Endocrine physiology

Nervous system and endocrine system are regulatory system .

  • Endocrine is a ductless gland
  • It secrete hormones.
  • it directly goes into the blood and work on distant target tissue.
  • when hormone come to blood it reaches to all organ but specific tissue and organ have receptors for it.
  • paracrine act on parietal cell.
  • it will act on neighbouring cell.
  • it will not go into the circulation.
  • Autocrine :-it act on same cell which given out the secretion.
  • Endocrine releases three type of hormones:-peptide hormone,steroid hormone,Derivative of single amino acid.

peptide hormone:-

  1. growth hormone
  2. insulin
  3. PTH
  4. glucagon
  • Amino acid sequence
  • It is synthesised and stored.
  • short half life
  • Found in bound form
  • M.O.A. of hormone:-Receptors on target cell membrane.
  • Hormone bind to cell membrane which activate secondary messenger.

steroid hormone:-

  • glucocorticoid:-cortisol
  • mineralocorticoid :-it regulate salt and water balance.
  • sex steroid:-Estrogen,progesterone,androgen.

Derivative of single amino acid:-

  • Thyrosine derived hormones
  • Thyroid hormone
  • catecholamine

Two type of cell membrane receptor present in peptide hormone :-

  • GPCR-Receptor combine with G- protein hormones but no enzyme activity seen inside cell membrane.
  • Catalytic receptor:-Receptor show enzymatic activity and it activate secondary messenger.
  • secondry messenger are cyclic AMP, cyclic GMP.
  • GPCR is also known as serpentine receptor because of having seven fold.
  • Cyclic AMP is secondary messenger in ACTH,FSH,TSH,LH,PTH,Glucagon.
  • Cyclic GMP is secondary messenger for NO ,Atrial natriuretic peptide.
  • GPCR has two sub unit G alpha inhibitory,G alpha stimulatory.

catalytic receptor is of two type:-

  1. Receptor for tyrosine kinase activity.
  • Example:- insulin
  • Receptor will act on tyrosine kinase residue of protein
  • insulin bind cell membrane receptor  which will activate secondary messenger 2.Tyrosine kinase associated receptor.
  • Example:-Growth hormone
  • GH bind with receptor and enzyme get activated.
  • JAK/STAT get activated by tyrosine kinase associated receptor.

Fact about hormones 

  • shortest hormone:- TRH
  • Longest hormone:-HCG
  • Shortest half life:- catecholamine
  • Longest half life:- vit -D
  • latent period:- Time taken to take action after stimulus received is known as latent period.
  • shortest latency:-oxytocin.
  • longest latency:-thyroid hormone.
  • All hormone are synthesised and stored intracellular except thyroid which stored extracellular.
  • Thyroid hormone are stored in thyroglobulin.
  • Thyroid gland are not essential to life only BMR drops.
  • Parathyroid gland are essential to life because serum calcium levels get dropped.