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Muscles and Muscle Tissue
Functions, gross and microscopic structure with pictures
80
Anatomy
Undergraduate 2
03/28/2007

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Term
Three types of muscles tissue are:
Definition
skeletal, cardiac, and smooth
Term
Muscle Fibers
Definition
Skeletal and smooth muscle cells
Term
Actin and myosin
Definition
Two kinds of myofilaments that muscle contraction depends on
Term
Sarcolemma
Definition
Muscle plasma membrane
Term
Sarcoplasm
Definition
Cytoplasm of a muscle cell
Term
Myo, mys, and sarco
Definition
Prefixes that all refer to muscle
Term
Skeletal muscles are responsible for:
Definition
...all locomotion
Term
Cardiac muscle is responsible for:
Definition
...coursing the blood through the body
Term
Smooth muscle helps maintain:
Definition
...blood pressure, and squeezes or propels substances (i.e. food, feces) through organs
Term
Excitability or irritability
Definition
The ability to recieve and respond to stimuli
Term
Contactililty
Definition
The ability to shorten forcibly
Term
Extensiblity
Definition
The ability to be stretched or extended
Term
Elasticity
Definition
The ability to recoil and resume the original resting length
Term
Endomysium
Definition
Fine sheath of connective tissue composed of reticular fibers surrounding each muscle fiber. [image]
Term
Perimysium
Definition
Fibrous connective tissue that surrounds groups of muscle fibers called fascicles [image]
Term
Epimysium
Definition
An overcoat of dense regular connective tissue that surrounds the entire muscle [image]
Term
Skeletal Muscle
Definition
Elongated cell Multiple peripheral nuclei Visible striations Voluntary [image]
Term
Cardiac Muscle
Definition
Branching cell Single central nucleus Visible striations Involuntary [image]
Term
Smooth Muscle
Definition
Spindle-shaped cell Single central nucleus Lack visible striations Involuntary [image]
Term
Thick filaments (myosin)
Definition
Extend the entire length of an A band [image]
Term
Thin filaments (actin)
Definition
Extend across the I band and partway into the A band [image]
Term
Z-disc
Definition
coin shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another [image]
Term
Desmin
Definition
A protein present in M lines that makes them appear darker
Term
Myosin
Definition
Protein that makes up a thick filament. Each myosin molecuole has a rod-like tail and two globular heads [image]
Term
Actin
Definition
Protein that makes up thin filaments. Each actin molecule is a helical polymer of globular subunits called G actin. The subunits contain the active sites to which myosin heads attach during contraction [image]
Term
Tropomyosin and troponin
Definition
Proteins bound to actin that regulate the interaction of actin and myosin.
Term
Sarcoplasmic Reticulum (SR)
Definition
The endoplasmic reticulum of the muscle cell; its interconnecting tubules surround each myofibril [image]
Term
Terminal Cisterna
Definition
Sac like regions of the sarcolplasmic reticulum that serve as specialized resevoirs for calcium ions.[image]
Term
T Tubules
Definition
Elongated tubes that penetrate into the cell's interior where the A band and I band meet up. Associated with the paired terminal cisternae to form triads. Conduct impulses to the deepest regions of the muscle. These impusles signal for the relase of calcium ions from adajacent terminal cisternae. [image]
Term
Triad
Definition
3 unit group consisting of one T tubule lying between two adjacent terminal cisternae. [image]
Term
Sarcomere
Definition
The contractile unit of muslce that extends from one Z line to the next. Includes the entire A band and half of the I band (to the Z line) on each side of the A band. [image]
Term
Fascicle
Definition
A bundle of muscle cells (fibers) bound together by connective tissue to form a functional unit [image]
Term
In order to contract a skeletal muscle must:
Definition
Be stimulated by a nerve ending

Propagate an electrical current, or action potential, along its sarcolemma

Have a rise in intracellular calcium ion levels, the final trigger for contraction
Term
Cytosol
Definition
The intracellular fluid in which the organelles are suspended
Term
Mitochondrion
Definition
The cytoplasmic organelle that is the site of ATP synthesis; referred to as the "powerhouse" of the cell[image]
Term
Myofibril
Definition
A cylindrical bundle of contractile filaments within the skeletal muscle cell[image]
Term
Nucleus
Definition
The cellular structure that contains the genetic material of the cell[image]
Term
Whole muscle is surrounded by what connective tissue?
Definition
Epimysium[image]
Term
A fascicle is surrounded by what connective tissue?
Definition
Perimysium[image]
Term
A muscle cell (fiber) is surrounded by what connective tissue?
Definition
Endomysium[image]
Term
Resting Membrane Potential
Definition
The voltage that exists across a cell's plasma membrane when the cell is at rest (not conducting an impulse); cell interior is relatively more negative than the cell exterior. The resting membrane potential is measured in millivolts.
Term
Action Potential
Definition
An electrical signal consisting of the depolarization and subsequent repolarization of a nerve or muscle cell membrane.

