Muscular System
Mrs. Yanac
Big Picture
• Responsible for allowing us to move.
• Muscles make up quite a large part of the
body & make up more than one-third of our
body mass.
• Muscles are able to contract and relax which
allows the body to move and performs all
bodily actions.
• Muscles provide the force that push
substances such as food through the body.
Key Terms
• Muscular System: The organ system that includes
all the muscles of the body.
• Muscle Fiber: A muscle cell.
• Tendon: Tough connective tissues which attach
skeletal muscles to the skeleton.
• Myofibrils: Bundles of threadlike structures that
are found in muscle fiber.
• Sarcomere: Basic functional unit of the muscle.
• Sliding Filament Theory: Theory explaining how
muscle fibers contract.
Muscle System Functions
• Provides voluntary
movement of body
– Enables breathing,
blinking, and smiling
– Allows you to hop, skip,
jump, or do push-ups
• Maintains posture
• Produces heat
Functions cont’d
• Causes heart beat
• Directs circulation of
blood
– Regulates
blood
pressure
– Sends blood to
different areas of
the body
Functions cont’d
• Provides movement of
internal organs
– Moves food through digestive
tract
– Enables bladder control
• Causes involuntary actions
– Reflex actions
– Adjusts opening of pupils
– Causes hair to stand on
end
Types of Muscles
• Skeletal Muscle: Muscle tissue that is attached
to bone.
• Cardiac Muscle: Muscle that is found only in
the walls of the heart.
• Smooth Muscle: Muscle tissue in the walls of
internal organs such as the stomach.
Muscle Tissue Characteristics
• Is made up of contractile
fibers
• Provides movement
• Controlled by the nervous
system
– Voluntary- consciously
controlled
– Involuntary- not under
conscious control
• Examples
– Skeletal
– Smooth
– Cardiac
Skeletal
Smooth
Cardiac
Types of Muscle Tissue
• There are three
main types of
muscle tissue
– Skeletal
(striated)
– Cardiac
(heart)
– Smooth
(visceral)
Muscle Contraction
• Muscles can only contract and relax
• Voluntary (under conscious control – such as
flexing your bicep) – controlled by the somatic
nervous system
• Involuntary (not under conscious control –
such as a heart beat) - controlled by the
autonomic nervous system
Comparison of Muscle Types
Muscle Type
Skeletal
Cardiac
Smooth
Attached to bone Heart
Walls of internal
organs + in skin
Function
Movement of
bone
Beating of heart
Movement of
internal organs
Control Mode
Voluntary
Involuntary
Involuntary
Long + slender
Branching
Spindle shape
Location
Shape
Striated- light and Striated
Characteristics dark bands
One or two nuclei
Many nuclei
Non-striated
One nucleus
(visceral)
Skeletal Muscles
Characteristics:
• Striated (striped) because muscle fibers are
arranged in bundles
• Allow the body to move
• Contracts in short, strong bursts
Contractions:
• Voluntary
Location:
• Attached to bones
Smooth Muscle
Characteristics:
• Not striated - muscle fibers are arranged in sheets
• Move food and other substances through the body
• Helps organs carry out their functions
• Contracts slowly but steadily
Contractions:
• Involuntary
Location:
• Lines inside of hollow organs (stomach, intestines, etc),
iris of eyes, blood vessels, reproductive tracts, bladder
Cardiac Muscles
Characteristics:
• Striated
• Responsible for heartbeats
• Contain lots of mitochondria to provide ATP
• Electrical impulses are sent so that all muscle
fibers contract at the same time
Contractions:
• Involuntary
Location:
• Only in the heart
Facts
• There are 639 skeletal muscles in the human body that
vary in size.
• Tendons connect skeletal muscles to bones
• Many skeletal muscles are attached to the ends of
bones on opposite sides of a joint
• Bone moves when muscles contract
• Skeletal muscles work in pairs. When one muscle
contracts to bend a joint, the other muscle needs to
contract in order to straighten the joint.
• Exercise is needed to maintain big, strong muscles
(atrophy) use ‘em or lose ‘em.
M
u
s
c
l
e
•
T
I
s
s
u
e
Muscles are made up of bundles
of muscle fibers, called fascicles
– Fascicle is a bundle of muscle
fibers
• A muscle fiber is a muscle
cell….made up of many small
myofibrils
– Myofibrils
contain filaments
» Two types of
protein
filaments
A
n
a
t
o
m
y
Filaments
Muscle Fibers
Myofibrils
Muscle
Fascicle
Muscle Tissue
Anatomy
1. Muscle
2. Fascicle
(bundle of fibers)
3. Muscle fiber
(muscle cell)
4. Myofibrils
1D
2C
3B
A
4
Muscle Contraction
• Muscles are made up of muscle fibers, which each contain
hundred of myofibrils.
• Myofibrils are made up of repeating sections of
sarcomeres.
• Sacromeres are what gives the striated appearance to
muscles.
• Each sarcomere contains two protein filaments: actin and
myosin.
• Actin filaments are anchored to structures called Z lines.
