The Nervous System

The Nervous system
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is communication network that controls and coordinates the body activities.

Every though, memory, emotion or sensation a person has and every action he or she carries out is reflection of the nervous system.

works unnoticed to regulate a multitude of internal events such as blood pressure, hear rate, and body temperature in order to maintain homeostasis.
Image: The Nervous system
Divisions of the Nervous Systema. Central Nervous System(CNS) b. Peripheral Nervous System(PNSCentral Nervous System(CNS)fulfills the function of processing and integration Composed of : i. Brain ii. Spinal CordPeripheral Nervous System(PNS)cable like nerves that are made of bundles of 2 types of neurons that may be CRANIAL NERVES and / or SPINAL NERVES: i. Sensory neurons or Afferent Nerves ii. Motor neurons or Efferent NervesSensory neurons or Afferent Nervescarry input from receptors to the CNSSensory neurons or Afferent Nervescarry input from receptors to the CNS a. Somatic b. VisceralSomaticfrom skeletal musclesVisceralfrom cardiac, smooth muscle and glandsMotor neurons or Efferent Nervestransmit motor output from the CNS to muscles and glands. a. Somatic motor neurons are voluntary b. Autonomic motor neurons are involuntarySomatic motor neurons are voluntarycarry signals to skeletal muscles to make them moveAutonomic motor neurons are involuntarycontrol involuntary activities such as breathing rate, digestion, by activating glands, smooth muscle, and other organs. i. Sympathetic ii. parasympatheticSympatheticexcitatoryparasymlpatheticinhibitoryHistology OF NERVOUS SYSTEM TISSUE / CELLS INVOLVEDA. Neuroglia B. Cells found in the PNS:Neuroglia->nerve glue of the CNSNeuroglia->nerve glue of the CNSNeurogla Function:to support, protect and insulate neuronsNeuroglia1. Astrocyte 2. Microgla 3. Ependymal 4. OlgodendocyteAstrocyte=star shaped; anchor neurons to capillariesMicroglia=ovoid with long processes; macrophage activityEpendymal=ciliated; produce cerebral spinal fluidOligodendrocyte=produce myelin for the CNSMyelin=protects neurons and causes rapid nerve impulsesCells found in PNS1. Schwann 2.SateliteSchwann cells=produce myelin for the PNSsatelite cells=controls chemical environment of neuronsNeurons=highly specialized nerve cells which carry electrical impulses to, from, and within the CNS.Neurons characteristics1. Extreme longevity, can live for 100years or more 2. Amitotic, do not divide 3. High metabolic rate, need a lot of oxygen and glucosecell bodyCell Body, the following are found within the cell body a. Nucleus with no centrioles b. Ribosomes that are very active c. Nissl Bodies=another name for the rough endoplasmic reticulum d. Neurofibrils=intracellular transportneuron processes=cytoplasmic extensions of the cell body a. Dendrites= b. AxonDendrites=conduct impulses towards the cell bodyAxon=conduct impulses away from the cell bodyClassification of Neurons:1. Structure 2. Function:Structure of Neurons p.435a. Multipolar b. Bipolar c. UnipolarMultipolar=more than one structure coming off of the cell bodybipolar cellsonly two structures coming off of the cell bodyunipolar neurononly one structure, that usually bifurcates/divides into two structures later on, coming off the cell body.Function of Neuronsa. Sensory b. Motor c. MixedSensoryinfo from sensory receptors to CNSmotor neuronsinfo away form CNS to EffectorsWhat are stimuli?Things that put our nervous system into action! 1. Temperature Receptors 2. Mechanical Receptors 3. Photo Receptors 4. Chemo Receptors 5. Nociceptorstemperature receptors=sense temperaturemechanical receptors=sense pressure, touch, movementPhoto receptors=sense lightChemo receptors=sense the chemical environment in and outside our bodyNociceptors=sense painNEUROPHYSIOLOGY=One of the above stimuli will trigger a change in the membrane of a neuron. OR simply stimulation of a neuron. 1. A resting neuron is said to be POLARIZED. In this resting state there is more sodium, Na, outside the cell than inside, and there is more potassium, K, inside than outside. 2. Then, the neuron encounters one or more of the 5 stimuli listed above! 3. The neuron is then said to be active and DEPOLARIZED. In this active state, sodium is actively pumped in and potassium is actively pumped out. Actively meaning that this takes ATP! So now there is more potassium on the outside of the cell membrane and more sodium on the inside of the cell membrane.Synapse=where two or more neurons come into close contact; they do not touch, but are separated at junctions called synapses. When a neuron is stimulated a wave of electrical disturbance, nerve impulse, sweeps along at 300ft/sec. At the end/presynaptic terminal of the axon of the neuron is a swelling/synaptic knobs. When the impulse arrives here, it causes the release of neurotransmitter. It is here that a recipient nerve may be stimulated because its dendrites are in "contact" with that neurotransmitter and a nerve impulse is generated in this second nerve.