© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko
PowerPoint Lectures for
Campbell Biology: Concepts & Connectio...
Figure 28.0_1
Chapter 28: Big Ideas
Nervous System
Structure and Function
The Human BrainAn Overview of Animal
The Eye
Ner...
28.1 Nervous systems receive sensory input,
interpret it, and send out appropriate
commands
 The nervous system
– obtains...
 Sensory neurons
– convey signals from sensory receptors
– to the CNS.
 Interneurons
– are located entirely in the CNS,
...
Figure 28.1B
Sensory
receptor
2
1
3
4
Sensory
neuron
Brain
Spinal
cord
Interneuron
CNSPNS
Nerve
Flexor
muscles
Quadriceps
...
28.2 Neurons are the functional units of nervous
systems
 Neurons are
– cells specialized for carrying signals
– the func...
28.2 Neurons are the functional units of nervous
systems
© 2012 Pearson Education, Inc.
Figure 28.2_2
Node of Ranvier
Layers of
myelin
Nucleus
Schwann
cell
• Myelin sheaths
• enclose axons,
• form a cellular in...
28.3 Nerve function depends on charge differences
across neuron membranes
 At rest, a neuron’s plasma membrane has potent...
Figure 28.3
Neuron Axon
Plasma
membrane
Plasma
membrane
Na+
channel
Outside of neuron
K+
channel
Inside of neuron
Na+
Na+
...
28.4 A nerve signal begins as a change in the
membrane potential
 A stimulus is any factor that causes a nerve signal
to ...
 A nerve signal, called an action potential, is
– a change in the membrane voltage, from the resting
potential, to a maxi...
Figure 28.5_s3
Na+
1
Na+
Na+
Na+
K+
K+
Action potential
2
Plasma
membrane
Axon
segment
Action
potential
Action potential
N...
28.6 Neurons communicate at synapses
 Synapses are junctions where signals are
transmitted between
– two neurons or
– bet...
 Electrical signals pass between cells at electrical
synapses.
 At chemical synapses
– the ending cell secretes a chemic...
Figure 28.6
Axon of
sending
cell
Synaptic
terminal
of sending
cell
Dendrite
of receiving
cell
Sending cell
Synaptic
vesicl...
28.7 Chemical synapses enable complex
information to be processed
 Neurotransmitters
– can excite a receiving cell
– can ...
28.8 A variety of small molecules function as
neurotransmitters
 Neurotransmitters:
– Acetylcholine is a neurotransmitter...
28.9 CONNECTION: Many drugs act at chemical
synapses
Many psychoactive drugs
act at synapses
affect neurotransmitter act...
 In the vertebrates, the central nervous system (CNS)
– consists of the brain and spinal cord and
– includes spaces fille...
Figure 28.11A
Central
nervous
system
(CNS)
Peripheral
nervous
system
(PNS)
Spinal
cord
Cranial
nerves
Ganglia
outside
CNS
...
Figure 28.11B
Brain Cerebrospinal fluid
Meninges
Gray matter
White
matter
Dorsal root
ganglion
(part of PNS)
Spinal nerve
...
 The motor nervous system
– carries signals to and from skeletal muscles and
– mainly responds to external stimuli.
 The...
Figure 28.12A
Peripheral nervous system
(to and from the central
nervous system)
Motor system
(voluntary and
involuntary; ...
28.14 The structure of a living supercomputer:
The human brain
 The human brain is
– more powerful than the most sophisti...
Figure 28.14A
Cerebral cortex
(outer region
of cerebrum)
Cerebrum
Thalamus
Hypothalamus
Pituitary gland
Midbrain
Forebrain...
Figure 7.16a
Third ventricle
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla o...
 The cerebrum is
– part of the forebrain and
– the largest and most complex part of the brain.
– Most of the cerebrum’s i...
28.15 The cerebral cortex is a mosaic of
specialized, interactive regions
 The cerebral cortex
– accounts for 80% of the ...
 Association areas
– make up most of the cerebrum and
– are concerned with higher mental activities such as
reasoning and...
Figure 28.15
Frontal lobe Parietal lobe
Occipital lobeTemporal lobe
Frontal
association
area
Speech
Smell
Speech
Motorcort...
Regions of the Brain
 Hypothalamus
– Under the thalamus
– Important autonomic nervous system center
– Helps regulate body...
Regions of the Brain
 Medulla oblongata
– The lowest part of the brain stem
– Merges into the spinal cord
– Includes impo...
Regions of the Brain
 Cerebellum
– Two hemispheres with convoluted surfaces
– Provides involuntary coordination of body
m...
28.20 CONNECTION: Changes in brain
physiology can produce neurological
disorders
 Many neurological disorders can be link...
