The Biological Basis of Behavior

1. The Biological Basis of Behavior Chapter 2

2. Vocabulary Chapter 2 • Neurons • Dendrites • Synapse • Neurotransmitters • Receptor site • Cerebellum • Thalamus • Hypothalamus • Cerebral cortex • Occipital Lobe • Temporal Lobe • Frontal Lobe • Corpus Callosum • Spinal cord • Adrenal glands • Genes

3. Neurons: The Messengers • About 100 billion neurons (nerve cells) in the human brain • Neurons have many of the same features as other cells • Nucleus • Cytoplasm • Cell membrane • What makes neurons unique is their shape and function

4. Structure of Neurons • Dendrites • Carry information to the cell body from other neurons • Cell Body (Soma) • Contains nucleus • Axon • Carries information to the next cell • Myelin Sheath • Insulates the axon and speeds up the neural impulse

5. Types of Neurons • Sensory neurons • Carry information from sensory systems to the brain • Also referred to as afferent • Motor neurons • Carry information from the brain to muscles and glands • Also referred to as efferent • Interneurons • Carry information between other neurons

6. Glial Cells • Cells that insulate and support neurons • Create the myelin sheath • Remove waste products • Provide nourishment • Prevent harmful substances from entering the brain

7. The Neural Impulse

8. The Neural Impulse • Ions • Charged molecules • Resting Potential • When more negative ions are inside the neuron than outside • Charge is approximately -70mV • Neuron is not transmitting information

9. The Neural Impulse • Polarization • When the electrical charge of a cell moves away from zero • Depolarization • When the electrical charge of a cell moves toward zero

10. The Neural Impulse • Action Potential • Sudden, massive change in charge in the neuron • Occurs when depolarization reaches the threshold of excitation • Ions flow across cell membrane

11. The Neural Impulse • Graded Potentials • Subthreshold depolarization • Many subthreshold depolarizations are added together to produce an action potential (a process known as summation)

12. The Neural Impulse • All-or-None Law • A neuron either fires or it does not • When it does fire, it will always produce an impulse of the same strength • Intensity of a stimulus is coded by the frequency of action potentials

13. The Neural Impulse • Absolute refractory period • Period immediately after an action potential when another action potential cannot occur • Relative refractory period • Period following absolute refractory period when a neuron will only respond to a stronger than normal impulse

14. The Synapse • Synaptic space (synaptic cleft) • Tiny gap between neurons • Terminal button • Enlarged area at the end of an axon • The synapse • Composed of the terminal button of one neuron, the synaptic space, and the dendrites or cell body of the receiving neuron

15. Transmission Between Neurons • Synaptic vesicles • Sacs in terminal button that release chemicals into synaptic space • Neurotransmitters • Chemicals released by synaptic vesicles • Receptor sites • Location on receptor neuron for specific neurotransmitter

16. Some Well-Known Neurotransmitters • Acetylcholine (ACh) • Released at the neuromuscular junction • Plays an important role in arousal and attention • Loss of ACh producing cells is linked to Alzheimer’s Disease • Dopamine • Affects neurons associated with voluntary movement • Plays a role in learning, memory, and emotions • Loss of dopamine-producing cells causes symptoms of Parkinson’s Disease

17. Some Well-Known Neurotransmitters • Serotonin • Found throughout the brain • Appears to sets an “emotional tone” • Low serotonin levels are implicated in depression • Endorphins • Reduce pain by inhibiting or “turning down” neurons that transmit pain information

18. Psychopharmacology • Most psychoactive drugs (and toxins) work by blocking or enhancing synaptic transmission • Botulism • Blocks release of ACh at the neuromuscular junction, causing paralysis • “Botox” is botulism toxin used to prevent facial muscles from making wrinkles

19. Psychopharmacology • Curare • Can stun or kill prey quickly • Blocks ACh receptors causing paralysis • Antipsychotic medications • Block dopamine receptors • Reduces schizophrenic hallucinations • Caffeine • Increases the release of excitatory neurotransmitters by blocking the inhibitory neurotransmitter adenosine

20. Psychopharmacology • Cocaine • Prevents reabsorption of dopamine • Leads to heightened arousal of entire nervous system

21. Neural Plasticity • The brain can be changed, both structurally and chemically, by experience • Rat studies show that an “enriched” environment leads to larger neurons with more connections • Has also been shown in humans • Recent research has uncovered evidence of neurogenesis, or the production of new brain cells, in human brains

22. Nervous System Organization • Central nervous system (CNS) • Consists of the brain and spinal cord • Peripheral nervous system • Connects the CNS to the rest of the body • Somatic nervous system • Autonomic nervous system

