Dhruthi Mudduluru Chapter 6: Myology

How many muscles are in the body?

650

What are the two general characteristics of muscles?

• Excitability

• Contractability

What does excitability mean?

ability to generate electrical impulses (Action Potential)

What does contractility mean?

ability to shorten in length

What are the only two cells in the body that exhibit excitability?

nerve and muscle cells

What are the three functions of the muscles?

1. voluntary movement

2. maintainence of body posture

3. heat production

What is the tendon of origion commonly called?

head/ceps

What does the tendon of origin connect to?

less moveable structure(s)

What is the tendon of insertion commonly called?

tail of muscle

What is the tendon of insertion connect to?

more movable structure

What are the three layers of fascia?

1. Epimysium

2. Perimysium

3. Endomysium

What does a somatic motor unit consist of?

somatic motor neurons and all muscles it innerviates

What are proprioceptors?

sensory neurons that supply muscles

What is an agonist?

prime mover; muscles that cause desired action

What is a synergist muscle?

helper; acts with agonist

What is an antagonist muscle?

muscle causing opposite action of agonist

What is a fixator/stabilizer?

muscle that stabilizes body position and decreases unnecesary movement

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

1. large diameter muscle fibers

2. fast rate of contraction

3. high power development

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

1. small diameter muscle fibers

2. slow rate of contraction

3. high endurance development

Frontalis

raises eyebrows, wrinkles forehead

Orbicularis oculi

closes eyelids

Orbicularis oris

puckers lips

Buccinator

compresses check as when blowing

Platysma

pulls lower lip and jaw downwards

Zygomaticus

smiling (raising corners of mouth)

Superior Rectus

elevates eye

Inferior Rectus

depresses eye

Medial Rectus

rotates eye medially

Lateral Rectus

rotates eye laterally

Temporalis

elevates mandible, and thus closes the jaw

Masseter

synergist with the Temporalis (elevates mandible)

Genioglossus

sticks out tongue

Styloglossus

puts tongue back in

What are the general characteristics of facial muscles?

1. all superficial

2. insert into overlying skin

3. develop from the branchial arches

4. all innervated by facial nerve VII

What nerves innervate the facial muscles?

facial nerve (VII)

What is the action of the frontalis?

raises 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 facial of the facial nerve, often from inflammation

How many muscles move the eye?

6

What muscles elevates the mandible?

temporalis

What nerve innervates the tongue?

hypoglossal nerve XI