2/7/14  

1  

Endocrine  System  1.  Hormones  –  Func8on  –  Classifica8on  –  General  process  

2.  Secretory  control:  The  Pituitary  gland  and  the  hypothalamus  –  Hormonal  media8on  

through  an  axis  system  3.  Hormonal  Regula8on  –  Stress  Response  –  Metabolism  

•  Endocrine  glands  – Single  gland  made  up  of  many  secretory  cells    

– Secrete  many  different  hormones  

– Each  hormone  binds  to  different  receptors  on  different  target  cells  

Endocrine  glands  

Secretory  Cells  

Hormones  Hormones  

Hormones  

Target  Cell  

Target  Cell  Target  Cell  

Endocrine  System  

Hormones:  Func8on  •  Chemical  produced  and  released  by  endocrine  cells  

•  Regulates  func8on  of  other  cells  •  There  are  a  few  of  them...  

•  Hormones  carried  in  bloodstream  –  Can  exert  effects  over  long-­‐distances  

•  Bind  to  receptor  proteins  on  specific  target  cells  –  Pass  by  many  cells  through  circula8on  

•  Hormones  control  many  bodily  func8ons:  – Water  balance  –  Environmental/physical  stress  

– Metabolism  –  Reproduc8on,  growth,  development  

 

Hormones  

Hormones:  Func8on  

•  Greater  rate  of  secre8on  =  greater  effect  on  target  cells  –  Because  hormones  are  more  concentrated  in  blood  

•  Target  cells  have  1000s  receptor  proteins  –  Greater  ability  to  receive  more  hormones  =  higher  sensi,vity  

Endocrine  glands  

Secretory  Cells  

Hormones  Hormones  

Hormones  

Target  Cell  

Target  Cell  Target  Cell  

Hormones:  Classifica8on  1.  Steroid  hormones  –  Lipid-­‐soluble  (diffuse  through  cell  membranes)  –  Binds  to  receptor  proteins  located  INSIDE  cell  –  Ac8on  is  slow  because  steroid  hormones  produce  proteins  

Figure  2.25d  

2/7/14  

2  

Hormones:  Classifica8on  2.  Pep8de  hormones  –  Chains  of  amino  acids  –  Binds  to  receptors  on  cell  membrane  -­‐  enzyme-­‐linked  or  G-­‐

protein  coupled  reac8ons  –  Binding  ac8vates  2nd  messenger  (cAMP)  to  ac8vate  other  

enzymes    

Figure  2.25c  

Hormones:  Classifica8on  3.  Amine  hormones  –  Modified  chains  of  amino  acids  

New  proteins    1.  Hormone  binds  to  

receptor  proteins  on  target  cell  –  G-­‐protein  coupled,  

Intracellular,  Enzyme-­‐ac8vated  

2.  Interacts  with  DNA  in  target  cell  –  Alters  gene  expression  (may  

trigger  protein  synthesis)  

3.  New  proteins  carry  out  func8on  

Hormones  

Target  Cell  

Target  Cell  Target  Cell  

Endocrine  System:  General  process  

New  func8ons  

Endocrine  System  1.  Hormones  –  Func8on  –  Classifica8on  –  General  process  

2.   Secretory  control:  The  Pituitary  gland  and  the  hypothalamus  –  Hormonal  media8on  

through  an  axis  system  3.  Hormonal  Regula8on  –  Stress  Response  –  Metabolism  

Hypothalamus  •  Maintains  homeostasis  by  regula8ng  internal  environment  – Regulates  hormones  released  from  pituitary  gland    

– Produces  some  hormones  secreted  by  the  pituitary  gland  

– Controls  body  temperature  

– Maintains  water  balance  

2/7/14  

3  

Pituitary  Gland    2.  Anterior  pituitary  –  Hormones  synthesized  

and  secreted  in  endocrine  cells  in  8ssues  

1.  Posterior  pituitary  •  Hormones  secreted  

here  are  synthesized  in  hypothalamus  

Posterior  Pituitary  Gland  1.  Median  eminence  2.  Infundibular  stalk  –  Contain  axons  of  neurons  from  hypothalamus  

 3.  Pars  nervosa  –  Neurons  synapse  

with  arteries  –  Release  hormones  

from  hypothalamus  to  bloodstream  •  Vasopressin  

(an8diure8c  hormone)  

•  Oxytocin  

 

