EXAM 2 ANATOMY - COMBINED

What is a reflex?

Neural pathways that quickly facilitates a sensation

What is the purpose of reflexes?

Protect the body

What neuron types make up reflex arcs?

Sensory, motor, and interneurons

Monosynaptic reflex definition

Only 2 neurons - sensory and motor

Polysynaptic reflex definition

Multiple interneurons

Describe the general path of monosynaptic reflexes

Afferent neuron originating at stretch receptor in skeletal m, Terminate at LMN innervating same muscle, Involuntary contraction to counteract the stretch

What happens when there is a change in muscle stretch (reflexes)

Activates a muscle spindle fiber, Inputs to a proprioceptive afferent neuron in a DRG, Excites a lower (alpha) motor neuron in the ventral horn of the same cord segment that initiated the contraction

What are deep tendon reflexes?

Monosynaptic reflex arc present in large muscles throughout the body

What type of response is the patellar reflex?

Deep tendon reflex

What spinal cord is involved in the patellar reflex?

L4

Describe the path of the patellar reflex.

Strike patellar tendon, Stretch muscle spindles in quadricepts, Stimulates proprioceptive afferents, Alpha motor neuron conduct SM back to muscle + interneurons send relaxation signal to hamstrings

What type of response is the jaw jerk reflex?

Deep tendon reflex

What nerve segment is involved in the jaw jerk reflex?

CN V3

Describe the path of the jaw jerk reflex.

Sudden lengthening of skeletal m., Stimulates proprioceptive afferents, Alpha motor neuron activity V3, Fiber contraction

What kind of response is considered abnormal for the jaw jerk reflex?

Jerk motion

What can lead to abnormal jaw jerk responses?

Lesion on CN V, palsy, ALS, UMN Lesion

How would a LMN lesion impact deep tendon reflexes?

Disrupt efferent signal

Hyporeflexia

Reduced reflex response

Areflexia

Absence or loss of normal response

Which type of reflex has a degree of voluntary control?

Polysynaptic reflex

What is the purpose of the withdrawl reflex?

Protect the body from painful, damaging stimuli

What is the purpose of the cough reflex?

Protect airways and lungs

Sensory limb of cough reflex

CN X - VS reflex, Larynx - internal laryngeal n. + others (can also be triggered by SS)

What locations can trigger a cough reflex?

Oropharynx through lyngs

Where is the cough center located?

Between brainstem and pons

Describe the 3 phases of the cough reflex

Inspiration (diaphragm + intercostals contract), Glottic closes (increase thoracic pressure), Glottic opens, abdominal m. contract to expel air

Is it easier to trigger a cough standing up or laying down?

Laying down

Sensory limb of gag reflex

CN IX - VS reflex, posterior pharyngeal wall mucus + SS (sometimes)

Where is info from the afferent limb of the gag reflex processed?

Nucleus ambiguous of medulla

What other centers are close to the gag center?

Vomiting, salivary and cardiac centers

What are the 3 phases of the gag reflex

Elevate soft palate to protect nasal cavity, Closure of glottis to protect airways, Posterior pharyngeal m. constrict + tongue protrusion

How does dental anxiety influence the gag reflex?

More hypersensitive gag reflex (triggered by dental tools and procedures)

Sensory limb of corneal (blink) reflex

CN V1 - Nasociliary n. from cornea via ciliary nn

Motor limb of corneal (blink) reflex

CN VII - temporal and zygomatic branch to orbicularis oculi

Sensory limb of accommodation reflex

CN II - From stimulation of retinal ganglion cells

Motor limb of accommodation reflex

CN III (para) - via short ciliary nn to ciliary mm.

To see far objects, should parasympathetics to the accommodation reflex increase or decrease?

Decrease (relax ciliary mm. and pupil sphincter)

To see close objects, should parasympathetics increase or decrease

Increase (contract ciliary mm. and pupil sphincter)

Sensory limb of pupillary light reflex.

CN II - from stimulation of retinal ganglion cellls

Motor limb of pupillary light reflex.

CN III (para) - short ciliary n. to pupillary sphincter

What is the purpose of the vestibulo-ocular reflex?

Stabilize gaze during head movement

Sensory limb of VOR

CN VIII (vestibular branch) - semicircular canals (horizontal plane)

Motor limb of VOR

Extraocular muscles (MR and LR) - CN III and CN VI respectively

What is the purpose of the vestibulocollic reflex (VCR)

Brainstem reflex that stabilizes the head in response to movements → stable gaze and orientation

Describe the general pathway of the VCR

Head is moved or external forces act on it, the vestibular system, detects the motion, VCR, activates the neck, stabilize the head in space

Sensory limb of VCR

CN VIII (vestibular branch)

Motor limb of VCR

Neck m. - cervical plexus and accessory n.

Describe the path of CN XII (include key vessels)

Rootlets branch off medulla, Hypoglossal nucleus, Hypoglossal canal, Inf. and lat. between ICA and IJV, Loop around occipital a., Branches to intrinsic and extrinsic tongue muscles

What muscles does CN XII run deep to?

Posterior belly of digastric, stylohyoid, mylohyoid

What muscles does CN XII run superficial to?

Hyoglossus

What extrinsic tongue muscles are innervated by CN XII?

