Download PART IV INTEGRATION AND COORDINATION IN HUMANS

PART IV
INTEGRATION AND COORDINATION IN HUMANS
13 Nervous System
14 Senses
15 Endocrine System
Chapter 13 - Nervous System
BEHAVIORAL OBJECTIVES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Name the two types of cells that comprise nervous tissue. [13.1, p.246]
Draw a neuron and label the three parts. [13.1, pp.246-247]
Describe the functions of the three major classes of neurons. [13.1, p.246]
Describe the differences in structure of the three major classes of neurons. [13.1, pp.246-247, Fig. 13.1-13.3]
Explain the importance of the myelin sheath. [13.1, p. 247, Fig. 13.3]
Describe the nerve impulse as an electrochemical change that can be recorded by an oscilloscope. [13.1,
p.248, Fig. 13.4]
Describe the structure and function of a synapse, including transmission across a synapse. [13.1, pp.248-251,
Figs. 13.5 & 13.6]
Describe the location and function of the central nervous system. [13.2, p.252, Fig. 13.7]
Describe the structure and function of the spinal cord. [13.2, p.252-253, Fig. 13.8]
Describe the general anatomy of the brain, name the major parts, and give a function of each. [13.2, pp.254257, Figs. 13.9, 13.11]
Name the lobes of the cerebrum, and give a function of each. [13.2, pp.255-256, Fig. 13.10]
Give the location and functions of the limbic system. [13.3, pp. 257-258, Fig. 13.12]
Describe the higher mental functions of learning, memory, and language. [13.3, pp.258-259, Figs. 13.13 &
13.14]
Describe the peripheral nervous system and define nerve. [13.4, p.260]
Distinguish between spinal and cranial nerves. [13.4, p.260, Fig. 13.15]
Describe the somatic system and list the features of a path of a spinal reflex. [13.4, p.261, Fig. 13.16, Table
13.1]
Describe the autonomic nervous system, and cite similarities and differences in the structure and function of
the two divisions. [13.4, pp.262-263, Fig. 13.17, Table 13.1]
Describe drug action at a synapse, and discuss the effects of alcohol, nicotine, cocaine, heroin, and marijuana.
[13.5, pp.264-265, Figs. 13.18 & 13.19]
Describe the role of the nervous system in homeostasis. [13.6, p.266]
Dis cuss how the nervous system works with other body systems to maintain homeostasis. [13.6, pp.266-267,
Human Systems Work Together]
List two degenerative nervous system diseases, their causes and symptoms. [13.6, p. 266, Fig. 13.20]
Understand and use the bold-faced and italicized terms included in this chapter. [Understanding Key Terms,
p.269]
EXTENDED LECTURE OUTLINE
13.1 Nervous Tissue
The nervous system contains neurons and neuroglial cells that service neurons.
Neuron Structure
Neurons are composed of dendrites, a cell body, and an axon. Long axons are covered by a myelin sheath. Sensory
neurons take information from sensory receptors to the CNS; interneurons occur within the CNS, and motor
neurons take information from the CNS to effectors (muscles or glands).
67
Myelin Sheath
Long axons are covered by a myelin sheath formed by neuroglial cells called Schwann cells, interrupted by gaps
called nodes of Ranvier. A myelin sheath gives nerve fibers their white, glistening appearance and plays an
important role in nerve regeneration within the PNS.
The Nerve Impulse
The nervous system sends messages using the nerve impulse which can be recorded using an oscilloscope.
Resting Potential
As recorded by an oscilloscope, when an axon is not conducting a nerve imp ulse, the inside of an axon is negative
(-65mV) compared to the outside. The sodium-potassium pump actively transports Na + out of an axon and K+ to
inside an axon. The resting potential is due to the leakage of K+ to the outside of the neuron.
Action Potential
An action potential is a rapid change in polarity as the nerve impulse occurs. It is an all-or-none phenomenon and
occurs only when threshold is reached.
Sodium Gates Open
The gates of sodium channels open first and Na + flow into the axon. The membrane potential depolarizes
to +40 MV.
Potassium Gates Open
The gates of potassium channels open and K+ flows into the axon. The membrane potential repolarizes to
-65 MV.
Propagation of an Action Potential
The action potential occurs in each successive portion of an axon. A refractory period ensures that the action
potential will not move backwards. In myelinated fibers the action potential only occurs at the nodes of Ranvier.
