The Nervous System

• The nervous system is the body's information gatherer, storage center and control system. Its overall function is to collect information about the external conditions in relation to the body's external state, to analyze this information, and to initiate appropriate responses to satisfy certain needs. The most powerful of these needs is survival. The nerves do not form one single system, but several which are interrelated. Some of these are physically separate, others are different in function only.

• The brain and spinal cord make up the central nervous system.

• The peripheral nervous system is responsible for the body functions which are not under conscious control - like the heartbeat or the digestive system. The smooth operation of the peripheral nervous system is achieved by dividing it into sympathetic and parasympathetic systems. These are opposing actions and check on each other to provide a balance. The nervous system uses electrical impulses, which travel along the length of the cells. The cell processes information from the sensory nerves and initiates an action within milliseconds. These impulses travel at up to 250 miles per hour, while other systems such as the endocrines may take many hours to respond with hormones.

Organization of the Nervous System

The Autonomic Nervous System

Communication in the Nervous System

Communication in the Nervous System

• Neurons are individual cells in the nervous system that receive, integrate, and transmit information

• Soma or cell body contains the cell nucleus and much of the chemical machinery common to most cells.

• Dendrites are the parts of a neuron that are specialized to receive information.

• Axon transmits signals from the soma to other neurons or to muscles or glands.

• Myelin sheath is the insulating material, derived from glial cells, that encases the axons.

• Terminal buttons are small knobs that secrete chemicals called neurotransmitters.

• Synapse is a junction where information is transmitted from one neuron to another.

Neuron

The Neural Impulse

• The neural impulse is the signal stimulates the neuron to action.– The neuron is surrounded inside and outside by electrically

charged atoms and molecules called ions.– Positively charged sodium and potassium atoms and negatively

charged chloride ions flow back and forth across the cell membrane, but they do not cross at the same rate. The difference in flow rates leads to a slightly higher concentration of negatively charged ions inside the cell.

– The resting potential of a neuron is its stable, negative charge when the cell is inactive.

• The action potential is a very brief shift in a neuron’s electrical charge that travels along the axon.

• The absolute refractory period is the minimum length of time after an action potential during which another actions potential cannot begin.

• Action Potential Images

The Neural Impulse – con’t

•The neural impulse is an all-or-none proposition.

Neurotransmitters

• Acetylcholine is the most abundant neurotransmitter in the body and the primary neurotransmitter between neurons and muscles. The stomach, spleen, bladder, liver, sweat glands, blood vessels, and heart are just some of the organs that this neurotransmitter controls. The body's synthesis of acetylcholine is vital because of the neurotransmitters role in motor behavior and memory. Low levels of acetylcholine can contribute to lack of concentration and forgetfulness and may cause light sleep. Acetylcholine helps control muscle tone, learning, and primitive drives and emotions. It also controls the release of pituitary hormone vasopressin, which is involved in learning and in the regulation of urine output. • Neurotransmission Animated Movie

The Biological Bases of Behavior

Neurotransmitters

Dopamine in an inhibitor, dampening activity so we stay rooted. Dopamine is critical for executing smooth and controlled movements. Lack of dopamine is a cause of Parkinson disease which a person looses the ability to initiate controlled movements. Dopamine moves into frontal lobe regulating flow of information coming in from other areas of the brain. Compromise in the flow of dopamine may cause disrupted or incoherent thought as in schizophrenia. In milder disorders, too much dopamine in the limbic system and not enough in the cortex may produce an overly suspicious personality giving to bouts of paranoia or may inhibit social interaction. A shortage of Dopamine in the frontal lobes may contribute to poor working memory.

Serotonin plays an important role in blood clotting, stimulating a strong heart beat, initiating sleep, fighting depression (prescription drugs that treat depression raise the brain's levels of serotonin) and causing migraine headaches in susceptible individuals (because of its ability to constrict blood vessels or cause them to spasm).

