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Human Physiology Exam 1 Study Guide

by: MBattito

Human Physiology Exam 1 Study Guide BIOL 3160

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GPA 3.5

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This is a detailed outline with notes from Dr. McNutt's lectures, her power point notes, and supplement information from the text book for chapters 1, 6 and 7 that will be covered on our first exam...
Human Physiology
Dr. Tamara McNutt-Scott
Study Guide
Human Physiology
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This 32 page Study Guide was uploaded by MBattito on Friday January 29, 2016. The Study Guide belongs to BIOL 3160 at Clemson University taught by Dr. Tamara McNutt-Scott in Fall 2015. Since its upload, it has received 203 views. For similar materials see Human Physiology in Biological Sciences at Clemson University.


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Date Created: 01/29/16
Test  1  Study  Guide:       Chapter  1:     Physiology:     • Fundamentally  represents  the  study  of  how  living  organisms  work   o Molecules  à  cells  à  tissue  à  organ  à  organ  system   o How  organisms  accomplish  tasks  essential  for  life   • Function  and  integration   o Body  parts  work  together  at  various  levels  of  organization  and  whole   organism   o No  “part”  works  in  isolation   • Mechanisms  and  their  effects   o Sequence  of  events  à  parts  of  larger  stories   • Misconception:  all  is  known   History  of  Physiology:   • Aristotle:     o Speculated  on  function  of  human  body   o Good  health  associated  with  balance  of  humours   § Humours:  black  bile,  yellow  bile,  phlegm  and  blood   • Erasistratus:  “father  of  physiology”   o Applied  physical  laws  to  study  of  human  body   o Studied  cardiovascular  and  nervous  systems   o Performed  dissections  on  live  humans  à  noted  increase  in  heart  rate   • William  Harvey:     o First  to  study  biology  quantitatively   o One  of  the  first  to  be  able  to  accurately  describe  the  parts  of  the  body   and  systematic  circulationà  identified  parts  and  their  functions   • Claude  Bernard:  “father  of  modern  physiology”   o Observed  the  milieu  interieur   o Found  that  animals  possess  control  systems  that  could  adjust  to   external  and  internal  stimuli   o Internal  environment  remains  remarkably  constant  despite   constantly  changing  external  environment   Father  of  American  Physiology:  Robley  Dunglison   • In  the  early  19  century  in  the  US  physiology  was  treated  as  an  aspect  of   theory  and  practice  of  physics   • 1824:  Thomas  Jefferson  and  the  board  members  of  the  University  of  Virginia   added  Dunglison  to  the  first  faculty  of  the  U  of  VA   • Dunglison:   o English  physician     o Professor  of  Anatomy,  Physiology,  Surgery,  Materia  Medica,  Pharmacy   and  History  of  Medicine   o Teaching  was  an  explanation  of  “successive  theories”   o Published  several  books  and  articles   § Human  Physiology  (1832)  à  landmark  text   Homeostasis  and  Feedback  Control:   • Homeostasis:  maintenance  of  a  relatively  stable  internal  environment   o Basically  represented  by  the  state  of  equilibrium  of  the  body’s  internal   environment  by  dynamic  processes  of  feedback  and  regulation   o Reason  for  regulatory  mechanisms   o Is  not  an  easy  accomplishment   § Every  organ  system  is  involved  with  the  maintenance  and   necessitates  integrated  function   o Major  foundation  for  medical  diagnostic  procedures   • Walter  Cannon:  coined  the  term  homeostasis  in  his  book,  The  Wisdom  of  the   Body   • How  is  the  maintenance  of  homeostasis  accomplished?  Feedback   mechanisms   Feedback  Mechanism:  maintain  homeostasis   • Set  point:  normal  range  of  measurements  and  values   o Variable:  factor  or  event  being  regulated     • Control  systems  that  promote  homeostasis  are  characterized  by  3   interdependent  components:   o Receptor:  serve  as  sensors  to  determine  what  is  out  of  balance   § Uses  afferent  pathways  (sensory  pathways  toward  central   nervous  system)   o Control/integrating  center:  uses  efferent  pathways  (motor  pathways   away  from  central  nervous  system)   o Effector:  bring  balance  back   • Why  is  it  referred  to  as  a  “loop”?     o “Loop”  emphasizes  feedback  mechanism  is  a  continuous  cycle  to   maintain  homeostasis   • Is  our  internal  environment  absolutely  constant?    Are  we  always  in  a  state  of   balance?   o Our  internal  environment  is  not  absolutely  constant.  We  maintain  a   dynamic  balance  or  consistency;  that  is  overall  our  body  is  constant   within  a  range  but  is  not  absolutely  constant.  