Anterior  Pituitary  Gland  

2.  Travel  through  series  of  vessels  to  anterior  pituitary  

3.  S8mulate/inhibit    release  of  hormones  from  endocrine  cells  in  anterior  pituitary    

•  Made  up  of  endocrine  cells  •  Hypothalamo-­‐hypophysical  portal  system:  1.  Hypothalamus  secretes  neurohormones  into  

median  eminence    

Anterior  Pituitary  Gland  •  Hypothalamus  secretes  two  kinds  of  

neurohormones  •  Releasing  hormones  s8mulate  anterior  pituitary  to  

release  specific  hormone    

Anterior  Pituitary  Gland  •  Hypothalamus  secretes  two  kinds  of  

neurohormones  •  Releasing  hormones  s8mulate  anterior  pituitary  to  

release  specific  hormone    •  Release-­‐inhibi8ng  hormones  inhibit  anterior  pituitary  from  secre8ng  hormones  

CNS  ‘controls’  endocrine  system  Internal/External  

signals  and/or  s8muli   Sensory  receptors  

Secrete  neurohormones  

Signals  integrated  in  CNS   Motor  neurons  

synapse  with  neurosecretory  cells  

Affect  endocrine  glands  and  8ssues  

2/7/14  

4  

Endocrine  System  1.  Hormones  –  Func8on  –  Classifica8on  –  General  process  

2.  Secretory  control:  The  Pituitary  gland  and  the  hypothalamus  –  Hormonal  media,on  

through  an  axis  system  3.  Hormonal  Regula8on  –  Stress  Response  –  Metabolism  

Hormone  media8on    •  Axis  system:  when  secre8ons  of  one  endocrine  gland  act  on  (mediate)  the  secre8ons  from  another  

•  Hypothalamus-­‐anterior  pituitary-­‐thyroid  axis  mediates  hormones  released  from  the  thyroid    

Hormone  media8on    

•  Hypothalamus-­‐Pituitary-­‐Adrenal  Cortex  (HPA)  axis  mediates  hormones  released  from  the  adrenal  cortex  STRESS  RESPONSE  

•  Axis  system:  when  secre8ons  of  one  endocrine  gland  act  on  (mediate)  the  secre8ons  from  another  

Adrenal  Cortex  

•  Glucocor,coids  secreted  in  response  to  stress  – Promote  increased  blood  glucose  concentra8on  

– Cor8sol  is  main  human  glucocor8coid  

•  Adrenal  gland  secretes  many  hormones  for  several  systems  

HPA  axis  •  Nervous  and  endocrine  systems  TOGETHER    mediate  HPA  axis  

Hormone  media8on  in  the  HPA  axis  

1.   Synergys,c:  one  hormone  amplifies  effect  of  another  •  Vasopressin  +  CRH  

à  increased  produc8on  of  CRH    

•  Vasopressin  alone  à  minimal  effect  

•  How  do  nervous  and  endocrine  systems  interact  to  affect  hormone  produc8on/secre8on?  

2/7/14  

5  

Hormone  media8on  in  the  HPA  axis  

1.  Synergys8c  2.   Permissiveness:  

Presence  of  one  hormone  required  for  other  to  operate  •  Adrenaline  causes  

vasoconstric8on  ONLY  if  cor8sol  is  present  

•  How  do  nervous  and  endocrine  systems  interact  to  affect  hormone  produc8on/secre8on?  

Hormone  media8on  in  the  HPA  axis  

•  How  do  nervous  and  endocrine  systems  interact  to  affect  hormone  produc8on/secre8on?  

1.  Synergys8c  2.  Permissiveness  3.   Antagonism:  one  

hormone  opposes  ac8on  of  another  •  Insulin  promotes  uptake  

of  glucose  from  blood;  glucagon  s8mulates  release  of  glucose  into  blood  

Endocrine  System  1.  Hormones  –  Func8on  –  Classifica8on  –  General  process  

2.  Secretory  control:  The  Pituitary  gland  and  the  hypothalamus  –  Hormonal  media8on  

through  an  axis  system  3.   Hormonal  Regula,on  –  Stress  Response  –  Metabolism  

Stress  response    •  Adrenal  cortex  secretes  glucocor8coids    

•  Alters  many  physical  processes  –  Reduced  feeding,  reproduc8on  

–  Increased  heart  and  breathing  rate  

– Heightened  alertness  –  Release  of  stored  energy    – O2/nutrients  sent  to  CNS    

