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A&P 1 Brain & Cranial Nerves Guide Lab Exercises Have someone in your group read the following out loud, while the others read along:

In this "Lab Guide", we will be looking at the brain & cranial nerves. This guide should only be attempted after reading the correct sections in either the lab or lecture book, or watching any videos that have been assigned. The First 2 Parts must be done in lab, with the dissections and other lab materials. Parts 3 & 4 can be done outside of lab.

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Part 1. Review Key Concepts from the book and videos #1 Read Me

Have someone in your group read this, while the others follow along: Look over the list of regions and sub regions is below. Make sure you understand this outline, and write down any individual structures you can think of. For example, you could write “corpus callosum” under “inner white matter” and “pituitary” under “hypothalamus”. You might want to come back and complete this after the next section! A. Cerebrum (telencephalon) 1. cerebral cortex (outer gray matter)

2. inner white matter (inner tracts, nuclei, etc.)

B. Diencephalon 1. epithalamus

2. thalamus

3. hypothalamus

C. Brain Stem 1. midbrain

2. pons

3. medulla oblongata

D. Cerebellum

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Part P 2. Find d the Regio ons and Sttructures o of the Brain you need d, on both the models m and d the sheep p brain. #1

Have H someo one in your group g read d this, while the others follow alon ng: Get G a dissectting pan, 1 scalpel, 1 pair scissors, a and some latex-free surg gical gloves. Your Y group should have the t following g in front of yyou: 1. 2. 3. 4.

uman Brain Model Hu Sh heep Brain - Whole, witth Dura Matter (you willl be dissectting this!) Sh heep Brain Whole W - with hout dura m mater (you w will not be d dissecting tthis) Sh heep Brain Frontal F Section

Human n brain model

Sheep bra ain without meninges s

We W will be co omparing the ese four at th he same time e.

Shee ep brain w with mening ges

Sheep brain - Fro ontal sectio on

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Meninges M Obtain O one off the preserv ved sheep brains that is still encased within the protective membranes m known k as the e meninges.. The menin nges consistt of three layyers; an oute er dura mater, a middle arac chnoid, and an internal p pia mater.

Do This!

Do This!

While W lookin ng at the "sh heep brain with w mening ges":

Examine E the dura mate er, a protectivve outer meembrane com mposed of a tough dense e co onnective tis ssue. Descrribe the appe earance and d feel of this membrane.

Continued on nextt page

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Do T This!

#3

Examine E the e surface of the "sheep p brain who le - withoutt dura mater". Note the e thin fillmy membra ane covering g over the ac ctual brain tisssue. This iis more deliccate tissue o of the arachnoid and a pia ma ater. The arrachnoid willl only look likke a film with dark patch hes here and therre...you may y not really see it. The p pia mater will look like a shiny coat directly attach hed to the ne eural tissue.

Study S the ex xternal featu ures of the brain. b On th his guide, we will use im mages from m either the model or sheep brain.. Howe ever, find all of the follo owing on th he surface o of the "shee ep brain witthout dura mater", the dissected “Sheep Bra ain - Whole,, with Dura Mater” and the "hum man brain mo odel". Use the images s in your lab b book as n needed. A fissure is a deep groov ve that goes deep and se eparates big g regions. Examine E the sheep brain n from a supe erior view (ssee figure be elow). Note the two large ce erebral hemispheres tha at constitute the cerebru um and enve elop most of the brain. T The ce erebral hemispheres are e almost com mpletely sep parated by a deep longittudinal fissure. The T cerebrum m and cerebe ellum is separated by th he transvers se fissure.

