Essay on Muscular System Pp2

Muscular System

1

The Muscular System
 Muscles are responsible for all types of body movement
 Three basic muscle types are found in the body
 Skeletal muscle
 Cardiac muscle
 Smooth muscle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2

Characteristics of Muscles
 Muscle cells are elongated
(muscle cell = muscle fiber)
 Contraction of muscles is due to the movement of microfilaments
 All muscles share some terminology
 Prefix myo refers to muscle
 Prefix mys refers to muscle
 Prefix sarco refers to flesh
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3

Skeletal Muscle

striated, voluntary
 Multi-nucleated – fibers in bundles
 1-40 mm long, 10-100 microns thick
 42% of male body weight, 36% in females
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General
 1.

sarcoplasm – cytoplasm of muscle fibers
 2. sarcolemma – plasma membrane covering the muscle fibers
 3. location – any muscle attached to bones as well as in the tongue, the pharynx, and certain muscles of the eye
 4. functions – locomotion, posture, transport of blood and lymph, and heat production (85% of the body’s heat)
4

Cardiac Muscle

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heart muscle, involuntary branched fibers & striated

Similar to skeletal muscles
 Involuntary control
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purkinje fiber (conduction myofiber)
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Stimulate actual contraction of the ventricles

innervation – autonomic nervous system
Functions
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Move blood through the heart and through the vessels 5

Smooth Muscle
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Involuntary – maintenance of the body’s internal environment Nonstriated
Spindle shaped
15-500 microns long contractions are slow
Location – in the walls of internal organs such as digestive organs, trachea, gall bladder, blood vessels, urinary and genital ducts, and the iris of the eye Functions – propulsion,expulsion, regulation of openings, and regulation the diameter of tubes / blood vessels
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Characteristics of Muscle Tissue
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Excitability – ability to receive and respond to stimuli 

Contractility – ability to shorten and thicken

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Extensibility – ability to stretch

Elasticity – ability to return to the original shape 

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Skeletal Muscle Tissue

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Connective tissue components
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Fascia – sheet or broad band of fibrous connective tissue superficial – under the skin
 deep – holds the muscles together thus forming functional groups
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Epimysium – fibrous connective tissue surrounding an entire muscle
 Perimysium – covers a bundle of fibers called fascicles  Endomysium – surrounds each muscle fiber
 Aponeurosis – the tendon that extends as a broad, flat layer around the skull or as a part of the abs – figure
7-14
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Connective Tissue Wrappings of
Skeletal Muscle
 Endomysium – around single muscle fiber
 Perimysium – around a fascicle (bundle) of fibers Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 6.1

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Connective Tissue Wrappings of
Skeletal Muscle
 Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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Nerve and Blood supply
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MUST HAVE:
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Action Potential – the electric current stimulation necessary for contraction

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Nerve impulse – causes the stimulation

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Muscle action potential – the result

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Blood to bring nutrients and oxygen, as well as to carry wastes
 Generally

there is one artery along with 1 or 2 veins to accompany each nerve

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Structure – Skeletal Muscle Fibers
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Sarcolemma – coverings
Sarcoplasm – “stuff” inside – many nucleii, and mitochondria Sarcoplasmic reticullum – network of tubules similar to E.R.
Transverse tubules – Perpendicular to the S.R. – open to exterior of the muscle fiber
Myoglobin – reddish pigment similar to hemoglobin that carries 02

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Fibers - continued
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Myofibrils – Cylindrical structures that run longitudinally through the fibers and contain: thin myofilaments – Made mostly

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