M2-CS-01.pdf

Case 1 - EXPLOSION Few hours PTC, Ralph was attending the opening of his sister’s restaurant, when suddenly a loud explosion was heard. There was smoke all over the area, and found himself running towards the door. He then saw his friend lying on the floor, he was able to carry her outside the buil...

Case 1 - EXPLOSION Few hours PTC, Ralph was attending the opening of his sister’s restaurant, when suddenly a loud explosion was heard. There was smoke all over the area, and found himself running towards the door. He then saw his friend lying on the floor, he was able to carry her outside the building. His heart was pounding hard when he saw what happened to the restaurant, there was an explosion coming from the ceiling.  Loud explosion - triggering event to Ralph’s action  Running towards the door - natural reaction  Carry a heavy load (Sister) - stress response  Heart Pounding hard - sympathetic stimulation At the ER, Ralph’s heart was still pounding and his knees were trembling. He can’t believe that he was able to carry his friend, who weighs 51kgs, and run out of the smoked filled room Vital Signs: HR: 118bpm BP: 140/80mmHg Wt. 70kgs RR: 22cpm Temp: 37.2C Physical Examination: HEENT: (+) contusion hematoma on the forehead 2x2cm, (-) Lacerations; clear sclera, intact EOM’s; normal otoscopic findings; normal anterior rhinoscopy; unremarkable oral cavity CVS: Dynamic precordium; Tachycardic, regular rhythm Respi: Clear breath sounds, Tachypneic Abdomen: Soft, no visible bruising Extremities: Superficial abrasions on both arms and legs, No lacerations NVS: Normal neurological exam Disposition at the ER: Ralph was discharged from the ER, after almost 4hours. VS upon discharge: HR: 86bm BP: 120/60mmHg RR: 16cpm Temp: 37.3C   The functional unit in both the CNS and PNS is the neuron or nerve cell.  The cell body, or perikaryon, which contains the nucleus and most of the cell’s organelles and serves as the synthetic or trophic center for the entire neuron. Basic Unit of  The dendrites, which are the numerous elongated the Nervous processes extending from the perikaryon and specialized to receive stimuli from other neurons at System unique sites called synapses.  The axon (Gr. axon, axis), which is a single long process ending at synapses specialized to generate and conduct nerve impulses to other cells (nerve, muscle, and gland cells).  Neurons can be classified according to the number of processes extending from the cell body  Most neurons are multipolar.  Bipolar neurons are found in the retina, olfactory mucosa, and the (inner ear) cochlear and vestibular ganglia, where they serve the senses of sight, smell, and balance, respectively.  Pseudounipolar neurons are found in the spinal ganglia (the sensory ganglia found with the spinal nerves) and in most cranial ganglia.   Sensory neurons are afferent and receive stimuli from the receptors throughout the body.  Motor neurons are efferent, sending impulses to effector organs such as muscle fibers and glands. Nervous components can also  Somatic motor nerves are under voluntary control and typically innervate be subdivided functionally. most skeletal muscle;  autonomic motor nerves control the “involuntary” activities of glands, cardiac muscle, and most smooth muscle.  Interneurons establish relationships among other neurons, forming complex functional networks or circuits (as in the CNS and retina).  Figure 46-6 shows a typical anterior motor neuron in the anterior horn of the spinal cord. It is composed of three major parts: the soma, which is the main body of the neuron; a single axon, which extends from the soma into a peripheral nerve that leaves the spinal cord; and the dendrites, which are great numbers of branching projections of the soma that extend as much as 1 millimeter into the surrounding areas of the cord.  Figure 46-5A illustrates the basic structure of a chemical synapse, showing a single presynaptic terminal on the membrane surface of a postsynaptic neuron.  The presynaptic terminal is separated from the postsynaptic neuronal soma by a synaptic cleft having a width usually of 200 to 300 angstroms. The terminal has two internal structures important to the excitatory or inhibitory function of the synapse: the transmitter vesicles and the mitochondria.  The transmitter vesicles contain the neurotransmitter that, when released into the synaptic cleft, either excites or inhibits the postsynaptic neuron. It excites the postsynaptic neuron if the neuronal membrane contains excitatory receptors, and it inhibits the neuron if the membrane contains inhibitory receptors.  The mitochondria provide adenosine triphosphate (ATP), which in turn supplies the energy for synthesizing new transmitter substance.   