3Functionssense changes in internal and external environment via sensory receptorsanalyze sensory information, store information and decision making processesrespond to stimuli via muscles glands or other nerves
4Organization Central nervous System (CNS) brain spinal cord Peripheral nervous System (PNS)cranial nervesspinal nervessensory and motor componentsgangliareceptorsPeripheral Nervous System Subdivisionssomatic nervous system - voluntaryautonomic nervous system (ANS) - involuntarysympathetic divisionparasympathetic divisionenteric nervous system - enteric plexi throughout GI tract
6Autonomic Nervous System • Responsible for involuntary visceral motor activity• conducts impulses from the CNS to• cardiac muscle• smooth muscles• glands• Two DivisionsSYMPATHETICEngages body systems during activityPARASYMPATHETICConserves energyantagonist of sympathetic system
7Enteric Nervous System • Sensory receptors and neurons located in GI tract and enteric plexuses• Involuntary motor neurons in the enteric plexuses• Effects smooth muscle, gastroitestinal and endocrine glands of the GI tract
8Cells of the Nervous System • Supporting cells - neurogliasmaller thean neuronscomprise 1/2 mass of the brainapproximately 10x more numerous than neurons• Neurons
9Astocytes NEUROGLIA most abundant contains radiating processes that adhere neurons to nearby blood capillariesmake exchanges between capillaries and neuronsguide developing neuronsaid in synapse formationaid in cleaning up leaked K ionsrecapture neurotransmittersaid in information processing in the brain
10Microglia NEUROGLIA contains thorny extensions function to monitor health of nearby neuronsmigrate towards injured or unhealthy neuronsconverts macrophages to destroy/remove neuronal debris and microorganismsonly protecting within the CNS
11Ependymal Cells NEUROGLIA shaped from squamous to columnar some ciliatedlocated in the central cavities of brain and spinal cordform a permeable barrier between the CSF of these cavities and surrounding tissue
12Oligodendrocytes NEUROGLIA similar to astrocytes position themselves along thick neuron fibers in CNSwrap processes around neuronproduce insulating myelin sheaths
13Satellite & Schwann Cells NEUROGLIASatellite & Schwann Cellsboth located in the PNSSatellite cells surround neuron cell bodies with unknown functionSchwann cells are also called neurolemmocytesthese surround the myelin sheathaid in the formation of myelin similar to oligodendrocytesaid to repair damaged PNS nerve fibers
14THE NEURON Functional cell of the nervous system transmit and conduct impulses from one part to anotherfound asafferent or sensoryefferent or motorinternuncial or associationCHARACTERISTICSlongevity - with adequate nutrition will last a lifetimeamitotic - once fucntional they lose the ability to divide and cannot be replaced...EXCEPTolfactory epitheliummemory cells o the hippocampusretain a high metabolic rate - require continuous and abundant supplies of glucose and oxygen
16cell bodydendritesaxon collateralnucleusaxonhillockneurofibrilsneurilemmanissl bodiesaxon cylindermyelin sheathnode of Ranvieraxon terminalssynaptic end bulbs
17DCBDDCBAXAXAXCBATATATMultipolarUnipolarBipolarone dendrite; one axon; fond in retina if eye, inner ear and olfactory area of the brainbegin as bipolar in fetusmultiple dendrites; one axon; found in brain and spinal cord
18Kinesin Movement Review References ReviewReferences
20Ion channels control the movement of ions through the neuronal cell membrane. Ion channels are selectivepassive or activeregionally locatedfunctionally unique
21Selective Ion Channels Selective channels select ions for passage based on the charge of the ion, the size of the ion and how much water the ion can attract and hold around it
22Ion Channels Ion channels are either active or passive Active channels have gates that either open or close the channelpassive channels or leakage channels are always open and allow ions to flow continuously. These channels are located throughout all parts of the neuron.
23Voltage Regulated Channels When a neuron is at rest the voltage regulated gates are closed.During an action potential, the voltage across the membrane changes with the flux of Na-K causing the voltage channels to open and closeIons move through open channelsFound in axon hillock, nodes of Ranvier, all along unmyelinated axons
24Chemically Regulated Channels or Ligand Gates Some neurons have active channels that contain chemically controlled gates.Neurotransmitters such as acetylcholine (ACH) and GABA bind to chemically gated channels causing them to open. This then permits ions to move across the membrane. Located on dendrites and cell body.
