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Chapter 3

Chapter 3. The Biological basis of Behavior. Communication in the Nervous System. Hardware: Glia – structural support and insulation Neurons – communication Soma – cell body Dendrites – receive Axon – transmit away. Myelin sheath – speeds up transmission

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Chapter 3

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  1. Chapter 3 The Biological basis of Behavior

  2. Communication in the Nervous System • Hardware: • Glia – structural support and insulation • Neurons – communication • Soma – cell body • Dendrites – receive • Axon – transmit away

  3. Myelin sheath – speeds up transmission • Terminal Button – end of axon; secretes neurotransmitters • Neurotransmitters – chemical messengers • Synapse – point at which neurons interconnect

  4. The Neural Impulse: Electrochemical Beginnings • Hodgkin & Huxley (1952) - giant squid • Fluids inside and outside neuron • Electrically charged particles (ions) • Neuron at rest – negative charge on inside compared to outside • -70 millivolts – resting potential

  5. The Neural Impulse: The Action Potential • Stimulation causes cell membrane to open briefly • Positively charged sodium ions flow in • Shift in electrical charge travels along neuron • The Action Potential • All – or – none law

  6. Neural Impluse

  7. Synaptic cleft • Presynaptic neuron • Synaptic vesicles • Neurotransmitters • Postsynaptic neuron • Receptor sites

  8. When a Neurotransmitter Binds: The Postsynaptic Potential • Voltage change at receptor site – postsynaptic potential (PSP) • Not all-or-none • Changes the probability of the postsynaptic neuron firing • Positive voltage shift – excitatory PSP • Negative voltage shift – inhibitory PSP

  9. Overview of synaptic transmission

  10. Signals: From Postsynaptic Potentials to Neural Networks • One neuron, signals from thousands of other neurons • Requires integration of signals • PSPs add up, balance out • Balance between IPSPs and EPSPs • Neural networks • Patterns of neural activity • Interconnected neurons that fire together or sequentially • Synaptic connections • Elimination and creation • Synaptic pruning – Figure 3.5

  11. Neurotransmitters • Specific neurotransmitters work at specific synapses • Lock and key mechanism • Agonist – mimics neurotransmitter action • Antagonist – opposes action of a neurotransmitter • 15 – 20 neurotransmitters known at present • Interactions between neurotransmitter circuits • Botox – Ach blocker • Dopamine – substantia nigra – Parkinson disease

  12. Organization of the Nervous System • Central nervous system (CNS) – brain and spinal cord • Afferent = toward the CNS/ Efferent = away from the CNS • Peripheral nervous system – nerves that lie outside the central nervous system • Somatic nervous system– voluntary muscles and sensory receptors • Autonomic nervous system (ANS) – controls automatic, involuntary functions • Sympathetic – Go (fight-or-flight) • Parasympathetic – Stop

  13. Figure 3.6 Organization of the human nervous system

  14. Figure 3.7 – Peripheral Nervous System – Somatic and Autonomic

  15. Cranial Nerves

  16. The Cranial Nerves and Their Function • 1 – Olfactory - smell S • 2 – Optic – vision S • 3 – Occulomotor – eye movements, control of pupil and lens, tears MP • 4 – Trochlear - eye movements M • 5 – Trigeminal – facial sensations, chewing SM • 6 – Abducens - eye movements M • 7 – Facial – facial muscles, salivary glands, taste SMP • 8 – Auditory – acoustic branch: audition S verstibular branch: balance S • 9 – Glossopharynegeal – throat muscles, salivary glands, taste SMP • 10 – Vagus – parasympathetic control of internal organs, sensation from internal organs, taste SMP • 11 – Spinal accessory – head and neck muscles M • 12 – Hypoglossal – tongue and neck muscles M S, sensory; M, motor; P, parasympatheic function

  17. Studying the Brain: Research Methods • Electroencephalography (EEG) – F 3.10 • Damage studies/lesioning • Electrical stimulation (ESB) – F 3.11 • Transcortical Magnetic Stimulation (TMS) – F 3.12 • Brain imaging – • computerized tomography – CT – F 3.13 • positron emission tomography - PET – F 3.14 • magnetic resonance imaging – MRI – F 3.15 • functional magnetic resonance imaging – fMRI – F 3.15

  18. Electroencephalography (EEG)

  19. PET scan MRI and fMRI scans

  20. Positron Emission Tomography – PET scan

  21. Magnetic Resonance Imaging - MRI

  22. Functional MRI images showing reduced activation of language areas during a linguistic task in patients with schizophrenia

  23. Functional MRI images

  24. 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

  25. The Cerebrum: Two Hemispheres, Four Lobes • Cerebral Hemispheres – two specialized halves connected by the corpus collosum – • Left hemisphere – verbal processing: language, speech, reading, writing, sequential • Right hemisphere – nonverbal processing: spatial, musical, visual recognition, parallel • Four Lobes: - • Occipital – vision • Parietal – somatosensory – phantom limb – • Temporal - auditory • Frontal – movement, executive control systems – • Primary functions and associated functions • Language – Broca’s and Wernicke’s areas – loss of language – aphasia –

  26. The cerebral cortex in humans

  27. Primary motor cortex with homunculus

  28. Mirror Neurons • An area just forward of the primary motor cortex is where “mirror neurons” were first discovered accidentally in the mid-1990s. • May play a role in the acquisition of new motor skills, • the imitation of others, • the ability to feel empathy for others, • and dysfunctions in mirror neuron circuits may underlie the social deficits seen in autistic disorders.

  29. The Plasticity of the Brain • The brain is more “plastic” or malleable than widely assumed • Aspects of experience can sculpt features of brain structure • Damage to incoming sensory pathways or tissue can lead to neural reorganization • Adult brain can generate new neurons – neurogenesis

  30. Visual input with split-brain – Roger Sperry and others Split-brain research

  31. 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 • Use of steroids

  32. The endocrine system

  33. 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 PolygenicInheritance

  34. 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

  35. Modern Approaches to the Nature 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.”

  36. 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

  37. Parental Investment and Mating Systems - sociobiology • Polygyny – high female, low male – based on a study by Buss (1994) found in 84 % of human cultures • Polyandry – high male, low female – rare but examples have been found for example in the Pahari of Nepal and India, and Tibet and other limited places in the world. The system in Tibet was based on class and land considerations. http://www.case.edu/affil/tibet/booksAndPapers/pahari.html • Monogamy – shared parental investment but not always equal. There are few exclusively monogamous species – 15 % of human cultures (Buss, 1994) • Polygynadry – group parental investment and very rare – in chimpanzees mating is promiscuous for males and females • Incest – universal taboo – increased genetic diversity

  38. – brain asymmetry and speech localization – use of Wadi technique and TMS

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