Chapter 10 Muscle Tissue Flashcards
Functions of Muscle Tissue:
A. Production of body movements.
B. Stabilize body position.
C. Storage and movement of substances through the body.
D. Generating Heat
Properties of Muscle Tissue
A. Electrical Excitability - the ability to respond to stimuli
B. Contractility - the ability to contract (shorten) forcibly when
stimulated
C. Extensibility - the ability to stretch without being damaged
D. Elasticity - the ability to return to its original length and shape
after contraction or extension
Myasthenia Gravis
- an autoimmune disorder
- antibodies bind to Acetylcholine receptors, inactivating them
- patient develops progressive muscle weakness
- initial symptoms often develop in the muscles of the face and
neck - if death occurs it is can be associated with paralysis of the
respiratory muscles
Muscular Dystrophy
- a group of genetic disorders associated with degeneration of
skeletal muscle
Effects of Aging
- the relative number of Slow Oxidative fibers increase
- inactivity leads to fibrosing of skeletal muscle
- overall decrease of skeletal muscle
Smooth Muscle regeneration
- cells can enlarge to provide additional contraction strength
- certain smooth muscles retain the ability to undergo cell
division, ex. Myometrium of the Uterus - Pericytes = stem cells located in capillaries and small veins
- Limited regeneration capability, but much greater than Skeletal
muscle
Cardiac Muscle regeneration
- heals via fibrosis
- existing cells can enlarge to provide additional contraction
strength - recent studies have discovered stem cell that can differentiate
to become healthy cardiac muscle cells, the extent of this
regeneration remains to be discovered
Skeletal Muscle regeneration
- most damaged muscle is replaced via fibrosis (scar tissue).
- undamaged cells will enlarge to attempt to make up for lost
function - Satellite Cells = cells located in Skeletal Muscle tissue that
can differentiate to become new muscle cells (myofibers), not
enough of these cells exist to replace damaged cells - Limited regeneration
Muscle tone
The tautness or tension that is constantly in a muscle due to
involuntary, weak stimulation of the motor units.
a. Flaccid - loss of muscle tone associated with damage to motor
neurons
Types of Skeletal Muscle Fibers: Slow Oxidation fiber
- a red fiber
- high myoglobin content, an iron containing protein that binds
oxygen - smallest diameter
- contains many capillaries
- has many Mitochondria (aerobic respiration)
- fibers contract slower than the other two fiber types
- resist fatigue
- found in postural muscles and in muscles involved in endurance
(i.e. prolonged contraction)
Types of Skeletal Muscle Fibers: Fast Oxidative-Glycolytic
- a red fiber
- high myoglobin content
- intermediate in diameter
- contains many capillaries
- generate ATP by aerobic and anaerobic contraction
- uses ATP faster than Slow Oxidative fibers
- provides faster muscle contraction but fatigue quicker than Slow
Oxidative fibers - associated with activities like walking and sprinting
Types of Skeletal Muscle: FibersFast Glycolytic fibers
- a white fiber
- low myoglobin content
- few capillaries
- few Mitochondria
- generate most ATP via glycolysis (anaerobically)
- provide strong, rapid contraction
- fatigue the quickest
- provide quick, short bursts of muscle contraction
Control of Muscle Tension: The amount of stretch on the muscle fibers before
contraction.
B. Frequency of stimulation - the number of nerve impulses that
pass through a motor unit per second
(1) Wave Summation - The increased strength of a muscle
contraction that result when nerve impulses occur in
rapid succession.
c. The number of motor units that are stimulated.
(1) Motor Unit Recruitment - The process where an increasing
number of motor unit are activated in response to an
increased load.
d. The type of muscle fiber.
(1) Refractory Period - The period of time in which an
excitable cell (i.e. muscle or nerve cell) cannot
respond to a stimulus. Different types of muscle fibers
have different refractory periods
Motor Unit Recruitment
The process where an increasing number of motor
units are activated in response to an increased load
Recovery Oxygen Consumption
the elevated use of oxygen after exercise
to replace the lost energy stores and to facilitate tissue repair after
exertion
Muscle fatigue
the inability of muscle to contract forcefully after
prolonged activity.
Aerobic Respiration
occurs in the Mitochondria
- requires oxygen (oxygen is the limiting factor)
- produces up to 36 ATP
- can get energy from the breakdown of Pyruvic Acid, fatty acids
and amino acids
- provide energy for prolonged muscle use
Anaerobic respiration - occurs in Sarcoplasm
- no oxygen is required
Glucose Glycolysis
or ——————-> 2 Pyruvic Acids + 2 ATP
Muscle glycogen
- provides energy for maximum muscle contraction for 30 to 40 seconds
- when plenty of oxygen is available Pyruvic Acid is transported to the
Mitochondria, where the Krebs cycle occurs
- when the muscle is short of oxygen, Pyruvic Acid is converted to Lactic
Acid which will diffuse into the blood, as the pH of muscle decreases the
ability of the muscle to function will also decrease.
Creatine Phosphate
found in the Sarcoplasm
Creatine Kinase
ADP + Creatine Phosphate —————> ATP + Creatine
- provides energy for maximum muscle contraction for approx. 15 seconds
ATP Production:
- Creatine Phosphate
- Anaerobic respiration - occurs in Sarcoplasm
- no oxygen is required - Aerobic Respiration
Termination of Muscle Contraction
- Acetylcholinesterase- (an enzyme that deactivates ACh) in the
Synaptic cleft continually breaks down ACh. If the signal to
release ACh into the synaptic cleft ceases, the Action Potential in
the muscle will cease.
2.The Calcium pumps in the Sarcoplasmic Reticulum continuously pump
the Ca++ around the myofibrils back into the Sarcoplasmic
Reticulum.
- With no Ca++ to bind to Troponin, the Tropomyosin slides over the
Myosin binding sites. The Myosin head now has nowhere to bind,
thus muscle contraction ceases
Sliding Filament Mechanism
The process where the Thin filaments
are drawn towards the M line. This involves the repeating of
steps 9 through 12.