The region between two Z lines is the sacromere.
• Myosin filaments overlap the actin filaments. They have
tiny structures called cross bridges that attach to the actin
filaments.
Sliding Filament Theory
• Explains how actin and myosin interact to
contract muscle fibers:
• Myosin slides along actin, pulling the actin
filaments and Z lines together and shortening
the sacromere
• ATP is required to fuel this process
Mechanics of a Muscle Contraction
• Where does stimulation occur?
– Neuromuscular junction
• How do motor neurons
communicate with
muscle cells?
– Neurotransmitters (typically
acetylcholine) carry
impulse signal across the gap
• What happens when a
muscle cell is stimulated?
– Calcium ions are released into the muscle cell
Myofibrils are
surrounded by
calciumcontaining
sarcoplasmic
reticulum.
Neurotransmitters
Mechanics of a Muscle Contraction
• When each sarcomere becomes shorter it causes
each myofibril to become shorter.
• When each
myofibril becomes
shorter it causes
the muscle fibers
to become shorter
• When each
muscle fiber
shortens the
Sarcomere
overall muscle
contracts.
Control of a Muscle Contraction
• How long does a muscle cell
remain contracted?
– Until the release of acetylcholine
stops.
• How strongly does a muscle fiber contract?
– To it’s fullest extent.
– All-or-none response
• So what controls the strength
of a contraction?
– Number of muscle cells recruited
– To get a stronger contraction, more
cells are stimulated
– A single cell can’t contract harder
A Closer Look at Muscle Contraction
Muscle
Fiber
Deltoid
muscle
Myofibril
Actin
sarcomere
Myosin
Big Guns – Crash Course Video
• https://www.youtube.com/watch?v=jqy0i1KX
UO4
Macroscopic Structure
of Muscle
Tendon
• _________attaches
muscle to bone
Origin attachment of
• _______muscle to immovable
(fixed) bone (anchors
muscle)
• Insertion
________- attachment
to bone that moves
when muscle contracts
Belly bulging middle
• _____part of the muscle
Belly of
Biceps
Muscle Movement
fixed
• Muscles originate on a _____bone
in our body,
cross over a ______,
joint and insert onto a ______
movingbone.
• It is important to understand that all muscles
move from the insertion
________ point
going toward the __________
origination
point.
• It is because of the placement of
the muscles that we can
move.
Muscle Movement
• Tendons
– attach _________
muscle to bone
– are inelastic
– don’t stretch when the force of the
muscle acts on them
• When muscle contracts,
it pulls on the _______
bone
• Individual muscles can
only ____
pull in ____
one direction
• Muscles work in
opposing ______
pairs
Muscle Movement
• ______Flexor Muscle that bends the joint when
contracted.
• Extensor
________- Muscle that straightens the joint when
contracted.
• Contracted
__________ muscle
is short, firm, tight
and thicker around.
• Relaxed
_______ muscle is
stretched, long, loose
and thinner around.
Muscle Movement
• When the biceps in the arm contracts the triceps
relaxes
________ causing ________
bendingof the arm.
contracts the biceps
• When the triceps in the arm _________
straighteningof the arm.
relaxes causing ____________
• ______
Pairs of muscles are
needed because the only
activemovement
_________ of a
muscle is to contract
_______, to
lengthen it must be
stretched by the action
_________
of an opposing muscle
_______.
Muscle + Bone Interaction
• Let’s review the structures involved in
movement at a joint.
D
B
C
F
A
•
•C
G
•
E
•
D
•
•C
•B
•F
•B
•F
Ligament
Tendon
Cartilage
Body (Belly)
Origin
Insertion
Contracted muscle
Relaxed muscle
Flexor
Extensor
Naming Muscles
• The skeletal muscles can be difficult to
remember
– Their names are often long and confusing
– The key to learning the muscles is to understand
the basic naming conventions
– Once you see the patterns, it will be much easier
to remember.
Some Basics
• Deltoid - shaped like a triangle
• Orbicularis - orbit, circular muscle
• Major/Minor - large/small or sometimes upper &
lower
• Vastus – large
• Dorsi or Dorsal – backside
• Infra / Supra - lower and upper
• Longis / Brevis - long/ short (brief)
• Medialis / Lateralus - medial (toward the inside),
lateral (toward the outside)
Named for bone or location
attachment
• Biceps femoris - two headed muscle attached
to the femur
• Extensor carpi radialis longus - long muscle
that runs the length of the radius (bone) to
the carpals (wrist bones) that extends the
fingers
Named for movement performed
•
•
•
•
Adductor longus
Abductor hallucis
Exensor carpi radialis brevis
Flexor carpi ulnaris
Involuntary Muscles
– Diaphragm
– Digestive organs
– Arrector pili
– Heart
– Urinary bladder
– Muscles around
blood vessels
Interactive Body
• http://www.bbc.co.uk/science/humanbody/b
ody/interactives/3djigsaw_02/index.shtml?m
uscles
• http://www.bbc.co.uk/science/humanbody/b
ody/