10 [chapter 10 muscular tissue]

CHAPTER 10
Muscular Tissue
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Principles of
Anatomy and
Physiology
14th Edition

The purpose of the chapter is to:
1. Learn about the structure and function of the 3
types of muscular tissue
2. Examine the events at the neuromuscular
junction
3. Describe energy use in muscle cells
4. Understand how muscle tension is controlled
Introduction

1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
3 Types of Muscular Tissue

3 Types of Muscle
Anatomy Overview:
 The Muscular System: Skeletal, Cardiac, and
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Three Types of Muscular Tissue
Location Function Appearance Control
Skeletal
[Insert skeletal muscle
image from Table 10.5, pg
321]
Cardiac
[Insert cardiac muscle
321]
Visceral
(smooth muscle)
[Insert smooth muscle
321]
skeleton
various
organs,
example:
GI tract
heart
move
bones
various
functions,
example:
peristalsis
pump
blood
multi-
nucleated &
striated
onenucleus&
no striations
onenucleus,
striated, &
intercalated
discs
voluntary
involuntary
involuntary

More About Skeletal Muscle Tissue

Muscle Tissue Components

How are Muscles Formed?

Microscopic Anatomy of a Muscle

Microscopic
Anatomy of
a Muscle

The Arrangement of a Sarcomere

Components of a Sarcomere

Muscle Proteins
Contractile
Myosin
Actin
Regulatory
Troponin
Tropomyosin
Structural
Titin
Nebulin
Alpha-actin
Myomesin
Dystrophin

 Myosin pulls on actin, causing the thin
filament to slide inward
 Consequently, Z discs move toward each
other and the sarcomere shortens
 Thanks to the structural proteins, there is
a transmission of force throughout the
entire muscle, resulting in whole muscle
contraction
The Sliding Filament Mechanism

Note the changes in the I band and H zone
as the muscle contracts
Sliding Filament Mechanism

The Contraction Cycle

The Contraction Cycle
Interactions Animation:
 Contraction of Skeletal Muscle Cells
The neuromuscular junction, parts of a muscle
fiber, and the contraction cycle

This concept connects the events of a muscle
action potential with the sliding filament
mechanism
Excitation-Contraction Coupling

The force of a
muscle contraction
depends on the
length of the
sarcomeres prior
to the contraction
Length-Tension Relationship

The events at the NMJ produce a muscle
action potential
 Voltage-gated calcium channels open resulting in
an influx of calcium. This causes exocytosis of
neurotransmitter (NT) into the synaptic cleft. NT
binds to ligand-gated Na+ channels on the motor
endplate which cause an influx of Na+ into the
muscle. This depolarizes it and results in Ca2+
release from the SR
 NT gets broken down
Without this series of events, muscle
contraction would not be possible
The Neuromuscular Junction (NMJ)

The Neuromuscular Junction

Events at the NMJ
 Neuromuscular Junctions

How do muscles derive the ATP necessary
to power the contraction cycle?
 Creatine phosphate
 Anaerobic glycolysis
 Cellular respiration
Muscle Metabolism

Production of ATP in Skeletal Muscle

Energy Sources and Fatigue
 Muscle Metabolism
Role of ATP in Muscle Movement and Fatigue

The inability to maintain force of contraction
after prolonged activity
Due to:
 Inadequate release of Ca2+ from SR
 Depletion of CP, oxygen, and nutrients
 Build up of lactic acid and ADP
 Insufficient release of ACh at NMJ
Muscle Fatigue

Why do you continue to breathe heavily for
a period of time after stopping exercise?
Oxygen debt
 Replenish CP stores
 Convert lactate into pyruvate
 Reload O2 onto myoglobin
Oxygen Consumption After Exercise

A motor unit consists of a somatic motor
neuron and the muscle fibers it innervates
 The strength of a contraction depends on how
many motor units are activated
Control of Muscle Tension

The brief contraction of all muscle fibers in a
motor unit in response to a single action
potential
 Latent period
 Contraction period
 Relaxation period
 Refractory period
Twitch Contraction

Wave summation occurs when a second
action potential triggers muscle contraction
before the first contraction has finished
 Results in a stronger contraction
Unfused tetanus
Fused tetanus
Frequency of Stimulation

Myograms

Motor units recruitment is the process in
which the number of active motor units
increases
 Weakest motor units are recruited first followed by
stronger motor units
 Motor units contract alternately to sustain
contractions for longer periods of time
Motor Unit Recruitment

Factors That Influence Tension
 Control of Muscle Tension

Even when at rest, a skeletal muscle
exhibits a small amount of tension, called
tone
 Due to weak, involuntary contraction of motor
units
Muscle Tone

Isotonic – tension is constant while muscle
length changes
 Concentric
 Eccentric
Isometric – muscle contracts but does not
change length
Isotonic vs. Isometric Contractions

Isotonic vs. Isometric Contractions

 Slow oxidative
 Fast oxidative glycolytic
 Fast glycolytic
Skeletal Muscle Fiber Types

 Stretching
 Strength Training
Exercise and Skeletal Muscle Tissue

Cardiac muscle has the same arrangement
as skeletal muscle, but also has intercalated
discs
Cardiac Muscle

 Smooth muscle contractions start more
slowly and last longer than skeletal and
cardiac muscle contractions
 Smooth muscle can shorten and stretch to
a greater extent
Smooth Muscle

Smooth Muscle

Mature skeletal muscle fibers cannot
undergo mitosis
 Hypertrophy
 Hyperplasia
 Smooth muscle and pericytes
Regeneration of Muscle Tissue

Development
of Muscle

Between 30–50 years of age, about 10% of
our muscle tissue is replaced by fibrous
connective tissue and adipose tissue.
Between 50–80 years of age another 40%
of our muscle tissue is replaced.
Consequences are:
 Muscle strength and flexibility decreases
 Reflexes slow
 Slow oxidative fiber numbers increase
Aging and Muscle Tissue

Copyright 2014 John Wiley & Sons, Inc.
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programs or from the use of the information herein.
End of Chapter 10

10 [chapter 10 muscular tissue]

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