Where is skeletal muscle located?

Widely Distributed:

Deep to skin and hypodermis (subcutaneous fascia) in most body regions.

Mainly bone.

Origin and/or insertion

Insertion: Point at which a muscle attaches to the skin, a bone, or another muscle. The insertion attaches to the structure that will be moved by the contraction of the muscle.

Origin: The structure that the origin is attached to is not moved by the contraction of the muscle

Muscles of facial expressions.

Intrinsic tongue muscles.

What are the characteristics of skeletal muscle cells(fibers)?

• Long
• Cylindrical
• Unbranched
• Multinucleated
• Striated

• Muscle
• Connective tissue
• Nerve
• Epithelium

• Endomysium(around each fiber/cell)
• Perimysium
• Epimysium

• Big cells with nuclei at the periphery
• Polygonal cells (paving stones)

Basic contractile subunit of myofibrils.

Z line marks the ends.

Always the same size.

Goes from one side of the Myosin(thick) filaments to the other. It could over lap thin filaments as well.

Very reflective

Contains only thin(actin) filaments.

Goes from A-Band to A-Band

Z line goes through the middle of it

The zone of the A Band that does not over lap thin filaments.

Gets small during contractions.

Middle of the Sarcomer.

Anchors central portion of the thick filaments together.

• Actin
• Tropomyosin
• Troponin

α-actinin (also there)

Globular protein that conatins the binding site for attachment with myosin cross bridge.

Polymerized into double stranded filamentous actin (F-actin)

Filamentous protein that blocks the myosin-binding sites on the Actin

"cock blocker"

Protein Complex

TnT: attaches complex to tropomyosin

TnI: Inhibits. Blocks binding site on Actin

TnC: Ca²⁺ binding protein for initiation of contraction.

2 Heavy chains: α helix (double helical)

4 Light chains: forms 2 globular heads

Looks like a double ended golf club.

Titin

•  It extends into the thick filaments from the Z-line.
• Flexibly stabalizes thick filament position.

Invagination of the sarcolemma into the cell at the A-I Band junction.

Surrounds Myofibrils

Expansions of sarcoplasmic reticulum near T-tubules.

T-tubules with 2 adjoining terminal cristea.

Located at A-I Band junction

Myo-D

Myof-5

The cells would just be fibroblasts.

Slows progression of myogenesis.

It may block satallite activation.

Without it muscles grow like crazy.

• Disuse
• Cachexia: cancers, loose appetite. Body robs protein from muscle.
• Neurogenic: nerve severed

A Band: stays the same

H Band: shrinks

I Band: shrinks

A-I overlap: increases

Acetylcholinesterase

Located at post synapse

Allows sarcolemma to repolarize

Nicotinic ACh receptor

Autoimmune Neuromuscular Disease

Body makes autoantibodies to ACh receptors.

And the cleft gets wider and flatter. Loses some surface area.

Progressive loss in neuromuscular control.

Ryanodine Receptors

Located in SR terminal cisternea membranes.

Lets you know where you are in space.(with your eyes closed)

Impaired by alcohol.

• Endocardium
• Myocardium
• Epicardium

Endothelium of cardiac underlain by loose connective tissue.

Cardiac muscle

Thickest layer

Bigger in ventricals 

Also called viceral pericardium

Outside layer of Cardiac muscle

Denser connective tissue covered with mesothelium

Right: thinner. Pumps blood to lungs to get reoxygenated.

Left: Thicker. Pumps blood to the rest of the body.

• Branched fibers (cross section has irregular shape)
• Central nuclei
• Intercalated disks- where one cell joins to another
• Intercellular spaces- accomodate abundant capillaries

What are the cell(fiber) types found in cardiac muscle?

• Atrial
• Ventricular
• Purkinje

• Smaller cells(than ventricular)
• Fewer T-tubules (response to stimulus is slower)
• Small dense granules containing atrial natriuretic peptide.

• Hormone
• derived from latin root "Natrium" which means sodium.
• puts Na into the urine
• Water follows the solute and lowers blood pressure

• Larger cells(than Atrium)
• More T-tubules (response to stimuli is faster
• No granules

• Modified cardiac muscle fibers
• Located between ventricular endocardium and contractile muscle.
• Less dense
• Looks like air is pumped into it
• Allows current to flow more easily
• Dont want them to contract too much

Cardiac Muscle

Intercalated disks joined end-to-end and the spaces between them cause the zig-zag.

Fascia Adherens: like zonula but its a plate instead of a belt. anchored by Actin filaments.

Macula Adherens: Desmosome. anchored with Desmin intermediate filaments.

Gap Junctions: Allows ions to pass.

• T-Tubules at Z-lines (not A-I junction)
• Terminal Cisternea is small
• Dyads, not Traids.(only one terminal cristea)
• Sarcoplasmic Reticulum is less extensive. Less developed.

• Sequential extracellular signal-gene expression response.
• Signaling activates or represses selected genes in proper order to elicit cardiac muscle phenotype.
• Purkinje fibers from same lineage but diverge from contractile muscle path.

Type I, oxidative

Specialized version

1. SA node (pace maker)
2. AV node

• Biggest cause of heart attack
• Blood is blocked from getting to heart.
• not enough blood/O₂ is getting to the heart.
• Left intraventricular
• Reperfusion: results when Oxygen is rushed in after it has been blocked off. Results in inflammation and oxidative damage.

60-100/min

Too Fast: Tachycardia

Too Slow: Bradycardia

• Not enough O₂
• Damages mitochondria
• Causes Cytochrome C release.
• initiates apoptosis

Tunica Media

Middle layer of an artery or vein.

• the "tracts"
• Splenic Capsule
• Skin(arrector pili)

• Visceral smooth muscle located in the skin.
• connected to hair and causes goose bumps.

• Elongated
• Overlapping cells
• No striations
• Single, central, pale, nucleus/cell

• Tightly packed
• Less Vascular
• Little connective tissue
• Dont see all of the nuclei because of overlapping

Spindle-Shaped=Fusiform

Actin: radiate from dense bodies

Myosin: overlap between actin when needed.

Dense bodies: are attached to each other by the actin and myosin filaments. serve as "Z" lines

Phallicidin (stains filaments)

Hoechst (stains nucleus)