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Lab II: Sheep Brain Dissection

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Julia Draper

on 8 October 2013

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Transcript of Lab II: Sheep Brain Dissection

Ventral View
Dorsal View
Right Lateral
Left Lateral
Hippocampus & Dentate Gyrus
Superior Colliculus
Hippocampal Formation
Optic Nerve & Chiasm
Abducens Nerve
Trigeminal Nerve
Ventral View
Mammiliary Body
Temporal Lobe
Spinal Cord
The spinal cord has an entirely different organization from the brain. It still has grey and white matter according to myelination, but the grey matter is organized into a mass in the middle with horns and the white matter surrounds it in columns (Fig 42). In the middle is the central canal which contains CSF (cerebrospinal fluid) and runs the length of the spinal cord. In the spinal cord, the dorsal horns point toward the backside and the ventral horns point to the front (Fig 43). The brain, on the other hand, is oriented with the anterior side pointing toward the front and posterior side pointing to the backside with structures being additionally inferior or superior to each other (Fig 43). In the spinal cord, the dorsal horns contain the multipolar motoneurons.The sensory neurons that are concentrated in the root ganglia are unipolar. There are two spinal nerve roots, dorsal and ventral, that serve as spinal nerves. The dorsal root ganglion has afferent nerves that carry information from the sensory organs to the integration center. Opposite that is the ventral root that uses efferent motor nerves to carry out signals to the motor areas (Fig 44). There are 31 pairs of spinal nerves, in descending order: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccyx (Fig 45). If one were to injure this area, there would be much greater deficit after cervical spine damage than lumbar spine damage because the spinal cord is present in the spine until the lumbar spine. The dorsal root ganglion is the site where afferent (sensory) neurons are concentrated. A ventral root ganglion is not necessary because the efferent (motor) neurons are located within the spinal cord (Fig 46).

Dorsal Root Ganglion
Primary Motor & Somatosensory Cortices
Corpora Quadragemina
Frontal Lobe
Occipital Lobe
Surface Features
Surface of the Brain
Temporal Lobe
Parietal Lobe
Lab II: Sheep Brain Dissection
Atlas B