Conditions  stabilize   around  a  set  point;  they  must  be  in  the  range  so  physiological   processes  can  run  efficiently.   Negative  Feedback  Mechanism:  reverse  direction  control  mechanism   • Most  common  homeostatic  control  mechanism   • Works  because  output  of  system  causes  a  decrease  or  shuts  off  the  original   stimulus   o Continuous,  ongoing  processes   • All  negative  feedback  mechanisms  have  the  same  goal:  preventing  sudden,   severe  changes  in  the  body   • Antagonistic  effects:  effectors  have  antagonistic  actions,  allowing  for  finer   degree  of  control   • Integration  center  does  not  always  have  to  be  in  the  central  nervous  system   Positive  Feedback  mechanism:  same  direction  control  system   • Enhance  or  exaggerate  the  response  over  the  original  stimulus,  thus  the   output  is  increased   • Usually  control  episodic  or  infrequent  events  that  do  not  require  continuous   adjustments   o Ex:  blood  clotting,  breast  feeding,  parturition  (child  birth)   • Limited  occurrence  because  it  proceeds  with  very  little  control   Homeostatic  imbalance:   • Places  an  individual  at  higher  risk  of  disease   • Typically  a  result  of  certain  pathological  conditions  and  aging   Homeostatic  Regulation:   • Regulatory  mechanisms  for  homeostasis   o Intrinsic:  within  organ   o Extrinsic:  “outside”  organ   § Nervous  system:  impacts  homeostasis  via  nerves   § Endocrine  system:  impacts  homeostasis  via  hormones   • Advantages:  self  regulatory  and  self  initiated     Disadvantages:  automatic  response  sometimes  does  not  help     Cells:  basic  unit  of  structure  and  function   • Simplest  structural  unit  that  complex,  multicellular  organisms  can  be  divided   into     • Smallest  unit  of  life   • Retain  functional  characteristics  of  lfie   Tissues:  cells  with  similar  functions   • 4  Primary  tissue  types:   o Connective   o Muscle   o Nervous     o Epithelial     Organ:  2+  primary  tissues  grouped  into  anatomical  and  functional  units   • Typically  all  4  types  of  tissue  presents   • Activities  and  interactions  of  tissues  determine  physiology  of  organ   Muscle  Tissue:  3  types  specialized  for  contraction   1.)  Skeletal  Muscle:  generally  attached  to  a  bone  via  a  tendon;  the  tongue  is   the  exception   o Skeletal  muscle  cells  referred  to  as  myofibers   o Form  in  the  4  week  of  development  as  myoblasts   § Myoblasts  fuse  together  making  skeletal  muscle  multinucleate   o Arranged  in  bundles  which  vary  in  strength   § Perform  graded  contractions  controlled  individuallyà  allow  us   to  change  the  degree  of  strength  and  finer  degree  of  movement   o Striated     • Cardiac  Muscle:  Found  in  the  wall  of  the  heart   o Cardiac  muscle  cells  referred  to  as  myocardial  cells   o Form  a  continuous  sheet   § Uninucleated   § Referred  to  as  branched   § Striated  as  a  result  of  the  interactions  between  the  contractile   elements  (actin  and  myosin)   o Intercalated  discs:  couple  cells  mechanically  and  electrically     • Smooth  Muscle:  Found  in  GI  tract   o Nonstriated,  fusiform  shape   § Still  has  actin  and  myosin,  just  different  interactions  between   them  that  do  not  form  striations   o Forms  a  sheet  arranged  circularly  and  or  longitudinally     o Performs  peristalsis:  wave-­‐like  contractionsà  specifically  in  areas   like  the  lumen   What  type  of  muscle  is  termed  voluntary  muscle?     à  Skeletal  muscle;  because  it  must  be  consciously  initiated  to  move   What  type  of  muscle  is  termed  involuntary?   à  Cardiac  and  smooth  muscle;  they  are  under  the  control  of  the  autonomic  nervous   system  –  they  do  not  have  conscious  control     Nervous  Tissue:     • Consists  of  neurons  and  supporting  cells   o Neurons:  highly  specialized  to  generate  and  conduct  nerve  impulses   à  an  electrical  event   § Constructed  of  a  cell  body  (soma),  dendrites  and  an  axon   • Can  have  multiple  dendrites  but  only  one  axon   • Each  has  structural  attributes  and  functions   § Cannot  divide     o Support  Cells:  Non-­‐conducting  cells  that  support,  insulate  and  protect   neurons   § AKA  neuroglial  or  glial  cells   § Main  function  is  to  make  sure  the  neurons  work  as  efficiently   as  possible   § More  abundant  than  neurons   § Limited  ability  to  divide   Epithelial  Tissue:  cover  body  surfaces  and  line  body  cavities   • Perform  a  variety  of  functions  but  primarily  serves  as  a  boundary   • Classified  according  to  number  of  layers  and  shape   o Layers:   § Simpler:  1  layer  of  cells   § Stratified:  multiple  layers  of  cells   o Shapes:     § Squamous   § Columnar   § Cuboidal     Epithelial  tissue  serving  as  a  barrier   • Site  of  regulation  for  substances  entering/leaving  