MIDTERM LEC 1: MUSCLE TISSUE Flashcards by Sunwoo's Berry

Composed of cells that OPTIMIZE THE UNIVERSAL CELL PROPERTY OF CONTRACTILITY

MUSCLE TISSUE

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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

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PRIMARY FUNCTION OF MUSCLE TISSUE

GENERATE MOVEMENT/FORCE which in return
produces HEAT
(Shivering causes heat through contraction)

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MUSCLE CELLS or MYOBLAST (a mesenchymal cell)
● Originates during embryonic development
from the ______________

MESODERM

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LOCATION: Bone
STRIATIONS: Striated
CONTRACTION: Voluntary
NUCLEUS: Multinucleated (cylindrical)

SKELETAL MUSCLE TISSUE

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LOCATION: Heart
STRIATIONS: Striated
CONTRACTION: Involuntary
NUCLEUS: Uninucleated (1-2 nuclei)
Intercalated discs (distinguishing form)

CARDIAC MUSCLE TISSUE

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LOCATION: Hollow, visceral organs
STRIATIONS: Non - striated
CONTRACTION: Voluntary
NUCLEUS: Uninucleated (1-2 nuclei)

SMOOTH MUSCLE TISSUE (visceral muscle)

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MESODERM undergo lengthening due to production of proteins:
❖ Myosin filaments- thick
❖ Actin filaments- thin
- Myosin and actin slide passed each other creating __________________

MUSCLE CONTRACTION

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Contraction is caused by _____________
of thick myosin filaments along a thin actin filaments

SLIDING MECHANISM

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Cytoplasm of muscle cells
● SARKOS means flesh (muscle)
● PLASMA means thing formed

SARCOPLASM

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Specialized smooth endoplasmic reticulum

SARCOPLASMIC RETICULUM

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plasma/cell membrane and its external lamina
● Sarkos + Gr. Lemma means husk

SARCOLEMMA

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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

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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

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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

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Smooth and Cardiac muscles movements are controlled by _________________ and _____________

Autonomic Nervous System (ANS) and Hormones

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increased cell volume

HYPERTROPHY

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increased in the number of cells

HYPERPLASIA

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● 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

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DEVELOPMENT OF SKELETAL MUSCLE

➢ Mesenchymal myoblasts fuse forming?
(MYOBLAST + MYOBLAST = ?)

MYOTUBES

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● 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

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ORGANIZATION OF SKELETAL MUSCLE
dense irregular connective tissue overlying epimysium; adjacent to a tendon

DEEP FASCIA

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tough connective tissue of a tendon which joins the muscle to bone, skin, or
another muscle

MYOTENDINOUS JUNCTION

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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

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● 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:

1. Their maximal rate of contraction (fast or slow fibers) 2. 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:

1. Calmodulin 2. 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

MIDTERM LEC 1: MUSCLE TISSUE Flashcards

(83 cards)