Darius Hadaegh Chapter 6: Myology

How many muscles are in the body?

650

What are the 2 general characteristics of muscles

Excitability and Contractility

What does excitability mean?

capacity to generate electrical impulses

What does contractility mean?

capacity to shorten in length

What are the only 2 cells in the body that exhibit contractility?

Muscle and Nerve cells

What are the 3 functions of the muscles

Voluntary movement, maintenance of body posture, and heat production

What is the tendon of origin commonly called?

head or “ceps”

What does the tendon of origin connect to?

less moveable structures

What is the tendon of insertion commonly called?

tail

What does the tendon of insertion connect to?

more moveable structure

What are the 3 layers of fascia?

epimysium, perimysium, and endomysium

What does a somatic motor unit consist of?

a motor neuron plus all of the muscle fibers it stimulates

What are proprioceptors?

things that we can feel

What is an agonist?

muscle that causes a desired action

What is a synergist muscle?

Helper

What is an antagonist muscle?

muscle that causes the opposite action of the agonist

What is a fixator or stabilizer?

muscle that stabilizes body position and decreases unnecessary movement

What are the characteristics of muscles that are used in maximal training?

large diameter muscle fibers, fast rate of contraction, high power development, low myoglobin content, whiter in color

What are the characteristics of muscles used in sub-maximal training?

smaller in diameter, darker in color because of high myoglobin content

Frontalis

raises eyebrows; wrinkles forehead

Orbicularis oculi

closes the eyelid

Orbicularis oris

puckers the lip

Buccinator

compress the cheek; as when blowing

Platysma

pulls the lower lip and jaw downward

Zygomaticus

smiling (raising corners of mouth)

superior rectus

elevates or raises eye

Inferior rectus

depresses or lowers eye

medial rectus

rotates eye medially

lateral rectus

rotates eye laterally

Temporalis

elevates mandible, and this closes the jaw

Masseter

Synergist with the temporalis; elevates mandible

Genioglossus

protracts tongue, sticks tongue out

Styloglossus

retracts, pulls tongue back in

What are the general characteristics of facial muscles?

they develop from the occipital somites, they are all innervated by the hypoglossal nerve (II)

What nerve innervates the facial muscles?

Hypoglossal Nerve (II)

What is the action of the frontalis?

raise eyebrows; wrinkles forehead

What muscle closes the eyelids?

orbicularis oculi

What muscle is responsible for squinting, winking, and blinking?

orbicularis oculi

What muscle puckers the lips?

Orbicularis oris

What muscle compresses the cheeks?

Buccinator

What muscle pulls the lower lip downward?

Platysma

What is Bell’s Palsy?

Unilateral paralysis of the facial nerve

How many muscles move the eye?

6

What muscles elevates the mandible?

Temporalis

What nerve innervates the tongue?

Hypoglossal Nerve (II)

What are the 2 characteristics of the muscles of the vertebral column

Permit movement of the spine and stabilize (fixate) the spine when moving limbs

What are prevertebral muscles responsible for?

Fixation of the spine (pulls the spine to one side)

Sternocleidomastoid

flexes the head downward

External Oblique

bending body sideways (opposite side), flexing spine forward, stabilizing core during movement.

Internal Oblique

bending body to the same side

Transversus abdominis

stabilize lower back, help breathing and coughing,

Rectus abdominis

flex spine forward, compresses abdominal organs, stabilizes trunk to support lower back during movement.

Quadratus lumborum

Stabilize lumbar spine, contributes do bending sideways, and arching of the lower back.

iliopsoas

Flex and extend waist (switch hitter)

Why is the iliopsoas called the switch hitter?

It flexes and extends the waist

What are postvertebral muscles responsible for?

extension of spine

splenius

extends the neck

What are the three muscles of the erector spine?

Spinalis dorsi, longissimus dorsi, iliocostalis dorsi

trapezius

pulls the shoulders toward the midline; can also elevate the shoulders

What are the 3 parts of the trapezius?

clavotrapezius, spinotrapezius, and acromiotrapezius

Rhomboideus

pulls the shoulders towards the midline (synergist with trapezius)

serratus anterior

pulls the shoulder downward toward the rib

What does abduct mean?

move away from the midline of the body

Deltoid

stabilize shoulder joint, allow wide range of arm movements, mainly lifting arm out to side (abduction)

Supraspinatus

Initiates arm abduction, preventing it from shifting upward the the deltoid muscle engages

What does supinate mean?

turn hand so palm is facing upward

Biceps Brachii

flexes the forearm and supinates the hand

Brachialis

Flexes the forearms (synergist with the biceps brachii)

Brachioradialis

Flexes the forearms (synergist with the biceps brachii)

Triceps Brachii

extends the forearm ( Antagonist of the biceps brachii

Flexor Carpi radialis

flexes and abducts the hand

Palmaris Longus

flexes the hand

Pronator Teres

pronates the hand (antagonist of the biceps brachii)

Extensor Carpi Radialis

extends and abducts the hand

Extensor Carpi Ulnaris

extends and abducts the hand

Thennar Eminence

gripping, grabbing, traction

Levator Ani

Supports the pelvic organs

Bulbocavernosus

constricts vaginal opening, contracts during orgasm

Tensor Fascia Lata

abducts thigh towards the midline

Gluteus maximus

forms much of the mass of the buttocks in men, extends and rotates the thigh laterally

Quadriceps femoris

extends the lower leg

Rectus femoris

located on the mid portion of the thigh

Vastus lateralis

commonly used site for intramuscular injections

Vastus medialis

extend knee joint, working with other 3 quadricep muscles to straighten the leg

vastus intermedius

located just below rectus femoris, but is often difficult to separate from the other 3 parts of the quadriceps

Sartorius

strap like muscle extends diagonally, pulls entire thigh towards hip, this ti flexes the thigh

Gracilis

“Dancers muscle” appears as a very broad muscle in the cat, that almost crosses with the sartorius muscle

Biceps femoris

broader in the cat than it is in man

Semitendinosus

hamstring muscle in the back of the thigh

Semimembranosus

large, flat muscle deep in the back of the thigh

Plantar flexion

movement of the ankle joint where the sole of the food is pointed downward, away from the body

Dorsiflexion

upward movement of the foot at the ankle

tibialis anterior

located just lateral to the anterior crest of the tibia (shin splints)

Extensor digitorum Longus

located on lateral aspect of the leg

gastrocnemius

muscle possesses 2 large heads situated lateral to the midline of the calf

soleus

large, flat muscle located in the calf

flexor digitorum longus

deep muscle located on the posteromedial aspect of the leg

peroneus longus

(fibularis) key muscle on lateral side of your lower leg to help with ankle stability