Neuro Module 3 Neuro Function and Cranial Nerves

Voltage
Ligand
-Thermal-
Mechanical-

responds to shearing (ex: inner hair cells)

responds to temperature

Tough and Fiberous, Outermost layer

(Chemical gate) – respond to neurotransmitters to open or close

Middle layer of Meninges that resembles a spider's web

Regulated) – respond to + or – charges. Results in action potential

innermost lining of meninges, helps form the CHOROID PLEXUS (which makes CSF)

most abundant, many dendrites and one axon

– Golgi Type I – projection - long axon that extends into different portions of the nervous system (ex. It may start in the CNS and extend into the PNS)

– Golgi Type II – local circuit – smaller and remain in the CNS, integrate neuronal groups, mostly unmyelinated.
– circuits

one dendrite and one axon (located in the eye and ear)

have peripheral processes, connector type sensory neurons

they innervate muscles and glands (efferent)

sensory neurons, respond and receive input

connect neurons to each other

highest

point of initiation of the action potential

SENDS SIGNAL ACROSS SYNAPTIC CLEFT and then to yet another cell’s DENDRITE

– insulator, assists speed of neurotransmitters, has breaks called the Nodes of Ranvier
-where action potential actually occurs in the breaks of the myelin, hopping along – called Saltatory transmission

Speed is determine by two things:
1. Diameter of axon and the myelin
Thicker is better, the faster
2. Temperature, example: put cold on an injured body part, slows down the neurotransmitters (as well as reduces swelling)

at least 2 or more, short compared to axons, cytoskeleton – allows transport of cell waste (out), receive info from neighbor cell (in) and provides structure
RECEIVING INFO FROM OTHER NEURONS

long single - Golgi Type 1, attaches to the body of the cell at the axon hillock, can short Golgi Type 2,
longer and less branching than the dendrites, if branching, called collateral, and is at right angle and has few of them, contains few organelles, but a well organized cytoplasm

12

special protein in neurons found in RER, necessary for membrane upkeep and info processing. Purpose is to replace any lost protein

all except I and II
(olefactory and optic)

nerve is not firing, - 70 mV (because of the Sodium Potassium Pump, we have a slightly negative internal potential across the membrane at rest)
The difference in potentials across the membrane of a cell at rest, so the internal cytosol is slightly more negative than the external (about -70 megaVolts)

There are more negative ions inside the cell than outside the cell

Olefactory, smell, sensory

mechanical or chemical events that effects the plasma membrane
Might be excitatory or inhibitory, but it is very short lived, usually happen in the cell body or the dendrite, they don’t go long distances.

Happens in an initial charge and then the signal gets weaker as it goes along

Optic, vision, sensory

When a local potential is excitatory, channels open and negative flows out, and positive flows in
The intracellular becomes less negative due to the influx of the sodium.

Think of depolarization as approaching 0 from the negative side.

Oculomotor, visual convergence, pupil size/lens shape, motor

inhibitory; the graded channels open and more negative ions come in, so the intracellular becomes more negative, greater than the -70 megavolts. (more negative than -70)

trochlear, visual tracking (down and out), motor

ALL or NOTHING

Series of depolarization along the axon, just as strong in the beginning as it is at the end of the transmission
• Better for longer transmissions
• Initiated at the axon hillock
• Sometimes referred to the as the actual nerve impulse
• Result of depolarization at the axon hillock

Trigeminal, facial sensations & mastication, both
Maxillary Division:
_ Temples
_ Posterior nose
_ Upper cheeks
_ Lower eyelids, upper lip
_ Gums
_ Teeth
_ Soft & Hard palate

Mandibular Divisions
_ Teeth and gums of the mandible
_ Skin of the temporal region of the head
_ Outer ear
_ Lower lip
_ Lower face
_ Muscles of mastication
_ Mucous membrane of the anterior two-thirds of the tongue

Ophthalmic Division
_ Lacrimal – supplies lacrimal gland, conjunctiva, upper eyelid, (tear ducts)
_ Frontal – forehead, conjunctiva, upper eyelid
_ Nasociliary – mucous membranes of nostrils, ala (side) and apex (tip) of nose

• Channels open up (DEPOLARIZATION/sodium gates open/inside cell becomes positive), the sodium enters the cell, the peak is hit for the charge (-40 mV) and sodium charge is inactivated, sodium gate closes as (REPOLARIZATION/potassium gates are opened/potassium flows outside of the cell/restores positive charge outside of cell) Potassium gates are opened, and it sets off this all or not action potential which sends a negative wave down the axon, non-decrementing (does not get weaker), and keeps sending it to the end – the terminal bouton
NEXT it activates the SYNAPTIC VESICLE, that, releases a neurotransmitter to the next cell’s dendrite
Ligand (chemical gate) – refer to as the neurotransmitter (converted from electrical signal to chemical signal)
IF the neurotransmitter is INHIBITORY THEN
RESTING POTENTIAL is INCREASED, resulting in HYPEROLARIZATION
IF the neurotransmitter is EXCITATORY THEN
RESTING POTENTIAL is DECREASED, resulting in DEPOLARIZATION

