For Exam #2 Flashcards
The nervous system can structurally be divided into what two categories?
central nervous system (CNS)
peripheral nervous system (PNS)
What structures are in the CNS?
brain and spinal cord (protected by cranium, vertebral canal)
What structures are in the PNS?
cranial nerves and spinal nerves
The nervous system can be functionally divided into what three categories?
sensory, motor, and integration components
What does the sensory component do?
carries sensation to the brain and spinal cord
What does the motor component do?
delivers impulses to muscles and glands
What does the integration center do?
helps to process sensory input and organize motor output
The sensory system is divided into what two systems?
somatic sensory system and visceral sensory system
What does the somatic sensory part of the nervous system do?
carries sensory information we are generally aware of (such as touch from the skin, vision, hearing, smells, and taste)
What is the visceral sensory part of the nervous system do?
carries sensory information we are generally not aware of (such as amount of oxygen and carbon dioxide in the blood or the make-up of food traveling through the digestive tract)
What does the somatic motor part of the nervous system do?
delivers impulses to skeletal muscles, which we generally control voluntarily
What does the visceral motor (autonomic) part of the nervous system do?
delivers impulses to cardiac muscle, smooth muscle and glands, which are generally controlled automatically (without conscious effort)
Characteristics of a Neuron
- high metabolic activity requiring constant supply of glucose and oxygen
- not capable of cell division (nonmitotic)
- cell body is control center of cell and contains the nucleus
- prominent nucleolus indicative of high metabolic activity
- large number of mitochondria to produce ATP for energy
What do dendrites do?
carry impulses to cell bodoy
What does the axonal process do?
carries impulse away from cell body
- often myelinated
What is the axon hillock?
where the cell body tapers down to the axon
What are telodendria?
branches at the terminal end of axons
What are on the ends of telodendria?
synaptic knobs that can release neurotransmitters
What are the cells of the nervous system?
neurons
interneurons
glial cells
What are the three structural classification of neurons?
bipolar neurons
unipolar (pseudounipolar) neurons
multipolar neurons
Bipolar Neurons
- have one dendritic process and one axonal process
- found in retina of eye (vision) and olfactory epithelium of nose (smell)
Unipolar (Pseudounipolar) Neurons
- dendritic and axonal processes fuse to form a single process, but still functionally separate
- carry sensation from the SKIN
- dendritic branches have specialized sensory receptors for touch, pressure, vibration, pain, and temperature
- cell bodies located outside the CNS
- axonal processes enter spinal cord posteriorly
- collection of cell bodies is called a ganglion
Multipolar Neurons
- have a single axon and multiple dendritic processes
- function as motor neurons and interneurons
- can have sparsely-branched or extensively-branched dendritic arbors
What are the functional classifications of neurons?
sensory neurons
motor neurons
interneurons
Sensory Neurons (AKA afferents)
- carry sensation from the skin to the CNS
- are unipolar
- their cell bodies form ganglia
- axonal processes enter the brain or spinal cord
Motor Neurons (AKA efferents)
- deliver impulses (motor commands) to muscles and glands
- multipolar
- cell bodies are in the spinal cord (in ventral horns) and their axons project out to their targets
What is a ganglion?
collection of cell bodies in the PNS
Interneurons (AKA association neurons)
- multipolar and entirely located within the CNS, specifically within the gray matter of the spinal cord
- receive information from sensory neurons and “decide” what to do with it
- may decide to send information up to the cerebral cortex for awareness
- may decide to send the information to motor neurons in anterior horn for motor response
Glial Cells (AKA neuroglia = nerve glue)
- provide a wide range of supportive functions in the CNS and PNS (protect, nourihs, and provide supporting networks for neurons)
- smaller and more numerous than neurons
- do not conduct impulses
- capable of cell division
What are the four types of glial cells in the CNS?
astrocytes
ependymal cells
microglia
oligodendrocytes
What are the two types of glial cells in the PNS?
satellite cells
neurolemmocytes (Schwann cells)
Astrocytes
- have processes which extend to neurons and capillaries
- help regulate what leaves the capillaries and enters the interstitial space (around the neurons)
- part of the blood brain barrier
- fill in space left by dead cells to maintain structural integrity of CNS
- release small “bursts” of calcium to influence neuronal activity
What is the blood-brain barrier?
