Download HAP Chapter 8 - Central Lyon CSD

Make a short list of what you do voluntary
and involuntary with your muscles…
A. Def – organs composed of specialized
cells that use chemical energy to
contract.
B. Three Types
1. *skeletal*
2. smooth
3. cardiac
Neuromuscular junction
Aponeuroses
Neurotransmitters
Sarcoplasmic reticulum
Motor neuron
Motor end plate
Fascia
Myosin
Sarcomere
Myofibrils
Actin
Motor unit
A. Connective Tissue Coverings
1. Fascia – surrounding connective tissue
that… (pg.170)
a. Holds muscle in position
b. Separates muscles
c. May project into a tendon and
connect to the periosteum.
2. Aponeuroses – sheet like connective
tissue that… (pg.188)
a. Can attach to bone
b. Cover adjacent muscles
3. Epimysium – surrounds outside of
muscle
4. Perimysium – extend inwards from
epimysium and separate into small
compartments (fascicles)
5. Endomysium – covers each muscle
fiber.
Study Analogy
You are going to give someone 100 pencils.
The pencils will represent muscle fibers. First
you wrap each individual pencil in tissue
paper. This would be endomysium. Then
you take about 10 pencils in a bundle (a
fascicle) and wrap them in paper
(perimysium). After that you take all the
bundles and wrap them in paper
(epimysium). But you are going to mail this,
so you also have to wrap it in brown paper
representing the fascia.
B. Skeletal Muscle Fibers
1. Def – single cell that contracts w/
stimulation and relaxes w/o.
2. Sarcolemma – cell membrane
3. Sarcoplasm – cytoplasm
-mitochondria
-myofibrils (aid in contraction)
a. Myosin – thick protein
b. Actin – thin protein
*produce characteristic of striations
4. Sarcomere – extends from Z line to Z line
a. I bands – thin bands of actin filaments
-attached to z line
b. A bands – thick bands of myosin
filaments
-myosin overlaps actin filaments
-H zone – only thick filaments
-M line – protein that holds thick
filaments in place.
5. Sarcoplasmic reticulum & T-Tubules – store
calcium and activate muscular contraction
when stimulated
1.
8.
2.
2.
4.
5.
7.
6.
3.
6.
C. Neuromuscular Junction – connection
between muscle and motor neuron.
1. Every muscle fiber is connected to an
axon from a nerve cell. (motor neuron)
2. Extends from brain to muscle fiber.
3. Motor end plate
-nuclei and mitochondria are present
4. Motor neuron branches into muscle
fiber.
5. Neurotransmitters – released into the
synaptic cleft and cause muscle to fire
Questions to think about…
1. Describe the general structure of a
skeletal muscle fiber.
2. What is the neuromuscular junction?
3. What is the purpose of the motor end
plate and motor neuron axon?
4. What is the function of a
neurotransmitter?
*myosin binds to actin and exerts a pulling
motion. Actin and myosin filaments slide
past each other.*
A. Roles of Actin and Myosin
1. Myosin – contain cross-bridges that
are forked.
2. Actin – are globular structures that
have binding sites for cross-bridges.
Troponin and tropomyosin are part of the
actin filament.
3. Sliding Filament Model
a. Sarcomeres shorten b/c crossbridges pull on actin filament.
b. Cross-bridges can then release and
move to another biding site and pull
again.
c. ATPase (enzyme) – breaks down ATP
to ADP and phosphate.
d. SFM can occur as long as there is ATP.
B. Stimulus Contraction
1. Nerve impulse is sent…
2. Acetylcholine (neurotransmitter) is
released into synaptic cleft.
3. Acetylcholine diffuses to receptors.
4. Creates a muscle impulse.
-sent throughout the muscle fibers
-reaches the sarcoplasmic reticulum
5. S.R. releases Ca2+ ions into the
sarcoplasm of the muscle fibers.
6. Ca2+ ions expose binding site on actin
filament.
7. Contraction occurs…ATP and
acetylcholine
C. Relaxation of Muscles
1. Nerve impulses cease…
a. Acetylcholine is decomposed by
acetylcholinesterase.
b. Prevents continuous contraction
2. Ca2+ ions are transported back to S.R.
a. Troponin and tropomyosin return to
normal state.
b. Actin and myosin return to normal
state.
D. Energy Sources for Contraction
1. ATP – energy source for muscles
a. Must be a continual supply to
continue contraction
b. ADP + Phosphate must be
regenerated back to ATP
-creatine phosphate – reconnects ADP +
Phosphate…thus allowing more ATP
for your muscles to use.
very abundant
*Why would some people
take creatine supplements?*
E. Oxygen Supply and Cellular Respiration
1. Glycolysis – breakdown of glucose for
energy
a. Used best with oxygen..
-blood carries O2 to muscles
hemoglobin
-O2 is released into muscles and
stored there
myoglobin
F. Oxygen Debt
1. Resting…blood supplies all O2 needs
2. Active…blood can’t supply O2 needs
a. Lactic acid is produced
b. Oxygen debt forms
c. No oxygen = no activity
3. Training helps…
a. Building mitochondria
b. Increase capillaries
c. Allows for less O2 debt and thus less
lactic acid in muscles.
G. Muscle Fatigue and Heat Production
1. Fatigue – losing the ability to contract
-lack of blood, lactic acid
-can cause cramps
2. Cellular reactions…lead to heat
byproducts
-blood transports to other tissues and
to skin’s surface.
A. Threshold Stimulus – the minimum amount
of stimulation required to fire a muscle.
1. Caused by Acetylcholine
B. All or None Response – when stimulated,
a muscle fiber fires fully.
1. Each muscle fiber is controlled by a
motor neuron.
2. The whole muscle (ex: biceps) does not
need to fire…only what is needed
C. Muscular Contraction
1. Terms…
a. Twitch – single muscular contraction
b. Tetanus – sustained contractions
c. Latent period – delay b/t signal and
response.
d. Fast Twitch Muscle – high intensity,
quick and strong fibers; fatigable
e. Slow Twitch Muscle – lower intensity,
slower muscle fibers; fatigue resistant
A. Smooth Muscle Fibers
1. elongated
2. lack striations
3. sarcoplasmic reticulum not developed
B. Types of Smooth Muscle
1. Multiunit
a. Muscle fibers are separate
b. Found…
-irises, blood vessels,
2. Visceral
a. Sheet-like
b. Found…
-walls of hallow organs (stomach,
intestines, uterus, bladder…
c. Can stimulate each other
-“peristalsis”
C. Smooth Muscle Contraction
1. Similar to skeletal muscle
2. norepinephrine and acetylcholine
3. Slow to contract
4. longer contractions
5. have the ability to stretch
A. Location – heart
B. Functions…
1. similar to skeletal and smooth
2. contains more actin, myosin and
striations
3. intercalated discs
-join cells together better
-pass muscle impulses better
4. rhythmic