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Human Physiology Final Exam Study Guide

by: MBattito

Human Physiology Final Exam Study Guide BIOL 3160

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This study guide covers material from chapters 16-19 that will be on the final exam. It has information from lecture, the power points and additional information from the textbook that will be on t...
Human Physiology
Dr. Tamara McNutt-Scott
Study Guide
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This 38 page Study Guide was uploaded by MBattito on Thursday April 21, 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 83 views. For similar materials see Human Physiology in Biological Sciences at Clemson University.


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Date Created: 04/21/16
Chapter  16:  Respiratory  Physiology     Respiration:   • Ventilation   o Breathing   o Mechanical  process  to  move  air  in  and  out  of  lungs   • Gas  exchange   o Occurs  between  alveolar  air  and  blood  of  pulmonary  capillaries     • Oxygen  utilization   o By  tissues  for  energy-­‐liberating  reactions  of  cell  respiration   Steps  of  Respiration   1. Ventilation:  exchange  of  air  between  atmosphere  and  alveoli  by  bulk  flow   2. Exchange  of  O2  and  CO2  between  alveolar  air  and  blood  in  lung  capillaries  by   diffusion     a. O2  concentration  of  air  is  higher  in  lungs  than  in  blood  –  O2  from  air   of  lungs  à  blood   b. CO2  concentration  in  blood  is  higher  than  air  of  lungs  –  CO2  travels   from  blood  à  air  of  lungs   c. Results  in  inspired  air  containing  more  O2  and  less  CO2  than  expired   air   3. Transport  of  O2  and  CO2  through  pulmonary  and  systemic  circulation  by   bulk  flow     a. Pulmonary:  blood  leaving  lungs  –  has  higher  O2  and  lower  CO2   concentrations  because  lungs  function  to  bring  the  blood  into  gaseous   equilibrium  with  air   4. Exchange  of  O2  and  CO2  between  blood  in  tissue  and  capillaries  and  cells  in   tissues  by  diffusion     5. Cellular  utilization  of  O2  and  production  of  CO2   • External  respiration:  ventilation  and  the  exchange  of  gases  between  the  air   and  blood   • Gas  exchange  between  air  and  blood  occurs  entirely  by  diffusion   through  lung  tissue     • Very  rapid  because  of  large  lung  surface  area  and  small  diffusion   distance   • Steps  1-­‐2   • Internal  respiration:  gas  exchange  between  the  blood  and  other  tissues  and   oxygen  utilization  by  the  tissues   • Steps  4-­‐5       Steps  of  Respiration         Structure  of  the  Respiratory  System     • Alveoli:  tiny  air  sacs  in  the  lungs   o Site  of  gas  exchange     o Very  numerous  ~300  million   § Provides  large  surface  area  for  diffusion  of  gases     o Very  thin  –  forms  short  blood-­‐air  distance  also  aiding  diffusion   o 2  types  of  alveolar  cells   § Type  I:  comprise  95-­‐97%  total  surface  area  of  the  lung   • Gas  exchange  occurs  primarily  through  type  I   • Very  thin   § Type  II:     • Secrete  pulmonary  surfactant  and  reabsorb  Na+  and   H2o   • Prevent  fluid  build  up  within  the  alveoli   o Although  thin,  not  fragile  –  strong  enough  to  withstand  high  stress   during  heavy  exercise  and  high  lung  inflation   § Strength  provided  by  fused  basement  membranes  of  the  blood   capillaries  and  alveolar  walls   o Polyhedral  shape  that  form  clustered  units   § Air  within  one  member  of  a  cluster  can  enter  other  members   through  pores   § Clusters  usually  occur  at  the  ends  of  respiratory  bronchioles   (the  very  thin  air  tubes  that  end  blindly  in  the  alveolar  sac)   • Air  passage  of  respiratory  system  is  split  into  2  functional  zones   o Respiratory  Zone:     § Region  where  gas  exchange  occurs     § Includes  respiratory  bronchioles  and  terminal  alveolar  sacs   o Conducting  Zone:   § Included  anatomical  structures  through  which  air  passes   before  reaching  the  respiratory  zone   • Mouth,  nose,  pharynx,  larynx,  trachea,  primary  bronchi,   all  successive  branching  up  to  and  including  terminal   bronchioles   § Functions  to  warm,  humidify,  filter  and  cleanse  incoming  air   • Ensures  air  is  always  at  temperature  of  37  degrees   Celsius  and  saturated  with  water  vapor  from  wet  mucus   membranes  that  line  respiratory  airways  –  warming   and  humidifying  function   • Mucus  secreted  serves  to  trap  small  particles  –  filter   function   • Mucus  is  moved  by  cilia  in  conducting  zone   o