Lab 7: The Brain

Question 1

the brain

Answer 1

• control center of the CNS
• occupies the endocranial cavity of the skull and is continuous through the foramen magnum with the spinal cord
• peripheral nerves of the brain are known as cranial nerves
• brain is enclosed by the same 3 layers of meninges that are continuous around the spinal cord (dura, arachnoid, pia mater)
• CSF occupies the subarachnoid space around the brain and spinal cord -> produced and circulates in hollow, interconnected ventricles within the brain
• brain has myelinated and unmyelinated neurons (clusters of nerve cell bodies) and support cells (neuroglia)
• 3 components:
• rhombencephalon
• mesencephalon
• prosencephalon

Question 2

grey matter

Answer 2

-consists of neuron cell bodies and unmyelinated fibers that occupy the outer, convoluted layer of the cerebrum and cerebellum

Question 3

white matter

Answer 3

• comprises myelinated axons that form fiber tracts deep to the cortex
• basal nuclei (clusters of grey mater) are formed by nerve cell bodies and lie deep within the white matter

Question 4

basal nuclei

Answer 4

• cluster of grey mater
• formed by nerve cell bodies
• lie deep within the white matter

Question 5

rhombencephalon

Answer 5

• aka hindbrain
• comprises the medulla oblongata, pons, cerebellum, tegmentum
• houses the fourth ventricle
• has the metencephalon

Question 6

mesencephalon

Answer 6

• aka the midbrain
• a stalk of white matter connecting the rhombencephalon and prosencephalon
• contains:
• superior and inferior colliculi
• cerebral peduncles (crura cerebri)
• cerebral aqueduct- connects the third and fourth ventricle
• tegmentum

Question 7

prosencephalon

Answer 7

• aka the forebrain
• contains: cerebral cortex, white matter, basal ganglia, lateral ventricle
• comprises the diencephalon and cerebrum (telencephalon)
• diencephalon comprises the thalamus and surrounds the third ventricle
• cerebrum is composed of 2 large hemispheres connected to one another by the corpus callosum
• each hemisphere has a cortex of gray matter abundant in white matter, a core basal nuclei, and a lateral ventricle

Question 8

Rhombencephalon: medulla oblongata

Answer 8

• myelencephalon
• contains: pyramids, pyramidal decussation, cuneate and gracile fasiculus
• one of the 3 parts of the brain stem (other 2 are pons and midbrain)
• all cranial nerves except 1 and 2 emerge from the brain stem
• medulla oblongata is continuous with the spinal cord and contains the cardiac, vasomotor, and respiratory nerve centers
• regulates vomiting, breathing, sneezing, coughing, and swallowing and monitors the level of carbon dioxide in the blood
• continuous with the pons superiorly
• connected to the cerebellum by the inferior cerebellar peduncle
• lateral surfaces of the medulla are swollen to form the olives

Question 9

olives

Answer 9

• lateral surfaces of the medulla that are swollen
• mediate impulses that pass from the forebrain and midbrain to the cerebellum by way of the inferior cerebellar peduncles

Question 10

pyramids

Answer 10

• the ventral surface of the medulla oblongata that is elevated into the 2 parallel ridges
• carry motor nerve fibers from the prosencephalon to the spinal cord
• almost all these fibers cross over (decussate) just distal to the pyramids at the pyramidal decussation
• this decussation is responsible for the face that the left side of the brain controls body movements on the right side (vice versa)

Question 11

rhombencephalon: pons

Answer 11

• bridge between the medulla oblongata and the midbrain
• dorsal surface forms the floor of a space known as the fourth ventricle of the brain
• connected to the cerebellum by the middle cerebellar peduncle

Question 12

rhombencephalon: cerebellum

Answer 12

• makes up a large part of the brain
• wedged between the brain stem and the back of the cerebrum
• functions relate to balance, timing and precision (coordination) of movements, and body posture
• divided into 3 parts: midline vermis, two small flocculonodular lobes (involved in the maintenance of skeletal muscle tone), and 2 large lateral loves (corpus cerebelli) that synchronize the precise timing of skeletal muscle contractions
• cerebellar cortex consists of a surface layer of gray matter and is corrugated, with numerous parallel ridges (folia cerebelli) separate by shallow fissures
• underlying white matter of cerebellar cortex has a branching arrangement known as the arbor vitae
• cerebellum is connect to the medulla oblongata by the inferior cerebellar peduncle, pons by middle cerebellar peduncle, and midbrain by the superior cerebellar peduncle