body   • To  be  effective  it  must  be  able  to  be  sealed  off  à  junctional  complex   o Junctional  complex  seals  off  epithelium  at  lumen  allowing  it  to  be  a   barrier   § Composed  of  a  tight  junction,  adhering  junction  and  a   desmosome   § What  allows  us  to  regulate  the  entrance  and  exit  of  substances   from  the  cell     Glands:   • Formed  by  epithelial  tissue  growing  down  into  the  connective  tissue   o Exocrine  gland:  forms  from  a  cord  or  tubule   § Has  a  duct  and  a  secretory  portion   o Endocrine  gland:  forms  from  a  cluster  of  cells     § Has  a  secretory  portion  but  no  duct   Exocrine  Glands:     • Components:     o Duct   o Secretory  unit:   § Acinus   § Myoepithelial  cells:  surround  acini   • Classified  by:   o Number  of  ducts:     § Simple  (1  duct)   § Branched  (many  ducts)   o Type  of  secretory  portion:   § Tubular   § Acinar/alveolar     Connective  Tissue   • Characterized  by:   o Large  amount  of  extracellular  material  in  the  spaces  between   connective  tissue  cells   § Extracellular  matrix  is  made  up  of  fibers  and  ground   substances;  varies  in  composition  arrangement  between  tissue   types   • Fibers:  collagen  fibers,  elastic  fibers  and  fibroblast   • Ground  substances:  interstitial  fluid,  cell  adhesion   protein,  glycocalyx     o Comprised  of  varied  cell  types   • Categorized  into   o Connective  tissue  proper:  loose  and  dense  connective  tissue   o Supportive  connective  tissue:  bone  and  cartilage   o Liquid  connective  tissue:  blood   Stem  cells:   • Tissues  of  an  organ  are  comprised  of  differentiated  cells   o Highly  specialized   • Differentiation  begins  during  embryonic  development   o Zygote/embro:  one  celled  structure;  fertilized  egg   § Contains  totipotent  stem  cells  à  the  least  differentiated;  can   form  any  tissue  type   o Blastocyst-­‐implantation   § Pluripotent  stem  cellsà  capable  of  forming  unrelated  cell   types   o Trilaminar  embryo     § Ectoderm,  mesoderm  and  endoderm   • Ives  rise  to  4  primary  tissue  types   • Adult  stem  cells   o Multipotent:  form  related  cell  types   Hierarchical  system  to  structural  organization   • Levels  of  cellular  organization   • Human  body  is  a  complex  society  of  differentiated  cells,  which  combine   structurally  an  functionally  to  carry  out  life-­‐sustaining  processes   • Cells  basic  units  of  the  society  and  almost  all  exhibit  fundamental  activities   common  to  all  forms  of  life   • One  big  community  and  if  any  one  part  starts  having  problems,  everything   else  will  be  affected   o Reliant  and  restricted  by  what  is  found  below  it   Body  Fluid  Compartments:   • Extracellular  fluid:     o Fluid  in  blood  and  spaces  that  surround  cells   § Found  in  plasma   § Also  found  in  interstitial,  or  tissue  fluid  à  between  the  cells   themselves   • Intracellular  fluid   o Fluid  within  cells   • Mainly  comprised  of  water   o Aqueous  compartments   o Properties  of  water  have  significant  impact  on  functional   characteristics   • Compositions  varied  between  compartments   o Extracellular  fluid  considered  to  be  more  “homogenous”  than   intracellular  fluid   § Cells  have  specific  functions  so  there  is  more  variability  in  cell   types;  in  extracellular  fluid  there  is  more  exchange  between   them   • What  organ  plays  an  important  role  in  extracellular  fluid   composition/volume?   o Kidneyà  filters  blood  and  eliminates  water  to  impact  and  modify   volume   • Compartmentalization:  ability  to  have  barriers   • Who  serves  as  the  “barriers”?   o Epithelial  tissue  and  plasma  membrane   • Properties  of  the  barriers  determine  what  moves  between  the  compartments     Chapter  6:  Interactions  Between  Cells  and  the  Extracellular  Environment     • Extracellular  environment  represents  all  constituents  outside  the  cell   Why  is  the  extracellular  matrix  so  important?   • This  is  where  cells  obtain  the  nutrients  they  need  and  release  their  secretions   (biproducts  of  their  chemical  processes)   • They  eliminate  their  wastes  to  be  processed  accordingly   • Impact/interact  with  neighboring  cells,  different  tissues  and  different  organs   Body  Fluids:   • Divided  into  compartments:   o Extracellular:   § Blood  plasma  and  interstitial  fluid   § 33%  of  body  fluids   o Intracellular:   § Within  cells   § 67%  of  body  fluids   • Fluids  serve  as  communication  link  between  cells,  tissues  and  organs   Extracellular  Matrix   • Complex  network  of  proteins   o Specific  for  any  given  tissue  à  not  generic   • Extracellular  fluid  interspersed  within   • Functions:   o Scaffolding  for  cellular  attachment   o Transmits  information  to  regulate  