Sheep Brain Dissection Guide

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Sheep Brain DissectionGuide
Good Luck!!
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Meninges of the Brain
Brain is protected by the skull and 3 layers of
membranes called meninges

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Observe Meninges

• Examine the brain to see if there is a tough
  outer coatThis is the DURA MATER (literally
  means tough mother)
• Now look for the stringy, web-like ARACHNOID
  MATER (literally means spider mother) beneath and
  stuck to the dura mater. The space under the
  arachnoid, the subarachnoid space, is filled with
  cerebrospinal fluid and contains blood vessels.
• Look deeper and see an thin transparent membrane
  that follows the contour of the ridges (gyri) and
  valleys (sulci) of the brain. This is the PIA
  MATER ( means tender mother)

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Questions??

• What is the function of the meninges?
• Describe the following meninges
• Dura mater, Arachnoid mater, and Pia mater
• What is meningitis?

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Main Brain Regions

• Identify the cerebrum, brain stem) and cerebellum
  on your brain
• Draw picture of sheep brain and label structures

Cerebrum
Cerebellum
Brain stem
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Questions??

• Which part of the brain allows for
• 1) Balance
• 2) Breathing
• 3) Hearing and Vision

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Human vs Sheep

• Compare the various areas of the sheep brain
  (cerebrum, brain stem, cerebellum) to the human
  brain.
• 4. How is it the same and How is it different?

Human brain
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Identify Dorsal Structures

• With the dorsal side up, identify the cerebral
  hemispheres, gyri, sulci,and longitudinal fissure
  on your sheep brain

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Questions??

• What does the longitudinal fissure divide?
• What is the difference between gyri and sulci?
• What is the purpose of the gyri and sulci?

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Lobes of the Cerebrum

• Find the 4 lobes of the brain-frontal, parietal,
  occipital,
• and temporal
• Using pins label each lobe
• Teacher check

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Questions????

• Name the lobe that functions in
• a) Hearing
• b) Vision
• c) Touch
• d) Movement

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Corpus Callosum

• At the longitudinal fissure, gently separate the
  two hemispheres and look down between them for
  the thick band of white fibers. This is the
  corpus callosum
• What is its function?

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Identify Ventral Structures

• Place the sheep brain ventral side up.
• Identify the olfactory bulb, optic nerve, optic
  chiasm
• Using pins label each structure.
• Draw and label the structures in lab writeup

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Questions??

• How does the human brains olfactory bulb differ
  from the sheeps?
• Which is able to smell more odors?
• Look at the optic chiasma. What happens to the
  optic nerve (vision) at the optic chiasma?
• Which side of the occipital lobe (right or left)
  sees for the right eye?

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Brain Stem

• Look at the three parts of the brain stem-the
  midbrain (cerebral peduncle and mammilary body),
  pons and medulla oblongata
• Pin and label parts
• Teacher check

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Function

• Mammillary bodies serve as relay stations for
  reflexes related to sense of SMELL
• Cerebral Peduncle-group of myelinated nerves

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Questions??

• Label your diagram with parts of midbrain and
  brain stem
• What is the function of the medulla oblongata and
  pons?
• Could you survive without them?
• Why or Why not?

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Identify dorsal structures

• Carefully pull the cerebellum away from the
  cerebrum. Dont break any structures off.
• Identify the pineal body, superior colliculi, and
  inferior colliculi.

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Functions-Reflex Centers

• Inferior Colliculi- movement of head and trunk in
  response to sound stimuli
• Superior Colliculi-movement of eyes, head and
  neck in response to visual stimuli

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Pineal Gland

• Produces the hormone melatonin at night
• Melatonin is the sleep hormone

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Questions??

• What is the function of the Pineal body?

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Midsagittal Section

• Obtain a brain the has been cut in half
• Locate the brain stem parts the medulla
  oblongata, the pons, cerebrum, and cerebellum

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Cerebellum

• Look at the cross section of the cerebellum. The
  inner structure is called the arbor vitae (living
  tree).

Why is this a good name for it?
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Midsagittal Section

• Locate the corpus callosum, thalamus,lateral
  ventricle, fourth ventricle and cerebral aqueduct

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Questions

• What is the function of the ventricles?
• The cerebral aquaduct allows for the circulation
  of the cerebral spinal fluid through the
  ventricles. What do you think would happen if
  the duct became blocked?
• How would that affect brain tissue?

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How does the normal brain compare with the
Alzheimers brain? How would that explain the
memory loss?
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The End!!

• Good bye or in sheep language

BAA BAA