Chapter 35 Biology 2 Notes
Chapter 35 Biology 2 Notes BIOL 1040
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This 5 page Class Notes was uploaded by Courtney Luber on Friday January 22, 2016. The Class Notes belongs to BIOL 1040 at Clemson University taught by Dr. William Surver in Fall 2016. Since its upload, it has received 45 views. For similar materials see General Biology II in Biology at Clemson University.
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Date Created: 01/22/16
Lecture 2: Chapter 35 Neurons and Nervous Systems Review structure of cell membranes Review diffusion and active transport Neuron—functional cells in nervous system o Know structure of the neuron o Cell body—normal cell activities o Dendrites, axon, synapse o Some axons are bare, and some have a sheath o Myelin sheath—enable quick responses o Sometimes have strange looking anatomies Unipolar, bipolar, multipolar, pseudopolar o Glial cells support neurons and maintain the environment of the nervous system Nervous systems have two main anatomical divisions o The central nervous system (CNS) consists of the brain and spinal cord (vertebrates) Decisions are made by nervous system; discriminates between important info and no important info o The peripheral nervous system (PNS) is located outside the CNS and consists of nerves (bundles of neurons wrapped in connective tissue) and ganglia clusters of cell bodies The Nervous System o Obtains sensory info, sensory input o Processes sensory info, integration o Sends commands to effector cells (muscles and glands) that carry out appropriate responses, motor output Sensory neurons o Convey signals from sensory receptors to the CNS Interneurons o Located entirely in the CNS and they integrate info and send it to the motor neurons Motor neurons o Convey signals to effector cells Simple reflex arc o Demonstrates the relationship between neurons and nervous system structure and function Resting potential o In order for a neuron to be stimulated, must be at resting potential Gated channels o When stimulus is applied, these open up and allow sodium to move in o Inside loses its negative charge Threshold response o Minimum amount of stimulation needed to generate action potential Action potential o Threshold o Depolarization o Repolarization o Hyperpolarization Propagation and synapse o The movement of an action potential down the neuron (propagation) o One area of a neuron depolarizes A stimulus o any factor that causes a nerve signal to be generated o Alters the permeability of a portion of the neuron membrane o Allows ions to pass through o Changes the membrane’s voltage A nerve signal, action potential, is o A change in the membrane voltage o From the resting potential o To a maximum level, and o Back to the resting potential Action potentials are o Self-propagated in a one-way chain along a neuron all-or-none events o Threshold versus non-threshold o Frequency of action potentials, but not their strength changes with the strength of the stimulus Myelin sheath o Covers up a part of the axon o This area of membrane cannot be stimulated o Nodes of Ranvier—gaps in myelin coverage along axons Synapse o Relay points between a synaptic terminal of a sending neuron and a receiving cell o Polarizations: Depolarization Repolarization Hyperpolarization o The receiving cell can be: Another neuron An effector cell such as a muscle or endocrine cell Chemical synapses o The ending (presynaptic) cell secretes a chemical signal, a neurotransmitter o The neurotransmitter crosses the synaptic cleft o The neurotransmitter binds to a specific receptor on the surface of the receiving (postsynaptic) cell o Responsible for the determination of if cell moves on or not o Action potential triggers neurotransmitter o Neuron that has decision—postsynaptic neuron o Has action potential—presynaptic neuron o Bonding of neurotransmitter makes the decision o Postsynaptic neuron begins to depolarize if Na channel opens (gains Na) o Postsynaptic neuron begins to hyperpolarize if K channel opens (loses K) Synapse o Some neurotransmitters excite a receiving cell (EPSP) o Some inhibit a receiving cell (IPSP) o A receiving neuron’s membrane may receive excitatory and inhibitory signals from different sending neurons o The summation of excitation and inhabitation determines if a neuron will transit a nerve signal o One the action potential is generated, everything is done and goes through the process o A single neuron can receive both excitatory and inhibitory inputs from multiple neurons, resulting in local membrane depolarization (EPSP input) and hyperpolarization (IPSP input). All these inputs are added together at the axon hillock. If the EPSPs are strong enough to overcome the IPSPs and reach the threshold of excitation, the neuron will fire. Presynaptic/postsynaptic neurons, IPSP, EPSP, polarizations Nervous System Overview o The flow of information in the nervous system relies on synaptic integration; how many neurons are organized in the body o The brain has thousands and thousands of neurons arranged in blocks all receiving either excitatory or inhibitory signals o There are divergent circuits-neurons in one block fan out to form connections with other blocks o There are also convergent circuits-signals from many blocks are relayed to a few blocks Evolutionary Trends o The nervous systems of invertebrates are not as complex as that those of vertebrates; however they are still able to respond to stimuli and carryout some complex behavior o Behavior is controlled by nervous system and hormone system o Trends to look for Whole body response to more local response Cephalization – the formation of a head Specialized functions of sensory, integrating, and responding Radial Symmetry o Radial symmetrical animals have a nervous system arranged in a web-like system of neurons called a nerve net Cephalization and Centralization o Most bilaterally symmetrical animals evolved o Cephalization – the concentration of the nervous system at the head end o Centralization – the presence of a central nervous system distinct from a peripheral/nervous system o Presence of ganglia—aggregates of neurons that receive info & respond The Human Nervous System o CNS—receives and processes info; initiates action o Brain—receives and processes sensory info; initiates responses; stores memories; generates thoughts and emotions o Spinal Cord—conducts signals to and from brain; controls reflex activities o PNS—transmits signals between CNS and the rest of the body o Sensory neurons—carry signals from sensory organs to CNS o Motor neurons—carry signals from CNS; control activities of muscles and glands o Somatic Nervous System—controls voluntary movements; activates skeletal muscles o Autonomic Nervous System—controls involuntary responses; influences organs, glands, and smooth muscles o Sympathetic Division—prepares body for stress or energetic activity; “Fight-or-Flight” responses o Parasympathetic Division—dominates during times of “rest or rumination”; directs maintenance activities Human Peripheral Nervous System o The PNS can be divided into two functional components o Motor system – mostly voluntary o Autonomic nervous system – mostly involuntary o The motor nervous system Carries signals to and from skeletal muscles Mainly respond to external stimuli o The autonomic nervous system Regulates the internal environment Controls smooth and cardiac muscle and organs and glands of the digestive, cardiovascular, excretory, and endocrine systems o The sympathetic and parasympathetic nervous systems often have opposing effects on target organs.
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