activity,  migration,  growth  and   differentiation     • Composed  of  fibrous  proteins  and  ground  substances   o Ground  substances:  analogous  to  a  hydrated  gel  and  location  of   interstitial  fluid   § Comprised  of  glycoproteins  and  proteoglycans     • Highly  functional,  complex  organization  of  molecules  chemically  linked  to   extracellular  protein  fibers  and  glycoproteins  of  glycocalyx   • Integrins:  adhesion  molecule  between  cells  and  extracellular  matrix   o Physically  joins  extracellular  and  intracellular  compartments   o Serve  to  relay  signals  or  integrate  them  à  communication  element   • Block  integrin:  block  functions  of  integrins   o Example:  found  in  snake  venom;  binding  site  on  platelets  which  slows   blood  clotting   Transport  across  the  plasma  membrane   • Plasma  membrane:   o Serves  as  a  “barrier”  to  movement  –  extracellular  and  intracellular   compartments   o Selectively  permeable  à  dynamic;  ability  to  change  permeability   • Membrane  transport  processes   o Passive  transport:  does  not  require  energy   § Ex.  Diffusion:  flow  along  a  concentration  gradient  from  high  to   low   o Active  transport:  require  energy   o Carrier-­‐mediated  transport:  requires  a  carrier  protein   Diffusion  and  Osmosis   • Molecules  of  a  solution  are  in  constant  motion   • Solvent:  what  the  particle  is  dissolved  in   • Solute:  the  particle  being  dissolved   • Osmosis:  diffusion  of  water  to  reach  equilibrium  between  concentration   gradients   o Mass  net  movement  of  water  from  high  water  concentration  to  low;   however  still  some  small  movement  from  low  to  high   • Mean  diffusion  time:  time  to  reach  equilibrium   o Increases  with  distanceà  distance  kept  within  100micrometers  for   effective  exchange   § Beyond  100  micrometers  our  bodies  cannot  effectively   transport  material  fast  enough   Diffusion  through  a  plasma  membrane     • Nonpolar  molecules:   o Oxygen  gas     o Steroids   • Small  polar  covalent  molecules  without  charge   o Carbon  dioxide   o Ethanol   o Urea   • Ability  of  these  molecules  to  cross  easily  allows  for  efficient  cellular   respiration   o Our  environment  is  always  oxygen  rich  so  it  can  freely  flow  into  cells   and  carbon  dioxide  can  easily  exit   Membrane  channels   • Used  for  charge  inorganic  ions  such  as  sodium  and  potassium     • Can  be  open  or  gated   • Gated  channels  have  the  ability  to  open  or  close   o Allows  a  degree  of  regulation   o Regulated  by  particular  physiological  stimuli     • For  large,  polar  molecules,  carrier  proteins  are  needed  in  the  plasma   membrane  for  movement   Rate  of  Diffusion:  speed  of  diffusion  per  unit  time   • J=PA  (C -­‐C )   0 i o J  represents  the  net  flow   o (C -­‐0) i  represents  the  concentration  gradient   o A  represents  the  surface  area   o P  represents  the  membrane  permeability  coefficient   • Factors  effecting  rate  of  diffusion:   o Magnitude  of  concentration  gradient   o Diffusing  substance’s  permeability  to  plasma  membrane   o Temperature  à  rate  increases  as  temperature  does   o Surface  area  availability   § Ex.  Microvilli  increase  surface  area  to  assure  there  is  enough   space  for  diffusion  to  be  run  efficiently   o Distance   • Magnitude  of  concentration  gradient  is  the  driving  force  for  diffusion,  but   will  not  move  if  plasma  membrane  is  not  permeable  to  that  molecule   Osmosis   • Net  diffusion  of  water   o Follows  a  concentration  gradient   • Requirements:     o Concentration  difference  of  solute  between  sides  of  membrane   o Membrane  selectively  impermeable  to  solute   § Non-­‐penetrating  solute  à  cannot  move  across  membrane   § Osmotically  active:  creates  osmotic  pressure  (“pull”  of  water   via  a  solute)   o Essentially,  solute  cannot  cross  the  membrane,  so  equilibrium  must   be  reached  by  movement  of  water  instead  of  solute  to  alter  the  solute   concentration   • Aquaporins:  open  water  channels   o Facilitate  movement  of  water   o Present  in  some  cell  types  or  can  be  inserted  in  response  to  regulatory   molecules   Osmotic  Pressure   • Represents  the  pressure  that  must  be  applied  to  a  solution  to  prevent  the  net   flow  of  water   • Indicates  how  strongly  a  solution  draws  water   • Water  drawn  more  rapidly  with  greater  solute  concentration     Molarity  vs.  