a modification of capillaries in the brain which protects the nervous tissue from substances that could adversely affect brain function
- consists of specializations of the capillaries (tight junctions and continuous basement membrane) and the perivascular feet of astrocytes)
What kinds of substances can diffuse across the blood-brain barrier?
lipid-soluble compounds such as alcohol, nicotine, and some anesthetics
Ependymal Cells
- have somewhat cuboidal shape with cilia
- join capillaries to form choroid plexus (found in ventricles of brain, produces cerebrospinal fluid [CSF])
- the cilia of the ependymal cells help circulate CSF
Function of cerebrospinal fluid (CSF)
provide nourishment and protection for CNS
Microglia
- especially small
- wander through the CNS and clean up debris from dead cells via phagocytosis
Oligodendrocytes
- have multiple projections that project out to nearby axons
- the projections wrap around regions of axons to produce myelin
- myelin increases conduction velocity in neurons
What are gaps in the myelin sheath called?
nodes of Ranvier
- responsible for saltatory conduction (jumping) in axons
What is the only place where reversal of polarity occurs in an axon?
in the nodes of Ranvier
Why is it desirable to insulate some neurons?
insulating them increases the speed that the impulse can travel
Satellite Cells
- located around unipolar cell bodies of dorsal root ganglia
- help deliver nutrients and remove waste products
Neurolemmocytes (Schwann Cells)
- myelinate neuronal processes (motor and sensory) in peripheral nerves
- each neurolemmocyte attaches to a segment of a neuronal process and wraps its cell membrane around it to form myelin
- assists with nerve regeneration
Endoneurium
the connective tissue around a single axon
Perineurium
the connective tissue around a bundle of axons (fascicle)
Epineurium
the connective tissue around a peripheral nerve
When a peripheral nerve is cut, what ends of the nerve processes (both sensory and motor) degenerate?
the distal ends
During nerve regeneration, what happens to the ends of the processes still attached to the cell bodies?
they seal off and swell
During nerve regeneration, the neurolemmocytes for a regenerate rube and secrete what?
nerve growth factor (NGF)
What does nerve growth factor (NGF) do in nerve regeneration?
signals the end of the neuronal process to sprout and extend down the regeneration tube to the muscle or skin
Why is regeneration less likely to occur in the CNS?
- neurons are more tightly packed
- no neurolemmocytes (and therefore no NGF)
- astrocytes tend to fill in the space left by the degenerated neuronal processes
What three things does successful regeneration depend on?
- amount of damage
- secretion of nerve growth factor (NGF) by neurolemmocytes
- distance between damaged axons and target organ
An impulse travels down an axon and its terminal branches as a result of _____ entering the cells and reversing the relative polarity across the cell membrane
sodium
Spinal Cord
- link between the brain and the rest of the body
- protected by vertebral canal and meninges (pia mater, arachnoid mater, and dura mater)
What is located in the subarachnoid space?
cerebrospinal fluid (CSF)
What defines the segments of the spinal cord?
attachment of a pair of spinal nerves
How many cervical segments in the spinal cord?
8
How many thoracic segments in the spinal cord?
12
How many lumbar segments in the spinal cord?
5
How many sacral segments in the spinal cord?
5
Which spinal cord regions are enlarged for the extremities?
cervical and lumbar regions
Where does the spinal cord end?
at the L1 level of the vertebral column as conus medullaris
Cauda Equina
Meaning horse tail; a collection of nerve roots at the end of the spinal cord
Gray matter is on the ____ of the spinal cord while white matter is on the _____.
inside ; outside
Central processes of sensory neurons enter the…
posterior (dorsal) horns
The posterior root ganglia are made of…
sensory (unipolar) neuron cell bodies
Where are the cell bodies of interneurons located?
posterior (dorsal) horns
The cell bodies of motor neurons are located in the…
anterior (ventral) horns
The axons of motor neurons leave the spinal cord ____, forming ________.
anteriorly ; anterior roots
Anterior and posterior roots join to form what?
a spinal nerve
Spinal nerves divide into….
posterior and anterior rami
Posterior Rami
Deliver motor fibers to skeletal muscles along vertebral column and carry sensation from overlying skin
Anterior Rami
Deliver motor fibers to skeletal muscles of the body wall and extremities, as well as carry sensation from skin of body wall and extremities
Nerve Plexuses
joining of anterior rami to form nerves comprised of more than one level of the spinal cord
Where are nerve plexuses found and why?