Question 13

mesencephalon: midbrain

Answer 13

• short section of the brain stem that connects the rhombencephalon and prosencephalon
• passes through the notch in the dural sheet known as the tentorium cerebelli
• comprises 2 ventrolateral halves called the crura cerebri
• ventral portion of the crura are known as the cerebral peduncles
• these masses of white matter serve as the fiber tracts that convey all somatic motor impulses between the cerebral cortex and the spinal cord
• between the slightly posterior to the cerebral peduncles runs a hollow, fluid-filled canal called the cerebral aqueduct -> connects the third and fourth ventricles
• dorsal surface of the midbrain is known as the tectum -> has 4 bumps called the colliculi which are nerve reflex centers
• midbrain contains the substantia nigra, a nucleus that is functionally connected to the basal nuclei

Question 14

colliculi

Answer 14

• on the dorsal surface of the midbrain (tectum)
• 4 small bumps
• nerve reflex centers
• 2 superior colliculi are related to the eyes -> involved in the coordination of eye movements as well as focusing and pupillary response
• 2 inferior colliculi are related to the ears/auditory reflex
• 4 colliculi together constitute the corpora quadrigemina

Question 15

prosencephalon: diencephalon

Answer 15

• lies deep within the prosencephalon, forming the walls and floor of the third ventricle
• comprises the:
• thalamus
• epithalamus (pineal gland)
• hypothalamus
• subthalamus
• optic chiasm
• mammillary bodies
• 3rd ventricle

Question 16

prosencephalon: diencephalon: thalamus

Answer 16

• egg shaped mass of gray matter
• constitutes most of the lateral wall of the third ventricle
• left and right thalami are joined by the interthalamic adhesion
• thalami serve as relay points and processing center for all sensory impulses (except olfaction)

Question 17

prosencephalon: diencephalon: hypothalamus

Answer 17

• lies directly below and somewhat anterior to the thalamus, forming the floor and lower walls of the third ventricle
• has a number of nuclei, including the 2 mamillary bodies
• mammillary bodies project inferiorly between the cerebral peduncles of the midbrain and the optic chiasm (limbic system)
• the hypophysis (pituitary gland) extends inferiorly from the hypothalamus by the infundibulum
• the pituitary gland functions largely in the regulation of other endocrine glands
• hypothalamus is important in a number of functions, including the modification of autonomic responses (blood pressure, heart beat), body temperature regulation, maintenance of electrolyte balance, and the expression of emotional behaviors

Question 18

prosencephalon: diencephalon: subthalamus

Answer 18

• located below the thalamus and behind the mamillary body

- regulates and modulates the output of the basal nuclei

Question 19

prosencephalon: diencephalon: pineal gland

Answer 19

• occupies the caudal part of the roof of the third ventricle
• this is an endocrine gland of regulatory (generally inhibitory) importance

Question 20

prosencephalon: cerebrum

Answer 20

• telencephalon
• the largest part of the brain, accounting for 85% of its tissue
• comprises of 2 cerebral hemispheres that are connected to one another by the corpus callosum, a narrow band of transverse fibers
• each hemispheres has a cortex of gray matter, abundant white matter comprising the fiber tracts, and a deep core of gray matter called the basal nuclei

Question 21

prosencephalon: cerebral cortex

Answer 21

• a thin layer of gray matter that is convoluted by ridges (gyri) and shallow grooves (sulci)
• divided into 5 lobes (4 are named according to the skull bone that covers them): temporal, frontal, parietal, occipital, limbic lobe
• several gyri and sulci are important enough to be named
• frontal lobe is separate from the parietal lobe by the central sulcus
• frontal and parietal lobes are separated from the temporal lobe by the lateral (sylvian) sulcus
• occipital lobe is separated from the parietal and temporal by arbitrary lines that meet dorsally at the parietooccipital sulcus
• parietal lobe is involved in the sensation of taste

Question 22

cerebral cortex: frontal lobe

Answer 22

• frontal lobe is separate from the parietal lobe by the central sulcus
• frontal and parietal lobes are separated from the temporal lobe by the lateral (sylvian) sulcus
• precentral gyrus is apart of the frontal lobe
• precentral gyrus is located immediately anterior to the central sulcus
• precentral gyrus contains the primary motor cortex which controls all voluntary skeletal muscles movement
• frontal love is also involved in speech

