Endocrine system Flashcards
What does the endocrine system consist of?
- Specialised ductless glands (or neurones) scattered throughout the body
What do the glands of the endocrine system secrete and how do they travel in the body and what is the response?
- They secrete biologically active chemical messengers
(hormones) into the blood stream. - The hormones are carried in the blood stream to interact with distant target cells.
- Interaction leads to specific target cell response in terms of metabolism, growth or reproduction.
What are the anatomical divisions of the endocrine system and what does each one consist of?
THE CENTRAL ENDOCRINE GLANDS: Hypothalamus, Pituitary gland, Pineal gland
THE PERIPHERAL ENDOCRINE GLANDS: Thyroid glands, Adrenal glands, Endocrine pancreas, Parathyroid glands
State the functions of the endocrine system.
- Regulate & Control Important Cellular & Body Functions.
- Cellular Metabolism and water & Electrolyte balance.
- Cell Growth & Development and Reproduction.
- Adaptive changes to help the body cope with stressful
situations. - Control & Integration of circulatory and digestive
systems.
Describe the synthesis of hormones.
Vesicle-mediated pathway
* Synthesised in rER & packaged in vesicle
* Amine/AA/Peptide/Protein hormones
Non-vesicle-mediated pathway
* Synthesised in sER & directly released
* Steroid hormones
Describe the transport of hormones.
Free & unbound
* Amine/AA/peptide hormones
Protein career-bound
* Steroid & thyroid hormones
How do hormones produce their effects on target cells?
- By interacting with specific receptors
What are the two broad types of hormonal receptors?
- Cell surface receptors:
Receptor-ion channels
G-protein coupled receptors
Tyrosine kinase-linked receptors - Intracellular or nuclear receptors
What may endocrine disorders result from?
- Hyposecretion
– Endocrine secretes too little of its hormone
– Primary, Secondary or Tertiary - Hypersecretion
– Endocrine secretes too much of its hormone
– Primary, Secondary or Tertiary - Abnormal Target Cell Responsiveness
– Receptor down regulation (hypo responsiveness)
– Receptor up regulation (hyper responsiveness)
Where are the hypothalamus and pituitary glands located?
In diencephalon: the pituitary gland lies in a pocket of bone at the base of the brain
State the function of the hypothalamus & pituitary gland.
Function cooperatively as ‘master regulators’ of the endocrine system - control of critical homeostatic & metabolic functions
State the two lobes the pituitary gland consists of and their functions?
- Anterior pituitary: secretes and releases 6 major hormones
- Posterior pituitary: stores and releases 2 hormones
What is the hypothalamus?
Brain’s coordinating centre for endocrine, behavioural & autonomic nervous system function
What does the hypothalamus act as?
A neuroendocrine transducer or bridge:
– receives & integrates multiple brain signals
– converts signals into chemical messages
– releases chemical messengers (hormones) to control secretion of pituitary hormones
– pituitary hormones control activity of peripheral endocrine glands
Describe the transport of hypothalamic releasing hormones.
- Hypothalamus makes releasing hormones
- Action potentials cause release of hormones into portal vessels which are carried to anterior pituitary
- The anterior pituitary releases its stored tropic hormones into systemic circulation
Describe the role of the hormones GH (ANTERIOR PITUITARY HORMONE)
– Important role in intermediary metabolism
* Exerts largely anti-insulin effects
* Increases lipolysis - increases free fatty acid (FFA)
mobilization & use as fuel
* Inhibits peripheral cellular glucose uptake - increases blood glucose levels & decreases use of
glucose as fuel
What is the secretion of the growth hormone modulated by?
- GHRH & somatostatin from hypothalamus
- Ghrelin from gastric fundus
What does GH output increase with?
Size - to maintain the concentration of GH pulses needed to sustain growth during childhood
Describe the pathology of GH.
*undersecretion BEFORE puberty will cause dwarfism
*overproduction BEFORE puberty will cause
gigantism
*AFTER puberty over-production causes acromegaly
State the role of the follicle-stimulating hormone FSH (ANTERIOR PITUITARY HORMONE)
– stimulates growth & development of ovarian follicles (F)
– promotes ovarian secretion of oestrogen (F)
– Required for sperm production (M)
How is FSH stimulated?
– Secretion stimulated by GnRH from the hypothalamus
Describe the role of the luteinising hormone (LH) (ANTERIOR PITUITARY HORMONE)
– Responsible for ovulation & development of the corpus luteum (F)
– Regulates ovarian secretion of sex hormones (F)
– Stimulates testes to secrete testosterone (M)
What is the secretion of LH stimulated by?
GnRH from hypothalamus
Describe the role of prolactin (PRL) (ANTERIOR PITUITARY HORMONE)
– Enhances breast development & milk production in females;
elevated in pregnancy and lactation
– Overproduction leads to infertility
