Lo mila blok 5 up 2
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INDIVIDUAL ASSIGNMENT BLOCK 5 STUDY UNIT 2 Peripheral Nervous System
By: Istianah Maryam Jamilah 2011/315747/KH/7098
Faculty of Veterinary Medicine Gadjah Mada University Yogyakarta 2012
I. Learning Objectives 1. What are neurotransmitter components (type) and function? 2. How is the impulse transmitted trough synapse? 3. How the reflex happen? 4. Complete definition of PNS and its nerve? II. Explanation 1. Neurotransmitter components and function Neurotransmitters are substances that are produced by neurons, stored in the synapses and released in to the synaptic reflect in response to a stimulus. At the post synaptic membrane, they bind to special receptors and affect their activity (Koolman and Roehm, 2005). Neurotransmitters are the chemicals which allow the transmission of signals from one neuron to the next across synapses (Boeree, 2009).
EXCITATORY Acetylcholine (Ach) Aspartat Dopamine Histamine Norepinephrine Epinephrine Glutamat Serotonine
INHIBITORY GABA Glisin Dopamine
A. Small molecule neurotransmitter a. Acetylcholine (C7H16O2N/ CH3COOCH2CH2N) The Acetic acid ester of the cationic alcohol choline acts at neuromuscular junctions, where its triggers muscle contraction and in certain parts of the brain and the autonomous nervous system (Koolman and Roehm, 2005). Proteinogenic Amino Acid Neurotransmitter b. Glutamate It is acts as a stimulatory transmitter in the CNS. More than half of synapses in the brain are glutaminergic.The amine GABA also synthetized from it. c. Glycine Glycine is an inhibitory neurotransmitter with effects in the spinal cord and in parts of the brain (Koolman and Roehm, 2005). A neurotransmitter used mainly by neurons in the spinal cord. It probably always acts as an inhibitory neurotransmitter. Biogenic amines Arise from amino acid by decarboxylation. d. 4-aminobutyrate (-aminobutyric acid/ GABA) Formed from glutamate and is the most important inhibitory transmitter in CNS (Koolman and Roehm, 2005). Inhibits excretory neurotransmitters; decreases anxiety and paranoia; maintains proper firing of nerve impulses. GABA acts like a brake to the excitatory neurotransmitters that lead to anxiety. People with too little GABA
tend to suffer from anxiety disorders, and drugs like Valium work by enhancing the effects of GABA. Lots of other drugs influence GABA receptors, including alcohol and barbituates. If GABA is lacking in certain parts of the brain, epilepsy results (Boeree, 2009). e. Norephinephrine Norepinephrine is strongly associated with bringing our nervous systems into "high alert." It is prevalent in the sympathetic nervous system, and it increases our heart rate and our blood pressure. Our adrenal glands release it into the blood stream, along with its close relative epinephrine (aka adrenalin). It is also important for forming memories (Baroore, 2009). Norepinephrine acts as a neurotransmitter and a hormone. In the peripheral nervous system, it is part of the flight-or-flight response. In the brain, it acts as a neurotransmitter regulating normal brain processes. Norepinephrine is usually excitatory, but is inhibitory in a few brain areas. f. Serotonin Serotonin is an inhibitory neurotransmitter that has been found to be intimately involved in emotion and mood. Too little serotonin has been shown to lead to depression, problems with anger control, obsessive-compulsive disorder, and suicide. Too little also leads to an increased appetite for carbohydrates (starchy foods) and trouble sleeping, which are also associated with depression and other emotional disorders. It has also been tied to migraines, irritable bowel syndrome, and fibromyalgia ( Baroore, 2009). g. Dopamine The neurotransmitter that produces feelings of pleasure when released by the brain reward system. Dopamine has multiple functions depending on where in the brain it acts. It is usually inhibitory.Inhibits prolactine release. Feelings of happiness, pleasure and content; increased social behavior; muscle movement control ( Baroore, 2009). Function summary Neurotransmitter Acetylcholine Role in the Body A neurotransmitter used by the spinal cord neurons to control muscles and by many neurons in the brain to regulate memory. In most instances, acetylcholine is excitatory.
The neurotransmitter that produces feelings of pleasure when released by the brain reward system. Dopamine has multiple functions depending on where in the brain it acts. It is usually inhibitory. The major inhibitory neurotransmitter in the brain.
