PSYCH 112 1st Edition Lecture 4 Why Neurons?I. Response system is characterized by two non-linear relationshipsa. Energy: a response may involve more energy than in communicated to the organism by the eliciting stimuli.b. Signal Strength: the signal from even a small number of receptors can activate a large number of muscles. II. Cellsa. Cells of the circulatory system carry oxygen and kill intruding organismsb. Central Nervous system has two types of cellsi. Glia: provides neurons with insulation, structure, protection, nutrition, and repair. Most common type is Oligodendrocytes, astrocytes, microglia.Mainly used to clean up after dead/dying neurons ii. Neurons: make the nervous system work and they process information and communicate it. They carry our summation and inhibition signals. 1. Resting potential: neuron maintains slight negative charge across the cell membrane2. Action Potential: neuron generates signal, sends down axon, recovers, and then returns to resting state.3. Activation Threshold: charge at which the neuron switches from its resting to its active state. iii. Basic function of neurons: 1. Summation of signals from other neurons or sense receptors and if they exceed the activation threshold2. Dispatch of a signal to other neurons or to muscle fibers c. Axon: longest of cell processes ends in terminal buttons that secrete neurotransmitters(detecting signal chemical) III. Excitation and Inhibitiona. Synapse: communicative connection between two neuronsb. Inhibitory connections nudge neurons away from its activation thresholdc. Summation: adding up all incoming signals of excitation and inhibition d. Special Summation: to sum up simultaneous inputs from different locations (overtime which is temporal summation.IV. All or None Principlea. If the neuron receives enough stimulation to switch into active state, it will at full power. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. No strong or weak action potential , it occurs or doesn’t c. Autonomic Nervous System: part of nervous system that controls our internal organs d. Sympathetic nervous system: signals our organs to increase or decrease their rateof operatione. Parasympathetic nervous system: signals our organs to relax and resume their normal rate of operation V. Hodgkin-Huxley Model (Ion exchange model): features of how action potential worksa. Regards transmission of an action potential down an axon as the conduction of a positive electrical charge on the order of 50 millivoltsb. At resting state, a neuron pumps in negative ions and pumps out positive ionsc. Refractory Period: positive ions are pumped out and negatives pumped in so thatthe neuron is prepared to conduct the next action potentiald. Two consequences of periodi. Neuron can signal only periodicallyii. There is a limit to the maximum frequency of a neurons signale. Alternation between positive and negative state is essential to the functioning of the nervous system f. Active Conduction: axon actively recharges action potential g. Myelin Sheath speeds up the action potential by smoothening the recharging process, but gets recharged less frequently when traveling down the axon VI. The Solution Model: during an action potential, there is also a ripple a. Soliton: mathematical model of a kind of pressure wave b. A ripple of liquid gel is created from lipid molecules because of a pressure wave VII. Communication between Neuronsa. Synaptic Gap: tiny space between the end of one neuron and the beginning of another caused by action potential reaching terminal buttons at the end of the axon b. Neurotransmitter: molecules of chemicals that communicate that an action potential has occurred to the next neuron down the line i. Common kind: Acetylcholine which communicates between neurons and muscle cells c. Curare is an antagonist to acetylcholine because it blocks it , once curare is in the blood, the communication between nerves and muscles id blocked VIII. Information Processing a. Information require energy i. Biological systems fight off entropy (disorganization) ii. Neurons use as metabolic energy to create an d maintain informationiii. Neuron use chemical energy to create a discontinuous chemical gradient across the cell membrane b. Information involves alternativesi. Information us communicated by distinction, the contrast between at least two possible signals ii. Most common us between an action potential c. Information is Layered i. One set of distinction is used to create another set ii. Neurons: the most fundamental is between positive and negative polarities across cell membraned. Information is a relational propertyi. Afferent Neurons: receive information from senses ii. Efferent Neurons: receive signs from other neurons, process them, and passes the message iii. Most neurons are Interneurons: receive info from one set of neurons and talk to another setIX. Requirements of Response System / Properties of the nervous system a. Signals must be able to traveli. Neurons are linked in series by their long axonsb. Signals must interact in central pathi. Neural pathways from the senses converge in the CNS and from the dispatch messages to the muscle. Within CNS, neurons are highly interconnected c. Signals must be able to sum and inhibit one another i. The combination of excitatory and inhibitory connections and an activation threshold enables the neurons to sum and inhibit one another d. Signals and responses must be powered independently of the stimulus that triggers them i. The energy for carrying out neurons and muscle fibers activities comes from cellular metabolism rather than the stimulus that triggers them.e. Any stimulus must be able to elicit any response i. The nervous system is so connected that any possible stimulus can be used to signal and possible