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Chapter 9: Muscles and Muscle Tissue

Key Concepts:

Terms in this set (59)

Name the 3 types of muscle tissue
cardiac, smooth and skeletal
Characteristics of skeletal muscle
- striated
- voluntary control
- multi nucleated, cells fused during development
Characteristics of cardiac muscle
- striated
- involuntary control
- uni nucleated and bi nucleated, branching
Characteristics of smooth muscle
- not striated
- involuntary (ANS controls)
- uni nucleated cells
4 characteristics of muscle tissue
1. excitability
2. contractility
3. extensibility
4. elasticity
4 functions of muscle
1. produce movement
2. maintain posture
3. stabilize joints
4. generate heat
Each muscle has...
1 nerve, artery and veins
Motor unit =
alpha motor neuron + muscle fibers
Order of connective tissue sheaths from outside working in...
1. epimysium
2. perimysium
3. endomysium
Epimysium
dense irregular connective tissue surrounding the entire muscle
Perimysium
fibrous connective tissue surrounding the fascicle
Endomysium
areolar connective tissue around the muscle fibers
sarcolemma
membrane of the cell or muscle
motor end plate
receptors, aka neuromuscular junction. The junction formed by a single muscle fiber and the axon terminal
T tubules
allow us to get the signal thru the muscle faster
sarcoplasmic reticulum
stores calcium and releases it on demand when the muscle fiber is stimulated to contract.
Calcium
provides the final GO signal for contraction
myofibrils
contains sarcomeres. found within a single muscle fiber
myofilaments
thick and thin filaments found within the sarcomere (myosin and actin)
sarcomere
functional unit of muscle contraction, composed of myofilaments
sarcoplasm
muscle fiber cytoplasm that contains myoglobin and glycosomes and surrounds the myofibrils
myoglobin
stores oxygen in the muscle
A band
dark regions made up of myosin. contains the H zone and M line
H zone
lighter region in the middle of the dark A band. contains the M line
M line
line of protein that bisects the H zone vertically
I band
lighter regions with actin only
Z disc
sheet of proteins on the midline of the I bands
actin filaments
anchored to Z disc, thin filament, contains troponin and tropomyosin
myosin filaments
thick filament, connected at M line, travels with ATP, extends length of A band
sliding filament theory
actin slides past myosin causing the sarcomere to shorten
muscle fiber contraction occurs when...
calcium binds to troponin and tropomyosin is shifted out of the way of the binding site
Step 1 of sliding filament theory
cross bridge formation
Step 2 of sliding filament theory
power stroke: myosin head rotates inward
Step 3 of sliding filament theory
cross bridge detachment (requires ATP)
Step 4 of sliding filament theory
myosin head moves to next binding site (cross bridge cycling)
neuromuscular junction
where the motor neuron synapses with the skeletal muscle cell
1st action leading to a muscle fiber contraction
action potential arrives at axon terminal at NMJ
2nd action leading to a muscle fiber contraction
ACh released and binds to receptors on the sarcolemma
3rd action leading to a muscle fiber contraction
ion permeability of the sarcolemma changes
4th action leading to a muscle fiber contraction
local change in membrane voltage occurs (depolarization)
5th action leading to a muscle fiber contraction
local depolarization ignites action potential in sarcolemma
6th action leading to a muscle fiber contraction
action potential travels across the entire sarcolemma
7th action leading to a muscle fiber contraction
action potential travels along the T tubules
8th action leading to a muscle fiber contraction
sarcoplasmic reticulum calcium ions; calcium ions bind to troponin; binding sites on actin exposed
9th action leading to a muscle fiber contraction
myosin heads bind to actin; contraction begin
1st action to stopping a contraction
signal to the muscle fiber stops
2nd action to stopping a contraction
calcium is pumped back into the sarcoplasmic reticulum
3rd action to stopping a contraction
tropomyosin again covers actin binding sites
4th action to stopping a contraction
actin slides back to its original position (sarcomere lengthens to resting position)
5th action to stopping a contraction
the muscle relaxes
Latent period
signal spreading into muscle cells; cross bridge cycle begins but no measurable force is created
period of contraction
cross bridge cycling; sarcomere, muscle shorten
period of relaxation
calcium is returned to the SR; sarcomere returns to normal resting position
How do you change the strength of a muscle contraction?
change frequency of stimulation; change strength of stimulus
wave summation
2 stimuli in rapid succession
unfused tetanus
stimuli at a faster rate; linked to wave summation
complete tetanus
fused, sustained contraction; fastest stimuli
How to change the strength of a muscle stimulus?
more motor unit recruitment (to increase strength of contraction)
Effects of training skeletal muscle
1. hypertrophy
2. increased mitochondria
3. increased blood supply
4. better neuromuscular coordination
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