Molality   • Molarity:  ratio  of  solute  to  volume  of  solution   o Ratio  of  solute  to  solvent  not  completely  specified   o Amount  of  water  changes  due  to  the  molecular  weight  of  substances   • Molality:  ratio  of  solute  to  solvent   o Better  measurement  of  concentration  when  discussing  osmosis   o Compares  compartments  (solute  and  solvent)  better   Osmolality:     • Osmotic  pressure  depends  on  the  ratio  of  solute  to  solvent,  not  chemical   characteristics  of  solute     o Therefore  osmolality  is  more  appropriate  (Osm)   § Total  molality  of  a  solution   • Electrolytes  will  ionize  in  water  and  therefore  alter  the  concentrations   • Blood  plasma  and  other  biological  fluids  have  a  complex  osmolality  due  to   the  presence  of  organize  molecules  and  electrolytes   o Cell  activity  leads  to  constant  change   Tonicity:   • Describes  effect  of  solution  on  osmotic  movement  of  water,  thus  cell  shape   and  volume   o Solute  load  (normal  osmolality)=300mOsm   • Solutions  describes  by  how  they  change  cell  volume  (and  thus  shape)  by   causing  water  movement     • Take  into  account  both  solute  concentration  and  solute  permeability  for  each   solute  crossing  the  plasma  membrane   • Examples:  using  a  300mOsm  cell  placed  in  the  following  solutions:   o 400mOsm  solution:  water  will  flow  out  because  it  is  in  a  hypertonic   solution  à  cell  will  shrink   o 300mOsm  solution:  there  will  be  no  net  movement  because  it  is  in  an   isotonic  solution  à  cell  size  remains  the  same   o 200mOsm:  water  will  flow  into  the  cell  because  it  is  in  a  hypotonic   solutionà  cell  will  swell   When  a  cell  comes  in  contact  with  a  solution,  hypertonic  or  hypotonic,  the  initial   concentration  of  solutes  determines  the  degree  of  change   • If  a  cell  were  placed  in  a  solution  containing  100mOsm  impermeant  solutes,   how  would  its  final  volume  compare  to  its  initial  volume?   o The  final  volume  would  be  tripled   Homeostasis  of  Plasma  Concentration   • Variety  of  mechanisms  exist  to  keep  blood  plasma  osmolality  maintained   within  very  narrow  limits   • Osmoreceptors:  serve  as  sensor  and  integrating  center   • Ex.  Dehydration:  blood  volume  decreases  and  plasma  osmolality  increases   o Osmoreceptors  found  in  the  hypothalamus   o Signal  posterior  pituitary  to  secrete  ADH     o Efferent  pathway  leads  the  ADH  to  the  kidneys   o Signals  to  increase  water  intake   o Negative  feedback  mechanism   Carrier-­‐Mediated  Transport   • Cellular  metabolism  relies  on  the  cell’s  ability  to  uptake  molecules  it  needs   from  the  EC  fluid   • Many  of  these  molecules  cannot  be  attained  by  simple  diffusionà  require   protein  carriers   • Carrier  proteins  display  the  characteristics  of  saturation   o When  at  capacity,  it  cannot  move  anything  further   • If  carriers  can  transport  more  than  on  molecule  type,  then  they  will  compete   for  transport   o Specificity,  saturation,  competition     Facilitated  Diffusion     • Cell  stimulated,  passive  transport   • Carriers  are  inserted  into  plasma  membrane  to  meet  the  cell’s  needs   • Carriers  are  not  static  à  can  change  them  to  adapt     o Can  transport  molecules  in  both  ways  from  the  plasma  membrane  to   regulate  intake     Active  Transport:  Primary   • Energy  required  for  carrier  function   • Typically,  molecules/ions  moved  against  their  concentration  gradient  (from   low  to  high  concentration)   o Binding  of  molecule  to  be  transported  to  “recognition  site”   o Binding  stimulates  ATP  hydrolysis   o Phosphorylation  causes  carrier  protein  to  undergo  conformational   change   o Hinge-­‐like  motion  of  carrier  protein  releases  transported  molecule  to   other  side   • Often  referred  to  as  pumps   Ex.  Sodium-­‐Potassium  Pump:   • Binds  3  sodium  ions  out  of  the  cell  and  2  potassium  ions  in     • Created  steep  ion  gradient   • Functions:   o Provides  energy  for  coupled  transport  of  other  molecules   o Used  to  generate  electrochemical  events  (impulses)  in  nervous  and   muscle  tissue  à  action  potentials   o Sodium  movement  important  for  osmotic  reasons   § Stops,  observe  increase  in  sodium,  causes  osmotic  influx  of   water  (damage  cell)     Active  Transport:  Secondary   • Driven  indirectly  by  passive  ion  gradients  created  by  operation  of  primary   active  pump   • Can  move  molecules  such  as  glucose  using  the  sodium  gradient   • What  happens  if  the  Sodium-­‐Potassium  pump  is  poisoned?   