Muscles: General, Head/Neck

Question 1

Type I vs. Type II muscle fibers

Answer 1

Type I = Slow twitch red fibers. These guys have a lot of mitochondria and myoglobin. Primary energy for these guys is aerobic oxidative phosphorylation of fatty acids, making them great for slow, prolonged contractions, like with postural muscles of the back

Type II = Fast twitch white fibers

IIa = Intermediate oxidative-glycolytic fibers with a lot of mitochondria and myoglobin like with the reds of type I, along with a considerable amount of glycogen, allowing them to use both oxidative metabolism and anaeroebic glycolysis. We need these guys for rapid contractions and and short bursts of activity, such as those needed for athletics

IIb = These have fewer mitochondria and less myoglobin, but abundant glycogen, making them very pale. These depend mostly on glycolysis, and are rapid like IIa, but fatigue much more quickly. These guys are smaller muscles and contain many NMJs, like those for digits and the eyes.

Question 2

Smooth muscle is composed of grouped, _____ ____ cells with weak involuntary contractions

Answer 2

Mononucleated fusiform cells

Question 3

Muscles of Mastication are innervated by what nerves?

Answer 3

Various branches of V3 (mandibular branch of the trigeminal nerve)

Question 4

What are the 4 muscles for mastication and what are their individual functions

Answer 4

• Temporalis - Elevates and retracts the mandible to close the jaw
• Masseter - Elevates and protrudes the mandible to close the jaw
• Medial Pterygoid - Elevates and helps protrude the mandible to close and grind the jaw
• Lateral Pterygoid - Depresses and protrudes the mandible AND moves it side to side to open and grind the jaw

Question 5

What two muscles help assist the lateral pterygoid with opening the jaw?

Answer 5

Suprahyoid and Infrahyoid muscles

Question 6

Innervation and function: Genioglossus

Answer 6

CN 12 - Depresses and protrudes the tongue

Question 7

Innervation and function: Hyoglossus

Answer 7

CN 12 - Depresses and retracts the tongue

Question 8

Innervation and function: Styloglossus

Answer 8

CN 12 - Retracts and elevates the tongue for swallowing

Question 9

Innervation and function: Levator Veli Palatini

Answer 9

CN 10 - Elevates the soft palate for swallowing and yawning

Question 10

Innervation and function: Palatopharyngeus

Answer 10

CN 10 - Tenses the soft palate and moves the pharynx for swallowing

Question 11

What is the palat and glossus rule?

Answer 11

A way to remember which ones are innervated by 10 and 12.

Palats are usually 10, glossus is usually 12

Question 12

Innervation and function: Palatoglossus…oh god, is it innervated by 10 and 12?

Answer 12

Nope, follows the palat rule since palat comes first, so it gets CN 10, the Vagus Nerve.

This guy elevates the posterior tongue and brings the soft palate to the tongue.

Question 13

Innervation and Function: Tensor Veli Palatini

Answer 13

This guy is the only one that doesn’t follow our Palat glossus rule. It is innervated by neither 10 nor 12, but V3 (mandibular branch of the trigeminal)

This guy tenses the soft palate and opens the auditory tube during swallowing and yawning

Question 14

What does the SCM attach to and what does contraction on one side lead to

Answer 14

It attaches superiorly to the mastoid as you might expect and divides inferiorly into two heads that form attachments to the sternum and clavicle.

Contraction causes head tilting to the same side and flexion/rotation of the head to the opposite side

Question 15

What is congenital torticullis?

Answer 15

When you are born with a shortened SCM on one side, leading to a tilted, flexed, rotated head.

Question 16

What is spasmodic torticullis? What other names does it go by?

Answer 16

Also called cervical dystonia or wry neck.

Abnormally increased SCM tone, often associated with spasms of intense neck pain

Question 17

How are the muscles of the larynx broken up?

Answer 17

The first division for larynx muscles if extrinsic vs intrinsic.

Question 18

What are the extrinsic muscles of the larynx and what do they do?

Answer 18

Extrinsic muscles move the hyoid bone and larynx superiorly (suprahyoid muscles) and inferiorly (infrahyoid muscles).

Suprahyoid - Mylohyoid, Geniohyoid, Stylohyoid, Digastric (My Genie Styles my Digs way up (supra/elevate))

Infrahyoid - Sternohyoid, Omohyoid, Sternothyroid, Thyrohyoid

Question 19

What are the intrinsic muscles of the larynx and what do they do?

Answer 19

These guys work together to alter the shape and tension of the vocal folds in order to change the size and shape of the space between the folds, called the rima glottidis.

Four divisions:

• Adductors (3) - Lateral cricoarytenoid muscles (main), Transverse and oblique arytenoids (also act as sphincters to protect during swallowing), and Aryepiglottic muscles (just sphincters mainly)
• Abductors (1) - Posterior cricoarytenoids. Can’t breathe without em
• Tensors (1) - Cricothyroid (raise pitch of voice)
• Vocalis Muscles (1) - Fine voice adjustments

Question 20

Recurrent laryngeal nerve and what damage may cause

Answer 20

Innervates motor activity of inner laryngeal muscles, so damage causes hoarseness (if unilateral) and breathing difficulties/aphonia (if bilateral).

Question 21

When do we worry about recurrent laryngeal nerve damage?

Answer 21

If we damage it’s parent nerve, the inferior laryngeal.

Also, thyroidectomy or if compressed secondary to laryngeal cancer.

Question 22

If motor innervation comes from below, via the inferior giving off the recurrent, where does sensory input come from?

Answer 22

Comes from above via the internal laryngeal nerve, a branch of the superior laryngeal.

Damage here thus leads to anesthesia of the larynx mucosa, making it more likely that foreign bodies will pass through. We hit this with block when we are putting in an endotracheal tube.

Question 23

We stated that coming from above off of the superficial gives us the sensation and that coming from below via the inferior gives us the motor.

What muscle in the larynx violates this nice rule?

Answer 23

Cricothyroid muscle.

Both its sensory and motor come from the above from the superficial. As per the rule, the sensory still comes from the internal, but for motor, the external is used.