Question 23

cerebral cortex: parietal lobe: postcentral gyrus

Answer 23

• in the parietal love
• located immediately behind the central sulcus
• contains the primary sensory motor cortex -> receives sensory information from receptors throughout the body
• parietal lobe is involved in the sensation of taste

Question 24

temporal lobe

Answer 24

-involved in hearing and equilibrium

Question 25

occipital lobe

Answer 25

-processes visual information and is related to our understanding of the written word

Question 26

insula

Answer 26

-a small region of cortex located within the lateral sulcus

Question 27

limbic lobe

Answer 27

- comprises several gyri surrounding the corpus callosum and third ventricle on the medial surface of the cerebral hemisphere - these gyri are the cingulate gyrus, isthmus, parahippocampal gyrus, and uncus

Question 28

white matter

Answer 28

- the mass of the cerebrum is composed of myelinated fibers that create a core of white matter - these nerves fibers follow numerous tracts that lead from one place to another - 3 types of fiber tracts: - association fibers- connect area of the cerebral cortex to one another within the same hemisphere - commissural fibers- connect corresponding areas of the cerebral cortex between the two hemispheres -> these traverse the corpus callosum - projection fibers- connect areas of the cerebral cortex to other regions of the brain and to the spinal cord - corticospinal tract, which runs from the precentral gyrus through the crura cerebri of the midbrain and medullary pyramids of the medulla oblongata into the spinal cord, is composed of projection fibers

Question 29

basal nuclei

Answer 29

- aggregations of neuron cell bodies within the white matter of the cerebrum - functionally associated with other parts of the cerebrum in the production and control of motor responses - initiate voluntary movements and are involved in the slow skeletal muscle contractions, such as those employed in posture and balance (arm swinging, while walking) - some also seem to be involved in cognitive functions - lesions to these nuclei result in a variety of motor dysfunctions, such as parkinsons disease and huntingtons disease - structures that are functionally linked to basal nuclei are: substantia nigra (midbrain nucleus), the subthalamic nucleus, and red nucleus - 3 main components of basal nuclei that comprise the corpus striatum: - caudate nucleus, putamen, globus pallidus

Question 30

basal nuclei: caudate nucleus

Answer 30

- curved like a C - superior part is known as the head - inferior part is the tail - a component that comprises the corpus striatum

Question 31

basal nuclei: putamen and globus pallidus

Answer 31

- constitute the lentiform nucleus - putamen comprises its lateral portion - globus pallidus makes up its medial portion - lentiform nucleus lies along the dorsolateral side of the tail of the caudate nucleus

Question 32

ventricles and cerebrospinal fluid

Answer 32

- brain and spinal cord are protected against physical injury by the CSF -> serves to buoy and cushion them - CSF circulates in the subarachnoid space (space between pia and arachnoid mater) - CSF is produced in the hollow ventricles within the brain by a network of capillaries and epithelial tissue called the choroid plexus

Question 33

ventricular system

Answer 33

- 4 ventricles - 2 lateral ventricles occupy space within the cerebrum: C shaped - anterior part is separated from its opposite by a thin vertical partition, the septum pellucidum - the upper part runs below the corpus callosum and above the thalamus, and it extends as a posterior horn into the occipital love of the cerebrum - inferior part of the C extends anterolaterally into the temporal lobe - the caudate nucleus forms the lateral wall of the lateral ventricle - the two lateral ventricles communicate by the interventricular foramen with the midline third ventricle - this occupies a narrow cleft between the left and right thalami - choroid plexus on the roof of the third ventricle is continuous with that on the floor of the lateral ventricles - third ventricle is connected by the narrow cerebral aqueduct to the midline fourth ventricle -> occupies the space between the dorsum of the pons and medulla and the overlying cerebellum - at the junction of the pons and medulla there are 2 lateral apertures, and below the cerebellum there is a midline median aperture in the roof of the fourth ventricle - it is through these apertures that the ventricular system becomes continuous with the subarachnoid space - fourth ventricle is continuous distally with the central canal of the medulla oblongata and spinal cord

