Chapter 2 Brain and Behavior. By the End of this Lecture, Students will be able to:
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Transcript of Chapter 2 Brain and Behavior. By the End of this Lecture, Students will be able to:
Chapter 2Brain and Behavior
By the End of this Lecture, Students will be able to:
Neuron and Its Parts
• Neuron: Individual nerve cell– Dendrites: Receive messages from other neurons– Soma: Cell body; body of the neuron– Axon: Fiber that carries information away from the
cell body– Axon Terminals: Branches that link the dendrites
and somas of other neurons
Figure 2.1
FIGURE 2.1 A neuron, or nerve cell. In the right foreground you can see a nerve cell fiber in cross section. The upper left photo gives a more realistic picture of the shape of neurons. Nerve impulses usually travel from the dendrites and soma to the branching ends of the axon. The nerve cell shown here is a motor neuron. The axons of motor neuron stretch from the brain and spinal cord to muscles or glands of the body.
Synapses
Messages from one neuron to another pass over a microscopic gap called a synapse– Synapse: Microscopic gap between two
neurons over which messages pass
Figure 2.5
FIGURE 2.5 A highly magnified view of a synapse. Neurotransmitters are stored in tiny sacs called synaptic vesicles (VES-ihkels). When a nerve impulse reaches the end of an axon, the vesicles move to the surface and release neurotransmitters. These molecules cross the synaptic gap to affect the next neuron. The size of the gap is exaggerated here; it is actually only about one millionth of an inch. Some transmitter molecules excite the next neuron, and some inhibit its activity.
Neurotransmitters
• Chemicals that alter activity in neurons; brain chemicals that carry messages.– Acetylcholine: Activates muscles– Dopamine: Muscle control– Serotonin: Mood and appetite control
• Receptor Site: Areas on the surface of neurons and other cells that are sensitive to neurotransmitters
Nerves and Neurons
• Nerves: Large bundles of axons and dendrites (Not neurons)
• Myelin: Fatty layer of tissue that coats axons– Multiple Sclerosis (MS) occurs when myelin layer
is destroyed; numbness, weakness, and paralysis occur
• Neurogenesis: Production of new brain cells
Neural Networks
• Central Nervous System (CNS): Brain and spinal cord• Peripheral Nervous System: All parts of the nervous
system outside of the brain and spinal cord– Somatic System: Links spinal cord with body and
sense organs; controls voluntary behavior– Autonomic System: Serves internal organs and
glands; controls automatic functions such as heart rate and blood pressure
Figure 2.6
FIGURE 2.6 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and the autonomic nervous system.
Two Divisions of the Autonomic System
• Sympathetic: Arouses body; emergency system• Parasympathetic: Quiets body; most active after an emotional
event
Figure 2.8
FIGURE 2.8 Sympathetic and parasympathetic branches of the autonomic nervous system. Both branches control involuntary actions. The sympathetic system generally activates the body. The parasympathetic system generally quiets it. The sympathetic branch relays its messages through clusters of nerve cells outside the spinal cord.
Figure 2.7
FIGURE 2.7 Subparts of the nervous system.
Researching the Brain
• Computed Tomographic Scanning (CT): Computer-enhanced X-ray image of the brain or body
• Magnetic Resonance Imaging (MRI): Uses a strong magnetic field, not an X-ray, to produce an image
• Functional MRI (fMRI): MRI that also records brain activity
• Positron Emission Tomography (PET): Computer-generated color image of brain activity, based on glucose consumption in the brain
Cerebral Cortex
• Definition: Outer layer of the cerebrum• Cerebrum: Two large hemispheres that cover upper
part of the brain• Corticalization: Increase in size and wrinkling of the
cortex• Cerebral Hemispheres: Right and left halves of the
cortex• Corpus Callosum: Bundle of fibers connecting
cerebral hemispheres
Split Brains
• Corpus Callosum is cut; done to control severe epilepsy (seizure disorder).
• Result: The person now has two brains in one body.• This operation is rare and is often used as a last
resort.
Figure 2.19
FIGURE 2.19 Basic nerve pathways of vision. Notice that the left portion of each eye connects only to the left half of the brain; likewise, the right portion of each eye connects to the right brain. When the corpus callosum is cut, a “split brain” results. Then visual information can be sent to just one hemisphere by flashing it in the right or left visual field as the person stares straight ahead.
Figure 2.22
Figure 2.18
Spatial neglect resulting from a right hemisphere stroke. Notice the neglect of the left side of the pictures which were being reproduced.
When the Brain Fails to Function Properly
• Broca’s Area: Related to language and speech production– If damaged, person knows what s/he wants to say
but can’t say the words• Wernicke’s Area: Related to language comprehension– If damaged, person has problems with meanings
of words, NOT pronunciation
Figure 2.25
FIGURE 2.25 This simplified drawing shows the main structures of the human brain and describes some of their most important features. (You can use the color code in the foreground to identify which areas are part of the forebrain, midbrain, and hindbrain.)
Limbic system
• First studied By:
– Paul Broca (1824-1880)– James Papez (1883-1958)
Forebrain
• Structures are part of the Limbic System: System within forebrain closely linked to emotional response– Thalamus: Relays sensory information to the
cortex; switchboard– Hypothalamus: Regulates emotional behaviors
and motives (e.g., sex, hunger, rage, hormone release)
– Amygdala: Associated with fear responses– Hippocampus (Seahorse): Associated with storing
memories; helps us navigate through space
Figure 2.26
FIGURE 2.26 Parts of the limbic system. Although only one side is shown here, the hippocampus and the amygdala extend out into the temporal lobes at each side of the brain. The limbic system is a sort of “primitive core” of the brain strongly associated with emotion.
