Download muscle - powerpoint

MUSCLE.
I. Types of muscle:
A. Striated muscle.
1. Skeletal muscle - voluntary muscle
http://cal.vet.upenn.edu/histo/muscle/skeletal.html
2. Cardiac muscle - heart muscle
http://www.ttuhsc.edu/courses/cbb/histo/muscle/pg08jp.html
II. Basic components of muscle cell organization
A. sarcolemma - plasmalemma of muscle cells - well developed basement
membrane. Sarcolemmal tubular invaginations called transverse tubules associated with the sarcoplasmic reticulum.
B. sarcoplasm - cytoplasm of muscle cells excluding the myofibrils.
C. sarcoplasmic reticulum - smooth endoplasmic reticulum of muscle cells.
D. sarcomere - basic contractile unit of a myofilament/myofibril (skeletal and cardiac
muscle only)
E. sarcosome - specialized long mitochondrion found (skeletal and cardiac
muscle only).
F. myofibril or myofilament - a string of sarcomeres (skeletal and cardiac muscle
only)
G. myofiber - a single muscle cell
II. Basic components of muscle cell organization
H. epimysium - thick layer of collagenous connective tissue that surrounds large bundles of
muscle.
I. perimysium - collagenous connective tissue continuous with epimysium that separates
fascicles of muscle cells.
J. fascicle - bundle of muscle cells (myofibers) bounded by perimysium.
K. endomysium - very thin layer of connective tissue that separates individual muscle cells.
fascicle
perimysium
http://training.seer.cancer.gov/module_anatomy/unit4_2_muscle_structure.html
III. Skeletal - voluntary muscle
http://www.siumed.edu/~dking2/ssb/NM016b.htm
A. As just described, epimysium, perimysium, and endomysium surrounds the
components of skeletal muscle as.
B. Skeletal muscle is connected to bone a tendon.
C. Individual muscle cells are syncytial
(multinucleate). Nuclei at periphery of cell.
D. Each individual muscle cell is called a muscle
fiber/myofiber. Within the sarcoplasm of these
cells are numerous myofilaments/myofibrils.
http://www.finchcms.edu/anatomy/histology/histology/muscle/h_m_8.htm
III. Skeletal - voluntary muscle
E. The myofilaments/myofibrils are linear arrays of structures known as sarcomeres connected in end to end repeating pattern. The sarcomeres contain filaments of actin
and myosin that interact to cause contraction of the muscle cells.
Skeletal/voluntary muscle
III. Skeletal - voluntary muscle
http://www.siumed.edu/~dking2/ssb/muscle.htm
III. Skeletal - voluntary muscle
F. Axons from CNS form multiple synapses on sarcolemma.
• Called myoneural junctions, neuromuscular junctions, or motor endplates.
• Contain synaptic vesicles filled with acetylcholine.
• Nervous impulses (action potentials) cause acetylcholine in vesicles to be released
into the gap between the axon and the muscle cell
• This initiates an electric action potential in the sarcolemma that causes the muscle
to contract.
http://www.gwc.maricopa.edu/class/bio201/histo/nmj.htm
http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab10/Examples/exmtrplt.htm
Electron micrograph of motor endplate synapse
http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/externes/Wartenberg/nmendpl1.html
A = Artefact; Ec = Euchromatin;
Hc = Heterochromatin;
H = Herzmuskelzelle;
Ko = Kollagenfasern (Querschnitt);
Ma = Macula adherens;
Mi = Mitochondrium (Crista-Typ);
Nf = Neurofilamente;
Nt = Neurotubuli;
P = Plasmalemm;
Po = postsynaptische Membran;
Pr = praesynaptische Membran;
S = synaptischer Spalt;
SR = sarcoplasmatisches Reticulum;
SV = synaptische Vesikel;
TB = terminaler Bouton (= motorische Endplatte,
enthält Axolemma).
G. Sarcoplasmic reticulum - stores calcium that is released to cause contraction.
1. Organization - extensions of the sarcolemma called Transverse tubules (Ttubules) extend between parallel cisternae of the sarcoplasmic reticulum that
encircle individual myofilaments (myofibrils).
2. Allows very rapid transmission of
surface action potentials to the
interior of the cell ----> releasing
calcium ions from the sarcoplasmic
reticulum and allowing the
sarcomeres of the myofilaments to all
contract at essentially the same time.