Question 34

CSF production, circulation, and resorption

Answer 34

- CSF is produced by aggregates of the choroid plexus in the roof of the temporal limb of the lateral ventricle, the floor of the parietal limb of the lateral ventricle, the roof of the third ventricle, and the roof of the fourth ventricle - form the lateral ventricles, the CSF passes through the interventricular foramina into the third ventricle - from the third ventricle, the CSF passes through the cerebral aqueduct into the fourth ventricle - from the fourth ventricle, the CSF flows out into the subarachnoid space via the lateral apertures and the median aperture - CSF circulates around the brain and spinal cord in the subarachnoid space - it is gradually reabsorbed from this space into the vascular system by means of the arachnoid villi -> finger-like extensions of the arachnoid mater that project into the superior sagittal sinus

Question 35

cranial nerves

Answer 35

- 12 - peripheral nerves that emanate directly from the brain - numbers based on exit the brain from anterior to posterior - all emerge from the brain stem except 1 (olfactory) and 2 (optic) which derive from the cerebrum 1. olfactory 2. optic 3. oculomotor 4. trochlear 5. trigeminal 6. abducens 7. facial 8. vestibulocochlear 9. glossopharyngeal 10. vagus 11. accessory 12. hypoglossal

Question 36

purely sensory cranial nerves

Answer 36

1. olfactory 2. optic 8. vestibulocochlear

Question 37

PRIMARILY motor cranial nerves

Answer 37

3. oculomotor (also parasympathetic fibers to peripheral ganglia) 4. trochlear 6. abducens 11. accessory 12. hypoglossal

Question 38

mixed cranial nerves

Answer 38

5. trigeminal 7. facial (also parasympathetic fibers to peripheral ganglia) 9. glossopharyngeal (also parasympathetic fibers to peripheral ganglia) 10. vagus (also parasympathetic fibers to peripheral ganglia)

Question 39

olfactory nerve (CN I)

Answer 39

- carries sensory (smell) information from receptors in the olfactory epithelium in the upper part of the nasal cavity - axons from these cells form numerous bundles that pierce the cribriform plate* of the ethmoid bone - the nerves then enter the olfactory bulb where they synapse - postsynaptic fibers travel into the brain along the olfactory tracts - olfactory tracts and bulbs are part of the cerebrum

Question 40

optic nerve (CN II)

Answer 40

- carries sensory (vision) information from receptors in the retina of the eye - nerves pass back through the optic canal* of the sphenoid bone and then converge at the optic chiasm anterior to the hypophyseal fossa - at the topic chiasm fibers from each nerve cross over to join the optic tract on the opposite side to pass back to the thalamus - receptors in the medial half of each retina receive information from the temporal visual field - axons from these receptors in each eye cross over to the opposite side at the optic chiasm - synapse at the lateral gericulate body - information from the temporal visual field is relayed to the opposite side of the brain - receptors in the lateral half of each retina receive information from the nasal visual field - axons from these receptors do not cross over at the chiasm - information from the nasal visual field is relayed to the same side of the brain - perception of visual stimuli occurs in the occipital lobe of the cerebrum

Question 41

oculomotor nerve (CN III)

Answer 41

- somatic motor and parasympathetic - carries motor information to the muscle that raises the upper eyelid (levator palpebrae, superioris) - it also carries motor information to 5 of the 6 muscles that move the eyeball (superior rectus, medial rectus, inferior rectus, inferior oblique) - this nerve also conveys parasympathetic fibers to two of the intrinsic muscles of the eye: the ciliary muscle (controls focus of the lens), and the constrictor pupillae of the iris (contracts to constrict the pupil under bright light) - the parasympathetic axons leave the oculomotor nerve and synapse in the ciliary ganglion which lies next to the optic nerve - short ciliary nerve then innervate the eyes (relax) - oculomotor nerve enters the orbit via the superior orbital fissure

Question 42

trochlear nerve (CN IV)

Answer 42

- somatic motor to superior oblique muscle - carries motor information to one of the six muscles that move the eyeball (superior oblique) - enter the orbit with the oculomotor nerve via the superior orbital fissure

Question 43

abducens nerve (CN VI)

Answer 43

- somatic motor to lateral rectus muscle - abducts the eye - carries motor fibers to one of the six muscles that move the eyeball (lateral rectus) - enter the orbit through the superior orbital fissure

Question 44

trigeminal nerve (CN V)