This is called saltatory conduction.
Transmission Across a Synapse
Transmission of the nerve impulse from one neuron to another takes place at a synapse when a neurotransmitter
molecule is released from an axon bulb into a synaptic cleft. The binding of the neurotransmitter to receptors in the
postsynaptic membrane causes either excitation or inhibition.
Synaptic Integration
One thousand to ten thousand synapses per single neuron is not uncommon. Excitatory signals have a
depolarizing effect, and inhibitory signals have a hyperpolarizing effect on the post synaptic membrane.
Integration is the summing up of these signals.
Neurotransmitter Molecules
Two well known neurotransmitters are acetylcholine (Ach) and norepinephrine (NE) but at least 25
different neurotransmitters have been identified. Neurotranmitters that have done their job are removed.
The enzyme acetylcholinesterase (AChE) breaks down acetylcholine. Many drugs work by interfering
with the action of neurotransmitters.
Mader VRL CD-ROM
Image 0243l.jpg (Fig. 13.1)
Image 0244l.jpg (Fig. 13.2)
Image 0245l.jpg (Fig. 13.3)
Image 0246a l.jpg (Fig. 13.4)
Image 0246bl.jpg (Fig. 13.4)
Image 0246cl.jpg (Fig. 13.4)
Image 0247al.jpg (Fig. 13.5)
Image 0247bl.jpg (Fig. 13.5)
Image 0247cl.jpg (Fig. 13.5)
Image 0247dl.jpg (Fig. 13.5)
Image 0248l.jpg (Fig. 13.6)
68
Dynamic Human 2.0 CD-ROM
Nervous/Histology/Astrocyte(s)
Nervous/Histology/Spinal Neuron(s)
Life Science Animations VRL 2.0
Mader ESP Modules Online
Transparencies
Animal Biology/Nervous System/ Organization of Nervous
System in Humans
Animal Biology/Nervous System/ Synapse Structure and
Function
Animal Biology/Nervous System/ Transmission Across a
Synapse
Animal Biology/Nervous System/ Generation of an Action
Potential
Animal Biology/Nervous System/Action Potential
Animal Biology/Nervous System/ Development of Membrane
Potential
Animal Biology/Nervous System/ The Nerve Impulse
Animals/Nervous System/Introduction
Animals/Nervous System/Nervous Tissue
Animals/Nervous System/Action Potential
Animals/Nervous System/Synapse
182 (Fig. 13.1b)
183 (Fig. 13.2)
184 (Fig. 13.3a)
185 (Fig. 13.4a, b)
186 (Fig. 13.4d)
187 (Fig. 13.5)
188 (Fig. 13.6)
13.2 The Central Nervous System
The CNS consists of the spinal cord and brain, which are both protected by bone, meninges, and cerebrospinal
fluid. The CNS receives and integrates sensory input and formulates motor output. The CNS is composed of short,
nonmyelinated gray matter and myelinated tracts called white matter.
The Spinal Cord
The spinal cord extends from the base of the brain and is located in the vertebral canal formed by the vertebrae.
Structure of the Spinal Cord
The gray matter of the spinal cord contains neuron cell bodies; the white matter consists of myelinated
axons that occur in bundles called tracts. Because these tracts cross over, the left side of the brain controls
the right side of the body and vice versa. The spinal cord also has a central canal.
Functions of the Spinal Cord
The spinal cord carries out reflex actions and sends sensory information to the brain and receives motor
output from the brain. When the spinal cord is severed, a loss of sensation and motor control occurs in
areas below the site of injury.
The Brain
The brain has four cavities called ventricles. The cerebrum can be associated with the two lateral ventricles.
The Cerebrum
The cerebrum has two cerebral hemispheres connected by the corpus callosum. Sensation, reasoning,
learning and memory, and also language and speech take place in the cerebrum. Each cerebral
hemisphere contains a frontal, parietal, occipital, and temporal lobe.
69
The cerebral cortex is a thin layer of gray matter covering the cerebrum. The primary motor area in the
frontal lobe sends out motor commands to lower brain centers that pass them on to motor neurons. The
primary somatosensory area in the parietal lobe receives sensory information from lower brain centers in
communication with sensory neurons. Association areas are located in all the lobes; the prefrontal area of
the frontal lobe is especially necessary to higher mental functions. A visual association area occurs in the
occipital lobe, and an auditory association area occurs in the temporal lobe.