Alveoli  themselves  are  normally  kept  clean  by   resident  macrophages   o Cleansing  action  of  cilia  and  macrophages  in  the   lungs  is  diminished  by  cigarette  smoke   Thoracic  Cavity   • Diaphragm:  dome-­‐shaped  sheet  of  striated  muscle   o Divides  anterior  body  cavity  into  two  parts   § Abdominopelvic  cavity  –  area  below  the  diaphragm  –  contains   liver,  pancreas,  GI  tract,  spleen  and  genitourinary  tract     § Thoracic  cavity  –  area  above  the  diaphragm  –  contains  the   heart,  large  blood  vessels,  trachea,  esophagus,  thymus,  lungs   • Within  thoracic  cavity,  structures  in  the  central  region  (mediastinum)  are   enveloped  by  pleural  membranes   o Pleural  membrane:  2  layers  of  wet  epithelial  membrane   § Parietal  pleura:  superficial  layer  –  lines  inside  of  thoracic  wall   § Visceral  pleura:  deep  layer  –  covers  the  surface  of  the  lungs     o Visceral  pleura  of  lungs  normally  is  pushed  against  the  parietal  pleura   lining  the  thoracic  cavity  –  thus  there  is  no  air  between  the  pleura   under  normal  conditions     § Intrapleural  space:  potential  space  between  the  pleura  that  can   become  a  real  space  if  they  separate  when  a  lung  collapses     Ventilation   • Movement  of  air  results  from  pressure  differences  between  ends  of  airways   induced  by  changes  in  lung  volume   • Physical  properties  of  lung  important  component  of  functionality     o Physical  properties  include:  compliance,  elasticity  and  surface  tension   • Airflow  is  directly  proportional  to  pressure  difference  and  inversely   proportional  to  frictional  resistance  to  flow     Pressure  Relationships  in  Thoracic  Cavity     • Respiratory  pressures  are  always  describes  relative  to  atmospheric  pressure   (760  mmHg  at  sea  level  –  pressure  air  exerts  on  body)   o Negative  respiratory  pressure  (subatmospheric)  indicates  value  lower   than  760  mmHg   o Positive  respiratory  pressure  indicates  value  higher  than  760  mmHg   • Intrapulmonary  pressure:  pressure  within  alveoli   o Changes  during  phases  of  breathing  –  will  equalize  with  atmospheric   pressure   o Air  enters  lungs  during  inspiration  because  atmospheric  pressure  is   greater  than  intrapulmonary  pressureàduring  inspiration   intrapulmonary  pressure  falls  below  atmospheric  pressure     § ~  -­‐3mmHg  during  quiet  inspiration   o Expiration  occurs  when  intrapulmonary  pressure  is  greater  than   atmospheric  pressure     o ~  +3  mmHg  during  quiet  expiration   • Intrapleural  pressure:  pressure  within  pleural  cavity  outside  lungs   o Result  of  elastic  tension  of  lungs  with  thoracic  wall     o Changes  during  breathing  –  always  less  than  intrapulmonary  pressure   • Transpulmonary  pressure:  difference  between  intrapulmonary  and   Intrapleural  pressures   o Always  positive  during  inspiration  and  expiration   o Keeps  air  spaces  in  lungs  from  collapsing  and  lung  volume  changes   parallel  to  thoracic  volume  during  ventilation   Boyle’s  Law   • Relationship  between  pressure  and  volume  of  gases  is  represented  by   Boyle’s  law   • States:  “For  an  ideal  gas,  that  if  temperature  is  constant,  then  pressure  of  a   gas  varies  inversely  with  its  volume”   o P V  =  P V   1 1 2 2 • Note  that  gases,  unlike  liquids,  fill  up  the  space  of  a  container  –  so  given  a   certain  amount  of  air  in  a  large  volume  will  have  less  pressure  than  the  same   amount  of  air  in  a  smaller  volume,  pressure  will  increase     • Changes  in  intrapulmonary  pressure  occur  as  a  result  of  changes  in  lung   volume     o An  increase  in  lung  volume  during  inspiration  decreases   intrapulmonary  pressure  to  subatmospheric  levels   o A  decrease  in  lung  volume  during  expiration  increases   intrapulmonary  pressure  above  atmospheric  pressure   Physical  Properties  of  the  Lungs   • Compliance     o Distensibility  –  stretchable     § Consider  it  the  inverse  of  stiffness   o Defined  as  change  in  lung  volume  per  change  in  Transpulmonary   pressure   § ΔV/  ΔP   o Reduced  by  factors  that  produce  resistance  to  distension     § Low  lung  compliance  makes  it  hard  to  breath  –  takes  a  lot  of   energy   § Pulmonary  fibrosis:  infiltration  of  lung  tissue  with  connective   tissue  proteins  –  decreases  lung  compliance     • Elasticity     o Refers  to  tendency  of  structure  to  return  to  its  initial  size  after  being   distended   o Normal  lung  is  very  elastic     § High  elastic  protein  content   o The  lungs  are  normally  stuck  to  the  chest  wall  –  always  in  a  state  of   elastic  tension   § Tension  increases  during  inspiration  when  lungs  are  stretched   § Tension  decreases  during  expiration  by  elastic  recoil   • Surface  tension     o Force  exerted  by  fluid  in  the  alveoli  that  acts  to  resist  distension     o Lungs  secrete  and  absorb  fluid  in  2  antagonistic  processes   § Cells  move  Na  and  Cl  ions  –  Cl  secretion  and  Na  absorption     • Both  active  processes   • Water  moves  in  with  Na  and  out  with  Cl   § Leaves  very  thin  film  of  fluid  on  alveolar  surface   o At  air-­‐water  interface,  a  tension  exists  due  to  attractive  forces   between  water  molecules  that  “shrink”  alveoli  and  resist  further   stretching   § Would  make  breathing  very  costly  to  organism  –  hard  to   change  lung  volume   § Surfactant  –  made  by  type  II  alveolar  cells   • Detergent-­‐like  substances  that  reduces  cohesive  forces   between  water  molecules  on  alveolar  surface     • Decreases  surface  tension  and  increases  compliance   • Makes  lung  expansion  easier   • Regular  breathing  decreases  surfactant  production  à   deep  breaths  stimulated  to  occur  every  once  in  a  while   to  stimulate  surfactant  release  by  stretching  type  II   pneumocytes   o Law  of  Laplace     § Describes  relationship  between  pressure  (P),  surface  tension   (T)  and  radius  (r)  of  the  alveolus   § P  =  2T/r   • P  is  directly  proportional  to  T   • P  is  inversely  proportional  to  r   Mechanics  of  Breathing   • During  ventilation,  pressure  in  the  alveoli  changes  due  to  thoracic  cavity   volume  changes  so  that  there  is  a  pressure  difference  between  the   atmosphere  and  the  alveoli  in  air  flow   o Breathing  consists  of  2  phases   § Inspiration:  alveolar  pressure  <  atmospheric  à  air  flows  in   • Results  from  muscle  contraction   § Expiration:  alveolar  pressure  >  atmospheric  à  air  flows  out   • Results  from  muscle  relaxation  and  elastic  recoil   o Mechanical  process   • RULE:  volume  changes  lead  to  pressure  changes  which  lead  to  the  flow  of   gases   o Volume  is  always  changed  first  before  pressure   Mechanics  of  Pulmonary  Ventilation   • Diaphragm  is  the  primary  muscle  of  ventilation   o Function  is  aided  by  intercostal  muscles  on  the  ribs   o 2  layers  of  intercostal  muscle  between  bony  portion:  external  and   internal   o Only  1  layer  between  costal  cartilages   § Fibers  oriented  similar  to  internal  intercostals  à  named   interchondral  part  of  the  internal  intercostals  (also  called   parasternal  intercostals)   • Inspiration   o Diaphragm  contracts  and  moves  downward  à  expands  thoracic   volume  vertically   o Parasternal  and  external  intercostal  muscles  contract  and  raise  ribs  à   expand  thoracic  volume  laterally   o Increases  volume  and  lowers  pressure   o Nothing  to  connect  lungs  to  ribs  so  when  rig  cage  expands,  lungs   expand  with  it  because  they  adhere  to  inner  wall  because  the   Intrapleural  pressure  is  less  than  the  intrapulmonary  à  suctions  it  to   wall   • Expiration   o Diaphragm  contracts  –  goes  back  up   o Internal  intercostal  muscles  relax   o Decreased  volume  so  increased  pressure   o Abdominal  muscles  aid  expiration  by  forcing  abdominal  organs  up   against  diaphragm  and  further  decrease  volume   Gas  Exchange  in  the  Lungs   • Gas  exchange  in  the  body  occurs  due  to  bulk  flow  of  gases  and  diffusion  of   gases  through  tissues   • Dalton’s  Law  of  Partial  Pressures   o States  that  in  a  mixture  of  gases,  the  total  pressure  is  the  sum  of  the   partial  pressures  exerted  independently  by  each  gas  in  the  mixture   • Note:  air  flow  stops  at  terminal  bronchioles;  movement  of  gases  from   respiratory  bronchioles  to  alveoli  is  by  diffusion  –  will  flow  along   concentration  gradients   Partial  Pressure  of  Gases  in  Blood   • Large  surface  area  and  short  diffusion  distance  along  with  abundant   capillariesà  rapid  gas  exchange  with  gases  reaching  equilibrium  quickly     • Amount  of  gas  dissolved  in  blood  reaches  a  value  in  accordance  to  Henry’s   Law:   o If  a  mixture  of  gases  is  in  contact  with  a  liquid,  each  gas  will  dissolve   into  the  liquid  in  proportion  to  its  partial  pressure  à  thus,  the  greater   the  concentration  of  a  gas,  the  quicker  and  more  of  it  will  go  into   