The membrane of the presynaptic terminal is called the presynaptic membrane. Mechanism by Which an Action Potential Causes  It contains large numbers of voltage-gated calcium channels. Transmitter Release from the  When an action potential depolarizes the presynaptic membrane, these Presynaptic Terminals—Role of calcium channels open and allow large numbers of calcium ions to flow Calcium Ions into the terminal.  The quantity of neurotransmitter that is then released from the terminal into the synaptic cleft is directly related to the number of calcium ions that enter.  When the calcium ions enter the presynaptic terminal, they bind with special protein molecules on the inside surface of the presynaptic membrane, called release sites.  This binding in turn causes the release sites to open through the membrane, allowing a few transmitter vesicles to release their transmitter into the cleft after each single action potential.  For the vesicles that store the neurotransmitter acetylcholine, between 2,000 and 10,000 molecules of acetylcholine are present in each vesicle, and there are enough vesicles in the presynaptic terminal to transmit from a few hundred to more than 10,000 action potentials.   The membrane of the postsynaptic neuron contains large numbers of receptor proteins  The molecules of these receptors have two important components:  (1) a binding component that protrudes outward from the membrane into the synaptic cleft— here it binds the neurotransmitter coming from the presynaptic terminal—and  (2) an intracellular component that passes all the way through the postsynaptic membrane to the interior of the postsynaptic neuron. Action of the Transmitter  Receptor activation controls the opening of ion channels in the Substance on the Postsynaptic postsynaptic cell in one of two ways: Neuron—Function of “Receptor  (1) by gating ion channels directly and allowing passage of specified types of Proteins” ions through the membrane, or  (2) by activating a “second messenger” that is not an ion channel but instead is a molecule that protrudes into the cell cytoplasm and activates one or more substances inside the postsynaptic neuron. These second messengers increase or decrease specific cellular functions.  Neurotransmitter receptors that directly gate ion channels are often called ionotropic receptors, whereas those that act through second messenger systems are called metabotropic receptors.   is the portion of the nervous system that controls most visceral functions of the body.  This system helps to control arterial pressure, gastrointestinal motility, gastrointestinal secretion, urinary bladder emptying, sweating, body temperature, and many other activities.  Some of these activities are controlled almost entirely and some only partially Autonomic by the autonomic nervous system. Nervous  One of the most striking characteristics of the autonomic nervous system is the rapidity and intensity with which it can change visceral functions. System  For instance, within 3 to 5 seconds it can increase the heart rate to twice normal, and within 10 to 15 seconds the arterial pressure can be doubled.  At the other extreme, the arterial pressure can be decreased low enough within 10 to 15 seconds to cause fainting.  Sweating can begin within seconds, and the urinary bladder may empty involuntarily, also within seconds.   The autonomic nervous system is activated mainly by centers located in the spinal cord, brain stem, and hypothalamus. General  In addition, portions of the cerebral cortex, especially of the limbic cortex, can transmit signals to the lower centers and in this way can influence Organization autonomic control.  The efferent autonomic signals are transmitted to the various organs of of the ANS the body through two major subdivisions called the  sympathetic nervous system and  the parasympathetic nervous system Physiological Anatomy of the Sympathetic Nervous System  Figure 61-1 shows the general organization of the peripheral portions of the sympathetic nervous system.  Shown specifically in the figure are  (1) one of the two paravertebral sympathetic chains of ganglia that are interconnected with the spinal nerves on the side of the vertebral column,  (2) prevertebral ganglia (the celiac, superior mesenteric, aortico-renal, inferior mesenteric, and hypogastric), and  (3) nerves extending from the ganglia to the different internal organs.  The sympathetic nerve fibers originate in the spinal cord along with spinal nerves between cord segments T1 and L2 and pass first into the sympathetic chain and then to the tissues and organs that are stimulated by the sympathetic nerves. Preganglionic and Postganglionic Sympathetic Neurons  The sympathetic nerves are different from skeletal motor nerves in the following way:  Each sympathetic pathway from the cord to the stimulated tissue is composed of two neurons, a preganglionic neuron and a postganglionic neuron, in contrast to only a single neuron in the skeletal motor pathway.  