In the white matter of the cerebrum where myelinated axons are arranged in tracts, masses of gray
matter called basal nuclei serve as relay stations for motor impulses from the primary motor area.
The Diencephalon
The diencephalon encloses the third ventricle. Within the diencephalon, the hypothalamus controls
homeostasis, and the thalamus specializes in sending sensory input, except for smell, to the cerebrum.
The pineal gland of the diencephalon secretes melatonin.
The Cerebellum
The cerebellum primarily coordinates muscle contractions.
The Brain Stem
The brain stem contains the midbrain, the pons, and the medulla oblongata. The midbrain relays impulses
from the cerebrum and spinal cord or cerebellum and houses reflexes for visual, auditory, and tactile
responses. The medulla oblongata and pons have reflex centers for vital functions, like breathing and the
heartbeat.
Within the reticular formation a complex network of nuclei and fibers that extend the length of the brain
stem called the reticular activating system arouses the cerebrum via the thalamus.
Mader VRL CD-ROM
Image 0249l.jpg (Fig. 13.7)
Image 0250al.jpg (Fig. 13.8)
Image 0250bl.jpg (Fig. 13.8)
Image 0250cl.jpg (Fig. 13.8)
Image 0251al.jpg (Fig. 13.9)
Image 0251bl.jpg (Fig. 13.9)
Image 0252l.jpg (Fig. 13.9b)
Image 0253al.jpg (Fig. 13.10)
Image 0253bl.jpg (Fig. 13.10)
Image 0254l.jpg (Fig. 13.11)
Dynamic Human 2.0 CD-ROM
Nervous/Anatomy/3D Viewer
Nervous/Anatomy/Gross Anatomy: Brain
Nervous/Anatomy/Gross Anatomy: Spinal Cord
Nervous/Histology/Spinal Cord
Life Science Animations VRL 2.0
Animal Biology/Nervous System/ Human Brain
Mader ESP Modules Online
Animals/Nervous System/Human Nervous System
Animals/Nervous System/Central Nervous System
Transparencies
189 (Fig. 13.7)
190 (Fig. 13.8a, b)
191 (Fig. 13.9a)
192 (Fig. 13.10)
193 (Fig. 13.11)
70
13.3 The Limbic System and Higher Mental Functions
The limbic system is known to generate primitive emotions and function in higher mental functions.
Limbic System
Within the limbic system, the hippocampus makes the prefrontal area aware of past experiences, and the amygdala
causes such experiences to have emotions associated with them.
Higher Mental Functions
Memory and Learning
Memory is the capacity to retain a thought or recall an event or other information from the past. Learning
takes place when we retain and utilize past memories.
Types of Memory: Short-term memory and long-term memory are dependent upon the prefrontal area.
Long-term memory includes semantic memory (numbers, words, etc.) and episodic memory (persons,
events, etc.) Skill memory is involved in performing motor activities.
Long-term Memory Storage and Retrieval: The hippocampus acts as a conduit for sending information
to long-term memory and retrieving it once again. The amygdala adds emotional overtones, such as fear,
to memories.
Long-term Potentiation: On the cellular level, long-term potentiation seems to be required for long-term
memory. Unfortunately, long-term potentiation can go awry when neurons become overexcited and die.
Drugs are being developed in the hope they will prevent disorders like Alzheimer disease.
Language and Speech
Language and speech are dependent upon Broca’s area (a motor speech area) and Wernicke’s area (a
sensory speech area) that are in communication. Interestingly enough, these two areas are located only in
the left hemisphere.
Mader VRL CD-ROM
Image 0255l.jpg (Fig. 13.12)
Image 0256l.jpg (Fig. 13.13)
Image 0257l.jpg (Fig. 13.14)
Case Studies Online
Behavior Disordered Students
Why Do My Students Sleep in Biology Class?
Transparencies
194 (Fig. 13.12)
195 (Fig. 13.13)
13.4 Peripheral Nervous System
The peripheral nervous system contains only nerves (bundles of axons) and ganglia (cell bodies) There are cranial
nerves and spinal nerves. Dorsal root ganglia contain the cell bodies of sensory neurons.
Somatic System
The brain is always involved in voluntary actions but reflexes are automatic, and some do not require involvement
of the brain.
