Chicken Dissection

In this lab, we dissected a chicken in order to learn about its muscles.  First, we turned it on its back and removed the skin so we could see its pectoralis major. We then cut the pectoralis major down the midline to expose the pectoralis minor.

We then turned the chicken over in order to see the trapezius, which pulls the shoulders back, and the latissimus dorsi, which extends the arm.

After that, we cut the skin off the wing in order to observe the deltoid, biceps brachii, and triceps humeralis.

Further down the wing, past the elbow joint, we saw the flexor carpi ulnaris and brachioradialis. 

We then moved on to the leg and the numerous muscles there, including the sartorius, iliotibialis, biceps femoris, semimembranosus, semitendonosus, and quadriceps femoris.

The final muscles we looked at were the gastrocnemius, peroneus longs, and tibialis anterior.

Muscle	Function (Chicken)	Function (Human)
Pectoralis Major	Pulls wing down	Adducts, flexes, and rotates arm
Pectoralis Minor	Pulls wing up	Abducts arm, depresses shoulder
Trapezius	Pulls shoulders back/shrugs shoulders	Extends head, elevates/depresses scapula, adducts arm
Latissimus Dorsi	Extends wing	Extends arm
Deltoid	Raises wing	Raises upper arm
Biceps Brachii	Flexes wing	Flexes elbow joint
Triceps Humeralis/Brachii	Straightens wing	Extends elbow joint
Flexor Carpi Ulnaris	Flexes hand & alula	Flexes/adducts hand
Brachioradialis	Pulls hand back	Flexes forearm at elbow, pronation/supination
Sartorius	Flexes thigh	Flexes thigh, allows legs to cross
Iliotibialis (birds) or Tensor Fasciae Latae, Gluteus Maximus, and Iliotibial Tract (humans)	Extends thigh, flexes leg	Extends thigh, flexes leg
Biceps Femoris	Flexes leg	Flexes leg
Semimembranosus	Extends thigh	Extends thigh
Semitendonosus	Extends thigh	Extends thigh
Quadriceps Femoris (birds) or Vastus Lateralis, Intermedius  and Medialis, and Rectus Femoris (humans)	Flexes thigh, extends lower leg	Flexes thigh, extends lower leg
Gastrocnemius	Extends foot, flexes lower leg	Extends foot, flexes lower leg
Peroneus Longus	Extends foot	Extends foot
Tibialis Anterior	Flexes foot	Flexes foot

The many similarities between major human and chicken muscles astonished me. There were a few small differences, but for the most part, chicken muscles perform very similar functions to  their human counterparts; most even share the same names. The muscles of chickens and humans also function in the same way; as the muscle contracts, the tendon of the insertion is moved toward the origin, flexing the joint.

Reflexes Lab

Some motions are automatic, things we do without thinking about, and can't stop even if we want to- like blinking if something is town at our face. These are called reflexes, and they work by sending a signal to the spine, which sends a signal directly back to the muscle, bypassing the brain entirely. In this lab, we tested some of our different reflexes.
First, we tested our photo pupillary reflex- the reflex that controls the contraction of our pupils in response to light. We covered one eye, then shined a light in it and watched, and we saw the pupil constrict. Humans have probably evolved this reflex to prevent us from being blinded by bright lights.

After that, we tested our patellar reflex, which is the one doctors test when you go in for a physical. It causes the lower leg to suddenly kick out in response to a sharp tap to a spot under the knee. It is sometimes hard to find, but my lab partner and I were able to find it, tapping the knee in the right place and causing the lower leg to suddenly kick out. I don't know exactly why this happens, but I think it could be some sort of defense mechanism.

We also tested our blink reflex by throwing a cotton ball at each other's faces while stretching a piece of plastic in front of our eyes to protect them. Obviously, we both blinked. This reflex evolved in order to protect our eyes from harm.

After that, we tested the reflex in our foot, drawing an object across the bottom of our feet and making our toes curl. This probably also evolved in order to protect our feet.

Finally, we tested our reaction time by having our partner drop a yardstick and catching it, then figuring out our response time. We did this both normally and while texting, and my average response time was slower by 0.03 seconds when texting, increasing from 0.27 to 0.3 seconds.

Brain Dissection

In this lab, we dissected a sheep's brain. We started by removing the meninges, a layer of tissue that surrounds the brain and forms the blood brain barrier. Then, we observed the outside of the brain, identifying and labeling (with pins) several different structures we could see. After that, we cut the brain in half by severing the corpus callosum and identified more structures inside. Finally, we took a cross section of the brain in order to see the white matter, which is an area containing more neurons, and gray matter, which contains fewer.
This dissection was very interesting. Even though I knew that the corpus callosum was the only thing connecting the two hemispheres, it was still surprising to look down in between the hemispheres and see only one small white thing at the bottom holding them together. I also liked looking at the white and gray matter, as it was interesting to see where the neurons were most concentrated.

Picture and drawing of outside of brain

*Black pin is posterior, white pin is anterior

Part of Brain	Pin Color	Function
Brainstem	Silver	Filtering/directing information, breathing, circulation, digestion
Cerebellum	Green	Motor control, coordination, muscle memory
Cerebrum	Yellow	Integrating/interpreting data

In a neuron, myelin surrounds the axon, helping the signal to go faster.