solution   o Also  must  consider  solubility  of  gas  and  temperature     • Each  individual  alveoli  has  its  own  capillary  network   • Nitrogen  is  present  in  high  concentrations  but  is  not  very  soluble  so  it  will   not  participate  in  gas  exchange  as  much   • Oxygen  is  present  in  higher  concentrations  and  is  semi-­‐soluble  so  it  will   participate  in  gas  exchange  more  than  nitrogen   • Even  though  CO2  is  present  in  smaller  concentrations  than  O2,  CO2  is  more   soluble  so  they  exchange  at  approximately  the  same  rate   Ventilation-­‐Perfusion  Coupling:   • For  efficient  gas  exchange,  must  have  ventilation  and  perfusion  coupled   • Regulated  by  local  autoregulatory  mechanisms  that  monitor  alveoli   • Ventilation:  air  flow  into  alveoli   • Perfusion:  blood  flow  in  capillary  network   • Keeping  ventilation  and  perfusion  synchronized  leads  to  efficient  gas   exchange     o They  are  kept  synchronized  by  vasoconstriction  and  dilation  of   pulmonary  and  systemic  arterioles   § When  alveolar  oxygen  partial  pressure  is  low,  pulmonary   arterioles  constrict  to  reduce  blood  flow  to  alveoli  that  are   inadequately  ventilated  à  reduces  ventilation  and  perfusion   § When  alveolar  oxygen  partial  pressure  is  low,  systemic   arterioles  dilate  to  supply  more  blood  and  oxygen  to  the   tissues   • If  ventilation  and  perfusion  were  not  matched,  blood  from  poorly  ventilated   alveoli  would  mix  with  blood  from  well-­‐ventilated  alveoli     o Would  result  in  a  lower  oxygen  partial  pressure  in  the  blood  leaving   the  lungs  à  dilution  effect     • Apex  of  the  heart  is  over  ventilated  (or  under  perfused)  –  normal  mismatch   of  ventilation/perfusion   o Abnormally  large  mismatches  can  occur  in  cases  on  pneumonia,   pulmonary  emboli,  edema  and  other  pulmonary  disorders       Regulation  of  Breathing:   • Motor  neurons  that  stimulate  the  respiratory  muscles  are  controlled  by  two   major  pathways  –  one  that  controls  voluntary  breathing  and  one  for   involuntary  breathing   • Unconscious  rhythmic  control  is  influenced  by  sensory  feedback  from   receptors  sensitive  to  partial  pressures  of  O2,  CO2  and  pH   • Inspiration/expiration  produced  by  contraction/relaxation  of  skeletal   muscles  in  response  to  somatic  neuron  activity   o Controlled  by  respiratory  centers  in  the  medulla  and  input  from   cerebral  cortex   § Rhythmicity  center  –  controls  autonomic  breathing   • Observe  inspiratory  neurons  –  DRG  and  part  of  VRG  –   and  Expiratory  neurons  –  part  of  VRG   • DRG  =  for  inspiration   • VRG  –  sets  basal  rate  of  breathing   o Modified  by  centers  in  the  pons   § Apneustic  and  pneumotaxic  centers   • Apneustic  control  stimulates  inspiration  neurons   • Pneuomotaxic  center  (now  referred  to  as  pontine   respiratory  center)  antagonizes  apneustic  center  –   inhibits  inspiration   Chemoreceptors     • Automatic  control  of  breathing  influenced  by  chemoreceptors   o Found  in  central  and  peripheral  locations   § Central  chemoreceptors  found  in  medulla   § Peripheral  chemoreceptors  contained  within  small  nodules   associated  with  the  aorta  and  carotid  arteries  à  include  aortic   and  carotid  bodies     • Control  breathing  indirectly  through  sensory  nerve   fibers  to  the  medulla     o Relay  information  on  changes  in  pH  and  brain  interstitial  fluid  and   cerebral  spinal  fluid  as  well  as  blood  partial  pressures  of  O2,  CO2  and   pH   • Chemoreceptors  information  to  the  brain  modifies  rate  and  depth  of   breathing   Effects  of  Blood CO2  and  pH  on  Ventilation   • Hypoventilation  (inadequate  ventilation)  à  causes  P CO2  to  rise  (hyprecapnia)   à  pH  quickly  falls   o Fall  in  pH  because  CO2  can  combine  with  water  to  form  carbonic  acid   –  carbonic  acid  is  a  weak  acid  and  thus  can  release  H+  ions  into  the   solution   • Hyperventilation  (excessive  ventilation)  à  causes  P CO2  to  drop  (hypocapnia)   à  pH  rises     o Rise  in  pH  because  of  the  excessive  elimination  of  carbonic  acid   • Oxygen  content  of  the  blood  decreases  much  more  slowly  because  of  the   large  reservoir  of  oxygen  attached  to  hemoglobin   • So,  blood CO2  and  pH  are  more  immediately  affected  by  changes  in   ventilation  than  oxygen     • Changes  in  CO2  are  the  most  potent  stimulus  for  the  reflex  control  of   ventilation   o Ventilation  is  adjusted  to  