28.20 CONNECTION: Changes in brain
physiology can produce neurological
disorders
 Schizophrenia
– a severe mental disturb...
Figure 28.20A
Depressed brain
Normal brain
 Alzheimer’s disease
– characterized by confusion, memory loss, and personality changes
 Parkinson’s disease
– a motor d...
The Eye and Vision
 70 percent of all sensory receptors are in
the eyes
 Each eye has over a million nerve fibers
 Prot...
29.7 EVOLUTION CONNECTION: Several types
of eyes have evolved independently among
animals
 The ability to detect light pl...
29.7 EVOLUTION CONNECTION: Several types
of eyes have evolved independently among
animals
– In single-lens eyes
– light en...
Figure 29.7C
Sclera
Ciliary body
Ligament
Cornea
Iris
Pupil
Aqueous
humor
Lens
Vitreous
humor
Blind spot
Artery
and vein
O...
29.8 Humans have single-lens eyes that focus by
changing position or shape
 The outer surface of the human eyeball is a t...
29.8 Humans have single-lens eyes that focus by
changing position or shape
 The lens and ciliary body divide the eye into...
29.8 Humans have single-lens eyes that focus by
changing position or shape
 In mammals, the lens focuses by changing shap...
29.9 CONNECTION: Artificial lenses or surgery
can correct focusing problems
 Visual acuity is the ability of the eyes to ...
29.10 The human retina contains two types of
photoreceptors: rods and cones
 The human retina contains two types of
photo...
Figure 29.10B
Retina
Optic
nerve
Retina
Neurons Photoreceptors
Rod Cone
Optic
nerve
fibers
To the brain
Structure of the Eye: Sensory Layer
 Signals leave the retina toward the brain through the
optic nerve
 Optic disc (blin...
Upcoming SlideShare
Loading in …5
×

Ch28&29 notes Nervous system and the eye

1,770 views

Published on

Published in: Technology, Health & Medicine
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,770
On SlideShare
0
From Embeds
0
Number of Embeds
59
Actions
Shares
0
Downloads
30
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide
  • 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
  • Ch28&29 notes Nervous system and the eye

    1. 1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 28Chapter 28 Nervous Systems
    2. 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
    3. 3. 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands  The nervous system – obtains sensory information, sensory input, – processes sensory information, integration, and – sends commands to effector cells (muscles) that carry out appropriate responses, motor output. © 2012 Pearson Education, Inc.
    4. 4.  Sensory neurons – convey signals from sensory receptors – to the CNS.  Interneurons – are located entirely in the CNS, – integrate information, and – send it to motor neurons.  Motor neurons convey signals to effector cells. 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands © 2012 Pearson Education, Inc.
    5. 5. Figure 28.1B Sensory receptor 2 1 3 4 Sensory neuron Brain Spinal cord Interneuron CNSPNS Nerve Flexor muscles Quadriceps muscles Ganglion Motor neuron
    6. 6. 28.2 Neurons are the functional units of nervous systems  Neurons are – cells specialized for carrying signals – the functional units of the nervous system  A neuron consists of – cell body – extensions (fibers) that conduct signals, – Dendrites (toward the cell body) – Axons (away from the cell body) © 2012 Pearson Education, Inc.
    7. 7. 28.2 Neurons are the functional units of nervous systems © 2012 Pearson Education, Inc.
    8. 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.
    9. 9. 28.3 Nerve function depends on charge differences across neuron membranes  At rest, a neuron’s plasma membrane has potential energy—the membrane potential, in which – just inside the cell is slightly negative and – just outside the cell is slightly positive.  The resting potential is the voltage across the plasma membrane of a resting neuron. – The resting potential exists because of differences in ion concentration of the fluids inside and outside the neuron. © 2012 Pearson Education, Inc.
    10. 10. Figure 28.3 Neuron Axon Plasma membrane Plasma membrane Na+ channel Outside of neuron K+ channel Inside of neuron Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+K+ K+ K+K+K+ Na+ -K+ pump ATP K+
    11. 11. 28.4 A nerve signal begins as a change in the membrane potential  A stimulus is any factor that causes a nerve signal to be generated. A stimulus – alters the permeability of a portion of the membrane, which allows ions to pass through, – Which then changes the membrane’s voltage. © 2012 Pearson Education, Inc.
    12. 12.  A nerve signal, called an action potential, is – a change in the membrane voltage, from the resting potential, to a maximum level, and then back to the resting potential.  Action potentials are – self-propagated in a one-way chain reaction along a neuron – all-or-none events. 28.4 A nerve signal begins as a change in the membrane potential © 2012 Pearson Education, Inc. Animation: Action Potential
    13. 13. Figure 28.5_s3 Na+ 1 Na+ Na+ Na+ K+ K+ Action potential 2 Plasma membrane Axon segment Action potential Action potential Na+ K+ K+ 3 Na+ Animation
    14. 14. 28.6 Neurons communicate at synapses  Synapses are junctions where signals are transmitted between – two neurons or – between neurons and other cells. © 2012 Pearson Education, Inc.
