MIDTERM LEC 1: MUSCLE TISSUE Flashcards
Composed of cells that OPTIMIZE THE UNIVERSAL CELL PROPERTY OF CONTRACTILITY
MUSCLE TISSUE
Muscle cells are of __________ and
differentiate by a gradual process of cell
lengthening with abundant synthesis of the
myofibrillar proteins actin and myosin
MESODERMAL ORIGIN
PRIMARY FUNCTION OF MUSCLE TISSUE
GENERATE MOVEMENT/FORCE which in return
produces HEAT
(Shivering causes heat through contraction)
MUSCLE CELLS or MYOBLAST (a mesenchymal cell)
● Originates during embryonic development
from the ______________
MESODERM
LOCATION: Bone
STRIATIONS: Striated
CONTRACTION: Voluntary
NUCLEUS: Multinucleated (cylindrical)
SKELETAL MUSCLE TISSUE
LOCATION: Heart
STRIATIONS: Striated
CONTRACTION: Involuntary
NUCLEUS: Uninucleated (1-2 nuclei)
Intercalated discs (distinguishing form)
CARDIAC MUSCLE TISSUE
LOCATION: Hollow, visceral organs
STRIATIONS: Non - striated
CONTRACTION: Voluntary
NUCLEUS: Uninucleated (1-2 nuclei)
SMOOTH MUSCLE TISSUE (visceral muscle)
MESODERM undergo lengthening due to production of proteins:
❖ Myosin filaments- thick
❖ Actin filaments- thin
- Myosin and actin slide passed each other creating __________________
MUSCLE CONTRACTION
Contraction is caused by _____________
of thick myosin filaments along a thin actin filaments
SLIDING MECHANISM
Cytoplasm of muscle cells
● SARKOS means flesh (muscle)
● PLASMA means thing formed
SARCOPLASM
Specialized smooth endoplasmic reticulum
SARCOPLASMIC RETICULUM
plasma/cell membrane and its external lamina
● Sarkos + Gr. Lemma means husk
SARCOLEMMA
TYPES OF MUSCLE TISSUE
➢ No. of nucleus: bundles of very long, multinucleated cell
(10-100 μm)
➢ Cross-striation and has banding pattern
➢ Contraction:
❖ Quick
❖ Forceful
❖ Voluntary
➢ Cell shape: cylindrical
SKELETAL MUSCLE TISSUE
TYPES OF MUSCLE TISSUE
➢ consists of collections of fusiform cells which lack striations and have slow, weak & steady contraction
➢ Stimulated by the autonomic NVS & other hormones.
➢ No. of nucleus: uninucleated
➢ Lacks striation
➢ Contraction:
❖ Slow
❖ Involuntary
➢ Cell shape: SPINDLE or FUSIFORM; narrow at ends
SMOOTH MUSCLE TISSUE
TYPES OF MUSCLE TISSUE
➢ Also has striations
➢ No. of nucleus: 1-2 nucleus: usually uninucleated
➢ Cross 2- striation and has banding pattern
➢ Contraction:
❖ Vigorous
❖ Rhythmic
❖ Involuntary
➢ Cell shape: cylindrical
➢ Composed of elongated, often irregular branched cells bound to one another called:
❖ INTERCALATED DISCS which are unique to cardiac muscle
CARDIAC MUSCLE
Smooth and Cardiac muscles movements are controlled by _________________ and _____________
Autonomic Nervous System (ANS) and Hormones
increased cell volume
HYPERTROPHY
increased in the number of cells
HYPERPLASIA
● Consist of cylindrical multinucleated
cells with diameter of 10-100m
● Consist of MUSCLE FIBERS
● Contains progenitor cells called “muscle satellite” which undergoes
differentiation, replacing the damaged
nearby tissue
MUSCLE CELL
DEVELOPMENT OF SKELETAL MUSCLE
➢ Mesenchymal myoblasts fuse forming?
(MYOBLAST + MYOBLAST = ?)