The Reflex Arc
When a reflex occurs a stimulus causes sensory receptors to generate nerve impulses which are conducted
by sensory nerve fibers to interneurons in the spinal cord. Interneurons signal motor neurons which
conduct nerve impulses to a skeletal muscle that contracts, giving the response to the stimulus.
Autonomic System
The autonomic (involuntary) system controls smooth muscle of the internal organs and glands. Table 13.1
contrasts the two divisions of the autonomic system.
Sympathetic Division
The sympathetic division is associated with responses that occur during times of stress.
Parasympathetic Division
The parasympathetic system is associated with responses that occur during times of relaxation.
71
Mader VRL CD-ROM
Image 0258l.jpg (Fig. TA13.1)
Image 0259al.jpg (Fig. 13.15)
Image 0259bl.jpg (Fig. 13.15)
Image 0259cl.jpg (Fig. 13.15)
Image 0260l.jpg (Fig. 13.16)
Image 0261l.jpg (Fig. 13.17)
Image 0262l.jpg (Fig. TA13.2)
Image 0263l.jpg (Fig. TA13.3)
Dynamic Human 2.0 CD-ROM
Nervous/Explorations/Motor and Sensory Pathways
Nervous/Explorations/Neural Network
Nervous/Explorations/Reflex Arc
Nervous/Histology/Dorsal Root Ganglion
Life Science Animations VRL 2.0
Animal Biology/Nervous System/Reflex Arc
Animal Biology/Nervous System/ Reflex Arc Showing Path of a
Spinal Reflex
Mader ESP Modules Online
Animals/Nervous System/Peripheral Nervous System
Transparencies
196 (Fig. TA13.1)
197 (Fig. 13.15)
198 (Fig. 13.16)
199 (Fig. 13.17)
200 (Fig. TA13.2 - TA13.3)
13.5 Drug Abuse
Although neurological drugs are quite varied, each type has been found to either promote or prevent the action of a
particular neurotransmitter or to impact the limbic system. With physical dependence, formerly called addiction,
more of the drug is needed to cause the same effect, and withdrawal symptoms are experienced if taking the drug
is stopped.
Alcohol
Alcohol may affect the inhibiting transmitter GABA or glutamate, an excitatory neurotransmitter. Alcohol is
primarily metabolized in liver, where fat metabolism is interrupted. Cirrhosis of the liver and fetal alcohol
syndrome are serious conditions associated with alcohol intake.
Nicotine
Nicotine is an alkaloid derived from tobacco. In the CNS, nicotine causes neurons to release dopamine; in the PNS
mimics the activity of acetylcholine. Nicotine induces both physiological and psychological dependence.
Cocaine
Cocaine is an alkaloid derived from the shrub Erythroxylum cocoa, often sold as potent extract termed “crack.”
Cocaine, which prevents reuptake of dopamine by the presynaptic membrane, is highly addictive and over-dosing
is a real possibility.
Heroin
Derived from morphine, heroin is an alkaloid of opium. It alleviates pain by preventing release of substance P
from sensory neurons in spinal cord and bind to receptors meant for body’s own opiates (endorphins).
Marijuana
Marijuana is obtained from Cannabis sativa. Effects depend upon strength and the amount consumed, expertise,
and setting.
72
Mader VRL CD-ROM
Image 0264l.jpg (Fig. 13.18)
Image 0265l.jpg (Fig. 13.19)
Life Science Animations VRL 2.0
Animal Biology/Nervous System/Drug Addiction
Transparencies
201 (Fig. 13.18)
13.6 Homeostasis
A Human Systems Work Together box shows how the nervous system works with other systems of the body to
bring about homeostasis.
Degenerative Nervous System Diseases
Alzheimer Disease
Alzheimer disease (AD) occurs as plaques and neurofibrillary tangles appear throughout the brain, but
especially in the hippocampus and amygdala. Patients with AD produce too much beta amyloid which
triggers an inflammatory reaction and kills neurons. A gradual loss of reason and memory is associated
with AD.
Parkinson Disease
Parkinson disease occurs when the basal nuclei are overactive and cause degeneration of the dopaminereleasing neurons in the brain. The patient develops hand tremors and a shuffling gait.
