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AP1 Lab 6 - The Human Brain (Week 1)
Project 1 – Cerebrum, Cerebral Cortex, & Cerebellum
Identify the following on the human brain models
CEREBRUM * (subdivided into L & R CEREBRAL HEMISPHERES) figs. 12.5 through 12.8
LONGITUDINAL FISSURE - The deep vertical separation between the 2 hemispheres along the
mid-sagittal plane. It runs anterior to posterior.
TRANSVERSE CEREBRAL FISSURE - The horizontal separation between the cerebellum and cerebrum.
Though not visible on our models there are two DURAL SINUSES, the SUPERIOR SAGITTAL SINUS and the
TRANSVERSE SINUS, found in these fissures. They are ‘channels’ created by separations of the dura matter and
resemble large veins. They do in fact contain venous blood.
CSF is reabsorbed from the subarachnoid space through structures called arachnoid granulations (a.k.a.
arachnoid villi) back into venous blood at these dural sinuses.
Again, these sinuses are not visible on the models. See figs. 12.22 through12.24.
The blood and absorbed CSF eventually flows to the two internal jugular veins in the neck back toward the heart.
LOBES OF THE CEREBRUM:
Each cerebral hemisphere is subdivided into LOBES called: FRONTAL, PARIETAL, OCCIPITAL, and
TEMPORAL. (Note how these correspond to the cranial bones.) Fig. 12.5
Each lobe is then subdivided into many ‘valleys’ called sulci (pronounced “sul – sigh”) and ‘ridges’ called
gyri (pronounced “Ji – rye”). The pia mater follows every convolution of the brain, clinging tightly to it.
CENTRAL SULCUS (pronounced “sul-Kus”) is one of the many SULCI. Is the landmark sulcus (valley)
separating frontal lobe from parietal lobe. It runs along the coronal/frontal plane. (SULCUS = SINK)
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The superficial gray matter covering each cerebral hemisphere is the CEREBRAL CORTEX.
Being gray matter, what do you suppose it is composed of, mostly? ______________________________
Various functions of the brain are known to be localized in specific regions of the cerebral cortex.
Use figs. 12.6 through 12.8 to identify the location of:
PRECENTRAL GYRUS * (one of many GYRI) (Pronounced “Ji-rus” and “Ji-rye.”)
 A landmark gyrus just anterior to the central sulcus.
 It is also called the PRIMARY MOTOR CORTEX.
 Countless neuron cell bodies, dendrites, and axons form billions of synapses in these ridges.
 Most motor impulses for voluntary muscle contraction begin here as conscious thought.
POSTCENTRAL GYRUS * (one of many GYRI)
 A landmark gyrus just posterior to the central sulcus.
 It is also called the PRIMARY SOMATOSENSORY CORTEX.
 Most incoming somatic sensory information arrives here. Somatic sensory info is sensory info coming from skin,
muscles and joints.
These next four areas are ‘approximate’ locations.
WERNICKE’S AREA – (pronounced “VER-ni-keez”) possibly for speech recognition (understanding what words mean
and for sounding out unfamiliar words) In most people the left hemisphere is dominant for speech.
BROCA’S AREA – (pronounced “BRO-kahz”) for motor speech control (being able to pronounce the word you are
thinking) (Note: In most people the left hemisphere is dominant for control of motor speech.)
PRIMARY AUDITORY CORTEX (AREA) - for sound / hearing.
PRIMARY VISUAL CORTEX (AREA) - for visual images.
So, based on what you just learned, where would most sensory info from somatic (skin, muscle, & joints) regions arrive?
_________________________________________________
And, where would the impulses going out to control most voluntary muscle contractions originate?
_________________________________________________
CEREBELLUM *
Take a brain to your instructor and confirm accuracy of your identifications so far.
* Use the attached “Divisions of the CNS and their Functions” to learn the function.