MYOTUBES
● Remains adjacent to most fibers of differentiated skeletal muscle
➢ Remains adjacent to most fibers of differentiated skeletal muscle
➢ Part of MYOBLAST POPULATION
➢ Located on the external surfaces of muscle fibers
➢ Proliferate and produce new muscle fibers
➢ Small population of reserve progenitor cells
➢ Undergo differentiation
➢ Are active if there is injury nearby
➢ It replaces nearby damaged cells
SATELLITE CELLS = RESERVE CELLS
ORGANIZATION OF SKELETAL MUSCLE
dense irregular connective tissue overlying epimysium; adjacent to a tendon
DEEP FASCIA
tough connective tissue of a tendon which joins the muscle to bone, skin, or
another muscle
MYOTENDINOUS JUNCTION
ORGANIZATION OF A SKELETAL MUSCLE
● External sheath of dense irregular
connective tissue, SURROUNDS THE ENTIRE MUSCLE
● Nerves, blood vessels and lymphatics of
the muscle
EPIMYSIUM
● Surrounds each BUNDLE OF MUSCLE FIBER
termed fascicle
● Nerves, blood vessels and lymphatic
penetrate the perimysium to supply
each fascicle
PERIMYSIUM
makes up a functional
unit in which the fibers work
together
FASCICLE
● Surround the EXTERNAL LAMINA OF INDIVIDUAL MUSCLE FIBER
● carry oxygen to muscle fibers
ENDOMYSIUM
● JOIN THE MUSCLE TO THE BONE, skin or another muscle
● continuous with the tough connective tissue of a tendon
MYOTENDINOUS JUNCTION
ORGANIZATION WITHIN MUSCLE FIBER
● run parallel to the long axis fiber
● contain long cylindrical filament bundles
● Do not have a connective tissue covering
● COMPONENTS OF EACH MUSCLE FIBER
● Gives distinct bands resulting to striated appearance
● Consist of an end-to end repetitive
arrangement of sarcomeres
MYOFIBRILS
● REPETITIVE FUNCTIONAL UNIT OF CONTRACTILE APPARATUS
● Extends from Z disc to Z disc
● 2.5 μm long in resting muscle
- BASIC STRUCTURAL AND FUNCTIONAL UNIT OF SKELETAL MUSCLE
SARCOMERE
DURING RELAXATION SARCOMERE?
SHORTEN OR LENGTHEN?
LENGTHEN
DURING CONTRACTION SARCOMERE?
SHORTEN OR LENGTHEN?
SHORTEN
2 PATTERNS OF SARCOMERES
- DARK BANDS on the myofibril
- ANISOTROPIC or birefringent in polarized microscopy
➢ Creates contrasting image
➢ Contains myosin, reason why it is dark
➢ Bisected by: H zone (narrow, lens dense region)
A BAND
LENS DENSE REGION
H ZONE
2 PATTERNS OF SARCOMERES
● light bands
● isotropic, do not alter polarized light
➢ No refractive indices
➢ Bisected by: Z DISC (under TEM) - a dark transverse line between I band; zwischen = between
➢ Mitochondria, glycogen granules,
and small cisternae of SER occur
around the Z disc
➢ Arranged SYMMETRICALLY
I BAND
● zwischen = between
● DARK TRANSVERSE line
● repetitive functional subunits of the contractile apparatus
● 2.5 m in resting muscle
Z DISC
Thick and thin is composed of myosin
and F-actin
MYOFILAMENTS
● 1.6-μm long and 15-nm wide;
● They occupy the A band at the middle
region of the sarcomere
THICK MYOSIN FILAMENT
Synthesize proteins to make up microfilaments
MYOTUBES
it forms a TRANSIENT CROSS BRIDGES between the thick and thin filaments
Myosin head + actin
results to catalyzing energy release (actomyosin ATP activity)
Myosin head + ATP
2 tightly associated regulatory proteins
TROPOMYOSIN & TROPONIN
● 40 nm long coil of two polypeptide chains located in the groove between the two twisted actin strands
TROPOMYOSIN
TROPONIN 3 SUBUNITS
TnT
TnC
TnI
■ Attaches to tropomyosin
■ SERVE AS CARDIAC MARKER that
help detect acute myocardial infarction and to detect if there
is something wrong with the
heart
■ 3-4 hours in blood
■ After 3-4 hours may lead to erroneous result
TnT
Binds Ca 2+
TnC
Regulates the actin-myosin interaction
TnI
● Involve in the release of calcium
○ T tubule - trigger release of calcium
● NERVE - a stimulus for contraction
Motor neurons (specialized) + muscle it
stimulates = MOTOR UNIT
SARCOPLASMIC RETICULUM & TRANSVERSE TUBULE SYSTEM
● Cisternae of smooth ER and mitochondria
● specialized for Ca2+ sequestration and release
SARCOPLASMIC RETICULUM
● each sarcomere, two terminal cisternae of SR contact a deep invagination of the sarcolemma
● FORMING A TRIAD that triggers that triggers Ca2+ release (which is depolarized)
● INITIATE CALCIUM RELEASE and contraction of sarcomeres
● INVAGINATION: deep hollow part of sarcolemma