The upper and lower extremities, because they perform complex, graded functions
What are the two largest nerve plexuses?
brachial plexus and lumbosacral plexus
Brachial Plexus
delivers motor to, and sensory from, the upper extremity
Lumbosacral Plexus
delivers motor to, and sensory from, the lower extremity
What forms the brachial plexus?
anterior rami of spinal nerves C5-T1
Where is the brachial plexus?
it extendsf rom the lower neck, between the clavicle and 1st rib, and then into the axilla.
What does the brachial plexus do?
Innervates the skeletal muscles of the upper extremity and carries sensation from the skin of the upper extremity
Anterior rami of C5 and C6 join to form…
the superior trunk
Anterior rami of C8 and T1 join to form…
the inferior trunk
Anterior ramus of C7 forms…
the middle trunk
The posterior branches of all 3 brachial plexus trunks form…
the posterior cord
The anterior branches of the superior and middle brachial plexus trunks form…
the lateral cord
The anterior branch of the brachial plexus’s inferior trunk forms…
the medial cord
The posterior cord gives rise to what nerves?
radial and axillary
The lateral cord gives rise to…
the musculocutaneous nerve and part of the median nerve
The medial cord gives rise to the…
ulnar nerve and part of the medial nerve.
Axillary Nerve
- spinal cord levels C5 and C6
- motor signals to deltoid and teres minor
Main Function of Axillary Nerve
abduction and external rotation of the arm
responsible for sensation from skin of lateral shoulder
Musculoskeletal Nerve
- spinal cord levels C5-C7
- motor signal to biceps brachii, corachobracialis, and brachialis
Main Function of Musculoskeletal
flexion at the elbow
sensation of skin of lateral forearm
Radial Nerve
- spinal cord levels C5-T1
- motor signals to triceps, anconeous, brachioradialis, extensory carpi ulnaris, supinator, abductor pollicis longus, extensor pollicis brevis, extensory pollicis longus, and extensory indicis
Main Function of Radial Nerve
extension at the elbow, wrist and fingers
sensation from skin of posterior arm, forearm, and hand
Median Nerve
- spinal cord levels C6-T1
- motor signals to pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus (1/2), pronator quadratus, thenar muscles, and 2 lumbricals
Main Functions of Median Nerve
flexion at wrist and fingers, pronation
sensation from skin of lateral palm, thumb, index finger, middle finger, and 1/2 of ring finger
Ulnar Nerve
- spinal cord levels C8-T1
- motor singals to flexor carpi ulnaris, flexor digitorum profundus (1/2), hypothenar muscles, intercossei and 2 lumbricals
Main Functions of Ulnar Nerve
abduction and adduction of fingers
sensation from skin of medial palm, little finger, and 1/2 of ring finger
What are the smaller branches of the brachial plexus?
long thoracic nerve suprascapular nerve upper subscapular nerve middle subscapular nerve lower subscapular nerve
Long Thoracic Nerve
from nerve roots to the serratus anterior
stabilizes scapula, responsible for upward rotation of scapula
Suprascapular Nerve
to supraspinatus and infraspinatus for abduction and lateral rotation at the shoulder, respectively
Upper Subscapular Nerve
to subscapularis for internal rotation at shoulder
Middle Subscapular (Thoracodorsal) Nerve
to latissimus dorsi for adduciton, extnesion, and medial rotation of arm (at shoulder)
Lower Subscapular Nerve
to subscapularis (for medial rotation at shoulder) and teres major (for adduction, extension, and medial rotation at shoulder)
What nerves are in the lumbosacral plexus?
femoral nerve
obturator nerve
iliohypogastricnerve
ilioinguinal nerve
Femoral Nerve
spinal cord levels: L2-L4
motor to flexor iliopsoas and quadriceps
Main Function of Femoral Nerve
flex the hip, extend the leg
Where does the femoral nerve get sensation?
skin of anterior thigh, medial leg
Obturator Nerve
spinal cord levels: L2-L4
motor to adductor adductor longus, adductor brevis, adductor magnus, and gracilis
Main Function of Obturator Nerve
adduct the thigh
Where does the obturator nerve get sensations?