o The  cell  will  no  longer  be  able  to  move  sodium  and  potassium  and   anything  associated  with  or  utilizing  the  pump  will  also  stop   Movement  of  solutes  across  a  typical  plasma  membrane  involving  membrane   proteins   • Many  of  these  membrane  proteins  can  be  modulated  by  various  signals   o Results  in  controlled  rise  or  fall  of  specific  solute  fluxes  across  plasma   membrane   • Specialized  cells  may  contain  additional  transporters  and  channels   Transport  across  epithelial  membranes   • Epithelial  cells  line  the  body’s  surface  as  well  as  cavities  of  hollow  organs   o Molecules  entering  the  body  must  pass  through  an  epithelial  cell  layer   Junctional  complex   • Presence  and  number  dependent  on  location   • Composed  of:   o Tight  junction:  physically  joins;  seals/binds   o Adhering  junction:  “glues”  together;  proteins  on  both  sides  that  have   an  element  allowing  them  to  stick  together  à  attach  to  the   cytoskeleton  of  the  cell  and  support  the  apical  surface   o Desmosome:  “velcroes”  together   • All  components  not  only  seal  off  epithelial  membrane  but  also  provide  some   of  its  characteristics     Bulk  transport:     • Movement  of  molecules  too  large  to  be  transported  through  plasma   membrane   • Endocytosis:  brings  molecules  into  the  cell   o Phagocytosis:  form  a  vacuole  to  bring  in  à  “cell  eating”   o Pinocytosis:  vacuum  in  liquid  molecules  à  “cell  drinking”   o Receptor  mediated:  uses  carriers  to  bring  in  molecules   • Exocytosis:  release  molecules  from  cells  à  secretion       Membrane  Potential:  difference,  or  potential  difference  in  charge  across  the   membrane   • Separation  of  oppositely  charged  ions  that  has  the  potential  to  do  work  if   they  come  together   • Results  from:   o Action  of  Na-­‐K  pump:  creates  a  concentration  gradient   § Potassium  has  open  leakage  channels  because  it  is  much  bigger   than  sodiumà  potassium  leaks  out  creating  an  unequal   distribution  at  the  plasma  membrane   o Permeability  of  plasma  membrane:  leakage  channels  produce  an   unequal  distribution  of  charges  across  the  plasma  membrane;   however,  if  you  add  up  the  charges  it  is  equal   o Presence  of  impermeant  molecules:  fixed  anions  draw  cations  into  cell   Equilibrium  Potentials:   • Many  inorganic  ions  maintained  at  specific  concentrations  within   intracellular  and  extracellular  fluid   o Contributes  to  membrane  potential   o Impact  of  each  ion  depends  on  its   § Concentration  gradient   § Membrane  permeability     o Potassium     § Plasma  membrane  is  more  permeable  to  this  ion  à  Major  role   in  membrane  potential   • Consider  a  membrane  only  permeable  to  potassium,  what  would  be  the   membrane  potential?   o This  would  cause  the  intracellular  potassium  concentration  to   increase  to  a  point;  then  potassium  ions  would  begin  to  leave  the  cell   by  net  diffusionà  reaching  a  state  of  equilibrium     o Potassium  equilliubium  potential  =  -­‐90mV   § For  a  value  more  negative,  it  would  draw  more  K+  into  the  cell   § For  a  value  less  negative,  it  would  diffuse  out  of  the  cell   o Sodium  equilibrium  potential  would  be  66mV   • Useful  to  know  because  they  tell  us  what  happens  to  the  membrane   potentials  when  the  plasma  membrane  becomes  highly  permeable  to  one   particular  ion     Nernst  Equation:   • Allows  us  to  determine  the  electrical  potential  necessary  to  balance  a  given   ion  concentration  gradient  across  a  plasma  membrane  so  no  net  flux  of  the   ion  occurs     • Diffusion  gradients  of  an  ion  depend  on  concentration  differences   • Equilibrium  potential  depends  on  ratio  of  ion  concentration  on  both  sides  of   plasma  membrane   • Nernst  equation  permits  calculation  of  theoretical  equilibrium  potential  for   specific  ion  if  we  know  its  concentration     • It  differs  between  ion  species   o Magnitude  and  direction   o Cation  value  is  negative   § The  concentration  inside  is  greater  than  the  concentration   outside   • What  happens  when  more  than  one  ion  channel  is  open?   o GHK  equation  (Vm)   o Vm=membrane  potential  of  the  cell  plasma  membrane   • Nernst  Equation:       ▯▯ ▯▯ E x   log      ▯ ▯ ▯   E xequilibrium  potential  in  mV  for  ion  x   Z=valence  of  the  ion  (+1  for  Na+  or  K+)   X oconcentration  of  the  ion  outside  of  the  cell   X=ioncentration  of  the  ion  inside  the  cell       Goldman-­‐Hodgkin-­‐Katz  (GHK)  equation:     ▯▯ ▯ ▯  ▯ ▯▯ ▯▯ ▯ ▯  ▯▯▯▯▯ ]▯   V m61  log     ▯ ▯ ▯ ▯  ▯ ▯▯ ▯▯ ▯▯ ▯ [▯▯▯] ▯   ▯ ▯ ▯ ▯.▯▯ ▯▯▯ ▯(▯.▯▯)(▯)   V m61  log    =  -­‐68mV   ▯ ▯▯▯ ▯ ▯.▯▯ ▯▯ ▯(▯.