ANATOMY & PHYSIOLOGY
LAB: Neuroanatomy
Introduction
The human brain—a spongy, three-pound mass of tissue—is the most
complex living structure in the universe. With the capacity to create a
network of connections that far surpasses any social network and
stores more information than a supercomputer, the brain has enabled
humans to achieve breathtaking milestones—walking on the moon,
mapping the human genome, and composing masterpieces of
literature, art, and music.
The brain is the body’s control center, managing just about everything we do. Whether we’re
thinking, dreaming, playing sports, or even sleeping, the brain is involved in some way. A wonder of
evolutionary engineering, the brain is organized into different parts that are wired together in a
specific way. Each part has a specific job (or jobs) to do, making the brain the ultimate multitasker.
Working in tandem with the rest of the nervous system, the brain sends and receives messages,
allowing for ongoing communication.
Neuroscientists are scientists whose specialty is the study of the brain and the nervous system. Over
the years, the field has made enormous progress. For example, neuroscientists now know that each
person has as many as 100 billion nerve cells, called neurons, and the communication between these
cells forms the basis of all brain function. However, scientists continue to strive for a deeper
understanding of how these cells are born, grow, and organize themselves into effective, functional
circuits that usually remain in working order for life.
Sheep brains, although much smaller than human brains, have similar features and can be a valuable
tool when studying neuroanatomy. In this lab, you will explore the structures of the brain that lead
to functions that make us uniquely human.
Materials
 Dissection kit
 Sheep brain
 Nitrile or latex gloves
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Dissection Tray
Microscope
Lab apron
Procedure
1. ALL lab group members should wear lab aprons for this lab. ONLY the “dissectors” (1-2
members of the group) will need nitrile or latex gloves. If you have a latex allergy, please alert
your teacher!
2. Open your dissection kit to ensure you have all the necessary tools. If you are missing any
tools, notify your teacher immediately. You will be held responsible for cleaning, drying, and
returning ALL dissection tools before you will be dismissed from the lab.
a. Your kit should contain: (1) Scalpel, (1) Dissecting probe, (2) Dissecting needles, (1)
plastic ruler, (1) tweezers/forceps, (1) eye dropper.
3. Bring your dissection pan to the center lab bench to obtain a brain specimen from your
teacher. Our specimens have had the dura mater removed already; the dura mater is a
translucent outer membranous covering that serves to protect, surround, and support the
spinal cord.
Part A—External Neuroanatomy
4. Place your brain on the dissection pan
ventral side down, as shown at right.
Locate the cerebrum, the large section of
the brain. This is where higher order
functioning occurs; thinking, perceiving,
planning, and understanding language all
lie within the cerebrum’s control.
5. The cerebrum is divided into two
sections, called hemispheres, by a deep
sulcus known as the longitudinal fissure. The two hemispheres are connected by and
communicate with one another via a bundle of fibers called the corpus callosum. Identify the
right and left hemispheres. NOTE: “Right” and “left” refer to
the SPECIMEN’S right and left.
6. The surface of the cerebrum is called the cerebral cortex (or
“gray matter”, because of its color). The cerebral cortex is
divided into four zones, or lobes, each involved in specific
functions. Identify the four lobes of the cerebral cortex:
a. Frontal lobe: Responsible for initiating and coordinating movements; higher cognitive
skills, such as problem-solving, thinking, planning, and organizing; and for many
aspects of personality and emotional makeup.
b. Parietal lobe: Involved with sensory processes, attention, and language. The right side
of the brain is often associated with spatial awareness processes, while the left with
spoken and/or written language.
c. Occipital lobe: Helps process visual information, including recognition of shapes and
colors.
d. Temporal lobe: Helps process auditory information and integrate information from the
other senses. It is believed to play a role in short-term memory through its
hippocampal formation, and in learned emotional responses through its amygdala.
7. Run your fingers gently over the surface of the cerebral cortex and record your observations.
The ridges of the brain are called gyri (singular: gyrus) and the folds are called sulci (singular:
sulcus). These grooves increase the brain’s surface area, allowing for the inclusion of many
more neurons. Record the average depth (in mm) of the sulci.
8. Identify the smaller division of the brain, the
cerebellum. The cerebellum helps control
movement and cognitive processes that require
precise timing, and also play an important role
in Pavlovian learning. This will be separated
from the cerebrum by a very deep sulcus called
the transverse fissure. Record observations of
the similarities/differences between the
texture, color, and appearance of the cerebrum and cerebellum.
9. Just posterior to the cerebellum is the spinal cord. Together the brain and spinal cord
comprise the Central Nervous System (CNS), which is one of two great divisions in the
nervous system. The brain is protected by the skull, while the spinal cord (about 17 inches
long in humans) is protected
by the spinal column.
10. Turn your brain over, so it is
dorsal side down in the
dissection pan. Just ventral to
the cerebellum are the other
parts of the hindbrain: the
medulla oblongata and the
pons, which control
respiration, heart rhythms,
and blood glucose levels. The
pons is just cranial to the
medulla oblongata, which is
just cranial to the spinal cord.
