1. The Nervous System

2. Objectives To differentiate sensory division from motor division. To learn the two divisions of nervous system. To compare and contrast sympathetic and parasympathetic nervous system. To learn different types of neurons. 3. Basic Functions of the Nervous System 1. Sensation Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors. 2. Integration The parallel processing and interpretation of sensory information to determine the appropriate response 3. Reaction Motor output. The activation of muscles or glands (typically via the release of neurotransmitters (NTs)) 4. Nervous vs. Endocrine System Similarities: They both monitor stimuli and react so as to maintain homeostasis. Differences: The NS is a rapid, fast-acting system whose effects do not always persevere. The ES acts slower (via blood-borne chemical signals called Hormones) and its actions are usually much longer lasting. 5. Organization of the Nervous System 2 big initial divisions: 1. Peripheral Nervous System The nervous system outside of the brain and spinal cord Carry info to and from the brain 2. Central Nervous System The brain + the spinal cord The center of integration and control 6. Peripheral Nervous System Sensory Division Afferent division Conducts impulses from receptors to the CNS Informs the CNS of the state of the body interior and exterior Sensory nerve fibers can be somatic or visceral Motor Division Efferent division Conducts impulses from CNS to effectors (muscles/glands) Motor nerve fibers 7. Peripheral Nervous System 3 kinds of neurons connect CNS to the body sensory motor interneurons Motor - CNS to muscles and organs Sensory - sensory receptors to CNS Interneurons: Connections Within CNS Spinal Cord Brain Nerves 8. Three Types of Neurons 9. Motor Efferent Division Can be divided further: Somatic nervous system VOLUNTARY (generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles Autonomic nervous system INVOLUNTARY (generally) Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands. 10. Assignment Peripheral Nervous System Autonomic - sympathetic - parasympathetic 11. Peripheral Nervous System Skeletal (Somatic) Sympathetic P arasympathetic Autonomic P eripheral Nervous System 12. Autonomic Nervous System Can be divided into: Sympathetic Nervous System Fight or Flight Parasympathetic Nervous System Rest and Digest These 2 systems are antagonistic. Typically, we balance these 2 to keep ourselves in a state of dynamic balance. 13. Autonomic System Control involuntary functions heartbeat blood pressure respiration perspiration Digestion Can be influenced by thought and emotion (Hypothalamus) 14. Parasympathetic Rest and digest system Calms body to conserve and maintain energy Lowers heartbeat, breathing rate, blood pressure 15. Sympathetic Fight or flight response Release adrenaline (epinephrine) and noradrenaline (norepinephrine) Increases heart rate and blood pressure Increases blood flow to skeletal muscles Inhibits digestive functions 16. Nervous Tissue Highly cellular 2 cell types 1. Neurons Functional, signal conducting cells 2. Neuroglia Supporting cells 1. 2. 17. Cells of Nervous System Neurons or nerve cells Receive stimuli and transmit action potentials Organization Cell body or soma Dendrites: Input Axons: Output Neuroglia or glial cells Support and protect neurons 18. Neuroglia Outnumber neurons by about 10 to 1 . 6 types of supporting cells 4 are found in the CNS: 1. Astrocytes Star-shaped, abundant, and versatile Guide the migration of developing neurons Involved in the formation of the blood brain barrier Function in nutrient transfer 19. Neuroglia 2. Oligodendrocytes Produce the myelin sheath which provides the electrical insulation for certain neurons in the CNS 20. Neuroglia of CNS 3. Ependymal Cells Line brain ventricles and spinal cord central canal Help form choroid plexuses that secrete CSF 4. Microglia Specialized macrophages 21. 2 types of glia in the PNS 1. Satellite cells Surround clusters of neuronal cell bodies in the PNS Unknown function 2. Schwann cells Form myelin sheaths around the larger nerve fibers in the PNS. Vital to neuronal regeneration Neuroglia 22. Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Neuron Structure and Myelin Sheath Formation 23. Assignment: Central Nervous System 24. The Central Nervous System is made of the brain and the spinal cord. The Central Nervous System controls everything in the body. 25. White Matter vs. Gray Matter Both the spinal cord and the brain consist of: white matter = bundles of axons each coated with a sheath of myelin gray matter = masses of the cell bodies and dendrites each covered with synapses. In the spinal cord, the white matter is at the surface, the gray matter inside 26. Spinal cord conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain conducts motor information from the brain to our various effectors skeletal muscles cardiac muscle smooth muscle Glands serves as a minor reflex center Spinal Cord Brain 27. Reflex Actions- actions that result from a nerve impulse passing over a reflex arc - predictable response to a stimulus 28. Somatic reflexes of clinical importance 1. Knee jerk reflex- extension of lower leg in response to tapping the patellar tendon with a reflex hammer - lost in some patients with poliomyelitis and other diseases 29. Effects: 1. Stretches the quadriceps muscles 2. Stimulates muscle spindles 3. Inhibits hamstring +knee jerk- provides evidence that sensory and motor connections between muscle and sipnal cord are intact Hypoactive-knee jerk -due to peripheral nerve damage -absent in those with chronic diabetes and neurosyphilis and during coma -hyperactive in polio and stroke patients 30. 