Human Muscular
System
SVHS Adv, Biology Biology
Unit #6
2011-12
Normal
or
Not???
Muscular
System
• Study of muscle
is known as
myology.
• 40-50% of body
weight is muscle.
Tortora pages 154
Muscle
Tissue Types
• Smooth
– Involved in
internal
processes.
– Makes up the
walls of
hollow
internal
structures.
– Involuntary
Tortora pages 154
Muscle
Tissue Types
• Cardiac
– Forms wall
of the heart
and major
vessels
leading from
the heart
Tortora pages 154
Muscle
Tissue Types
• Skeletal
– Attached to
skeleton.
– Responsible
for skeletal
movement.
Tortora pages 154
Functions of
Muscle Tissue
• Producing body movement
• Movement of substances
in body.
• Stabilizing body position.
• Regulating organ volume.
• Heat production.
Tortora pages 154
Striated Muscle
Connective Tissue.
• Connective tissues
– Superficial facia
• Contains fat and is just
below the skin.
– Deep facia
• Connective tissue
• Holds muscles together.
• Separates muscle
bundles
• Extends to form
tendons
Tortora pages 154-155
Striated Muscle
Connective Tissue.
• The entire muscle
is wrapped in the
epimysium
Tortora pages 154-155
Striated Muscle
Connective Tissue.
• Muscle bundles
fasicles are
surrounded by
facia called
perimysium
Tortora pages 154-155
Striated Muscle
Connective Tissue.
• Each muscle fiber
(cell) is covered by
facia called
endomysium.
Tortora pages 154-155
Striated Muscle
• Blood supply
– Muscle contraction
requires large
amounts of energy
and so requires
large amounts of
nutrients and
oxygen.
Tortora pages 154-155
Striated Muscle
Nervous Tissue
Nerve tissue
• Motor neuron
– Motor units
• Muscle must receive
a stimulus in order
to contract.
• Role of muscle
action potential.
Tortora pages 154-155
Homework Quiz - Activity A
1- T or F
Smooth muscle is voluntary and found in the
walls of blood vessels.
2- T or F Cardiac muscle is not under conscious control.
3- T or F Striated muscle is voluntary and is also called
skeletal muscle.
4- Which of the following is not a function of the
muscular system?
– A) Creating motion
– B) Moving substances in the in the body.
– C) Creating body heat.
– D) Sustaining the body’s posture.
– E) Producing hormones for growth.
5- Which of the following is not a characteristic of
muscle tissue?
A) Ability to return to it’s original shape.
B) Ability to respond to a stimuli.
C) Ability to push bones to create movement.
D) Ability to shorten.
E) Ability to stretch.
6- The ability of muscle to stretch is referred to as ?
7- Muscle making up the wall of the heart is known as ?
8- Muscle making up the walls of the intestine is known
as ?
Answers
1) True
2) True
3) True
4) E (producing hormones for growth)
5) C (ability to push bones)
6) Extensibility (ability to stretch)
7) Cardiac
(makes up wall of heart)
8) Smooth (makes up wall of intestines)
Muscles + Bones =
Lever Systems
• Class I lever
– fulcrum between
resistance and
energy.
• Class II lever
– Resistance between
energy and fulcrum.
• Class III lever
• Energy is between
fulcrum and resistance.
Skeletal Muscle
Structure
Each muscle
fiber or cell
is composed
of subunits
called
myofibrils
Tortora pages 156
Striated Muscle
Structure
• Structure of
striated muscle cell.
– Sarcolemma
– Sarcoplasm
– Sarcoplasmic
reticulum
– Transverse
tubules
Tortora pages 156-157
Striated Muscle
Structure
• Proteins of muscle are
called myofilaments.
– Thin protein filament
is composed of:
• Actin
• Tropomyosin.
– Thick protein
myofilament is
myosin.
• Myosin has cross
bridges.
Tortora pages 156
Striated Muscle
Structure
• Actin
– Contains myosin binding
site.
– Site is covered by
tropomyosin.
