Anatomy and Physiology Reviewer – Comprehensive Study Guide and Exam Preparation Notes

MUSCULAR SYSTEM STRUCTURES-MUSCLE FIBER STRUCTURE

Functions: 1. SARCOLEMMA:
 cell membrane-contains T-tubules.
1. Movement 2. SARCOPLASM:
2. Maintainposture  cytoplasm of muscle fiber (cell).
3. Respiration 3. MYOFIBRIL:
4. Production of body heat  thread-like proteins that make up muscle fibers.
5. Communication 4. MYOFILAMENT:
6. Heartbeat  proteins that make up myofibrils.
7. Contraction of organs and vessels  Ex. actin and myosin.

SARCOPLASMIC RETICULUM: stores and releases
Types: Ca2+.

1. Skeletal Muscle Sarcomere-basis for muscle contraction theory
2. Cardiac Muscle known as sliding filament theory.
3. Smooth Muscle


General Properties of Muscle STRUCTURES-ACTIN AND MYOSIN
MYOFILAMENTS
1. EXCITABILITY:
- Respond to stimulus 1. ACTIN:
2. CONTRACTILITY:  Thin myofilament
- Ability to shorten  Resemble 2 strands of pearls.
3. EXTENSIBILITY: 2. MYOSIN:
- Can stretch  Thick myofilament
4. ELASTICITY:  Resemble golf clubs.
- Recoil 3. TROPONIN:
 attachmentsiteonactinforCa2+.
4. TROPOMYOSIN:
Clinical Significance of Muscle  Filament on grooves of actin.
 attachment site on actin for myosin.
1. Muscles are sites for the introduction of drugs.
 Intramuscular injections in the: arm (into deltoid
muscles), thigh (into vastus muscles), and
buttocks (into gluteus muscles). STRUCTURES-SARCOMERES
2. Muscles are efficiently used in lifting & moving
1. SARCOMERE:
clients.
 contractile unit-contains actin and myosin.
2. Z DISK:
 protein fibers that form attachment site for
SKELETAL MUSCLE actin.
3. H ZONE:
Characteristics:  center of sarcomere-contains only myosin.
4. I BAND
1. Makes up 40% of body weight.
 Contains only actin.
2. Named because attached to bones (skeleton).
5. A BAND:
3. Many nuclei per cell (near periphery).
 Where actin and myosin overlap.
4. Striated
6. M LINE:
5. Longest of muscle types.
 Where myosin are anchored.


STRUCTURES-CONNECTIVE TISSUE COVERINGS
EXCITABILITY OF MUSCLES FIBERS
1. EPIMYSIUM:
 connective tissue that surrounds entire skeletal
muscle (outside).
2. MUSCLE FASCICULUS:
 bundle of muscle fibers.
3. PERIMYSIUM:
 connective tissue around each muscle
fasciculus.
4. MUSCLE FIBER:
 Skeletal muscle cells.
 Many nuclei.
5. ENDOMYSIUM:
 Connective tissue that surrounds each muscle
fiber.

,ACTION POTENTIAL

 “electricity”
 stimulus that causes rapid depolarization and
repolarization.
 causes muscle to contract.

DEPOLARIZATION

 change in charges.
 inside becomes more + and outside more.
 Na+ channels open.

REPOLARIZATION

 Na+ channels close.
 change back to resting potential.

SODIUM-POTASSIUM PUMP

 pumps Na+ out of cell and transports K+ into
cell.
 restores balance.


NERVE SUPPLY AND MUSCLE FIBER
STIMULATION

1. MOTOR NEURON:
 nerve cells that carry action potentials to
muscle fibers.
2. NEUROMUSCULAR JUNCTION (SYNAPSE):
 where nerve cell and muscle fiber meet.
3. PRESYNAPTIC TERMINAL:
 end of nerve cell (axon).
4. SYNAPTIC CLEFT:
 space between presynaptic terminal and
postsynaptic membrane.
5. POSTSYNAPTIC MEMBRANE:
 muscle fiber membrane.
6. SYNAPTIC VESICLE:
 in presynaptic terminal.
 store and release neurotransmitters.
7. NEUROTRANSMITTER:
 Chemicals that stimulate or inhibit a muscle
fiber.
 Ex. Acetylcholine




SKELETAL MUSCLE CONTRACTION

The Sliding Filament Mechanism




STEPS IN A MUSCLE CONTRACTION (Sliding
Filament Theory)

, 1. An action potential travels down motor neuron to  Tetanus:
presynaptic terminal causing Ca2+ channels to - Muscle remains contracted.
open.
2. Ca2+ causes synaptic vesicles to release
acetylcholine into synaptic cleft.
TYPES OF MUSCLE CONTRACTIONS
3. Acetylcholine binds to receptor sites on Na+
channels, Na+ channels open, and Na+ rushes  ISOTONIC:
into postsynaptic terminal (depolarization). - amount of repetitions increases.
4. Na+ causes sarcolemma and t-tubules to  Concentric – movement is against gravity.
increase the permeability of sarcoplasmic  Eccentric – movement is with gravity.
reticulum which releases stored calcium.  ISOMETRIC:
5. Ca2+ binds to troponin which is attached to - amount of tension increases (weight).
actin.
6. Ca2+ binding to troponin causes tropomyosin to
move exposing attachment sites for myosin.
SLOW TWITCH FIBERS
7. Myosin heads bind to actin.
8. ATP is released from myosin heads and heads  Contract slowly
bend toward center of sarcomere.  Fatigue slowly
9. Bending forces actin to slide over myosin.  Long distance runners
10. Acetylcholinesterase (enzyme breaks down  Use aerobic respiration.
acetylcholine) is released, Na+ channels close,  Energy from fat
and muscle contraction stops.  Dark meat
 Red or dark because of myoglobin.
 Myoglobin: helps O2 bind in muscle



FAST TWITCH FIBERS

 Contract quickly
 Fatigue quickly
 Sprinters
 Use anaerobic respiration.
 Energy from glycogen.
 White meat



OTHER FACTS ABOUT TWITCH FIBERS

 Humans have both types of fibers.
 Distribution of fibers is genetically determined.
 Neither type can be converted but capacity can
be increased through intense exercise.



SKELETAL MUSCLE ANATOMY

 Origin:
Other Information - Non movable end
 Insertion:
 ATP is made in mitochondria from aerobic or - movable end.
anaerobic respiration.  Belly:
 During a muscle contraction, H zone and I band - middle
shorten but A band stays the same.  Agonist:
 Striations of skeletal and cardiac muscle are - muscle that accomplishes a certain
due to sarcomeres (actin and myosin). movement.
 Rigor mortis:  Antagonist:
- person dies and no ATP is available to release - muscles that oppose each other.
cross-bridges.  Synergists:
- muscles that work together.
Terms  Fixator:
- muscles that hold one bone in place.
 Threshold:
- weakest stimulus needed to produce a
response.
 All or None Law: NOMENCLATURE
- Muscle contracts or doesn’t (no in between)
 Twitch: Muscles are named according to:
- Rapid contraction and relaxation of a muscle.