1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chapter 28 Nervous System

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Can an Injured Spinal Cord Be Fixed? Injuries to the spinal cord –Disrupt communication between the central nervous system (brain and spinal cord) and the rest of the body Spinal cord

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The late actor Christopher Reeve –Suffered a spinal cord injury during an equestrian competition –Was an influential advocate for spinal cord research

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings NERVOUS SYSTEM STRUCTURE AND FUNCTION 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands Nervous systems –Are the most intricately organized data- processing systems on Earth

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The nervous system obtains and processes sensory information –And sends commands to effector cells, such as muscles, that carry out appropriate responses Sensory input Sensory receptor Effector cells Motor output Integration Peripheral nervous system (PNS) Brain and spinal cord Central nervous system (CNS) Figure 28.1A

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sensory neurons –Conduct signals from sensory receptors to the central nervous system (CNS) The CNS –Consists of the brain and spinal cord

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interneurons in the CNS –Integrate information and send it to motor neurons Motor neurons –Convey signals to effector cells

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Quadriceps muscles Flexor muscles Brain Spinal cord Nerve PNS Ganglion CNS Automatic responses called reflexes –Provide an example of nervous system function Interneuron 4 Sensory neuron 2 Motor neuron 3 1 Sensory receptor Figure 28.1B

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Located outside the CNS, the peripheral nervous system (PNS) –Consists of nerves (bundles of fibers of sensory and motor neurons) and ganglia (clusters of cell bodies of the neurons)

10. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.2 Neurons are the functional units of nervous systems Neurons –Are cells specialized for carrying signals

11. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A neuron consists of –A cell body –Two types of extensions (fibers) that conduct signals, dendrites and axons Schwann cell Signal direction Dendrites Cell body Nucleus Axon Schwann cell Signal pathway Myelin sheath Nodes of Ranvier Node of Ranvier Layers of myelin in sheath Nucleus Synaptic terminals Cell body SEM 3,600  Figure 28.2

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Many axons are enclosed by cellular insulation called the myelin sheath –Which speeds up signal transmission

13. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings NERVE SIGNALS AND THEIR TRANSMISSION 28.3 A neuron maintains a membrane potential across its membrane At rest, a neuron’s plasma membrane –Has an electrical voltage called the resting potential Voltmeter Plasma membrane Microelectrode outside cell – 70 mV Axon Neuron Microelectrode inside cell + + + + + + + + – – – – – – – – + + + + + + + + Figure 28.3A

14. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The resting potential –Is caused by the membrane’s ability to maintain a positive charge on its outer surface opposing a negative charge on its inner surface Outside of cell Na + K+K+ K+K+ K+K+ Protein Na + Plasma membrane K + channel K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ Na + - K + pump Na + K+K+ channel Inside of cell Figure 28.3B

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.4 A nerve signal begins as a change in the membrane potential A stimulus alters the permeability of a portion of the membrane –Allowing ions to pass through and changing the membrane’s voltage

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A nerve signal, called an action potential –Is a change in the membrane voltage from the resting potential to a maximum level and back to the resting potential 3 2 1 4 5 1 Na + + + + + + + + – – + + – – – + + + + + + + Additional Na + channels open, K + channels are closed; interior of cell becomes more positive. A stimulus opens some Na + channels; if threshold is reached, action potential is triggered. Resting state: voltage-gated Na + and K + channels closed; resting potential is maintained. Na + channels close and inactivate. K + channels open, and K + rushes out; interior of cell more negative than outside. The K + channels close relatively slowly, causing a brief undershoot. Return to resting state. Na + + + + + + + + – – + – – – – + + + + + + + + + + + – – – – – – – – + + + + + + + + + + + – – – – – – – + + + + + + + + + + + – – – – – – – – + + + + Neuron interior Neuron interior Action potential Resting potential Threshold +50 0 – 50 – 100 Time (msec) K+K+ K+K+ Membrane potential (mV) 3 1 2 4 5 1 Na + Figure 28.4

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.5 The action potential propagates itself along the neuron Action potentials –Are self-propagated in a one-way chain reaction along a neuron –Are all-or-none events

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Axon Action potential Axon segment                                     Na  KK KK KK KK Propagation of the action potential along an axon 1 2 3 Figure 28.5

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The frequency of action potentials, but not their strength –Changes with the strength of the stimulus

20. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.6 Neurons communicate at synapses The transmission of signals between neurons –Or between neurons and effector cells occurs at junctions called synapses

21. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Electrical signals –Pass between cells at electrical synapses

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings At chemical synapses –The sending cell secretes a chemical signal, a neurotransmitter The neurotransmitter –Crosses the synaptic cleft and binds to a receptor on the surface of the receiving cell

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sending neuron Axon of sending neuron Receiving neuron Synaptic cleft Receiving neuron Synaptic terminal Neurotransmitter molecules Vesicles Ion channels Neurotransmitter broken down and released Ions Neurotransmitter Receptor Synapse Neuron communication Vesicle fuses with plasma membrane 2 3 Neurotransmitter is released into synaptic cleft 4 Neurotransmitter binds to receptor 1 Action potential arrives 5 Ion channel opens 6 Ion channel closes Figure 28.6

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.7 Chemical synapses make complex information processing possible A neuron may receive information –From hundreds of other neurons via thousands of synaptic terminals Dendrites Myelin sheath Axon Synaptic terminals Inhibitory Receiving cell body Excitatory Synaptic terminals SEM 5,500  Figure 28.7

25. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Some neurotransmitters –Excite the receiving cell Other types of neurotransmitters –Inhibit the receiving cell’s activity by decreasing its ability to develop action potentials

26. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The summation of excitation and inhibition –Determines whether or not a neuron will transmit a nerve signal

27. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.8 A variety of small molecules function as neurotransmitters Many small, nitrogen-containing molecules –Serve as neurotransmitters

28. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 28.9 Many drugs act at chemical synapses Many psychoactive drugs –Act at synapses and affect neurotransmitter action Figure 28.9

29. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings AN OVERVIEW OF ANIMAL NERVOUS SYSTEMS 28.10 Nervous system organization usually correlates with body symmetry Radially symmetrical animals –Have a nervous system arranged in a weblike system of neurons called a nerve net Nerve net Neuron A Hydra (cnidarian) Figure 28.10A

30. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Most bilaterally symmetrical animals exhibit –Cephalization, the concentration of the nervous system in the head region –Centralization, the presence of a central nervous system B Flatworm (planarian) Eyespot Brain Nerve cord Tranverse nerve E Squid (mollusc) Brain Giant axon Brain Ventral nerve cord Segmental ganglion C Leech (annelid) Brain Ventral nerve cord Ganglia D Insect (arthropod) Figure 28.10B–E

31. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.11 Vertebrate nervous systems are highly centralized and cephalized Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Cranial nerves Ganglia outside CNS Spinal nerves Figure 28.11A

32. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The brain and spinal cord –Contain fluid-filled spaces Brain Cerebrospinal fluid Meninges White matter Gray matterDorsal root ganglion (part of PNS) Spinal nerve (part of PNS) Central canal Spinal cord (cross section) Ventricles Central canal of spinal cord Spinal cord Figure 28.11B

33. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cranial and spinal nerves –Make up the peripheral nervous system

34. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.12 The peripheral nervous system of vertebrates is a functional hierarchy The PNS can be divided into two functional components –The somatic nervous system and the autonomic nervous system Peripheral nervous system Somatic nervous system Autonomic nervous system Sympathetic division Parasympathetic division Enteric division Figure 28.12

35. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The somatic nervous system –Carries signals to and from skeletal muscles, mainly in response to external stimuli The autonomic nervous system –Regulates the internal environment by controlling smooth and cardiac muscles and the organs of various body systems

36. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.13 Opposing actions of sympathetic and parasympathetic neurons regulate the internal environment The parasympathetic division of the autonomic nervous system –Primes the body for activities that gain and conserve energy for the body The sympathetic division of the autonomic nervous system –Prepares the body for intense, energy- consuming activities

37. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The autonomic nervous system Parasympathetic divisionSympathetic division Eye Salivary glands Lung Liver Heart Adrenal gland Pancreas Stomach Intestines Bladder Genitalia Spinal cord Brain Constricts pupil Stimulates saliva production Constricts bronchi Slows heart Stimulates stomach, pancreas, and intestines Stimulates urination Promotes erection of genitals Promotes ejaculation and vaginal contractions Inhibits urination Inhibits stomach, pancreas, and intestines Stimulates glucose release Stimulates epinephrine and norepinep- hrine release Accelerates heart Dilates bronchi Inhibits saliva production Dilates pupil Figure 28.13

38. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.14 The vertebrate brain develops from three anterior bulges of the neural tube The vertebrate brain –Develops from the forebrain, midbrain, and hindbrain Embryonic Brain Regions Brain Structures Present in Adult Forebrain Midbrain Hindbrain MidbrainHindbrain Forebrain Embryo (one month old) Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain (part of brainstem) Pons (part of brainstem), cerebellum Medulla oblongata (part of brainstem) Cerebral hemisphere Diencephalon Midbrain Pons Cerebellum Medulla oblongata Spinal cord Fetus (three months old) Figure 28.14

39. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The size and complexity of the cerebrum in birds and mammals –Correlates with their sophisticated behavior

40. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings THE HUMAN BRAIN 28.15 The structure of a living supercomputer: The human brain The human brain –Is more powerful than the most sophisticated computer

41. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The human brain is composed of three main parts –The forebrain, the midbrain, and the hindbrain Forebrain Midbrain Hindbrain Cerebrum Thalamus Hypothalamus Pituitary gland Pons Medulla oblongata Cerebellum Spinal cord Cerebral cortex Figure 28.15A

42. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Major structures of the human brain Table 28.15

43. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The midbrain and subdivisions of the hindbrain, together with the thalamus and hypothalamus –Function mainly in conducting information to and from higher brain centers –Regulate homeostatic functions, keep track of body position, and sort sensory information

44. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The forebrain’s cerebrum –Is the largest and most complex part of the brain

45. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Most of the cerebrum’s integrative power –Resides in the cerebral cortex of the two cerebral hemispheres Left cerebral hemisphere Right cerebral hemisphere Corpus callosum Basal ganglia Figure 28.15B

46. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.16 The cerebral cortex is a mosaic of specialized, interactive regions Specialized integrative regions of the cerebral cortex include –The somatosensory cortex and centers for vision, hearing, taste, and smell Frontal lobeParietal lobe Occipital lobeTemporal lobe Frontal association area Motor cortex Somatosensory cortex Somatosensory association area Speech Taste Reading Hearing Smell Auditory association area Visual association area Vision Speech Figure 28.16

47. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The motor cortex –Directs responses Association areas –Concerned with higher mental activities such as reasoning and language, make up most of the cerebrum The right and left cerebral hemispheres –Tend to specialize in different mental tasks

48. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 28.17 Injuries and brain operations provide insight into brain function Brain injuries and surgeries –Have been used to study brain function Figure 28.17A, B

49. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.18 Several parts of the brain regulate sleep and arousal Sleep and arousal involve –Activity by the hypothalamus, medulla oblongata, pons, and neurons of the reticular formation

50. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The reticular formation –Receives data from sensory receptors and sends useful data to the cerebral cortex Eye Reticular formation Input from touch, pain, and temperature receptors Input from ears Data to cerebral cortex Figure 28.18A

51. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings An EEG –Measures brain waves during sleep and arousal Awake but quiet (alpha waves) Awake during intense mental activity (beta waves) Asleep Delta waves REM sleepDelta waves Figure 28.18B, C

52. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 28.19 The limbic system is involved in emotions, memory, and learning The limbic system –Is a functional group of integrating centers in the cerebral cortex, thalamus, and hypothalamus –Is involved in emotions, memory, and learning Smell Olfactory bulb Amygdala Hippocampus Cerebrum Thalamus Hypothalamus Prefrontal cortex Figure 28.19

53. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 20.20 Changes in brain physiology can produce neurological disorders

54. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Schizophrenia Schizophrenia is a severe mental disturbance –Characterized by psychotic episodes in which patients lose the ability to distinguish reality

55. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Depression Two broad forms of depressive illness have been identified –Major depression and bipolar disorder

56. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Selective serotonin reuptake inhibitors (SSRIs) –Are prescribed to treat depression 140 120 100 80 60 40 20 0 199519961997199819992000200120022003 Year Prescriptions (millions) Figure 28.20A

57. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Alzheimer’s Disease Alzheimer’s disease (AD) –Is characterized by confusion, memory loss, and a variety of other symptoms Senile plaqueNeurofibrillary tangle LM 250  Figure 28.20B

58. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Parkinson’s Disease Parkinson’s disease is a motor disorder –Characterized by difficulty in initiating movements, slowness of movement, and rigidity Figure 28.20C