▯▯)(▯▯▯) • Takes  into  account  each  ions  permeability  coefficientà  Nernst  equation  does   not   • Note  the  chloride  ion  concentration  inside  and  outside  are  reversed  because   it  is  negatively  charged  à  therefore  movement  has  opposite  effect  on   membrane     Resting  Membrane  Potential  (RMP)   • Membrane  potential  of  a  cell  at  “rest”  or  a  cell  in  an  inactive  state   • Depends  on:   o Ratio  of  concentrations  (X /X)o  oi  each  ion  on  both  sides  of  the  plasma   membrane   o Specific  permeability  of  membrane  to  each  ion     • Most  important  “players”:   o Potassium  ion  (K+),  sodium  ion  (Na+)  and  chloride  ion  (Cl-­‐)   o Individual  contribution  dependent  on  concentration  differences   across  the  plasma  membrane  and  permeabilities     § Any  change  in  an  ions  extraceullular  concentration  will  change   the  RMP  but  only  to  the  extent  the  membrane  is  permeable   § Change  in  the  cell  membranes  permeability  for  any  given  ion   will  change  its  RMP   • Cellular  range:  -­‐65mV  to  -­‐85mV   Question:  Would  lowering  a  neuron’s  intracellular  potassium  concentration  by  1mM   have  the  same  effect  on  RMP  as  raising  the  extracellular  potassium  concentration  by   1mM?   à  No;  changing  the  extracellular  [K]  has  a  greater  effect  on  the  equilibrium   potential  and  thus  the  resting  membrane  potential.  This  is  because  the  ratio  of   external  to  internal  [K]  is  changed  more  when  extracellular  levels  go  from  5  to  6   (20%  increase)  than  when  intracellular  levels  are  lowered  from  150  to  149mM   (0.7%).  This  can  be  confirmed  by  the  Nernst  equation     Role  of  Sodium-­‐Potassium  Pumps  (Na-­‐K  pumps):   • Runs  continuously  to  maintain  ion  concentration   • RMP  is  less  than  the  equilibrium  à  causes  some  K+  to  leak  out  and  therefore   is  not  in  equilibrium  with  respect  to  [Na+]  or  [K+]   • The  concentrations  are  still  maintained  constant,  though,  because  of  the   constant  expenditure  of  energy  in  active  transport  by  the  Na-­‐K  pumps   • The  pump  acts  to  counter  the  K+  leaks  and  maintain  the  membrane  potential     • Electronegative  effect:  it  pumps  3Na+  out  of  the  cell  and  2  K+  into  the  cellà   causes  unequal  transport  of  charge   o Adds  about  3mV  to  the  membrane  potential  (very  minimal  effect  on   RMP)   Cell  signaling:     • Refers  to  how  cells  communicate  with  each  other  (intercellular   communication)   o Many  release  regulatory  molecules  into  extracellular  environment   o General  categories:     § Paracrine:  local  mechanismà  regulates  a  nearby  target  cell   § Synaptic:  functional  connectionà  the  means  by  which  neurons   regulate  their  target  cell   • Synaptic  gaps  between  two  cells  contain  chemical   regulators  (neurotransmitters)  to  release  signal   § Endocrine:  long  distance  mechanism  à  regulate  target  cells  via   hormones   • Gap  Junctions:  provide  direct  communication  between  cells  by  fusing  plasma   membranes  together  and  permitting  diffusion  from  one  cell’s  cytoplasm  to   the  next   o As  long  as  the  gap  junctions  are  open,  things  will  be  moving  through   them   Regulatory  Molecules:   • Exert  fine  control  over  the  physiology  of  our  tissues  and  organs   • Target  cells:  only  present  on  the  target  organs   o Must  display  a  target  receptor  protein  for  signaling/regulatory   molecule   Signal  transduction  pathways   • Mechanism  for  lipid-­‐soluble  messengers   o Receptors  will  not  be  on  the  membrane  because  it  can  get  through  it   o Receptors  will  be  in  the  cytosol  or  nucleus     • Mechanism  for  water  soluble  messengers   o If  a  molecule  is  polar  or  too  large  to  penetrate  through  the  plasma   membrane,  the  receptor  must  be  located  on  the  membrane  and  a   second  messenger  system  is  utilized   o The  molecule  does  not  enter  the  cell,  so  its  actions  are  produced  by   the  second  messengers     o Key  second  messenger:  cyclic  adenosine  monophosphate  (cAMP)   o Receptors  can  be  an  enzymeà  binding  activates  the  enzyme   G-­‐protein:     • Three-­‐protein  subunits  that  shuttle  between  receptors  and  different   membrane  effector  proteins     o Includes  specific  enzymes  and  ion  channels   o Protein  subunits:  alpha,  beta  and  gamma   • The  G-­‐protein  activates  an  effector  protein  to  initiate  a  cellular  response     o Requires  GTP  for  energy     Mechanism  for  lipid-­‐soluble  messengers   o Receptors  will  not  be  on  the  membrane  because  it  can  get  through  it   o Receptors  will  be  in  the  cytosol  or  nucleus     Cessation  of  activity  in  signal  transduction     • Important  because  chronic  overstimulation  can  be  detrimental  to  cell   • Key  event  is  stopping  receptor  activation     • Can  be  stopped  by:   o Decreasing  the  concentration  of  the  first  messenger   o Chemically  altering  the  receptorà  lowers  the  affinity  for  first   messenger   o Phosphorylating  the  receptor  à  prevents  G-­‐protein  from  binding   o Endocytose  the  receptor-­‐ligand  complex  à  removes  the  receptor   from  the  plasma  membrane     Chapter  7:  The  Nervous  System  –  Neurons  and  Synapses       The  nervous  system  is  responsible  for  the  