• Myosin
– Contains actin binding
site.
– Contains a binding site
for ATP.
Tortora pages 156
Striated Muscle Structure
• Sarcomeres are
contracting units in
muscle.
• Each fiber has many
myofibrils.
• Each myofibril is
composed of many
sarcomeres.
–
–
–
–
Z lines
A band
I band
H zone
Tortora pages 156
Tortora pages 156
C & D Quiz
1.
2.
3.
4.
5.
6.
7.
Which lever type is a distance multiplier?
Which lever type has the force exerting between
the fulcrum and the load?
A muscle that decreases the angle of a joint.
A muscle that moves a bone away from the midline
of the body.
A muscle that decreases the size of an opening.
A muscle that produces a downward movement.
A muscle that turns the palm downward or
posteriorly.
• Motor units
– Motor neuron
– Muscle cell
– 10-500 fibers
per motor
neuron.
•Neuromuscular
junctions
Striated Muscle
Structure
–Motor end plate.
–Synaptic cleft.
–Sarcolemma
• Starting a muscle
contraction.
1) Nerve impulse
reaches axon
terminal.
2) Ca++ enters the
synaptic end bulb.
3) Vesicles move to and
fuse with membrane.
4) Vesicle releases ACH
into the synaptic
cleft.
Neuromuscular
Junctions
•
•
•
•
5) ACH diffuses
across cleft and binds
to ACH receptors in
sarcolemma.
6) Muscle action
potential is created.
7) Within 1/500 of a
second ACHe
inactivates ACH.
8) Muscle prepares
for next muscle
action potential.
Neuromuscular
Junctions
• Muscle action
potential spreads
across
sarcolemma.
– Reaches into the
transverse
tubules.
– Spreads to the
sarcoplasmic
reticulum.
– Sarcoplasmic
reticulum releases
Ca++
Physiology of
Contraction
Physiology of Contraction
• Calcium binds to
tropomyosin,
changing its shape.
• Myosin and actin
bind.
• ATP is broken down
to ADP .
• Powerstroke
occurs.
• Two changes cause
relaxation.
– ACh broken down by
Ache.
– Results in no muscle
action potential.
– Ca++ is rapidly removed
from the sarcoplasm.
– Results in tropomyosin
covering the myosin
binding sites on the
actin.
Striated Muscle
& Relaxation
Striated Muscle
& and Energy
• ATP is needed as
energy source for
muscle contraction.
• ATP attaches to ATP
binding site on myosin
head.
• ATP is broken down to
ADP + P.
• Myosin cross bridge is
energized.
Tortora
Pages 160, 162-163
Striated Muscle
& and Energy
• Ca++ removes tropomyosin.
• Actin & myosin engage.
• Cross bridge changes
shape. (Powerstroke)
• ADP is released.
• ATP again attaches to
binding site causing actin &
myosin to disengage.
• ATP is broken down causing
myosin head to return to
normal position.
• Powerstroke repeated.
Tortora
Pages 160, 162-163
Energy for Muscle
Contraction
• Contraction is
powered initially by
ATP stored in the
muscle.
• 5 second supply.
• 40 yards into
400 meter race.
Tortora
Pages 160, 162-163
Energy for Muscle
Contraction
• Creatine Phosphate
– Energy is released
from CP.
– Used to make more
ATP from ADP and
Pi.
– Supplies 15 seconds
worth of energy.
– 22 seconds or 220
yards into race.
Tortora
Pages 160, 162-163
Energy for Muscle
Contraction
• Glycolysis
– Glucose is broken down to pyruvic
acid.
– Occurs in sarcoplasm.
– Anaerobic (does not require oxygen)
– Results in lactic acid if no oxygen
available.
– Lactic acid causes fatigue feeling.
– Provides 30 seconds worth of
muscle contraction.
– You are now 300 yards into race.
Tortora
Pages 160, 162-163
Energy for Muscle
Contraction
• Aerobic respiration.
–
–
–
–
Occurs in mitochondria.
Breaks down pyruvic acid.