• Limbic System: • The Emotional Brain Structures lying deep
within the cerebral hemispheres.
Coordinates behaviors needed to satisfy motivational and emotional urges arising in the hypothalamus.
Also involved in memory.
Functions
• “Emotional brainEmotional and motivational aspects of
behavior.Provides emotional component to learning process:
Especially the amygdala.• Associated with memory
Especially the hippocampus.• Associated with pain/pleasure, rage
• Limbic System: Structure
Hippocampus: Learning and Memory
• Limbic System: Structure
Hippocampus: Learning and Memory
Amygdala:Emotions and Aggression
Functions of the Amygdala
• Relate environmental stimuli to coordinated behavioral autonomic and endocrine responses seen in species-preservation.
• Plasticity• Responding to stress• Vigilance/attention• Learning about emotional stimuli• Pavlovian learning, or classical conditioning• Affective state
• Responses include:
Feeding and drinking
Agnostic (fighting) behavior
Mating and maternal care
Responses to physical or emotional stresses.
Model of associative learning in the amygdala
• Limbic System: Structure
Hippocampus: Learning and Memory
Amygdala: Emotions and Aggression
Hypothalamus:Hunger, ThirstTemperature Control
• Limbic System: Structure
Hippocampus: Learning and Memory
Amygdala: Emotions and Aggression
Hypothalamus:Hunger, ThirstTemperature Control
Thalamus:Relay Center for SensoryInformation
• Limbic System: Structure
Hippocampus: Learning and Memory
Amygdala: Emotions and Aggression
Hypothalamus:Hunger, ThirstTemperature Control
Thalamus:Relay Center for SensoryInformation
Pathologies (lesions)
• Voracious appetite• Increased (perverse) sexual activity• Docility:
Loss of normal fear/anger response• Memory loss:
Damage to hippocampus portion:Cells undergoing calcium-induced
changes associated with memory
Kluver-Bucy Syndrome:
• Results from bilateral destruction of amygdala.• Characteristics:
Increase in sexual activity.Compulsive tendency to place objects in
mouth.Decreased emotionality.Changes in eating behavior.Visual agnosia.
Stress
1. A state of threatened homeostasis
2. The thing responsible for the imbalance. aka stressor
3. The body’s response to the imbalance. aka stress-response
The Flight or Fight Response
1. Perceive extreme danger or distress2. Neurons send entire body into “high gear”3. Responsively prepare for “fight or flight”“flight or flight” response = generalized set of changes
in cardiovascular, respiratory, blood flow, and metabolic systems, such as increased blood glucose (e.g.Cannon, 1920)
Hans Selye Experiment
• Early research project: Ovarian extract—What does it do?– Inject rats every day ulcers, enlarged adrenal
glands, & shrunken immune tissues– So did control rats!!– So did others subjected to cold, heat, forced
exercise, surgical procedures– Stress!
Selye’s General Adaptation Syndrome (GAS)
• Described as body’s adaptive response to stress– Stage 1: The alarm reaction in which the
body prepares itself for “fight or flight.”– Stage 2: Since the first stage cannot long be
sustained, there is a general resistance to the stress which is established.
– Stage 3: If the stress is continued for a long period of time, then eventual exhaustion results (the body’s response to prolonged “wear and tear”).
Selye’s Third Stage
• Overcome by physiological, psychological, and environmental changes (stressors)
• Failure to accommodate to changes can lead to exhaustion
• Currently extensive investigation into this as potential contributor to many “western” health problems.
The stress response is non-specific
short-term
adaptive
long-term
maladaptive
Two component stress-response
The fastest response to stress is the activation of the Autonomic Nervous System (ANS) • ON: seconds
The slow response to stress is activation of the Hypothalmus-Pituitary-Adrenal axis (HPA) • ON: minute(s)
Psychological Variables
Learning and habituationSocial factorsIndividual differences
Social Factors
Most studies show that dominant animals have lower cortisol than subordinate animalsParticularly with social unrest
Ex: Vervet monkeys in captivity form social hierarchy then dominants constantly harass subordinates.
Subordinate animals died at younger age and had enlargedadrenal glands, atrophied hippocampus and ulcers (sounds like Selye’s rats)
Opposite Outcome: Dominant African wild dogs and mongooses have higher cortisol than subordinate-likely due to constant defense of hierarchy
Individual differences
• Subordinate baboons = sicker? Too simplistic• Dominant males may fight to stay on top.
• If subordinates not harassed not bad– Things are worst during stable hierarchy ie
dominants have no real challenges so they harass subordinates.
• Social support: groom females, play with kids• Status rising or falling• Glass half full/half empty
Social support appears to serve as a “stress buffer”
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Also, time required to return to baseline:
Paired: 45 min
Single: 75 min
***lactating women and female rats also have dampened HPA axis responses*****
Stress and health
• Long-term uncontrollable stress – Inhibits immune system– Depletes energy stores • always tired, muscle weakness
– Disrupts limbic function• Increases depression• (Interferes with memory)
• Antidepressants • hippocampal neurogenesis as they improve mood.