Pons medulla relationship in human and sheep cross

pons medulla relationship in human and sheep cross

Match the letters on the diagram of the human brain (right lateral view) cerebral hemispheres pons midbrain cerebellum medulla oblongata diencephalon 2. site where medial fibers of the optic nerves cross . When comparing human and sheep brains, you observed some Pons/medulla relationship. the cerebral hemispheres, diencephalon, brain stem, and cerebellum on a and sheep brain. .. dissectible model or a coronally or cross-sectioned human . relationship of the basal nuclei to the thalamus and the lateral and third ventricles . When comparing human and sheep brains, you observe some profound Pons/ Medulla Relationship. Human: Pressed up against the corpus callosum.

pons medulla relationship in human and sheep cross

Each contains a cerebrum, cerebellum, and brain stem. The sheep brain is smaller, weighing around grams, or about one-tenth of the weight of an adult human brain, though it is still large enough to be easily dissected. The cerebrum is more elongated in sheep than in humans, and the cerebellum and brain stem are located behind the cerebrum, instead of being tucked below it.

This is because sheep, being four-legged animals, have a horizontal spine, while humans stand upright with their spines vertical. Frontal Lobe A major difference is that the frontal lobe in the sheep brain is much smaller relative to the overall brain size, accounting for only a few percent by volume compared to about 25 percent in the human case. The frontal lobe is connected with higher cognitive functions, such as abstract thinking and analysis.

The relative size of the frontal lobe, as well as the number of ridges in the cortex, are indicators of species intelligence. Though the sheep has generally been regarded as an unintelligent animal, it is increasingly recognized that sheep are able to perform some advanced tasks, such as remembering the faces of other sheep and humans for two years or longer. Olfactory Bulb The sheep, like many mammals, has a more developed sense of smell, or olfaction, than humans do. The olfactory bulb is the part of the brain located underneath the frontal lobe that is responsible for relaying sensory information from the nose to the rest of the brain.

Look at the dorsal aspect of the brain and the spinal cord that extends from it. Have the instructor or lab assistant point this out to you. You should be able to see that the dorsal surface of the medulla, and the spinal cord, are marked by parallel, longitudinal striations formed by columns of fibers. The most medial pair of these columns is the fasciculus gracilis; the more lateral pair of columns is the fasciculus cuneatus.

Have the instructor or lab assistant point these out to you, if you are unclear about their locations. Collectively, these two fasciculi are also known as the dorsal columns. The axons in these columns are ascending sensory fibers, carrying for the most part, light touch sensations from the body and limbs. Click on the image at the left for an expanded view.

Barrett Sheep Brain trannycams.info

Follow the dorsal columns rostrally until they just begin to disappear beneath the cerebellum; you will find two small mounds. These two swellings are the nucleus gracilis and the nucleus cuneatus. Remember from Lab 1 that nuclei are collections or clusters of cell bodies located within the CNS.

The axons in the dorsal columns synapse on cells located in the nucleus gracilis and nucleus cuneatus. The axons of the cells residing in the two nuclei then exit the nucleus, decussate cross the midline and project to the contralateral thalamus where they synapse on cells in the ventroposterolateral nucleus VPL. The axons of the cells located in VPL project to somatosensory cortex the post-central gyrus.

Differences Between Human and Sheep Brains

Before you continue, stop to draw a schematic of the path that somatosensory information takes from spinal cord to postcentral gyrus. Include the nucleus gracilis, nucleus cuneatus, VPL and postcentral gyrus in your drawing. Important features of the ventral surface. In Lab 1, you located a large fiber structure, the cerebral pedunclesjust anterior to the pons. The oculomotor nerves can be seen exiting from them.

Recall that the cell bodies that give rise to the axons in the cerebral peduncles are found in motor cortex and that they are called pyramidal cells.

