Muscular System 1 Flashcards
the study of muscle
myology
Muscles make up ____ of one’s body weight
40-50%
enervated by neurons of the somatic nervous system
skeletal muscle
enervated by neurons of the automatic nervous system
cardiac muscle (smooth)
Affected by neurotransmitters and hormones
smooth muscle
5 key functions of muscle tissue:
-Producing body movements -Stabilizing body position -Regulating organ volume (particularly through the use of sphincters) -Moving substances within the body -Producing heat (through contraction of muscle tissue)
How do muscles produce heat?
through contraction of muscle tissue
How does muscle tissue regulate organ volume
through the use of sphincters
4 properties of muscle
-Electrical excitability -Contractility -Extensibility -Elasticity
is stimulated by nerves
Electrical excitability
the ability of a muscle to contract
contractility
Ability of a muscle to expand/stretch
Extensibility
Ability of a muscle to return to its original shape
Elasticity
two types of muscle contractility
-isometric contraction -isotonic contraction
muscle tension without shortening the muscle
isometric contraction
muscle tension is constant as muscle shortens
isotonic contraction
Each skeletal muscle is considered to be an _____
organ
surrounds muscle fibers and whole muscle
connective tissue
penetrate the muscle
blood vessels and nerves
-sheet of fibrous connective tissue -surrounds muscles and other organs
facia
separates muscles from skin
superficial fascia
-dense, irregular connective tissue -lines the body wall and limbs -holds muscles together
deep fascia
connective tissue that surrounds the whole muscle
epimysium
connective tissue that surrounds 10-100+ individual muscle fibers
perimysium
perimysium separates muscle fibers into:
bundles/fascicles
-thin sheath of areolar connective tissue -wraps around each individual muscle fiber
endomysium
-a cord of dense, regular connective tissue -attaches to the periosteum of the bone
tendon
-a broad, flat layer of connective tissue -functions as a tendon
Aponeurosis e.g., frontalis and occipitalis
_____ stimulate skeletal muscle
somatic motor neurons
axons meet at:
the neuromuscular junction
axons usually branch to:
enervate different muscle fibers
-bring oxygen to the muscles -take away heat and metabolic waste
blood vessels
Each skeletal muscle fiber arises from the fusion of ____ cells
mesodermal
A mature muscle fiber has ____ or more nuclei
100 or more
the muscle fiber’s plasma membrane
sarcomere
the sarcoma contain:
T-tubules
fluid filled tunnels in the muscle tissue carrying muscle action potentials
T-tubules
Allows the entire muscle to be enervated at one time
T-Tubules
Cytoplasm of the muscle fiber
Sarcoplasm
-the contractile elements of the skeletal muscle -give the muscle fiber striations
myofibrils
-encircles each myofibril -releases Ca++ to trigger muscle contraction
sarcoplasmic reticulum (SR)
Inside myofibrils are two types of filaments:
-Thin filaments (actin) -Thick filaments (myocin)
Thin filaments
actin
Thick filaments
myocin
Separate one sarcomere from the next
Z discs
the darker portion
the A band
the less dense area (has only thin filaments)
the I band
A Z disc goes through ___ bands
I bands
Area in the middle of the A band
H zone
middle of the sarcomere
M line
make up skeletal muscle
myofibrils
make up myofibrils
sarcomeres
3 kinds of proteins make myofibrils:
- contractile proteins 2. regulatory proteins 3. structural proteins
myocin and actin
contractile proteins
tropomyosin covers the myosin-binding site on actin
regulatory proteins
contribute to alignment, stability, and elasticity of myofibrils
structural proteins
myosin helps pull the thin filaments toward:
the M line
the thin filaments meet at the center of the ____
sarcomere
What happens when thin filaments meet at the center of the sarcomere
-causing Z discs to come together -shortening the sarcomere -shortens the entire muscle
The contractile cycle
-Ca++ is released by the SR (allowing the contraction cycle to begin) -ATP is broken to release energy -Myosin heads attach to actin -“Power Stroke” -Detachment of myosin from actin
It is the ____ filaments that move while the ___ filaments stay stationary
thin filaments move; thick filaments stay stationary
myosin heads attach to:
actin
muscle action potential starts here
Neuromuscular Junction
The synapse between a somatic motor neuron and a skeletal muscle fiber
The Neuromuscular Junction
Where communication between a neuron and its target cel occurs
Synapse
Synaptic cleft divides:
the two cells
surrounds synaptic end bulbs
synaptic vesicles
release Ach into the NMJ
synaptic end bulbs
receives the neurotransmitters
Motor end plate
Describe the chemistry behind muscle contraction:
- Action potential runs down neuron 2. Neuron releases acetyl coline into the synaptic cleft 3. reaches motor end plate of the sarcomere (*Generates action potential*) 4. Action potential runs down the T-tubule 5. Action potential stimulates S.R. to release CA++ 6. Calcium binds to Troponin (changes shape, releasing blocking action of Tropomyosin). Actin actives sites now exposed. 7. “Power Stroke” Hydrolysis of ATP (moves thin filaments to M line (muscle contracts) 8. Tropomyosin blockage restored, myosin heads release actin
Allows for influx of Na+
Acetyl Choline (allows for creation of action potential)
Moves thin filaments to M line
Power Stroke
myosin heads alternatively attach to actin and detach, pulling the actin filaments toward the center of the sarcomere, release of energy through ATP Hydrolysis
“Power Stroke”
thin filaments only
I band
thick filaments only
H zone
Thick filaments linked by accessory proteins
M line
Thick and thin filaments overlap
outer edge of A band
ATP in a muscle fiber
Enough to power a contraction for only a few seconds (4-6 seconds)
ATP in muscle fibers come from three sources:
- Creatine Phosphate
- Anaerobic Cellular Respiration
- Aerobic Cellular Respiration
When at rest, muscles make more ATP than they need, and they put this extra ATP into:
Creatine Phosphate
A series of ATP-producing reactions that don’t require oxygen
Anaerobic Cellular Respiration
A series of oxygen requiring mitochondrial reactions that produce ATP
Aerobic Cellular Respiration
ATP and creatine phosphate stores have enough energy to power a contraction for ____ seconds
10-15 seconds
If you have continuous action potential, you eventually lose _____
Calcium
The inability of a muscle to contract forefully after prolonged activity
Muscle Fatigue
Factors in muscle fatigue:
- Drop in CA++ released from the SR
- Depletion of Creatine Phosphate
With prolonged muscle contractions, increase in:
oxygen delivery to the muscle tissue
The recovery period after exercise is due to:
due to oxygen debt
____ restores metabolic conditions to resting levels
oxygen
Oxygen restores metabolic conditions to resting levels, by conveting lactic acid into:
glucose in the liver
*Later can build up Glycogen in muscle
O2 needed not just to make ATP stores but also:
- ) creatine-phosphate stores
- ) opxygen stored with myoglobin
Oxygen restores metabolic conditions to resting levels by resynthesizing:
Create Phosphate and ATP
Oxygen restores metabolic conditions to resting levels by replacing:
Oxygen removed by myoglobin
