Neurons and Synapses, Hormones and neurotransmitters PDF

Neurons and Synapses Hormones and neurotransmitters Ms. Hanna Mae A. Caparas, MP, RPm, CHRA Instructor The Cells of the Nervous System NEURONS Cells of the nervous system that are specialized for information processing and communication. Receive information and transmit i...

Neurons and Synapses Hormones and neurotransmitters Ms. Hanna Mae A. Caparas, MP, RPm, CHRA Instructor The Cells of the Nervous System NEURONS Cells of the nervous system that are specialized for information processing and communication. Receive information and transmit it to other cells GLIA (OR NEUROGLIA) Do not transmit information over long distances as neurons do, although they perform many other functions: Cells in the nervous system that support the activities of neurons. Glia : Cells in the nervous system that support the activities of neurons Astrocytes have several support functions. Through their close association with the blood supply, astrocytes help transfer nutrients to neurons and block the movement of some circulating toxins into neural tissue. Astrocytes also provide a structural matrix for neurons, holding them in place. The Structure of Neurons Neurons have four major parts: a cell body, dendrites, an axon, and presynaptic terminals. The Structure of Neurons cell body / soma -The main mass of a neuron, containing the nucleus and many organelles dendrites -The branch of a neuron that generally receives information from other neurons. Axon- The branch of a neuron usually responsible for carrying signals to other neurons. Synapse- The junction between two neurons at which information is transferred from one to another. Myelin sheath- The fatty insulation around many axons Neuron Membranes The neural membrane is composed of a two-molecule thick layer of phospholipids. Embedded within the phospholipid membrane are ion channels and pumps, which are specialized proteins that allow chemicals to pass into and out of the neuron.  Neural Cytoskeleton neural cytoskeleton - provides structural support and the ability to transport needed substances within the neuron. Microtubules provide means for transporting materials within the neuron. anterograde transport-Movement of materials from the cell body of a neuron to the axon terminal along the microtubules. retrograde transport- Movement of material from the axon terminal back to the cell body via the cell’s system of microtubules Neurofilaments provide structural support Microfilaments may be involved with structural changes associated with learning. Functional Variations in Neurons Sensory neurons - specialized to receive information from the outside world. These neurons can translate many types of information, such as light or sound waves, into neural signals that the nervous system can process. Motor neurons-transmit commands from the central nervous system directly to muscles and glands. Interneurons - not specialized for either sensory or motor functions but act as bridges between the sensory and motor systems Classes of Neurons based on the number of processes (projections) emanating from their cell bodies: unipolar neuron - A neuron with one process extending from its cell body bipolar neuron- A neuron with two processes extending from its cell body multipolar neuron- A neuron with more than two processes extending from its cell body; most neurons are multipolar. interneurons- Neurons with a short axon or no axon at all. Blood–brain barrier The blood–brain barrier prevents most toxins circulating in the blood from entering the brain. Because of the blood–brain barrier, many molecules cannot enter the brain. The blood–brain barrier consists of an unbroken wall of cells that surround the blood vessels of the brain and spinal cord  Neural Impulse-the electrochemical discharge of a nerve cell, or neuron polarize – to ready a neuron for firing by creating an internal negative charge in relation to the body fluid outside the cell membranes Resting potential - the electrical potential across the neural membrane when it is not responding to other neurons depolarize – to reduce the resting potential of a cell membrane Action potential- Conduction of neural impulse along axon  Firing: Neuron to Neuron Firing -Conduction of neural impulse along the length of a neuron Threshold-Incoming messages reach a strength at which neuron will fire All-or-none principle- Every time a neuron fires, it transmits an impulse of the same strength. A significant amount of charge must be felt for the commencement of Action Potential Refractory period- Period of recovery time between firings  synapse – a junction between the axon terminals of one neuron and the dendrites or cell body of another neuron Neurotransmitters-Chemical substances that communicate from one neuron to another Synaptic vesicles- Contain neurotransmitters in the axon terminals receptor site – a location on a dendrite of a receiving neuron tailored to receive a neurotransmitter Excitatory neurons- Cause other neurons to fire Inhibitory neurons- Prevent other neurons from firing