2. Figure 28.0_1
Chapter 28: Big Ideas
Nervous System
Structure and Function
The Human BrainAn Overview of Animal
The Eye
Nerve Signals and
Their Transmission
8. Figure 28.2_2
Node of Ranvier
Layers of
myelin
Nucleus
Schwann
cell
• Myelin sheaths
• enclose axons,
• form a cellular insulation, and speed up signal transmission.
16. Figure 28.6
Axon of
sending
cell
Synaptic
terminal
of sending
cell
Dendrite
of receiving
cell
Sending cell
Synaptic
vesicles
Synaptic
terminal
Synaptic
cleft
Vesicle fuses
with plasma
membrane
Action
potential
arrives
Neurotransmitter
is released into
synaptic cleft
Neurotransmitter
binds to receptor
Neurotransmitter
molecules
Neurotransmitter broken
down and released
Ion channel closes
Ions
Receptor
Receiving
cell
Neurotransmitter
Ion channels
Ion channel opens5 6
4
3
2
1
Animation
24. Figure 28.12A
Peripheral nervous system
(to and from the central
nervous system)
Motor system
(voluntary and
involuntary; to and from
skeletal muscles)
Autonomic nervous system
(involuntary; smooth and
cardiac muscles, various glands)
Parasympathetic
division
(“Rest and digest”)
Sympathetic
division
(“Flight and fight”)
Enteric division
(muscles and glands
of the digestive system)
31. Figure 28.15
Frontal lobe Parietal lobe
Occipital lobeTemporal lobe
Frontal
association
area
Speech
Smell
Speech
Motorcortex
Hearing
Reading
Vision
Visual
association
area
Somatosensory
association
area
Auditory
association
area
Somatosensorycortex
32. Regions of the Brain
Hypothalamus
– Under the thalamus
– Important autonomic nervous system center
– Helps regulate body temperature
– Controls water balance
– Regulates metabolism
– Houses the limbic center for emotions
– Thirst, appetite, pain, pleasure, etc.
33. Regions of the Brain
Medulla oblongata
– The lowest part of the brain stem
– Merges into the spinal cord
– Includes important fiber tracts
– Contains important control centers
– Heart rate control
– Blood pressure regulation
– Breathing
– Swallowing
– Vomiting
34. Regions of the Brain
Cerebellum
– Two hemispheres with convoluted surfaces
– Provides involuntary coordination of body
movements, balance and equilibrium.
39. The Eye and Vision
70 percent of all sensory receptors are in
the eyes
Each eye has over a million nerve fibers
Protection for the eye
– Most of the eye is enclosed in a bony orbit
– A cushion of fat surrounds most of the eye
49. Structure of the Eye: Sensory Layer
Signals leave the retina toward the brain through the
optic nerve
Optic disc (blind spot) is where the optic nerve
leaves the eyeball
– Cannot see images focused on the optic disc
Notas del editor
Figure 28.0_1 Chapter 28: Big Ideas
Student Misconceptions and Concerns
1. As students absorb additional details, often they lose sight of the fundamental functions of the nervous system, creating the risk that they will miss the forest for the trees. Remember to regularly connect the three fundamental functions of the nervous system, (a) sensory input, (b) integration, and (c) motor output, to an image of the PNS and CNS, noting where these functions occur (as in Figure 28.1A, for example). Returning to this or another familiar figure throughout lectures on the nervous system can help to remind students of key functions while allowing them to visually organize additional information. Such figures serve as “intellectual anchors” for a discussion.
2. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion.
Teaching Tips
1. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus?
2. Challenge your students to provide examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that detect signals indicating engine performance, interpret the signals, and then send signals to make adjustments.
Student Misconceptions and Concerns
1. As students absorb additional details, often they lose sight of the fundamental functions of the nervous system, creating the risk that they will miss the forest for the trees. Remember to regularly connect the three fundamental functions of the nervous system, (a) sensory input, (b) integration, and (c) motor output, to an image of the PNS and CNS, noting where these functions occur (as in Figure 28.1A, for example). Returning to this or another familiar figure throughout lectures on the nervous system can help to remind students of key functions while allowing them to visually organize additional information. Such figures serve as “intellectual anchors” for a discussion.
2. Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion.
Teaching Tips
1. Challenge students to explain the adaptive advantages of reflexes. What is the benefit of an “automatic” response to a stimulus?
2. Challenge your students to provide examples of computer systems that have the same three functions as the nervous system. For example, many automobiles use built-in computers that detect signals indicating engine performance, interpret the signals, and then send signals to make adjustments.
Figure 28.1B The knee-jerk reflex
Student Misconceptions and Concerns
Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion.
Teaching Tips
1. The proportion of neurons to glial cells in the brain is often quite surprising to students who might have little appreciation for the roles or even the existence of glial cells. Like the president of the United States or the head of any major organization, neurons have a large “support staff” of cells that help them perform their function.
2. Myelination is like the insulation on an electrical cord that ensures the wires are only exposed in specific locations. Breaks in this insulation, like disruption of myelin sheaths, will reduce the effectiveness of signal conduction.
3. Myelin sheaths and the nodes of Ranvier may also be described using the following analogy: Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. If you really want to make the point, you could find a fake hot dog item and bring along three hot dog buns.
Student Misconceptions and Concerns
Students often confuse the terms spinal column, spinal cord, spine, and backbone. They may fail to distinguish between the series of bones (vertebrae) and the extension of the central nervous system (the spinal cord) that runs through them. Figure 28.12B can help to clarify any confusion.
Teaching Tips
1. The proportion of neurons to glial cells in the brain is often quite surprising to students who might have little appreciation for the roles or even the existence of glial cells. Like the president of the United States or the head of any major organization, neurons have a large “support staff” of cells that help them perform their function.
2. Myelination is like the insulation on an electrical cord that ensures the wires are only exposed in specific locations. Breaks in this insulation, like disruption of myelin sheaths, will reduce the effectiveness of signal conduction.
3. Myelin sheaths and the nodes of Ranvier may also be described using the following analogy: Imagine that you are preparing a long hot dog (axon), maybe one 20 inches long. However, your hot dog buns (myelin) are only 6 inches long. You use three buns spaced 1 inch apart. That leaves two gaps (nodes of Ranvier), 1 inch each, separating the buns. If you really want to make the point, you could find a fake hot dog item and bring along three hot dog buns.
Figure 28.2_2 Structure of a myelinated motor neuron (part 2)
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
Students may require a review of the basic concept of potential energy. A simple demonstration in class, such as holding an object and then letting it plummet to the floor, can provide a quick, clear demonstration. As noted in the text, potential electrical energy can be stored in a battery.
Figure 28.3 How the resting potential is generated
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
1. Students might benefit most by first learning how sodium and potassium ions move during an action potential before addressing the resulting changes in membrane potential.
2. Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off.
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
1. Students might benefit most by first learning how sodium and potassium ions move during an action potential before addressing the resulting changes in membrane potential.
2. Students may better comprehend the idea of the threshold for an action potential by considering an analogy to the various annoying stimuli in our lives. A blaring TV might be annoying, but one tolerates it for a while. However, a person can reach a “threshold” where he or she is stimulated enough to get up and turn it off.
Figure 28.5_s3 Propagation of the action potential along an axon (detail, step 3)
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, then driving away on a road on the other side. The movement of the traveler (or the signal) continues, but changes mechanisms along the way.
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
The transmission of a signal across a chemical synapse is like driving along a road to a river, then taking a ferry across the river, then driving away on a road on the other side. The movement of the traveler (or the signal) continues, but changes mechanisms along the way.
Figure 28.6 Neuron communication at a typical chemical synapse
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
1. The authors compare a neuron’s diverse contacts with other neurons (potentially, hundreds of them) to a living circuit board.
