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HUMAN ANATOMY/PHYSIOLOGY
“The Human Brain Versus Sheep Brain: A Comparison” Lab
LAB REPORTS DUE: ______________________________________
INSTRUCTIONS: Read the “Pre-lab Information” and study the labeled sheep
brain diagram prior to the dissection. NOTE: The information you will need to label
the diagrams and answer the questions will be in the “Pre-lab Information”, as well
as in the “Procedure” section.
PRE-LAB INFORMATION (READ PRIOR TO LAB)
Sheep brains, although much smaller than human brains, have similar features and can be
a valuable tool for anatomy studies. Here is a list of structures found in both the human
and sheep brains:
•
Cerebrum (including the cerebral cortex/gray matter and cerebral medulla/white
matter)
•
Corpus collosum
•
Cerebellum
•
Brainstem (including medulla oblongata, pons, and midbrain)
•
Diencephalon (including thalamus and hypothalamus)
One major difference between the human and sheep brain is the position on the brainstem
(and therefore, the position of the spinal cord) in relation to the brain. Because sheep are
quadrupedal, the brainstem and spinal cord run parallel to the ground, whereas humans
are bipedal, and our brainstems and spinal cords run perpendicular to the ground (when
standing). This will also affect the position of the foramen magnum in the skull – can you
explain why?
While performing the sheep brain dissection, your goal is to observe the similarities and
differences between the sheep and human brains. The information above lists the
major similarities and differences between the two species. However, you should
observe more differences and similarities during the lab; be sure to note these as you
go along.
Study the 3 labeled sheep brain diagrams (Figures A, B, C) before the dissection.
You will use these diagrams to guide you through the dissection. You will also use
them to help you label the diagrams (Figures I, II, III) in the Results section. See the
next 3 pages for Figures A, B, and C.
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(Put Labelled Sheep Diagrams Here)
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“The Human Brain Versus Sheep Brain: A Comparison”
LAB REPORT STRUCTURE
(1) PROBLEM: In what ways are the human and sheep brains similar? In what ways do the
human and sheep brains differ?
(2) HYPOTHESIS: [Answer the questions posed in the “Problem”. You should use the “Pre-lab
Information” to formulate your hypothesis.]
(3) MATERIALS:
o
Preserved sheep brain
o
Dissecting kit
o
Dissecting pan
o
Gloves
o
Dissecting pins
o
Writing utensil
o
Paper/notebook
o
“The Human Brain Versus Sheep Brain: A Comparison” Lab Packet
o
[Add anything to this list that I may have left out]
(4) PROCEDURE: [ONLY COPY THE REGULAR FONT INTO YOUR
PROCEDURE IN YOUR LAB REPORTS, NOT THE ITALICIZED FONT]
Observation: External Anatomy
1. Collect all materials needed for the lab, including a preserved sheep brain. Set the brain
down so the flatter side (with the white spinal cord at one end) rests on the dissection pan.
2. Notice that the cerebrum has two halves,
or hemispheres. Find the cerebrum and the
cerebellum and observe the differences
between them. Identify the ridges (called
gyri) and the grooves (called sulci) in the
cerebrum. How does the surface of the
cerebrum feel compared to the cerebellum?
3. Turn the brain over. Identify the medulla,
pons, midbrain, optic chiasm, and olfactory bulbs.
Figure A
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4. Find the olfactory bulb on each hemisphere. These will be slightly smoother and a
different shade than the tissue around them. The olfactory bulbs control the sense of
smell. The nerves to the nose are no longer connected, but you can see “nubbly” ends
where they were. The nerves to your mouth and lower body are attached to the medulla;
the nerves to your eyes are connected to the optic chiasm. Using a magnifying glass, see
if you can find some of the nerve stubs. (SEE FIGURE B)
Dissection: Internal Anatomy
5. Place the brain with the curved top side of the cerebrum facing up. Use a scalpel to
slice through the brain along the center line, starting at the cerebrum and going down
through the cerebellum, spinal cord, medulla, and pons. Separate the two halves of the
brain and lay them with the inside facing up.
6. Use Figure C to identify the corpus callosum, medulla oblongata, pons, midbrain, and
pituitary gland. Use your fingers or a teasing needle to gently probe the parts and see how
they are connected to each other. What does that opening inside the corpus callosum lead
to? How many different kinds of tissue can you
see and feel?
•
The corpus callosum is a bundle of
white fibers that connects the two
hemispheres of the brain, providing
coordination between the two.
•
The medulla oblongata is located
right under the cerebellum. In this the
nerves cross over so the left
Figure C
hemisphere controls the right side of
the body and vice versa. This area of the brain controls the vital functions like
heartbeat and respiration (breathing).
•
The pons is next to the medulla. It serves as a bridge between the medulla and the
upper brainstem, and it relays messages between the cerebrum and the cerebellum
(important in controlling movement).
•
The pituitary gland, which produces important hormones, is a sac-like area
between the pons and the optic chiasm. This might be harder to locate, especially
if it has been punctured.
7. Look closely at the inside of the cerebellum. You should see a branching "tree" of
lighter tissue surrounded by darker tissue. The branches are white matter, which is made
up of nerve axons. The darker tissue is gray matter, which is a collection of nerve cell
bodies. You can see gray and white matter in the cerebrum, too, if you cut into a portion
of it.
