Download Muscular System - Northside Middle School

Muscular System
3 Types of Muscle
Skeletal Muscle (aka "striated“ or "voluntary“)
attached to bones and under conscious, willful
control. Has the ability to contract (shorten) and
thereby bring about movement
I. Muscles and Muscle Fibers
Muscles are composed of many fibers that are
arranged in bundles called FASCICLES
A muscle also contains 3
different layers of connective tissue:
Muscle fiber (cell)
Endomysium
Tissue around 1 muscle cell
Perimysium
Tissue bundle of muscle fibers (fascicle)
Epimysium
Tissue around an entire muscle belly
Muscle belly
Entire macroscopic organ
How does a muscle cell obtain energy?
Fibers contain multiple mitochondria for
ATP energy (cellular respiration)
Most fibers have multiple nuclei
Muscle Cell (Muscle Fibers)
The muscle fiber
membrane is called
the SARCOLEMMA
Muscle fiber cytoplasm is
called SARCOPLASM
The muscle fiber membrane is called the SARCOLEMMA
and the cytoplasm is called the SARCOPLASM. Within the
sarcoplasm are many parallel fibers known as MYOFIBRILS
Human Anatomy
11/2
1. Finish muscle Fatigue Lab
2. Color Muscle Tissue Worksheet
3. On the back of the worksheet, define/describe
the terms labeled D-N
Fascicle
myofilament
Epimysium
Muscle fiber (cell)
Muscle belly
Sarcomere
Stop Day 1
How do muscle
cells contract?
It is important to remember the
hierarchy of muscle fibers
myosin
Muscle fiber
fasicles
myofilaments
actin
Each muscle fiber (cell) is made of many protein
filaments called Myofilaments. There are two types:
ACTIN – thin, Actively slide up past myosin
MYOSIN – thick, does not slide, but moves
the actin filaments
?
?
?
Structure of a SARCOMERE (functional unit of a muscle)
The actin and myosin overlap to form dark
and light bands on the muscle fiber
 A band = dArk, thick (myosin)
 I band = lIght, thIn (actin)
•In the middle of
•
each I band are Z
lines.
A sarcomere is
one Z line to the
other
(I band)
(A band)
Sarcomere
* The arrangement of these sarcomeres next to each other
produces the Striations (Z Line) of the skeletal muscle.
SLIDING FILAMENT THEORY
The theory of how muscle contracts is the sliding filament
theory. The contraction of a muscle occurs as the thin
filament slide past the thick filaments.
The sliding filament theory involves five
different molecules plus calcium ions.
The five molecules are:
1.
myosin
2.
actin
3.
tropomyosin
4.
troponin
5.
ATP
Each Myofibril is surrounded by a network of channels
called SARCOPLASMIC RETICULUM.
TRANVERSE TUBULES (T Tubule) pass through the fibers.
The sliding filament theory involves five different
molecules. The five molecules are:
1.
myosin
2.
actin
3.
tropomyosin
4.
troponin
5.
ATP
Include the function of all
molecules in #7 of ‘Sliding
Filament Theory’ worksheet.
Any questions?
If you don’t ace the next
test I will destroy you!!
Cells use electrical impulses to
communicate. Muscles use
electricity to contract.
desiree jennings 2020 part
1 youtube
dystonia
Muscles & Nervous System
NEUROMUSCULAR JUNCTION - where a nerve fiber and muscle
fiber come together.
MOTOR NEURON ENDINGS - nerve fiber caries electrical signal
called an action potential that stimulates the muscle fibers
MOTOR END PLATE - specialized part of muscle
fiber membrane that transmits neural impulses to
the muscle.
Neuromuscular Junction
1. Neuron
2. motor end plate
3. Synaptic
Vesicle
4. Neurotransmitter
Receptor
5. Mitochondria
SYNAPTIC CLEFT - An physical gap or “cleft”
which exits between the motor neuron endings
and the motor end plate.
A cleft chin
SYNAPTIC VESICLES - where neurotransmitters are stored in
neuron before being released into the synaptic cleft.
NEUROTRANSMITTER – chemical substance
that transmits signals across a synapse
Noradrenaline is a neurotransmitter
The neurotransmitter that crosses the gap is ACETYLCHOLINE.
ACETYLCHOLINE - The neurotransmitter that brings about
muscle contractions. It is stored in synaptic vesicles.
Synaptic
Vesicles
Synaptic
Cleft
Neurotransmitter
Motor Unit
The muscle
fiber and the
motor neuron
Video Time
The ‘Tough Mudder’ Race features live
electricity obstacles to run through.
III. Events in Muscle Contraction
Nerve impulse stimulates the release of a
neurotransmitter (acetylcholine) from
synaptic vesicles into synaptic cleft. This
stimulates muscle impulse.
Impulse spreads across sarcolemma and
into fiber along the T-tubules . This
impulse causes an increase in the
cisternae's permeability to calcium ions.
The S.R. has a high conc. of Ca++. Calcium
ions diffuse into the sarcoplasm. The Ca++
causes the formation of "cross bridges"
between the actin and myosin filaments '
The filaments slide between each other '
this shortens the myofibrils which in turn
shorten the muscle fibers, which shortens
the muscles
Sliding Filament Handout
IV. Energy Source
•Provided by ATP from cellular respiration.
Occurs in the mitochondria in myofibrils.
(requires O2 and glucose, produces CO2,
H2O and ATP)
•Only 25% of energy produced during cellular
respiration is used in metabolic processes the rest is in the form of HEAT.
(This is what produces our body heat and maintains body
temperature. More muscle activity = more heat)
• Creatine phosphate
increases
regeneration of ATP
Threshold Stimulus
Minimal strength required to cause a contraction
Motor neuron releases enough acetylcholine to
reach threshold
All-or-None Response
Fibers do not contract partially, they either do or
don't
Motor Unit
The muscle fiber + the motor
neuron
Recruitment
more and more fibers contract as
the intensity of the stimulus
increases
Muscle Tone
Sustained contraction of
individual fibers, even when
muscle is at rest
Hypertrophy
- muscles enlarge (working out or certain
disorders)
Atrophy - muscles become small and weak due to disuse
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,
during exercise you may not have enough oxygen
-> this causes Lactic Acid to accumulate in the
muscles
-
*See Magic School Bus
-
Origin and Insertion
Origin = the immovable
end of the muscle
Insertion = the movable
end of the muscle
**when a muscle
contracts the insertion is
moved toward the origin
The biceps brachii has two origins
(or two heads).
Cardiac Muscle Fiber
(400x Magnification)
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.
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.