    15. 15.  Electrical signals pass between cells at electrical synapses.  At chemical synapses – the ending cell secretes a chemical signal, a neurotransmitter, – the neurotransmitter crosses the synaptic cleft, and – the neurotransmitter binds to a specific receptor on the surface of the receiving (postsynaptic) cell. 28.6 Neurons communicate at synapses © 2012 Pearson Education, Inc. Animation: Synapse
    16. 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
    17. 17. 28.7 Chemical synapses enable complex information to be processed  Neurotransmitters – can excite a receiving cell – can inhibit a receiving cell’s activity – by decreasing its ability to develop action potentials. © 2012 Pearson Education, Inc.
    18. 18. 28.8 A variety of small molecules function as neurotransmitters  Neurotransmitters: – Acetylcholine is a neurotransmitter – in the brain – at synapses between motor neurons and muscle cells. – Biogenic amines – are important neurotransmitters in the CNS – include serotonin and dopamine, which affect sleep, mood, and attention. – Neuropeptides – consist of relatively short chains of amino acids important in the CNS – include endorphins, decreasing our perception of pain. © 2012 Pearson Education, Inc.
    19. 19. 28.9 CONNECTION: Many drugs act at chemical synapses Many psychoactive drugs act at synapses affect neurotransmitter action. – Caffeine counters the effect of inhibitory neurotransmitters. – Nicotine acts as a stimulant by binding to acetylcholine receptors. – Alcohol is a depressant by increasing inhibitory effects. – Antidepressants block the removal of serotonin, increasing the time this mood neurotransmitter is in the synapse. – Tranquilizers (Valium & Xanax) increase inhibitors in synapses. – Ritalin & Adderall block reuptake of dopamine and norepinephrine © 2012 Pearson Education, Inc.
    20. 20.  In the vertebrates, the central nervous system (CNS) – consists of the brain and spinal cord and – includes spaces filled with cerebrospinal fluid  The vertebrate peripheral nervous system (PNS) consists of – cranial nerves, – spinal nerves, and – ganglia. 28.11 Vertebrate nervous systems are highly centralized © 2012 Pearson Education, Inc.
    21. 21. Figure 28.11A Central nervous system (CNS) Peripheral nervous system (PNS) Spinal cord Cranial nerves Ganglia outside CNS Spinal nerves Brain
    22. 22. Figure 28.11B Brain Cerebrospinal fluid Meninges Gray matter White matter Dorsal root ganglion (part of PNS) Spinal nerve (part of PNS)Central canal Spinal cord (cross section) Ventricles Central canal of spinal cord Spinal cord
    23. 23.  The motor nervous system – carries signals to and from skeletal muscles and – mainly responds to external stimuli.  The autonomic nervous system – regulates the internal environment and – controls smooth and cardiac muscle and organs and glands of the digestive, cardiovascular, excretory, and endocrine systems. 28.12 The peripheral nervous system of vertebrates is a functional hierarchy © 2012 Pearson Education, Inc.
    24. 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)
    25. 25. 28.14 The structure of a living supercomputer: The human brain  The human brain is – more powerful than the most sophisticated computer and – composed of three main parts: 1. forebrain, 2. midbrain, and 3. hindbrain. © 2012 Pearson Education, Inc.
    26. 26. Figure 28.14A Cerebral cortex (outer region of cerebrum) Cerebrum Thalamus Hypothalamus Pituitary gland Midbrain Forebrain Hindbrain Pons Medulla oblongata Cerebellum Spinal cord
    27. 27. Figure 7.16a Third ventricle Anterior commissure Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord Cerebral hemisphere Corpus callosum Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Corpora quadrigemina Cerebral aqueduct Cerebral peduncle of midbrain Fourth ventricle Choroid plexus Cerebellum Midbrain (a)
    28. 28.  The cerebrum is – part of the forebrain and – the largest and most complex part of the brain. – Most of the cerebrum’s integrative power resides in the cerebral cortex of the two cerebral hemispheres. 28.14 The structure of a living supercomputer: The human brain © 2012 Pearson Education, Inc.
    29. 29. 28.15 The cerebral cortex is a mosaic of specialized, interactive regions  The cerebral cortex – accounts for 80% of the total human brain mass.  Specialized integrative regions of the cerebral cortex include – the motor cortex – the somatosensory cortex (touch, pain, pressure, and temperature) – centers for vision, hearing, taste, and smell. © 2012 Pearson Education, Inc.
