Module 3.1

1
Module 3.1

• The Nervous System and Behavior

2
Introduction

• Explanations for Behavior
• Physiological explanations describe the
  mechanisms that produce behaviors.

3
Measuring Brain Activity

• Methods for looking at and mapping the brain
  include
• Electroencephalographs (EEG) record electrical
  activity in the brain.

4
Measuring Brain Activity

• Positron emission tomography (PET) provides a
  high-resolution picture of brain activity using
  radioactivity from chemicals injected into the
  bloodstream.

5
Measuring Brain Activity

• Functional magnetic resonance imaging (fMRI) uses
  magnetic detectors outside the head to measure
  the amounts of hemoglobin and oxygen in different
  areas of the brain.

6
The Major Divisions of the Nervous System

• The central nervous system and the peripheral
  nervous system

7
The Major Divisions of the Nervous System

• The peripheral nervous system is composed of
  bundles of axons between the spinal cord and the
  rest of the body.
• There are two sets of subdivisions of the
  peripheral nervous system.

8
The Peripheral Nervous System

• The somatic nervous system and autonomic nervous
  system

9
Figure 3.5

• Figure 3.5 The human brain begins development as
  three lumps. By birth the forebrain has grown
  much larger than either the midbrain or the
  hindbrain, although all three structures perform
  essential functions.

10
The Forebrain

• General structure
• The forebrain
• The forebrain has two separate hemispheres, left
  and right.
• Each hemisphere controls sensation and motor
  functioning on opposite side of body.
• Hemispheres communicate with each other through a
  thick bundle of axons crossing between them
  corpus callosum

11
The Forebrain

• Cerebral cortex
• The cerebral cortex
• The outer covering of the forebrain is known as
  the cerebral cortex.
• It is made up of gray matter, the cell bodies of
  the cortical neurons.

12
The Forebrain

• Cerebral cortex
• The four lobes of the cerebral cortex
• Its customary to represent the areas of the
  cerebral cortex as four lobes
• Occipital
• Parietal
• Temporal
• Frontal

13
The Forebrain

• Other structures that lie under or near the
  temporal lobe
• hypothalamus
• Amygdala
• Hippocampus

14
The Forebrain

• Cerebral cortex
• Contains primary motor cortex, an area important
  for control of fine movements.
• Prefrontal cortex is responsible for planning of
  action, organization, aspects of memory.

15
Figure 3.8

• Figure 3.8 The four lobes of the human cerebral
  cortex, with indications of some of their major
  functions.

16
Between the Spinal Cord and the Forebrain

• The hindbrain midbrain
• The medulla, pons, midbrain contain the
  reticular formation
• regulates levels of arousal in the brain

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How the Cerebral Cortex Communicates with the Body

• The hindbrain
• Cerebellum is linked to coordination timing
• also in charge of tasks that require shifting of
  attention and discrimination between stimuli

18
How the Cerebral Cortex Communicates with the Body

• The hindbrain
• medulla oblongata and the pons contain
• axons that control breathing and heart rate
• They relay sensory information from the head and
  sending motor messages back to it.

19
Figure 3.6

• Figure 3.6 The major divisions of the human
  central nervous system, as seen from the midline.

20
The Peripheral Nervous System

• The autonomic nervous system
• The divisions of the autonomic nervous system
• The sympathetic nervous system

21
The Peripheral Nervous System

• The autonomic nervous system
• The divisions of the ANS
• The parasympathetic nervous system runs long-term
  survival-related functions, nutrition, and energy
  conservation.

22
Figure 3.12

• Figure 3.21 The sympathetic nervous system
  prepares the body for brief bouts of vigorous
  activity the parasympathetic nervous system
  promotes digestion and other non-emergency
  functions. Although both systems are active at
  all times, the balance can shift from a
  predominance of one to a predominance of the
  other.

23
The Endocrine System

• The endocrine system is under the control of the
  nervous system.
• The endocrine system is a system of glands that
  release hormones into the bloodstream.
• Hormones are chemicals that affect mood,
  behavior, and even anatomy.

24
Figure 3.13

• Figure 3.13 Glands in the endocrine system
  produce hormones and release them into the
  bloodstream. This shows only some of the
  endocrine glands and some of their most abundant
  hormones.

25
Experience and the brain

• The two halves of the brain
• Work with individuals who have had the
  split-brain operation (severing the corpus
  callosum) to control seizures provides evidence
  that the two hemispheres are highly specialized.

26
Module 3.2

• Neurons and Behavior

27
Nervous System Cells

• Neurons
• The cells that make up your nervous system are
  called neurons.
• Neurons are a unique type of cell that can
  receive and transmit information electrochemically

28
 Figure 3.18

• Figure 3.18 Distribution of the estimated 100
  billion neurons in the adult human central
  nervous system. (Based on data of R. W. Williams
  Herrup, 1988)

29
Nervous System Cells

• Anatomy of a neuron
• Neurons have a variety of shapes, but they all
  have 3 basic parts.
• A cell body that contains the nucleus and most of
  the organelles.
• The dendrites, widely branching structures that
  receive transmissions from other neurons.
• The axon, a single, long, thin fiber with
  branches near its tip.