2. Ankle jerk reflex-Achilles reflex - extension of foot in response to tapping the Achilles tendon 31. Babinski reflex- extension of great toe in response to stimulation of outer margin of sole of foot - in infants up to 11/2 years old 32. Plantar reflex- plantar flexion of all toes and a slight turning in and flexion of anterior part of foot in response to stimulation of outer edge of sole 33. Corneal reflex- winking in response to touching cornea 34. Abdominal Reflex- drawing in of abdominal wall in response to stroking the side of the abdomen 35. Assignment: Brain Parts of the Brain 36. An organ that controls your emotions, your thoughts, and every movement you make. 37. Parts of the Brain 38. The Meninges From outside in, these are the : -dura mater pressed against the bony surface of the interior of the vertebrae and the cranium -arachnoid -pia mater The region between the arachnoid and pia mater is filled with cerebrospinal fluid (CSF). 39. CSF Flow CSF Produced in the lateral ventricles Absorbed by the arachnoid villi 40. Arachnoid Villi Arachnoid Dura The arachnoid villi are specialized absorbing filters 41. Brain Support Bone Face Attachment Holds CSF and Supports Meninges Meninges Main brain support Suspends, Compartmentalizes, and Coats Cerebrospinal Fluid In a bony container, allows dissipation of sudden shocks (forces) 42. Parts of the Brain 43. Parts of the Brain 44. Parts of the Brain 45. Parts of the Brain 46. Parts of the Brain 47. Parts of the Brain 48. Parts of the Brain 49. Parts of the Brain 50. Parts of the Brain 51. Parts of the Brain 52. Parts of the Brain 53. Assignment: Brain Stem Cerebellum Diencephalon Prosencephalon 54. A. The Brain Stem Functions: Medulla oblongata 1. Performs sensory, motor, reflex actions 2. Contain cardiac, vasomotor, respiratory centers (vital centers) 3. Also contain centers for non-vital reflexes-vomitting, coughing, sneezing, hicuppping, swallowing Injury to medulla is fatal 55. Medulla oblongata Nerve impulses arising here rhythmically stimulate the intercostal muscles and diaphragm making breathing possible. regulate heartbeat regulate the diameter of arterioles thus adjusting blood flow. The neurons controlling breathing have mu () receptors, the receptors to which opiates, like heroin, bind. This accounts for the suppressive effect of opiates on breathing. Destruction of the medulla causes instant death 56. The Brain Stem Functions: b. Midbrain- - smallest region of the brain that acts as a sort of relay station for auditory and visual information -red nucleus and the substantia nigra are involved in the control of body movement -degeneration of neurons in the substantia nigra is associated with Parkinsons disease -ex. Eye movements 57. The Brain Stem Functions: c. Pons- from Latin word meaning bridge - pneumotaxic centers which aid in respiration -deal primarily with sleep, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture -contains the sleep paralysis center of the brain and also plays a role in generating dreams 58. Pons serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum. Nerve impulses coming from the eyes, ears, and touch receptors are sent on the cerebellum. The pons also participates in the reflexes that regulate breathing. 59. Represents 10% of the weight of the brain, but contains as many neurons as all the rest of the brain combined People with damage to their cerebellum are able to contract their muscles, but their motions are jerky and uncoordinated. The cerebellum appears to be a center for motor skills, posture and maintaining equilibrium B. Cerebellum 60. C. Diencephalon-interbrain Thalamus -chief sensory integrating center -All sensory input (except for olfaction) passes through these paired structures -maintenance of consciousness, alertness, recognition of crude sensations of pain -expressions of emotions(associating impulses with feelings of pleasantness/unpleasantness) 61. Hypothalamus - regulator/coordinator of autonomic activities Damage to the hypothalamus is quickly fatal as the normal homeostasis of body temperature, blood chemistry, etc. goes out of control. Posterior lobe of the pituitary. Receives vasopressin (ADH) and oxytocin from the hypothalamus and releases them into the blood. 62. Hypothalamus - regulation of water/body temp levels -feeding and satiety levels 63. D. Prosencephalon- forebrain The human forebrain (prosencephalon) is made up of a pair of large cerebral hemispheres Executive suite of nervous system Convolutions triple its surface area Accounts for 40% of brain mass 64. Assignment: Functions of Cerebral Hemisphere Association Areas General Interpretation Areas Right and Left Hemisphere 65. FUNCTIONS OF CEREBRAL HEMISPHERE 1. Sensory functions a. somatic senses-touch, pressure, temp, proprioception b. special senses-vision, hearing Sensory areas Primary somatosensory cortex Somatosensory association areas Visual areas - sight Auditory areas - hearing Olfactory cortex - smell Gustatory cortex - taste Limbic system 66. 