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The Biological Basis of Behavior

The Biological Basis of Behavior

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The Biological Basis of Behavior

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  1. The Biological Basis of Behavior Chapter 2

  2. Neurons: The Messengers Section 1

  3. What “Language” do Neurons Speak? • The average human brain contains as many as 100 billion nerve cells, or Neurons • Neurons vary widely in size in shape, but they are all specialized to receive and transmit (send) information

  4. Like all cells, they are made up of: • Nucleus : the complete set of chromosomes and genes • Cytoplasm: keeps the cells alive • Cell Membrane: encloses the whole cell • What makes them different? • Dendrites: short fibers that branch out from the cell body and pick up incoming messages • Axon: Single long fiber extending from the cell body; carries outgoing messages to other neurons, muscles or glands • All neurons only have one axon but at the end they branch off into many terminal branches

  5. Nerves: group of axons bundled together like wires • Myelin Sheath: white, fatty covering around the axon Pinched in intervals • Two Functions: • Provides insulation so signals from adjacent neurons so they do not interfere with each other • Increases the speed that a signal is transmitted

  6. Other Neurons • Sensory Neuron: Neurons that collect messages from sense organs and carry them to the spinal cord or the brain • Motor Neurons: Neurons that carry messages from the spinal cord/brain to muscles and glands • Interneurons (Association) Neurons: Carries messages from one neuron to another • The Nervous System also contains numerous Glial Cells or glia • Greek word for glue • Hold the neurons in place, provide nourishment and waste product, prevent harmful substances from passing from the blood stream to the brain, and forms the Myelin Sheath

  7. Neural Impulse • Neurons “speak” with simple electrochemical impulses • When a neuron is at rest and not “speaking” they are in a state of Polarization—the condition of a neuron when the insides is negatively charged outside • A guitar string that has been pulled but not released • To generate a signal the tension needs to be release

  8. Depolarization : when an area of the cell membrane is stimulated enough by messages , pores (channels) allow positively charged ions come in; allowing the inside to be positive • Creates an electrical charge, or a neural impulse, that travels down the axon • When this happens the Neuron has “fired”—sent a signal • This entire process takes only a millisecond

  9. Graded Potential : incoming messages that cause a small, temporary shift in the electrical charge leaving the neuron in its polarized state • For a Neuron to fire, graded potentials must exceed a certain minimum threshold of excitation—level an impulse must exceed to cause a neuron to fire • Each time a neuron fires it is the same strength • Called All-or-Nothing- Law

  10. However, the neuron is more likely to fire more often when stimulated by a strong signal • Absolute Refractory Period: After a neuron fires, for the next thousandth of a second it will not fire again regardless of the strength of the incoming message's • Relative Refractory Period: during the resting state of a cell the neuron will only fire if the incoming message is considerably stronger than normal • Otherwise after a neuron fires it returns to its resting state and waits for the next incoming message

  11. The Synapse • Neurons are not directly connected like a chain, instead there are tiny gaps—called synaptic space • When a neuron fires, an impulse travels down the axon, out though the terminal branches into a tiny swelling that looks like a light bulb • Called Terminal Button or Synaptic Knob • Synapse: area composed of the axon terminal of one neuron, the synaptic space, and the dendrite (cell body) of the next neuron

  12. When the neural impulses reaches the end of the terminals it causes the vesicles to release varying amounts of chemicals called neurotransmitters • Synaptic vesicles: tiny bags in the terminal button that release chemicals into the synapse • Neurotransmitters: chemicals released by the synaptic vesicles that travel across the synaptic space • Neurotransmitters each have a specific matching receptor site on the other side of the synaptic cell • Receptor Site: location on a receptor neurotransmitter; fits like a key into a lock • Once their job is done they detach from the receptor site • Recycled to make new neurotransmitters, or disposed in the body as waste

  13. Neurotransmitters • There are hundreds of neurotransmitters, but their exact function is still unknown • Some Neurotransmitters are: • Acetylcholine: involved in arousal, attention, memory, motivation, and movement. • Can lead to Alzheimer’s disease • Dopamine: variety of behaviors and emotions, including pressure. • Implicated in schizophrenia and Parkinson’s disease • Serotonin: regulates sleep, dreaming, mood, eating, pain, and aggression • Implicated in depression • Endorphins: inhibition of pain, released during strenuous exercise • Responsible for “runner’s high”.