BIOL 340: Psycho-Biology
Julia Draper & Briana Halliwell

Midsagittal View
Midsagittal View
Spinal Nerves
Cross Sections
Pituitary Gland
Motor (A)
Somatosensory (C)
Olfactory Bulb
Spinal Cord, Medulla and Pons
Spinal Cord
Cingulate Gyrus
Corpus Collosum
Cerebral Cortex
Temporal Lobe
Frontal Lobe
Parietal Lobe
Occipital Lobe
Video displaying Lateral, 3rd, and 4th Ventricles
Tegmentum (floor)
Tectum (roof)
Pineal Gland
Anterior & Posterior Commissures
Hippocampal Formation
Massa Intermedia
Breedlove, S. Marc., and Neil V. Watson. Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience. 7th ed. Sunderland, MA: Sinauer Associates, 2013. Print.
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McCaffrey, Patrick. "Cerebral Lobes, Cerebral Cortex, and Brodmann's Areas." CMSD 620 Neuroanatomy of Speech, Swallowing and Language. Neuroscience on the Web, 2009. Web. 05 Oct. 2013.
Crisan, Elena, MD. "Ventricles of the Brain ." EMedicine. Medscape, 4 Sept. 2013. Web. 05 Oct. 2013.
Kark, Peter, MD. GETTING TEAMS TO SUCCEED: A NEUROLOGIST’S VIEWPOINT: 1) Survival versus Gratification. Digital image. Www.pkark.com. N.p., n.d. Web. 6 Oct. 2013.
Breedlove, S. Marc., and Neil V. Watson. Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience. 7th ed. Sunderland, MA: Sinauer Associates, 2013. Print.
"Hippocampus - What Is the Hippocampus?" Hippocampus. N.p., n.d. Web. 07 Oct. 2013. <http://www.news-medical.net/health/Hippocampus-What-is-the-Hippocampus.aspxhttp://thebrainobservatory.ucsd.edu/hm>.
"Interesting Brain Areas." Interesting Brain Areas. N.p., 30 Apr. 2010. Web. 02 Oct. 2013. <http://mva.me/educational/brain_areas.html>.
N.d. Photograph. Anatomy. StudyBlue. Web. 7 Oct. 2013. <http://www.studyblue.com/notes/note/n/anatomy-/deck/696994>.
N.d. Photograph. Corpus Callosum and Corona Radiata. Web. 7 Oct. 2013. <http://myhomepage.ferris.edu/~griffida/anatomy%20online/a_atlas/cns/white/comm5.htm>.
N.d. Photograph. Histological Features of the Spinal Cord. Web. 7 Oct. 2013. <http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/CNS_Histology/Spinal_Cord/Spinal_Cord_Histology.htm>.
N.d. Photograph. Interesting Brain Areas. PAC Lab, 30 Apr. 2010. Web. 7 Oct. 2013. <http://mva.me/educational/brain_areas.html>.
N.d. Photograph. Nervous System Anatomy. Web. 7 Oct. 2013. <http://craniumcommander.wikispaces.com/Nervous+System+Anatomy>.
N.d. Photograph. Our Sense of Sight. Web. 7 Oct. 2013. <http://faculty.washington.edu/chudler/eyecol.html>.
N.d. Photograph. Sheep Brain. Web. 7 Oct. 2013. <http://classroom.sdmesa.edu/anatomy/ModelPages/sheep_brain.htm>.
N.d. Photograph. Striatum and Globus Palladius. Web. 7 Oct. 2013. <http://homepages.inf.ed.ac.uk/anaru/research/anatomy/>.
"Pineal Gland (anatomy)." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 07 Oct. 2013. <http://www.britannica.com/EBchecked/topic/460967/pineal-gland>.
"Sheep Brain." Sheep Brain. N.p., n.d. Web. 02 Oct. 2013. <http://classroom.sdmesa.edu/bbrothers/modelpages/sheep_brain.htm>.
The meninges consists of three layers: the innermost layer is the dorsally-located Dura Mater, which separates the cranial cavity into compartments and protects the brain from displacement; the middle layer is the Arachnoid Mater, which transfers cerebrospinal fluid from the ventricles; and the outmost layer is the ventrally-located Pia Mater, which is responsible for producing cerebrospinal fluid (CSF). The Dura and Arachnoid Mater layers are the toughest of the three and the Pia Mater is the most delicate layer and is most closely associated with the brain’s surface structures. The brain consists of (from caudal to rostral) the hindbrain, midbrain, and forebrain (Dartmouth.edu). The anterior and posterior aspects of the brain are the medulla and the cerebellum, respectively.
The brain consists of four major lobes, each of which is associated with a primary cortical area: the frontal lobe and primary motor cortex (fig. 6); the parietal lobe and the primary somatosensory cortex (fig. 7); the occipital lobe and the primary visual cortex (fig. 8); and the temporal lobe and the primary auditory cortex (fig. 9). These lobes are divided into sections by three different structures: gyrii, sulci, and fissures. A gyrus refers to folds in the brain, especially as found in the cerebral cortex and a sulcus is a deep groove or furrow in the brain, whereas a fissure is more of a thin crack that separates lobes of the brain. The gyrus that contains the primary motor cortex is the precentral gyrus and the gyrus that contains the primary somatosensory cortex is the postcentral gyrus (fig. 10). These gyrii are the division lines between the frontal lobe and the parietal lobe of the cerebral cortex. Located posteriorly between the cerebellum and the cerebral cortex is the corpora quadragemina, which is made up of the superior and inferior colliculi (fig. 11 & 12)). These structures are collectively known as the tectum, or “roof”, and are immediately dorsal to the ventrally located pons. These colliculi contain sensory nuclei which are relay stations concerned with the processing of visual (superior) and auditory (inferior) sensations.
Ventral View
Within a ventral view of the brain one is able to locate the 12 major cranial nerves, which generally operate sensory systems related to scent, sight, sound, taste, and touch and process motor information that enters the brain. In order the cranial nerves are:
I) Olfactory (fig. 18) VII) Facial
II) Optic (fig. 19) VIII) Vestibulocochlear (auditory)
III) Oculomotor IX) Glossopharyngeal
IV) Trochlear X) Vagus
V) Trigeminal (fig. 17) XI) Spinal Accessory
VI) Abducens (fig. 16) XII) Hypoglossal
The mammillary body (fig. 13), which is connected to the hypothalamus, is also visible in this view, as well as the infundibulum (fig. 14) (AKA pituitary stalk), which connects the hypothalamus to the posterior pituitary gland (known as the hypothalamo-hypophyseal tract). The stalk contains a rich supply of blood vessels and is chockfull of axons. If this important connection were to be severed then the portal blood vessels and the flow of releasing hormones within them would be interrupted, which would lead to “profound atrophy of the pituitary and major hormonal disruptions” (Breedlove 141). A disease known as Korsakoff’s Syndrome, which affects the limbic system by targeting the mammillary bodies and the medial thalamus, can cause anterograde amnesia due to a deficiency of thiamine (Vitamin B1) and can lead to cerebral atrophy. The temporal lobe can also be seen very well from this ventral view of the brain (fig. 15), and it contains two important limbic structures: the amygdala and the hippocampus.
The spinal cord, medulla, and pons (fig.58) are three related structures with very different functions. The medulla is just one section of the brain stem, which is responsible for relaying nerve signals from the brain to the spinal cord and controls autonomic functions (such as breathing and heart rate), whereas the pons is superior to the medulla and is responsible for auditory and vestibular (balance) and sensory/motor functions (such as sleep cycles and arousal). These structures all develop from the mesencephalon (the midbrain (fig.59)). Some of the major nuclei that make up this midbrain region are the red nucleus and the substantia nigra, which are involved in the control of body movement. The overall function of the midbrain is to act as a relay station for auditory and visual information. The diencephalon (fig. 60), which is located superiorly to the midbrain, contains the thalamus (fig. 60 a.) and the hypothalamus (fig. 60 b.). All sensory inputs to the brain (except sense of smell) come through the thalamus and the hypothalamus is directly involved with the regulation of the body’s vital drives such as eating, drinking, temperature, sleep cycles, emotional behavior, and sexual activity. The cerebellum (fig. 62), which means “small brain” and is so named due to its visual similarity to the cerebral cortex, is one of the most prominent structures of the brain and its major function is the control of voluntary movement of the body. Damage to the cerebellum results in paralyzation and impaired motor function.
Ventricular System
There are four major ventricles within the brain, which form a network of communication within the brain parenchyma (video 63). These ventricles are the lateral ventricles (right and left), the third ventricle, the fourth ventricle, and the cerebral aqueduct. The choroid plexuses, which are located within the ventricles, produce cerebrospinal fluid (CSF) which in turn fills the ventricles and subarachnoid space. The lateral ventricles communicate with the third ventricle via interventricular foramens, and the third ventricle communicates with the fourth ventricle via the cerebral aqueduct. The septum pellucidum is a fluid-filled cavity formed by the thin walls of the 2 cerebral hemispheres during early development. The CSF that is produced primarily by the choroid plexus of the ventricles “flows from the lateral ventricles, through the interventricular foramens, and into the third ventricle, cerebral aqueduct, and the fourth ventricle” (emedicine.medscape.com). CSF protects the brain against external trauma by insulating it with a protective liquid barrier. It also aids the removal of metabolites produced by neuronal and glial cell activity and supports the transport of biologically active substances (like hormones) throughout the brain.
Lateral Ventricle
Cingulate Cortex
Coronal Cuts
Substantia Nigra
Cerebral Cortex
The primary sensory cortical area that is located in the temporal lobe is the primary auditory cortex. The frontal lobe is anterior to the parietal lobe and it contains the primary motor cortex, which means that its major function is the control of movement. The occipital lobe contains the primary visual area (fig. 61). Damage to this area can cause blindness in certain parts of one’s visual field, but the person is still able to perceive shapes and objects. However, damage to the similarly-named visual association area affects one's’ ability to perceive objects and shapes and may even disrupt color vision.
60. a
60 b.
Grey and White Matter & Central Canal
Central Canal
White Matter
Grey Matter
Dorsal and Ventral Horns
Spinal Cord
Seen in these cross sections is the grey and white matter of the brain. Grey matter is darker because it is more densely packed with cell bodies of neurons. White matter on the other hand, is filled with cells with myelinated axon tracts. This myelin serves as insulation that allows neurons to be significantly more efficient and resistant to damage (Fig 20). Also seen in these cross sections is the striatum, containing the caudate nucleus and the putamen (Fig 21). The striatum along with the globus pallidus makes up the basal ganglia (Fig 22). This brain system is important in the function of movement and motor control in the body. Parkinson’s disease and Huntington’s disease are two examples of the many disorders one could get from degeneration of this brain area.
Also seen in these cross sections are fiber pathways like the corona radiata (Fig 23 & 24). One of these pathways is the corpus callosum, latin for “tough body” (Fig25). Immediately ventral to the corpus callosum is the cingulate gyrus.
Within the diencephalon, just inferior to these structures, is the thalamus and hypothalamus. The thalamus is split into several different divisions with varying functions: the medial group at in the center of the superior edge, the anterior group just anterior to it, the lateral group opposite the anterior group, the ventral group just inferior to the later group, and the posterior group on the dorsal end (Fig 26). Not too far from the Thalamus is the Hippocampus, which plays a major role in the limbic system, consolidating information for memory and aiding in spatial navigation. This brain structure resembles a sea horse, for which it is named after (Fig 27).
Also part of the limbic system is the amygdala. If this almond-shaped structure were to be lesioned, that person would most likely suffer from an inability to process emotional reactions and have severe memory deficits (Fig 28).
Above the amygdala are the lateral ventricles, or ventricles # 1 and 2 (Fig 29). Also present in the coronal section is the limbic or cingulate cortex (Fig 30). This structure is vital in emotion formation, learning, and memory and linking motivation with behavioral outcomes.
In the coronal section through the cerebral peduncle one can see the hippocampus, dentate gyrus, lateral geniculate nucleus (Fig 32), the superior colliculus (Fig 34), and substantia nigra. The substantia nigra innervates a forebrain nuclei called the basal ganglia and is important in addiction, reward, and motion (Fig 33). This structure has high concentrations of dopamine that when in deficit can cause Parkinson’s disease.