from skin of superior-medial thigh
Tibial nerve is formed by…
anterior branches of L4-S3
The common fibular nerve is formed by…
posterior branches of L4-S2
The superior gluteal nerve is formed by…
posterior branches of L4, L5, and S1
The inferior gluteal nerve is formed by…
posterior branches of L5, S1, and S2
What is the superior gluteal nerve a motor to?
gluteus medius, gluteus minimus, and tensor fasciae latae
Main Function of Superior Gluteal Nerve
abduction and medial rotation at the hip
What is the inferior gluteal nerve a motor to?
gluteus maximus
Main Functions of Inferior Gluteal Nerve
extension and lateral rotation at the hip
What is the tibial nerve a motor to?
long head of biceps femoris, semitendinosus, semimembranosus, fastrocnemius, soleus, flexor hallucis longus, tibialis posterior, flexor digitorum longus and muscles of the foot.
Main Function of Tibial Nerve
extend the thigh, flex the leg, plantarflex the foot and flex the toe
Where does the tibial nerve get sensations?
skin of sole of the foot
What is the common fibular (peroneal) nerve a motor to?
to short head of biceps femoris- helps to flex the leg
What is the superficial fibular (peroneal) nerve a motor to?
fibularis (peroneous) longus and brevis
Main Function of Superficial Fibular Nerve
evert foot
Where does the superficial fibular nerve get sensations?
skin of dorsal foot except between first two toes
What is the deep fibular (peroneal) nerve a motor to?
tibialis anterior, extensor digitorum longus and extensor hallucis longus
Main Function of Deep Fibular (Peroneal) Nerve
dorsiflex and invert the foot, extend the toes
Where does the deep fibular nerve receive sensations?
from skin of between first two toes
The common fibular nerve divides into what?
the superficial fibular nerve (goes to lateral compartment) and the deep fibular nerve (goes to anterior compartment)
Reflex
Type of motor response that occurs as the result of some type of sensory stimuli that takes place without conscious control.
Monosynaptic (Stretch) Reflex
- simplest type of reflex
- quick stretch to a skeletal muscle tendon
- involves a sensory neuron synapsing directly on a motor neuron, and the motor (efferent) neuron causes the muscle that was stretched to contract
Polysynaptic Reflex
- involves 3 neurons in series
- the sensory (afferent) neuron carries painful stimulus from skin to spinal cord, synapsing with several interneurons in the posterior horn, who then recruit several muscles in order to remove skin from the stimulus
What type of reflex is being test when your physician taps you on the patellar tendon with a reflex hammer and your leg kicks?
Monosynaptic
What type of reflex is responsible for quickly removing your hand when you accidentally touch a hot stove?
Polysynaptic
The nervous system begins development as a…
neural tube
At the 4th week of development, the cranial end of the neural tub develops 3 dilations, or primary vesicles, called:
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
At the 5th week, the primary vesicles further specialize into secondary vesicles:
prosencephalon → telencephalon and diencephalon
mesencephalon stays the same
rhombencephalon → metencephalon and myelencephalon
The mesencephalon gives rise to what completed structure?
midbrain
The prosencephalon and its secondary vesicles give rise to what completed structures?
cerebrum, thalamus, hypothalamus, epithalamus
The rhomencephlon and its secondary vesicles give rise to what completed features?
pons, cerebellum, medulla oblongata
In the brain, the front of the brain is called the ____ part.
anterior
In the brain, the back of the brain is called the ____ part.
posterior
In the brain, the superior part of the brain is called the _____ part.
dorsal
In the brain, the inferior part of the brain is called the ______ part.
ventral
Longitudinal Fissure
Separates left and right hemispheres of brain
What does the cerebrum do?
- location of conscious thought and complex intellectual function
- allows us to comprehend the world around us
- house the centers of reasoning as well as memories
- allow us to be aware of sensory input and initiate motor activity
The meningeal layer of the dura matter separates from the periosteal layer to form what structures?
falx cerebri
falx cerebelli
tentorium cerebelli
The cavernous sinuses receive blood from the…
opthalmic veins in the orbit
The sigmoid sinus drains into the…
internal jugular vein
What sinus carries blood from the front of the brain to the back of the brain?
the superior sagittal sinus
Many veins empty into the…
confluence of sinuses
Ventricles are responsible for…
production of cerebrospinal fluid (CSF)
What is the flow of CSF in the brain?
