Chapter 3

The Biological basis of Behavior8%-10% on the AP EXAM

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Before we start. . .

A website to help you review. It’s COOL! http://www.g2conline.org/

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DID– DENDRITES

SOMEONE– SOMA

ASK– AXON

MY SISTER– MYELIN SHEATH

TO BE– TERMINAL BUTTON

NICE TODAY– NEUROTRANSMITTER

SURE– SYNAPSE

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Communication in the Nervous System

Hardware:– Glia (glue) – structural support and insulation– Neurons – communication– Soma – cell body– Dendrites – receive– Axon – transmit away

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Neural Communication: Insulation and Information Transfer

Myelin sheath – protects & speeds up transmission Terminal Button – end of axon; secretes

neurotransmitters Neurotransmitters – chemical messengers Synapse – point at which neurons interconnect

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The Neural Impulse: Electrochemical Beginnings

Hodgkin & Huxley (1952) - giant squid– Fluids inside and outside neuron – Electrically charged particles (ions)– Neuron at rest – negative charge on inside

compared to outside– -70 millivolts – resting potential

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The Neural Impulse: The Action Potential

Stimulation causes cell membrane to open briefly– Absolute Threshold – minimum amount of

stimulus needed for AP to fire. Positively charged sodium ions flow in, potassium

ions flow out Shift in electrical charge travels along neuron

– The Action Potential

All – or – none law - it fires or it doesn’t Refractory Period – the period of time after the AP

fires in which it cannot fire again until it resets itself.

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The Synapse: Chemicals as Signal Couriers

Synaptic cleft (Synapse) Presynaptic neuron

– Synaptic vesicles– Neurotransmitters

Postsynaptic neuron– Receptor sites

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TWO MINUTE DRILL:

BRIEFLY DEFINE EACH OF THE FOLLOWING TERMS AS THEY RELATE TO A NEURAL IMPULSE– RESTING POTENTIAL– ABSOLUTE THRESHOLD– ALL-OR-NONE LAW– SODIUM– POTASSIUM– ACTION POTENTIAL– REFRATORY PERIOD

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When a Neurotransmitter Binds: The Postsynaptic Potential

Voltage change at receptor site – postsynaptic potential (PSP)– Not all-or-none– Changes the probability of the postsynaptic neuron firing

Positive voltage shift – excitatory PSP Negative voltage shift – inhibitory PSP

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Signals: From Postsynaptic Potentials to Neural Networks

One neuron, signals from thousands of other neurons Requires integration of signals

– PSPs add up, balance out– Balance between IPSPs and EPSPs

Neural networks– Patterns of neural activity– Interconnected neurons that fire together or sequentially

Synaptic connections– Elimination and creation– Synaptic pruning

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Neurotransmitters

Specific neurotransmitters work at specific synapses– Lock and key mechanism

Agonist – mimics neurotransmitter action Antagonist – opposes action of a neurotransmitter

– curare – extracted from vines in South America – extreme muscle relaxant – death by suffocation

15 – 20 neurotransmitters known at present Interactions between neurotransmitter circuits

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Basic Neurotransmitters

Acetylcholine (ACh) Controls skeletal

muscles Contributes to the

regulation of attention, arousal and memory

Some ACh receptors are stimulated by nicotine

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Dopamine (DA)

Contributes to control of voluntary movement, pleasurable emotions

Decreased levels associated with Parkinson’s Disease

Overactive at DA synapses associated with schizophrenia

Cocaine and amphetamines elevate activity at DA synapses

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Norepinephrine (NE) Contributes to

modulation of mood and arousal

Cocaine and amphetamines elevate the activity at NE synapses

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Serotonin Involved in regulation of sleep

and wakefulness, eating and aggression

Abnormal levels may contribute to depression and OCD

Prozac and similar antidepressant drugs affect serotonin circuits

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Gamma-aminobutyic acid

(GABA)

Serves as widely distributed inhibitory transmitter

Valium and similar antianxiety drugs work at GABA synapses

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Endorphins

Resemble opiate drugs in structure and effect

Contribute to pain relief and perhaps to some pleasurable emotions

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Organization of the Nervous System

Central nervous system (CNS) – brain and spinal cord– Afferent (Sensory)= toward the CNS/ Efferent (Motor) =

away from the CNS– SAME – Sensory=Afferent Motor=Efferent

Peripheral nervous system – nerves that lie outside the central nervous system– Somatic nervous system– voluntary muscles and sensory

receptors– Autonomic nervous system (ANS) – controls automatic,

involuntary functions• Sympathetic – Go (fight-or-flight)• Parasympathetic – Stop

Table of ContentsFigure 3.6 Organization of the human nervous system

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The Nervous System

Reflex a simple, automatic, inborn response to a sensory stimulus

Skinreceptors

Muscle

Sensory neuron(incoming information)

Motor neuron(outgoing information)

Brain

Interneuron

Spinal cord

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Studying the Brain: Research Methods

Electroencephalography (EEG) Damage studies/lesioning Electrical stimulation (ESB) Brain imaging –

– (CT) computerized tomography - computer enhanced X-ray

– (PET) positron emission tomography - radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray

– (MRI) magnetic resonance imaging - uses magnetic fields, radio waves, and computer enhancement to image brain structure

– (fMRI)functional magnetic resonance imaging – Real-time MRI

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Schizophrenia

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Bill is suffering from depression and his psychiatrist prescribed Prozac to help him recover. What neurotransmitter will the drug affect?

