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Study Guide

§ Primary function is to convert chemical

energy into mechanical energy to produce
body movement
§ Three types of muscle tissue:
1. ____________ muscle
§ Striated, under voluntary control, functions to
move bones of skeleton

2. ____________ muscle
§ Striated, under involuntary control has
autorhythmicity, found only in the heart

3. ____________ muscle
§ Nonstriated, under involuntary control, located
in walls of hollow internal structures

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§ 4 Functions:
1. Producing body ______________
2. Stabilizing body positions
3. Moving substances within the body
4. Producing __________

§ 4 Properties:
1. Electrical excitability
2. ______________
3. Extensibility
4. ______________

§ Organ produced of elongated muscle fibers

§ Plus nerves, blood vessels, and connective tissues

§ Hypodermis
§ Separates muscle from skin

§ _________
§ Units muscles with similar functions, carries nerves and
vessels, fills spaces between muscles

§ Three layers of connective tissue protect ad strengthen

skeletal muscle
1. Epimysium: outmost layer encircles the muscle
2. Perimysium: bundles muscle fibers into fascicles
3. Endomysium: innermost layer surround each muscle fiber

§ Each skeletal muscle is supplied by one artery and one or

two veins
§ _________ neurons: stimulate muscle fibers through
axons

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§ Hypertrophy: muscle growth occurring from

enlargement of existing muscle fibers
§ Parts of a muscle fiber:
§ ______________:
§ Covers each muscle fiber, contains tunnel-like extensions
called transverse tubules that open to the cell’s exterior
§ Sarcoplasm
§ Contains glycogen and ____________, which binds oxygen
molecules for use in ATP synthesis
§ Full of long contractile elements that give the fiber its striated
appearance, called myofibrils
§ Myofibrils
§ Contractile elements surrounded by a sarcoplasmic
reticulum (SR)
§ SR stores and releases calcium
§ Myofibrils have ________ filaments and _________ filaments
arranged in sarcomeres
§ Sarcomeres are separated by Z-discs

§ ___________ and Actin:

§ _____________ proteins found inside myofibrils

§ Myosin is the main component of thick

filaments, converts chemical energy in ATP to
mechanical energy of motion
§ Actin is the main component of thin filaments,
has myosin-binding site where the myosin head
can attach
§ ____________ and Troponin
§ ______________ proteins that are part of the thin
filament
§ Help switch contraction on and off

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§ Arise at neuromuscular junctions, the synapse

between a motor neuron and a skeletal muscle
fiber
§ ______________________: neurotransmitter released
from the motor neuron that binds to ACh receptors on
the motor end plate of the sarcolemma of the muscle
fiber
§ Excitation of a muscle fiber:
1. Release of ACh as impulse from brain or spinal
cord reaches synaptic end bulbs
2. Activation of ACh receptors when ACh bind to
motor end plate ACh receptor
3. Ion channels ___________
4. Generation of a muscle action potential that
stimulates a contraction
5. Breakdown of ACh by the enzyme
acetylcholinesterase

§ ___________ ______________ mechanism: model describing the contraction of muscle

§ Involves thin filaments at both ends of the sarcomere being pulled to the center of the sarcomere by myosin
head activity. Sarcomere shortens.
1. Ca2+ release channels are opened when muscle action potential propagates along the sarcolemma
2. Ca2+ flows into sarcoplasm, combines with troponin, moves the troponin-tropomyosin complex away from
the myosin-binding sites on actin
3. Myosin heads then bind to actin, contraction cycle begins
§ _______________ cycle: repeating sequence of events that causes filaments to slide
§ Four steps of contraction cycle:
1. ATP splits
2. Myosin attaches to actin
3. Power ___________ occurs
4. Myosin detaches from actin
§ Contraction cycle repeats for as long as ATP and calcium are available in the sarcoplasm
§ Relaxation occurs when impulses in the motor neuron stops ACh release

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§ Muscle tension
§ Controlled by stimulation frequency and motor unit recruitment
§ Frequency of stimulation governs the total tension that can be produced by a single
muscle fiber
§ Total tension produced in a whole muscle depends on number of fibers contracting in
unison

§ Motor unit: one motor neuron and all the skeletal muscle fibers the motor neuron
stimulates
§ Many small motor units are needed for ____________, ___________muscle movements
§ Fewer, large motor units are needed for controlling ____________, ____________muscle
movements

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§ Twitch contraction: response of a motor unit

of a single impulse in its motor neuron
§ Three phases of a twitch:
1. ___________ period: series of events leading
up to contraction
2. ___________ period: power strokes generating
tension
3. ____________ period: the muscle resumes its
original length
§ Wave summation: multiple stimuli that arrive
before the muscle fiber has fully released
§ Unfused tetanus: when frequency of
stimulation allows partial relaxation
§ Fused tetanus: rapid frequency of stimulation
and sustained contraction

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§ Motor unit recruitment:

§ Process of increasing the number of
contracting motor units
§ Muscle _____________
§ A small amount of tension due to involuntary
alternating of contractions of small number
of motor units that do not produce
movement
§ _______________: loss of tone in a muscle
due to damaged motor neurons

§ Isotonic contractions: change in muscle

length without a change in tension
§ Isometric contraction: when the load
equals or exceeds muscle tension and the
muscle does not lengthen of shorten

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1. From creatine phosphate

2. By anaerobic cellular respiration
3. By aerobic cellular respiration
§ Muscle _____________: inability of muscle to contract forcefully after prolonged
activity
§ _________ ________ (aka recovery oxygen uptake): increased oxygen intake in
heavy breathing after prolonged muscle activity to restore metabolic conditions

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§ Skeletal muscle fibers are classified as:

1. _________ oxidative
§ Aerobic cellular respiration
§ Slow speed of contraction
§ Fatigue resistant, good for posture and endurance activities
2. Fast oxidative-glycolytic
§ Aerobic cellular respiration and glycolysis
§ Fast speeds of contraction
§ Moderately fatigue-resistant, used for walking and sprinting
3. __________ glycolytic
§ Use glycolysis mainly
§ Contract strongly and rapidly
§ Adapted for intense bursts of anaerobic movements, fatigue quickly
§ Most muscles are a ________________ of all 3 types.
§ Proportions can be altered by training, genetics, and muscle action.

