Reflexes Lab

A sensory neuron carries the message from the receptor to the central nervous system (the spinal cord and brain). A motor neuron carries the message from the central nervous system to the effector. For instance, in the knee-jerk reflex arc the sensory

neuron directly connects to the motor neuron in the spinal cord.

Reflexes tested:

The photopupillary reflex is a reflex that adjusts the size of the upil in order to adjust for the varying degree of light in the area. To test this, we had a classmate cover his eye and cover it. After 5 minutes he uncovered his eye and the results are as follows:

The reason the response occurred was because the eye detected the intensity of the light and corrected for it, allowing less light into the eye. This ultimately reduced the stress on the eye.

The knee jerk reflex is a sudden involuntary forward movement of the lower leg that can be produced by a firm tap to the tendon located just below the kneecap. The term is loosely applied to any muscular response or belief that is automatic rather than thought. To test this we tapped our classmates knee. The results are as follows:

The reason this response occured was due to the pressure on the tendon. Remember that the knee is like a lever, and once the tendon is pressed in, it shortens, pulling up the knee.

The blink reflex is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though could result from any peripheral stimulus. To test this reflex we had our classmate hold surran wrap up by his face and stare at us throwing cotton balls at him, the results were as follows.

The results were due to speed and direction of the objects we were throwing at him. If we were to throw the cotton balls at his chest, he would likely not blink.

The plantar reflex is a superficial reflex obtained by stroking the skin on the lateral edge of the sole of the foot, starting at the heel advancing to the ball of the foot then continuing medially to the base of the great toe. The normal response is flexion of all the toes. On our test subject, she did not flex her toes. The reason she did not flex was likely due to the absence of the nerve responsible for the action in her foot

Finally, we tested our somatic nervous system by trying to catch a ruler as it fell

Our response times were as follows:

As shown in the graph, when asked to text while trying to grab the ruler, reaction times were more than doubled. This was because we cannot physically do two things at once, instead, we can only switch off from one task to another very rapidly.

Brain Dissection Analysis

In this lab, we dissected a sheep brain. As we dissected the brain, we followed certain guidelines. As a part of these guidelines, we had to answer questions as we completed each step. The following are the guideline questions and my appropriate responses:

Question 1:  Take a picture with your pins in place.  Draw a detailed sketch of the brain and label each of the structures you just identified on that paper.   

Question 2:  What is the function of each of these structures?  Make a table that describes each of these parts and their functions.

Cerebrum-  Allows for a higher level of thinking, such as emotions and thought and action.

Cerebellum- receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements

Brainstem-  functions include regulation of heart rate, breathing, sleeping, and eating

Question 3:  What is the function of myelin in a neuron?

Myelin helps the neuron conduct its electrical signal faster by decreasing the channels the action potential has to cross. Imagine taking a piece of paper (representing an axon) and folding it into thirds. The middle portion is the ‘myelin’. Take the the two ends that are not the myelin and connect them. This is essentially the space that the electrochemical signal now has to travel due to the myelin.

Question 4: Take a picture with your pins in place.  Draw a detailed sketch of the cross-section and label each of the structures from the table above.

(picture taken after longitudinal cut of the corpus callosum)  

Question 5: What is the function of each of the structures you pinned in Step 8?  Make a table with the structure name and the function (written in your own words).

Thalamus (Yellow) - works to correlate several important processes, including consciousness, sleep, and sensory interpretation

Optic nerve (Green) - to transfer visual information from the retina to the appropriate vision centers of the brain via electrical impulses (right eye to left brain and vise versa)

Medulla Oblongata (Pink) - regulates breathing, heart and blood vessel function, digestion, sneezing, and swallowing

Pons (Purple) - control center for important nerves in the body

Midbrain (Blue) -  the portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation

Corpus Callosum (Red) -  to hold both hemispheres together

Hypothalamus (Brown) - the portion of the brain that regulates hormones

Question 6:  Make a detailed drawing of your cross section (of the cerebrum), and also take a picture.  Shade the gray matter and white matter to distinguish between them in your drawing.  Label the gray matter and white matter in your drawing.

And now time for the fun part, my personal perspective on the lab:

During this lab, I was the one who actually performed the cuts. First we cut through the corpus callosum, the tissue that holds the hemispheres together. I then proceeded to cut the brainstem in half. After doing so, we identified and labeled the structures in question # 5. After identifying the structures, we removed the pins and cut the brain once more across the hemispheres to reveal the grey and white matter.

