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Chapter 3: The Biological Bases of

Behavior

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Communication in the Nervous System

• Hardware:1) Glia: structural support and insulation (Glue) 2) Neurons: communication (receives, integrate & transmits)

Dendrites – receive message

Soma – cell body

Axon – transmit message

Myelin sheath- speeds up transmission

Terminal Button- end of axon, release message

Synapse- gap between Button & Dendrite

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Structure of the Neuron

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The Neural Impulse

1) Resting Potential- Neuron is Ready› -70 millivolts

2) Action Potential- Neuron Fires (down axon)› Sodium + ions flow in, Potassium - ions flow out

3) Refractory Period- Neuron is Recharging› The minimum time after firing, cannot fire until charged

All or None Principle- Neuron fires at the same speed whether it was strong or weak. Either fires or doesn't.

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The Neural Impulse

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The Synapse: Chemicals as Signal Couriers

• Neurotransmitters: is the chemical message that transmit info from one neuron to another.– Presynaptic neuron (Terminal Button)

• Synaptic vesicles: Contain Neurotransmitters

– Postsynaptic neuron (Dendrites)• Receptor sites: Located on dendrites, each receptor

site receive specific neurotransmitters

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When a Neurotransmitter Binds:The Postsynaptic Potential

Postsynaptic Potential (PSP)Changes the probability of the postsynaptic neuron firing

– Excitatory PSP: Positive voltage shift, increase firing

– Inhibitory PSP: Negative voltage shift, decrease firing

• Reuptake: All the excess neurotransmitters that don’t bind to a receptor site get sucked up into the terminal button

• Synaptic connections– Elimination and creation– Synaptic pruning

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Overview of Synaptic Transmission

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Synaptic Pruning

Types of Neurons

• Sensory Neurons– Nerves that carry information to the central

nervous system Connect the sense organs to the brain and spinal cord

• Motor Neurons– Nerves that carry information from the central nervous

system Carries messages from the brain and spinal cord to other parts of your body

• Inter Neurons– Nerve cells in the brain and spinal cord responsible for

processing information related to sensory input and motor output 11

The Neural Chain

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Neurotransmitters

Specific neurotransmitters work at specific synapses– Lock and key mechanism– (15 – 20) neurotransmitters known at present• Agonist – mimics neurotransmitter action• Antagonist – opposes action of a

neurotransmitter

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Common Neurotransmitters and Some of their Functions

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Neurotransmitter Helpful Hints

• ACh- AAMM• DA- Sell Dope at the Park (Parkinson)

Movement & Pleasure

• NE- Norma PMS (Mood & Arousal)

• Serotonin- Sleep/Wakefulness, Eating/Aggression (Ninja Turtles, SEWA)

• GABA- Inhibitor

• Endorphins- Natural pain reliever

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Organization of the Nervous System

• Central nervous system (CNS)Brain & Spine (It is the center)

– Hindbrain. Back bottom– Midbrain. Core– Forebrain. Outer

• Peripheral nervous system (PNS)Bones. Organs. Muscles. (Is everything else)

– Somatic nervous system (SNS) voluntary• Afferent = (In) toward the CNS• Efferent = (Out) away from the CNS

– Autonomic nervous system (ANS) automatic• Sympathetic (Fight or Flight)• Parasympathetic (Calming)

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Organization of the NS

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The CNS & PNS

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The Autonomic Nervous System (ANS)

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Studying the Brain: Research Methods

• Electroencephalography (EEG). Brain Waves • Damage studies/lesioning • Electrical stimulation (ESB). Mapping out the Brain

• Brain Imaging – – CT Scan (computerized tomography). X-Ray of brain structure – PET Scan (positron emission tomography). Brain function,

shows activity in the brain with radioactive glucose. – MRI Scan (magnetic resonance imaging). 3D pictures

– fMRI Scan (functional magnetic resonance imaging). Additional oxygen & blood flow. Structure & function

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Accidents

Phineas Gage Story• Personality changed

after the accident.

What this this tell us?• That different part of

the brain control different aspects of who we are.

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Lesions

• Purposeful removal or destruction of some part of the brain.

• Frontal Lobotomy

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Brain Regions & Functions• Hindbrain:

– Medulla. vital functions – Pons. facial expression, sleep & dreaming– Cerebellum. movement & balance

• Midbrain: (Plug into hard drive)

– Reticular Formation. sensory functions • Forebrain:

– Basal ganglia. Regulates muscle contraction/movements– Thalamus. All senses except smell– Hypothalamus. 4 “F’s”– Limbic system

• Hippocampus. Learning & Memory (Hip to the campus)• Amygdala. Emotion (Amy is emotional)

– Cerebrum. Outer layer of brain (largest) is covered by…– Cerebral cortex. Wrinkles in the outer layer 1.5 sqf (gray

matter)

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The Cerebrum:Two Hemispheres, Four Lobes

• Cerebral Hemispheres – two specialized halves connected by the corpus callosum

• Contralateral Control- each hemisphere controls opposite sides of the body– Corpus Collosum- connects the hemispheres

• Lateralization- left & right hemispheres have different functions– Left hemisphere – verbal processing: language, speech,

reading, writing– Right hemisphere – nonverbal processing: spatial,

musical, visual recognition

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The Cerebrum:Two Hemispheres, Four Lobes

• Four Lobes:– Occipital – vision– Parietal – somatosensory/motor cortex– Temporal - auditory– Frontal – movement, executive control

systems

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Structures & areas in the human brain

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Brain Reorganization

• Corpus Callosum neural fiber connecting the 2 brain hemispheres & carrying messages between the hemispheres.

• Split Brain was used to cure epilepsy by cutting the corpus callosum.

• Brain Plasticity is the brain’s capacity to overcompensate for a loss of a brain function. Higher in children.

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The Cerebral Hemispheres & The Corpus Callosum

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Spilt Brain

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The Cerebral Cortex in Humans

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The Primary Motor Cortex

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Language processing in the brain

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The Endocrine System: Hormones

Hormones – Chemical messengers produced by the endocrine glands and circulated in the blood

Similar to neurotransmitters in that they are also messengers

Slower communication system, but with longer lasting effects

The Endocrine System: Glands• Endocrine glands

– Pituitary – “master gland,” growth hormone– Thyroid – helps regulate the energy level in

the body metabolic rate– Adrenal – help to arouse the body in times of

stress, Located above the kidneys, Release epinephrine (adrenaline) and norepinephrine

– Pancreas – regulates the level of sugar in the blood

– Gonads – sex hormones, Ovaries (females) and testes (males) influence emotion and physical development. 34

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Genes & Behavior:The Field of Behavioral Genetics• Behavioral genetics = the study of the

influence of genetic factors on behavioral traits• Chromosomes – strands of DNA carrying

genetic information– Human cells contain 46 chromosomes in pairs

(sex-cells – 23 single)– Each chromosome – thousands of genes, in pairs

• Dominant, recessive/Homozygous, heterozygous

• Genotype- Genetic makeup• Phenotype- manifested in characteristics • Polygenic Inheritance- characteristics

influenced by more than one gene

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Genetic Material

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Research Methods in Behavioral Genetics

• Family studies – does it run in the family?

• Twin studies – compare resemblance of identical and fraternal twins on a trait

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

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Genetic Relatedness

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Family studies of risk for Schizophrenic Disorders

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Twin studies of Intelligence &Personality

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Modern Approaches to theNature 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