30
 Figure 3.20

• Figure 3.20 The generalized structure of a motor
  neuron shows the dendrites, the branching
  structures that receive transmissions from other
  neurons, and the axon, a single, long, thin,
  straight fiber with branches near its tip. Axons
  range in length from 1 millimeter to more than 1
  meter and carry information to other cells.
  Inset A photomicrograph of a neuron.

31
Nervous System Cells

• Axons
• The function of the axon is to send the
  electrochemical message on to the next cell.
• Most axons transmit information to the dendrites
  or cell bodies of neighboring neurons.
• Many axons have a coating of myelin, which speeds
  up transmission.

32
Nervous System Cells

• Nerve cell growth
• Neurons do not have a fixed anatomy.
• Researchers have discovered that neurons are
  constantly growing and losing branches to
  dendrites and axons.
• This growth seems to be related to new
  experiences and learning.

33
Nervous System Cells

• Action potentials
• Axons convey information by a combination of
  electrical and chemical processes.
• This combination is called an action potential.
• An action potential is an excitation that travels
  along the axon at a constant strength regardless
  of the distance it must travel.

34
ANIMATION Neuron and Neural Impulse
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35
Nervous System Cells

• Action potentials
• The all-or-none law
• An action potential is an all-or-nothing process
  its either happening or not theres no sort
  of action potential.
• This allows the message to reach the brain at
  full strength, but does slow it down compared to
  regular electrical conduction.

36
Nervous System Cells

• Action potentials
• How an action potential works
• An un-stimulated axon has resting potential.
• Resting potential is an electrical polarization
  across the membrane covering the axon.
• A polarized axon has an inside charge that is
  negative (-70 millivolts) relative to the outside.

37
Nervous System Cells

• Action potentials
• How an action potential works
• Resting potential is maintained by the mechanism
  called the sodium-potassium pump.
• Sodium is mostly concentrated outside the neuron,
  and potassium mostly inside

38
Nervous System Cells

• Action potentials
• How an action potential works
• The sodium-potassium pump sends positively
  charged (1) sodium ions out of the cell and
  brings in a smaller number of positively charged
  (1) potassium ions.
• The result is that the outside of the cell has
  more positive charges than the inside.

39
Nervous System Cells

• Action potentials
• How an action potential works
• When a message from a neighboring cell excites
  part of the axons membrane, some of the sodium
  gates are opened and sodium can enter the axon.
• This makes the charge inside the cell positive.
  Depolarization has taken place.

40
Figure 3.22

• Figure 3.22 (a) During an action potential,
  sodium gates in the neuron membrane open, and
  sodium ions enter the axon, bringing a positive
  charge with them. (b) After an action potential
  occurs at one point along the axon, the sodium
  gates close at that point and open at the next
  point along the axon. When the sodium gates
  close, potassium gates open, and potassium ions
  flow out of the axon, carrying a positive charge
  with them. (Modified from Starr Taggart, 1992)

41
Nervous System Cells

• Synapses
• Communication between neurons occurs at the
  synapses.
• A synapse is a specialized junction between two
  neurons.
• Chemicals released by one will either excite or
  inhibit the other, making it either more or less
  likely to produce an action potential.
• This activity at the synapses is crucial to
  everything the brain does.

42
Figure 3.24

• Figure 3.24 The synapse is the junction of the
  presynaptic (message-sending) cell and the
  postsynaptic (message-receiving) cell. At the end
  of the presynaptic axon is the terminal bouton
  (or button), which contains many molecules of the
  neurotransmitter, ready for release.

43
Nervous System Cells

• Synapses
• Synaptic communication
• Each axon has a bulge at the end called a
  pre-synaptic ending or a terminal bouton
  (alternately spelled button.)
• When the action potential reaches the terminal
  bouton, molecules of a neurotransmitter are
  released.
• A neurotransmitter is a chemical that is stored
  in the neuron. It activates special receptors of
  other neurons.

44
ANIMATION Synaptic Transmission
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45
Module 3.3

• Drugs and their effects

46
The Survey of Abused Drugs and Their Effects

• The biological basis of drug abuse and addiction
• Nearly all abused and addictive drugs increase
  activity at the dopamine receptors in the brain.
• These drugs increase the release of dopamine,
  interfere with reuptake, and stimulate neurons
  that release dopamine or decrease activity of
  neurons that inhibit its release.

47
The Survey of Abused Drugs and Their Effects

• The biological basis of drug abuse and addiction
• The addictive actions of dopamine particularly
  work upon a small brain area called the nucleus
  accumbens, a central area for attention and
  habit-formation.
• Activities such as gambling and video game
  playing can have the same biological effects.
• Addiction can be thought of as in the person, not
  in the drug.

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 Figure 3.30

• Figure 3.30 Both legal and illegal drugs
  operate at the synapse. Drugs can increase the
  release of neurotransmitters, block their
  reuptake, or block their receptors.