Answer 44

- is mixed, conveying both sensory and motor fibers - sensory neurons have their cell bodies in a very large ganglion (trigeminal ganglion) that lies on the floor of the greater wing of the sphenoid - it is equivalent to the dorsal root ganglion of a spinal nerve - both sensory and motor fibers pass through this ganglion - three divisions: - V1- ophthalmic (purely sensory) - V2- maxillary (purely sensory) - V3- mandibular (mixed somatic sensory and somatic motor)

Question 45

trigeminal nerve: ophthalmic division (CN V1)

Answer 45

- somatic sensory from skin of upper face, forehead, conjuctiva, cornea, and part of nasal sinuses - exits the cranial cavity through the superior orbital fissure - supplies the cornea of the eye, the nasal cavity and sinuses, and the skin of the forehead, eyelids, and middle of the nose - one of its branches, the supraorbital nerve, exits the orbit via the supraorbital foramen (notch) to reach the forehead - goes through supraorbital foramen and then through the superior orbital fissure -> to the brainstem

Question 46

trigeminal nerve: maxillary division (CN V2)

Answer 46

- somatic sensory from skin of midface, nasal cavity, maxillary sinuses, palate, upper teeth - exits the cranial cavity through the foramen rotundum - supplies the skin of the cheek and upper lip, the nasal cavity, maxillary sinus and the upper teeth - one of its branches, the infraorbital nerve, reaches the face by exiting the maxilla through the infraorbital foramen - goes through the foramen rotundum, inferior orbital fissure, infraorbital foramen - Gives off 5 nerves: infraorbital nerve (sensory innervation to cheek), superior alveolar nerve (teeth), greater palatine nerve (palate), lesser palatine nerve (palate), nasopalatine nerve

Question 47

trigeminal nerve: mandibular division (CN V3)

Answer 47

- exits the cranial cavity through the foramen ovale - carries motor fibers that serve the muscles of mastication as well as the mylohyoid, tensor palatini, and tensor tympani muscles - conveys sensation but not taste, from the mucosa of the mouth and tongue via one of its principle branches, the lingual nerve - conveys sensation from the teeth, lower lip, and skin over the mandible via the inferior alveolar nerve which enters the mandible through the mandibular foramen and exits it through the mental foramen to become the mental nerve - its supplies sensation rom the ear and the skin above it by the auriculotemporal nerve which emerges behind the neck of the mandible - 4 muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid - innervates mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini

Question 48

facial nerve (CN VII)

Answer 48

- mixed - conveying both sensory and visceral motor information (parasympathetic) - carries sensory (taste) fibers from the anterior two-thirds of the tongue and motor fibers to the muscles of facial expression - also conveys parasympathetic fibers to the lacrimal and salivary glands - enter the petrous portion of the temporal bone via the internal acoustic meatus - travels through the bone for a short distance, where it encounters the geniculate ganglion - this is the location of the cell bodies of its sensory neurons - at the geniculate ganglion, the facial nerve gives off a branch, the greater petrosal nerve - soon after the geniculate ganglion, the facial nerve gives off a second branch, the chorda tympani - somatic motor- muscles of facial expression, posterior belly of digastric, stylohyoid, and stapedius -> exits the skull via internal acoustic meatus and stylomastoid foramen -> forms the parotid plexus - parotid plexus innervates the facial muscles (zygomatic branches, buccal branches, marginal mandibular branch, temporal branches, cervical branch, posterior auricular nerve)

Question 49

facial nerves (CN VII): greater petrosal

Answer 49

-carries parasympathetic fibers -emerges from the front of the petrous bone into the middle cranial fossa, which it then exits through the cartilage of the foramen lacerum -it then runs anteriorly through a channel in the sphenoid bone at the root of the medial pterygoid plate (the pterygoid canal) to synapse in the pterygopalatine ganglion -postganglionic fibers then pass into the orbit via the inferior orbital fissure to supply the lacrimal gland -submandibular and sublingual salivary glands (via chorda tympani) -

Question 50

facial nerves (CN VII): chorda tympani

Answer 50

- carries sensory (taste) and parasympathetic fibers - anterior 2/3 of tongue - it leaves the temporal bone through a narrow slit between the petrosal and tympanic plate next to the jaw joint - it then travels in company with the lingual nerve, which is a branch of the mandibular division of the trigeminal (V3) - sensory fibers run with V3 into the tongue, conveying taste from its anterior two-thirds - its parasympathetic fibers leave V3 to synapse in the submandibular ganglion - postganglionic fibers innervate the submandibular and sublingual salivary gland

