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A&P Lec Exam 2
Terms in this set (70)
What are the functions of muscles?
Provide movement and heat
What are the 3 forms of muscle found in the body?
Cardiac, smooth, skeletal
Which type of muscle is involuntary, striated, contains intercalated disks, and has Y or H shaped cells?
Which type of muscle is fatigue resistant with many mitochondria?
Which type of muscle is involuntary, not striated, and often arranged in a sheet?
Which type of muscle has spindle shaped cells?
Which type of muscle has a slow contraction rate?
Where is smooth muscle found? Give 3 examples
Visceral walls. Arteries, uterus, gastrointestinal tract
Which type of muscle lacks transverse tubules?
Which type of muscle is voluntary and striated?
Which type of muscles have well developed transverse tubule systems?
Skeletal and Cardiac
Which type of muscle is cylindrical in shape?
Which type of muscle is multinucleated?
Describe the structural breakdown of skeletal muscle
muscle > fascicles > muscle fibers (cells) > myofibrils > thick and thin filaments
The fascia known as epimysium covers what?
The fascia known as perimysium covers what?
The fascia known as endomysium covers what?
Muscles fibers (cells)
Epimysium, perimysium, and endomysium come together to create _________? It is composed of _______ tissue?
Tendon - Dense Regular Connective Tissue
Thin filaments are composed of?
Actin-primary protein, troponin-3 protein subunit, tropomyosin-long strand
Thick filaments are composed of?
Myosin - Proteins that have heads to create cross bridges
Troponin and tropomyosin combine to create the _____________ _________ ?
Define a sarcomere
Structural unit of a myofibril, functional unit of contraction
What makes a sarcomere shorten during contraction?
Thick and think filaments slide past each other
What happens to A band during contraction?
Nothing. It does not change length
Where in sarcomere is the A band?
Area where thin filaments and thick filaments overlap
Where in sarcomere is the H zone?
Area within the A band, only thick myosin filaments
What part of sarcomere is the I band?
Area composed of only thin filaments (actin),
z line in middle
What happens to I band during contraction?
What happens to H zone during contraction?
Covers myosin binding sites in relaxed muscle
Keeps tropomyosin in position on actin and contains calcium binding sites
What is the stimulus for a muscle contraction?
Acetylcholine is released from the end of a motor nerve fiber
Why is the motor end plate folded?
To increase surface area for acetylcholine receptors
A motor unit consists of?
1 motor neuron and the muscle fibers associated with it
What stops muscles from contracting continuously once acetylcholine is released
Aetylcholinesterase decomposes acetylcholine
What is action potential
Sequence of electrical changes in part of a nerve cell membrane exposed to a stimulus that exceeds threshold
Summarize the events in muscle contractions
1. Action potential of motonueron. Nerve impulse moves down motor neuron axon.
2. Acetylcholine binds binds to receptors and sodium ions rush in
3. A muscle impulse is generated
4. Muscle impulse travels down T tubules (T tubules become hypoolarized
5. Calcium ions released into sarcoplasm from sarcoplasmic reticulum
6. Calcium ions bind to troponin, causing the troponin-tropomyosin complex to shift away from the actin binding sites
7. Myosin heads attach to exposed actin binding sites
8. Power stroke occurs releasing ADP and P
9. ATP binds to myosin head and myosin releases from actin
10. Energy transferred from ATP to "recock" the myosin head
Summarize the events in relaxation of muscles
1. Acetylcholinesterase destroys Acetylcholine in the synaptic cleft
2. Receptors are no longer filled and impulse stops
3. Calcium pumps send (active transport) calcium back into the sarcoplasmic reticulum
4.Without Calcium, the toponin-tropomyosin complex shifts back and the binding sites on actin become blocked again
5. Cross bridges cannot be made and relaxation is induced
Define neuromuscular junction
Functional connection between a motor neuron and the motor end plate of a muscle fiber
What are the sources of ATP to muscle?
1. Creatine phosphate system - immediate energy (10 sec)
2. Anaerobic system - Glycolysis
3. Aerobic system - Citric acid cycle, electron transport chain
How does creatine phosphate effect muscle contraction?
Stores energy so ATP can be synthesized from ADP & allow powerful sustained contractions
___________ is needed by the liver to convert accumulated lactic acid into glucose
If anaerobic state continues, _______ _______ builds up and must be buffered
Oxygen debt is ?
The amount of oxygen required to convert built up lactic acid to glucose and to restore supplies of ATP and creatine phosphate
Anaerobic threshold is reached when ?
The intensity of exercise is greater than oxygen supply.
How do you measure the anaerobic threshold?
Measure pulmonary exchange
*Buffering of lactic acid makes excess CO2
*A spike in respiration rate shows the body is trying to get rid of excess CO2 being made from anaerobic ATP production
How can a person's anaerobic threshold be altered
Fatigue is produced by _______ ?
1. lactic acid
2. electrolyte imbalances
3. blood flow decreased
4. psychological reasons
Muscle cramps are caused by ?
sustained involuntary muscle contraction. Usually caused by electrolyte imbalance
What are the types of muscle fibers?
1. Type I - slow twitch oxidative
2. Type IIa - fast twitch oxidative glycolytic
3. Type IIb - fast twitch glycolytic
Type 1 muscle fibers are also known as
slow twitch oxidative
Type 2a muscle fibers are known as
fast twitch oxidative glycolytic
Type 2b muscle fibers are known as
fast twitch glycolytic
Which type of muscle fibers would be used for postural muscles in the neck and back? Why
Type 1 - slow twitch oxidative
Red fibers have high oxidative capacity and are extremely fatigue resistant.
Aerobic metablolism supplies energy
Which type of muscle fibers would be used by your arm muscles to throw a ball? Why
Type 2b - fast twitch glycolytic
White fibers have a fast contraction rate for speed and power, but are very fatigue susceptible.
Anaerobic metabolism supplies energy
Which type of muscle fiber has the speed of fast twitch, but some of oxidative capacity like slow twitch?
Type 2a - fast twitch oxidative glycolytic
Contraction types are:
Isotonic (concentric) or (eccentric)
Muscle shortens with force production in a _________ contraction
Muscle lengthens with force production in a ____________ contraction
Force is produced but muscle does not change length in a ________ contraction
In a ___________ contraction, the muscle changes length and force is produced
The immoveable end of a muscle is it's _______
The moveable end of a muscle is it's ________
The functional classifications of skeletal muscles during movements are ?
Agonist - prime mover
Synergist - assists prime mover
Antagonist - opposes prime mover (one contracts, one relaxes)
Polarization of the sarcolemma is generated by ___ ions outside the cell and ____ ions inside the cell
Potassium K+ (inside negative because less K+)
Resting potential is maintained at ______ mv
What is the stimulus for depolarization of membranes?
Sodium channels open and Na+ rushes in
The _______ stimulus, the _______ the depolarization of a membrane
An action potential results once depolarization reaches threshold potential of ____ mv
Describe events which lead to nerve impulse conduction
1. Nerve cell maintains resting potential by pumping na+ and k+ up their concentration gradients while diffusion occurs
2. Neurons are stimulated, causing local potentials, which may reach threshold of -55 mv
3. Sodium channels open
4. Sodium rushes in, depolarizing membrane
5. Potassium channels open
6. Potassium rushes out, membrane repolarizes
7. Resulting action potential causes an electric current that stimulates attached portions of the membrane
8. Action potentials move along the length of the axon as a nerve impulse
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