maintain  constant  P CO2  h  proper   oxygenation  occurring  as  a  natural  side  effect  of  this  reflex  control   • Immediate  increase  in  ventilation  due  to  activation  of  peripheral  chemoRs  –   sustained  rise  in  CO2  activated  central  ChemoRs  that  take  longer  to  respond   Effects  of  Blood O2    Ventilation   • Chemoreceptor  sensitivity  to  P CO2  augmented  by  a  loO2  P  and  is  decreased   by  a  highO2  P   o Blood  P O2affects  breathing  only  indirectly   • Breathing  increases  linearly  with  increasing  CO2   • O2  must  decrease  by  half  before  breathing  is  stimulated   • Hypoxic  drive:  significant  stimulation  of  ventilation  caused  when  blood  CO2   is  held  constant  by  experimental  techniques  and  blood O2  lls  from   100mmHg  to  70  mmHg   o Due  to  direct  effect  oO2  P  on  carotid  bodies  –  become  depolarized  and   allows  entry  of  Ca2+  à  stimulates  release  of  neurotransmitter  à   increases  ventilation   • Change  in  CO2  responds  more  quickly     Effects  of  Pulmonary  Receptors  on  Ventilation   • Lungs  contain  various  types  of  receptors  that  can  influence  brainstem   respiratory  centers   • Unmyelinated  C  fibers:  sensory  neurons  in  the  lungs  that  can  be  stimulated   by  capsaicin  (chemical  in  hot  peppers  that  produces  burning  sensation)   o Produce  an  initial  apnea,  followed  by  rapid  shallow  breathing  when   peppers  are  eaten  or  pepper  spray  is  inhaled   • Rapidly  adapting  receptors:  cause  a  person  to  cough  in  response  to   components  of  smoke  and  smog  and  inhaled  particulates     o Stimulated  most  directly  by  increase  in  the  amount  of  fluid  in  the   pulmonary  interstitial  tissue  à  the  unmyelinated  C  fibers  can  cause   such  an  increase  and  thus  explains  the  coughing  after  eating  a  hot   pepper   • Hering-­‐Breuer  Reflex:  stimulated  by  pulmonary  stretch  receptors   o Activation  of  receptors  during  inspiration  inhibits  respiratory  control   centers  making  further  inspiration  difficult   o Prevents  over-­‐inflation   o Not  as  active  in  adults  during  normal  tidal  breathing  but  become  more   active  during  higher  tidal  volumes  such  as  during  exercise   Hemoglobin  and  Oxygen  Transport   • Bond  strength  between  hemoglobin  and  oxygen,  and  thus  the  extend  of   oxygen  unloading  in  systemic  circulation,  is  changed  under  different   conditions     • Total  oxygen  concentration  depends  on  the  PO2  and  hemoglobin   concentration   o Anemia:  abnormal  or  below  normal  hemoglobin  levels   § Oxygen  content  of  blood  with  be  abnormally  low   o Polycythemia:  have  above  normal  hemoglobin  levels  –  what  athletes   want   § Can  occur  as  an  adaptation  to  life  at  a  high  altitude   o Normal  levels  allow  blood  to  carry  ~  20mL  o2  O  per  100mL  of  blood   • Most  of  the  oxygen  in  the  blood  is  contained  within  the  red  blood  cells   chemically  bonded  to  hemoglobin   o Each  hemoglobin  molecule  can  attach  to  4  oxygen  molecules  à  280   million  hemoglobin  molecules  per  RBCà  each  RBC  can  carry  over  a   billion  molecules  of  oxygen   • Normal  heme  contains  iron  in  its  reduced  form  –  in  this  form  it  can  bind  with   oxygen  to  form  oxyhemoglobin     o When  oxyhemoglobin  releases  oxygen,  it  is  still  in  its  reduced  form   and  forms  deoxyhemoglobin   o Oxygen  binding  is  cooperative   § To  unload:  first  is  the  hardest  to  remove  and  the  last  is  the   easiest   § To  add:  first  is  the  hardest  to  add  and  the  last  is  the  easiest   o Methemoglobin:  oxidized  hemoglobin  –  iron  in  its  oxidized  state   § Lacks  the  electrons  it  needs  to  form  a  bond  with  oxygen  à   cannot  participate  in  oxygen  transport   § Blood  contains  a  small  amount   o Carboxyhemoglobin:  carbon  monoxide  binds  with  reduced   hemoglobin  instead  of  oxygen     § Binds  with  a  higher  affinity  so  it  will  not  release     • Percent  Oxyhemoglobin  Saturation:  percentage  of  oxyhemoglobin  to  total   hemoglobin   o Measured  to  assess  how  well  the  lungs  have  oxygenated  the  blood   o Normal  amount  ~  97%   Oxygen-­‐Hb  Dissociation  Curve   • Graphical  representation  that  relates  saturation  of  hemoglobin  to  P  – O2ot  a   linear  relationship   • Blood  in  systemic  arties  at  a O2 P  of  100  mmHg  has  a  percent  oxyhemoglobin   saturation  of  97%   o Blood  is  delivered  to  tissue  and  oxygen  is  diffused  into  cells  à  blood   leaving  systemic  veins  have  reduced  oxygen  concentration   