Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Nervous system


Published on

Published in: Health & Medicine, Business
  • Be the first to comment

  • Be the first to like this

Nervous system

  1. 1. Nervous System Function Neurons Base unit that has very simple function – “decide” whether totransmit signal or not Organization Billions of Neurons (estimates of 100 billion) Very complex interconnections Create systems/circuits that can function independently (parallelprocessing) “Simple decisions” passed to “higher” levels for that addadditional information to create generate more complexdecisions (hierarchical processing) Very expensive - less than 2% of weight but uses 20% ofenergy
  2. 2. Neuron Structure Cell Body Nucleus – genetic information Dendrites Receive information Axon Carry information “long” distances Myelin (Multiple Sclerosis) Axon Terminals Transmit information
  3. 3. Neuron - Structure
  4. 4. Neuron Function Electrical Activity Used to transmit signal within neuron Chemical Activity Used to transmit signal between neurons Synapse – small gap that physically separatesneurons Neurotransmitters – special “chemicals” thatneurons use to transmit message across thesynapse
  5. 5. Neuron Function Electrical Activity Resting Potential Inside negative (-70 mV) compared to outside Inside has high K+ (negativity comes from proteins& other negative ions) Outside has high Na+ Forces at work Electrical Diffusion
  6. 6. Neuron Function Electrical Activity Graded Potential Depolarization – Inside less negative (e.g., Na+ enters) Hyperpolarization – Inside more negative (e.g., Cl- enters) Action Potential When graded reaches approximately -55mV Electrical impulse that travels down cell – axon to axonterminals Axon terminals release neurotransmitter
  7. 7. Neuron Function Electrical Activity Restoring Resting Potential Sodium-Potassium Pump – moves Na+ out of celland K+ into cell This requires cell to use energy
  8. 8. Neuron Function Chemical (Neurotransmitter) Activity Leads to graded potentials in neuron Excitatory NTs – causes depolarization in neuron Initiatory NTs – causes hyperpolarization inneuron
  9. 9. Neuron – Excitation & Inhibition
  10. 10. Neuron - Synapse
  11. 11. Synapse Types Multiple ways of connecting Examples Axon to Dendrite – excite or inhibit neuron Axon to Axon Terminal – moderate NT release Axon to Extracellular Space or blood – potentialfor diffuse effects
  12. 12. Synapse Types
  13. 13. Synapse Function Neurotransmitter cycle in Axon Terminals Synthesis Storage Release Inactivation Reuptake Degradation Neural transmission problems if cycle disrupted(e.g., drugs) at any step
  14. 14. Synapse Function
  15. 15. Synapse Function
  16. 16. Neurotransmitter Types Small Molecules Nine – Acetylcholine (ACh), dopamine (DA),norepinephrine (NE), epinephrine (adrenaline), serotonin(5-HT), histamine, GABA, glycine, glutamate Simple (or no) alterations to basic food components Glutamate & glycine are amino acids DA and NE from tyrosine & 5-HT made from tryptophan Manufactured in axon terminals Large quantity and have short duration
  17. 17. Note: There are four criteria by whichneurotransmitters are defined. 1. It must be synthesized in thepresynaptic cell.2. It must be released by the presynapticterminal in sufficient quantities to producea measurable effect on the postsynapticcell.3. When administered artificially, it mimicsnatural release.4. A specific, known mechanism exists forit to be removed from the synaptic cleft.
  18. 18. Acetylcholine (ACh)• -Arousal and orgasm- voluntary muscular control and propertone- enhance energy and stamina- memory- long-term planning- mental focus
  19. 19. dopamine (DA) - Alertness- Motivation- motor control- immune function- Ego hardening,confidence, optimism- Sexual Desire- Fat gain and loss- lean muscle gain- Bone density- ability to sleep soundly- Inhibits prolactin- thinking, planning, andproblem solving- Aggression- Increase psychic andcreative ability- Reduction ofcompulsivety- Salience and paranoia- Processing of pain- Increase sociability
  20. 20. norepinephrine (NE) - Increase physicalenergy- Reducecompulsivety- Increase heart rate- Increase BP- Aggression- Alertness- Wakefulness/sleepcycle- Memory and learning- Orgasm- Decrease blood flow toextremities- Increase heart rate- Maintenance ofattention- Cerebral plasticity
  21. 21. epinephrine (adrenaline) - increases supply of oxygen and glucoseto brain and muscles- Surpresses digestion- Increase heart rate and stroke volume- Pupil dilation- constricts arterioles in skin and GI tract- Dilates arterioles in skeletal muscles- Elevates blood sugar levels
  22. 22. serotonin (5-HT) - Decrease thought- Anaesthesize emotions- Decrease Agression and anger- Decrease Anxiety- Promote satiety and decreaseappetite- Elevates Pain threshold- Reducescompulsivety/impulsivety- Decrease Sexual Desire- Thermoregulation (5-HT1A)- Stimulate Emesis (5-HT3)- Cerebrospinal fluid secretion (5-HT2C)- Platelate aggregation (5-HT2A)- Smooth muscle contraction,vasoconstriction, and vasodilation (5-HT2A)- Release oxytocin (5-HT1A)- Learning (5-HT2A & 5-HT4)- Memory (5-HT4)- Neuronal excitation (5-HT2A, 5-HT3,& 5-HT4)- GI motility (5-HT4)- Neuronal inhibition (5-HT1A)- Cerebral vasoconstriction (5-HT1D)- Pulmonary vasoconstriction (5-HT1B)- Presynaptic inhbition (5-HT1B)
