lecture_Ch04_1[1]

lecture_Ch04_1[1] - Drugs and Behavior Drugs Homeostatic...

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Unformatted text preview: Drugs and Behavior Drugs Homeostatic Systems and Drugs – part I PSY 291 PSY number Your exam results and scores through the quarter will be posted in the Course Studio. First scores after one week will be posted today. Due to the privacy issue your names were replaced by the PSY number. The PSY number was send to each of you individually last week. Homeostasis Homeostasis Two elaborate The body’s self-regulating continuous adjustment systems: nervous to internal and external system and the changes in the endocrine system = environment by Homeostasis This process uses endogenous chemicals to maintain both the body’s physiological and psychological stability. By understanding mechanisms regulating homeostasis, we may be able to better identify drug treatments that are effective. Introduction to Nervous Systems Introduction All nervous systems consist of specialized All nerve cells called neurons and glia (supporting cells). Neurons receive and send information Communication by both chemical and Communication and electrical signals electrical Homeostatic functions of the nervous systems Homeostatic is achieved through the activity of neurons CNS Support Cells CNS Glia (neuroglia, glial cells) – supporting cells of the CNS. Surround neurons and hold them in place Supply nutrients and oxygen to neurons Insulate one neuron from another, preventing neural Insulate messages from getting scrambled messages Form the myelin sheath around axons Form Destroy pathogens and remove dead neurons Destroy Nerve cell (neuron) specializations Basic Structure Soma – cell body of a neuron which contains the Soma nucleus. nucleus. Dendrite – branched, treelike structure attached to the Dendrite soma; receives information from other neurons. soma; Synapse – junction between the terminal button of an Synapse axon and the membrane of another neuron. axon Axon – long, thin, cylindrical structure that conveys Axon information from the soma of a neuron to its terminal buttons. buttons. Terminal Buttons – bud at the end of a branch of an Terminal axon. axon. A typical neuron 1. Carries impulses toward or away from the CNS. 2. Communicates with other neurons or target cells by releasing the neurotransmitter. 3. Has cell body with the nucleus. 4. Has cell processes: a. axon – carries signals away from the cell body. Could be myelinated or unmyleinated. b. dendrites – carry signals toward the cell body. Unmyleinated. Transfer of messages by neurons Transfer Dendrite- receiving region of neuron receiving affected by a chemical messenger (NT) either excites or inhibits If excited, electrical impulse moves down the If axon to the… axon Terminal- the sending region the NTs (chemical messengers) are released Sending Messages by Neurons Sending Neurons Each neuron in the central nervous system Each is in close proximity with other neurons. is Although they are close, neurons never Although actually touch. actually Synapses Synapse – the point of communication between one neuron and another between Synaptic cleft – the gap between neurons at the synapse (~20 nm) the Synaptic vesicles transport NTs to the terminal membrane at the synapse terminal By fusing with the terminal membrane they By release contents into the cleft release Synapses The axon terminal (presynaptic element) contains: Mitochondria that provide energy for axon functions. Synaptic vesicles (round objects) that contain neurotransmitter. Presynaptic Membrane – membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released. Postsynaptic Membrane – cell membrane opposite the terminal button in a synapse. Synapse Synapses Synapses Excitatory synapse—initiates an impulse in initiates the receiving neuron when stimulated, causing release of neurotransmitters or increasing activity in target cell increasing Inhibitory synapse—diminishes likelihood diminishes of an impulse in the receiving neuron or reduces the activity in other target cells reduces Synapses Neurons can send discrete excitatory or Neurons inhibitory messages (# of vesicles) to their target cells. target A receiving neuron or target cell may have receiving many excitatory and inhibitory synapses. many Final cellular activity is a summation of Final summation these many excitatory and inhibitory synaptic signals. synaptic Excitatory neuron Inhibitory neuron Target neuron Communication Between Neurons Communication Neural Integration – process by which inhibitory Neural and excitatory postsynaptic potentials summate and control the rate of firing of a neuron. and Types of Neurons Types Sensory Neuron – neuron that detects changes in the external or internal environment and sends information about these changes to the CNS. these Motor Neuron – neuron that controls the contraction of a muscle or the secretion of a gland. gland. Interneuron – neuron located entirely within the CNS, connecting other neurons. within Reflex Arc – Withdrawal Reflex Withdrawal Reflex Arc – Withdrawal Reflex Withdrawal Can be modulated by brain. Brain signals inhibitory interneuron to prevent muscle contraction. Patella reflex (stretch reflex) Crossed extension reflex Transfer of messages by neurons Transfer Neurotransmitters travel and attach to large Neurotransmitters proteins in the membrane of the target cells. proteins The proteins are called receptors. The receptors Activation of receptors causes a change in the Activation activity of the target cell; the target cells can be other neurons or cells that make up organs, muscles, or glands. muscles, Receptors only interact with molecules that Receptors have specific configurations have Lock & Key hypothesis Agonists—substances or drugs that activate —substances receptors receptors Antagonists—substances or drugs that —substances attach to receptors and prevent them from being activated being ...
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