Name: NERVOUS SYSTEM NOTES

VOCABULARY

1. Action potential2. Auditory nerve3. Axon 4. Brainstem5. Cell Body6. Central Nervous System

(CNS)7. Cerebrum8. Cochlea9. Cones10. Dendrite11. Electromagnetic spectrum12. Frontal lobe13. Hypothalamus14. Interneuron15. Involuntary impulse

16. Iris17. Lens18. Medulla oblongata19. Motor neuron20. Myelin sheath21. Nerve22. Neuron23. Neurotransmitter24. Occipital lobe25. Olfactory nerve26. Optic nerve27. Parietal lobe28. Peripheral Nervous System

(PNS)29. Pons30. Primary physiological colors

31. Pupil32. Reflex Arc33. Retina34. Rods35. Secondary physiological

colors36. Semicircular canal37. Sensory neuron38. Spinal cord39. Taste buds40. Temporal lobe41. Visible spectrum42. Voluntary impulse

1. Using the word bank below, label the parts of a neuron. Describe the function of each part.

NEURON:

NERVE:

Parts of a Neuron Function

Axon

Cell Body

Dendrite

Myelin Sheath

Synapse

2. Define the three types of neurons involved in a reflex arc.

Types of Neurons Function

Sensory Neuron

Interneuron

Motor neuron

3. Explain why a simple reflex arc is unique and is completed by the body.

4. Explain how a nerve impulse is similar to an electrical signal, and how it moves from one neuron to the next.

5. Describe the function of a neurotransmitter.

6. Know the specific function of the following neurotransmitter examples:

Neurotransmitter Function

Acetylcholine

Dopamine

Serotonin

Endorphin

Epinephrine

Melatonin

7. Locate and describe the three main parts of the brain.

8. Color and describe the function of the specific parts of the brain. (Click on the 3D Brain Link in the upper right hand corner: http://www.g2conline.org/ )

1 st image: Cerebrum = greyBrain Stem = bluePons = blueCerebellum = purpleHypothalamus = greenSpinal cord = yellow Medulla = blue

2 nd image: Frontal lobe = redParietal lobe = light blueOccipital lobe = orangeTemporal lobe = yellowCerebellum = purplePons = dark blueMedulla = dark blue

Brain Part Function(s) Associated Cognitive Disorders

Cerebrum

Frontal lobe (part of

cerebrum)

Parietal lobe (part of

cerebrum)

Occipital lobe (part of

cerebrum)

Temporal lobe (part of

cerebrum)

Pons (part of brain stem)

Medulla oblongata

(part of brain stem)

Hypothalamus

Cerebellum

Spinal Cord

9. Compare the functions of the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

10. How does our body enable us to TASTE and SMELL?

Sensory nerves associated with taste and smell are located in the mouth and nasal cavity. Once a stimulus is detected an impulse is sent to the brain.

Signals from these nerves work together to create a combined effect in the brain.

Olfactory Nerve: transmits information from sensory receptors in the mouth and nasal cavity to the brain. The brain will enable the body to determine a sense of smell.

Olfactory sensations also contribute to long-lasting memories and emotion.

Taste buds : detect combinations of chemicals that we identify as sweet, sour, salty, bitter and umami.

Umami : represents the taste of the amino acid called glutamate.  It can be described as a pleasant "brothy" or "meaty" taste with a long lasting, mouthwatering and coating sensation over the tongue. 

All other taste sensations, such as coffee, cinnamon, garlic and pepper, are combinations of the primary tastes.

11. How does our body enable use to HEAR?

Sound waves enter the auditory canal and cause the eardrum to vibrate. The sound waves continue to the cochlea.

Cochlea: A spiral-shaped cavity of the inner ear that resembles a snail shell and contains nerve endings essential for hearing.

12. How does our body enable us to sense BALANCE?

Auditory nerve : transmits information from the inner ear to the brain. The brain will enable the body to determine a sense of sound and balance.

Semicircular canals: three looped fluid-filled tubes, at right angles to one another found in the inner ear. They help determine the sense of orientation and equilibrium (balance).

13. How does our body enable us to us to sense TOUCH?

The skin has many types of sensory receptors:

1. Touch

2. Heat

3. Cold

4. Pressure

5. Pain

Some sensory receptors become less sensitive and trigger fewer signals to the brain.

14. How does our body enable us to sense VISION?

PROCESS:

1. Light travels through the pupil to the lens. The iris tissue will change the pupil’s size to allow more or less light in.

2. The lens inverts the image and focuses it on the retina.

3. Rods and cones in the retina provide light-sensitivity and information about color.

4. The rods and cones are connected to the optic nerve and help send light & color sensory information to the brain.

VOCABULARY:

Pupil: The dark circle in the center of the eye. It’s a hole that lets light into the inner part of the eye.

Iris: A muscle that controls how much light can enter the eye.

Lens : Clear flexible part of the eye that inverts an image and focuses it on the retina.

Retina : innermost layer of the eye that contains rods and cones

Optic Nerve : transmits information from rods and cones to the brain. The brain will enable the body to determine the sense of vision.

15. How does the human eye perceive light and color?

Rods and Cones are photoreceptors, they signal the presence of light.

Rods : determine light intensity (dark vs light) and are good motion detector.

Cones : Distinguish color by wavelength of light and intensity. Humans have three types:

Red cone: long wavelength

Green cone: medium wavelength

Blue cone: short wavelength

Read the following paragraphs and answer the questions that follow:

Electromagnetic radiation can be thought of as consisting of waves, and therefore every kind of EM radiation has an associated wavelength, the physical distance between two successive peaks in that wave. The full EM spectrum is shown below.