The fibers in the cerebral peduncles continue to the spinal cord. They can be seen on the ventral surface of the medulla, where they are known as the pyramidal tract.

pons medulla relationship in human and sheep cross

Stop, now, and mentally trace the pyramidal tract from cerebral cortex to spinal cord. The pyramidal motor system, one of two major motor systems in the body is in control of fine, discrete and voluntary motor activities such as writing, typing, or playing the piano. Other motor systems are concerned with gross motor movements, such as, dancing, walking, or waving goodbye. This may be a good time to restate conventions concerning names of tracts in the CNS.

If you keep the rule 'from-to' in mind, you will always be able to tell the site of origin and destination for a given tract. The first name in the title indicates the site of origin of the tract, while the second name indicates the tract's destination.

The tract known as the corticospinal tract, according to the rule, originates from neurons whose cell bodies reside in the cortex and project their axons to the spinal cord. The trapezoid body consists of fibers carrying information from the right ear to left auditory cortex and information from the left ear to right auditory cortex.

The trapezoid body is to the auditory system what the optic chiasm is to the visual system. Unlike somatosensory cortex, the auditory and visual cortices receive bilateral input, that is, each projection site receives information from both ears or both eyes, respectively.

If it has not been stripped away, you will find the VIII cranial nerve, the vestibulo-cochlear or auditory nerve at the most lateral extent of the trapezoid body.

On the ventral surface of your sheep brain, locate the very prominent swelling between the trapezoid body and the cerebral peduncles, the pons. Its name is derived from the Latin word, pons, which means 'bridge. Pyramidal tract fibers descending from motor cortex to their destination in the spinal cord are one example of these fibers of passage.

Immediately posterior to the the cerebral hemispheres, you find the cerebellum, a large, complex structure concerned with all levels of motor coordination. The cerebellar surface is characterized by intricate, extremely fine convolutions called folia. The folia are analogous to the gyri of the cerebral hemispheres. Like the cerebral hemispheres, the cerebellum has an inner core of white matter.

Differences Between Human and Sheep Brains | Animals - trannycams.info

In the cerebellum this inner core of white matter is called the arbor vitae. Click on the image below for a larger view. The white-matter core consists of axons projecting to and from the cerebellar hemispheres, the spinal cord, sensory and motor cortices, and other regions of the brain. The cerebellum sends information to the brain and spinal cord via axons that exit from the cerebellum. In this way, we have information coming into the cerebellum that helps guide cerebellar control of our motor behavior.

Without an intact cerebellum, you would find it difficult to walk, maintain a sense of balance, or to perform a complex behavior, such as, hit a tennis ball with a tennis racket, an action that requires hand-eye coordination and timing. The cerebellum has other important functions; it is important for establishing skill memories and for the occurrence of classically conditioned responses.

Nestled between the cerebellum and the cerebral hemispheres are two prominent elevations sitting symmetrically on either side of the midline. You may have to pull your cerebellum gently and caudally to reveal them. Collectively, these four structures are called the corpora quadrigemina 'bodies of four twins'but it is easier to remember them in their pairwise configurations: This region of the midbrain is also called the tectum 'roof'because the colliculi 'little hills' form the roof, or upper boundary of the Aqueduct of Sylvius.

Look at the figure connected to this link to see the relationship between the colliculi tectum and the aqueduct of sylvius. The figure will clarify the location of the colliculi. If you are unable to see any of the structures named in this paragraph clearly and easily, seek help from the instructor, or lab assistant. On the ventral surface of the brain, at the midline just anterior to the oculomotor nerve, locate the small, but distinct, tissue that looks like the tip of a tongue.

Cells in the mammillary bodies are particularly vulnerable to alcohol. Autopsies have shown significant destruction of the mammillary bodies in chronic alcoholics suffering from a severe memory disorder known as Korsakoff's syndrome. Some neurologists believe that the mammillary bodies are involved in memory processes. While the mammillary bodies form the caudal limit of the hypothalamusits anterior border is marked by the optic chiasm.

The general outline of the hypothalamus from the ventral aspect, thus, assumes a diamond-like configuration. Although the hypothalamus is not a very large structure, it is quite complex.

The hypothalamus contains many different nuclei that are concerned with regulation of temperature, hunger and satiety, sexual behavior, and, perhaps, even sexual preference.