Dorsal Root Vs. Ventral Root
Grey and White Matter
The Striatum
Globus Pallidus
N.d. Photograph. Anatomy. StudyBlue. Web. 7 Oct. 2013. <http://www.studyblue.com/notes/note/n/anatomy-/deck/696994>.
Corona Radata
N.d. Photograph. Corpus Callosum and Corona Radiata. Web. 7 Oct. 2013. <http://myhomepage.ferris.edu/~griffida/anatomy%20online/a_atlas/cns/white/comm5.htm>.
Corpus Callosum
N.d. Photograph. Striatum and Globus Palladius. Web. 7 Oct. 2013. <http://homepages.inf.ed.ac.uk/anaru/research/anatomy/>.
N.d. Photograph. Striatum and Globus Palladius. Web. 7 Oct. 2013. <http://homepages.inf.ed.ac.uk/anaru/research/anatomy/>.
Grey Matter
White Matter
Lateral Geniculate Nucleus
N.d. Photograph. Our Sense of Sight. Web. 7 Oct. 2013. <http://faculty.washington.edu/chudler/eyecol.html>.
Ventral Horn
Dorsal Horn
Dorsal Root
Ventral Root
N.d. Photograph. Histological Features of the Spinal Cord. Web. 7 Oct. 2013. <http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/CNS_Histology/Spinal_Cord/Spinal_Cord_Histology.htm>.
N.d. Photograph. Nervous System Anatomy. Web. 7 Oct. 2013. <http://craniumcommander.wikispaces.com/Nervous+System+Anatomy>.
N.d. Photograph. Histological Features of the Spinal Cord. Web. 7 Oct. 2013. <http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/CNS_Histology/Spinal_Cord/Spinal_Cord_Histology.htm>.
Ventral Root

