Major Endocrine Glands And Hormone Classification Flashcards
(59 cards)
Endocrine Glands
Pituitary Pineal Thyroid and Parathyroid Thymus Adrenal Pancreas Ovary or Testes
Hypothalamus in Endocrine
Provides highest level of endocrine control
–> endocrine director
Hypothalamic Control
Integrates activities of nervous and endocrine system by:
- secretion of regulatory hormones (control activity of anterior pituitary cells
- synthesises hormones and transports to posterior pituitary via infundibulum
- Direct neural control function (hypothalamic autonomic centres control secretion of adrenaline and noradrenaline by adrenal medulla)
Diurnal Control of hormone levels
Circadian rhythm
External cues (light/dark) evoke fluctuations in hormone secretion
Hormonal levels are also influenced by the rate at which they are eliminated by the body
Complementary Actions of Hormones (adrenaline, cortisol and glucagon)
Stress/ Exercise
Release of adrenaline and cortisol
Cortisol
- Causes gluconeogenesis, resulting in raised blood glucose
- Stimulatory effect on pancreatic alpha cells
Adrenal
- Stimulatory effect on pancreatic alpha cells
Stimulatory effect on pancreatic alpha cells causes glucagon to be released
Glucagon causes glycogenolysis on the liver
Antagonistic Actions of Hormones
Hormonal control of glucose homeostasis
Hormonal structure
- Steroids (oestrogen)
- Amine-derived (adrenaline, epinephrine)
- Proteins (oxytocin & ADH, GH and Insulin)
Steroids
lipids derived from cholesterol
Synthesis rates control amounts
Once synthesised steroids are secreted not stored
Steroid Transportation
Hydrophobic
- steroids are transported in blood plasma by binding to carrier proteins
Free/unbound steroids are biologically active
Steroid Examples
Cortisol
- secreted from adrenal cortex
- mediates stress responses
testosterone and oestradiol
- secreted from gonads and placenta
- responsible for sexual characteristics
Steroids: Hormone action
Steroids are hydrophobic/ lipophilic
Pass through plasma-membrane initiating a 2 step process
- Activate hormone-receptor complex forms within the cell
- Complex binds to DNA and activates specific genes –. gene activation leads to production of key proteins
Amine Hormone Types (2)
Derived from amino acids (e.g. tyrosine)
Catecholamine Amine Hormones
- hydsrophilic
- transported unbound or ‘free’ in blood plasma
Thyroid amine hormones
- bound to carrier proteins
Amine hormone storage and secretion
Secreted from thyroid and adrenal medulla
Amines like adrenaline stored as vesicles in cytoplasm until needed
Amine Hormone action
Amine hormones bind to membrane bound receptors to evoke cellular responses
Peptide hormones
hydrophilic and transported unbound or ‘free’ in blood plasma
Peptide hormones secretion
Secreted by
- pituitary
- parathyroid
- heart
- stomach
- liver
- kidneys
Peptide hormone synthesis
Synthesised as precursors molecules and stored in secretory vesicles
Different end hormones can be made by cleaving a common precursor with a different enzyme
Peptide hormone example
Somatostatin
-ring structure due. to disulphide bonds
Insulin
- 2 chains held together by disulphide bonds
- AA sequence may differ between species
Cellular Energy secretion
linked to insulin secretion in pancreatic beta-cell
- Elevation of blood glucose concentration
- Increased diffusion of glucose into the b-cell by facilitated transport (GLUT2)
- Phosphorylation of glucose by glucokinase
- Glycolysis by glucose-6-phosphate in mitochondria yielding ATP
- Increased ATP/ADP ration within cell closes ATP-sensitive K+ channels causing membrane depolarisation
- Opening of voltage gated Ca2+ channels increases intracellular Ca2+ that triggers insulin secretion
Transport of Hormones
Steroid and thyroid hormones
- insoluble in plasma and transported in blood via carrier proteins
Binding to carrier proteins
- facilitation of hormone transport
- Increased half life of hormone
- reservoir for hormone
Carrier Proteins(3)
Cortisol Binding Globulin (CBG)
- Binds cortisol in a selective manner
Thyroxine- Binding Globulin (TBG)
- Binds thyroxine (T4) selectively
Sex steroid binding globulin (SSBG)
- Binds mainly testosterone and oestradiol
Hypothalamus Gland hormones (2)
Thyrotropin Releasing Hormone (TRH)
Corticotrophin Releasing Hormone (CRH
Thyrotropin Releasing hormone
Peptide
Acts on anterior pituitary
Stimulates release of TSH and prolactin
Corticotrophin Releasing Hormone
Peptide
Acts on anterior pituitary
Stimulates release of ACTH