GABA (gammaaminobutyric acid) Glutamate Glycine
The most common excitatory neurotransmitter in the brain. A neurotransmitter used mainly by neurons in the spinal cord. It probably always acts as an inhibitory neurotransmitter. Norepinephrine acts as a neurotransmitter and a hormone. In the peripheral nervous system, it is part of the flight-or-flight response. In the brain, it acts as a neurotransmitter regulating normal brain processes. Norepinephrine is usually excitatory, but is inhibitory in a few brain areas. A neurotransmitter involved in many functions including mood, appetite, and sensory perception. In the spinal cord, serotonin is inhibitory in pain pathways. NIH Publication No. 00-4871 http://outreach.mcb.harvard.edu/teachers/Summer05/RaymondBroadhead /Synapses_and_Drugs.pdf
2. Impuls transmitted trough synapse
Synapses is a unique junction that controls the communication between one neuron to another cell. Cells that conduct signals called prasimpatic cells and cells that received the cell called the parasympathetic. Synapses are of two types: electrical synapses and chemical synapses. Electrical synapses allow action potentials propagate directly from cell to cell prasinanptik post-synaptic. These cells are loosely connected by junction channels between cells that is the local action potential ion stream to flow between neurons. This allows the impulses travel from one neuron to another neuron without delay and without loss of signal strength. (Campbell, 2007).
(Campbell, 2007) Chemical synapses, the synaptic cleft separating the cells post-synaptic prasinaptik of cells, causing the cells can not be matched electrically and action potentials that occur in the cells can not be slowed prasinaptik directly to the postsynaptic cell membrane. Inside the bag there are many chemical synapses (synaptic vesicles) that contain thousands of neurotransmitter molecules, which are substances that were released as a messenger between cells into the synaptic cleft. (Campbell, 2007)
3. How Reflex Happen
(Campbell, 2007) Reflex have five primary components: a. Reflex is start with receptor. Receptor transduce some environment energy into action potrentiol along the sensory nerve. For example: -Receptor at the retina that transduce light energy. -Skin that transduce heat, cold, pressure, and other cutaneuos stimule. -Muscle spindle receptor that tranduce stretch In transduction, action potential are genetrated along sensory nerves at a frequency proportional to the intensity with which the receptor is stimulated and and the frequency os the resulting sensory nerve action potoential is called frequency codingand its how the receptor comunicates to the CNS the instensity of light, heat, stretch, and so forth its transduced (Cunningham, 2002). b. Sensory nerve (afferent nerve) that carry action potential from the receptor to the CNS which entered the spinal cord by way of the dorsal roots c. Synapse in CNS. Actually most reflex arcs, more than one synapse occurs. However, a few reflex arcs, such as those that come from the muscle spindle, are monosynaptic. d. Motor nerve (efferent nerve), which carries action potential from the CNS to the target (effector) organ. Motor nerve leave the spinal cord depart by way of the ventral root. e. The targeted organ(effector organ) that causes the reflex response. These usually a muscle, such as skeletal muscle of the quadriceps muscle of the leg, in the case of knee jerk(muuscle stretch) reflex, or the smooth muscle of the iris, in the case of pupillary light reflex (Cunningham, 2002). Reflex arcs are either segmental or intersegmental
Segmental reflex is a reflex in which the reflex arc through only a small segment of CNS. For example are the muscle stretch reflex and the pappilary light reflex because they are only use a small segment of either the spinla cord or the brain stem. In the intersegmental reflex, multiple segments of the CNS are used. Concious proprioceptions response is a good example of this type. Because of the sensory action potential may enter as far away as the lumbar spinal cord and yet travel all the way to the cerebral cortex before the motor response is generted. The motor response returns along roughly the same intersegmenteal route (Cunningham, 2002).4. Peripheral Nervous System
Peripheral nervous system or peripheral nervous system is the nervous system includes the cranial nerves and spinal nervous. Peripheral nervous system (PNS) is divided into two subsystems, namely the motor (efferent) and sensory (afferent). The motor component of the nervous cranial and spinal nervous that the motor neurons and autonomic somatic motor neurons. a.) Somatic motor neurons (axons of somatic efferent neurons) bring an action potential command and central nervous system to the sympathetic junction in skeletal muscle.
b.) Autonomic motor neurons (axons visceral efferent neurons) bring an action potential, through synaps intermediates, to synaps in smooth muscle, cardiac muscle and exocrine glands. Peripheral sensory nerves carry messages to the action potential of the central nervous system peripheral receptors. This receptor is responsible for converting environmental energy (light, noise, muscle activity) to