Histo

Red Skeletal Muscle: aerobic, smaller, slow, sustained contraction, more mitochondria, more myoglobin, cytochromes, less complex NMJs.

White Skeletal Muscle: anaerobic, larger, fast twitch, fewer mitochondria, less myoglobin, cytochromes, more complex NMJs.

Fibers that exhibit characteristics intermediate between red and white fibers. They are red in color and are prevalent in red muscle.

The NMJs are more complex in white than in red fibers. The number of synaptic vesicles and the number and complexity of the junctional folds are much greater in the white fibers and the least in the red ones.

The distribution of fiber types within a muscle is regulated by the type of innervation.

The sarcolemma and external basal lamina interactions.

It anchors the cortical actin network to the ECM through intercaction of its N-terminus with F-actin, and the interaction of its C-terminus with a transmembrane complex of dystrophin-associated proteins and glycoproteins.

These patients get muscle weakness.

Mediates the link between myofibrillar proteins inside the muscle cell and the extracellular basal lamina by stabilizing it and protecting its physical integrity.

Endomysium, perimysium, epimysium

It's connective tissue that surrounds each myofibril. It is composed of a network of collagenous and reticular fibers and varying amounts of elastic fibers. Some CT cells, fine capillaries, and nerves are also present. It blends with the extracellular basal lamina of the myofiber.

Surrounds bundles of several myofibrils grouped into a fascicle. It is loose, irregularly arranged and composed mainly of collagenous CT. This layer brings in and distributes blood vessels and nerves throughout the body.

A dense CT sheath that binds fascicles together to form a muscle body. (Also known as deep fascia).

Perimysium.

Attaches skeletal muscle to the bone.

The sarcolemma of individual myofibers interdigitates with the collagen and ground substance of the ECM of the tendon.

Encapsulated, lymph filled, fusiform structures that lie parallel to the myofibers in connective tissue between bundles of myofibers.

Nuclear bag fibers and nuclear chain fibers. These associate with two types of sensory nerve fibers: annulospiral endings and flower-spray endings.

When a muscle fiber is stretched, the sensory fiber receptors are distorted and stimulated which relays information to lead to a muscle contraction.

Protects the tendon

Provides inhibitory feedback to relax the muscle

Causes contraction of the tendon

Composed of collagen fibers of tendon and sensory nerve endings

Stimulated by excessive stretching of the collagen fibers.

They have opposing actions that together integrate spinal reflex systems.

They are muscle stem cells that proliferate after muscle injury.

They are mononucleated and reside just underneath the basal lamina of the myofibers.

Satellite cells go on to generate new myoblasts which go on to fuse and form myotubes.

The basal lamina must still be intact.

1. Only found in the myocardium
2. Involuntary
3. Striated
4. Branching histology
5. 10-20nm dia; 100-150 nm length
6. One to two central nuclei

Gap junctions that allow for electronic coupling between adjacent cardiac muscle cells so they can act in sync.

All muscle fibers acting as one unit

Alpha-actinin: Z-line protein
Myomesin: M-line protein
Titin: Thick filament ass. protein
Nebulin: Thin filament ass. protein

An intermediate filament protein associated with desmosomes of the intercalated discs. Overall, it provides structural support.

They attach to the cytoplasmic plaques of the desmosomes.

30%

They bind neighboring cardiac myofibers together and anchor them at the sarcolemma. Also provide gap junctions for electronic communication.

Desmosomes, fascia (zonula) adherens and gap junctions.

They anchor actin filaments of the terminal sarcomeres to the plasma membrane.

They are prominent in cardiac and less extensive in skeletal muscle. In cardiac muscles, they are also arranded in diads as opposed to triads of skeletal. Lastly, they present at the Z-lines (cardiac) rather than the A-I band junctions (skeletal). The T-tubules are thicker and SR less extensive in skeletal muscle. Cardiac more dependent on extracellular calcium and Skeletal relies solely on intracellular calcium for a muscle contraction.

Cardiac muscle has more mitochondria, more deposits of glycogen, more mitochondria, and highly elaborate mitochondrial cristae.

Cardiac muscle contains for less CT.

Individual myofibers are surrounded by a endomysium. These are then bundled into groups surrounded by a perimysium.

Modified cardiac myocytes that conduct impulses from the AV node trhough the ventricular septum into the ventricles.

Atrium: muscle cells are smaller and have less T-tubules. They also produce ANF (atrial natriuretic factor) and BNF (brain natriuretic factor).

These hormones act on the kidneys to stimulate sodium and water loss and thereby coordinate the regulation of blood pressure and body fluids.

It is secreted as a prohormone that is cleaved to form the active hormone. It is synthesized and processed in the ER-Golgi

Membrane bound granules that the ANF prohormone is stored near the golgi complex.

Dia: 3-8 microm
Length: 15-200 microm

Often arranged in layers with different orientations

The cytoplasmic organelles are confined to a conical region on each of the nucleus (perinuclear cytoplasm). Contain dense bodies which contain alpha-actinin which are analogues to the Z-lines of striated muscle serving as anchoring regions for the actin-myofilaments. Attachment plaques are also associated with this anchoring.

Desmin and vimentin

Smooth muscle has an actin:myosin ratio of 15:1.

The nuclei coils up

It contains a poorly elaborated ER which stores/regulates calcium. There are also caveolae and gap junctions. No T-tubules are present.

Unitary (visceral) smooth muscle and Multi-unit smooth muscle.

Sustained contractions, waves of contractions in the walls of organs, connected by gap junctions, only a few cells are innervated.

rapid, precise graded contractions e.g. pilli, eye, each cell is innervated

Smooth muscle is surrounded by basal lamina that blends into a delicate network of reticular, elastic, and fine collagenous fibers.

The CT fibers are produced by the smooth muscle cells themselves rather than fibroblasts.