Mader VRL CD-ROM
Image 0266l.jpg (Fig. 13.20)
Image 0267al.jpg (Fig. TA13.4)
Image 0267bl.jpg (Fig. TA13.4)
Image 0268l.jpg (Fig. TA13.5)
Dynamic Human 2.0 CD-ROM
Nervous/Clinical Concepts/Carpal Tunnel Syndrome
Nervous/Clinical Concepts/MRI Stroke
Nervous/Clinical Concepts/Stroke
Life Science Animations VRL 2.0
Animal Biology/Nervous System/Stroke
Transparencies
202 (Fig. 13.20)
203 (Fig. TA13.4)
204 (Fig. TA13.5)
SEVENTH EDITION CHANGES
New/Revised Text:
This was chapter 12 in the previous edition. This chapter has been extensively reorganized. Many
sections and topics have been rewritten. The central nervous system, limbic system, memory, language, and
speech are discussed before the peripheral nervous system. Homeostasis ends the chapter.
13.1 Nervous Tissue was previously entitled Neurons and How They Work. Neuron Structure and
Myelin Sheath have been rewritten. Synaptic Integration now follows the discussion of transmission across a
synapse.
13.2 The Central Nervous System is discussed next in the logical sequence of spinal cord and brain.
Functions of the Spinal Cord has been rewritten and now discusses the role the spinal cord plays in regulating
internal organs in addition to the skeletal muscles. Parts of the brain are discussed in more depth.
13.3 The Limbic System and Higher Mental Functions contains discussions of the limbic system,
memory and learning, and language and speech. (The discussion of Alzheimer disease has been moved to the end
of the chapter).
13.4 The Peripheral System. The organization and content of this section remains essentially the same as
in the last edition.
73
13.6 Homeostasis has been expanded to include discussions of two degenerative nervous system diseases,
Alzheimer disease and Parkinson disease. The Alzheimer disease discussion has been updated with the newest
information, and the Parkinson disease discussion is new to this chapter.
New/Revised Figures:
13.1 Organization of the nervous system; 13.3 Myelin sheath; 13.4 Resting and action potential; 13.5
Synapse structure and function; 13.6 Integration; 13.7 Organization of the nervous system; 13.9 The human brain;
13.10 The cerebral cortex; 13.12 The limbic system; 13.13 Long-term memory circuits; 13.15 Cranial and spinal
nerves; 13.16 A reflex arc; 13.18 Drug actions at a synapse; 13.19 Drug use; 13.20 Alzheimer disease.
STUDENT ACTIVITIES
Overcoming Chemical Dependence
1. Invite a physician and/or a counselor from a chemical dependency treatment center to visit the class and
describe their attempts to help people overcome their dependence on alcohol or other drugs. Differentiate
between a physiological addiction and a psychological dependence. Ask the counselor to give your students
suggestions about how they can avoid chemical dependency and how to recognize when one exists.
Sensory Adaptation
2. Many sensory receptors stop firing impulses after a brief period. For example, after applying cologne or
perfume, you may not be able to detect the scent after a short time. Demonstrate sensory adaptation to your
students.
First, ask a volunteer to leave the room, to apply a moderate amount of cologne to a washcloth, and to reenter
the room. Most students will detect the fragrance immediately. Set the cloth on a front table. Change the
subject for a bit, and then ask students again whether they can detect the cologne.
An alternate exercise involves thermoreceptors and sensory adaptation. Many of us know that acclimating to
the colder temperatures of winter takes time. We have also experienced a too-warm bath that felt just right
after we had been immersed a few minutes. Do a similar demonstration for your class. Ask three volunteers to
come to the front of the class. Have three small basins full of water--one quite warm (but not so hot as to burn
the skin), another room temperature, and a third cold. Ask three students to each place a hand in one of the
three basins. Have them describe the temperature of the water. Wait a few minutes until the students can claim
that they are used to the water temperature (it no longer feels “hot,” “cold,” or “warm.” See if students
acclimate in the same amount of time, even for different water temperatures.
How Accurate Is Your Memory?
3. Ask students to put their pens and pencils down and to momentarily not take notes. Using an overhead
projector, show a photograph of a person for a few moments, and say the name of the person once (a
hypothetical name is fine in this case). Turn off the projector, and spend a few minutes discussing how
memory works or another topic to divert student attention. Finally, ask students to recall the name of the
person from the photograph, and to describe their appearance. Relate their difficulty remembering details to
short-term memory and to the futility of cramming for exams.
74