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MUSCLES OF THE HUMAN BODY KEY
How a muscle moves: Read p. 325
Define the following:
Origin- bone that anchors a muscle; doesn’t usually move
Insertion- bone that attaches a muscle and is moved by it
Prime mover/agonist- The main muscle that places the most force on a bone to move it.
Antagonists- Muscle that reverses the motion of a prime mover.

How do prime movers and antagonists work together to accomplish a motion
such as bending of the elbow? They flex to bend the arm (prime mover) and
extend the arm by contracting antagonist (tricep contracts; bicep relaxes)
Synergists- muscles that work together to make a motion.

Explain how synergist muscles of the wrist help direct movement when you
form a fist. They contract in different amounts to fix the wrist and stabilize
it.
Fixators- contract to provide support to a bone that is being pulled by a prime mover.
MUSCLES OF THE HEAD:
MUSCLE
MEANING
OF NAME
Temporal bone
ORIGIN
Temporal bone
О Temporalis
Chewer
О Masseter
Zygomatic
bone
INSERTION
Under
zygomatic and
attaches to
mandible
Mandible
ACTION
Chewing
chewing

Together these muscles accomplish which action? chewing

Explain how these muscles work together. Synergists- work together to close jaw
temporalis
masseter
MUSCLES OF THE NECK:
MUSCLE
О Digastric
MEANING OF
ORIGIN
NAME
Di= two
Mandible
Gastric=belly/stomach
Breastbone
О
Clavicle
Sternocleidomastoid Mastoid (named after
the bones it connects
to)
Sternum
and
clavicle
INSERTION
ACTION
Hyoid
Swallow/talk
Mastoid
process
Lift or nod
head
Read p. 340.

What are the functions of the muscles of the neck? Swallow and move head

How is the hyoid bone involved in these fuctions? Acts like an anchor that the
muscle can pull against
digastricus
Sternocleidomastoideus
MUSCLES OF THE ABDOMEN:
MUSCLE
MEANING
OF NAME
“straight”
ORIGIN
INSERTION
ACTION
Pubis
Xiphoid
Sit up
“outside
angle”
Ribs
Tendon
Rotation;
posture
Inside angle
Ribs
Ilium/pubis
Rotate
Across
Ribs/ilium
Pubis
Holds in
abdomen
О Rectus abdominis
О External oblique
О Internal oblique
О Transverse
abdominis
Read p. 348.
 What common functions do the muscles of the abdomen accomplish?
Act as a net to stabilize abdomen; maintains posture

What causes the so called “potbelly”? weak and stretched muscles; common
after pregnancy
Rectus
abdominus
Transverse
abdominis
External
oblique
Internal
oblique
MUSCLES OF THE CHEST AND BACK THAT MOVE THE SCAPULA:
MUSCLE
MEANING
OF NAME
Small chest
ORIGIN
INSERTION
ACTION
Ribs
Scapula
Trapezoid
Vertebrae
Clavicle/scapula shrug
Fixes scapula
О Pectoralis minor
О Trapezius
Read p. 352 (Table 10.8):

How do these muscles work with each other to move the scapula?
Pectoralis
major
trapezius
Pectoralis
minor
deltoid
Latissiumus
dorsi
Bicep
brachii
MUSLCES OF THE CHEST AND BACK THAT MOVE THE ARM:
MUSCLE
MEANING
OF NAME
Chest
ORIGIN
INSERTION
Clavicle/ribs
Humerus
Wide back
Vertebrae
Humerus
triangle
Clavicle/scapula Humerus
О Pectoralis major
О Latissimus dorsi
О Deltoid
ACTION
Prime mover
for moving
arm medially
Prime mover
to extend
arms in front
or overhead
Arm rotation;
lift arm
Read p. 354 (Table 10.9):

What type of muscle movement do each of the above muscles accomplish- prime
movement or synergists or fixators?

Why does the movement of the arm require synergists and fixator muscles?

What is the function of the muscles that originate anterior to the shoulder joint?

What is the function of the muscles that originate posterior to the shoulder joint?

How do the latissimus dorsi and pectoralis major work together to move the arm?
MUSLCES OF THE ARM THAT MOVE THE FOREARM:
MUSCLE
MEANING
OF NAME
ORIGIN
INSERTION
ACTION
О Triceps brachii
О Biceps brachii
О Brachialis
Read p. 356 (Table 10.10)

Why are these muscles’ movements limited to flexion and extension?

Why is it harder to do chin ups with the palms facing anteriorly rather than
posteriorly?
MUSCLES OF THE LEGS:
MUSCLE
MEANING
OF NAME
ORIGIN
INSERTION
ACTION
Adductor muscle:
О Gracilis
Quadriceps:
О Rectus femoris
О Vastus lateralis
О Tensor fasciae
latae
Buttocks:
О Gluteus maximus
Hamstrings:
О Biceps femoris
О Semitendinosus
О
Semimembranosus
Calf muscle
О Gastrocnemius
Read p. 369- (Table 10.14)

The gracilis is an adductor muscle. What does this mean and what types of
movements does it take part in?

The rectus femoris and vastus lateralis make up two of the four “heads” of
the quadriceps. What general location are these muscle groups found and
what actions do they accomplish?

Biceps femoris, semitendinosus and semimembranosus are all hamstrings.
What general location would you find these and what roles they play in leg
movement?

Where does the common name of “hamstring” come from?