    30. 30.  Association areas – make up most of the cerebrum and – are concerned with higher mental activities such as reasoning and language.  In a phenomenon known as lateralization, right and left cerebral hemispheres tend to specialize in different mental tasks. – Left – language, logic, math, and motor control – Right – spatial relations, patterns, nonverbal thinking 28.15 The cerebral cortex is a mosaic of specialized, interactive regions © 2012 Pearson Education, Inc.
    31. 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. 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. 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. 34. Regions of the Brain  Cerebellum – Two hemispheres with convoluted surfaces – Provides involuntary coordination of body movements, balance and equilibrium.
    35. 35. 28.20 CONNECTION: Changes in brain physiology can produce neurological disorders  Many neurological disorders can be linked to changes in brain physiology, including – schizophrenia, – major depression, – Alzheimer’s disease, and – Parkinson’s disease. © 2012 Pearson Education, Inc.
    36. 36. 28.20 CONNECTION: Changes in brain physiology can produce neurological disorders  Schizophrenia – a severe mental disturbance and – characterized by psychotic episodes in which patients lose the ability to distinguish reality.  Depression – Two broad forms of depressive illness have been identified: 1. major depression and 2. bipolar disorder, manic-depressive disorder. – Treatments may include selective serotonin reuptake inhibitors (SSRIs), which increase the amount of time serotonin is available to stimulate certain neurons in the brain. © 2012 Pearson Education, Inc.
    37. 37. Figure 28.20A Depressed brain Normal brain
    38. 38.  Alzheimer’s disease – characterized by confusion, memory loss, and personality changes  Parkinson’s disease – a motor disorder – characterized by – difficulty in initiating movements, – slowness of movement, and – rigidity. 28.20 CONNECTION: Changes in brain physiology can produce neurological disorders © 2012 Pearson Education, Inc.
    39. 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
    40. 40. 29.7 EVOLUTION CONNECTION: Several types of eyes have evolved independently among animals  The ability to detect light plays a central role in the lives of nearly all animals.  All animal light detectors are based on cells called photoreceptors that contain pigment molecules that absorb light. © 2012 Pearson Education, Inc.
    41. 41. 29.7 EVOLUTION CONNECTION: Several types of eyes have evolved independently among animals – In single-lens eyes – light enters the front center of the eye through a small opening, the pupil, – the amount of light that enters is controlled by the iris – light passes through a single disklike lens – light is focused onto the retina, which consists of many photoreceptor cells © 2012 Pearson Education, Inc.
    42. 42. Figure 29.7C Sclera Ciliary body Ligament Cornea Iris Pupil Aqueous humor Lens Vitreous humor Blind spot Artery and vein Optic nerve Fovea (center of visual field) Retina Choroid
    43. 43. 29.8 Humans have single-lens eyes that focus by changing position or shape  The outer surface of the human eyeball is a tough, whitish layer of connective tissue called the sclera. – At the front of the eye, the sclera becomes the transparent cornea – lets light into the eye – helps focus light © 2012 Pearson Education, Inc.
    44. 44. 29.8 Humans have single-lens eyes that focus by changing position or shape  The lens and ciliary body divide the eye into two fluid-filled chambers. 1. The large chamber behind the lens is filled with a jellylike vitreous humor. 2. The smaller chamber in front of the lens contains the thinner aqueous humor. – These humors – help maintain the shape of the eyeball and – circulate nutrients and oxygen to the lens, iris, and cornea. © 2012 Pearson Education, Inc.
    45. 45. 29.8 Humans have single-lens eyes that focus by changing position or shape  In mammals, the lens focuses by changing shape using muscles attached to the choroid and ligaments that suspend the lens. © 2012 Pearson Education, Inc.
    46. 46. 29.9 CONNECTION: Artificial lenses or surgery can correct focusing problems  Visual acuity is the ability of the eyes to distinguish fine detail. – Visual acuity is measured by reading standardized eye charts from a distance of 20 feet. – The ability to see normally at 20 feet is 20/20 vision. © 2012 Pearson Education, Inc.
    47. 47. 29.10 The human retina contains two types of photoreceptors: rods and cones  The human retina contains two types of photoreceptors. 1. Rods – contain the visual pigment rhodopsin, which can absorb dim light, and – can detect shades of gray in dim light. 2. Cones – contain the visual pigment photopsin, which absorbs bright colored light, and – allow us to see color in bright light. © 2012 Pearson Education, Inc.
    48. 48. Figure 29.10B Retina Optic nerve Retina Neurons Photoreceptors Rod Cone Optic nerve fibers To the brain
    49. 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

    ×