49
The Survey of Abused Drugs and Their Effects

• Stimulants are drugs that boost energy, heighten
  alertness, increase activity and produce a
  pleasant feeling.
• Cocaine and amphetamine are examples of powerful
  stimulant drugs
• The net effect of cocaine is to decrease brain
  activity, which in turn stimulates behavior.
• Free-base and crack cocaine are forms that allow
  the drug to enter the nervous system more
  rapidly, thus producing a more powerful high.

50
The Survey of Abused Drugs and Their Effects

• Ritalin, which is prescribed for children with
  ADD, is a strong but slow-acting stimulant.
• Caffeine, which is an ingredient in coffee, tea,
  and many soft drinks, is a milder and less
  dangerous stimulant drug.
• Cigarettes are nicotine delivery devices.
  Nicotine is a powerfully addictive stimulant.
  Smoking is experienced as relaxing because
  between cigarettes the smoker begins to
  experience withdrawal, which a subsequent
  cigarette will temporarily alleviate.

51
The Survey of Abused Drugs and Their Effects

• Depressants
• Depressants are drugs that largely decrease
  physiological arousal.
• The most commonly used and abused depressants are
  alcohol and tranquilizers.
• These drugs work by facilitating the transmission
  of the neurotransmitter GABA.
• Alcohol is a class of chemicals including
  methanol, ethanol, and propyl (rubbing) alcohol.
• Ethanol is the type found in liquor, wine, and
  beer.

52
The Survey of Abused Drugs and Their Effects

• Depressants - Alcohol
• Alcohol has been consumed in many world cultures
  for millennia.
• It acts primarily as a relaxant when consumed in
  small amounts.
• In greater amounts, it can increase aggressive
  and risk-taking behaviors.

53
The Survey of Abused Drugs and Their Effects

• Depressants - Alcohol
• Excessive consumption of alcohol can damage the
  liver and other internal organs.
• Excessive consumption of alcohol has been related
  to memory impairment and loss of motor control.
• Fetal alcohol syndrome, which can result when a
  pregnant woman consumes alcohol, is the number
  one preventable cause of mental retardation in
  the United States.

54
The Survey of Abused Drugs and Their Effects

• Depressants - Alcohol
• Alcohol abuse and dependence are worldwide public
  health problems.
• They are more common in some cultures than in
  others.
• Ethnic differences in alcohol consumption have
  been related to overall differences in lifespan.
  For example, the relatively greater rates of
  consumption among Native Americans and African
  Americans may constitute part of the reason for
  the shorter average lifespan in these
  populations.

55
The Survey of Abused Drugs and Their Effects

• Depressants Tranquilizers
• Medical doctors have prescribed tranquilizers in
  the past to help people relax and fall asleep.
• They have also been used to suppress epileptic
  seizures.
• Barbiturates, once a legitimately prescribed
  medication for these purposes, proved to be so
  addictive and dangerous that it is rarely
  prescribed today.
• Benzodiazepines, a class that includes drugs such
  as Valium, are milder drugs used for anxiety
  management. They are also highly addictive.

56
The Survey of Abused Drugs and Their Effects

• Narcotics
• Narcotics are drugs that produce drowsiness,
  insensitivity to pain, and overall decreased
  responsiveness to environmental stimuli.
• Opiates are one common type of narcotic.
• Opiates can be derived naturally from the opium
  poppy or synthesized in the laboratory.
• Opiates create a feeling of euphoria.
• Once the drug has been used up, the person begins
  to feel intense withdrawal and a need to use the
  drug again.

57
The Survey of Abused Drugs and Their Effects

• Narcotics
• Researchers have found that the human brain
  produces chemicals called endorphins.
• These neurotransmitters bind to opiate receptors
  and stimulate dopamine production.
• Neurons release endorphins when an individual
  experiences pain or stress.

58
The Survey of Abused Drugs and Their Effects

• Marijuana
• Marijuana is classified as a narcotic, but it
  intensifies sensory experiences and in many ways
  is not like the opiates.
• It has possible medical uses as a mild painkiller
  and nausea suppressant.
• It is a dangerous drug to use. As with tobacco,
  it poses a risk of lung cancer because it is
  usually smoked.

59
The Survey of Abused Drugs and Their Effects

• Marijuana
• It appears to impair learning and memory. The
  active ingredient in marijuana, THC, is
  especially likely to attach to receptors in the
  hippocampus, where memories are consolidated.
• Because of the political overtones, research
  studies of marijuana have been tainted by the
  agenda of the researcher (pro or con) and may be
  unreliable.
• Marijuana is probably no more of a gateway drug
  than are tobacco and alcohol.

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The Survey of Abused Drugs and Their Effects

• Hallucinogens
• Drugs that induce sensory distortions and false
  sensory experiences are called hallucinogens.
• Peyote is an example of a naturally derived
  hallucinogen. It has played an important role in
  Native American religious ceremonies.
• LSD is a hallucinogen that is artificially
  manufactured. It works by altering serotonin
  receptors, but we are still unsure how this leads
  to altered sensory experiences.
• MDMA, also called ecstasy, acts as a stimulant at
  low doses and a hallucinogen at high doses. This
  hallucinogen appears to pose the greatest risk of
  brain damage to the user.