The tegmentum (floor) contains the nuclei of cranial nerves III, IV, V, and VIII (Fig 69). It also contains the VTA, or ventral tegmental area, where the mesolimbocortical pathway of the limbic system originates. This makes it an important area in reward and reinforcement behaviors involved in drug addiction. This pathway is dopaminergic, meaning it releases the neurotransmitter dopamine. The mesostriatal pathway is also a dopaminergic pathway of this area that plays a major role in motor control. Degeneration of this pathway can lead to motor issues like that of Parkinsons patients.
Not far from the tegmentum are the anterior and posterior commissures (Fig 70). Both commissures are a bundle of fibers in the white matter that form connections. The anterior commissure connects the two hemispheres, much like the corpus callosum. The posterior commissure connects the pretectal nuclei and is important in the function of the pupillary light reflex.
Also in this region of the brain is the pineal gland, or endocrine gland (Fig 71). This gland does many things including secreting the hormone melatonin which allows for the regulation of circadian rhythms. It also happens to be the part of the brain that the great philosopher Descartes believed was the center of the soul and main source of thoughts.

It’s not difficult to identify the cingulate gyrus (Fig 64), just above the corpus callosum (Fig 65). As a part of the limbic system, critical in functions like emotion and learning, the cingulate gyrus is thought to be key in directing attention. The corpus callosum just below it serves as a connector between the left and right brain hemispheres, thus facilitating interhemispheric communication (Fig65). The massa intermedia and hippocampal formation are also commissural systems in the brain. The massa intermedia connects the two halves of the thalamus (Fig 66).
The hippocampal formation, from Latin hippocampus, meaning sea horse (which the hippocampus resembles) plays a role in memory, spatial navigation, and attention control (Fig 67). Much of what we now know about the hippocampus comes from research done on Henry Molaison, also known as H.M. To cure his epilepsy, Molaison had his hippocampus, hippocampal gyrus, and amygdala removed and shortly after experienced severe amnesia with no other side effects. After the surgery he couldn’t recognize the hospital staff, didn’t know his way home, and couldn’t remember facts of things he had just read, but otherwise seemed completely fine. It was concluded that his short-term and procedural memory remained intact, as did long-term memories that existed before the surgery. However, he could no longer create new long-term memories. This tells us that the hippocampus must play a large role in memory formation.
The tectum (roof) is composed of the superior and inferior colliculi of the corpora quadrigemina (Fig 68). These structures process sensory information, specifically visual information in the superior colliculus and auditory information in the inferior colliculus. Naturally, the inferior colliculus is closer to the dorsal (back) aspect of the brain, as it is inferior (below or behind) to the other colliculi.
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