25Uniqueness of Ion Channels Passive channels are responsible for resting membrane potentialPassive channelsChemically gated channels are responsible for synaptic potentials or the incoming signals to a neuronChemically gated channelsVoltage gated channels are responsible for the generation and propagation of an action potential - the outgoing signal from the neuronVoltage gated channels
34ELECTRICAL SYNAPSESWhen one neuron forms a gap junction with another neuron, an electrical synapse is made. Electrical current in the form of ions, flows directly from one neuron to another through the gap junction. These synapses are ALWAYS excitatory
35CHEMICAL SYNAPSESat a chemical synapse the neuronal membranes are separated by a gap called the synaptic cleft. Electrical current CANNOT flow directly from one neuron to another. A chemical called a neurotransmitter is released from the sending neuron and carries the signal to the next neuron.
36Parts of the Chemical Synapse postsynaptic neuronsynaptic cleftSynaptic vesiclespresynaptic neuron
38voltage gated Ca channel 1. impulse moves down neuron to axon terminalnerve impulseimpulse reaches voltage gated Ca channels and the wave of depolarization causes gate to open and Ca ions to move inCa influx recruits synaptic vesicles to migrate to presynaptic neurons membranevoltage gated Ca channelsynaptic vesiclessynaptic cleftneurotransmitterspostsynaptic neuron
39synaptic vesicles release neurotransmitter into synaptic cleft neurotransmitteractivates channel to open and causes an influx of Na ions triggering an postsynaptic action potentialneurotransmitters attaches to specific receptor sites on closed ligand gated channelpostsynaptic neuron
57Serial Processingwhole system works in a predictable all-or-nothing manner.One neuron stimulates the next, which stimulates the next, and so on, eventually causing a specific, anticipated response.examples of serial processing are spinal reflexes, andstraight-through sensory pathways from receptors to the brain
58Parallel Processinginputs are segregated into many pathways, and information delivered by each pathway is dealt with simultaneously by different parts of the neural circuitry.smelling a pickle (the input) may cause you to remember picking cucumbers on a farm; or it may remind you that you don’t like pickles or that you must buy some at the market; or perhaps it will call to mind all these thoughts.For each person, parallel processing triggers some pathways that are unique.The same stimulus—pickle smell, in our example—promotes many responses beyond simple awareness of the smell.Parallel processing is not repetitious because the circuits do different things with the information, and each “channel” is decoded in relation to all the others to produce a total picture.
60Neurotransmitters Acetylcholine Glutamate Major NT found in PNS neuromuscular junction where it excites skeletal muscle, and inhibits cardiac muscleis also found in the CNSis degraded via acetylcholinesteraseGlutamateMost common excitatory NT in the CNSremoved by active pumping back into the presynaptic end bulbGamma amino butyric acid (GABA)Most common inhibitory NT in the CNSAnti-anxiety drugs enhance the action of GABANorepinephrineIn the brain NE effects sleep and moods.In the PNS, NE and epinephrine are main neurotransmitters of sympathetic postganglion synapsesNE and epinephrine are also produced by the adrenal glands and are responsible for flight or flight responsesthis is a biogenic amine and is degraded enzymatically by monoamine oxidaseDopamineFound in the brain is involved in emotional responses and skeletal muscle movementthis is a biogenic amine and is degraded enzymatically by monoamine oxidaseSeratoninFound in the brain is involved in temperature regulation, sleeping, sensory perception and moodsthis is a biogenic amine and is degraded enzymatically by monoamine oxidase
61Neurotransmitters Continued Neuropeptideswidespread throughout CNS and PNSsome act as hormonesEndorphins and Enkephalinsinvolved in natural pain killingbiochemical derivatives of morphine and heroinproduce euphoric effectsNitric Oxideis not produce by vesicles like other NEis lipid soluble and diffuses out of the neuronacts to cause changes in cellular enzymes instead of a membrane receptorcauses blood vessel vasodilationPhagocytes release NO in higher toxic levels to destroy invading cells
62Neurotransmitter Removal NT removal is absolutely necessary for normal synaptic function.If the NT lingers at the postsynpatic neuron, muscle fiber or gland it would cause continuous stimulation of the postsynaptic neuron.NT are removed viaDiffusion - some NT naturally diffuse away from receptors after their action closing the gatesEnzymatic degradation - most NT are degraded by enzymes released at the postsynaptic neuron. Enzymes are released once the gate has been activatedUptake by cells - many NT are actively transported into the neuron that released them via neurotransmitter transporters.Some NT are blocked from reuptake by therapeutic drugs. Neuromodulators as Welbutin and Prozac are selective seratonin reuptake inhibitors (SSRI). By preventing reuptake, stimulation is prolonged.