Download The Nervous System

Neuroscience
The Brain and Behavior
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Copyright © Allyn & Bacon 2006
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Neuroscience: The Brain and
Behavior
I.
How is the Nervous System Organized?
II.
How Does the Brain Function?
III. What Effects Do Hormones Have on
Behavior?
IV. How Do Genetic Factors Affect Behavior?
V.
Does Our Evolutionary Heritage Influence
Current Behavior?
Copyright © Allyn & Bacon 2004
How is the Nervous System
Organized?
A. Cellular Level
1. The Neuron = single nerve cell
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The Neuron
Myelin sheath – thin, fatty white coating on the axon
- Speeds up transmission of neural
signals
- Multiple sclerosis causes a loss of
myelination
Structure of neurons
– Dendrites - receive impulses
– Axon - transmit impulses
The Synapse - gap between neurons
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The Functioning of Neurons
– Communication is an electrochemical
process
• Within neurons it is electrical
• Between neurons it is chemical
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The Cellular Level
Neurotransmitters and Behavior
– Communication must cross the synapse
between neurons
– Chemical signal
• At the axon terminal, there is the
release of neurotransmitters (nts)
• The nts bind to receptors on the next
neuron
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Neurotransmitters
•
•
•
•
•
Acetylcholine
GABA
Serotonin
Dopamine
Norephinephrine
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Psychopharmacology
Study of drugs (and neurotransmitters) on
behavior and mental processes
Types of effects of drugs:
Alter amount of nt released
• E.g., Ecstasy causes massive
release of serotonin
• May also block release of nts
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Neurotransmitters, Drugs, and
Behavior
Change the speed at which nts are disabled
after release
• E.g., Prozac and Zoloft slow reuptake of
serotonin: SSRI’S
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How is the Nervous System Organized?
Divisions of the Nervous System
Nervous System
Central Nervous
System (CNS)
Brain
Peripheral Nervous
System
System
(PNS)
Spinal
Cord
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Divisions of the Nervous System
Central Nervous
System
Brain
Spinal
Cord
Peripheral Nervous
System
Somatic
NS
Autonomic
NS
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Peripheral Nervous System
a. Somatic nervous system
– Responds to and acts on the outside world
– Under voluntary control
– Both sensory and motor neurons
b. Autonomic nervous system
– Controls automatic processes
– Two subdivisions: autonomic and
parasympathetic
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Peripheral Nervous System
Peripheral Nervous
System
Somatic
NS
Autonomic
NS
Parasympathetic
Sympathetic
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Peripheral Nervous System
Autonomic Nervous System
a. Sympathetic nervous system
• Activates fight-or-flight response
b. Parasympathetic nervous system
• Controls normal operations and calms
the body
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Divisions of the Nervous System
Central Nervous System
a. Spinal Cord
– Controls spinal reflexes without input
from the brain
• E.g., Knee-jerk reflex
– Relays information to and from the brain
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Central Nervous System
b. The Brain
– Lower structures are involved in more basic
functions like breathing
– Higher structures are involved in more
complex functions like thinking
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Central Nervous System
Brain
Hindbrain
Midbrain
Forebrain
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The Brain
i. The Hindbrain
a) Medulla (breathing and heartbeat)
• Contains the reticular formation
b) Pons (sleep and dreaming)
c) The Cerebellum (balance and posture)
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The Brain
ii. Midbrain
• Collections of cell bodies that receive
signals from the spinal cord and other
parts of the brain
• Involved in smooth movement,
temperature, and some reflexes
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The Brain
iii. The Forebrain
a) Thalamus receives and passes on sensory information
b) Hypothalamus (hunger, thirst, body temperature)
c) The Limbic System (emotions and memory)
• Hippocampus (learning and memory)
• Amygdala – (emotional behaviors)
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iii. The Forebrain
e) Cerebrum
• Largest structure in the human brain
• Two hemispheres
– Connected by the
corpus callosum
–Covered by the
cortex
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iii. The Forebrain
e) Cerebrum
• Four lobes
Parietal
Lobe
Frontal
Lobe
Occipital
Lobe
Temporal
Lobe
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Studying Brain Function
– Electroencephalography (EEG)
• Measures electrical activity
– Computerized tomography (CT) scans
• Computer-enhanced X-rays
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Studying Brain Function
• Magnetic Resonance Imaging (MRI)
– Uses magnetic fields
– Images are clearer and more detailed than CT
scans
• Functional MRI (fMRI)
– Shows differences in activity in brain regions
• Positron Emission Tomography (PET)
– Tracks radioactive markers that have been
injected into the bloodstream
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Brain Specialization
Splitting the brain
• Cerebral hemispheres are not identical
• E.g., left hemisphere more involved in
language
• Information comes from study of split-brain
patients
– Individuals whose corpus callosum has
been cut to treat severe epilepsy
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Left and Right Hemisphere
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Left hemisphere controls the right side of the body and is
involved with language, math, science, analytical
reasoning, logic, and details.
