal regions of intercalated discs? (parallel to myofibrils)

Long and abundant mitochondria

T-tubules longer in ventricles

Secretory granules

Organized sarcoplasmic reticulum

Ultrastructure of cardiocytes reveal what features?

Dyads (found in cardiocytes)

T-tubule + one terminal cisterna forms a ?

Perinuclear glycogen granules (appears clear)

The nucleus of a cardiocyte is surrounded by what?

Fatty acids as triglycerides

In cardiocytes, what is stored in their lipid droplets?

Atrial natriuretic peptide (ANP)

Hormone that reduces blood pressure when the atrium stretches too much.

1. Slow, steady contraction

2. Synthesis of ECM components

Two functions of smooth muscle include?

Visceral muscle

Another name for smooth muscle?

Thick, branching perimysium

Endomysium composed of type I and type III collagen**

Describe the perimysium and enomysium of smooth muscle

Fusiform cells

Spindle-shaped smooth muscle cells with one elongated nucleus.

Closely packed, non striated, and linked by numerous gap junctions

Describe the organization of smooth muscle cells.

Caveolae

Smooth muscle cells lack T-tubules but instead contain what?

Plasmalemma invaginations that control Ca2+ release from the sarcoplasmic reticulum

Caveolae is an invagination of the ?

Bundles of thick and thin filaments crisscross the sarcoplasm obliquely. Mechanism similar to striated muscle (but fewer crossbridges)

How does smooth muscle contract?

Calmodulin and MCLK [myosin light chain kinase]

Calcium binds to troponin in skeletal muscle, but what binds Ca2+ in smooth muscle?

Dense bodies (similar to Z discs)

Anchors actin filaments in smooth muscle through the use of a-actin.

Transmitters of contractile force within and between cell

Dense bodies function as transmitters of ?

Distorts the cells and nucleus

Contractions does what to the cells and nuclei

1. ANS

2. Paracrine factors (GI)

3. Hormones (uterus)

4. No well-defined junctions

5. Swellings of ANS nerves

6. Synaptic vesicles (ACh)

7. Gap junction propagations

What are the regulators of contraction? (7 total)

Regeneration of skeletal muscle

Slow process using satellite cells for repair.

Regeneration of cardiac muscle

Very poor due to lack of satellite cells.

Regeneration of visceral muscle (smooth muscle)

Rapid due to undifferentiated cells allowing repair.