(REFRACTORY PERIOD - RECOVERS to slightly negative then -70 mV (potassium gate closes), and then goes back to RESTING POTENTIAL level)

• Synaptic transmission – hops across the synaptic cleft to the next cell’s dendrite
– Inhibitory / excitatory neurotransmitters

The AP is the nerve impulse, the wave of negativity that propagates along the nerve cell.

abducens, lateral eye movement, motor

• Presynaptic terminal – the sight of the actual transmitting axon
– Terminal boutons/ motor end plate (when interacting with a muscle)
– vesicles – within are different types of neurotransmitters, released into the synaptic cleft and received by the opposite dendrite
• Synaptic cleft
• Post-synaptic

Facial, sensations to the tongue, soft palate, facial expressions, both

_ Branchial Motor
_ Voluntary control of the muscles of facial expression (including buccinator, occipitalis and platysma muscles), as well as the posterior belly of the digastric, stylohyoid and stapedius muscles
_ Visceral Motor (General Visceral Efferent) tears and mucous
_ Stimulates secretion from the submandibular, sublingual, and lacrimal glands, as well as the
mucous membranes of the nasopharynx and hard and soft palates.
_ Special Sensory (Special Visceral Afferent) taste
_ Conveys taste information from the anterior 2/3 of the tongue and the hard and soft palates.
_ General Sensory (General Somatic Afferent) (touch)
_ Conveys general sensory information from the skin of the concha of the external ear and from a small area of skin behind the ear.
_ It may also supplement the mandibular division of CN V in providing sensation from the wall of the acoustic meatus and the outer surface of the tympanic membrane.

• Largely a chemical process
• Presynaptic- release of neurotransmitter
• Postsynaptic – accepts neurotransmitter

vestibulocochlear (acoustic), hearing equilibrium, sensory

_ Vestibular branch
_ Cell bodies in vestibular ganglion
_ Innervates semicircular canals
_ Destined for the Vestibular Nucleus (lateral-dorsal medulla)
Affected by some growth or tumor

_ Auditory branch
_ Cell bodies in spiral ganglion
_ Innervates cochlea
_ Destined for the Cochlear
Nucleus (dorsal (high frequency )& ventral (low frequency), in rostral [top of] medulla)
_ These branches travel together as the VIII nerve

• Excitatory – glutamate CNS, Ach in PNS, decreases the resting potential (DEPOLARZATION – less negative)
• Inhibitory – GABA, increases the resting potential (HYPERPOLARZATION – more negative)
• Neuropeptides – modulation
Dopamine and ACH

glossopharyngeal, swallowing, salvation, taste, both

_ Branchial Motor Component
_ Provides voluntary control of the stylopharyngeus muscle (elevates the larynx & pharynx during swallowing and speech)
_ Visceral Motor Component
_ Parasympathetic component - innervates the ipsilateral parotid gland (a major salivary gland)
_ Visceral Sensory
_ Innervates the baroreceptors (pressure) of the carotid sinus and chemoreceptors (pH,
oxygen) of the carotid body
_ General Sensory:
_ pain, temperature, and touch from the skin of the external ear, internal surface of the tympanic
membrane, the walls of the upper pharynx, and the posterior one-third of the tongue.
Works with Cranial Nerve 10, sensory portion of the gag reflex
_ LMN damage – ipsilateral
_ UMN damage - sparing
_ Special Sensory
_ provides taste sensation from the posterior one-third of the tongue

– relating to skeletal muscles (relating to the body)

vagus, sensations to/control the pharynx, larynx, viscera, both

_ Branchial Motor Component BMC (Branchial Efferent)
_ Voluntary control of the following:
_ Striated muscle of the pharynx.
_ Striated muscle of the larynx, except for the stylopharyngeus muscle (CN IX) and the tensor veli palatini muscle (CN V).
_ Palatoglossus muscle of the tongue (the rest of the muscles of the tongue are innervated by CN XII).
_ Three major branches
_ Pharyngeal
_ Superior Laryngeal
_ Recurrent Laryngeal
_ BMC - Pharyngeal Branch – helps with swallowing, constricting and the soft palate muscles, little bit with base of tongue
_ The muscles innervate by the pharyngeal nerve include:
_ Superior, middle, and inferior constrictor muscles
_ Levator palatini muscle
_ Salpingopharyngeus muscle
_ Palatopharyngeus muscle
_ Palatoglossus muscle of the tongue
_ BMC Superior Laryngeal Branch
_ Splits into external & internal branches
_ External serves the inferior constrictor muscle and the cricothyroid muscle (pitch control).
_ Internal branch serves as a sensory nerve for the larynx .
_ BMC Recurrent Laryngeal Branch
_ Innervates all intrinsic laryngeal muscles except for the cricothyroid.
_ Visceral Motor Component
_ Innervates the smooth muscle and glands of the pharynx, larynx, thoracic and abdominal viscera
_ CN X parasympathetic stimulation has the following effects (think "rest and digest"):
_ Cardiac - Slows heart rate
_ Lungs - Stimulates increased bronchiolar secretions and bronchoconstriction
_ GI tract- Stimulates increased secretions and motility
_ Visceral Sensory Component (supports heart beat, blood pressure and respiration)
_ Provides sensory information from the larynx, esophagus, trachea, and abdominal and thoracic viscera, as well as the stretch receptors of the aortic arch and chemoreceptors of the aortic bodies.
_ General Sensory Component (skin around the ear, larynx and pharynx)
_ General sensory information (pain, temperature, and touch) from the skin of the back of the ear and external auditory meatus, parts of the external surface of the tympanic membrane, and the from the larynx and pharynx.
Special Sensory Component
_ Mediate taste from the pharyngeal area (epiglottis)

