Presentation 16 - Nervous System
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The nervous system is composed of neurons and glial cells. Neurons transmit signals through electrical impulses called action potentials. Communication between neurons occurs at synapses through neurotransmitters. The vertebrate nervous system includes the central nervous system, which processes information, and the peripheral nervous system, which connects to sensory organs and muscles. The brain contains specialized regions that control functions like movement, senses, emotions, and consciousness.
Presentation 16 - Nervous System
- 1. The Nervous System Coordination, Integration, Control
- 2. Key Concepts and Important Terms Nervous systems function in sensory input, integration, and motor output. The nervous system is composed of neurons and supporting cells . Membrane potentials arise from differences in ion concentrations between a cell’s contents and the extracellular fluid. An action potential is an all-or-none change in the membrane potential. Action potentials travel along an axon because they are self-propagating. Chemical or electrical communication between cells occurs at synapses . One neurotransmitter can produce different effects on different types of cells. The symmetry of the nervous system is correlated with body symmetry. Vertebrate nervous systems are highly centralized and cephalized . The vertebrate peripheral nervous system has several components differing in organization and function. The brainstem conducts data and controls automatic activities essential for survival. The cerebellum controls movement and balance. The thalamus and hypothalamus are prominent integrating centers of the forebrain . The cerebrum contains the most sophisticated integrating centers.
- 3. Functions of Nervous Systems
- 4. Cells of the Nervous System Neurons Functional unit of the NS Transmit signals from one location to another Structure Large cell body Processes that conduct signals Dendrites Axons
- 5. 2. Glia Supporting cells Protect neurons Insulate neurons Provide structure Ex: astrocytes, microglia, ependymal cells, oligodendrocytes, satellite and Schwann cells
- 6. The Dendrite Song! (sung to the tune of "Clementine" sent in by Leah B., a graduate student in elementary education at Long Island Univ. Leah gives credit to Bruce Campbell for composing this song.) Use your dendrites, Use your dendrites, To connect throughout your brain. Take in info, analyze it, Grow some n ew ones Unrestrained. Axons send out Neurotransmitters To the dendrites all around Across the synapse Jumps the impulse New ideas can now abound. Stimulation Is what the brain needs To make dendrites stretch and grow. Ne w connections Mak e us smarter In what we think and what we know. Use your dendrites, Use your dendrites, To connect throughout your brain Take in info, analyze it, Grow some new ones Unrestrained.
- 7. How are neurons organized? Three types of neurons Sensory neurons Interneurons Motor neurons Neural circuits form from any combination of two or more of these Convergent : (many to one) Divergent : (one to many) Reverberating : (circular) Simplest: Sensory and motor neurons – refl ex arc
- 8. Quiz 1 (8 pts.) 1. What is the main function of the nervous system? 2. Draw two neurons and label the following parts: axon dendrite cell body myelin sheath synapse 3. Diffentiate between a sensory neuron and a motor neuron in terms of structure and function.
- 9. Electrical conduction of information Membrane potential Difference of charges across the plasma membrane Resting potential Resting cells are (-) inside and (+) outside Large amounts of Na+ outside the cell and K+ inside Action potential/impulse Rapid reversals in charges across the plasma membrane Caused by the exchange of ions across the membrane of the neuron Threshold level (-55mV) needed to stimulate neurons ALL-OR-NONE principle
- 10. RESTING Na + , K + channels closed + outside, - inside Resting potential maintained DEPOLARIZATION Action potential generated Na + channels open, K + channels close + inside, - outside Rise in membrane potential REPOLARIZATION Na + channels close, K + channels open - inside, + outside Drop in membrane potential UNDERSHOOT/ HYPERPOLARIZATION Na + channels close, K + channels remain open longer more - inside, + outside further drop in membrane potential refractory period of neuron
- 11. Saltatory conduction – a faster way Depends on myelin sheaths coating an axon Impulses carried from node to node Advantages Saves on ATP/energy Increases the speed of conduction Multiple sclerosis –demyelination of axons in the CNS
- 12. Gap junctions and neurotransmitters Communication between neurons Gap junctions form continuous passages between some neurons Neurotransmitters cross the synapse to relay the impulse to another neuron or an effector
- 14. Diversity of nervous systems Nerve cord – thick bundle of nerves from the brain Ganglion – mass of neurons in the PNS
- 15. Vertebrate nervous systems Evolutionary trends Increase in overall brain size Compartmentalization of functions Increased development of the forebrain
- 16. Vertebrate CNS Cephalized Centralized Integration and proc essing of information White matter – axon s in the CNS Gray matter – cell bo dies, dendrites, unmyelinated axons Central canal of the spin al cord Ventricles of the brain Cerebrospinal fluid (CSF) Meninges – protective co nnective tissue
- 17. Vertebrate PNS Transmits information to and from the CNS Components Both sensory and motor functions Paired cranial nerves (12) Paired spinal nerves (31) Ganglia Motor division Somatic nervous system Voluntary - signals to and from skeletal muscles Respond to external stimuli Autonomic nervous system Involuntary - Internal environment, smooth and cardiac muscles Sympathetic and parasympathetic divisions
- 18. Actions of the parasympathetic and sympathetic divisions of the ANS Sympathetic division Stimulation Energy generation Parasympathetic division Calming Rest and repair Often have antagonistic actions Cooperate to maintain homeostasis
- 19. Structure and function of the vertebrate brain
- 21. Integrating centers in the cerebrum Right and left cerebral hemispheres Cerebral cortex Highly developed and convoluted in mammals Lobes with sensory areas and association areas, frontal lobe with motor cortex Basal nuclei – planning and learning movement sequences
- 22. Other roles of the cerebral cortex Language and speech Broca’s area Wernicke’s area Emotions Limbic system – a mygdala, hippocampus, and olfactory bulb Laughing, crying, aggression, feeding, and sexuality Memory and learning Short-term: frontal lobe Long-term: amygdala and hippocampus Neurons may make new connections Consciousness Emergent property based on activity in many areas of the cortex
- 23. Drugs and the Nervous System Drug Effect on the NS Effect on the Body Alcohol (ethanol) CNS depressant Depends on dosage, FAS in babies Stimulants Amphetamines Cocaine Caffeine Nicotine CNS and Sym division 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 CNS depressant, action potentials cannot be produced Reduce respiration, bp, heart rate, anesthetic Opiates Heroin CNS depressant, mimics the effects of endorphins, stimulate pleasure center Analgesia, sedation, reduced respiration, Hallucinogens /psychedelics Mimics the effects of serotonin Vivid colors, heightened emotions, increase in heart rate and bp Marijuana Acts on cannabinoid receptors in the brain Altered sense of time and space, hallucinations