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Project 2 – Brain Stem and Misc Features
Use Fig. 12.11 to ID the following on our models and give function(s) as stated in the “Divisions of the CNS” handout
BRAIN STEM
MIDBRAIN *
PONS *
MEDULLA OBLONGATA *
SPINAL CORD *
DIENCEPHALON [not labeled as “diencephalon” but the two parts are labeled.]
THALAMUS *
HYPOTHALAMUS * [On the models it’s the funnel shaped area just below the thalamus]
Use various figures in chapter 12 to ID the following.
OLFACTORY BULBS and OLFACTORY TRACTS – (Fig. 12.7 & 12.14) On the models… Look on the inferior, anterior
surface of the frontal lobes of the cerebral hemispheres. The white bulbs and tracts are readily visible. The olfactory
bulbs receive messages for the sense of smell from bipolar neurons in your nasal cavity. Axons from these neurons
travel in the olfactory tracts to the appropriate portion of the cerebral cortex.
PITUITARY GLAND – (Fig. 12.11) the bulb-like structure just under the hypothalamus. Because it releases hormones
which control many other endocrine glands the pituitary gland is sometimes called the “MASTER GLAND”. It is
controlled by the hypothalamus. On our models, when you separate the hemispheres, the pituitary gland is wholly
attached to the R hemisphere only.
OPTIC CHIASMA (“ky-AS-ma”) (Fig. 12.11a & 12.11b) and “stumps” of optic nerves. Chiasma means “X” or “crossing.”
The two optic nerves cross above and slightly anterior to the pituitary gland.
CORPUS CALLOSUM * (“cal-LO-sum”) (Fig. 12.9, 12.10 & 12.11) Structurally, this is a broad band of TRACTS forming
the roof of the two lateral ventricles. It looks like a white arch from the lateral view.
Functionally, it is communication pathways between the two hemispheres. It enables the two hemispheres to “talk to
each other.” Many nerve impulses travel back and forth between the two hemispheres along myelinated axons.
What makes it white in color? ________________________
What advantage(s) does this provide? _____________________________________________________________
FORNIX - Structurally, this is essentially a smaller version of the corpus callosum located below it. (On these models it
happens to be colored orange because it is part of the diencephalon.) Viewed from the medial side, above the
thalamus, it appears to be the floor of the lateral ventricles and the roof of the third ventricle. (Ventricles identified
next.)
Functionally, it is communication pathways between various parts of the cerebrum. Like the corpus callosum, it
enables the two hemispheres to “talk to each other.” Many nerve impulses travel back and forth between the two
hemispheres along myelinated axons of the fornix.
**Confirm identifications of above with instructor.
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Project 3 - VENTRICLES
(See Fig. 12.4 & 12.24) and Misc.
Ventricles are cavities within the brain filled with about 140-150 ml. of cerebrospinal fluid. On our models
these cavities are depicted only in the right hemisphere.
LATERAL VENTRICLES (There are two… one in each cerebral hemisphere.) The deep cavity visible
between the corpus callosum and the fornix. The depth of these will be best appreciated when you
dissect the cow brain later.
THIRD VENTRICLE– from the medial view, note the shallow groove beneath the fornix around the
thalamus in the diencephalon. When you put the two hemispheres together it creates a narrow cavity
that is the 3rd ventricle.
CEREBRAL AQUEDUCT – the canal that drains fluid from the 3rd ventricle down to the fourth.
FOURTH VENTRICLE – the fluid filled space just anterior to the cerebellum.
All 4 ventricles contain a specialized capillary bed called CHOROID PLEXUS that produces cerebrospinal fluid
(CSF). Most of the CSF is produced in the two lateral ventricles and flows into the 3rd then through the cerebral
aqueduct to the 4th. The 4th ventricle has three openings: 2 lateral apertures in the side walls and 1 median
aperture in the roof. The apertures connect the 4th ventricle to the subarachnoid space. The majority of CSF
then exits into the subarachnoid space while only a very small percentage flows on into the central canal.
From the subarachnoid space, CSF is absorbed through arachnoid villi (a.k.a. arachnoid granulations) and is
reabsorbed by osmosis into the blood filled dural sinuses.