2. Motor functions-movement of limb muscles a. primary motor cortex- damage to this area paralyzes muscles controlled by these areas b. premotor cortex-controls learned motor skills of a repetitive and patterned nature c. Brocas area-present usually in left hemisphere only - directs muscles involved in articulation d. frontal eye field- controls voluntary movement of the eye 67. a. consciousness- state of awareness of ones environment and other beings - depends on excitation of cortical neurons by impulses from reticular activating system b. language- ability to speak/write words and to understand spoken/written words speech centers- frontal, parietal, temporal lobes c. emotions- limbic system and cerebrum -anger, fear, sexual feelings, sorrow etc d. memory- for storing, retrieving information -in temporal, parietal and occipital lobes 3. Integrative function 68. -influences the endocrine system and the autonomic nervous system -highly interconnected with the nucleus accumbens, the brain's pleasure center, which plays a role in sexual arousal and the "high" derived from recreational drugs -responses modulated by dopaminergic projections from the limbic system. -Rats with electrodes implanted into their nucleus accumbens repeatedly pressed a lever activating this region, and did so in preference to eating and drinking, eventually dying of exhaustion 69. 1. ASSOCIATION AREAS-communicate with primary sensory areas and with motor cortex to analyze, recognize and act on sensory inputs 1. pre-frontal area- anterior portion of frontal lobes; most complicated region - involved with intellect, cognition and personality - abstract ideas, judgment, reason, persistence, planning, concern for others and conscience -develops slowly in children -heavily dependent on +/- feedback from social environment -closely-linked to limbic system 70. Tumors of PFC- mental/personality disorders - wide mood swings, loss of attentiveness and inhibitions - person oblivious to social restraints and careless about personal appearance -cure during 1930s 1950s- pre-frontal lobotomy-severs connections to PFC -cure today-psychoactive drugs 71. 2. GENERAL INTERPRETATION AREA- gnostic or knowing -in one area usually left hemisphere -receives inputs from sensory association areas and integrates all incoming signals into a single thought or understanding of the situation - sends this assessment to PFC which adds emotional overtones and decides on appropriate response -injury to gnostic area-one becomes an imbecile bec ones ability to interpret the entire situation is lost 72. 3. LANGUAGE AREAS-occur in both hemispheres Wernickes area-involved in sounding out unfamiliar words Affective language areas=involved in non- verbal, emotional components of language ( tone/lilting of voice) Aprosodia-individual tells you (honestly) he is happy to see you with a flat voice and stony facial expression 73. LATERALIZATION OF CORTICAL FUNCTIONING -split-brain concept -division of labor -Each hemisphere has unique abilities not shared by the other Cerebral dominance- Left- dominant for language, math, logic Right- visual/spatial skills, intuition, emotion and appreciation of art and music - the poetic, creative and insightful side of our nature far better at recognizing faces - right-dominant people are generally left- handed and more often male 74. 90% of individuals with left-cerebral dominance are right-handed. 10%-roles of hemispheres are reversed or they share functions equally Results in cerebral confusion and learning disabilities Ambidexterity-mutuality of brain control Dyslexia-due to lack of cerebral dominance -people reverse order of letters or syllables in words or words in sentences 75. Left hemisphere: Logical, Analytic, Quantitative, Rational and Verbal Right hemisphere: Conceptual, Holistic, Intuitive, Imaginative and Non-Verbal 76. The left brain process information in logical analytical stages 77. Right side The Artistic Brain 78. Are both smiling figures? 79. Problem in recognizing inverted images 80. Are both smiling figures ? 81. Assignment Disorders of the CNS Disorders of the PNS 82. SOME DISORDERS OF THE CNS 1. Hydrocephalus- obstruction in drainage of csf cure- shunt(tube) to drain excess fluid 83. Epilepsy- characterized by seizures - sudden abnormal bursts of neuron activity that result in temporary changes in brain function -strong contractions of jaw muscles -controlled by anticonvulsive drugs which block neurotransmitters in affected areas of brain 84. Multiple sclerosis- nervous tissue is replaced by connective tissue which results in hardened patches everywhere -weakness, uncoordinated movements, strong, jerking movements 85. Alzheimers disease- degenerative disease; plaque formation in synaptic vesicles - char by extreme forgetfulness, mood swings, dementia, fatal, hereditary 