Download Rigor mortis (death rigor)

THE MUSCULAR SYSTEM
What do you already know about
muscle tissue?
What is the definition of an organ?
Types of muscle tissue
Skeletal muscle
Cardiac muscle
Smooth muscle
Functions
1. Producing body movements by
changing chemical energy into
mechanical energy
2. Stabilizing body positions
3. Generating heat
4. Moving substances
Within the body
Skeletal muscle anatomy
Connective tissue around muscle
(epimysium)
– Extends to form tendon (dense regular
connective tissue) – connects muscle to
periosteum of bone
Muscles: bundles
of fascicles (group
of fibers – cells)
surrounded by
perimysium
Nerves and blood
vessels
– At least 1 capillary
per muscle fiber
Myofibrils= contractile organelles 
stripes
Sarcoplasmic reticulum - encircles
myofibrils= similar to smooth ER;
function = stores calcium
Filaments (thin and thick)– inside
myofibrils; don’t extend length of
fiber; contained in sarcomeres
Anatomy of muscle fiber
No mitosis
Growth: hypertrophy due to
hormones (testosterone, HGH)
Sarcolemma = cell membrane
Sarcoplasm = cytoplasm (glycogen!!)
Myoglobin – a protein = binds
with/release O2 for the mitochondria
Mitochondria = many!
Don’t write
Review:
– Sarcolemma
– Sarcoplasm
– Sarcoplasmic reticulum
– Myofibrils
– filaments
HOW A MUSCLE CONTRACTS
http://www.youtube.com/watch?v=re
n_IQPOhJc&list=PL7DDED4766451C0
9D
A neuron connects to a muscle fiber
[called the neuromuscular junction (NMJ)]
Arrival of nerve impulse causes release of
acetylcholine (ACh: a neurotransmitter – a
chemical).
ACh diffuses to receptors on muscular
membrane (sarcolemma), opening a Na+
ion channel, causing Na+ to enter the
muscle fiber
Muscle contraction cont
Causes muscle action potential due to
change in membrane potential (b/c of
addition of Na+ )
Sarcoplasmic reticulum releases stored
Ca+2 into sarcoplasm
Causes muscle contraction (sliding
filament mechanism):
– Unblocks actin (thin) so myosin (thick) heads
can bind to them
– Filaments slide past one another, shortening
the muscle
Sliding filament
mechanism
Sliding filament mechanism
Lengths of filaments do not change
Sarcomere shortens
Causes shortening of muscle fiber
and muscle
Plants/drugs effect NMJ
Botulinum toxin from bacterium
Clostridium botulinum blocks
exocytosis of ACh
Curare – plant derivative – used on
arrow/blowgun darts. Binds
to/blocks ACh receptors
Muscle physiology
Muscles tug on tendons which pull on
bones
One bone is pulled towards another
Insertion towards origin
Most cross a joint
Muscle groups
Prime mover and
antagonist
Opposite actions
Switch roles
Opposite sides of
bone/joint
Lever
systems
Most of the bones of the limbs (arms & legs) act
as levers. These levers are powered by muscles.
A lever is a rigid rod able to rotate about a fixed
point known as a fulcrum, formed by the joint.
Any force applied to the lever is called the
effort.
A force that resists the motion of the lever, such
as the downward force exerted by a weight on
the bar, is called the load or the resistance.
The contraction of the muscles is the effort and
the part of the body concerned is known as the
resistance or load.
Bones of the body act as levers (a mechanical
device) which create a mechanical advantage of
strength or speed.
Muscle contraction
Muscle fibers: all-or-none
Strength of muscle contraction:
depends on # of contracting fibers
Affects energy usage
Providing energy
ATP broken down during contraction
Store little ATP, must produce it
3 ways:
– Aerobic respiration: slow, requires O2, lots
ATP
– Anaerobic glycolysis and lactic acid
formation: faster, no O2 needed, less ATP
– Creatine phosphate and ADP: CP not found
in other cells, very fast, doesn’t last
Muscle fatigue
no contraction
even with
stimulation occurs from
oxygen debt (lactic
acid builds up and
ATP runs low)
Types of muscle contractions
Isotonic: with movement
Isometric: muscle against immovable
(or almost) object
Effect of exercise
Aerobic (endurance): results in
muscles with resistance to fatigue.
Resistance (isometric) training:
enlarged muscles
In review………
(don’t write)
Lifting weights is an example of resistance
or endurance training?
The reaction of creatine phosphate and
ADP generates ATP quickly or slowly?
The ability of your body to use oxygen to
produce ATP is _____ respiration.
True or False: The strength of a muscle
contraction is determined by the amount
of muscle fibers that are contracting.
Don’t write
The strength of a muscle contraction
depends on what?
What is the relationship between the
strength of a muscle contraction and
energy usage?
Muscle fatigue is due to ____ debt
example
Running a 100 yd dash in 12 seconds
requires 6L of oxygen.
But the max amount that could be
delivered and used by your muscles
(VO2 max) would be 1.2 L
Oxygen debt?
= 4.8L
THE
POINT
The more oxygen your body can take
in and use determines your
endurance
DON’T WRITE
Why are some
people better at
endurance
activities?
Why are some
people FAST?
Is it genetic? Is it
training?
Types of muscle fibers
1. Slow oxidative fibers
– Little power (small in diameter); fatigue
resistant; many mitochondria. Adapted for
maintaining posture & endurance activities
2. Fast oxidative-glycolytic fibers
– Intermediate in diameter, faster than #1 but
briefer in duration. Adapted for:
walking/sprinting
3. Fast glycolytic fibers
– Large diameter (contract strongly/quickly); tire
quickly; large amount lactic acid build up
– Short, rapid, intense movement
– Adapted for intense anaerobic movements of
short duration: weight lifting/throwing a ball
muscle fibers in muscles
Muscle are a combo of different
fibers
Proportion of fibers is individual