Muscle Tissue Histo Flashcards Preview

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Flashcards in Muscle Tissue Histo Deck (47)
1

Muscle cytoplasm

Cytoplasm = Sarcoplasm

2

Smooth ER

Smooth Endoplasmic Reticulum = Sarcoplasmic Reticulum

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Plasma Membrane or Plasmalemma

Sarcolemma

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Muscle Cell

Muscle Fiber or Myofiber

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Special Characteristics of Muscle Tissue

Excitability (or Irritability)
Contractility
Extensibility
Elasticity

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Functions of Muscle Tissue:

Producing Movement
Maintaining Posture
Stabilizing Joints
Generating Heat (i.e. Thermogenesis)

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Skeletal Muscle

Voluntary control
Strong, quick contractions
Striated
Large, elongated, cylindrical, syncytial (multinucleated) cells
Peripheral, oval nuclei

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Cardiac Muscle

Involuntary control
Strong, quick contractions
Striated
Uninucleated cells
Centrally located nucleus
Elongated and branched cells joined by intercalated discs

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Smooth Muscle

Involuntary control
Weak, slow contractions
Nonstriated
Uninucleated, fusiform cells
Centrally located nucleus

10

Type I Skeletal

Slow, Red Oxidative Fibers
Many mitochondria and lots of myoglobin (dark red color)
Derive energy primarily from aerobic oxidative phosphorylation of fatty acids

Adapted for slow, continuous contractions over long periods

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Type IIa

Fast, Intermediate Oxidative-Glycolytic Fibers
Many mitochondria, and lots of myoglobin and glycogen (intermediate)
Utilize both oxidative metabolism and anaerobic glycolysis to produce energy
Adapted for rapid contractions and short bursts of activity

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Type IIb

Fast, White Glycolytic Fibers
Fewer mitochondria and myoglobin, but LOTS of glycogen (pale color)
Derive energy primarily via anaerobic glycolysis
Adapted for rapid contractions, but fatigue quickly

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M line

In the middle.

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H band

No actin

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A Band

all of myosin

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I Band

no myosin

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Sarcomere

1/2 of I band X2, all of A band.

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Neuromuscular Junction (Motor End Plate)

A neuromuscular junction (motor end plate) is a chemical synapse between a motor (efferent) neuron and a skeletal muscle fiber (cell).
A motor unit is defined as the motor (efferent) neuron and all the muscle fibers (cells) it innervates.

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A skeletal muscle (i.e. the organ) contains

Skeletal Muscle Tissue
Vessels (arteries, capillaries, veins, lymph vessels)
Nerve Fibers
Connective Tissue

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Connective tissue sheaths associated with skeletal muscle (i.e. the organ):

Endomysium
Perimysium
Epimysium

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FA = fascia adherens

anchoring junction
links actin (thin) filaments

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D = desmosome

anchoring junction
links intermediate filaments

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N = gap junction

communicating junction
intracellular communication

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Muscle develops from

mesoderm

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Extensibility

Ability of tissue to be stretched or extended - passive process

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Contractility

Requires presence of ATP. refers to the capacity of muscle to contract or shorten forcefully

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Elasticity

is the ability of your muscles to extend in an activity and resume their contracted position. Optimize strong, safe, graceful movement by stretching to increase the elasticity of your muscles.

28

Skeletal muscles

Cells 10 to 100 microm in diameter. In terms of length, they could be a few mm long to 1+ m in length (sartorius).

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Intercalated discs

Cardiac muscle (this muscle only has 1 nucleus- found centrally). Where one cell connects to another. Specialized junctions help cells communicate and hold them together.

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Cardiac muscle cells

15 microm in diameter, 85 to 100 microm in length.

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Smooth muscle

Nuclei in the center - fusiform (wide in center, narrow at end). Cells are 20microm in length in blood vessels, can be upwards of 500 microm in a pregnant uterus.

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Corkscrew nucleus

If you fix smooth msucle in contracted state, the way that actin/myosin sets up causes it to twist – twisting the nucleus with it.

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Myofibril

Sarcomeres - build together to form myofibers.

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Actin length

1 microm in length, 8 nm in width. 1 end attaches into Z disc, while other end extends into A band.

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Z- disc

wall/edge of sarcomere.

36

Sliding filament hypothesis

Why contraction with shortening causes changes in sarcomere. Muscle contraction w/shortening occurs because rod-like myosin has globular heads. These have actin binding sites, and grab them to walk along them. This produces tension and potential shortening.

A band stays the same length - I band shrinks and disappears with full contraction. H zone goes away as well.

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each myosin interacts with

6 actin filaments. This is hexagonal in shape.

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Thick myofilament

central thick filament that is made up of myosin protein. Has tail of interwoven peptide chains, with two globular heads. Heads have binding sites for ATP and Actin, and ATPase activity.

39

Actin

G actin - polymerize to form f-actin (fibrous actin). What you see is that each thin filament has 2 f-actin chains. Each g-actin subunit has a myosin binding site.

40

Troponin complex

Has 3 subunits - found at regular intervals along each tropomyosin. TnT, TnC, TnI subunits. TnI inhibits, TnC where you have calcium being able to bind. TnT makes sure that troponin is stuck to tropomyosin.

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Calcium ions are

the final trigger for contraction. It signals for contraction, nerve signals this, T-tubules (extensions of sarcoplasmic reticulum in the cell) - transverse tubules - extensions of PM into cells, these fingerlike extensions in skeletal muscle come in twice at each sarcomere- at A/I band junctions. On either side of T-tubules, you have enlargements of Smooth ER called terminal* cisternae. Creates a triad- T-tubule, 2 terminal cisternae. When cell gets signal, action potential goes along membrane, down t-tubules, terminal cisternae, releases calcium.

**while this is happening, cell is "pulling" calcium back in**

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Acetocholine

Muscle nerve NT. Exocytosis releases these into cleft between axon terminal and motor neuron. Bind ligand gated channels, cause difference in voltage that causes action potential to begin.

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Topomyosin

blocks myosin binding. When calcium comes in binds to TnC, it moves tropomyosin away.

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Contraction cycle

Myosin has been waiting for Ca to show up. Once actin and myosin bind, myosin goes from high energy to low energy state. Creates tension, potentially movement. When ATP binds to myosin head, myosin lets go after ATP is hydrolyzed putting myosin back into the high energy state.

45

Rigor mortis

Calcium floods cytoplasm - one of the first things that happens - comes from outside of cell, or from sarcoplasmic reticulum breaking down a bit.

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Cardiac muscle- Diads

Diad (SR) at each Z disc - not as elaborate as in skeletal musle.

The diad is a structure in the cardiac myocyte located at the sarcomere Z-line. It is composed of a single T-tubule paired with a terminal cisterna of the sarcoplasmic reticulum.

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Smooth muscle -actin and mysoin

Thick and thin filaments obliquely go through cell. Attach into dense bodies on cell surface (help connect cell to cell), or can be located deep in the cell. When the cell contracts, it shortens and twists.