- lateral ventricles
- 3rd ventricle
- 4th ventricle
- subarachnoid space, some goes to central canal
What specifically within the ventricles creates CSF?
the choroid plexus (type of capillary)
What cells are in the choroid plexus that allow it to create CSF?
ependymal cells
Purpose of the CSF
nourishment for the brain, shock absorbent
Interventricular Foramina
connections between lateral ventricles and 3rd ventricle
Mesencephalic aqueduct
connection (through midbrain) between 3rd and 4th ventricle
Central Canal
narrow canal through center of
Apertures
Openings in 4th ventricle that allow CSF to flow into subarachnoid space
Where does the CSF return to the blood?
superior sagittal sinus
Hydrocephalus
Brain swells d/t build up of pressure within, and the enlargement of, ventricles. Caused by congenitally malformed ventricular system, blockage of a passageway, or defective drainage through arachnoid villi
Arachnoid Villi
one-way valves that project from subarachnoid space into superior sagittal sinus, allowing CSF to enter sinus, keeping blood out
Fissure
long groove or crease
What are the major lobes of the brain?
frotal parietal temporal occipital insula
Central Sulcus
between frontal and parietal lobes
Parieto-Occipital Sulcus
between parietal and occipital lobes
Lateral fissure
defines temporal lobe
What does the primary motor cortex control?
skeletal muscle activity on the opposite side of the body
Where is the primary motor cortex?
precentral gyrus
What does the premotor cortex do?
causes groups of muscles to contract in a specific sequence (which becomes more efficient with practice)
Commissural Tracts
connect the two hemispheres of the brain
- corpus callosum
Which hemisphere is Broca’s area in?
left side, in premotor area
What does the Broca’s area do?
ability to speak and write so others can understand
What does the frontal eye field do?
regulates eye movements needed for reading and binocular vision
Where is the primary somatosensory cortex?
postcentral gyrus
What does the primary somatosensory cortex do?
receives sensation from the skin on the opposite side of the body
What does the somatosensory association cortex do?
integrates the qualities of the sensory information coming into the primary somatosensory cortex in order to identify everyday objects without having to look at them
What does the primary visual cortex do?
process incoming visual information
Where is the primary visual cortex?
occipital lobe
What does the visual association cortex do?
takes the visual information entering the primary visual cortex and allows us to recognize what an object is (or what it represents)
Where is the primary olfactory cortex?
temporal lobe
What does the primary olfactory cortex do?
provides for conscious awareness of smells
Where is the primary auditory cortex?
temporal lobe
What does the primary auditory cortex do?
receives and processes auditory information
Where is the primary gustatory cortex?
in the insula
What does the primary gustatory cortex do?
processes taste information
Where is Wernicke’s area?
left hemisphere
What does Wernicke’s area do?
involved in understanding written and spoken language
- has gnostic area that is responsible for integrating all sensory information in order to provide context to your environment
What is included in the limbic system?
cingulate gyrus
hippocampus
amygdaloid body
mammillary bodies
Where is the limbic system located?
lateral aspects of the hemispheres
What does the limbic system do?
process and experience emotions (and memories tied to emotions)
What are the higher order functions of the brain?
learning
memory
reasoning
consciousness
The left side of the brain tends to handle…
language, math, and reasoning
The right side of the brain tends to handle…
imagination, artistic ability, and insight
Where do higher order functions of the brain occur?
cerebral cortex
Projection Tracts
link the hemispheres within the brainstem and spinal cord
What is included in the diencephalon?
thalamus, hypothalamus, and epithalamus
The diencephalon forms the walls of what?
the third ventricle
What does the thalamus do?
receives, filters, and relays somatosensory information to cerebral cortex (except smells)
What are some functions of the hypothalamus?