CENTRAL CANAL (of spinal cord) – The canal in the center of the gray matter of the spinal cord that
carries a small portion of the CSF from the fourth ventral down through the spinal cord.
What are 3 functions/ benefits of CSF?
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Define/Describe hydrocephalus.
Loosely scattered throughout the core of the brainstem is a group of neurons known as the
RETICULAR FORMATION. (Part of the Reticular Formation is the reticular activation system (RAS) Fig.
12.18.
What is its function of the RAS?________________________________________________________
___________________________________________________________________________
Loosely scattered in the deep portions of the cerebrum and diencephalon is a group of neurons known as the
LIMBIC SYSTEM. Fig. 12.17
What is its function? ______________________________________________
On most of our models, the neurons of the limbic system are scattered throughout the orange areas. Parts
of the limbic system at the level of the temporal lobes are the Hippocampus and Amygdaloid Body.
These areas are highly active during learning and the formation of short term memories.
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DIVISIONS OF THE CNS and their Functions
Improves Table 12.1
BRAINSTEM
MIDBRAIN
 mediates visual reflexes and auditory reflexes
 contains the substantia nigra involved in Parkinson’s disease
PONS
 reflex control of respiratory depth. Controls whether you breathe shallow or deep.
MEDULLA OBLONGATA
 reflex control of Heart Rate, Respiratory Rate, and also Blood Pressure by adjusting the diameters
of blood vessels
 also reflex control of swallowing, vomiting, sneezing, coughing
 motor fibers from each hemisphere of the cerebral cortex “cross over” to the opposite side of the
spinal cord. This results in the right hemisphere controlling the left side of the body & vice-versa.
RETICULAR FORMATION (in particular a portion called the RETICULAR ACTIVATING SYSTEM)
 consists of neurons scattered throughout the brainstem. Visual, auditory, and somatic sensory
impulses pass through here on their way to the cerebrum. See Fig. 12.18
 Acts like a ‘filter’ limiting the amount of information reaching the cerebrum thereby controlling
our sleeping-waking cycles and determining our level of mental alertness.
 filters out repetitive stimuli (acts sort of like a “mute” button). Hallucinatory drugs such as LSD
inhibit this and other filters such as the thalamus. Since you are “inhibiting the inhibitor” this
allows the brain to be flooded with sensory input.
DIENCEPHALON
THALAMUS (a.k.a. the “gateway to the cortex”)
 relays incoming impulses to the appropriate part of the cerebral cortex. Acts like a filter
controlling the amount of information reaching the cerebral cortex and memory processing
HYPOTHALAMUS
 responsible for reflex control (not conscious control) of many homeostatic variables such as
temperature, hunger, appetite, thirst, pain.
 also influences moods, emotions, and sex drive
 controls the anterior pituitary gland by way of various ‘releasing’ hormones
 produces posterior pituitary hormones ADH and oxytocin
CEREBRUM (consisting of the two CEREBRAL HEMISPHERES)
CEREBRAL CORTEX
 the outer layer of each hemisphere - consists mostly of unmyelinated cell bodies and dendrites
 responsible for conscious perception of sensory info.
 also conscious thought, reasoning, problem solving, etc.
 also conscious control of motor messages to skeletal muscles for body movement and speech.
BASAL NUCLEI (not visible on our models) (commonly but mistakenly called “basal ganglia”)
 areas deep within each hemisphere (Fig. 12.9)
 helps to control skeletal muscle activity by inhibiting (via IPSPs) unintentional movement
LIMBIC SYSTEM (includes Amygdaloid body (fear, learning and memory), hippocampus (learning and
memory) and cingulate gyrus. (emotions)
 sometimes called the ‘emotional brain’ because it controls emotional responses to bad news, good
news, pain, pleasure, etc. Important in memory processing
CEREBELLUM
“Fine tunes,” through inhibition (IPSPs), impulses from the motor cortex to skeletal muscles allowing us to
produce smooth, coordinated, synchronized contractions like movement, balance, and posture.
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