THE BIOLOGICAL BASES OF BEHAVIOUR

NERVOUS TISSUE: BASIC HARDWARE
1. The cells in the nervous system fall into two major categories: Glia and Neurons
  1. Neurons are individual cells in the nervous system that receive, integrate, and transmit information
  2. Glia's are cells found throughout the nervous system that provide various types of support for neutrons
2. Soma: (Greek for body) contains the cell nucleus and much of the chemical machinery common to most cells
3. Dendrites: (Greek for tree) are the parts of the neurone that are specialized to receive information
4. Axon: (Greek for axle) is a long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands
5. Myelin sheath is insulting material, derived from glial cells, that encases some axons
6. The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters
7. Synapse: (Greek word for junction) is where information is transmitted from one neurone to another
THE NEURAL IMPULSE
1. The resting potential of a neurone is its stable, negative charge when the cell is inactive
2. When the neurone is stimulated, for an instant its charge is less negative, or even positive creating an action potential
3. Action Potential: very brief shift in the neurones electrical charge that travels along a axon
4. The absolute refectory period is the minimum length of time after an action potential during which another action potential cannot begin
5. Various neurones transmit neural impulses at different speeds.
  1. EXAMPLE: thicker axons transmit neural impulses more rapidly than thinner ones do
THE SYNPSE: WHERE NEURONES MEET
1. Transmissions take place at special junctions, which depend on chemical messengers
2. Sending signals: chemicals as couriers
  1. Synaptic cleft, a gap between the terminal button of one neurone and the cell membrane of another neurone
  2. Signals have to cross the gap to permit neurones to communicate. The neurone that sends a signal across the gap is called the presynaptic neurone
  3. The arrival of an action potential at an axons terminal buttons triggers the release of neurotransmitters (chemicals that transmit information from one neurone to another)
3. Receiving signals: Postsynaptic potentials
  1. They vary in size and they increase or decrease the probability of a neural impulse in the receiving cell in proportion to the amount of change in voltage
4. When a neurotransmitter and a receptor molecule combine, reactions in the cell membrane cause a postsynaptic potential (PSP)
  1. PSP: a voltage change at a receptor site on a postsynaptic cell membrane
5. Two types of messages that can be sent from cell to cell: Excitatory and Inhibitory
  1. Excitatory psp: a positive voltage shift that increases the likelihood that the postsynaptic neurone will fire action potentials
  2. Inhibitory psp: a negative voltage shift that decreases the likelihood that the postsynaptic neurone will fire action potentials
NEUROTRANSMITTERS
1. Acetylcholine: activates motor neurones controlling skeletal muscles
  1. Contributes to the regulation of attention, arousal, and memory
    1. Some ACh receptors stimulated by nicotine
2. Dopamine: contributes to control of voluntary movement, pleasurable emoticons
  1. Decreased levels associated with Parkinson's disease
  2. Overactivity at DA synapses associated with schizophrenia
  3. Cocaine and amphetamines elevate activity at DA synapses
3. Norepinephrine: Contributes to modulation of mood and arousal
  1. Cocaine and amphetamines elevate activity at NA synapses
4. Serotonin: involved in regulation of sleep and wakefulness, eating, aggression
  1. Abnormal levels may contribute to depression and obsessive compulsive disorder
  2. Prozac and similar depressant drugs affect serotonin circuits
5. GABA: serves as widely distributed inhibitory transmitter
  1. Valium and similar anti anxiety drugs work at GABA synapses
6. Endorphines: resemble opiate drugs on structure and effects
  1. Contribute to pain relief and perhaps to some pleasurable emotions
7. Glutamate: an amino acid that has both excitatory and inhibitory effects. It has been implicated in learning and memory
THE NERVOUS SYSTEMS
1. The peripheral nervous system: its made up of all those nerves that lie outside the brain and spinal cord. (It can be divided into the somatic nervous system and the autonomic nervous system)
2. The somatic nervous system: its made up of nerves that connect to voluntary skeletel muscles and to sensory receptors
3. The autonomic nervous systems: Its made up of nerves that connect to the heart, blood vessels, smooth muscles and glands (It can be subdivided into two branches)
  1. The sympathetic branch mobilizes bodes recourses for emergencies
  2. The parasympathetic branch generally conserves bodily recources
4. The central nervous system: consists of the brain and spinal cord
  1. (its bathed in its own special nutritive soup called "the cerebrospinal fluid")
THE BRAIN
1. The hindbrain: it includes the cerebellum and two structures found in the lower part of the brain stem: the medulla and the pons
  1. The medulla which attaches to the spinal cord, is in charge of largely unconscious but vital functions
  2. The pons includes a bridge of fibres that connects the brainstem with the cerebellum
  3. The cerebellum is a large and deeply folded structure located adjacent to the back surface of the brainstem (its critical to the coordination of movement and to the sense of equilibrium, or physical balance)
2. The midbrain: segment of the brainstem that lies between the hindbrain and the forebrain. It contains an area that is concerned with integrating sensory processes
3. The forebrain: largest and most complex region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus,limbic system, and cerebrum
  1. The thalamus: a structure through which all sensory information (except smell) must pass to get to the cerebral cortex
  2. The hypothalamus: a structure that is involved in the regulation of basic biological drives related to survival
  3. The limbic system: involved in the regulation of emotion, memory, and motivation, and recently it has been linked to the tendency of some people to be optimistic in their approach to life
  4. The cerebrum: the brain areas that are responsible for the most complex mental activities, including learning, remembering, thinking, and consciousness itself
BASIC PRINCIPLES OF GENETICS
1. Chromosomes are strands of DNA molecules that carry genetic information
  1. Every cell in humans (except sex cells) contain 46 chromosomes. They operate in 23 pairs, with one chromosome of each pair being contributed by each parent
2. Fertilization create a zygote: a single cell formed by the union of a sperm cell and an egg
3. Genes are DNA segments that serve as they key functional units in heredity transmission
4. A dominant gene one that is expressed when paired genes are different.
5. A recessive gene is one that is masked when paired genes are different
6. Genotype refers to a persons genetic makeup
7. Phenotype refers to the ways in which a persons genotype is manifested in observable characteristics
8. Polygenic traits, or characteristics are influenced by more than one pair of genes
INVESTIGATING HEREDITARY INFLUENCE: RESEARCH METHODS
1. Family studies: researchers assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait
  1. Family studies can indicate whether a trait runs in families
    1. Can also offer useful insights about the possible impact of heredity
2. Twin studies: researchers assess hereditary influence by comparing the resemblance of identical twins and fraternal twins with respect to a trait
  1. Identical twins emerge from on zygote that splits for unknown reasons
    1. Fraternal twins result when two eggs are fertilized simultaneously by different sperm cells, forming two separate zygotes
3. Adoption studies: researchers assess hereditary influence by examining the resemblance between adopted children and both their biological and their adoptive parents
  1. If adopted children reusable their biological parents in a trait, even though they were not raised by them, genetic factors probably influence that trait
  2. If adopted children resemble their adoptive parents, even though they inherited no genes from them, environmental factors probably influence the trait

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	Creado por Whitney Mitsuing hace más de 8 años