- master controller of autonomic nervous system
- master controller of endocrine system
- regulates food and water intake
- has connection with limbic system to control emotions
- directs the pineal gland when to secrete melatonin
What does the epithalamus do?
houses pineal gland to secrete the hormone melatonin to regulate one’s sleep-wake cycle (circadian rhythm)
What does the brainstem include?
midbrain
pons
medulla oblongata
What is another name for the midbrain?
mesencephalon
What runs through the midbrain?
cerebral (mesencephalic) aqueduct
What are the “pillars” in the front of the midbrain called?
cerebral peduncles
The midbrain has substantia nigra, which contain what?
neurons which contain melanin granules and produce the neurotransmitter dopamine
What disease is associated with the degeneration of the substantia nigra?
Parkinson’s
What do the superior colliculi of the midbrain do?
visually track moving objects
What do the inferior colliculi of the midbrain do?
orient our sense to sound
Both the pons and the medulla oblongata control what?
respiratory center
In addition to the respiratory center, the medulla also controls what?
the cardiac center that controls heart’s rate and force of contraction
Instead of gyri, the cerebellum has folds called…
folia
What does the cerebellum do?
- refine skeletal muscle movements so the motion is smooth and coordinated
- receives proprioceptive input from skeletal muscles to be aware of the position of the body parts (without having to see them)
Ataxia
uncoordinated, jerky movements due to impaired cerebellar function
How many pairs of cranial nerves are there?
12
Cranial nerves are part of what nervous system?
peripheral nervous system
Most cranial nerves originate from the brainstem, but the first two pairs originate from…
the prosencephalon
Olfactory Nerve (CN I)
- sensory only
- exits skull through cribriform plate of ethmoid bone
- carries sense of smell from nasal cavity to temporal lobe
Optic Nerve (CN II)
- sensory only
- exits skull through optic canals
- carries visual information from retina to thalamus
Oculomotor Nerve (CN III)
- motor only
- exits skull through superior orbital fissure
- innervates EYE MUSCLES: superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris with somatic motor fibers
- innervates smooth muscle of pupil and lens with parasympathetic fibers
Trochlear Nerve (CN IV)
- motor only
- exits skull through superior orbital fissure
- innervates superior oblique eye muscle with somatic motor fibers
What are the 3 divisions of the trigeminal nerve (CN V)?
- ophthalmic division (V1)
- maxillary division (V2)
- mandibular division (V3)
Ophthalmic Division (V1)
- sensory only
- exits skull through superior orbital fissure
- carries sensation from face, cornea, and sinuses
The superior oblique of the eye is innervated by which cranial nerve?
CN IV
The lateral rectus of the eye is innervated by which cranial nerve?
CN VI
With the exception of the superior oblique and lateral rectus, the orbit is innervated by which cranial nerve?
CN III
Maxillary Division (V2)
- sensory only
- exits skull through foramen rotundum
- carries sensation from face, nasal cavity, upper teeth, palate, and sinuses
Mandibular Division (V3)
- sensory and motor
- exits skull through foramen ovale
- carries sensation from face, lower teeth, and anterior 2/3 of tongue
- innervates muscles of mastication with somatic nerve fibers
Abducens Nerve (CN VI)
- motor only
- exits skull through superior orbital fissure
- innervates lateral rectus with somatic motor fibers
Facial Nerve (CN VII)
- sensory and motor
- exits skull through internal auditory meatus
- innervates muscles of facial expression with somatic motor fibers
- carries taste from anterior 2/3 of tongue
- innervates lacrimal gland, submandibular gland, and sublingual gland with parasympathetic fibers
Vestibulocochlear Nerve (CN VIII)
- sensory only
- exits skull through internal auditory meatus
- carries hearing and balance from inner ear
Glossopharyngeal Nerve (CN IX)
- sensory and motor
- exits skull through jugular foramen
- carries general sensation from posterior 1/3 of tongue
- carries taste from posterior 1/3 of tongue
- innervates parotid glands with parasympathetic fibers
Vagus Nerve (CN X)
- sensory and motor
- exits skull through jugular foramen
- innervates muscles of pharynx and larynx with somatic motor fibers (for swallowing and talking)
- innervates thoracic and abdominal organs with parasympathetic fibers
- carries sensation from heart, lungs, and abdominal organs
Accessory Nerve (CN XI)
- motor only
- exits skull through jugular foramen
- innervates sternocleidomastoid and trapezius with somatic motor fibers
Hypoglossal Nerve (CN XII)
- motor only
- exits skull through hypoglossal foramen
- innervates muscles of tongue with somatic muscle fibers