23. Central Nervous System Brain Spinal Cord Central Nervous System

24. The Brain – The Central Core • Medulla • Controls breathing, heart rate, and blood pressure • Pons • Maintains the sleep-wake cycle • Cerebellum • Coordinates body’s movements

25. The Brain – The Central Core • Thalamus • Relays information from sensory receptors to the brain • Hypothalamus • Influences motivated behavior • Regulates hunger, thirst, body temperature, and sexual drive. • Directly involved in emotional behavior

26. The Brain – The Central Core • Reticular formation • Network of neurons found throughout the brain • Serves to alert and arouse higher brain in response to incoming information

27. The Brain – The Limbic System • Ring of structures located between the central core and the cerebral hemispheres • Important to learning and emotional behavior • Hippocampus essential in formation of new memories • Amygdala, together with the hippocampus, is important for regulating emotions

28. The Cerebral Cortex • Occipital lobe • Receives and processes visual information • Temporal lobe • Complex visual tasks such as face recognition • Receives and processed auditory information • Involved in balance, some emotions and motivations • Some language processing

29. The Cerebral Cortex • Parietal lobe • Receives sensory information from body • Involved in spatial abilities • Frontal lobe • Coordinated information from other lobes • Controls voluntary movement, attention, setting goals, and expression of appropriate emotions

30. Hemispheric Specialization • Corpus Callosum • Fibers that connect the two hemispheres • Allow close communication between left and right hemishphere • Each hemisphere appears to specialize in certain functions

31. Split-Brain Research • Much information about functions of each hemisphere has come from studying split-brain patients

32. Tools for Studying the Nervous System

33. Microelectrode Techniques • Very small electrodes inserted into individual neurons • Used to study activity of a single neuron

34. Macroelectrode Techniques • Used to get a picture of overall activity in the brain • An example is an EEG, which uses electrodes placed on a person’s scalp to measure brain activity

35. Structural Imaging • Computerized Axial Tomography (CT-scan) • Uses X-rays to create a 3-dimensional image of the brain • Magnetic Resonance Imaging (MRI) • Uses a magnetic field and radio waves to produce images

36. Functional Imaging • EEG imaging • electrical activity on the scalp from millions of neurons is used to produce a continuous picture of activity in the brain • Magentoencephalography (MEG) and Magnetic source imaging (MSI) • Can localize activity more precisely than EEG

37. Functional Imaging • Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) • Use radioactive glucose to determine location of greatest brain activity • Functional Magnetic Resonance Imaging (fMRI) • Shows function and structure by measuring movement of blood molecules within the brain

38. The Spinal Cord

39. The Spinal Cord • Complex cable of nerves that connects brain to rest of the body • Carries motor impulses from the brain to internal organs and muscles • Carries sensory information from extremities and internal organs to the brain

40. The Spinal Cord • The spinal cord controls some protective reflex movements without any input from the brain

41. Peripheral Nervous System Somatic Nervous System Autonomic Nervous System Sympathetic Division Parasympathetic Division The Peripheral Nervous System

42. The Somatic Nervous System • Consists of neurons that communicate between the body and the brain • Afferent neurons • Neurons that carry messages from sense organs to spinal cord • Efferent neurons • Neurons that carry messages from the spinal cord or brain to muscles and glands

43. The Autonomic Nervous System • Sympathetic division • Most active when you are angry, afraid, or aroused • Fight-or-flight response • Increases heart rate and breathing • Stops digestion

44. The Autonomic Nervous System • Parasympathetic division • Calms body • Produces effects opposite to those of the sympathetic division • Reduces heart rate and breathing • Restores digestion

45. The Endocrine System

46. The Endocrine System • Helps coordinate and integrate complex psychological reactions • Endocrine glands secrete hormones into the bloodstream • Hormones serve to organize the nervous system and body • Hormones also activate behavior, such as sexual behavior

47. The Endocrine System • Thyroid gland • Secretes hormones (primarily thyroxin) that control metabolism • Parathyroid glands • Control levels of calcium and phosphate which in turn controls levels of excitability

48. The Endocrine System • Pineal gland • Secretes melatonin which regulates the sleep-wake cycle • Pancreas • Regulates blood-sugar levels • Secretes insulin and glucagon

49. The Endocrine System • Pituitary gland • Referred to as the “master gland” because it regulates many other glands • Gonads • Ovaries and testes secrete estrogens and androgens • Adrenal glands • Secretes hormones in reaction to stress

50. Genes, Evolution, and Behavior