86. Adrenoleukodystrophy- corrosion of myelin sheath; sex-linked -sensory-neural disorder;irreparable damage 87. cure-myelin transplant, stem cell technology 88. Cerebrovascular accident( CVA)- results in destruction of neurons of the motor area of cerebrum due to hemorrhage or cessation of blood flow through cerebral blood vessels -oxygen supply is disrupted and neurons die - results in paralysis of opposite side of body where CVA occurred (hemiplegia) 89. Cerebral palsy- permanent damage to motor areas of brain which remains throughout life - char by spastic paralysis; inv contractions of affected muscles -possible causes: a. mechanical trauma to head b. nerve-damaging poisons c. prenatal infections of mother d. reduced oxygen supply to brain due to difficult delivery 90. End Status-----nganga 91. Ion Movements in a Neuron K+ [K+] higher inside cell than outside Attracted to fixed anions inside cell High membrane permeability Flows slowly out of cell Na+ [Na+] higher outside cell than inside Attracted to fixed anions inside cell Low membrane permeability Flows slowly into cell 92. Resting Potentials Resting potential Typical membrane potential for cells Depends on concentration gradients and membrane permeabilities for different ions involved -65 to -85 mV [Na+] and [K+] inside the cell are maintained using Na+/K+ pumps ICF (-)ECF (+) Na/K pump 93. Neuronal Physiology Graded Potentials 94. Electrical Activity of Neurons: Electrical Signals Electrical signals due to changes in membrane permeability and altering flow of charged particles changes in permeability are due to changing the number of open membrane channels -70 mV-30 mV 95. Membrane Proteins Involved in Electrical Signals Non-gated ion channels (leak channels) always open specific for a particular ion Gated Ion channels open only under particular conditions (stimulus) voltage-gated, ligand-gated, stress-gated Ion pumps active (require ATP) maintain ion gradients 96. Changes to voltage-gated sodium and potassium channels during an Action Potential 97. Ionic movements responsible for changes in membrane potential during an action potential 98. Types of Electric Signals: Graded Potentials occur in dendrites / cell body small, localized change in membrane potential change of only a few mV opening of chemically-gated or physically-gated ion channels travels only a short distance (few mm) + + + ++ + - - - - - - - + + + ++ + - - - -70 mV -70 mV -70 mV-55 mV -63 mV -68 mV 99. Types of Electric Signals: Action Potentials begins at the axon hillock, travels down axon brief, rapid reversal of membrane potential Large change (~70-100 mV) Opening of voltage-gated Na+ and K+ channels self-propagating - strength of signal maintained long distance transmission mV 0 -70 100. Types of Electric Signals: Action Potentials triggered membrane depolarization (depolarizing graded potential) "All or none" axon hillock must be depolarized a minimum amount (threshold potential) if depolarized to threshold, AP will occur at maximum strength if threshold not reached, no AP will occur + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 101. Triggering event (graded potential) causes membrane to depolarize slow increase until threshold is reached Action Potential:Depolarization 102. mV 0 -70 +30 threshold voltage-gated Na+ channels open Na+ enters cell further depolarization more channels open further depolarization membrane reverses polarity (+30 mV) K+ channels close [Na+] and [K+] restored by the Na+-K+ pump K+ rushes out of the cell membrane potential restored Na+ channels close Delayed opening of voltage-gated K+ channels Action Potential: Repolarization 103. Action Potential Propagation: Myelinated Axons myelin - lipid insulator membranes of certain glial cells Nodes of Ranvier contain lots of Na+ channels Saltatory conduction signals jump from one node to the next AP conduction speed 50-100x Vertebrates tend to have more myelinated axons than invertebrates 104. Chemical Synapses Many voltage-gated Ca2+ channels in the terminal bouton AP in knob opens Ca2+ channels Ca2+ rushes in. Ca2+ induced exocytosis of synaptic vesicles Transmitter diffuses across synaptic cleft and binds to receptors on subsynaptic membrane Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Calmodulin Protein Kinase C Synapsins + + + + + + + + -- -- -- -- 105. Positive-feedback cycle 106. Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Synapse Events 107. Drug Addiction When a cell is exposed to a chemical signal for a prolonged period, it tends to lose ability to respond with its original intensity. If receptor proteins within synapses are exposed to high levels of neurotransmitter molecules for prolonged periods, the nerve cell often responds by inserting fewer receptor proteins into the membrane. 108. Drug Addiction Cocaine Neuromodulator (prolongs transmission of signal across synapse) that causes large amounts of neurotransmitters to remain in synapses for long periods of time. Transmit pleasure messages using the neurotransmitter dopamine. Nerve cells may eventually lower the number of receptor proteins on surface. 109. Copyright McGraw-Hill Companies Permission required for reproduction or display