The cell body of each preganglionic neuron lies in the intermediolateral horn of the spinal cord; its fiber passes through a ventral root of the cord into the corresponding spinal nerve, as shown in Figure 61-2. Sympathetic Nerve Fibers in the Skeletal Nerves.  Some of the postganglionic fibers pass back from the sympathetic chain into the spinal nerves through gray rami at all levels of the cord, as shown in Figure 61-2.  These sympathetic fibers are all very small type C fibers, and they extend to all parts of the body by way of the skeletal nerves.  They control the blood vessels, sweat glands, and piloerector muscles of the hairs.  About 8 percent of the fibers in the average skeletal nerve are sympathetic fibers, a fact that indicates their great importance.   Preganglionic sympathetic nerve fibers pass, without synapsing, all the way from the intermediolateral horn cells of the spinal cord, through the sympathetic chains, then through the splanchnic nerves, and finally into the two adrenal medullae. Special Nature of the  There they end directly on modified neuronal cells that secrete Sympathetic Nerve Endings in epinephrine and norepinephrine into the blood stream. the Adrenal Medullae  These secretory cells embryologically are derived from nervous tissue and are actually postganglionic neurons; indeed, they even have rudimentary nerve fibers, and it is the endings of these fibers that secrete the adrenal hormones epinephrine and norepinephrine.  The parasympathetic nervous system is shown in Figure 61-3, which demonstrates that parasympathetic fibers leave the central nervous system through cranial nerves III, VII, IX, and X;  additional parasympathetic fibers leave the lowermost part of the spinal cord through the second and third sacral spinal nerves and occasionally the first and fourth sacral nerves.  About 75 percent of all parasympathetic nerve fibers are in the vagus nerves (cranial nerve X), passing to the entire thoracic and abdominal regions of the body.  Therefore, a physiologist speaking of the parasympathetic nervous system often thinks mainly of the two vagus nerves.  The vagus nerves supply parasympathetic nerves to the heart, lungs, esophagus, stomach, entire small intestine, proximal half of the colon, liver, gallbladder, pancreas, kidneys, and upper portions of the ureters.   The parasympathetic system, like the sympathetic system, has both preganglionic and postganglionic neurons. Preganglionic and  However, except in the case of a few cranial parasympathetic nerves, the preganglionic fibers pass uninterrupted all the way to the organ that is to Postganglionic be controlled. Parasympathetic  The postganglionic neurons are located in the wall of the organ. Neurons  The preganglionic fibers synapse with these neurons, and extremely short postganglionic fibers, a fraction of a millimeter to several centimeters in length, leave the neurons to innervate the tissues of the organ.  The fibers that secrete acetylcholine are said to be cholinergic.  Those that secrete norepinephrine are said to be adrenergic, a term derived from adrenalin, which is an alternate name for epinephrine.   Acetylcholine is synthesized in the terminal endings and varicosities of the cholinergic nerve fibers, where it is stored in vesicles in highly concentrated form until it is released. Synthesis of Acetylcholine, Its  The basic chemical reaction of this synthesis is the following: Destruction after Secretion, and Its Duration of Action  Once acetylcholine is secreted into a tissue by a cholinergic nerve ending, it persists in the tissue for a few seconds while it performs its nerve signal transmitter function.  Then it is split into an acetate ion and choline, catalyzed by the enzyme acetylcholinesterase that is bound with collagen and glycosaminoglycans in the local connective tissue.   Synthesis of norepinephrine begins in the axoplasm of the terminal nerve endings of adrenergic nerve fibers but is completed inside the secretory vesicles.  The basic steps are the following: Synthesis of Norepinephrine, Its Removal, and Its Duration of Action  In the adrenal medulla, this reaction goes still one step further to transform about 80 percent of the norepinephrine into epinephrine, as follows:  After secretion of norepinephrine by the terminal nerve endings, it is removed from the secretory site in three ways:  (1) reuptake into the adrenergic nerve endings by an active transport process, accounting for removal of 50 to 80 percent of the secreted norepinephrine;  (2) diffusion away from the nerve endings into the surrounding body fluids and then into the blood, accounting for removal of most of the remaining norepinephrine; and  (3) destruction of small amounts by tissue enzymes (one of these enzymes is monoamine oxidase, which is found in the nerve endings, and another is catechol-O-methyl transferase, which is present diffusely in the tissues).  