CTO #12
Terms
undefined, object
copy deck
- three types of muscle
-
1. striated voluntary skeletal muscle
2. striated involuntary skeletal muscle
3. involuntary smooth muscle - functions of muscle tissue in animals
-
1. producing body mvmts
2. stabilizing body positions
3. regulating organ volume
4. regulating the flow of substances within the body
5. the production of heat - how is heat produced by one of the muscle types?
- involuntary contractions of skeltal muscle (SHIVERING)
- epimyseum
- dense CT sheath encasing most skeletal muscle, corresponds to deep fascia
- fasicles
- bundles of muscle fibers encased by perimyseum
- perimyseum
- CT layer encasing fasicles of muscle fibers
- muscle fibers
- are the muscle cells, each separated by surrounding endomysium by an external lamina
- sarcolemma
- cell membrane of a muscle fiber or muscle cell
- endomysium
- layer of loose connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers
- tendons
- dense, regular CT, attach muscle to bone, provide stability for muscle contraction and transmit the force of movement from muscle to bone
- myoblasts
-
type of stem cells that can fuse together to form multinucleate skeletal muscle fibers
Myoblasts that do not form muscle fibers differentiate into satellite cells. - skeletal muscle nuclei
-
multiple (multinucleate)
located on the fiber periphery, immediately beneath the sarcolemma (plasma membrane) - myofibrils
- bundles of myofilaments within the muscle cell, arranged in consistent alignment of repeated sarcomeres
- sarcomeres
- fundamental units of contraction
- major myofilaments of the sarcomeres
- (thin) actin and (thick) myosin II (with associated proteins)
- thin filaments of sarcomere
-
actin filaments anchored by their + ends (barbed ends) to the Z-line
associated with nebulin (scaffolding protein)
and bound to troponin-tropomyosin regulatory complex - how and where is actin anchored in sarcomere?
- by + ends (barbed ends) to the Z-line
- nebulin
- scaffolding protein associated with actin in sarcomeres
- myosin II
- thick filaments of sarcomeres
- titin
- protein associated with myosin II in sarcomere. prevemts sarcomere from overstretching
- A band
- (anisotropic) darker band in center of sarcomere associated with myosin (thicker fiber)
- I band
- lighter bands between Z discs and A band, contain only actin filaments
- H zone
- "Heller" (lighter) region in the middle of the A band, brighter (only myosin, no overlap
- Z disc
- "Zwischen discs" protein disks between each sarcomere
- M line
- "Mittel" of sarcomere, proteins including myomesin, titin and creatine kinase, structural proteins help titin and myosin maintain their 3-dimensional structure
- sarcolemma is stabilized by
- a membrane cytoskeleton composed of actin, dystrophin and other proteins
- muscular dystrophy is characterized by defects in what?
- dystrophin
- dystrophin
- protein essential for maintaining connection between cytoskeleton of muscle fiber and ECM (deficiency leads to muscular dystrophy)
- myotendinous junction
- integrins connect actin filaments of terminal sarcomere and the ECM
- motor unit
- a single axon, together with all the muscle fibers it innervates
- neuromuscular junctions
- location of motor end plate, where axon and muscle fibers meet
- what triggers depolarization of the sarcolemma?
- release of acetylcholine
- myasthenia gravis
- disease where autoantibodies against acetylcholine receptor result in impaired muscle function
- Transverse tubules
- invaginations of the membrane that facilitate the propogation of the depolarization of the sarcolemma throughout the muscle fiber
- triads
-
found in skeletal muscle
association of two terminal cisternae of the sarcoplasmic reticulum with a T-tubule
facilitates calcium release from the SR - power stroke
-
the molecular contraction event, when crossbridge moves toward H zone
(myosin hydrolyzes ATP and goes through a series of conformational changes) - rigor state
- when actin and myosin are strongly bound
- characteristics of cardiac muscle cells
-
centrally located single nucleus (uninucleate)
branching
intercellular junctional complexes through intercalated disks - intercalated disks
- combination of desmosomes, fascia adherens and gap junctions
- dyads
- association of the terminal cisternae of the SR and T-tubules of cardiac muscle cells (less elaborate then triads of skeletal muscle)
- characteristics of smooth muscle cells
-
single, often fusiform cells
centrally located nucleus
often connected by gap junctions
no sarcomeres
no calcium-regulated troponin-tropomysin system - what provides structural framework for smooth muscle cells?
- intermediate filaments
- dense plaques
- sites on plasma membrane of smooth muscle cells where actin filaments (interdigitating with myosin) are anchored
- smooth muscle cells are activated by
- the stimulation of myosin light chains by a myosin light chain kinase (MLCK) that triggers acto-myosin contraction
- examples of possible activation of MLCK pathway
- calcium-calmodulin pathway or cAMP activation
- multiunit type of smooth muscle
- under tight control, heavily innervated (such as pupillary muscles)
- visceral or unitary type of smooth muscle
- less-densely innervated, but has more gap junctions to permit a slow, coordinated contraction of the smooth muscle (as in peristalsis)
- type of innervation associated with skeletal muscle
- voluntary
- type of innervation associated with cardiac muscle
- involuntary
- type of innervation associated with smooth muscle
- involuntary
- efferent innervation of skeletal muscle
- somatic
- efferent innervation of cardiac muscle
- autonomic
- efferent innervation of smooth muscle
- autonomic
- regulation of skeletal muscle contraction
- binding of Ca2_ to TnC, causes tropomyosin movement and exposes myosin-binding sites on actin filaments
- regulation of cardiac muscle contraction
- binding of Ca2_ to TnC, causes tropomyosin movement and exposes myosin-binding sites on actin filaments
- regulation of smooth muscle contraction
- by phosphorylation of myosin light chian by myosin light chain kinase in the presence of Ca2+-calmodulin complex
- what types of muscle can undergo mitosis?
- only smooth muscle can undergo mitosis under normal conditions
- What types of muscle cells can undergo regeneration?
-
smooth muscle cells
and limited capacity in skeletal muscle sattelite and myogenic cells from bone marrow - What types of muscle have cell-to-cell junctions?
-
1. The intercalated disks of cardiac muscle have: fascia adherens, macula adherens, and gap junctions
2. Smooth muscle cells are joined via gap junctions (nexus) - morphology of skeletal muscle cell
-
large, elongate
10-100 micrometers in diameter
up to 100 cm in length - morphology of cardiac muscle cell
-
short, narrow cell
10-15 micrometers in diameter
80-100 micrometers in length - morphology of smooth muscle cell
-
short, elongate, fusiform cell
0.2-2 micrometers in diameter
20-200 micrometers in length