Download Muscle

Muscles
Anatomy and their Function
Patrick Allard, Sarah Ballard,
Christopher Dakin, James Lavender,
Brendan Takata, Melissa Tan,
Duncan Walker, Ariel Ward,
Stephanie Westendorp
Function
• Producing body movements
• Stabilizing body positions
• Regulating organ volumes
•
bands of smooth muscle called
sphincters
• Movement of substances within the
body
•
blood, lymph, urine, air, food and fluids,
sperm
• Producing heat
Outline
• Muscle Anatomy
• Sarcomere Anatomy
• Different Proteins in a Muscle
• Excitation
• Movement
• Excitation-Contraction coupling
• Contraction
• Relaxation
Muscle Overview
Myofibers
Myofibrils & Myofilaments
Filaments and the
Sarcomere
Myosin
Actin
Proteins of Muscle
•
•
•
Structure of NMJ
Junction
Action potential travels
down axon of motor neuron
and reaches axon terminal
Action potential causes the
release of synaptic
vescicles (acetylcholine)
through exocitosis
Vesicles release
acetylcholine into the
synaptic cleft, which bind to
the ach receptors on
sarcolemma (motor end
plate)
•
•
•
•
Structure of NMJ
Junction
Binding causes channels to
open and allows influx of
Na+ into the muscle fiber
Influx of Na+ makes the
muscle fiber positively
charged, causing an action
potential to travel along the
sarcolemma and into the
transverse tubules
Change in membrane
potential of the transverse
tubules triggers the release
of Calcium ions by
sarcoplasmic reticulum
Calcium ions start
Motor Unit
Movement
• Skeletal muscle spans a joint and is
attached to bones by tendons at both
ends.
•
•
•
Epimysium, perimysium, and
endomysium extend beyond fleshy part
of muscle to form tendon or
aponeurosis.
As muscle contracts, it creates a force
either tension or compression, which is
uniform across the muscle and tendon.
One of the bones remains relatively
fixed or stable while the other end
Twitch Contraction
Tension – Length Curve
Excitation – Contraction
Coupling
ATP, ADP, Creatine Reaction
Steps in Contraction Cycle
Sliding Filaments
Concentric
Eccentric
Isometric
Isotonic and Isometric
Contraction
•
•
•
•
•
•
•
Relaxation
Acetylcholinesterase (AChE) breaks down
ACh within the synaptic cleft
Muscle action potential ceases
Ca+2 release channels close
Active transport pumps Ca2+ back into
storage in the lateral sacs
Calcium-binding protein (calsequestrin)
helps hold Ca+2 in SR (Ca+2
concentration 10,000 times higher than in
cytosol)
Tropomyosin-troponin complex recovers
binding site on the actin
•
•
•
•
•
•
Steps to Cessation
Cessation of muscle activity is caused by these
stages:
Stoppage of the efferent action potential leading to an
inhibition of the release of acetylcholine into synaptic
cleft
Acetylcholinesterase breaks down the previously
released acetylcholine allowing for its recycling
Removal of acetylcholine from ligand gated ion
channels in the motor end plate allow for its
repolarization
Repolarization of the motor end plate causes a
change in the voltage gated ion channels of the
sarcolemma allowing for its subsequent repolarization
Repolarization of sarcolemma signals the end of the
muscle fiber's stimulating action potential
Steps
to
Cessation
•
Cessation of stimulating action potential stops release of
calcium ions from the sarcoplasmic reticulum allowing
for the calcium to be actively transported back into the
sarcoplasmic reticulum and bound to calcequestrin
•
•
•
A decrease in the availability of free calcium in the
muscle fiber cause troponin-tropomyosin complex to
change shape and cover the myosin binding sites on
actin molecule reducing the number of actively bound
myosin crossbridges
Decrease in actively bound cross-bridges allows for
lengthening of the sarcomere, decreasing tension in the
elastic connective tissue surrounding the fiber and
muscle as a whole (parallel elastic components) which
lowers the tension in the tendons of the muscle (series
elastic components)
Muscle tension lowers and under ideal conditions
Excitation – Contraction
Coupling
Finish