6 D Do Th his!

If you gently sp pread the hem mispheres apart, you can ssee a band off tissue that cconnects the ttwo he emispheres medially. m This s is the corpus callosum. W We will be cu utting through this when we e dissect the bra ain. The surface off each hemisp phere consists s of up pward folds of o nervous tiss sue called gy yri an nd shallow grrooves called sulci. These e in ncrease the su urface area of the cerebrall co ortex to allow w more comple ex interaction be etween neuro ons. Next N locate the e cerebellum m just caudal to t th he cerebrum. It is separate ed from the ce erebral hemis spheres by the deep trransverse fis ssure. Like th he cerebrum, the cerebellu um has a high hly convoluted d surface (gyrri and su ulci) and lobe es (see image e below). Caudal C and infferior to the ce erebellum notte the medul la oblongata which tapers outt to form the more m slenderr sp pinal cord. Find these stru uctures on the e model and sheep s brain. Keep K in mind that t you have to locate any y motor and se ensory cortice es on your wo ordlist:

7 The dorsal porrtion (or "roof"") of the midb brain can be ex xamined by carefully c sprea ading apart th he transverse fis ssure on the “whole “ sheep p brain withou ut meninges” (s see figure). This T exposes four f rounded bulges called d th he corpora qu uadrigemina a. The two su uperior collicu li arre larger than n the two inferrior colliculi. If I you look on n th he midline bettween and jus st above the superior s co olliculi you will see a small fingerlike exttension of tis ssue called th he pineal bod dy or gland. Examine the brain from an inferior i view (see ( Figure be elow). At the cranial end of o the brain no ote the two olfactory bulb bs that lay ag gainst the und dersurface of th he cerebrum. The band off tissue extend ding caudallyy from these bulbs are the olffactory tracts s. Caudal C to the olfactory o bulb bs and tracts is the X-shape ed optic chia asma. This iss the point wh here th he two optic nerves n from th he eyes meet and partially cross over be efore forming g the optic traccts th hat extend back to the visu ual area of the e cerebrum. Caudal C and infferior to the optic chiasma is a small bea an shaped piituitary gland d. This is a m major en ndocrine glan nd and is attac ched to the brain by a slen nder stalk callled the infund dibulum. Th he pituitary gland may be missing from som me of the prese erved brains, leaving only the infundibu ulum. The infundibulu um is rooted in a bulge of nervous tissu ue called the m mammillary body. This mammillary m bo ody and the ne ervous tissue e superior to itt comprise the e brain region n known as th he hypothalamus s. A portion of o the pituitary y gland is acttually an exten nsion of this h hypothalamuss.

Note: Th he mamillarry body is NOT very deffined or clear on the shee ep brain!!

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The ventral portion (or "floor") of the midbrain consistss of the cereb bral peduncles. These ban nds of ne ervous tissue e connect the cerebrum witth other regio ns of the braiin and are loccated just cau udal to th he hypothalam mus. Caudal C to the midbrain m is th he hindbrain which w consistss of the pons s and the medulla oblong gata. The nervous tissue then tap pers to form th he spinal cord d. Do This!

Dissec cting the Sh heep Brain

s time to dis ssect the “Sheep S Brain n - Whole, w with Dura Mater”, as we e want to see internal Now it is structure es. You will be comparring this witth the brain model, wh hich you sho ould now se eparate the e2 halves, and a any pre e-sectioned d preserved d sheep bra ains you wa ant for varia ability (available in a bucket at a the front of the room m). s sttill has a pa art of the eth hmoid bone e attached on the ante erior frontal Determine if your specimen s present, slip s a blunt probe p betw ween the bone and the dura to carefully lobe. If the bone is e the bone away from the specim men. Then, using yourr scissors, ssnip away a any attache ed separate dura. Ex xamine the e removed ethmoid e bone and iden ntify the cribriform plattes, where the olfactorry bulbs we ere sitting, and the cris sta galli: cre est of bone e where that serves ass the surface of attachment of the meninges. m Also, the e optic nerv ve may still be attache ed to 2 large e fat bodiess – these arre 2 pads th hat sit behin nd your eye eball. Using g the scisso ors, cut the e optic nerve es to removve the padss, trying to g get the brain to look liike the one in the imag ge below. Lay the brain, upsid de down, on the disse ecting tray. Always use u a scalp pel like a bu utter knife; ne ever “saw” through t the e tissue. It will take you y severall t get throu ugh the brain. passes to Each tim me you slide e the scalpe el through the brain, try t to stay in n the s slice. Sta ay as close to previous center of o the pituita ary as possible. WATCH H YOUR FIN NGERS!