Genioglossus, Hyoglossus, Styloglossus

Primary actions of genioglossus

Protrude and depress tongue

Primary actions of hyoglossus

Depress and retract tongue

Primary action of styloglossus

Elevate and retract tongue

What nerve hitchhikes on CN XII and where does it go to?

C1 - Thyrohyoid and Geniohyoid

Clinical test for CN XII

Ask patient to protrude tongue - observe if it is in midline

Describe the path of CN IX

Rootlets originate on medulla, Jugular foramen, Travel superficial to stylopharyngus, Split into components (pharyngeal branch and continued between S and M pharyngeal constrictors)

Pharyngeal branch of CN IX branches into…

Tonsillar and lingual branhces

What fiber types are on the tonsillar branch of CN IX?

SS

What fiber types are on the lingual branch of CN IX?

SS and taste to posterior 1/3 of tongue

CN IX continues inferiorly between ______ and ______ to reach _______ .

Superior pharyngeal constrictor, Middle pharyngeal constrictor, Carotid sinus + carotid body

What kind of receptor is in the carotid body?

Chemoreceptor

What kind of receptor is in the carotid sinus?

Baroreceptor

Describe the path of CN X

Rootlets originate on medulla, Jugular foramen, Split into components, Continue to thorax, Cardiac plexus, Esophageal plexus, Anterior and posterior vagal trunk, Through diaphragm, Abdomen

What are the 3 main branches of CN X?

Pharyngeal branch, Superior laryngeal, Recurrent laryngeal

What are the 2 smaller branches of CN X?

Meningeal and auricular branches

What does the pharyngeal branch of CN X innervate?

Muscles of pharynx and palate

What does the superior laryngeal branch of CN X innervate?

Internal branch - supraglottic region, External branch - cricothyroid m.

What does the internal branch of superior laryngeal n. of CN X pierce?

Thyrohyoid ligament

What does the recurrent laryngeal n. innervate?

All intrinsic laryngeal m. and SS to infraglottic region

What is the terminal branch of the recurrent laryngeal n.?

Inferior laryngeal n.

What structure does the R recurrent laryngeal n. loop around?

R subclavian a.

What structure does the L recurrent laryngeal n. loop around?

Arch of aorta

What nerves are easily damaged during thyroid removal?

Recurrent laryngeal n.

What arteries need to be ligated during a thyroid removal and where do they come from?

Inferior and superior thyroid a.; Thyrocervical trunk and ECA

CN IX provides SS to…

Ear, nasopharynx, and oropharynx

CN X provides SS to…

Laryngopharynx, larynx, trachea, esophagus, epiglottis

What branch of CN IX innervates the tympanic membrane?

Tympanic n.

What branch of CN X innervates the tympanic membrane?

Auricular branch

CN IX provides SM to…

Stylopharyngus

CN X provides SM to…

Cricothyroid, Levator veli palatini, Cricopharyngeus, Salpingopharyngeus, Palatoglossus, Palatopharyngeus, Phrayngeal constrictors

Clinical test for CN IX and X SM

Ask patient to protrude tongue and say “ahh” - visusally inspect movement of uvula and palate

CN IX provides taste to…

Posterior 1/3 of tongue

CN X provides taste to…

Valleculae and epiglottis

Describe the path of taste from anterior 2/3 of tongue

Anterior 2/3 of tongue, Lingual n., Chorda tympani, Geniculate ganglion, Nucleus of solitary tract, Brain

Describe the path of taste from posterior 1/3 of tongue

Posterior 1/3 of tongue, Lingual branch of IX, Inferior ganglion of CN IX, Nucleus of solitary tract, Brain

Describe the path of taste from the epiglottis

Epiglottis, Pharyngeal branches of CN X, Inferior ganglion of CN X, Nucleus of solitary tract, Brain

CN IX provides parasympathetics to…

Parotid gland

[Parasympathetics/Sympathetics] increase saliva production in the parotid gland

Parasympathetics

Describe the path of parasympathetics to the parotid gland

Inferior salivatory nucleus, CN IX, Jugular foramen, Inferior ganglion of CN IX, Tympanic n. (back to skull), Tympanic plexus, Lesser petrosal n., Foramen ovale, Otic ganglion (synapse), Hitchhike on auriculotemporal n. of CN V3, Parotid gland

Describe the path of sympathetics to the parotid gland.

Lateral horn T1-2, Ventral root, Spinal n., Ventral ramus, White communicating ramus, Sympathetic trunk (ascends), Superior cervical ganglion (synapse), ECA plexus, Maxillary and superficial temporal a., Parotid gland

Where are parasympathetic cell bodies of CN X located?

Dorsal motor nucleus of vagus (medulla)

What travels through the carotid sheath?

CN X, CCA, IJV

What n. bring parasympathetics to the supraglottic region?

Internal branch of superior laryngeal n.

What n. brings parasympathetics to the infraglottic region?

Recurrent laryngeal n.

In the pulmonary plexus, parasympathetics cause…

Bronchoconstriction

In the pulmonary plexus, sympathetics cause...

Bronchodilation

Where is the carotid plexus found?

Aortic arch and tracheal bifurcation

In the cardiac plexus, sympathetics cause...

Increased heart rate

In the cardiac plexus, parasympathetics cause…

Decrease heart rate