2. Another analogy to the diverse signal input to a neuron might be helpful, even amusing. A neuron receiving diverse and potentially opposing signals is like a sports team hearing the crowd cheering for and against them. Game shows often demonstrate similar situations, as players’ decisions are influenced by the shouted suggestions of the audience.
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
1. Students may have heard about chemical imbalances in the brain without specifically knowing what this means. Abnormal concentrations of neurotransmitters in the central nervous system resulting from disease or chemical exposure can change our ability to perceive and respond to our world. Many drugs, both legal and illegal, can create imbalances with potentially disastrous consequences.
2. The treatment of psychological disorders is complicated by the diversity of neurotransmitters and their interactions. Therefore, predicting how a specific prescription drug will function in a particular patient is often difficult. Students may begin with the assumption that scientists currently understand much more about these complex reactions than we actually do. Emphasizing the need for additional research in these fields may encourage students to ponder career directions they have not previously considered.
3. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why. The likely response will be that one might not trust a criminal pharmacist to carefully provide medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street?
Student Misconceptions and Concerns
1. The abstract and complex nature of action potentials requires a careful and gradual discussion. Students with minimal backgrounds in cell biology are likely to struggle with this concept. Consider an initial presentation that provides an overview of the movement of charges before addressing the specific details.
2. Students who lack a background in chemistry and electricity are likely to struggle with the basic process of action potentials. Assumptions about the limited permeability of membranes, charges on ions, and natural electrical attractions may be unfamiliar to them. Students who read carefully through the text before action potentials are discussed in class are much more likely to understand the related lecture(s).
3. Consider presenting the diverse actions of neurotransmitters and related drugs in a table for quick and easy reference during lecture. Many students will have an interest in a particular drug, but soon forget the related effect if it was discussed earlier. A table permits easy reference to check drug effects.
Teaching Tips
1. Students may have heard about chemical imbalances in the brain without specifically knowing what this means. Abnormal concentrations of neurotransmitters in the central nervous system resulting from disease or chemical exposure can change our ability to perceive and respond to our world. Many drugs, both legal and illegal, can create imbalances with potentially disastrous consequences.
2. The treatment of psychological disorders is complicated by the diversity of neurotransmitters and their interactions. Therefore, predicting how a specific prescription drug will function in a particular patient is often difficult. Students may begin with the assumption that scientists currently understand much more about these complex reactions than we actually do. Emphasizing the need for additional research in these fields may encourage students to ponder career directions they have not previously considered.
3. Here is a bit of logic you might share with your students. Ask your students if they would avoid purchasing prescription drugs from a pharmacist convicted of some crime. If the answer is yes, ask why. The likely response will be that one might not trust a criminal pharmacist to carefully provide medicine. Why, then, you might wonder aloud, would anyone trust the quality of illegal drugs obtained from criminals (who are not likely trained pharmacists) who sell them on the street?
Student Misconceptions and Concerns
Students may think of the human brain as completely unique. Yet, the anatomical components of the human brain mirror the basic components found in many other vertebrates. These similarities are so extensive that sheep brains are often studied in biology laboratories to better understand human anatomy.
Teaching Tips
Students often are surprised to learn that their brain is hollow, although some students may know that the central nervous system is surrounded by cerebrospinal fluid. The basic development of the brain and spinal cord from an embryonic tube is addressed in Module 28.13.
Figure 28.11A A vertebrate nervous system (back view)
Figure 28.11B Fluid-filled spaces of the vertebrate CNS
Student Misconceptions and Concerns
Students often think of the motor nervous system as “voluntary” and directed by conscious thoughts. You might point out to your students that they are not likely concentrating on contracting the various muscles needed to maintain their posture as they sit in class. As noted in Module 28.12, many skeletal muscles are actually controlled by reflexes.
Teaching Tips
1. Students often remember the functions of the autonomic nervous system better by thinking of them as “automatic.”
2. Students may remember the functions of the sympathetic division as “sympathetic” to our problems. For example, the sympathetic nervous system may react to stressful situations by preparing us to fight or to run (although we often choose to do neither).
