Muscular System
List of
muscles to
know is
posted in
canvas.
Muscle Facts
The average human heart will beat
3,000 million times in its lifetime and
pump 48 million gallons of blood.
The masseter is the strongest muscle
in the human body. It can exert as
much as 975lb of force.
The smallest muscle in
the body is the
stapedius attached to
the stapes in the ear.
Muscle is about 15% more
dense than fat.
The tongue consists of 8
different muscles.
The human heart creates enough pressure when
it pumps blood, that it could squirt blood 30 feet.
It takes the interaction
of 72 different muscles
to produce human speech.
Function
of Muscles
•to pull against bones to produce
movement.
•to maintain posture
•to stabilize joints
•to generate heat (mitochondria)
•to pump blood through the body
(heart muscle).
Types of Muscle
●Skeletal – striated & voluntary
●Smooth – involuntary
●Cardiac – heart & involuntary
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Origin and Insertion
•The origin of a muscle is a fixed bone for
attachment.
•The insertion is the bone that the muscle
moves when it contracts.
The biceps and triceps
are antagonistic muscles.
Gross Anatomy of a Muscle: Bundles
1. Actin & myosin myofilaments are bundled
into myofibrils
2. Individual myofibrils (muscle cells) are
bundled together into fibers.
3. Muscle fibers are bundled into fasicles
4. Fasicles are bundled into the whole
muscle.
Linear view of muscle bundling…
Whole Muscle
myofibril
Fasicle
myofilaments
Muscle Fiber
Gross Anatomy Skeletal Muscle
Muscle Layers
Myofibrils are made of myofilaments
ACTIN = thin filaments (light bands)
MYOSIN = thick filaments (dark bands)
How Muscles Work with the Nervous System
NEUROMUSCULAR JUNCTION - where a motor
nerve and muscle fiber come together
There are rules to muscle contractions…
Threshold stimulus: motor neuron releases enough
acetylcholine into synaptic cleft to reach threshold
All-or-None Response: individual muscle fibers (and
all the myofibrils within) will contract when
stimulated.
Recruitment: more and more fibers contract as the
intensity of the stimulus increases. (stimulus is
acetylcholine) more stim=heavier object
Actin & myosin contractile
units are called sarcomeres.
Contraction of
sarcomeres
contracts
muscle as
a whole.
When a muscle contracts the Z-line
(sarcomere) shortens.
This is called the Sliding filament
theory
Actin & Myosin Contraction
Animation
As is the case with any body system…
Issues can arise!
-hypertrophy
-atrophy
-tetanus
-muscle cramp
-muscle fatigue
-oxygen debt
6.
Hypertrophy
- muscles enlarge (working out or
certain disorders)
7.
Atrophy - muscles become small and weak due to
disuse
What is tetanus?
Tetanus causes cholinosterase to not break down the
acetylcholine in the synapse. This results in a person's
muscles contracting and not relaxing.
A tetanus shot
must be
administered
shortly after
exposure to
the bacteria.
Once you
develop
tetanus, there
is no cure.
Muscle Fatigue - muscle loses ability to contract
after prolonged exercise or strain
Muscle Cramp - a sustained involuntary
contraction
Oxygen Debt
oxygen is used to create ATP, -not have enough oxygen causes Lactic Acid to
accumulate in the muscles → Soreness
-
What is rigor mortis?
A few hours after a person or animal dies,
the joints of the body stiffen and become
locked in place. This stiffening is called
rigor mortis. Depending on temperature
and other conditions, rigor mortis lasts
approximately 72 hours. The
phenomenon is caused by the skeletal
muscles partially contracting. The muscles
are unable to relax, so the joints become
fixed in place.
Body Worlds
Body Worlds
Body Worlds
Body Worlds
Body Worlds
Body Worlds