Presentation on Nervous system
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The document discusses the nervous system. It describes the two main cell types, neurons and glia, and how neurons are organized into circuits. It explains how electrical signals travel along neurons through changes in membrane potential and the roles of ion channels and myelination in speeding signal conduction. The document also distinguishes between the central and peripheral nervous systems, describing their components and functions, including the sympathetic and parasympathetic divisions of the autonomic nervous system. Finally, it provides an overview of the structure and functions of the vertebrate brain, including areas involved in motor control, emotions, memory, language and consciousness.
Presentation on Nervous system
- 2. Functions of Nervous Systems
- 3. Cells of the Nervous System • • • 1. Neurons • Functionalunit of the NS • Transmitsignalsfrom one locationto another Structure Largest cell body Processesthat conduct signals • • Dendrites Axons
- 4. 2. Glia • Supportingcells • Protect neurons • Insulate neurons • • Providestructure Ex: astrocytes, microglia, ependymalcells, oligodendrocytes, satellite andSchwann cells
- 5. How are neurons organized? • Three types of neurons – – – Sensoryneurons Interneurons Motor neurons • Neural circuitsform from any combination of two or more of these – – – Convergent:(many to one) Divergent: (one to many) Reverberating: (circular) • Simplest: Sensory and motor neurons – reflex arc
- 6. Electrical conduction of information • Membrane potential – Difference of chargesacrossthe plasma membrane • Restingpotential – Restingcellsare (-) insideand(+) outside – Largeamounts of Na+outside the cell andK+inside • Actionpotential/impulse – – – Rapidreversalsin chargesacross the plasma membrane Causedbythe exchangeof ions acrossthe membrane of the neuron Thresholdlevel (-55mV) needed to stimulate neuronsALL-OR- NONEprinciple
- 7. • • • RESTING Na+, K+channels closed + outside, - inside Resting potential maintained DEPOLARIZATION • Actionpotential generated • Na+channelsopen, K+channels close •+ inside, -outside • Risein membrane potential REPOLARIZATION •Na+channels close, K+channels open •- inside, +outside •Drop in membrane potential UNDERSHOOT/ HYPERPOLARIZATION •Na+channelsclose, K+channels remain open longer •more - inside, +outside •further drop inmembrane potential • refractory period of neuron
- 8. Saltatory conduction – a faster way • • • • Depends on myelin sheaths coating an axon Impulses carried from node tonode Advantages – Saveson ATP/energy – Increasesthe speed of conduction Multiple sclerosis– demyelination of axons in the CNS
- 9. Gap junctions and neurotransmitters Communicationbetweenneurons • Gapjunctionsform continuous passagesbetween someneurons • Neurotransmitters crossthe synapse to relay the impulseto another neuronor an effector
- 11. Diversity of nervous systems • Nervecord – thick bundle of nerves from the brain •Ganglion– massof neurons in the PNS
- 12. Vertebrate nervoussystems Evolutionarytrends 2. Increasein overall brain size 3. Compartmentalization of functions 4. Increaseddevelopment of the forebrain
- 13. Vertebrate CNS • • Cephalized Centralized • Integration andprocessingof information • • White matter – axonsin the CNS Graymatter – cellbodies,dendrites, unmyelinated axons • • • Centralcanalof the spinalcord Ventriclesof the brain Cerebrospinalfluid (CSF) • Meninges– protective connective tissue
- 14. Vertebrate PNS • • Transmitsinformation to andfrom the CNS Components – – – – Bothsensoryandmotor functions Paired cranialnerves (12) Paired spinalnerves (31) Ganglia • Motor division – Somaticnervous system • Voluntary- signalsto andfrom skeletal muscles • Respondto external stimuli – Autonomic nervous system • • Involuntary - Internal environment, smoothandcardiac muscles Sympatheticand parasympatheticdivisions
- 15. Actions of the parasympathetic and sympathetic divisions of the ANS • • • • Sympathetic division – Stimulation – Energygeneration Parasympatheti c division – Calming – Restand repair Often have antagonistic actions Cooperateto maintain homeostasis
- 16. Structure and function of the vertebrate brain
- 18. Integrating centers in the cerebrum Right and left cerebral hemispheres • • Cerebral cortex – Highly developed and convoluted in mammals – Lobeswith sensoryareas and association areas, frontal lobe with motor cortex Basalnuclei– planning and learning movement sequences
- 19. Other roles of the cerebral cortex • Languageand speech – – Broca’sarea Wernicke’sarea • Emotions – Limbicsystem– amygdala, hippocampus, andolfactory bulb – Laughing,crying,aggression, feeding, and sexuality • Memory andlearning – – Short-term:frontal lobe Long-term:amygdalaand hippocampus – Neuronsmaymakenew connections • Consciousness – Emergent property based on activity in many areas of the cortex
- 20. Drugs and the Nervous System Effectonthe BodyDrug Effectonthe NS Alcohol (ethanol) CNSdepressant Dependson dosage, FASin babies Stimulants Amphetamines Cocaine Caffeine Nicotine CNSand Symdivision stimulant, more dopamine / adenosine/ norepinephrine / serotonin in the synapse Feelings of happiness and power, reduced fatigue, insomnia, psychosis, hallucinations, violent and aggressive behavior, tremors Depressants Barbiturates CNSdepressant, action potentials cannot be produced Reducerespiration, bp, heart rate, anesthetic Opiates Heroin CNSdepressant, mimics the effects of endorphins, stimulate pleasurecenter Analgesia, sedation, reduced respiration, Hallucinogens /psychedelics Mimics the effects ofserotonin Vivid colors, heightened emotions, increase in heartrate and bp Marijuana Acts on cannabinoid receptors in the brain Altered senseof timeand space, hallucinations