o Blood  P O2  40  mmHg  and  percent  oxyhemoglobin  saturation  of  ~   75%  at  rest         Oxygen  Transport   • Effected  by  pH,  Temperature  and  2,3-­‐DPG   • Loading  and  unloading  reactions  influenced  by  changes  in  the  affinity  of   hemoglobin  for  oxygen  –  ensure  active  skeletal  muscles  will  receive  more   oxygen       o Occurs  as  a  result  of  lower  pH  and  increased  temperature  in   exercising  muscles   • Effects  of  Temperature:   o Increased  temperature  à  increases  metabolic  rate   § Increasing  the  temperature  weakens  the  bond  between  oxygen   and  hemoglobin  thus  decreasing  the  affinity   o Increased  temp  –  easier  to  release  oxygen   o Decreased  temp  –  harder  to  release  oxygen   • Effects  of  pH:   o Bohr  effect:  when  you  increase  acidity  and  decrease  pH,  its  easier  to   unload  oxygen   § In  low  acidity  or  high  pH  it  is  harder  to  unload   § Thus,  increase  pH  increases  affinity  for  hemoglobin  to  oxygen   and  decrease  pH  decreases  affinity   o During  exercise,  CO2  levels  increase,  thus  decreasing  the  pH  and   allowing  more  oxygen  to  be  released   • Effects  of  2,3-­‐DPG   o DPG:  byproduct  of  glycolysis     o When  metabolism  increases  –  DPG  increases  à  curve  moves  to  the   right  because  oxygen  is  easier  to  unload   o The  enzyme  that  produces  2,3-­‐DPG  is  inhibited  by  oxyhemoglobin     § When  oxyhemoglobin  concentration  is  lowered,  production  of   2,3-­‐DPG  is  increased   § 2,3-­‐DPG  binds  to  deoxyhemoglobin  and  makes  it  more  stable   à  favors  the  conversion  of  oxyhemoglobin  to   deoxyhemoglobin  aka  releases  oxygen   Carbon  Dioxide  Transport   • Transport  can  occur  in  3  ways   o Dissolved  in  plasma   o Bound  to  Hb  (carbaminoHb)   o As  HCO3-­‐  (bicarbonate)  –  accounts  for  most  of  CO2  in  blood   • Internal  respiration:  converts  CO2  to  make  various  elements   o Makes  hydrogen  ions  and  bicarbonate  à  affects  acidity   o The  H+  ions  are  trapped  in  the  red  blood  cells  causing  a  net  positive   charge  à  attracts  Cl-­‐  ions  which  move  into  the  red  blood  cells  as   bicarbonate  moves  out  à  this  anion  exchange  is  termed  chloride   shift   • Due  to  Bohr  effect  and  increase  of  CO2,  Hemoglobin-­‐oxygen  bonds  are   weakened  –  enhances  O2  unloading   Hb-­‐NO  partnership  in  Gas  Exchange   • NO  (vasodilator)  secreted  by  lungs  or  vascular  endothelial  cells  causes   vasodilation  that  plays  an  important  role  in  blood  pressure  regulation   o However,  hemoglobin  is  a  vasoconstrictor  because  it  scavenges  NO   • Scenario   o As  O2  binds  to  Hb,  it  changes  shape  such  that  it  enables  NO  to  bind  to   it  à  protects  NO   o As  O2  is  unloaded  at  tissues,  so  is  NO,  which  causes  a  local  vessel   dilation  and  aids  in  O2  delivery   o When  CO2  binds,  NO  is  picked  up  as  well  and  carried  back  to  the  lung   o Bottom  line  à  it  appears  that  Hb  carries  along  its  own  vasodilator   Acid-­‐Base  Balance  of  Blood   • Changes  in  blood  pH,  produced  by  alterations  in  either  respiratory  or   metabolic  component  of  acid-­‐base  balance  can  be  partially  compensated  for   by  change  in  other  component   • Blood  pH  kept  within  narrow  range   o Function  of  lungs  (regulate  blood  CO2  levels)  and  kidneys  (regulate   bicarbonate  ion)   o pH  of  7.35-­‐7.45   • Major  buffer  in  plasma  –  bicarbonate  ion   • Acidosis:  blood  pH  fall  below  7.35   o Respiratory  acidosis  caused  by  hypoventilation   § Causes  increased  blood  CO2  and  thus  carbonic  acid   o Metabolic  acidosis  results  from  excessive  production  of  nonvolatile   acids  or  loss  of  bicarbonate   • Alkalosis     o Respiratory  alkalosis  is  caused  by  hyperventilation   § Hyperventilation   o Metabolic  alkalosis  results  from  too  much  bicarbonate  or  inadequate   nonvolatile  acids   § May  be  caused  by  excessive  vomiting  through  loss  of  acid  in   gastric  juice   • Respiratory  component  of  acid-­‐base  balance  is  represented  by  the  plasma   carbon  dioxide  concentration   • Metabolic  component  of  acid-­‐base  balance  is  represented  by  the  free   bicarbonate  concentration   • Proper  pH  can  be  achieved  when  a  good  balance  of  CO2  and  bicarbonate  is   reached     Chapter  17:  Physiology  of  the  Kidneys     Primary  function  of  kidneys  is  in  the  regulation  of  the  extracellular  fluid  (plasma   and  interstitial  fluid)  environment  of  the  body   • Accomplished  through  formation  of  urine   o During  this  process,  kidneys  regulate   § Volume  of  blood  plasma  à  contribute  significantly  to  the   regulation  of  blood  pressure   § Concentration  of  waste  products  in  blood   § Concentration  of  electrolytes  (Na,  K,  HCO3,  etc.)   § pH  of  plasma   • Kidneys  considered  most  potent  acid-­‐base  regulator   Gross  Anatomy  of  the  Urinary  System   • Kidneys:  lie  on  either  side  of  the  vertebral  column  below  the  diaphragm  and   liver   o About  the  size  of  a  fist   o Coronal  Section  of  kidney  has  2  regions   § Outer  renal  cortex  –  reddish  brown  and  granular  because  of   numerous  capillaries   § Deeper  renal  medulla  –  striped  due  to  the  presence  of   microscopic  tubules  and  blood  vessels   • Composed  of  8-­‐15  conical  renal  pyramids  separated  by   renal  columns   o Cavity  of  the  kidney  is  divided  into  several  portions   § Minor  calyx  –  small  depression  that  each  pyramid  projects  into   § Major  calyx  –  formed  by  union  of  several  minor  calyces  à   major  calyces  join  to  form  renal  pelvis     • Renal  pelvis:  cavity  where  urine  produced  in  the  kidneys  is  drained  to     o Urine  then  channeled  from  the  kidneys  to  the  urinary  bladder  through   the  ureters     o Ureters:  long  ducts  that  undergo  peristalsis  (wave-­‐like  contractions)   § Pacemaker  of  these  peristaltic  waves  is  located  in  the  renal   calyces  and  pelvis,  which  contain  smooth  muscle  –  renal   calyces  and  pelvis  also  undergo  peristalsis  to  aid  emptying  of   urine  from  kidney   • Urinary  bladder:  storage  sac  for  urine   o Shape  is  determined  by  amount  of  urine  it  contains   § Empty  =  pyramidal   § As  it  fills  =  ovoid  and  bulges  into  abdomen     o Drained  inferiorly  by  urethra   o Has  a  muscular  wall  –  detrusor  muscle     Microscopic  Anatomy  of  the  Kidney   • Nephron  –  functional  unit  of  the  kidney   o Responsible  of  urine  formation   o Comprised  of  renal  corpuscle  and  renal  tubules   § Renal  corpuscle  –  glomerulus  and  Bowman’s  capsule   • Glomerular  filtration   § Renal  tubules  –  proximal  convoluted  tubule,  distant  convoluted   tubulues  and  Loop  of  Henle   • Tubular  secretion     • Tubular  absorption     o 2  types:   § Cortical  –  original  in  the  outer  2/3  of  the  cortex   • More  numerous   § Juxtamedullary  –  originate  in  the  inner  1/3  of  the  cortex  (next   to  the  medulla)   • Have  longer  nephron  loops   • Play  an  important  role  in  kidney’s  ability  to  produce  a   concentrated  urine   • Glomerular  (Bowman’s)  capsule:  surrounds  the  glomerulus     o Contains  an  inner  visceral  layer  and  outer  parietal  layer   o Space  between  the  two  layers  is  continuous  with  the  lumen  of  the   tubule   o Filtrate  that  enters  glomerular  capsule  passes  into  lumen  of  the   proximal  convoluted  tubule   § Proximal  convoluted  tubule  contains  millions  of  microvilli  to   increase  surface  area  for  reabsorption   § See  absorption   o Fluid  passes  from  the  proximal  convoluted  tubule  to  the  nephron  loop   (Loop  of  Henle)     § This  fluid  is  carries  into  the  medulla  in  the  descending  limb  of   the  loop  and  returns  to  the  cortex  in  the  ascending  limb   o Distal  convoluted  tubule:  coiled  tubule  in  the  cortex   § See  secretion   § Shorter  than  proximal  tubule     § Relatively  few  microvilli     § Terminates  as  it  empties  into  a  collecting  duct   o Collecting  duct:  receives  fluid  from  the  distal  convoluted  tubule  of   several  nephrons   § Fluid  is  drained  by  the  collecting  duct  from  the  cortex  to  the   medulla  as  the  collecting  duct  passes  through  a  renal  pyramid   § Fluid  is  now  called  urine  à  passes  into  minor  calyx  à   funneled  through  renal  pelvis  out  of  the  kidney  into  the  ureter   • Vasculature   o Renal  artery:  where  arterial  blood  enters  kidney   o Renal  artery  divides  into  interlobular  arteries  that  pass  between   pyramids  through  the  renal  columns     o Arcuate  arteries  branch  from  interlobular  arteries  at  the  boundary  of   the  cortex  and  medulla   o Afferent  arterioles:  microscopic  arterioles  formed  from  branching  of   Arcuate  arteries     § Deliver  blood  into  glomeruli  (capillary  network  that  produce  a   blood  filtrate  that  enters  the  urinary  tubules)   o Efferent  arteriole:  where  remaining  blood  in  the  glomerulus  leaves   through   § Delivers  blood  into  another  capillary  network  –  peritubular   capillaries  surrounding  