  23. 23. histamine H1- Vasodilation- Bronchoconstriction- Smooth muscle activation- separation of endothelial cells (responsible for hives)- Pain and itching due to insect stings- Allergic rhinitis- Motion sicknessH2- stimulates gastric acid secretion- Potent stimulant of cAMP production- increases the intracellular Ca2+ concentrations and release Ca2+ from intracellularstores.H3- presynaptically inhibits the release of a number of other neurotransmittersincluding, but probably notlimited to dopamine, histamine, GABA, acetylcholine, noradrenaline, and 5-HT. Itleads to inhibition of the formation of cAMPH4- H4 Receptors mediate Chemotaxis and Calcium Mobilization of Mast Cells
  24. 24. GABA - synthesized from glutamate - Reduce physical tension- Reduce Anxiety- Reduce Insomnia- Elevates pain threshold- Reduces blood pressure- Decrease heart rate- Reduce compulsivety
  25. 25. GlycineGlutamate and Aspartate excitatory neurotransmitters
  26. 26. Neurotransmitter Types Peptides 50+ and grouped into families depending on function Opoids (enkephalins, dynorphin) – pain Gastrins (gastrin, cholocystokinin) – food digestion 2 or more amino acids and made in cell body (ribosomes)from DNA instruction Slower to manufacture & transport Small concentrations and longer durations Gases At least 2 – nitric oxide (NO) & carbon monoxide (CO) Can work on releasing cell
  27. 27. Neurotransmitter Function No one to one relation between type andfunction Same NT can be used in different places withvery different effects Acetylcholine – contracts muscles, used inautonomic nervous system, and brain
  28. 28. Neurotransmitter Receptor Proteins Channel Proteins NT binding site and channel trough membrane NT opens a channel to allow chemical flow (Na+) acrossmembrane Second Messengers NT binding site – NT activates a “second messenger” (1stis the NT) inside the cell Change function of cell (e.g., change protein production topermanently alter cell function for learning)
  29. 29. Neurotransmitter Receptor Proteins
  30. 30. Neurotransmitter Receptor Proteins Usually multiple receptors for a given NT Acetylcholine Nicotinic receptor – found a junction betweenneuron and muscle Muscarinic receptor – more prevalent in brain Acetylcholine affects both Drugs can have more specific effects (or notdepending on the drug) Nicotine & curare –affect nicotinic but not muscarinic
  31. 31. Neurotransmitter Receptor Proteins Usually multiple receptors for a given NT Serotonin (5-HT) 13 known receptors grouped into 6 families People with schizophrenia have an excess of onetype Demonstrates how genetic differences can influencemotivational temperaments Dopamine 5 known receptors grouped into 2 families
  32. 32. Psychoactive Drug Overview Two Broad effects on NT function Facilitate or increase function of a specific NT Inhibit or Decrease function of a specific NT 2 Broad effects accomplished by alteringany of the 7 synapse functions (previousslide) Acetylcholine
  33. 33. Psychoactive Drug Overview Acetylcohine Example Axon Release Black widow spider venom – released from axon terminals Botulinum toxin (Botox) – blocks release from axonterminals Synapse Stimulation Nicotine – mimics ACh Curare – blocks ACh from getting to terminals Inactivation Physostigmine – blocks effect of enzyme that destroys ACh
  34. 34. Psychoactive Drug Overview
  35. 35. Psychoactive Drug Overview Nervous System adapts drug presence Inhibitory drug – may create more proteinreceptors to detect smaller amounts of NTs thatare getting to postsynaptic cell Excitatory drug – may remove protein receptors NS now requires drug for functioning Inhibitory drug – “normal” signals are too strong Excitatory drug – “normal” signals not strongenough
  36. 36. Nervous System Organization
  37. 37. Nervous System Organization Central Nervous System (CNS) Spinal Cord – simple decisions & information transmission Brain – “complex” decisions Peripheral Nervous System (PNS) Somatic – sensory information & voluntary movement Autonomic Sympathetic – increases support increased physical activity Parasympathetic – increases support decreased physicalactivity Enteric – gastrointestinal system
  38. 38. Autonomic Nervous System
  39. 39. Nervous System Organization Neuron Groups Peripheral NS Nerve – collection of axons in PNS Ganglia – collection of cell bodies & dendrites Central NS Tract – collection of axons in CNS (White Matter) Nuclei – collection of cell bodies (Grey Matter) Glial Cells Support and assist neurons (many types) Produce myelin, nourishment, repair, waist disposal, etc.
  40. 40. Spinal Cord 31 segments with pairs (left & right) nervescarrying sensory and efferent information Functions Ascending and descending neural tracts Interneurons responsible for spinal reflexes(relatively simple decisions) Link sensory information (e.g., pain) with motorresponse (e.g., muscle contraction)
  41. 41. Brain Structure Very Complex Many different ways of describing brainstructures (location, function, etc.) General Principles Layered Lateralized
  42. 42. Brain Neural Systems Brain circuits responsible for brain function E.g., - vision, hearing, movement, reward System could be Localized (vision) or diffuse (arousal) General (vision) or specific (color vision) Broad Divisions Sensory Motor Association
  43. 43. Brain Complex behaviors (fear/defensive learning)depend on many systems Sensory Learning Memory Output Differences in a function (e.g., motivation) mightbe due to different reasons (e.g., sensory,learning, etc.)
  44. 44. Studying Brain Function Gross lesions Structural assessments Selective lesions specific neurotoxins transient lesions Local functioning Single-cell recording Neurotransmitter measurement & manipulation Gene expressions Non-invasive measures Functional MRI EEG & ERP