3. The automatic functions of the enteric division may not be appreciated by your students. You might note that given our busy days, with so many activities and obligations, we are fortunate that our digestive system can secrete, mix, propel, and absorb our meals without our focused mental attention! Can you imagine adding all that to our to-do list?
4. Many of the sympathetic division responses are the products of hormones released into the bloodstream. These responses cannot be quickly reversed. You might want to encourage students to think of how long it usually takes for them or others to calm down after having become extremely nervous or upset. Time and separation from the source of stress are usually required. For example, those who take a long walk in order to calm down often find, in the mild exercise and the retreat from the situation, an emotional comfort that also makes biological sense.
Figure 28.12A Functional divisions of the vertebrate PNS
Student Misconceptions and Concerns
Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
Teaching Tips
Tables such as Table 28.14, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams!
Figure 28.14A The main parts of the human brain
Student Misconceptions and Concerns
Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
Teaching Tips
Tables such as Table 28.14, which provide summaries of structures and functions, can relieve lectures from the repetition of tedious detail. Instead, more class time can be spent on more interesting and meaningful aspects of the topic. Such tables also facilitate the creation of matching questions on exams!
Student Misconceptions and Concerns
1. Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
2. Popular media often suggests that lateralization is a fixed human trait; i.e., certain people are “left-brained” while others are “right-brained.” Students might therefore believe that they are one or the other. As biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree, and studies of surgical procedures, disease, and injury have revealed that the brain’s hemispheres have considerable plasticity.
Teaching Tips
As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror!
Student Misconceptions and Concerns
1. Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
2. Popular media often suggests that lateralization is a fixed human trait; i.e., certain people are “left-brained” while others are “right-brained.” Students might therefore believe that they are one or the other. As biology frequently reveals, little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree, and studies of surgical procedures, disease, and injury have revealed that the brain’s hemispheres have considerable plasticity.
Teaching Tips
As students learn about the structure and function of the cerebral cortex, they are actually using these sets of cells to think about these cells. As student understanding grows, these sets of cells become increasingly aware of their own properties, in a process that is like looking in a mirror!
Figure 28.15 Functional areas of the left cerebral hemisphere
Student Misconceptions and Concerns
Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
Teaching Tips
1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website www.census.gov/main/www/popclock.html.
2. The frequent occurrence of the neurological disorders discussed in Module 28.20 makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class.
3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure.
Student Misconceptions and Concerns
Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
Teaching Tips
1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website www.census.gov/main/www/popclock.html.
2. The frequent occurrence of the neurological disorders discussed in Module 28.20 makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class.
3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure.
Figure 28.20A PET scans showing brain activity in a depressed person (top) and healthy person (bottom)
Red and yellow areas are low brain activity
Figure 28.20C Actor Michael J. Fox (right) and boxer Muhammad Ali, both of whom suffer from Parkinson’s disease, testifying before the United States Senate about funding for the disorder
Student Misconceptions and Concerns
Students often think of vertebrate skulls as just a place to house the brain. In most vertebrates, the brain is a relatively small item housed deep in the skull. The skull also houses all the major sense organs, is the site of firm muscle attachments, and is the entry point for the respiratory and digestive systems.
Teaching Tips
1. The text notes that nearly 20 million American adults are affected by depression. However, many students may be unaware what proportion of the population this number represents. Does 20 million represent a large or small fraction of the people in our country? Consider surveying your class to see how many have an idea of the size of the U.S. population and what fraction of people therefore suffer from depression. The current U.S. population, about 311–312 million in mid-2011, is estimated at the website www.census.gov/main/www/popclock.html.
2. The frequent occurrence of the neurological disorders discussed in Module 28.20 makes it likely that many of your students will know someone who is affected by such a disorder or may even be coping with one themselves. Topics such as these, which often have immediate relevance to students’ lives and tend to arouse both sympathy and curiosity, create excellent opportunities for class discussions and further exploration outside of class.