Ordinarily, the norepinephrine secreted directly into a tissue remains active for only a few seconds, demonstrating that its reuptake and diffusion away from the tissue are rapid.   Acetylcholine activates mainly two types of receptors, which are called muscarinic and nicotinic receptors.  The reason for these names is that  muscarine, a poison from toadstools, activates only muscarinic receptors and will not activate nicotinic receptors,  whereas nicotine activates only nicotinic receptors. Acetylcholine activates both of them. What are the two principal types of acetylcholine  Muscarinic receptors, which use G proteins as their signaling mechanism, receptors? are found on all effector cells that are stimulated by the postganglionic cholinergic neurons of either the parasympathetic nervous system or the sympathetic system.  Nicotinic receptors are ligand-gated ion channels found in autonomic ganglia at the synapses between the preganglionic and postganglionic neurons of both the sympathetic and parasympathetic systems.   Two major classes of adrenergic receptors also exist; they are called alpha receptors and beta receptors.  Norepinephrine and epinephrine, both of which are secreted into the What are the two major blood by the adrenal medulla, have slightly different effects in exciting the adrenergic receptors? alpha and beta receptors.  Norepinephrine excites mainly alpha receptors but excites the beta receptors to a lesser extent as well. Epinephrine excites both types of receptors approximately equally. List the excitatory and inhibitory actions of sympathetic and parasympathetic stimulation.  There is no generalization one can use to explain whether sympathetic or parasympathetic stimulation will cause excitation or inhibition of a particular organ.   Stimulation of the sympathetic nerves to the adrenal medullae causes large quantities of epinephrine and norepinephrine to be released into the circulating blood, and these two hormones in turn are carried in the blood to all tissues of the body. Function of  On average, about 80 percent of the secretion is epinephrine and 20 Adrenal percent is norepinephrine.  Stimulation of the adrenal medullae causes release of the hormones Medullae epinephrine and norepinephrine, which together have almost the same effects throughout the body as direct sympathetic stimulation, except that the effects are prolonged, lasting 2 to 4 minutes after the stimulation is over.   The sympathetic and parasympathetic systems are continually active, and the basal rates of activity are known, respectively, as sympathetic tone Sympathetic and and parasympathetic tone. Parasympathetic  The value of tone is that it allows a single nervous system to both increase and decrease the activity of a stimulated organ. tone What do you call the reaction of Ralph during the incident causing him to run and carry his friend? “ALARM” OR “STRESS” RESPONSE OF THE SYMPATHETIC NERVOUS SYSTEM When large portions of the sympathetic nervous system discharge at the same time—that is, a mass discharge— this action increases the ability of the body to perform vigorous muscle activity in many ways, as summarized in the following list: 1. Increased arterial pressure 2. Increased blood flow to active muscles concurrent with decreased blood flow to organs such as the gastrointestinal tract and the kidneys that are not needed for rapid motor activity 3. Increased rates of cellular metabolism throughout the body 4. Increased blood glucose concentration 5. Increased glycolysis in the liver and in muscle 6. Increased muscle strength 7. Increased mental activity 8. Increased rate of blood coagulation  The sum of these effects permits a person to perform far more strenuous physical activity than would otherwise be possible. Because either mental or physical stress can excite the sympathetic system, it is frequently said that the purpose of the sympathetic system is to provide extra activation of the body in states of stress, which is called the sympathetic stress response.  The sympathetic system is especially strongly activated in many emotional states.  For instance, in the state of rage, which is elicited to a great extent by stimulating the hypothalamus, signals are transmitted downward through the reticular formation of the brain stem and into the spinal cord to cause massive sympathetic discharge; most aforementioned sympathetic events ensue immediately.  This is called the sympathetic alarm reaction.  It is also called the fight-or-flight reaction because an animal in this state decides almost instantly whether to stand and fight or to run. In either event, the sympathetic alarm reaction makes the animal’s subsequent activities vigorous. GOODLUCK! (Please read your references…) (This is just a guide)