  14. Psychopharmacology • Most psychoactive drugs and toxins work by either blocking or enhancing the transmission of chemicals across synapses • Others do the exact opposite • enhance activity for neurotransmitters • Increasing the release of transmitter • Some substances interfere with the removal of neurotransmitters from the synapse after they have don’t their job so that they can stimulate receptor neurons • Ex: Cocaine—prevents dopamine from being reabsorbed…lead to the excess amounts of dopamine in your system

  15. Neural Plasticity • Neural Plasticity: the ability of the brain to change in response to the experience • Feedback loop—experience lead to changes in the brain, which facilitate new learning…which leads to the brain changing to accept what we newly learned • Ex: Deaf people’s brains have shown changes in the areas responsible for hearing to rewired to read lips and sign language • Studies done in the 1990’s showed that adult brains ere capable of Neurogenesis– growth of new neurons

  16. The Central Nervous System Section 2

  17. Organization of the Nervous system • Every part of the central nervous system is connected to every other part • 2 parts • The central nervous system includes the brain and spinal cord • Contains 90% of the brain’s neurons

  18. The Peripheral Nervous System consists of the nerves that connect the brain and spinal cord to every other part of the body • Carries messages back and forth between the central nervous system and the sense organs, muscles and glands • Subdivided into 2 other parts • Somatic Nervous System: transmits information about the body movements and external environment • Automatic Nervous System: transmits information to and from the internal organs and glands

  19. The Brain • Place where learning. Memory, and emotions are centered • Decided what to do and whether the decision was right or wrong • Imagines how things might have been if we had acted differently • 3 layers of the Brain • Central Core • Limbic System • Cerebral Hemispheres

  20. The Central Core • At the point where the spinal cord enters the skull, it becomes the hindbrain • Earliest part of the brain to evolve

  21. Parts and Functions • Medulla: regulates respiration, heart rate, and blood pressure • Pons: Regulates sleep/wake cycle • Cerebellum: regulates reflexes and balance, and coordinates movement • Thalamus: Major sensory relay center, and regulates the brain centers and the peripheral nervous system • Hypothalamus: Emotions and motivations, and stress reactions

  22. The Limbic System • Ring of structures that play a role in learning and emotional behavior • Parts and functions • Hippocampus: Formation of new memories • Amygdala: Governs emotions related to self preservation

  23. The Cerebral Cortex • Outer surface of the 2 cerebral hemispheres that regulates complex behavior • Processes thought, vision, language, memory, and emotions • What most people think of when we think of the brain • Divided into 2 hemispheres, left and right • Each hemisphere is divided into 4 lobes

  24. Four lobes • Occipital Lobe • Receives and processes visual information • Temporal Lobe • Smell, hearing, balance and equilibrium, emotion and motivation, some language comprehension, and complex visual processing

  25. Frontal Lobe • Goal-directed behavior, concentration, emotional control and temperament, motor projection and association areas, coordinates messages from other lobes, complex problem solving, and involved in many aspects of personality • Primary Motor Cortex: section of the frontal lobe responsible for voluntary movement

  26. Hemispheric Specialization • Humans have a “Right half-brain” and a “Left half- brain” • Corpus Callosum: thick band of nerve fibers connection the left and right cerebral cortex

  27. Language • Left hemisphere • Tow major language areas are Broca’s Area and Wernicke’s area • Wernicke’s Area is in the back of the temporal Lob • Processes and understands what other are saying, and overall listening • Broca’s Area found in the frontal lobe • Essential in our ability to talk