Travels along the membrane and functions as a signal to initiate an activity (i.e. a muscle contraction)
Term
Depolarization
Definition
A decrease in the negative resting membrane potential (the voltage that exists across the plasma membrane)
Term
Motor neuron
Definition
A single nerve cell that extends from the brain or spinal cord to a muscle or gland
Term
Neuromuscular Junction
Definition
The place where a motor neuron stimulates a muscle cell. The muscle cell and motor neuron do not actually touch, but are separated by the synaptic cleft [image]
Term
Axon Terminal
Definition
The swollen distal end of an axon.

Contains a neurotransmitter substance within synaptic vesicles
Term
Synaptic Vesicles
Definition
Membranous organelles containing neurotransmitter substances.

Found within the axon terminals of neurons
Term
Acetylcholine
Definition
The neurotransmitter released by a motor neuron at the neoromuscular junction; one of the principal neurotransmitters of the peripheral nervous system
Term
Synaptic Cleft
Definition
The space between the axon terminal and the membrane of the target cell.
Term
Neurotransmitter
Definition
Molecules released from synaptic vesciles in neuron axon terminals

Bind to receptor sites on target cells stimulating or inhibiting them
Term
Exocytosis
Definition
The bulk transport of material out of the cell by first fusing a membrane-bound vesicle with the plasma membrane. When the membrane ruptures, the contents of the vesicle are released into the extracellular space.
Term
Propagate
Definition
The process of reproducing and spreading the action potential along the sarcolemma and down the T tubules
Term
Polarized
Definition
A condition in which a difference in electrical charge exists across a cell membrane
Term
Calcium Ions
Definition
Calcium atoms with two positive charges; concentrated in the extracellular fluid and terminal cisternae, but enter then cytosol where they play an important role in many processes such as muscle contraction and the release of neurotransmitters.
Term
Voltage-regulated calcium channels
Definition
Integral proteins in cell membranes that respond to changes in membrane voltage by changing shape, which opens or closes calcium-specific channels in the proteins. When the channels are open, calcium ions move from one side of the membrane to the other.
Term
Receptor Site
Definition
A specific region on a protein to which another molecule become attracted and attaches. Also called a binding site
Term
Chemically regulated ion channels
Definition
Integral proteins in cell membranes that serve as ion channels. When a specific chemical binds to the receptor site on the protein, the protein changes shape, opens the channel and allows certain ions to move from one of the membrane to the other.
Term
Acetylcholinesterase
Definition
An enzyme located in the synaptic cleft that rapidly degrades the neurotransmitter acetylcholine. In muscle cells, the immediate breakdown of acetylcholine prevents repetitive stimulation of the motor end plate in the absence of action potentials.
Term
Refractory Period
Definition
The period immediately following the transmission of an impulse in a muscle, in which a neuron or muscle cell regains its ability to transmit another impulse
Term
Contraction
Definition
Refers to the activation of myosin's cross bridges (force generating sites)
Term
Shortening
Definition
Occurs when the tension generated by the cross bridges exceeds forces opposing shortening
Term
Contraction ends when...
Definition
cross bridges become inactive, the tension generated declines, and relaxtion is induced.
Term
The 2 Types of Muscle Contractions Are:
Definition
Isometric and Isotonic contraction
Term
Isometric Contraction
Definition
Increasing muscle tension (muscle does not shorten during contraction)
Term
Isotonic Contraction
Definition
Decreasing muscle length (muscle shortens during contraction)
Term
Motor Unit
Definition
A motor unit and all of the muscle cells it stimulates [image]
Term
Recruitment
Definition
The stimulation of additional motor units to increase strength of contraction
Term
Interneuron
Definition
A neuron within the brain or spinal cord that lies between sensory and motor neurons. Also called an association neuron.
Term
What is the advantage of having only a few muscle cells per motor unit?
Definition
Generates precise movements
Term
Small motor units
Definition
Contain few muscles and are found where precise movements are needed. Like in the muscles of the eye.
Term
Large motor units
Definition
Contain large muscles that exhibit gross movements, such as movements of the thigh, in which a single neuron is connected to a larger number of muscle cells.
Term
Muscle Tone
Definition
The nearly constant state of low-level tension and resistance to stretch in a muscle
Term
Muscle tone minute contractions are maintained by...
Definition
activities of the spinal cord and result in a firmness of the muscle
Term
If a muscles motor nerve is cut or damaged...
Definition
The muscle loses all tone and will become flaccid (soft and limp; not firm)
Term
4 Unique Characteristics Of Smooth Muscle
Definition
1. Smooth muscle tone, 2. slow prolonged contractile activity, 3. Low energy requirements, 4. Response to stretch
Term
White Muscle Fibers
Definition
Fast twitch, fatigue prone fibers. Light in color due to reduced myoglobin. Found in sprinters.
Term
Red Muscle Fibers
Definition
Slow twitch oxidative, fatigue resistant fibers. Red due to myoglobin. Found in long distance runners.
Term
Three factors that affect muscle tension:
Definition
1. Frequency of stimulation, 2. Number of motor units recruited, 3. Degree of muscle stretch
Term
Muscle Twitch
Definition
A single, rapid contraction in response to a stimulus.
Term
A complete muscle twitch is divided into three phases:
Definition
1. Latent period, 2. Contraction, 3. Relaxation
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