(towards the brain, sensory)

accessory, activates the sternocleoidmastoid and trapezius, motor

Branchial Motor _ Cranial root
_ Originates in nucleus ambiguous of medulla
_ Join with X nerve fibers in foramen magnum
_ Courses with X nerve and provides part of its motor innervation to pharynx & larynx – thus it is said to be “accessory” to X nerve
Branchial Motor _ Spinal root
_ Originates in the lateral portion of the ventral grey matter of the upper six segments of the spinal cord (C1- C6) – in line with nucleus ambiguous
_ Begins by coursing up (ascending) into skull, joining with cranial root fibers.
_ Splits from cranial root fibers and go on to innervate the trapezius (raises and medially rotates the scapula, tilting head back & to side) & sternocleidomastoid (pulls the mastoid process toward the ipsilateral clavicle resulting in rotation of the head and an upward tilting of the chin to the opposite side )

Turn, tilt, and thrust our head, raises the sternum and clavicle, as well as shoulder shrugging

(GSA) (General Pain is a GSA who is HOT)
_ These fibers are related to the receptors for pain, temperature, and
mechanical stimuli in somatic structures such as skin, muscle and
joints.

hypoglossal, control of tongue movement, motor

_ Innervates all the intrinsic tongue muscles.
_ Innervates ¾ extrinsic tongue muscles –in conjunction with 10 (not palatoglossus – X nerve does that)

– relate to only one sense
_ These fibers are related to the special senses of sight, hearing and
equilibrium.

(exiting the brain, goes to the skeletal muscles)

_ These fibers innervate skeletal muscle (i.e., they are the axons of the
alpha and gamma motor neurons).

relating to functions of respiration, phonation, & digestion

Involuntray system, visceral efferent

_ These fibers are related to the receptors of the visceral structures. Mediates
pain, temperature, touch in the pharynx, palate, larynx, aorta, & abdomen

the periperhal nervous system

)- relate to only one sense.
_ These fibers are related to the special senses of smell and taste.

smooth muscle and glands throughout the body

(Autonomic Nervous System)
_ Autonomic innervation of smooth muscles (heart, trachea, bronchi,
esophagus, lower viscera, pupils, glands)

Sympathetic and Parasympathetic

Also called Branchial Efferent
_ These fibers innervate certain striated muscles.
_ Develop out of branchial arches during embryological development
_ Structures that develop into gill arches in fish develop instead into various
structures near or in the head and neck (muscles of the face, larynx and
pharynx).
_ Although these muscles are identical to normal striated muscle, neurons for
branchiomeric muscles have a distinctive location in the brainstem.

Prepares the body for emergencies or excitement, responsible for the fight or flight stress response

all the corticospinal (from the cortex to the spinal cord) and corticobulbar (from the cortex to the brain stem) tracts, contained within the CNS

Calms the body down, acts opposite of the sympathetice nervous system, conserves body resources and energy

UMN

UMN are within in the CNS, once they leave the system through the cranial or spinal nerves and interface with the muscles or visceral components are deemed LMN

motor neurons in the cranial and spinal nerves; second order neurons; final common pathway

LMN

UMN damage

LMN damage

opposite or contralateral

ipsilateral side (same side)

lower

left hemisphere innervates both the right and left side of the upper face and vice versa of the right side. This allows for SPARING of motor function, in the event of damage to one side. If there is a lesion in the upper left, the upper face will still work because it is also innervated by the right side.

1. Generated and created in cell body/cytoplasm - Synthesis of neurotransmitter(s)
2. Concentration and packing of neurotransmitter within the vesicle and fuse with the presynaptic membrane
3. Release of neurotransmitter into synaptic cleft
4. Binding to receptor molecules postsynaptically (on neighboring dendrite) (ligand process)
5. Termination of action, sometimes enzymes in cleft clean up neurotransmitters left behind, sometimes diffusion happens where the neurotransmitters are absorbed by neighboring cells. Needs to be left a clean slate.