coordination  of  cell  function  in  the  human   body   • “Control”  systems:   o Nervous  system:  for  quick  acting  responses   o Endocrine  system:  for  slow-­‐acting,  long-­‐term  responses   • Need  multiple  systems  because  we  need  to  make  corrections  at  different   paces   o Quick  corrections  necessary  in  the  moment  are  not  always  good  in  the   long  termà  thus  aided  by  the  endocrine  system     • Nervous  system:     o Trillions  of  cells  distributed  in  a  network   o Communicate  via  electrical  and  chemical  signals     § Chemical  signaling  is  more  dominant   o Maintains  homeostasis  by:   § Coordinating  functions  of  internal  organs  allowing  to  work  as  a   whole   § Mediating  sensation:  ability  to  perceive  those  sensors   § Controlling  voluntary  movement   § Encoding  complexity  of  brain:  ability  to  process  and  respond  to   changes  in  our  internal  and  external  environment     Structural  organization  of  the  nervous  system   • Central  nervous  system:   o The  brain  and  spinal  cord   o Utilizes  efferent  pathways  via  somatic  and  autonomic  motor  nerves   § Sympathetic   § Parasympathetic   § Enteric   • Peripheral  nervous  system:   o Cranial  nerves  (arising  from  the  brain)  and  spinal  nerves  (arising   from  the  spine)   o Utilizes  efferent  pathways  via  somatic,  visceral  and  special  sensory   nerves   • Composed  of  neurons  and  glial  cells   o Neurons:  basic  structural  and  functional  unit  of  the  nervous  system   § Enables  perception  of  sensory  stimuli,  learning,  memory  and   the  control  of  muscles  and  glands   o Glial  cells:  aid  the  function  of  neurons   § About  5  times  more  abundant  than  neurons   § Can  divide  mitotically  à  why  brain  tumors  are  usually   composed  of  glial  cells  rather  than  neurons     Neurons   • Vary  in  size  and  shape   • Principle  regions   o Cell  body/soma:  serves  as  integration  center   o Dendrites:  receptive  area   § Have  many  on  one  neuron   o Axon:  transmission  area  –  sends  info  out   § Each  neuron  only  has  one   • Axonal  transport:   o Energy  dependent   o Two  different  components  for  removing  different  materials   § Fast  component:  transports  membranous  vesicles   • Important  for  synaptic  transmission     • Travels  400mm/day   § Slow  component:  transports  microfilaments  and  microtubules   • Proteins  important  for  synaptic  function   • Travels  2-­‐8mm/day   o Anterograde  and  retrograde:  represent  direction  of  flow   § Anterograde:  moves  from  soma  à  axon   • Uses  secretory  vesicles  and  kinesin  protein     § Retrograde:  moves  from  axon  à  soma   • Uses  dynein  proteins  and  recycled  membrane  vesicle   • Can  also  move  harmful  things  in  as  well   o Ex.  brings  in  rabies  virus,  herpes,  Lou  Gehrig’s   disease,  etc.     Classification  of  neurons   • Structural  classification:  based  on  the  number  of  processes  that  extend  from   the  cell  body   o Pseudounipolar:  one  large  axon  with  many  dendritic  branches   § Sensory  neurons   o Bipolar:  one  dendrite  and  one  axon  at  either  end  of  the  soma   § Typically  found  in  the  retina  of  the  eye   o Multipolar:  one  axon  and  multiple  dendrites   § Motor  neurons   § Most  common  type  of  neurons     • Functional  classification:  based  on  the  direction  in  which  they  conduct   impulses   o Efferent/motor  neurons:  signals  from  central  nervous  system  to   peripheral  nervous  system   § Somatic  motor  neurons:  responsible  for  reflex  and  voluntary   control  of  skeletal  muscle   § Autonomic  motor  neurons:  innervate  the  involuntary  effectors   (smooth  muscle,  cardiac  muscle,  glands)   o Afferent/sensory  neurons:  signals  from  peripheral  nervous  system  to   central  nervous  system   o Association/interneurons:  communicate  between  sensory  and  motor   neurons   § Typically  multipolar   § Found  in  central  nervous  system     • Nerve:  bundle  of  axons  located  in  the  peripheral  nervous  system   • Tract:  bundle  of  axons  located  in  the  central  nervous  system     Supporting  cells:   • 4  types  of  glial  cells  of  the  central  nervous  system:   o Astrocytes:  help  to  regulate  the  external  environment  of  neurons  in   the  central  nervous  system     o Microglia:  migrate  through  the  central  nervous  system  and   phagocytize  foreign  and  degenerated  material   § Unique  because  they  derive  from  cells  that  were  produced  in   the  embryonic  yolk  sac  and  migrated  into  the  developing   neural  tube   o Ependymal  cells:  epithelial  cells  that  line  the  ventricles  of  the  brain   and  the  central  canal  of  the  spinal  cord   o Oligodendrocytes:  form  the  myelin  sheath  around  axons  of  the  cen


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