The Muscular System

ELAINE N. MARIEB

EIGHTH EDITION

6

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University

ESSENTIALSOF HUMAN

ANATOMY& PHYSIOLOGY

PART AThe Muscular System


The Muscular System

Muscles are responsible for all types of body movement

Three basic muscle types found in the body Skeletal muscle Cardiac muscle Smooth muscle


Skeletal Muscle Location:

Attaches to bones or skin (face muscles) Cell Shape and Appearance:

Multinucleated (many nuclei per cell) Striations (stripes) Single long cylindrical cells

Regulation of Contraction: Voluntary Nervous System control

Contraction Speed: Slow to fast

Rhythmic contraction: No


Cardiac Muscle Location:

Walls of heart Cell Shape and Appearance:

Branching chains of cells Striated Uninucleate (1 nucleus per cell)

Regulation of Contraction: Involuntary; has pacemaker Nervous System control Hormonal control (ex: ANP)

Contraction Speed: Slow

Rhythmic contraction: Yes (“lub dub”)


Smooth Muscle Location:

Wall of visceral organs (not the heart) Ex: stomach, intestines, esophagus, rectum

Cell Shape and Appearance: Single cells No Striations Fusiform (wide in middle; tapered at ends) Uninucleate (1 nucleus per cell)

Regulation of Contraction: Involuntary Nervous System control Hormonal control

Contraction Speed: Slow

Rhythmic contraction: Yes (in some)


Characteristics of Muscles Muscle cells are elongated

(muscle cell = muscle fiber) Contraction of muscles is due to the movement

(sliding) of microfilaments Micro = small

All muscles share some terminology Prefix my(o)- refers to muscle ex. myosin Prefix mys- refers to muscle

ex. epimysium Prefix sarc(o)- refers to flesh

ex. sarcomere sarcophagus phag(o) = eat


Connective Tissue Wrappings of Skeletal Muscle

Endomysium around single muscle

fiber Perimysium

around a fascicle (bundle) of fibers

Epimysium covers the entire skeletal muscle

Figure 6.1


Skeletal Muscle Attachments Epimysium blends into a connective

tissue attachment Tendon – cord-like structure Aponeuroses – sheet-like

structure Sites of muscle attachment

Bones Cartilages Connective tissue coverings


Function of Muscles

Produce movement Maintain posture Stabilize joints Generate heat


Microscopic Anatomy of Skeletal Muscle Cells are multinucleate Nuclei are just beneath the sarcolemma

Figure 6.3a


Microscopic Anatomy of Skeletal Muscle

Sarcolemma specialized plasma membrane

Sarcoplasmic reticulum specialized smooth endoplasmic reticulum

Figure 6.3a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 6.3b

Microscopic Anatomy of Skeletal Muscle Myofibril

Bundles of myofilaments

Myofibrils are aligned to give distinct bands I band = light band A band = dark band



Sarcomere Contractile unit of a muscle fiber

Figure 6.3b


Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere

Thick filaments = myosin filaments Composed of the protein myosin Has ATPase enzymes

Figure 6.3c



Organization of the sarcomere Thin filaments = actin filaments

Composed of the protein actin

Figure 6.3c


Microscopic Anatomy of Skeletal Muscle Myosin filaments have heads (extensions or cross bridges) Myosin and Actin overlap

Figure 6.3d


Microscopic Anatomy of Skeletal Muscle At rest, there is a bare zone that lacks actin filaments

Sarcoplasmic Reticulum (SR) stores calcium

Figure 6.3d


Properties of Skeletal Muscle Activity

Irritability ability to receive and respond to a

stimulus

Contractility ability to shorten when an

adequate stimulus is received


Nerve Stimulus to Muscles

Skeletal muscles must be stimulated by a nerve to contract

Motor unit One neuron Muscle cells

stimulated by that neuron

Figure 6.4a



Neuromuscular junctions = association site of nerve and muscle

Figure 6.5b



Synaptic cleft – gap between nerve and muscle

Nerve and muscle do not make contact Area between nerve and muscle is filled with interstitial

fluid

Figure 6.5b


Transmission of Nerve Impulse to Muscle

Neurotransmitter = Chemical released by nerve upon

arrival of nerve impulse

Skeletal muscle neurotransmitter = Acetylcholine


Transmission of Nerve Impulse to Muscle

1. Neurotransmitter attaches to receptors on the Sarcolemma

2. Sarcolemma becomes permeable to sodium (Na+)

3. Sodium rushing into the cell generates an Action Potential

4. Once started, muscle contraction cannot be stopped


The Sliding Filament Theory of Muscle Contraction

Activation by nerve causes myosin heads (cross-bridges) to attach to binding sites on the thin filament

Myosin heads then bind to the next site of the thin filament

Figure 6.7


The Sliding Filament Theory of Muscle Contraction

This continued action causes a sliding of the myosin along the actin

The result is that the muscle is shortened (contracted)

Figure 6.7

The Muscular System

Documents

pearson education

slowrhythmic contraction

cellregulation of contraction

fastrhythmic contraction

single muscle fiberperimysium

basic muscle types

entire skeletal muscle

elongated muscle cell