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§ Found in the wall of the heart

§ Have ________ nucleus and are
branched and ____________
§ Fibers are interconnected with
intercalated discs
§ Some cardiac muscle cells maintain
the heart’s rhythm (autorhymicity)
§ Constant supply of oxygen and
nutrients is needed for continuous
work of heart muscle fibers

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§ Is _______________
§ Responds to autonomic nervous system
impulses, hormones, and local factors
§ Two types:
1. ____________ (single-unit) smooth
muscle tissue
§ Autorhythmic
§ Fibers connected by gap junctions to allow
cells to contract as a single unit
2. Multi-unit smooth muscle tissue
§ Acts independently, has few gap junctions,
lacks autorhythmicity

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§ Made up of voluntarily controlled skeletal muscles

§ Most skeletal muscles produce movement of body
parts
§ Some stabilize bones during movement

§ Movement is produced with the ___________ is

pulled toward the origin
§ Insertion: a muscle’s attachment on the movable
bone
§ Origin: a muscle’s attachment to an immovable bone

§ ___________: rigid structure that moves around a

fixed point called a fulcrum
§ Effort applied to the lever moves the load
(resistance)
§ __________ act as levers
§ ___________ are fulcrums
§ Skeletal muscles supply the ____________

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§ Produce facial expressions, eyeball movement,

assist in biting, chewing, swallowing, and speech
§ _____________ eye muscles
§ Among the fastest contracting and most precisely
controlled skeletal muscles
§ Allow for elevation, depression, abduction,
adduction, and medial and lateral rotation of
eyeballs
§ _____________ muscles move the mandible
§ Masseter, temporalis, medial pterygoid all move
the mandible to close the jaw
§ Medial and lateral pterygoids move the mandible
from side to side and protract it
§ _____________ movements: important for
chewing, swallowing, and speech

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§ Two groups of muscles stabilize

and move the hyoid bone, allowing
it to serve as the base of
attachment and action of the
tongue
1. ___________ muscles
§ Elevate the hyoid bone, oral cavity,
and tongue
2. ___________ muscles
§ Depress the hyoid, move larynx
during swallowing and speech
§ Some neck muscles balance and
move the head on the vertebral
column

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§ Protect and contain the abdominal organs

§ Move vertebral column
§ Assist breathing
§ Diaphragm: large, dome-shaped muscle that
separates the thoracic and abdominal cavities
§ Most important muscle for breathing
§ Contraction results in inhalation; relaxation results
in exhalation

§ ____________ intercostals: elevate ribs during

inhalation
§ ____________intercostals: used in forceful
exhalation to decrease thoracic cavity volume

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§ Pelvic ________________
§ Supports pelvic organs, resists increases
in intra-abdominal pressure, acts as a
sphincter for defecation, urination, and
vaginal control
§ Perineum
§ Important for childbirth, erection of the
penis and clitoris, ejaculation, urination
and defecation.

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§ Muscles that move the pectoral girdle stabilize the

________________and facilitate its function as the origin
for most of the muscles that move the humerus
§ Rotator cuff: tendons of several should muscles that give
the shoulder joint strength and stability
§ Flexors of the ___________ joint:
§ Biceps brachii
§ Brachialis
§ Brachioradialis

§ Extensors of elbow joint:

§ Triceps brachii
§ Anconeus

§ Forearm muscles:
§ Many muscles in forearm that move wrist, hand, and fingers
§ Pronator teres and pronator quadratus pronate
§ Supinator allows ______________
§ Intrinsic muscles of the hand: Originate within the
hand, allow ability to grasp and manipulate objects
easily

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§ Move the ________ and vertebral

column
§ Splenius muscles: attach to the sides
and back of the neck for head
extension, flexion, and rotation
§ Erector spinae group: largest muscle
mass of the ____________
§ Prime movers of the spinal column,
allow back extension
§ Iliocostalis group
§ Longissimus group
§ Spinalis group
§ Transversopinales and segmental
muscles also aid in vertebral column
movements

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§ Muscles that move the thigh at the hip originate on the

pelvic girdle and inserts on the femur
§ Ilipsoas: flexes the thigh
§ Adductor longus, adductor brevis, and adductor
magnus: adduct, medially rotate and flex the thigh
§ Gluteus __________ and gluteus minimus abduct the
thigh
§ Tensor fascia latae: flexes and abducts the thigh

§ Gracilis: straplike muscle that adducts the thigh and

flexes the leg at the knee
§ Quadriceps femoris: muscle group that is a powerful
extensor of the leg at the knee
§ _______________: muscle group on thigh that flexes the
leg at the knee and extends the thigh
§ Muscles that move the foot at the ankle and toes are
located in the leg
§ Intrinsic foot muscles: originate and insert within the
foot to move the toes, influence the arch of the foot

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