Question 51

facial nerves (CN VIII): facial nerve

Answer 51

-exits through the stylomastoid foramen to provide motor fibers to the muscles of facial expression via some 6 named branches (posterior auricular, cervical, mandibular, buccal, zygomatic, and temporal)

Question 52

vestibulocochlear nerve (CN VII)

Answer 52

- carries sensory information from the inner ear - conveys impulses related to both balance and hearing - this nerve is sometimes referred to as the statoacoustic nerve - impulses related to hearing originate in the snail shaped cochlea and are conveyed by the cochlear branch of this nerve - information relating to balance and equilibrium derives from the semicircular canals, utricle, and saccule and is conveyed by the vestibular branch - the cochlear and vestibular branches join together and enter the endocranial cavity through the internal acoustic meatus, in company with the facial nerve

Question 53

glossopharyngeal nerve (CN IX)

Answer 53

- mixed - somatic motor to stylopharyngeus and from posterior 1/3 of tongue, oropharynx, middle ear (tympanic) - it is mostly sensory, relaying somatic and visceral information as well as that related to taste - also conveys somatic and parasympathetic motor impulses - it has several important branches - it exits the skull through the jugular foramen - within the foramen, the glossopharyngeal gives off a branch, the tympanic nerve - specai lsensory (taste) from posterior 1/3 of tongue - visceral afferents from carotid sinus and body - parasympathetic is lesser petrosal nerve destined for parotid gland synapsing at otic ganglion - two branches tympanic (foramen ovale) and glossopharyngeal (jugular foramen)

Question 54

glossopharyngeal nerve (CN IX): tympanic nerve

Answer 54

- carries parasympathetic fibers - runs to a plexus atop the petrous temporal - emerges from this plexus as the lesser petrosal nerve which exits the skull through the foramen ovale to synapse in the otic ganglion immediately below the foramen - postganglionic fibers then jump onto the auriculotemporal nerve (branch of the mandibular division of the trigeminal, which also transverses the foramen ovale) and travel with it to innervate the parotid gland

Question 55

glossopharyngeal nerve (CN IX): glossopharyngeal

Answer 55

- glossopharyngeal nerve runs into the neck giving the pharyngeal branches to the pharyngeal plexus on the back of the middle constrictor muscles - these branches convey sensory information from the pharynx and are partially responsible for the gag reflex - runs along the stylopharyngeus muscle, supplying it with motor fibers, and then turns forward to reach the back of the tongue - it conveys taste from the posterior one-third of the tongue - sends off a branch that runs down the internal carotid artery to its bifurcation with the external carotid artery - this carotid branch provides visceral sensory information from chemoreceptors in the carotid body (measuring levels of CO2) and stretch receptors in the carotid sinus (monitoring blood pressure)

Question 56

vagus nerve (CN X)

Answer 56

- mixed - it has the most extensive distribution of any cranial nerve, innervating structures in the head, neck, thorax, and abdomen - gives somatic motor fibers to the pharyngeal constrictors and the laryngeal muscles (swallowing and speaking) - provides parasympathetic innervation to cardiac (heart) muscle and to the smooth muscles and gland of the digestive system - conveys sensory information from the skeletal muscles it innervates, the external auditory meatus, and the tracheobronchial tree of the lung - also conveys taste from the epiglottis - exits the skull through the jugular foramen - cell bodies of the sensory neurons are located within ganglia (superior jugular ganglion) in this foramen and ganglia (inferior nodose ganglion) just below it - the auricular branch runs from the superior ganglion to the external ear - vagus runs through the neck between the internal carotid artery and jugular vein in the carotid sheath - sends off 2 principle branches in the neck - pharyngeal nerve supplies the pharyngeal constrictors and most of the palatal muscles, and the superior laryngeal nerve supplies the cricothyroid muscles - below the neck the right vagus nerve sends off the right recurrent laryngeal nerve beneath the subclavian artery - left vagus nerve runs along the aortic arch, sending off the left recurrent laryngeal nerve under the arch - the recurrent laryngeal nerves run back up into the neck to supply all of the intrinsic laryngeal msucles with the exception of the cricothyroid - vagus provides fibers to the cardiac plexus and the pulmonary plexus - branches destined for the heart emerges from the former - branches destined for the lung come from the latter - nerves run down the esophagus as the anterior and posterior vagal trunks into the abdomen - left vagus contributes primarily to the anterior vagal trunk -> supplies the stomach, liver, pancreas, and parts of the intestines - right vagus constitutes the bulk of the posterior vagal trunk -> contributes to the celiac ganglion on the front of the aorta, from which the majority of abdominal structures receive innervation