Use the following im mages to guide you th hrough the p parts you n need to know w, finding the structures on the brain b model and dissec cted sheep brain, usin g the image es in your ttext or lab b book as you u need. Make M sure you y find eve erything ind dicated on yyour wordlisst indicated d with an Assterisk (*) on the shee ep brain.

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1. Speciffic Parts of th he Cerebrum m Locate the e corpus callosum, the band of tissue that connects the two cereb bral hemisphe eres. Also loc cate the band of tis ssue below th he corpus callosum known as the fornix. Depending D on the exact pos sition of the sectioning cut you sh hould either see s a membra ane linking the e fornix and corpu us callosum or o a cavity betw ween them. The membrane is the choro oid plexus, wh here cerebros spinal fluid is pro oduced and circulated. c Make sure e you see the e corpus callo osum and the lateral ventricles on n the “Sheep p Brain

Frontal Section”. S

2. Speciffic Parts of th he Dienceph halon:

Before we e go on: A wo ord about the “diencephalo on” and its ind dividual “sub-regions”: The dienc cephalon is th he region that surrounds the 3rd ventricle e. So a good way to look a at it is like a thick box:

4. F Find the diencep phalon, and its s sub regions, on n the “Sheep Brai n Frontal Sectio on”.

Dep pending on w where your frontal section w was taken, you u may not see e exactly whatt is shown be elow! These stru uctures, on a ““Sheep Brain n Frontal Sec ction”, will not be on the Pra actical!

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Inferior to the fornix is a round struc cture called the intermedia ate mass. Th his is the med dial portion of the two po ortions of the thalamus tha at lie within each cere ebral hemisph here. If there appears to be e a depress sed area arou und the interm mediate mass of the thalam mus, this will be the third ventricle. v

3. Speciffic Parts of th he Brain Stem, including g the midbrain: Examine again a the mid dbrain structu ures; the dors sal corpora quadrigemin q a and pineal body, and th he ventral ce erebral peduncles. Also reexamine the parts of th he hindbrain; the pons, the e medulla, an nd the cereb bellum.

he Cerebellu um 4. Speciffic Parts of th The white e matter structture in the center is the arb bor vitae.

Note that there is a sle ender canal th hat passes through th he midbrain to o the cavity be etween the cerebellum m and the me edulla. The ca avity is the fo ourth ventricle of o the brain an nd the canal is i the cerebra al aqueductt. The cerebrral aqueduct carries c cerebrosp pinal fluid from m the third ventricle to the fourth ventricle. Bloc ckage of this passage p caus ses the condittion known as s hydrocephalus.

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On the dissected ““Sheep Brain - Whole, with Dura Mater”, note the following structures, and how different they look on the dissected brain, versus the whole brain: Dura mater Pituitary gland (hypophysis) Optic chiasma Mamillary body (human brain model only) Central sulcus Midbrain and corpora quadrigemina Pons Pineal gland There are others, but these really stand out! Also notice how different these structures look on the shhep brain versus the human model, do to the fact that a sheep has a neck that goes straight out, whereas our has a 90 degree bend: Hypothalamus Midbrain

Do This!

Clean Up Procedures

1. Replace the following back into the buckets from which they came: Sheep Brain Whole - without dura mater (you will not be dissecting this) Sheep Brain Frontal Section 2. Place the brain you dissected, and any parts, in the designated container. When you are ready, place your gloves in a regular trash can and NOT in the container with the dissected brains. 3. Take the dissection tray and all instruments to the sink to be washed. 4. Remove the pad from the dissection tray and wash them separately using the provided disinfectant and sponge. 5. Also spray the instruments with disinfectant and clean them using the provided toothbrushes. 6. Rinse the pad, dissecting tray, and all tools and place them in the drying tray. 7. Place the instruments SHARP END DOWN in the appropriate portion of the drying tray. 8. Spray down the area of the lab bench where the dissection was completed with disinfectant and dry using a paper towel.

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Part 3. Identify and study the Cranial Nerves – Can be done out of lab! #1

Read Me

Have someone in your group read this, while the others follow along:

No two instructors are the same when it come to the cranial nerves. Some want you to know the names only, some want names and function, some want you to be able to ID them on images and models. You should confirm with your instructor what you need to know regarding the cranial nerves. Here, we will have you: 1. name all 12 in order, starting with the most anterior. 2. know something about their basic function. 3. ID the first 6, and number 10, on an image. If you need to know more, your instructor can guide you.

