Human Endocrine System

• HUMAN ENDOCRINE SYSTEM


  Composed of many parts (glands, hormones,

  target cells)

  Hormones

  Help control & regulate body processes

  Carried by body fluids to target cells
• Endocrine glands

  Ductless glands that secrete hormones into surrounding fluid

  Some glands release > 1 hormone with different functions

   Ex. Anterior lobe of pituitary gland

   Secrete 7 kinds of hormones with distinct function
• Exocrine glands

  release substances through ducts onto body

  surfaces/cavities

   Ex. Sweat/saliva
• HYPOTHALAMUS


  Coordinates endocrine signaling

  Receives information from nerves  initiates

  neuroendocrine signaling

  Ex. Sensory information from brain re seasonal

  changes  passed to hypothalamus 

  hypothalamus regulates release of

  reproductive hormones during breeding

  season
• PITUITARY GLAND


  At the base of the brain; connected to

  hypothalamus

  Anterior & posterior lobe – each secretes

  hormones in response to hypothalamus

  Most control other endocrine glands  master gland
• POSTERIOR PITUITARY GLAND

  Extension of neural tissue of hypothalamus

  2 hormones synthesized by neurosecretory cells of

  hypothalamus

  1. Anti-diuretic hormone (ADH)/vasopressin

   Regulates kidney function

   Increases water retention in kidneys  maintain normal blood

  osmolarity

  2. Oxytocin

   Multiple functions related to reproduction

   Controls milk secretion

   Regulates uterine contraction

   Influences behavior related to maternal care, pair bonding,

  sexual activity
• ANTERIOR PITUITARY GLAND


  Endocrine gland

  Secretes hormones in response to hormones

  from hypothalamus

  Control diverse processes in the body (metabolism,

  regulation, & reproduction)

  Many regulate glands/tissues

  Hormones from hypothalamus control

  release of all anterior pituitary hormones

   Releasing/inhibiting hormone

  Tropic hormones – target other endocrine

  glands
• HORMONE CASCADE PATHWAY

  Redirect signals from hypothalamus to

  other endocrine glands

  Ex. Thyroid regulation

   Regulates bioenergetics (maintain blood pressure,

  heart rate, & muscle tone)

   regulates digestive & reproductive functions

   Low blood level of thyroid hormone  no

  negative feedback regulation  anterior

  pituitary secretes TSH continuously  enlarged

  thyroid gland  goiter
• HORMONAL REGULATION OF GROWTH

  Growth hormone

   Secreted by anterior pituitary

   Stimulates growth thru tropic & non-tropic effects

  Major target: liver  release IGFs  blood

  circulation  stimulate bone and cartilage growth
• HORMONAL REGULATION OF GROWTH

  Growth hormone disorders

  Hypersecretion during childhood 

  gigantism

  Hypersecretion during adulthood 

  stimulates bony growth in few body parts

  still responsive to GH (face, hands, feet)

   acromegaly (overgrowth of

  extremities)

  Hyposecretion during childhood 

  retards long bone growth  pituitary

  dwarfism
• DIABETES MELLITUS

  2 main forms

  Type 1 diabetes

   Autoimmune disorder

   Own immune system attacks pancreas (secretes

  insulin)

   Blood glucose levels must be monitored

  frequently

  Little to no insulin

   Must inject insulin when blood glucose is too

  high or eat small amount of sugar when too low
• 2 main forms

  Type 2 diabetes

   Due to hormone resistance in target cells

   Target cells don’t respond to insulin  glucose in

  blood increases

   Response: pancreas secretes more insulin 

  damages pancreas over time  patient requires

  insulin injections

   Can be avoided since acquired

   Factors

   Inactivity  regular exercise

   Poor diet  healthy diet & weight loss
• FEEDBACK MECHANISMS

  Negative feedback mechanism

   Response reduces initial stimulus

  Positive feedback mechanism

   Reinforces stimulus