Muscles Chapter 28 Flashcards
Muscle major tissue types
a) Mucscle
b) Nervous
c) Connective
d) Epithelial
Tendons and ligaments
Tendons attach muscle to bone.
Ligaments attach bone to bone.
3 types of muscle tissue
a) Cardiac
b) Smooth
c) Skeletal
All derived from mesoderm.
Cardiac Muscle
Intercalated disks unique to cardiac muscle. Membranous boundary between adjacent cells. Single nucleus, striated, involuntary muscle.
Gap junctions also present in the cardiac tissue.
They allow direct transmission of the depolarizing current to go from cell to cell. Electrically coupled.
Gap Junctions
Connect the cytoplasm from one cell to another.
Cardiac muscle cells hormone
Artial atriuretic factor - acts on kidneys to help lower blood pressure by allowing Na and H2O loss.
Heart non regeneration
Damage to the heart does not result in cell regeneration, instead dead muscles cells are replaced by fibrous connective tissue.
Smooth Muscle
No striations, involuntary, and single nucleus.
Found in walls of blood vessels, GI tract, urinary, reproductive, urinary bladder, and internal organs.
Smooth muscles are regulated by
Hormones, ANS, local physiological conditions.
Unlike cardiac muscle regeneration is possible, can do mitosis.
Calmodulin
Ca2+ complex with calcium binding protein. It is involved in the contraction of smooth muscle.
Skeletal muscle
Striated, voluntary, and multinucleated.
No mitosis though regen can occur. Satellite cells reside on the external surface.
Epimysium
Dense connective tissue that surrounds muscle.
Muscle fibers can be
a) Red: many mitochondria, rich in Mb, rich in oxidative enzymes, and blood supply.
b) White: few mitochondria, poor in oxidative enzymes, poor in Mb, poor in blood supply.
c) Intermediate
Myofibrils are composed of
Thin and Thick filaments. Filament arrangement creates a pattern of light and dark bands.
Sarcomere
Structural and functional unit of myofibril. Part of the myofibril between two Z lines.
Dark bands = A bands
Light bands = I bands
H zone = center of A bands, lighter/pale area inside
Proteins contributing to Sarcomere
Titin: helps position of the thick filaments
Nebulin: Helps stabilize thin filaments.
Alpha - actinin: stabilize thin filaments
Muscle contraction will:
a) I bands shorten
b) H zone shortens
c) A bands do not change
d) Z lines come closer together
Bound to actin is
Tropomyosin: regulatory protein
Troponin complex: more proteins
When actin and myosin cannot associate:
Ach from presynaptic nerve binds to muscle fiber receptor and depolarizes it via T tubules. The sarcoplasmic reticulum releases Ca2+ through voltage gated Ca2+ release channels and enters the cytosol to bind to troponin. Troponin changes shape and it exposes the binding site for myosin.
Myosin head binds to the actin filaments with help of ATP.
ATP now binds to myosin head causing it to release it’s grip on actin. Hydrolysis of ATP returns its head back to original positions.
Actin, myosin, troponin 6 steps
1) Ach release to muscle fiber receptor, T tubules, depolarization of sarcoplasmic reticulum.
2) S.R. voltage gated releases Ca2+ into cytosol to bind troponin.
3) Change of shape of troponin, exposing binding site for myosin.
4) Myosin head binds to actin filament.
5) Myosin heads tilt towards center of sarcomere sliding the actin filament with them, ATP powered.
6) ATP binds to myosin head, to help release grip on actin.
Rigor Mortis
Lack of ATP prevents dissociation of actin and myosin. State of muscle contraction. Rigidity of the corpse disappears because the muscle proteins decompose. Putrescine and cadaverine are produced when proteins decompose.
Triad muscle
T tubule and two small cisternae of sarcoplasmic reticulum. When the membrane depolarizes Ca2+ is released, when depolarization ends, Ca2+ is transported back into the cisternae.
Process of recruitment
You brain recruits motor neurons along with motor units. It depends on the number of muscle fibers and the number of motor units activated.
Isotonic vs Isometric
Isotonic: muscle tension is constant; muscle shortens as it contracts.
isometric: muscle generates tension; muscles do not change length.
GTO
Golgi Tendon Organ. Mechanoreceptors that are found at the junctions of muscles and tendons. Regulates and aids in amount of force of muscles contraction.
