Sheep Brain Dissection

1. 

2. Cerebrum: higher brain function (thought/ activity)

Cerebellum: coordinate/ regulate muscular activity

Brain stem: transport information to and from the brain

3. Myelin increases the speed of nerve function.

4. 

5. Thalamus: involved in sensory/ motor signal transportation and the regulation of consciousness and sleep

Optic nerve: carries images from our retina to our brain so they can be interpreted

Medulla oblongata: helps regulate respiration and circulation

Pons: connector for cerebrum and cerebellum

Midbrain: part of the CNS associated with vision, hearing, motor control, sleep/wake, alertness, and temperature regulation

Corpus callosum: connects the left and right hemispheres of the brain

Hypothalamus: produces many of the body’s essential hormones

6. 

Relate & Review

In the brain dissection, we cut the sheep brain in half and identified the different parts of the brain. We used pins to mark the different sections. The brain was weirdly squishy, totally different to what I expected but very interesting. The brain also looked really similar to diagrams, which sometimes what we dissect doesn't, but the little parts of the brain were a little difficult to identify. It was also weird how similar the sheep brain was to diagrams of the human brain. We did figure it out in the end though. It was really cool to hold an actual brain and dissect it, I think we're all really lucky to have been able to do this lab.

The brain cut in half

The brain with all the pins in it, identifying the different parts

The initial identification of major parts and front/ back

 

Sheep Eye Dissection

In the lab, we dissected a sheep eye. The eye below is fully intact, the cornea covering the front of the eye, and the sclera covering the rest. 

First we cut away any fat (yellow) or muscle left on the sclera, then we cut into the sclera. It was really tough and thick - much tougher than I expected it to be. After we finally made it through the sclera, we cut all the way around it, turning the eyeball into two hemispheres.

 We had to be careful to not cut the optic nerve. We got really lucky in that our cut was right where we wanted it to be. On the anterior half (left in photo), we had the part of the eye that is visible to the world. In it, was a gelatinous vitreous humor.

The vitreous humor maintains the shape of the eye. On the posterior half (right in photo) the retina on our sheep eye was still intact over the choroid coat.

 The retina is where images focused by the lens are collected. The underlying choroid coat nourishes the back of the eye. It has the tapetum lucidum, which is bluish in color and gives animals their night vision. It was fascinating to see that the retina is only connected to the eye in one spot, the blind spot. The blind spot is the spot on the retina where images cannot be focused. We then tipped the vitreous humor out of the front half of the eye. It tipped out quite easily, and we were met with the lens.

The lens focused light and is connected to the eye by suspensory ligaments. The lens will flatten or thicken depending on what needs to be seen. Now, we could also see the other side of the cornea. It was cloudy, because it was not in the living state. It is also to focus light. We could also see the ciliary body underneath it, which looked a bit like the underside of a mushroom.

The iris was brown/ black in colour, and overall the cornea had an oval shape, where humans have a circular cornea. 

Clay Brain

This is the clay brain model our group made in class. It was a model of the left hemisphere along the sagittal plane, and the right cerebral hemisphere. The left hemisphere included the diencephalon, the thalamus, the hypothalamus, the pineal gland, brain stem, midbrain, pons, medulla oblongata, the cerebellum, the spinal cord, the pituitary gland. The right cerebral hemisphere included the occipital lobe, parietal lobe, frontal lobe, cerebellum, transverse fissure, parieto-occipital sulcus, postcentral gyrus, central sulcus, precentral gyrus, and lateral cerebral sulcus.

The Woman with a Hole in her Brain

This article just goes to show how adaptable the human body is. The featured woman was 24 years old when it was discovered she is missing her whole cerebellum and despite a few struggles with motor skills and speech, she manages just fine. It begs the question: could we survive with other parts of our brain missing? The article says it is not unheard of to be missing parts of the brain. We know that a missing cerebellum creates a few impediments, but what does a missing brain part mean for longevity, or long-term health concerns?

From my research, it appears that theoretically a person could survive without a parieto-occipital sulcus. The parieto-occipital sulcus is the ridge between the parietal lobe and the occipital lobe. person may also have a connected parietal and occipital lobe, leading to a whole new breed of problems. It appears to help with planning things - so maybe a person would struggle with forethought without it. The frontal lobe is also involved in planning, so it is possible that if the parieto-occipital sulcus was missing, the frontal lobe could just take over.