Requires oxygen.
Results in H2O and CO2 as
wastes.
– Makes 36 ATP molecules.
– Now you can run a
marathon!!
Tortora
Pages 160, 162-163
Energy for Muscle
Contraction
• Greg LeMond’s
career ended
due to a
mitochondrial
condition.
• What is he doing
today?
Tortora
Pages 160, 162-163
Still Racing!!
Tortora
Pages 160, 162-163
Oxygen Debt
• Occurs when oxygen
does not get to
muscles.
• Glycolysis results in
L.A.
• Must acquire oxygen
to pay back debt.
• Heavy breathing
after exercise!
Tortora
Pages 160, 162-163
All-or-None
Principle
• Any given motor unit will be
fully contracted or not at
all.
• Threshold stimulus causes
contraction.
• Subthreshold will not
create a contraction.
• Some motor units are
contracted while others
are not.
Tortora
Page 163-164
Homeostasis
• Oxygen Debt
– Due to lactic acid.
– Paid back with oxygen.
• Muscle Fatigue
– Due to L.A.
– Decrease in pH.
• Heat production
– 85% of energy is
released in form of
heat.
Tortora
Page 164
Types of Contraction
• Different types of
contractions
depending on how
often stimulation
occurs.
• A muscle twitch is a
brief contraction of
all muscle fibers in
a motor unit due to
a single nerve
impulse.
Tortora
Page 164
Types of Contraction
• Phases of a
muscle twitch
– Latent phase
• Action
potential
spreads across
sarcolemma
• Ca++ released.
Tortora
Page 164
Types of Contraction
• Contraction
phase
– Power
stroke.
– Actin and
myosin slide
over one
another.
– Muscle
becomes
shorter.
Tortora
Page 164
Types of
Contraction
• Relaxation phase
– Actin & Myosin
disengage.
– Ca++ is actively
pumped back into
the sarcoplasmic
reticulum.
Tortora
Page 164
Types of
Contraction
• Refactory phase
• Sarcolemma
not responsive
to a stimulus
Tortora
Page 164
Types of Contraction
• Wave Summation
– Successive
stimuli prior to
completion of
relaxation phase.
– Each contraction
is stronger than
the previous
Tortora
Page 164
Types of
Contraction
• Incomplete Tetanus
– 20 to 30 stimuli per
second.
– Partial relaxation
• Complete Tetanus
– 80-100 stimuli per
seconds.
– No relaxation.
Tortora
Page 164
Types of
Contraction
• Isotonic
– Contraction and
movement
• Isometric
– Contraction
without
movement
Tortora
Page 164
Skeletal Muscle Tissue
Characteristics
• Muscle tone.
• A muscle in partial
contraction.
• A few fibers are
contracting at all
times.
(recruitment)
Skeletal Muscle Tissue
Characteristics
• Muscular Atrophy
– Don’t use it and you
lose it!
• Muscular
Hypertrophy
• Muscle getting
bigger due to
work?
Thursday 12/4
Page 163-164
Cardiac Muscle Tissue
Characteristics
Cardiac Muscle Tissue
Characteristics
Smooth Muscle Tissue
Characteristics
How Skeletal Muscles Produce
Movement
• Origin
• Insertion
How Skeletal Muscles Produce
Movement
• Group actions
–
–
–
–
Prime mover
Antago
Synergists
fixators
Naming Muscles
• Direction of Muscle
fibers
Naming Muscles (cont)
• Location
Naming Muscles (cont)
• Number of origins
Naming Muscles (cont)
• Shape
Naming Muscles (cont)
• Origin and insertion
Naming Muscles (cont)
• Action
Naming Muscles (cont)
• Size
Tortora pages 154
4 Characteristics of Muscle Tissue
• Excitability:
– Ability of tissue to receive and respond to
stimuli.
• Contractility:
– Ability to shorten and thicken.
• Extensibility
– Ability of muscle tissue to stretch.
• Elasticity
– Ability of muscle tissue to return to its
original shape after contraction or extension.