A. Norepinephrine B. Acetylcholine C. Dopamine D. Serotonin E. GABA C. Serotonin

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Amanda has an excess amount of this neurotransmitter which is associated with her schizophrenia

A. Acetylcholine B. Serotonin C. Dopamine D. Endorphins E. GABA

C.Dopamine

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15. Researchers looking to create a drug to reduce the symptoms of Alzheimer’s disease would most likely focus their efforts on which of the following neurotransmitters? (A) GABA (B) Serotonin (C) Norepinephrine (D) Dopamine (E) Acetylcholine

E. Acetylcholine

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Metabolic activity in different areas of the brain can best be visualized by means of:

(A) magnetic resonance imaging (MRI) (B) computed tomography (CT) (C) positron emission tomography (PET) (D) electroencephalography (EEG) (E) electrical stimulation of the brain (ESB)

C. PET scan

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Which of the following correctly pairs subdivisions within the major divisions of the human nervous system? (A) Somatic . . endocrine and exocrine (B) Central . . somatic and sympathetic (C) Autonomic . . sympathetic and parasympathetic (D) Sympathetic . . parasympathetic and autonomic (E) Peripheral . . central nervous system and the spinal cord C. Autonomic – sympathetic and parasympathetic

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Brain Regions and Functions

Hindbrain – vital functions – medulla, pons, and cerebellum

Midbrain – sensory functions – dopaminergic projections, reticular activating system

Forebrain – emotion, complex thought – thalamus, hypothalamus, limbic system, cerebrum, cerebral cortex

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The Cerebrum: Two Hemispheres, Four Lobes

Cerebral Hemispheres – two specialized halves connected by the corpus collosum

– Left hemisphere – verbal processing: language, speech, reading, writing, math, logical, analytical

– Right hemisphere – nonverbal processing: spatial, musical, visual recognition, intuition, creativity

Four Lobes:– Occipital – vision– Parietal - somatosensory– Temporal - auditory– Frontal – movement, executive control systems

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The Cerebral Cortex

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Prefrontal Cortex

Mirror Neurons frontal lobe neurons that fire when

performing certain actions or when observing another doing so

may enable imitation, language learning, and empathy

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Our Divided Brain

The information highway from the eye to the brain

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Association Areas

More intelligent animals have increased “uncommitted” or association areas of the cortex

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Brain Reorganization

Plasticity the brain’s capacity for modification, as

evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development

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A review

Carl Sagen 11 mins NAT GEO web site for review

Brain Surgery

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The Endocrine System: Glands and Hormones

Hormones – chemical messengers in the bloodstream– Pulsatile release by endocrine glands– Negative feedback system– Hypothalamus – controls the system

Endocrine glands– Pituitary – “master gland,” growth hormone– Thyroid - metabolic rate– Adrenal - salt and carbohydrate metabolism– Pancreas - sugar metabolism– Gonads - sex hormones

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Genes and Behavior: The Interdisciplinary Field of Behavioral Genetics Behavioral genetics = the study of the influence of

genetic factors on behavioral traits Basic terminology: Chromosomes – strands of DNA carrying genetic

information– Human cells contain 46 chromosomes in pairs (sex-cells –

23 single)– Each chromosome – thousands of genes, also in pairs

Dominant, recessive Homozygous, heterozygous Genotype/Phenotype and Polygenic Inheritance

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Research Methods in Behavioral Genetics

Family studies – does it run in the family? Twin studies – compare resemblance of identical

(monozygotic) and fraternal (dizygotic) twins on a trait

Adoption studies – examine resemblance between adopted children and their biological and adoptive parents

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Modern Approaches to the Nature vs. Nurture Debate Molecular Genetics = the study of the

biochemical bases of genetic inheritance– Genetic mapping – locating specific genes - The

Human Genome Project Behavioral Genetics

– The interactionist model– Richard Rose (1995) – “We inherit dispositions, not

destinies.”

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Evolutionary Psychology: Behavior in Terms of Adaptive Significance

Based on Darwin’s ideas of natural selection– Reproductive success key

Adaptations – behavioral as well as physical– Fight-or-flight response– Taste preferences– Parental investment and mating