Picture and drawing of left hemisphere

Part of Brain	Pin Color	Function
Pons	Silver	Breathing/digestion
Medulla oblangata	White	Balance/coordination
Optic Nerve	Green	Sending information from eyes to brain
Midbrain	Blue	Filtering/directing information
Thalamus	Yellow	Sorting data
Hypothalamus	Black	Maintaining homeostasis
Corpus callosum	Red	Communication between hemispheres

Picture and drawing of brain cross-section

Sheep Eye Dissection

The eyeball

Cornea and sclera visible 

Retina (peeling off), choroid, and tapetum lucidum (top)

Lens and vitreous humor (bottom)

The lens

First, we looked at the outside of the eye, where we saw the sclera (the white of the eye), the cornea (which is where the light goes through), and lots of fatty tissue on the back. We then cut off most of the fatty tissue in  order to see the optic nerve, which sends electrical impulses to the brain, which then interprets them, letting you see. We then cut the eye in half, so we could see the retina, which converts the light hitting it into electrical impulses using cells called rods and cones, on the back, and in the middle of it was the blind spot, which is where the retina meets the optic nerve. We then peeled back the retina so we could see tapetum lucidum, which helps to give the sheep better night vision, and the choroid, which functions as a supplier of blood for the eye. We then looked at the front half of the eye and saw and the lens, which bends the light coming in from the pupil, and the vitreous humor, a clear jelly-like mass that helps the eye retain its shape. We then took out the lens and vitreous humor so we could see the ciliary body, which is a muscle that controls the shape of the lens, the suspensory ligament, which connects the lens and ciliary body, and the pupil. 

By dissecting the sheep's eye, we were better able to understand the path of light through the eye. We saw the cornea, where light first passes through, and the pupil, which is the hole between the cornea and lens, as well as the iris, which controls the size of the pupil. We also saw the lens, which bends the light, and the vitreous humor, which light also passes through. The size of the lens surprised me; I thought it would be much thinner, and a little smaller. Finally, we saw the retina, which is where the light hits and is transferred into electrical impulses, and the optic nerve, which caries those impulses to the brain.

Parts of the eye

Nervous System Power Hour Reading

Name of Book: Mastermind: How to Think Like Sherlock Holmes by Maria Konnikova

Name of Chapter: The Scientific Method of the Mind

In this chapter, Konnikova discussed the method of deduction employed by Sherlock Holmes, and how we can apply it in our own lives. She claims that Holmes has trained himself to use the scientific method to evaluate his every thought and action- something that, to a normal person, sounds exhausting, but has become second nature to Holmes. Most of us are reactive, relying on instinct and simply responding to a situation. This book aims to teach us how to become reflective, just like Sherlock Holmes, and consider what we see before we respond.

This reading relates to ideas of neuroplasticity that we have been learning about. The idea that we can  alter our way of thinking simply by practicing shows that we really can create neural pathways and strengthen them through continual use, just as we learned from "A Woman Perpetually Falling"

A Woman Perpetually Falling

"A Woman Perpetually Falling" starts off by describing a woman who has no sense of balance, and therefore always feel like she's falling, even when lying down. She can't walk, can't even stay upright, without losing her balance and falling. Then, she begins working with Dr. Bach-y-Rita, who has designed a hat which acts as a temporary vestibular system (sense of balance). Surprisingly, when she takes off the hat, she retains that sense of balance for some amount of time- an amount of time that increases each time she uses the hat. Dr. Bach-y-Rita ascribes this to neuroplasticity, explaining that the brain is forming new pathways which grow stronger each time that she puts the hat on and uses the pathways. Neuroplasticity, though not a new concept, has only recently come to be accepted by the scientific community; previously, scientists believed that there was one and only one location in the brain for each function, ignoring any evidence to the contrary. However, as Bach-y-Rita discovered, the brain can often reorganize itself.
This was very interesting to me, especially because we have just been learning about functions of different parts of the brain in class. However, after reading through the article, I realized that those locations were probably where those functions are primarily associated with those locations, but could also take place in another part of the brain if necessary.

There were some quotes that stuck out to me in the reading. The first was that the hat, the machine that allowed the woman to recover her vestibular sense, helped "to reinforce the signals from her healthy tissues. He [Bach-y-Rita] thinks the machine also helps recruit other pathways." I thought this was interesting because the hat was such a simple device- it used electrodes on the tongue which told the woman which way she was leaning- and yet it had such dramatic effects on her brain.  The second quote that stood out to me was that localizationism "went from being as series of intriguing correlations (observations that damage to specific brain areas led to loss of specific mental functions) to a general theory that declared that every brain function had only one hardwired location." This was interesting because science is supposed to be open-minded and accepting of change, but this theory completely shut out the idea of neiroplasticity, even though the observations it was based on did not disprove the idea. I was also intrigued by an experiment in which a scientist rewired the optic nerves of ferrets to go to the auditory cortex. He found that the auditory cortex reorganized itself to process sight, and "though the ferrets that had this surgery did not have 20/20 vision, they had about a third of that, or 20/60- no worse than some people who wear eyeglasses." This implied that while a reorganized structure of the brain works, it doesn't work quite as well as the original structure, which would mean that although neuroplasticity clearly exists, the typical locations of specific functions are still important.