I really enjoyed this dissection as we got to relate it back to our previous notes. For example, we had recently learned about myelinated vs unmyelinated nervous cells and their roles in the brain. Another example is the the identification of the different portions of the brain. To be honest, this was one of the more gratifying things about the dissection as the group as a whole was able to use anatomical terms we learned from first semester (such as anterior and posterior) and apply them in the dissection. Although the material may not have been taught in correlation to the specific dissection or what have you, we were still able to connect the major themes from the lectures. Due to the relatively short nature of the dissection, there is little more to connect with. However, the lab was still very interesting as we got to dissect a friggin brain!

Sheep eye dissection

1. Cornea- the transparent layer in front of the eye that protects it (was very hard and almost like a plastic during the dissection)
2. Sclera- the white outer layer of the eyeball and serves to protect the eye/contain its components (based off of observation) and connects the muscle
3. Optic nerve-  each pair of cranial nerves connect at the back of the eye; transmit signals to the brain from the retina at the back of the eye
4. Iris- a circular structure that controls the diameter of the pupil, thus the amount of light that enters the eye
5. Pupil- hole at the center or the iris that allows a certain amount of light into the eye
6. Ciliary body- controls the shape of the len, tissue that supplies eye with oxygen
7. Choroid- the pigmented vascular layer of the eyeball between the retina and the sclera;
8. Tapetum lucidum- lying right behind the retina, the tapetum lucidum is a refractory material that allows animals to see in the dark by reflecting the light (reason why animals eyes seem to flash back when photos are taken of them)
9. Retina- essentially the film in the camera; very thin and was VERY easy to peal back in the dissection
10. Lens- transparent, light bending structure, felt like a marble almost, like a marble split in half
11. Vitreous humor- clear gel that fills the space between the lens and the retina; is the ‘cushion’/filler/place holder for the lens  