the  renal  tubules   § This  blood  is  drained  into  veins  that  parallel  the  course  of  the   arteries  in  the  kidney  à  interlobular,  arcuate,  and  interlobar   veins   § Interlobar  veins  leave  kidney  as  a  single  renal  vein  à  empties   into  inferior  vena  cava   o Arrangement  of  blood  vessels  is  unique   § Only  one  in  which  capillary  bed  is  drained  by  an  arteriole   instead  of  a  venule  and  delivered  to  a  second  capillary  bed   downstream   Glomerular  Filtration   • Urine  formation  begins  with  the  filtration  of  plasma  from  glomerular   capillaries  into  Bowman’s  capsule  à  glomerular  filtration  –  results  in   formation  of  filtrate   • Process  utilizes  a  pressure  gradient   • Endothelial  cells  of  the  glomerular  capillaries  have  large  pores  (fenestrae)     o Causes  glomerular  capillaries  to  be  100-­‐400x  more  permeable  to   plasma  water  and  dissolved  solutes  than  skeletal  muscle  capillaries   o Pores  are  still  small  enough  to  prevent  entry  of  RBC,  WBC  and   platelets   • Before  fluid  in  blood  plasma  can  enter  the  interior  of  the  glomerular  capsule,   it  must  pass  through  3  layers  of  selective  filters   o Fluid  entering  is  referred  to  as  filtrate  –  will  become  modified  as  it   passed  through  the  different  segments  of  the  nephron  tubules  to   become  urine   o Capillary  fenestrae  –  first  potential  filtration  barrier   § Large  enough  to  allow  proteins  to  pass  but  are  surrounded  by   charges  that  may  present  some  barriers  to  plasma  proteins   o Glomerular  basement  membrane  –  second  potential  barrier   § Layer  of  collagen  and  proteoglycans  lying  immediately  outside   the  endothelium   § Most  resists  fluid  flow  into  the  capsule  lumen   § Offer  some  barrier  to  plasma  proteins   o Slit  Diaphragm  –  third  potential  barrier   § Visceral  layer  of  glomerular  capsule  is  made  up  of  podocytes   § Unique  epithelial  cells  with  a  bulbous  cell  body,  primary   processes  and  thousands  of  foot  processes   § Processes  are  attached  to  the  basement  membrane   § Narrow  slits  between  adjacent  foot  processes  provide   passageways  for  molecules  entering  the  interior  of  the   glomerular  capsule  as  glomerular  filtrate   § Slit  diaphragm  –  links  interdigitating  foot  processes  and   presents  the  last  potential  filtration  barrier   Forces  Involved  in  Filtration   • Filtration  occurs  due  to  opposing  forces   o Important  elements   § Blood  pressure   § Protein  concentration  in  plasma  compared  to  filtrate  (not   many  proteins  in  filtrate)     • Glomerular  filtration  rate  (GFR)   o Volume  filtered  from  the  glomeruli  into  Bowman’s  capsule  per  unit   time   § Average  ~115-­‐125mL/min   § Consider  average  blood  volume  is  5.5L  à  total  blood  volume  is   filtered  every  40  minutes   • Osmotic  pressure  established  by  presence  of  protein  in  plasma  and  not  really   in  filtrate     o Greater  colloid  osmotic  pressure  of  plasma  promotes  the  osmotic   return  of  filtered  water   o Net  filtration  pressure  of  about  10  mmHg  –  since  glomerular   capillaries  are  extremely  permeable  and  have  a  large  surface  area,  this   modest  filtration  pressure  produces  an  extraordinary  large  volume  of   filtrate   Regulation  of  GFR   • Vasoconstriction  or  vasodilation  of  afferent  arterioles  affects  rate  of  blood   flow  into  glomerulus   • Observe  variety  of  intrinsic  and  extrinsic  mechanisms  to  ensure  GFR  is  high   enough  to  eliminate  wastes  and  regulate  blood  pressure  –  but  not  too  high  as   to  cause  excessive  water  loss   o Sympathetic  nerve  endings   § Vasoconstriction  occurs  in  afferent  arterioles   § Helps  to  preserve  blood  volume  and  divert  blood  to  the   muscles  and  heart   o Renal  auto  regulation   § Observe  relatively  constant  GFR  with  fluctuation  BP   • Afferent  arterioles  dilate  when  BP  falls  below  average   and  constrict  when  BP  is  above  average   • Changes  in  efferent  arterioles  are  of  secondary   importance   § Myogenic  regulation   • Smooth  muscle  of  afferent  arterioles  sensitive  to  stretch   –  result  in  vasoconstriction  when  stretched   § Result  of  effects  of  locally  produced  chemicals  on  the  afferent   arterioles   • Tubuloglomerular  feedback   o Macula  densa:  specialized  cells  that  act  as  the   sensor  –  part  of  a  larger  functional  unit   (Juxtaglomerular  apparatus)     •


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