V. Cardiac muscle
http://www.cytochemistry.net/cell-biology/medical/practice_practical_muscle.htm
A. Unlike striated muscle, cardiac muscle cells are not a syncytium for most
part, though some cells may have two nuclei.
B. The structure is similar to that of striated skeletal muscle - myofilaments
(myofibrils) composed of sarcomeres are present. Contraction is mediated
by release of Ca+2 from sarcoplasmic reticulum. Fewer T-tubules.
http://www.finchcms.edu/anatomy/histology/histology/muscle/h_m_13.html
V. Cardiac muscle
http://www.siumed.edu/~dking2/crr/cvguide.htm#heart
C. Cardiac muscle differs from skeletal muscle in four major ways,
1. cardiac muscle cells are branched and
2. have 1-2 nuclei per cell
3. nucleus located in center of cell in cross-sections
4. muscle cells held together by intercalated disks.
Intercalated disks:
a. Interdigitating regions of the
sarcolemma of adjacent cardiac
muscle cells that
b. Hold the cells together
c. Act to conduct ionic changes
between cells.
d. The intercalated disks form the
irregular, jagged, dark lines that are
characteristic of stained cardiac
muscle.
V. Cardiac muscle
2. The intercalated disk is composed of a number of structures that are
organized along adjacent muscle cell sarcolemmas in a repeating array,
a. Macula adherens (desmosomes) previously described structures that
hold cells together. Located between
adjacent myofibers.
b. zonula adherens - Located where
myofilaments end at muscle cell
sarcolemma.
c. gap junctions - allow transfer of
ions between muscle cells. Allows
cells to coordinate their activities.
Action potentials can spread quickly
between the sarcoplasmic reticula of
adjacent cardiac muscle cells via gap
junctions.
V. Cardiac muscle
D. The sarcoplasmic reticulum of cardiac muscle cells is not as regular as that of
skeletal/voluntary muscle.
E. Purkinje fibers - modified cardiac muscle cells found in the ventricle that are
specialized for conduction of electrical impulses. Conduct the contraction impulses
that originate in the sinoatrial node (then passed via atrioventricular node) to the
cardiac muscle fibers.
VI. Smooth muscle
A. This sort of muscle consists of long, overlapping, spindle shaped cells that look
similar to fibroblasts.
B. Smooth muscle cells similarity to fibroblasts is evident in that they are able
to synthesize collagen, elastin, and proteoglycans.
Scanning EM of vascular smooth muscle
http://mphywww.tamu.edu/VSM-cells-DIC.html
VI. Smooth muscle
C. There are no sarcomere structures, but
filaments of actin and a type of myosin are
present. Thus, contraction is much less
organized and occurs more slowly than it does
in skeletal or cardiac muscle. Another reason
for this slower contraction is that smooth
muscle cells do not contain a transverse tubule
system.
D. The actin and myosin filaments are not
constrained by a sarcomere/myofilament
arrangement. Thus, the actin and myosin
filaments are able to achieve a greater degree of
overlap when contraction occurs resulting in a
greater degree of contraction.
http://www.mindquest.net/biology/images/histology/smooth-muscle-ls.jpg
VI. Smooth muscle
E. Smooth muscle cells have the ability
to remain contracted for long periods of
time.
F. Bundles of smooth muscle are
organized as fascicles similar to what is
seen in striated and cardiac muscle,
Thus, a perimysium with endomysium
between cells and epimysium
deliniating bundles of fascicles can be
identified.
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Muscle/Muscle.htm#LABSMOOTH
VI. Smooth muscle
G. The contraction of smooth muscle cells is
involuntary and the neuromuscular junctions
controlling contractile rhythms may be on the
surrounding epimysium rather than directly on
muscle cells. As a result, neurotransmitters have
to diffuse across this connective tissue layer and
onto the plasmalemma of the smooth muscle cells
in order to have an effect on contraction. This is
another reason for the slower contraction of
smooth muscle cells.
H. Smooth muscles exhibit spontaneous
contractile activity (doesn't require nervous
stimulation). Thus, the innervation that is present
acts to modify the contractile activity rather than
initiate it.
http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Muscle/Muscle.htm#LABSMOOTH