Bird Brain

Bird Brains by Candace Savage

1. A thesis is established for the works could be that regardless of our relatively low expectations of birds, they are actually quite smart. The book supports this claim with relatively scientific evidence. It does this by proposing an idea and following it up with quotes from the conductor of the experiment. Usually the quotes are fairly specific, however I noticed that the quotes rarely explained the why to the results. This could be attributed to “anthropomorphism,” or,  “the too-easy ascription of human emotions and mental processes to nonhuman animals” (19). Although their results may have helped prove the thesis of the book, none of the information made connections to their ability of higher thinking, rather explained what the results meant. Personally I found that by doing this, the book almost took away the some credibility. Occasionally however, there were moments where the author did fill in some gaps as to why (I will cover this later). A theme of the book was this idea of learned versus innate characteristics. I found that the best example was in the story of Konrad Lorenz. Having a collection of tame Jackdaws, Lorenz decided to introduce a new fledgling. When he grasped the new bird, completely tamed members of the colony attacked him, pecking at Lorenz’s hand until the new jackdaw was released. However, he later learned that, “young jackdaws  had no inborn reaction to predators,” and instead, “had to learn from their parents’ example what to trust and what to fear… if the adults responded to someone or something with alarm, the young birds quickly developed an identical phobia” (26).  
1. Ultimately, to support the claim that birds are smarter than we perceive, Savage uses multiple subtopics; resource management, generic shape and pattern matching, and parental features. Although the birds’, “cerebral cortex (the organ of higher thought in humans and other mammals) looked distressingly small and poor developed,” they still “share the ‘cognitive capacities’ of many primates.” (26,18). So why do we seem regard primates more highly than birds. Interestingly enough, the birds, “brain to body ratio equals that of dolphins and nearly matches our own” (29)! I don’t know about you, but the insult, “bird brain,” just got a whole lot less offensive.
2. The book mentions several times about the plasticity of brains and how the bird is capable of learning new things/ modifying old. For example, a magpie was attempting to build a nest in a confined area. Instead of using the material that the male partner had brought, the female independently ventured out to gather softer materials such as newspaper and grass. Ultimately, instead of making the tough outer portion of the nest, the female magpie made only made the soft inner portion so that the nest could fit in the confined space. Another example of the plasticity of the brain is in the example of the blue jay. The blue jays have been known to build their nests lower to the ground, however, younger birds may try to build their nests higher up into the canopy to expose their nests to the sun. Although this may benefit them, it also puts them at a higher risk of predation. As a result, “the frequency of nesting in exposed locations dropped from eighty percent to fifty five percent after individuals suffered their third predatory experience when nesting in exposed locations” (47). Another way the reading connect to the class was through identification of the portions of the brain. As mentioned above, the cerebral cortex is the basis for all higher thinking and that is why the bird’s is relatively small. However, there was an adaptation that did allow for complex thinking. Not found in mammals, a miniature cerebral cortex can be found in birds.
3. If I could ask the author two questions they would probably be:
1. What can be said about the mating habits of the birds? Are they genetically imprinted in the bird’s mind or is it a learned characteristic? Can a bird be taught the ‘dance’ or ‘song’ of another bird species.
2. Can a bird species really learn and or make alternate neural pathways to adapt to its environment? Although the jay may move its nesting ground after the 3rd predatory encounter, is it really the cortex at work? Or is it still imprinted in the jays brain?
4. I really enjoyed this reading. Although I read it at 4:00 am, I had absorbed almost all of the information that I had read. Infact, I was probably more critical of the reading because it was so late at night. In my opinion, the reading was very realistic as it contained scientific evidence as well as facts about the information discussed (for example the cerebrum, how nests are built and so on). For starters, I will discuss the things that I liked. Specifically, I loved how the book incorporated images to accompany the subjects it discussed. It really helped visualize the material. Concepts that I enjoyed learning about were how the bird brain has a ‘mini cerebral cortex’ that is not found in mammals. I also enjoyed learning about how the certain birds adapted to their surrounding environment. Although it cannot be proven that the birds actually adapted to their environment, I found it to be an interesting hypothesis. I also liked how the book went into detail as to how birds identify their young. I had been interested as to how they recognized their own chicks among the rest of the newborns. What I did not like however, was how the book almost contradicted itself. One second it’s saying that birds are intelligent as they can recognize shapes, yet counters the point by mentioning anthropomorphism. The book then continues along the lines mentioning the interesting mental powers of certain birds. To me it just seemed counter intuitive.
5. The effects of this work are in the grey zone. Once again, there have been speculations of birds having a higher level of thinking, but the general opinion is that they do not. The book helps to explain and clear up these speculations and make some of the grey area black and white, narrowing bringing us closer to definite answer. The practical application of this book is that it allows an ordinary person to have an new appreciation for birds. Ultimately, I believe this book will be apart of the foundation for the research that eventually proves or disproves whether or not birds have a higher level of thinking.

Clay Brain

In this activity, we made a brain out of clay, who could have guessed with title. Essentially what we did to create the brains was look up the images of the brain along the left hemisphere along sagittal plane and the right cerebral hemisphere. We made sure to get the basic and most familiar lobes and other structures down on the cardboard first, then built our way to the more complex structures. Eventually we got to the point where we needed to label the structures, so me, being the lazy guy that I am, cut out the grading sheet and pasted it onto the cardboard. We then pulled pieces of the play-dough from each structure and placed it on the appropriate label. Although this was supposed to save us time, we still ended up finishing the project last. 

Hole in the Brain

So recently I read an article on a woman who was missing her cerebellum. Apparently she had the space that was originally taken up by the cerebellum was replaced with a fluid. I found this remarkable and so did the article as only 9 other people have survived such a condition into adulthood. Personally, I was curious as to what would happen if the fluid drained and if the fluid had made any other complications, or if it was actually beneficial in other ways (knowing the cleansing power of the fluid). Then I wondered what would happen if the pons part of the brain was missing.

Pons is located in the brain stem and is involved in sensory analysis. It is also involved in regulating levels of consciousness and sleep. Injury to pons is known to cause comas as well. Given all this information, I would assume that if the pons portion of the brain stem were to be missing, or removed, the patient would likely enter a coma, and likely lead to death. Unlike the cerebellum, the pons most likely could not be replaced due to its essential function.