TRANSVERSE OR T-TUBULES
DEEP HOLLOW PART OF SARCOLEMMA
INVAGINATION
MECHANISM OF CONTRACTION
● Site where muscle and neuron meet
● Action potential/ nerve impulse
NEUROMUSCULAR JUNCTION (NMJ)
GAP between neuron and synaptic tissue
SYNAPTIC CLEFT
○ Resides inside neuron
○ Contain acetylcholine (neurotransmitter)
SYNAPTIC VESICLE
Different types of fibers can be identified on the basis of:
- Their maximal rate of contraction (fast or slow fibers)
- Their major pathway of ATP synthesis
(oxidative phosphorylation or
glycolysis)
SKELETAL MUSCLE FIBER TYPES
their maximal rate of contraction
FAST OR SLOW FIBERS
SKELETAL MUSCLE FIBER TYPES
their major pathway of ATP synthesis
OXIDATIVE PHOSPHORYLATION OR GLYCOLYSIS
globular sarcoplasmic protein similar to
hemoglobin which contains iron atoms and allows oxygen storage
MYOGLOBIN
3 MAJOR TYPES OF SKELETAL MUSCLE
FIBERS
● Adapted for SLOW CONTRACTIONS OVER A LONG PERIOD W/OUT FATIGUE
● Have many mitochondria, capillaries
and myoglobin
● Fibers DARK OR RED in color
SLOW OXIDATIVE FIBERS
3 MAJOR TYPES OF SKELETAL MUSCLE
FIBERS
● Specialized for RAPID, SHORT - TERM CONTRACTION
● Have a few mitochondria or capillaries and depends on anaerobic metabolism
● RAPID CONTRACTIONS LEAD TO RAPID FATIGUE as lactic acid is produced by glycolysis accumulates
Fast Glycolytic Fibers
LACTIC ACID causes?
MUSCLE PAIN
● Fibers have physiological and
histological features intermediate
between those of the other two types
Fast Oxidative-Glycolytic fibers
● An autoimmune disorder
● Instead of Ach, the ANTIBODY BINDS TO THE ANTIGENIC SITES
● Causing intermittent periods of skeletal muscle weakness, and drooping of upper eyelids
● FATALITY: affects muscle of lungs leading to respiratory failure
MYASTHENIA GRAVIS
- large actin-binding protein
- Located inside the sarcolemma
- Involved in the functional
organization of myofibrils
DYSTROPHIN
● Mutation of dystrophin gene
● Defective link ages between cytoskeleton and the extracellular matrix (ECM)
DUCHENNE MUSCULAR DYSTROPHY
Disruption of weak linkages cause
______of muscle fibers
ATROPHY
● INTERCALATED DISCS represent the interfaces between adjacent cells and consist of many junctional complexes
● It is INTRINSIC and SPONTANEOUS
● It is linked by GAP JUNCTIONS
● Consists of 1-2 nuclei
● Striated and involuntary contraction
● 2 regions to produce “electrical synapses”
○ Transverse regions - desmosomes (provide mechanical function) and fascia adherens (anchor cardiac cells together)
○ LONGITUDINALLY ORIENTED REGIONS of each intercalated discs
CARDIAC MUSCLE TISSUE
○ FORMING PROFILE JUNCTIONS between its terminal cisterns and T-tubules typically involve only one structure of each type
● Function is similar to skeletal muscle
● Rate of contraction results to autonomic nerves
● Contraction is PACEMAKER muscle fibers
DYADS
● Most common injury
● Tissue damage due to lack of oxygen
ISCHEMIA
causes myocardial infarction
Infarct
Aka visceral muscles
○ It lines and protects hollow, visceral
organs
● Specialized for slow, steady contraction under the influence of autonomic nerves and various hormones
○ Hormones such as OXYTOCIN
● Involuntary contraction
SMOOTH MUSCLE TISSUE
Smooth muscle tissue fibers
Elongated, tapering and nonstriated
Smooth muscle tissue is non striated because???
It lacks neuromuscular junctions
Smooth muscle tissue supplements?
Collagen, elastin and proteoglycans
SMT is the major component of?
Blood vessels
Digestive tract
Respiratory tract
Urinary tract
Reproductive tract
- 2 Contraction protein of Smooth Muscle Tissue:
- Calmodulin
- Myosin light-chain kinase (MLCK)
Contraction is mostly stimulated by
AUTONOMIC NERVES
● Benign tumor (localized)
● Common but seldom problematic
● Occurs in the wall of the uterus
○ Commonly called FIBROIDS
LEIOMYOMAS
● Hyper = above
● Trophe = nourishment
● Increase in cell size or volume
HYPERTROPHY
● Hyper = above; plasis = molding
● Increase in number of cells
● Takes place in smooth muscle where cells have
not lost the capacity to divide by mitosis
HYPERPLASIA
Decrease of volume or size
ATROPHY
Actin binding proteins which helps to connect the z disc
a - actinin
Accessory proteins in I band
- largest protein in the body
TITIN