Question 57

accessory nerve (CN XI)

Answer 57

- conveys motor impulses to skeletal muscles - somatic motor to trapezius and sternocleidomastoid - it is really 2 nerves and is sometimes referred to a the spinal accessory nerve - comprises of 2 nerves that are conjoined for a short distance -> it has 2 roots and 2 branches - two roots of the accessory nerve -> spinal and cranial (medullary) roots - spinal and cranial roots join together to form the accessory nerve which exits the cranium through the jugular foramen in company with the vagus nerve - 2 branches of the accessory nerve -> spinal and cranial (medullary) branches - upon emerging from the jugular foramen, the spinal root fibers of the accessory nerve split off as the spinal branch to innervate sternocleidomastoid and trapezius - the cranial root fibers of the accessory nerve form the cranial branch - the cranial branch is an accessory to the vagus

Question 58

spinal root of accessory nerve (CN XI)

Answer 58

- derives from a column of gray matter in the ventral horn of the spinal cord from C1-C5 - the axons from theses neural cell bodies join together as they travel upward through the vertebral canal, forming a single bundle that passes upward through the foramen magnum

Question 59

cranial root of the accessory nerve (CN XI)

Answer 59

-derives from motor nuclei in the medulla oblongata

Question 60

hypoglossal nerve (CN XII)

Answer 60

- conveys somatic motor impulses to the intrinsic and extrinsic tongue musculature except palatoglossus (vagus) - exits the skull through the hypoglossal canal - supplies the 2 intrinsic tongue muscles and 3 extrinsic tongue muscles: hyoglossus, genioglossus, styloglossus

Question 61

nerve origins

Answer 61

- olfactory nerve- takes origin from telencephalon - optic nerve- takes origin from diencephalon - all the others originate in the brain stem - mesencephalon- oculomotor CN III and trochlear CN IV - pons- trigeminal CN V, abducent CN VI, facial CN VII, vestibulocochlear CN VIII - medulla- glossopharyngeal CN IX, vagus CN X, hypoglossal CN XII

Question 62

CN in the cavernous sinus

Answer 62

- CN III, IV, V1, VI pass through - pass through canvernous sinus on their way to the superior orbital fissure - come from brain stem - 3,4,VI,6 pass through the cavernous sinus - deoxygenated blood being drained from the brain

Question 63

somatic motor of the facial nerve (CN VII)

Answer 63

- somatic motor- muscles of facial expression, posterior belly of digastric, stylohyoid, and stapedius -> exits the skull via internal acoustic meatus and stylomastoid foramen -> forms the parotid plexus - parotid plexus innervates the facial muscles (zygomatic branches, buccal branches, marginal mandibular branch, temporal branches, cervical branch, posterior auricular nerve)

Question 64

terminal sulcus

Answer 64

- anterior 2/3 (taste)- facial nerve from chorda tympani and somatic sensory from lingual nerve (V3) - somatic sensory from V3 posterior 1/3 (taste and somatic sensory from CN X) - terminal sulcus separates them

Question 65

vagus nerve (CN X)

Answer 65

- SOMATIC MOTOR- to all muscles of palate: palatoglossus, levator veli palatini, except tensory veli palatini - all muscles of pharynx: constrictors, salpingopharyngeus, palatopharyngeus, except stylopharyngeus - SOMATIC SENSORY- - from laryngopharynx, larynx, external auditory meatus, and part of tongue and epiglottis - PARASYMPATHETIC: - to pharynx and larynx and all thoracic vsicera and all abdominal viscera down to left colic flexure (ganglia in walls of organs) -> lungs, heart, stomach - nonsensory visceral afferents- from carotid body and sinus, and thoracic and abdominal structures - SPECIAL SENSORY- taste - root of tongue and epiglottis