Neurons send signals in a process known as action potential. An action potential is a shift in the neuron’s electric potential caused by the flow of ions in and out of the neural membrane. Action potentials trigger both chemical and electrical synapses Chemical and Electrical Synapse chemical synapse- A type of synapse in which messages are transmitted from one neuron to another by chemical neurotransmitters. electrical synapse- A type of synapse in which a neuron directly affects an adjacent neuron through the movement of ions from one cell to the other. https://www.researchgate.net/publication/370863684/figure/fig4/AS:11431281188891768@1694798 821388/a-b-Basic-structure-and-operation-of-chemical-synapses-a-and-electrical-synapses-b.png Synaptic Transmission: Chemical Transmission of Signals among Neurons Methods for Deactivating Neurotransmitters Deactivation may occur through: (a) diffusion away from the synapse (b) through the action of special enzymes (c) through reuptake Neurotransmitters A chemical messenger that communicates across a synapse. Most neurotransmitters produce either excitation or inhibition, not both  and are released in have an deactivated Neurotransmitters response to the observable effect following release are manufactured arrival of an on the by reuptake or by within neurons, action potential postsynaptic cell, the action of enzymes. Neurotransmitters Gamma-aminobutyric acid Hormones A hormone is a chemical that is secreted by cells in one part of the body and conveyed by the blood to influence other cells. Hormones are particularly useful for coordinating long lasting changes in multiple parts of the body. Regulate growth, metabolism and some behaviors Maintain steady bodily states (Homeostasis) Hormones Regulated by Pituitary Gland (the master gland) Growth hormone – regulates growth of muscles, bones, and glands Prolactin – regulates maternal behavior in lower mammals and stimulates production of milk in women Vasopressin – inhibits production of urine when body fluids are low Oxytocin – stimulates labor in pregnant women, connected with maternal behavior Glands Pineal gland- Secretes melatonin; Helps regulate sleep-wake cycle Thyroid gland-Produces Thyroxin; Affects body’s metabolism: Hypothyroidism – Thyroxin deficiency Hyperthyroidism – Too much thyroxin Glands Adrenal glands Located above the kidneys Cortical steroids increase resistance to stress promote muscle development Testes and Ovaries Testosterone and Androgen produced by testes (smaller amounts from adrenal gland) male sex characteristics Estrogen and progesterone produced by ovaries female sex characteristics Steroids, Behavior, and Mental Processes Steroids Anabolic steroids increase muscle mass, Enhance athletic prowess heighten resistance to stress, connected with self-confidence, increase body’s energy supply aggressiveness, memory function  Drugs and Behavior Refer mainly to chemical or plant-derived substances that affect psychological, behavioral or physical functions and lead to varying degrees of dependence or addiction. Drugs either facilitate or inhibit transmission at synapses. A drug that blocks a neurotransmitter is an antagonist, whereas a drug that mimics or increases the effects is an agonist. Drugs act in many ways, varying in their affinity (tendency to bind to a receptor) and efficacy (tendency to activate it). The effectiveness and side effects of drugs vary from one person to another. Drugs have different effects on the nervous system, depending on their method of administration Psychoactive drugs usually administered to obtain a particular psychological effect. these drugs circumvent the protective systems of the blood–brain barrier to gain access to the central nervous system  Drugs substance substance abuse – dependence – loss of persistent use of a control over use of a substance even substance; biologically though it is causing or speaking, dependence compounding is typified by tolerance, problems in meeting withdrawal symptoms, the demands of life or both  Drugs Addiction-A compulsive craving for drug effects or other experience. Most addictive substances enhance activity in the dopaminergic nucleus accumbens of the brainstem. More of “wanting” than to “liking” Continued use of some drugs can produce tolerance and withdrawal: Tolerance-The process in which more of a drug is needed to produce the same effect. Withdrawal-The symptoms that occur when certain addictive drugs are no longer administered or are administered in smaller quantities.  Stimulants (uppers) – Speed up the brain and central nervous system. Examples are caffeine (coffee, tea) nicotine (cigarettes), amphetamines, cocaine and diet pills. Depressants (downers) – Slow down the brain and central nervous system. Types of Examples are alcohol, beer, wine, vodka, gin drugs etc. heroin, tranquilizers, sleeping pills. Hallucinogens – These drugs alter the user’s state of consciousness. (Distort auditory and visual sensations) Examples are LSD, ecstasy, magic mushrooms, marijuana. St. John’s Wort Hallucinogen Mushroom Magic Mushrooms