3. Students may wonder why diseases of old age (such as Alzheimer’s, cancer, and cardiovascular disease) have not been selected against by natural selection. Consider challenging your class to explain why diseases of old age may not be subject to strong selective pressures. Many students will not realize that diseases that strike primarily after the most common age of reproduction experience reduced selective pressure.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. Optical illusions can reveal the mental gymnastics our mind performs to make sense of our visual world. Consider searching for “optical illusions” on the Internet to identify some examples to share with your class.
2. Cataracts, a clouding of the lens of the eye, are a common vision problem. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce exposure to UV light.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. Optical illusions can reveal the mental gymnastics our mind performs to make sense of our visual world. Consider searching for “optical illusions” on the Internet to identify some examples to share with your class.
2. Cataracts, a clouding of the lens of the eye, are a common vision problem. Extensive exposure to ultraviolet (UV) light is one known cause of cataracts. Using eyeglasses and/or sunglasses with 100% UV coating can reduce exposure to UV light.
Figure 29.7C The single-lens eye of a vertebrate
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. Bits of cellular debris often drift within the vitreous humor, temporarily showing up in our field of view. These bits are commonly called “floaters.”
2. Some students might be familiar with the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball and squeezing a tennis ball are examples of other tests of internal pressure.
3. The ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading might find it difficult to focus closely, especially at the end of a long day. Staring off into the distance is relaxing in part because the ciliary muscles can relax.
4. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. Bits of cellular debris often drift within the vitreous humor, temporarily showing up in our field of view. These bits are commonly called “floaters.”
2. Some students might be familiar with the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball and squeezing a tennis ball are examples of other tests of internal pressure.
3. The ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading might find it difficult to focus closely, especially at the end of a long day. Staring off into the distance is relaxing in part because the ciliary muscles can relax.
4. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. Bits of cellular debris often drift within the vitreous humor, temporarily showing up in our field of view. These bits are commonly called “floaters.”
2. Some students might be familiar with the test for glaucoma in which a puff of air is shot at the eye. This blast of air distorts the eyeball and provides a measurement of the internal pressure. Dribbling a basketball and squeezing a tennis ball are examples of other tests of internal pressure.
3. The ciliary muscles of the eye can become fatigued if one focuses closely for long periods. Students who spend hours reading might find it difficult to focus closely, especially at the end of a long day. Staring off into the distance is relaxing in part because the ciliary muscles can relax.
4. The lacrimal canal connects the inner corner of the eye to the sinus cavity. Our noses might run when we cry because some surplus tears drain into our nose.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
Challenge students to explain why an image appears clearer as we move closer to it. In general, it has to do with the number of rods and cones in the retina that are used to form the image. When we see an object at a distance, perhaps using only 10% of our field of vision, we use a proportional amount of rods and cones to form the image (about 10%). When we move closer, the image forms a larger percentage of our field of view and a proportionally higher number of rods and cones paint the picture. Like the images displayed on computer monitors or printed in newspapers, this image is formed by a series of dots: the more dots used to form the picture, the clearer the image.
Student Misconceptions and Concerns
Many common visual phenomena may have been noticed but not understood by students. Students have experienced or know about floating specks in the visual field, difficulty focusing on text late at night, and colorblindness. However, few students have the ability to accurately explain these and many other phenomena related to vision. These familiar subjects of curiosity can be used in your class to encourage reflective critical thought using the information provided in Modules 29.7–29.10. Insight into their explanations and other questions can be found in the Teaching Tips directly below.
Teaching Tips
1. The inheritance patterns of colorblindness are discussed in Module 9.22.
2. A dark pigment layer behind the rods and cones absorbs light that has passed through these photoreceptor cells. This prevents reflected light from interfering with the detection of new light. Albino vertebrate pupils appear red because the light transmitted through the retina is not absorbed by a pigment layer and instead reflects off red blood cells in the choroid layer of the eye.
Figure 29.10B The vision pathway from light source to optic nerve