Continued on next page

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#2 Fill out this table: Cranial Nerve:

Major Functions: Sensory only:

I Sensory only: II Mainly Motor: III Mainly Motor: IV

Motor & Sensory: V

Mainly Motor: VI Motor & Sensory: VII Mainly Sensory: VIII

Motor & Sensory (only sense listed here): IX

Motor & Sensory: X

Mainly Motor: XI

Mainly Motor: XII

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#3

Label the Cranial Nerves. 1

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La abel the cranial nerves listted below, and number X, on this diagrram. Label th hem on both the rig ght and left sides. If you cannot c directly y label the ne erve, label the e structure tha at accommodates th he nerve (for example, e the optic and olfa actory nervess cannot be diirectly seen o on the image, but th he structures that t attach to them can be e). Vagus Olfactory Trochle ear Oculom motor Abduce ens Optic Trigemiinal

If your instructo or wants you to be able to ID the other 5, label them on the image e now!

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Part 4. Assess yourself using a series of thinking questions – Can be done out of lab!

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Read Me

Have someone in your group read this, while the others follow along:

This will help in both lecture and lab. Answer these questions while identifying the structures on a model or image. You may do this exercise outside of lab if time is short. Answer them out loud, if you want to save time. Use a separate piece of paper if you need more space.

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Beginning with the outside layer, the names of the three meninges that enclose the CNS.

2. Name the three major regions of the Diencephalon.

3. Name the three major regions of the midbrain.

16 4. Name the two major regions of the cerebrum

5. Name the band of tissue at the base of the longitudinal or sagittal fissure that is the primary nerve pathway connecting right and left cerebral hemispheres.

5. Name of the brain region to which the pituitary gland is attached. Part of the pituitary (posterior lobe) is actually formed from tissue of this part of the brain. Also name the stalk that attached the gland.

6. Name of the small cavity around the thalamus which contains CSF.

7. Name of the point where the two optic nerves meet and partially cross over, before passing to the cerebrum.

17 8. Name of the outer layer of each cerebral hemisphere. (HINT: it is composed of grey matter)

9. The region of the brain consisting of two major hemispheres.

10. Name of the deep fissure that separates the cerebellum from the cerebral hemispheres.

11. Name of the grooves and folds of tissue characteristic of each cerebral hemisphere.

Groove -

Fold -

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12. What do we call the large, obvious sulcus running across the cerebral cortex?

13. Finish this sentence: All ___________________ functions of the brain are posterior to the Central Sulcus.

14. Finish this sentence: All ___________________ functions of the brain are anterior to the Central Sulcus.

15. Name the ridges of tissue anterior and posterior to the central sulcus of the cerebrum. What are their functions?

Anterior ridge -

Posterior ridge -

16. Name the gland that is found in the epithalamus. What does it secrete?

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17. Brain region that includes "vital centers" for involuntary control of heart function, respiratory function and vasomotor activity.

18. Brain center that functions as the "master gland" of the endocrine system. (HINT: fill in the blanks below):

"The ______________________ of the brain acts to control homeostasis of the

visceral organs, mainly by controlling the output of the _________________gland,

also known as the ___________________. "

19. Primary visual area of cerebrum are found where?

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20. Brain center that acts as a primary organizational control center for all information entering the cerebrum.

21. Brain center that includes involuntary centers critical to maintenance of muscle tone, equilibrium and posture.

22. What is the white matter of the cerebellum called?

21 23. How do the relative sizes of the cerebral hemispheres compare in the sheep brain and the human brain? What conclusions can you draw from this?

24. How do the relative sizes of the olfactory bulbs compare in the sheep brain and the human brain? What conclusions can you draw from this?

25. What is the importance of the fact that the surface of the cerebral hemispheres is highly convoluted?

22 26. What is the importance of the corpus callosum?

27. What is the function or importance of the ventricles of the brain? How are they related to the central canal of the spinal cord, and the subarachnoid space?