Endocrine System Flashcards
What is the endocrine system?
+ Second integrative control system of the body
+ Much slower to act than the nervous system
+ Actions are mediated by hormones
What regulatory systems does the endocrine system control?
+ Regulation of cellular metabolism
+ Maintenance of homeostasis (e.g. Ca++)
+Sexual development and reproduction
+ Growth and development from childhood to adulthood
+ Modulates long term behaviour (mood, sleep)
How do endocrine glands distribute hormones around the body?
They have no ducts so they secrete and release hormones directly into the bloodstream
What are hormones?
Hormones are ‘chemical messengers’ that act on target cells through specific receptors
What are the three classes of hormones?
+ Proteins
+ Steroids
+ Amino acid derivatives
Where do glands develop from?
Epithelial cells
What are exocrine glands?
+ Glands with ducts that carry secretions onto the surface of the epithelium
+ E.g salivary, sebaceous, sweat, mammary, glands open onto the skin)
+ Pancreatic duct opens into the duodenum
What are endocrine glands?
Glands that secrete their products, hormones, directly into the bloodstream rather than through ducts
What is paracrine secretion?
+ Paracrine factors (polypeptides) diffuse over short distances
+ Involves cell-cell communication: inducing changes in adjacent cells (e.g peptide neurotransmitters)
+ Important in embryogenesis where gradients of polypeptides influence developmental change
- fibroblast growth factor (FGF) family
- hedgehog family (sonic hedgehog)
- WnT family
- TGF-β superfamily
What are the major glands of the endocrine system?
\+ Hypothalamus \+ Pineal \+ Pituitary \+ Thyroid \+ Parathyroid \+ Thalamus \+ Adrenal \+ Pancreas \+ Ovaries \+ Testes
What are the features of hormones in the blood?
+ Very low concentrations
+ Concentrations vary (e.g episodic, diurnal)
- important when measuring plasma levels
+ Steroid and thyroid hormones are transported in the blood by specific carrier/binder proteins
- improves solubility
- increases half life
- provides a reserve in the blood
+ Only free hormones are biologically active
What are the conditions associated with the mechanisms of action?
+ All hormones act by binding to receptors
+ Target cells must present receptors ( lock and key)
Name types of cell membrane receptors
+ Peptides
+ Glycoproteins
+ Catecholamines
Name types of intracellular receptors in the nucleus
+ Steroids
+ Thyroid hormones
What are protein hormones?
+ Chains of amino acids
+ Usually injected
What are steroid hormones?
+ Synthesised from cholesterol
+ Oral administration
What are amino acid derivative hormones?
+ Thyroid hormones
+ Catecholamines (adrenalin, dopamine, noradrenalin)
From where does the anterior pituitary develop?
The epithelium of the mouth
How does the posterior pituitary develop?
It is a down growth of the hypothalamus (consists of nerve fibres)
What is endocrine axes/cascade?
When the target tissue of one hormone is another endocrine gland; this allows amplification and fine control
Generally, what does the hypothalamus do?
Secrete hormones that control the secretion and release of pituitary hormones
Generally, what do pituitary hormones do?
Stimulate/control many other endocrine glands (thyroid, gonads etc)
What is the function of the hypothalamus gland?
+ Controls the release of anterior pituitary hormones via releasing hormones (prolactin is controlled by a hypothalamic inhibiting factor)
+ Also secretes hormones stored and released by the posterior lobe of the pituitary gland (oxytocin and ADH)
What is another name for the anterior lobe of the pituitary gland?
Adenohypophysis