Neurotransmitters – con’t

• Norepinephrine is a hormone produced by the adrenal medulla, similar in chemical and pharmacological properties to epinephrine (also a hormone secreted by the adrenal medulla in response to stimulation of the sympathetic nervous system). Norephinephrine and epinephrine are the two active hormones that cause some of the physiological expressions of fear and anxiety and have been found to be in excess in some anxiety disorders when a disturbance in their metabolism occurs.

• Endorphins mediate pain at receptor sites. In an injury receptors in skin make electrical signals that goes up the spinal cord to the brain. The brain then evaluates pain by releasing pain killers called endorphins which bind at opiate receptor sites of neurons to mediate pain. Endorphins effect the dopamine pathway that feeds into the frontal lobe. These pathways inhibit the flow of dopamine. Vast quantities of endorphins are released and nerves are shut off so more dopamine flows through pathway to get to frontal lobe therefore replacing pain with pleasure

The Hindbrain

The Endocrine System: Glands and Hormones

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

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

Hormones

Lobes of the Brain

The Motor Cortex

The Motor Nerves

Hemispheres

Web Pages on Left-Right Brain

• Split Brain Consciousness • Experiments With Subjects Who Have Had Their Corpus Callosum Severed• Specialization of the Two Hemispheres

Lateralization

The Limbic System

Chromosomes

Chromosome. The microscopic, threadlike part of the cell that carries hereditary information in the form of genes.

Sex Chromosome. Either of a pair of chromosomes that determine whether an individual is male or female. The sex chromosomes of human beings and other mammals are designated by scientists as X and Y.

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

Phenotype and Genotype

Phenotype. This is the "outward, physical manifestation" of the organism. These are the physical parts, the sum of the atoms, molecules, macromolecules, cells, structures, metabolism, energy utilization, tissues, organs, reflexes and behaviors; anything that is part of the observable structure, function or behavior of a living organism.

Genotype. This is the "internally coded, inheritable information" carried by all living organisms. This stored information is used as a "blueprint" or set of instructions for building and maintaining a living creature. These instructions are found within almost all cells (the "internal" part), they are written in a coded language (the genetic code), they are copied at the time of cell division or reproduction and are passed from one generation to the next ("inheritable"). These instructions are intimately involved with all aspects of the life of a cell or an organism. They control everything from the formation of protein macromolecules, to the regulation of metabolism and synthesis.

Genes

• X-Linked Genes. Some genes are X-linked because they are located only on the X chromosome. This suggests that males, who only have one X chromosome are more susceptible to certain inherited disorders than female.

• In regard to the dominant-recessive pattern, a dominant gene may not “penetrate” the phenotype, and result in a mosaic, a mixture of cells, some with and without dominance.

• Genetic imprinting. The tendency of certain genes to be expressed differently when they are inherited from the mothers than when they are inherited from the father.– Evidence that imprinting has occurred comes from examining the pedigree. If

a disorder is always expressed when inherited only from the male or female parent, genomic imprinting should be suspected. It is the sex of the transmitting parent, not the affected offspring that is important. Another clue is discordance among monozygous twins

Dominance and Recessive Genes

Not all pairs of alleles will have the same phenotype: dominance when AA = Aa in phenotype, A is dominant, a is recessive. An allele can be dominant over one allele but recessive to another allele.

Model of dominance from enzyme activity: no copies produce no phenotype, one copy produces x amount of product and two copies produces 2x then the alleles are additive and there is no dominance (intermediate inheritance). If one copy of the allele produces as much product (or has as high a rate of flux) as a homozygote then there is dominance. There are cases where the heterozygote is greater in phenotypic value than either homozygote: called overdominance

X-Linked Recessive Inheritance is marked by individuals who are affected with the trait or condition in question are males. Mothers of the affected males are carriers, and the sisters of affected males may be either heterozygous or not carry the gene at all. The basis for X-linked inheritance is that females have two X chromosomes and males have only one X chromosome.

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