Human vision, however, is limited to what we call visible light, or EM radiation found within the visible spectrum, and that is the focus of the lesson. The “ROYGBIV” (red-orange-yellow-green-blue-indigo-violet) mnemonic can be useful in memorizing the order, by wavelength, of the colors that comprise the spectrum. Colors at the violet end of the visible spectrum have shorter wavelengths (and higher energy), while the red end of the spectrum has longer wavelengths (and lower energy). Immediately past the red end of the visible spectrum is the infrared region, which is beyond human perception but is often associated with heat. Immediately beyond the purple end of the visible spectrum is the ultraviolet region, also beyond human perception but readily apparent to anyone who has ever had a sunburn! The color system invoked to explain human visual perception is referred to as the RGB (“red-green-blue”) model or the additive color model.

It is the same model that is used to generate colors on computer screens and other electronic displays. Because of how the human retina operates, blue, green and red can be thought of as “primary physiological colors,” as shown below in the additive color wheel. When we perceive the color red, for example, it is because red light, whether emitted from a light bulb or reflected from an object, is exclusively activating our “red” cones, whereas green and blue result from the exclusive activation of our “green” and “blue” cones, respectively. By contrast, yellow, cyan and magenta can be thought

of as “secondary physiological colors”; each results from the simultaneous and equal activation of two types of cone cells. For example, a yellow chair appears yellow under full-spectrum (white) lighting because both red and green wavelengths of light are being reflected from the chair into the eye, activating the “red” and “green” cone cells equally and simultaneously; reference the additive color wheel to reinforce this. If all three cone varieties are activated equally and simultaneously, the resulting perception is white (also shown on the color wheel).

The Additive (RGB) Color Wheel

The “complementary physiological color pairs” are blue & yellow, red & cyan, and green & magenta (colors across from each other on the additive color wheel). An object of color X best absorbs light at the wavelength of its complementary color. For example, a yellow chair best absorbs light in the blue range of the spectrum. When two or three of the different cone varieties are activated unequally, you perceive non-primary or non-secondary physiological colors, such as orange, brown or purple.

16. What is the difference between the electromagnetic spectrum (EM) and visible spectrum?

17. What the human primary physiological colors?

18. What are the human secondary physiological colors?

19. Read and highlight answers to the following questions. How did human color vision evolve? What are the advantages and disadvantages of this development?

A lot of you have experienced “love at first sight” or you definitely know someone who has. Falling in love is a very strong feeling; but why does sight of a certain person alone provoke such a strong

feeling? In order to find the suitable mate, our distant ancestors once relied on smell and pheromones (tasteless and odorless chemical substances that activate a behavioral response from the opposite sex of the same species). Later, they developed the ability to see color, which caused them to be less sensitive to smell and pheromones. Today, most of the information necessary for mate-finding is perceived visually. Therefore, this suggests a close relationship between the evolution of color vision and the criteria for selecting suitable mates.

Chance triggered the evolution of color vision

Humans and animals see the world differently; some birds, rodents and certain types of fish can see ultraviolet light, some snakes can see infrared light waves. On the other hand, humans can’t see either of these lights. To give an example, dogs can see fewer colors than humans; however, they compensate for their weakness of color vision with a

sense of smell which is said to be 10,000 times more powerful than humans’. The world of dogs is ruled by scent, while the world of humans is ruled by the ability to see.

From four to three

Color vision evolved as a result of chance and environments. Recent advances in the study of genes forming cone cells and rod cells of the eye have led to the discovery of new facts about genes, especially those related to the recognition of different colors. Looking back at the process of biological evolution down to humans; the common ancestors of birds, reptiles and fish were tetrachromat (they could see four color spectrums: UV, blue, green, and red types). All mammals had the same ancestors. During Mesozoic era, when mammals had to live

with dinosaurs, in order to survive; mammals became nocturnal and the ability to see four different colors became less crucial for survival. As a result, they lost the genes responsible for green and blue color recognition, which resulted in dichromacy, i.e. the two-color vision system (UV and red types).

When the dinosaurs went extinct about 65 million years ago, the nocturnal ancestors of mammals returned to daylight activity. Some 30 million years later, the genes that these animals possessed for seeing red and blue duplicated and then mutated, which gave rise to the green-type gene capable of perceiving green light. Eventually, the three-color vision system (trichromat) developed. Mammals gained dominance in the jungle since they had the ability to make fine distinctions in color. It was then that our ancestors gained the ability to see color as we enjoy it today.

With the ability to distinguish more colors, our ancestors became less sensitive to smells and pheromones.

Evolution is Devolution

Devolution refers to retrograde evolution. Many researchers have proposed that evolution is closely tied to devolution, and this becomes obvious from various observations in the evolution of humans as well as other animals. An example of devolution comes from the ability to smell in humans. The maximum number of genes for color perception that humans possess is only four, as opposed to 802 that control sense of smell in humans and 1391 in mice. However, humans use only 388, or less than half, of the total genes available. In other words, humans have evolved by devolving, or ceasing to use many of these genes through mutation.

In summary, we can assume that humans and other primates gained the ability to see color at the expense of losing the sensitivity to smell and the ability to detect pheromones (tasteless and odorless chemical substances that activate a behavioral response from the opposite sex of the same species). As a result, for humans, color vision has become the primary sense that we depend on for all aspects of our lives, from love to survival.