Chicken Dissection Lab

Unfortunately I was absent for this assignment/dissection, however, I am still educated on the material. I asked class members who did do the lab, how it went and how the process of determining muscles went. They all, for the most part, referred to their in-class notes handouts of the human body. In general, the size of the muscles differed from chickens to humans, however the locations stayed the same. For example, the pectoralis major was far larger in the chicken than in the human. This difference is likely caused by the fact that to lift itself off the ground, the muscle would have to be larger. This causation ultimately results to form fits function. As the chicken needs to lift itself off the ground, the muscles need to be stronger, and therefore larger. In contrast, humans are far less reliant on the pectoralis major as we don't fly (if only). Some characteristic similarities are are in the trapezius and the deltoid. An important reminder is that muscles grow and atrophy depending on usage and resistance the muscle receives. This can help determine the physical activity and nature of the animal, for instance our largest muscle is the gluteus maximus which is due to our nature as a 2 legged animal.  

Not only are muscles used for movement, but so are bones and tendons. Muscles connect to the bone through tendons and help to show increase the range of motion and release tension. The bones allow for stability. As muscles contract, certain muscles contract as others relax. The muscle that contracts is called the agonist whereas the muscle that relaxes is the antagonist. For example in elbow extension, the triceps contracts, whereas the biceps relaxes. The lever system in this interaction allow the bicep to contract with less stress. These levers vary in class; each class identifies a different type of lever system.

Just as levers vary in class, so do tendons. There are two types, named, the origin, and the insertion. The origin is the end that does not move when the muscle moves while the insertion is the tendon that does move when the muscle contracts. The origin also tends to be more proximal while insertion tends to be more distal. The origin of a muscle attaches to a less movable bone whereas the insertion of a muscle attaches to a more moveable bone. The insertion also has less mass than the site of origin.

• The pectorals are predominantly used to control the movement of the arm, with the contractions of the pectoralis major pulling on the humerus to create lateral, vertical, or rotational motion
• large muscle in the upper chest, fanning across the chest from the shoulder to the breastbone

• thin, flat muscle found immediately underneath the pectoralis major

• The primary actions of this muscle include the stabilization, depression, abduction or protraction, upward tilt, and downward rotation of the scapula

1. The muscle also covers the lower tip of the scapula, or shoulder blade. When flexed, the muscle works at extending, adducting and rotating the arm.
2. One of the widest back muscles. Broad muscle bands cross the back, providing upright posture support. The trapezius muscle is a postural and active movement muscle, used to tilt and turn the head and neck, shrug, steady the shoulders, and twist the arms

• The deltoid muscle is responsible for the brunt of all arm rotation and allows a person to keep carried objects at a safer distance from the body.

2.  The triceps run along the humerus (the main bone of the upper arm) between the shoulder and the elbow. When the triceps are contracted, the forearm extends and the elbow straightens; if the triceps are relaxed and the biceps flexed, the forearm retracts and the elbow bends.

3.  The biceps brachii is a bi-articular muscle, which means that it helps control the motion of two different joints, the shoulder and the elbow. The function of the biceps at the elbow is essential to the function of the forearm in lifting.

1. Also called the brachialis anticus, its primary action is to flex the forearm muscles at the elbow
2. flexes the wrist and adducts it

1. Is a muscle located on the back portion of the lower leg, being one of the two major muscles that make up the calf. The flexing of this muscle during walking and bending of the knee creates traction on the femur, pulling it toward the tibia in the lower leg and causing the knee to bend.
2. It serves to steady the leg upon the foot.
3. the largest muscle located in the anterior compartment of the leg. Helps with dorsiflexion, which is the action of pulling the foot toward the shin.

- a group of muscles located in the front of the thigh

- The quadriceps assist in extending the knee

1. The muscle helps flex, adduct, and rotate the hip.
2. a tiny muscle, inferior to the iliotibial band.  It also provides lateral stability to the knee.

1. It is found on the back of the thigh and runs from the base of the pelvis to the back of the tibia, one of the bones that make up the lower leg. The muscle has several functions, including enabling the leg to flex and rotate, and serving as a thigh extensor
2. One of three hamstring muscles that are located at the back of the thigh. These three muscles work collectively to flex the knee and extend the hip.

1. The biceps femoris muscle is a double-headed muscle located on the back of thigh. It is important for knee flexion, internal and external rotation, and hip extension.
2. A large muscle group that includes the four prevailing muscles on the front of the thigh.They are crucial in walking, running, jumping and squatting. Because rectus femoris attaches to the ilium, it is also a flexor of the hip.