SHEEP BRAIN DISSECTION

parts, parts, parts

cerebral cortex

Sheep brains have parts comparable to human brains. Notice the two hemispheres. Identify the lobes of the cerebral cortex: frontal, temporal, parietal, occipital. What are their functions? Notice the sulci (singular - sulcus) and gyri (singular - gyrus). These increase the surface area of the cortex.

Frontal lobe

Temporal Lobe

Parietal Lobe

Occipital Lobe

Sulcus

Gyrus

Cerebellum

Dorsal view

Just take a look!

                                                                                                                                                                                                           

                                    

Cerebral cortex

Cerebellum

Corpus Callosum

Thalamus

Hypothalamus

Midbrain

Pons

Medulla oblongata

Ventricular System

Pineal Body

Why does the spinal cord of the sheep project horizontallyinstead of vertically as in a human?

1) cerebellum, 2) occipital lobe, 3) cerebral cortex, 4) corpus callosum, 5) pineal gland, 6) thalamus, 7) hypothalamus, 8) optic nerve, 9) pons, 10) spinal cord

                                                                                                                                                                                                                                                                 

                                 

Name the parts with pins

                                                                                                                                                                                                                                             

                                       

red pin = corpus callosumblue pin = thalamus

green pin = cerebellum

sheep - ventral view

ventral view ~optic nerve

ventral view~olfactory bulb and tract

ventral view~brain stem

Cranial nerves Olfactory bulb nerve

I. Optic nerve II. Oculomotor nerve

III.

Trochlear nerve IV. Trigeminal nerve V

Abducens nerve VI.

Oculomotor nerve

The oculomotor nerve, cranial nerve III, is found on the the medial surface of each cerebral peduncle. This nerve supplies four muscles of the eye. Movement of the eyes up (elevation), down (depression), up and toward the temple, and inward toward the nose (adduction). Controls constriction of the pupil and accommodation of the lens.

Trigeminal nerve

The trigeminal , cranial nerve V, is a mixed nerve that carries both sensory and motor information.  The motor component controls the muscles of mastication ( chewing), and the sensory component carries sensory information from the face and jaw.  Tooth pain for example, is carried by the trigeminal nerve.

Trochlear nerve

The trochlear,  cranial nerve IV, serves the superior oblique muscle of the eye. The superior oblique allows you to move your eyes down and in toward the nose (intorsion).  This nerve is often obscured by the trigeminal nerve.

Abducens

The abducens,  cranial nerve VI, serves the external rectus muscle of the eye. The external rectus allows you to move your eyes outward toward the temple (abduction). This nerve can be located at the anterior limit of the medulla (that section of the brain located caudal to the pons and anterior to the spinal cord).

ventral view~name the nerves

Cerebral cortex, Gray, White, Thalamus

Cerebral Cortex

The cerebral cortex is a highly ordered gray matter structure composed of six distinct layers. In spite of its complexity, it is composed of only three cell types: pyramidal cells, stellate cells and fusiform cells.

White Matter

White matter is composed of fiber tracts. The "white" is due to myelin sheaths around the fibers which appear white.

Gray Matter

Thalamus

Do you know . . . • Which cranial nerve is the largest?  • Which cranial nerve is the only one that exits the

"posterior" side of the brainstem?  • How many cranial nerves are responsible for eye

movements?  • What does "abducens" refer to?  • Which cranial nerves carry gustatory (taste)

information?  • Which cranial nerve is the longest?  • What two cranial nerves carry sensory information

about blood pressure to the brain?  • Which cranial nerve is responsible for pupillary

constriction?  

• Which cranial nerve is the largest? • CN V (Trigeminal)

• Which cranial nerve is the only one that exits the "posterior" side of the brainstem? • CN IV (Trochlear)

• How many cranial nerves are responsible for eye movements? • Three: CN III (Oculomotor), IV (Trochlear), and VI

(Abducens). • What does "abducens" refer to?

• The abducens nerve carries motor impulses to the lateral rectus eye muscle which moves the eye laterally causing abduction of the eye.

• Which cranial nerves carry gustatory (taste) information? • CN VII (Facial), CN IX (Glossopharyngeal) and CN X (Vagus).

• Which cranial nerve is the longest? • CN X (Vagus) which reaches from the medulla to the

digestive and urinary organs. • What two cranial nerves carry sensory information about blood

pressure to the brain? • CN IX (Glossopharyngeal) and CN X (Vagus).

• Which cranial nerve is responsible for pupillary constriction? • CN III (Oculomotor).

References

• trc.ucdavis.edu/.../Nervous/ grosscns/brain2/brain4.html