Right hemisphere controls the left side of the body and is
involved with facial recognition, creativity and imagination,
intuition, art and music, and spatial relations. The right
hemisphere is “holistic” rather than analytical.
Both hemispheres are needed for most tasks
Split brain patients can not use left-brain language
abilities to describe right-brain activities
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Splitting the Brain
An image in the left visual field
appears in the right (non-verbal)
hemisphere when looking straight
ahead
????
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Splitting the Brain
An image in the right visual field
appears in the left (verbal)
hemisphere when looking straight
ahead
It’s a silly
yellow and
pink polkadotted bug.
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How Does the Brain
Function?
Plasticity and Change
– The ability of the brain to change is referred to
as plasticity
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Plasticity and Change
• Several factors influence plasticity
– Experience
– Age
– Hormones
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What Effects Do Hormones Have on
Behavior?
• Hormones are chemicals produced by
endocrine glands
– Secreted directly into the bloodstream
– Regulate activities of specific organs or cells
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III. Hormones
Brain
Endocrine
Glands
Behavior
Target
Organs
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Hormones
Endocrine Glands
1. Pituitary Gland known as master gland
2. Gonads
• Produce androgens and estrogens
3. Adrenal Glands
• Produce adrenaline (epinephrine)
4. Pancreas
• Produces insulin
• Diabetes mellitus
• Hypoglycemia
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How Do Genetic Factors Affect
Behavior?
A. The Issue of Nature and Nurture
– Nature refers to biology
– Nurture refers to environment
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How Do Genetic Factors
Affect Behavior?
B. The Basics of Genetics
– Each human cell contains 23 pairs of
chromosomes
• Carry genes
– Genotype – genetic makeup
– Phenotype – physical manifestation
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How Genes Affect Behavior
• Genes affect behavior indirectly
• Behavioral genetics
– The study of the influence of genes on
behavior
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C. How Genes Affect Behavior
•Twin studies
–Fraternal twins
• Dizygotic twins
• Two sperm and two eggs
• No more genetically similar
than non-twin siblings
– Identical Twins
• Monozygotic twins
• One sperm and one
egg split
• Identical genes
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How Genes Affect Behavior
• Twin studies
– Identical twins raised apart share genes, but
not environment
– Fraternal twins raised together share
environment, but not genes
– Allows study of effects of genes and
environment
• Most behaviors are determined by an
interaction between genes and environment
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Does Our Evolutionary Heritage
Influence Current Behavior?
• Evolutionary psychology
– Seeks to explain and predict behavior by
studying the effects of evolution
– Interested in similarities among humans
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Does Our Evolutionary Heritage
Influence Current Behavior?
A. Natural Selection
– Characteristics that help an organism survive
are passed on to future generations
– Facilitates adaptation
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Does Our Evolutionary Heritage
Influence Current Behavior?
B. Adaptations in Humans
– Tendency to protect young from danger
– Complex language
– Jealousy
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Does Our Evolutionary Heritage
Influence Current Behavior?
C. Controversies in Evolutionary Psychology
1. Hypothesized universals
2. Sources of evidence
3. Human nature and determinism
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