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8. Use the letter labels on Figure C to try to find the following:
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Ventricles (contain cerebrospinal fluid)
•
The occipital lobe (receives and interprets visual sensory messages)
•
The temporal lobe (involved in hearing and smell). You can find this by looking
on the outside of one of the hemispheres. You will see a horizontal groove called
the lateral fissure. The temporal lobe is the section of the cerebrum below this
line.
•
The frontal lobe (plays a part in smell, plus dealing with motor function)
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The parietal lobe (handles all the sensory info except for vision, hearing, and
smell, like sensation of pressure, pain, and body position).
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The thalamus (a "relay station" for sensory information; it receives messages
from the nerve axons and then transmits them to the appropriate parts of the
brain).
•
The pineal gland (produces important hormones).
9. When you have identified all the structures and have finished with the dissection,
throw your sheep’s brain into the red bucket at the front of the room. Then take your
dissecting pan and all dissecting tools, and wash them in the bathroom. MAKE SURE TO
DRY EVERYTHING THOROUGHLY. Throw out your gloves and wash your hands
thoroughly. Return all materials to the appropriate areas.
(5) RESULTS:
(a) Provide the main function for the brain structures in the data table below. MAKE YOUR
OWN COPY OF THIS TABLE FOR YOUR LAB REPORTS.
TABLE I – BRAIN STRUCTURES AND THEIR PURPOSES/FUNCTIONS
BRAIN STRUCTURE
FUNCTION OR PURPOSE OF BRAIN STRUCTURE
Gyri
Olfactory bulbs
Corpus collosum
Medulla oblongata
Pons
Midbrain
Pituitary gland
Ventricles
Occipital lobe (of cerebrum)
Temporal lobe (of cerebrum)
Frontal lobe (of cerebrum)
Parietal lobe (of cerebrum)
Thalamus
(b) Label Figures I, II, and III and include them in the Results section.
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(6) DISCUSSION:
Answer the following questions in this section:
(a) Name at least 2 major similarities between the sheep and human brains that you did not
name in your hypothesis, but that you observed or learned about during the dissection.
(b) Both the sheep brain and the human brain have the four pairs of cerebral lobes: occipital,
temporal, frontal, and parietal. Although their basic functions are the same, can you think of
how they may differ in function? Hint: Think about the speech centers in the human brain;
think about how humans and animals may process light and sound differently. YOU
SHOULD TRY TO FIND SOME INFORMATION ON THE INTERNET HERE.
(c) Explain why the sheep brain is an effective way to learn more about the human brain (i.e.
what does it help an anatomy student learn and get a better understanding of?).
(7) CONCLUSION: [Summarize the major similarities and differences between the human and
sheep brains. State whether your observations supported your hypothesis, and explain similarities
or differences that were left out of your hypothesis. Lastly, name some things you learned during
the lab.]
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HUMAN ANATOMY/PHYSIOLOGY
“Sheep Heart Dissection” Lab Report
GRADING FORM (50 POINTS)
TOPICS
CRITERIA
POINTS
(5=Excellent; 4=Good;
3=Fair; 2=Difficulties;
1=Poor; 0=Incomplete)
Section 1: PROBLEM
Was the correct problem stated?
Was it clear to the reader exactly what the problem was?
Section 2: HYPOTHESIS
Did the hypothesis directly address the problem?
Did the hypothesis provide the path of blood through the
heart, starting with the right atrium, and where the blood
is coming from?
Did the writer state whether they thought the path was the
same for both humans and sheep, AND WHY?
Section 3: MATERIALS
Were all the materials used in the experiment listed?
Did the writer include any materials that were not on the
original list (ex: magnifying glass)?
Section 4: PROCEDURE
Were all the steps taken in the experiment listed (regular
font required)?
Were any steps left out?
Was there enough detail in the procedure?
Section 5: RESULTS
Was a drawing of the heart provided here, showing the
path of blood through the heart? Were red and blue
arrows used in this drawing? Was the representation
correct in every aspect?
Were Figures A, B, and C included here? Were they
labeled properly?
Section 6: DISCUSSION
Were the 4 questions answered here?
Were the questions answered using complete sentences?
Was enough detail and description provided in the
answers?
Section 7: CONCLUSION
Did the writer summarize the path of blood through the
heart here?
Did the writer address their hypothesis (was it supported
by their observations, and why/why not)?
Did the writer express whether they thought the sheep
heart was a good model of the human heart?
Did the writer list at least 2 things they learned in the
experiment?
WERE ALL 7 SECTIONS OF Were any sections missing?
THE LAB REPORT
Were the sections presented in order?
INCLUDED? (Organization)
Was there information presented in a section that should
have been presented in a different section?
Spelling, Grammar, and Clarity Were multiple spelling and grammatical errors made?
Should the writer use a dictionary in the future?
Does the writer need to proofread his/her work?
Did the writer provide enough description for the reader
in each step?
Was the process easy to follow?
Overall Effect and Impression Was it apparent that the writer put effort into their work?
on the Reader
Was the report’s presentation aesthetically pleasing?
OVERALL GRADE
(50 POINTS MAXIMUM)
SCORE =