Stress  response  •  Involves  autonomic  NS  and  HPA  axis  

Stress  response    1.    Stress  event  à  Autonomic  NS  and  HPA  axis  response  –  NS:  Adrenal  Medulla  à  Epinepherine,  norepinepherine  –  HPA  axis:  hypothalamus  à  Cor8cotropin-­‐releasing  hormone  

(CRH);  pituitaryà  adrenocor8cotropin-­‐releasing  hormone  (ACTH)    

2/7/14  

6  

Stress  response    1.    Stress  event  à  Autonomic  NS  and  HPA  axis  response  

Phase  1  (fast)  responses:  

1  

à More  blood  to  vital  organs  to  fuel  “fight  or  flight”  response  à To  fuel  muscle  and  heart  rate  increases  (simple  sugars  easiest  to  convert)    à To  counteract  increased  circula8ng  blood  glucose  

2  

3  

Stress  response    2.    Signals  integrated  between  CNS  and  HPA  axis  

 -­‐  epinephrine  further  s8mulates  CRH  produc8on    -­‐  CRH  and  epinephrine  increase  alertness    

Stress  response    3.    Adrenal  cortex  releases  glucocor8coids    

Stress  response    3.    Adrenal  cortex  releases  glucocor8coids    Phase  2  (slow)  responses:  

à More  circula8ng  glucose  (brain  func8on)  à More  faiy  acids  (func8on  of  other  8ssues)  à More  amino  acids  (8ssue  repair)  

2  

3  

1  

Stress  response    4.  Chronic  stress  has  long-­‐las8ng  effects  

Chronic  responses:  

à Inhibited  gonadotropin,  GH  (suppressed  reproduc8on)  à High  blood  pressure  (hypertension)  à Bone-­‐thinning  à Suppressed  immune  system  à Atrophy/shrinkage  of  hippocampus  (memory,  emo8ons)  

2  

3  

1  

Endocrine  System  1.  Hormones  –  Func8on  –  Classifica8on  –  General  process  

2.  Secretory  control:  The  Pituitary  gland  –  Hormonal  media8on  

through  an  axis  system  3.   Hormonal  Regula,on  –  Stress  Response  –  Metabolism  

2/7/14  

7  

Hormonal  regula8on  of  metabolism  •  Cells  need  nutrients  con8nuously  – Fats,  carbohydrates,  proteins  

•  Rely  on  stored  energy  sources  •  Hormones  regulate  storage,  mobiliza8on,  conversion  into  useable  forms  – Sense  body’s  needs/requirements  

Hormonal  regula8on:  Metabolic  func8ons  

•  Concentra8on  of  blood  glucose  is  main  factor  in  metabolic  func8oning  

•  Two  main  hormones  secreted  by  pancreas  1.  Insulin:  decreases  

blood  glucose  concentra8on  

2.  Glucagon:  increases  blood  glucose  concentra8on    

Hormonal  regula8on:  Insulin  •  Short-­‐term  storage/release  of  nutrients  

•  Insulin  binds  to  protein  receptors  à  facilitates  diffusion  of  glucose  into  target  cells  

Eat  Food  

Pancreas  releases  insulin  

é  storage  of  all  three  nutrients  

é  uptake  of  glucose,  faiy  acids,  amino  acids  from  blood  

ê  Blood  glucose  concentra8on  

Decrease  in  blood  glucose:    hypoglycemic    effect  

Carbohydrates  cause  spike  in  blood  glucose  

1.  High  carb  meal  2.  Glucose  in  blood  

surges  3.  Insulin  released  4.  Facilitated  diffusion  

into  cells  5.  Lowers  blood  

glucose  

Proteins  DO  NOT  cause  spike  in  blood  glucose  

1.  Low  carb  meal  2.  NO  Surge  of  

glucose  in  blood  3.  Insulin  s8ll  released  4.  Facilitated  diffusion  

into  cells  5.  Lowers  blood  

glucose  

Diabe8cs  don’t  produce  insulin  •  Blood  glucose  remains  high  •  Kidneys  can’t  filter  glucose  – Excreted  as  waste  and  not  used  for  energy!  – Diabe8cs  are  told  to  avoid  carbohydrates  (simple  sugars)  

2/7/14  

8  

Hormonal  regula8on:  Glucagon  

•  Pep8de  hormone  secreted  by  pancreas  •  Released  when  blood  glucose  low,  amino  acids  high    

Hormonal  regula8on:  Glucagon  •  S8mulates  gluconeogenesis  

•  Causes  blood  glucose  to  rise:  Hyperglycemic  effect