The Biological Bases of Behavior Chapter 3

Parts of a Neuron Neuron- individual cell in the nervous system that receives, integrates, and transmits information. Soma- (the cell body) contains the cell nucleus and much of the chemical machinery common to most cells. Dendrites- (tree) parts of a neuron that are specialized to receive information. Axon-(axle) a long, thin fiber that transmits signals away from the soma to other neurons or to muscles or glands.

Parts of a Neuron Myelin Sheath-insulated material that encases some axons. It functions to speed up the transmission of signals that move along axons. Terminal Buttons- small knobs that secrete chemicals called neurotransmitters.

Glia Cells Found throughout the nervous system that provides various types of support for neurons. Supply nourishment to neurons, help remove neurons’ waste products, and provide insulation around many axons. Also plays a role in the development of the nervous system in the human embryo.

The Neural Impulse a complex electrochemical reaction The resting potential- stable negative charge when the cell is inactive. The action potential- a very brief shift in the neuron’s electrical charge that travels along an axon. Absolute refractory period- the minimum length of time after an action potential during which another action potential can not begin. All-or-none law- a neuron either fires or doesn’t fire.

Synaptic Transmission Synthesis and storage neurotransmitters in synaptic vesicles. Release of neurotransmitters into the synaptic cleft. Binding of neurotransmitters at receptor sites leads to excitatory and inhibitory PSPs. Inactivation or removal of neurotransmitters or Reuptake of neurotransmitters by presynaptic neuron.

Neurotransmitters Chemical couriers that communicate information between neurons. Fundamental to behavior, play a key role in everything from muscular movements to moods and mental health. Specific neurotransmitters function at specific kinds of synapses.

Neurotransmitters Acetylcholine- released by neurons that control skeletal muscles. Serotonin- involved in the regulation of sleep and arousal and perhaps aggression. Dopamine- contributes to control of voluntary movement. Norepinephrine- contributes to modulation of mood and arousal. Endorphins- play role in pain relief and response to stress.

Organization of the Peripheral Nervous System

Peripheral Nervous System made up of all the nerves that lie outside the brain and spinal cord Somatic Nervous System Made up of nerves that connect to voluntary skeletal muscles and to sensory receptors. Cables that carry information from receptors in the skin, muscles, and joints to the central nervous system and vice versa. Has afferent (inward)and efferent (outward)nerve fibers. Autonomic Nervous System Made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands. A separate system that controls automatic, involuntary, visceral functions that people don’t normally think about (heart rate, digestion, perspiration). Mediates much of the physiological arousal when you experience emotion.

Autonomic Nervous System Sympathetic division- the branch that mobilizes the body’s resources for emergencies. Creates fight-or-flight response. Parasympatheic division- the branch that conserves bodily resources. Activates processes that allow the body to save and store energy.

Studying the Brain: Research Methods Studying brain functions require a working brain. Lesioning-destroying a piece of the brain with electric currents to burn and disable tissue. ESB- sending a weak electric current into the brain structure to stimulate (activate) it. Brain imaging – able to see inside the human brain – computerized tomography – positron emission tomography – magnetic resonance imaging TMS- a technique that permits scientists to temporarily enhance or depress activity in a specific area of the brain.

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 Plasticity of the brain- the anatomical structure and functional organization of the brain is more flexible.

Right Brain/Left Brain: Cerebral Specialization Cerebral Hemispheres – two specialized halves connected by the corpus collosum – Left hemisphere – verbal processing: language, speech, reading, writing – Right hemisphere – nonverbal processing: spatial, musical, visual recognition The corpus collosum is cut to reduce the severity of epileptic seizures.

The Cerebrum Frontal lobes- largest lobe in the human brain. Contains the principal areas that control the movement of muscles. Parietal lobes- includes the area that registers the sense of touch. Temporal lobes- includes the area that is devoted to the auditory process. Occipital lobes- where most visual signals are sent and visual processing begins.

The Endocrine System System consists of glands that secretes hormones into the bloodstream that help control bodily functioning. Governed by the hypothalamus and pituitary gland. Regulates our response to stress. Variations in testosterone levels show weak association with aggression in males and females.

The Endocrine System: Another Way to Communicate Hormones – chemical messengers in the bloodstream Endocrine glands – Pituitary – “master gland,” growth hormone – Thyroid – metabolic rate – Adrenal – salt and carbohydrate metabolism – Pancreas – sugar metabolism – Gonads – sex hormones

Basic Principles of Genetics 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 Polygenic traits- characteristics that are influenced by more than one pair of genes. – 3 to 5 gene pairs are thought to interactively determine skin color.

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

The Evolutionary Bases of Behavior Based on Darwin’s ideas of natural selection – Reproductive success of an individual organism relative to the average reproductive success in the population. Organisms vary in endless ways. Some traits are heritable. Variations in hereditary traits might affect organisms’ survival and reproductive success. Heritable traits that provide a survival or reproductive advantage will become more prevalent over generations.

The Evolutionary Bases of Behavior Adaptations – inherited characteristics sculpted through natural selection because they helped solve a problem of survival or reproduction when they emerged. – Fight-or-flight response – Taste preferences- for fatty substances that were adaptive in an era of hunting and gathering when dietary fat was scarce source. – Parental investment and mating Species’ typical patterns of behavior often reflect evolutionary solutions to adaptive problems. – For example, behavioral strategies that help organisms avoid predators have obvious adaptive value Many behavioral adaptions improve organisms’ chances of reproductive success.