  28. Cognitive and Emotional Style • Left side of the brain dominates the verbal tasks, such as identifying spoken and printed words and speaking • Also operates more analytically, logically, rationally, and sequentially

  29. Right Hemisphere dominates visual and spatial tasks, nonverbal imagery (visual images, music, ad environmental noises), face recognition, and perception and expression of emotion • More involved in solving problem s that require insight or creative solutions

  30. University of Wisconsin- Madison Study • People with more active left frontal lobes then the right front lobes tend to be more cheerful, sociable, and self confident • also respond more positively to events, enjoy being around other people , and don’t get upset or aggravated in unpleasant events • More active Right Frontal Lobes are more easily stressed, frightened, and upset and threatened by unpleasant events around them • They tend to spend more time alone

  31. The Spinal Cord • We talk of the brain and the spinal cord as 2 distinct structures, but in fact, there is no clear boundary between them • At the upper end the spinal cord enlarges into the brain stem

  32. Spinal Cord: complex cable of neurons that runs down the spine, connecting the brain to the most of the rest of the body • Made up of soft, jellylike bundles of long axons, wrapped in insulating myelin and surrounded and protected by vertebral bones

  33. The Peripheral Nervous System Section 3

  34. Somatic Nervous System • Somatic Nervous System: part of the PNS that carries messages from the sense to the CNS and between the CNS and skeletal muscles • All the things that we sense—sights, sounds, smells, temperature, pressure etc. • Voluntary Actions—eating and drinking, reading and writing, etc.

  35. Automatic Nervous System • Automatic Nervous System: part of the PNS that carries messages between the CNS and the internal organs • Consists of 2 branches • Sympathetic • Parasympathetic

  36. Sympathetic Division • Branch of the automatic Nervous System; it prepares the body for quick action in an emergency • In response, your heart pounds, you breath faster, your pupils enlarge, and your digestion stops

  37. Parasympathetic Division • Branch of the automatic nervous system; it calms and relaxes the body

  38. Genes, Evolution, and Behavior Section 5

  39. Genetics • Genetics: the study of how living things pass on traits from one generations to another • Offspring are not carbon copies of their parents, yet some traits reappear from generation to generation in predictable patterns • Genes: elements that control the transmission of traits; they are found on Chromosomes • Chromosomes: pairs of threadlike bodies within the cell nucleus that contains genes

  40. Humans have 23 pairs of chromosomes in every normal cell • The main ingredient of Chromosomes is DNA • DNA is the only known molecule that can replicate itself • The human genome– the total sum of all genes in the human chromosomes—contains more than 100,00 genes

  41. Genes, like chromosomes, occur in pairs • In some cases like eye color, one may be a dominant gene and the other a recessive gene • Dominant: member of the gene pair that controls the appearance of a certain trait • Recessive: member of the gene pair that can control the appearance of a certain trait only if it is paired with another recessive gene

  42. Behavior Genetics • Study topics that interest all psychologists—perceptions, learning, memory, motivation, emotions, personality and psych disorders– but from a genetic perspective • Goal is to determine which genes contribute to intelligence, temperament, talents, and other characteristics

  43. Human Behavior Genetics • Family Studies: studies of heritability in humans based on assumption that if genes influence a certain trait, close relatives should be more similar on their trait than distant relatives • Example: Schizophrenia • Affects 1-2 % general public • Siblings of people with schizophrenia are 8x’s more likely to develop disorder • Children of patients with schizophrenia are 10 x’s more likely to develop disorder

  44. Twin Studies: studies of identical and fraternal twins to determine the relative influence of heredity and environment on human behavior • Ex: nature v. Nurture • Identical Twins: twins that developed from a single fertilized ovum and therefore identical in genetic makeup • Fraternal Twins: twins developed from 2 separate fertilized ova and therefore different in genetic makeup

  45. Adoptions Studies: research carried out on children, adopted at birth by parents not related to them, to determine the relative influence of heredity and environment on human behavior.