11. If still intact, the oculomotor nerves will be just cranial to the pons (sometimes, these nerves
are removed with the dura mater). The oculomotor nerves control movement of the eyes,
including constriction of the pupil and keeping the eyelids open.
12. You will notice a white “X” shape just cranial to the oculomotor nerves; this is the optic
chiasm. The two white bundles are the optic nerves, which transmit information from the
retina of the eyes to the brain. The optic nerve of the right eye crosses over and delivers
information to the left side of the brain, and left optic nerve to right side of brain. Each optic
nerve contains between 770,000 and 1.7 million nerve fibers!
a. Damage anterior to the optic chiasm causes loss of vision in the visual field of the same
side only.
b. Damage in the optic chiasm causes loss of vision laterally in both visual fields
c. Damage posterior to the optic chiasm causes loss of vision in one eye but affecting
both visual fields: the visual field affected is located on the opposite side of the lesion.
13. Locate the olfactory bulbs. These are located anteriorly to the optic chiasm. These structures
transmit information regarding smells from the nose to the brain.
Part B—Internal Neuroanatomy, Midsagittal Section
14. Very carefully use the large kitchen knife to cut the brain into right and left portions, along the
longitudinal fissure through the corpus callosum and brainstem in one smooth motion (sawing
back and forth will destroy the brain tissue). The diagram below depicts what you will see in
the midsagittal view.
15. Now that you are looking at the inside of the midline of the brain try to locate a bundle of
white fibers that connects the two hemispheres. This bundle of fibers is known as the corpus
callosum, and it transfers information between the cerebral hemispheres.
16. Just below the corpus callosum you will notice a “space”; this is the lateral ventricle. There
are four ventricles (right and left lateral ventricles, third ventricle, and fourth ventricle). Below
the lateral ventricle is the third ventricle. The fourth ventricle is located in the cerebellum.
The ventricular system contains the cerebrospinal fluid of the brain. The CSF provides
protection for the brain and spinal cord, and creates a stable environment for the brain.
17. Identify the thalamus on your brain; it will be just posterior to the third ventricle and is a large
circular structure. This part of the brain receives and processes sound information and
transmits it to other parts of the brain.
18. Immediately posterior to the thalamus and just anterior to the brain stem is a small structure
called the hypothalamus. Its primary function is to link the nervous system to the endocrine
system via the pituitary gland. As it controls production of hormones, the hypothalamus is
important in regulating body temperature, thirst, hunger, sleep, and sex drive.
19. Identify the inside of the cerebellum. Notice the tree-branching pattern of white and grey
matter. White matter consists of axons covered in insulating myelin; grey matter contains
mostly cell bodies and axons that are not covered in myelin.
20. Identify the brainstem, located ventral to the cerebellum. The forepart of the hindbrain is the
pons, which serves as a bridge between various parts of the nervous system, including the
cerebrum and cerebellum. It is responsible for facial expressions, controlling biting, chewing,
and swallowing mechanisms, allowing the eyes to look from side to side, breathing, and
control of sleep cycles. The lower half of the brainstem is the medulla oblongata, which is
responsible for autonomic (involuntary) functions such as breathing, heart rate, and blood
pressure.
Part C— Internal Neuroanatomy, Coronal Sections
21. You will be cutting the left hemisphere into 4 coronal sections, as shown in the diagram
below. Be sure to make careful observations of each of the structures visible after each
coronal section cut.
22. Cut the first coronal section (#1). Record observations. Note the contrast of grey matter and
the white matter core. Note the space between the corpus callosum and the lateral ventricle.
23. Perform the second coronal section (#2). Record observations.
24. Perform the third coronal section (#3). Record observations.
25. Perform the fourth coronal section (#4). Record observations.
Part D— Microscopic Neuroanatomy, if time permits!
26. Using a razor blade, very carefully cut a thin section of cerebellum and prepare a wet mount
slide (consult with your teacher if you are unsure how to make a wet mount slide) and observe
under the microscope at 100X. Record your observations.
27. Repeat with a thin section of the cerebrum. Record your observations. Compare and contrast
the two tissue samples.
Clean-Up
28. Dispose of your brain sample as shown by your teacher. NO solids should be left in the sink!
29. Thoroughly wash and dry your dissection tools, and replace in their kits.
30. Wash down your lab bench using all-purpose spray. Wash your hands with warm water and
soap.
31. You must get teacher approval BEFORE leaving the lab.
Data
Construct a data table to record your observations during the lab.
Analysis Questions
1. Label the parts of the brain (internal and external) below, on the diagram.
2. What is the purpose of the sulci and gyri of the brain?
3. In what ways do human and sheep brains differ?
4. Is there an advantage to having different discrete functional locations in the brain? Explain.
5. What is the benefit for having the two hemispheres separate and only connected by the
corpus callosum?