Question 66

dorsal view of brain

Answer 66

=superior view of brain

Question 67

longitudinal fissure

Answer 67

-separate the left and right sides of the brain

Question 68

ventral view of brain

Answer 68

=inferior view of brain

Question 69

commissure tract

Answer 69

-connects the left and right side of brain

Question 70

projection tract

Answer 70

- long white matter tract | - long distance form of axonal communication

Question 71

association tract

Answer 71

-connect 2 things on the same side of the brain

Question 72

wernickes and broccs

Answer 72

- on left side of the brain - connection between them is the arcuate fasciculus - association tract

Question 73

fornix

Answer 73

connects mammillary to amygdala

Question 74

metencephalon

Answer 74

- pons - tegmentum- continuous space - 4th ventricle - cerebellum

Question 75

trochlear nerve

Answer 75

- only one that comes off the posterior aspect of the brain stem - trigeminal- lateral of pons - abducens- anteriorly between pons and medulla - 7-11- lateral aspect of the medulla - 12- anterior aspect of medulla

Question 76

lateral ventricle

Answer 76

- lateral to the septum pellucidum (separates the left and right side) on both sides - interventricular foramen leads to third ventricle

Question 77

third ventricle

Answer 77

- enters through interventricular foramen | - CSF is draining into the midbrain into the cerebral aqueduct -> into fourth ventricle

Question 78

CSF

Answer 78

- clear colorless fluid present in the ventricles of the brain and in the subarachnoid space throughout the CNS - cushions and protects the brain and spinal cord from trauma - has immune factors (removes toxic substances) -> lymphatic purposes -> removes waste - provide nutrients to the brain as well - provides mechanical buoyancy and support for the CNS -> otherwise it would crush the medulla and toxicity centers -> you will start to vomit - produced in the ventricles, predominantly by the choroid plexus constantly - resorbed into venous circulation through arachnoid granulations in the superior sagittal sinus - can be drawn from the subarachnoid space via a spinal tap (at L3/4 or L4/L5) or a cisternal tap (of the cisterna magna, or cerebellomedullary cistern, accessed between C1 and the foramen magnum)

Question 79

pathway of CSF flow

Answer 79

- lateral ventricles - interventricular foramen - third ventricle - cerebral aqueduct - fourth ventricle - exit through 1 of 3 holes: median aperture (foramen of magendie) or 2 lateral apertures (foramen of luschka) - bathe the brain in blood through subarachnoid space - CSF moves all the way up to the top of brain -> flushed away through the arachnoid granulations - allows CSF to be reabsorbed into the superior sagittal sinus

Question 80

cerebellomedullary cistern (cisterna magna)

Answer 80

-

Question 81

cerebral arteries

Answer 81

- anterior cerebral artery (longitudinal fissure) - middle cerebral artery (lateral sulcus) - posterior cerebral arteries (on inferomedial aspect of temporal and occipital lobes)

Question 82

cerebral cortex

Answer 82

-

Question 83

prefrontal cortex

Answer 83

-in frontal lobe

Question 84

central sulcus

Answer 84

-separates the frontal parietal lobe

Question 85

precentral gyrus

Answer 85

- anterior to central sulcus - primary motor cortex - first stop of processing sensory information - frontal

Question 86

postcentral gyrus

Answer 86

- posterior to central sulcus - primary somatosensory cortex - sensory - parietal

Question 87

primary visual cortex

Answer 87

-posterior part of occipital lobe

Question 88

brocas area

Answer 88

- frontal lobe - triangle shape - secondary motor speech

Question 89

primary auditory cortex

Answer 89

-transverse gyri of heschi

Question 90

limbic system

Answer 90

- control our emotions - cingulate gyrus - parahippocampal gyrus - hippocampal gyrus - dentate gyrus - nuceli: - mammillary body (hypothalamus) - amygdala (temporal lobe)

Question 91

telencephalon: basal ganglia

Answer 91

- caudate nucelus- wall of the lateral ventricle - putamen - globus pallidus - putamen and globus pallidus- forms the lentiform nucleus - internal capsule

Question 92

substantia nigra

Answer 92

- produces the neurotransmitter dopamine - where dopamine cells are produced - black pigment - act on basal nuclei circuits - these are dead in parkinsons - mesencephalon - involved in motor coordination (red nuclei too)