MNSR 40 - Endocrinology: Endocrine systems: hormones Flashcards
Endocrinology
The branch of biology dealing with the endocrine glands and their secretions, esp. in relation to their processes or functions.
Features of endocrine glands
ductless
secrete hormones
secreted directly into bloodstream
hormones
A substance secreted by cells in one part of the body that passes to another part where it is effective, in very small concentrations, in regulating the growth or activity of the cells
what will stimulate the release of the hormone
the appropriate receptor of the hormone
how do hormones function
as long term regulators of many activities, often involved in homeostasis
where do the secreted hormones go to and how are they transported
Transferred to the site of action, or target organ
Usually complexed with (transported by) plasma proteins - usually hydrophobic
how are neurohormones (hormones released by neurons) released
Pass down the axon to the nerve endings
Released into special capillary networks near the target organ
tissue hormones
hormones, produced in various parts of the body which have a local effect on cells and tissues
examples of tissue hormones
Kinins Prostaglandins (inflammatory mediator) Gastrin (Gastric acid secretion) Secretin (Regulation of pH in duodenum) Cholecystokinin (Digestion of fat & protein).
types of functionality of hormones
endocrine signalling
paracrine signalling
autocrine signalling
endocrine signalling hormones
hormones acts on target sells distant from site of synthesis
e.g. adrenocorticotrophic hormone
paracrine hormones
Signalling molecules act on neighbouring cells e.g. serotonin
Autocrine hormone
Local regulators
Signalling molecules act on same cells to amplify signals
4 main chemical groups
peptide hormones
amino acid derived hormones
steroid hormones
fatty acid hormones - derived from from arachidonic acid
4 ways hormones control activity of cells and tissue of target organs
Influencing the rate of synthesis of enzymes or other proteins.
Altering the rate of enzyme catalysis
Speeding up or slowing down metabolic pathways.
Altering the permeability of the cell membrane.
2 types of hormones
Cell-surface signalling – hydrophilic
Intracellular signalling - hydrophobic
mechanism of action of steroid and thyroid hormones
easily pass through membrane into nucleus
interact w/ receptor to activate or recess specific genes - synthesis of specific proteins
mechanism of action of peptide hormones
water soluble - can’t directly pass through membrane
GPCR - G Protein Coupled Receptor
hormones bind to receptor leads to conformational change in receptor
G protein is activated - moves away from receptor to activate next signalling protein in pathway usually adenylyl cyclaseATP – > cyclic-AMP
Phosphorylation cascade w/ protein kinase
hypothalamus function in endocrine systme
Links nervous system to endocrine system
Receives input from other areas of brain and alters release of hormones in response
what type of hormone does hypothalamus release
neurohormones
where are hormones produced in hypothalamus usually stored in
pituitary gland for regular secretion of hormones
through what system are hormones secreted in hypothalamus
hypothalamic-hypophyseal portal system
name 3 main components of the hypothalamic-hypophyseal portal system
superior hypophyseal artery
primary capillary plexus
secondary capillary plexus
function pituitary gland
Controls the other endocrine glands
what influences and regulates pituitary gland
Influenced by endocrine glands via a system of mostly negative feedbacks
Partially regulated by hypothalamus
2 lobes of pitiuitary gland
Posterior pituitary (neurohypophysis) is neural tissue anterior pituitary (adenohypophysis) is glandular tissue
how is pituitary gland attached
Attached by a short connection called the infundibular stalk (pituitary stalk) to the hypothalamus
what is the posterior and anterior part of the pituitary gland derived from?
One part is derived from a downgrowth of the hypothalamus, the infundibulum,
The other from Rathke’s pouch
rathke’s pouch
Depression of the roof of the developing mouth
Breaks away from the pharynx
Forms anterior pituitary
hypothalamus extends to form
Infundibulum
Posterior pituitary
what is posterior of pituitary gland composed of
Composed of two parts: pars nervosa and the median eminence
where is anterior pituitary developed from
developed from an inpushing of the mouth ectoderm called Rathke’s pouch.
how many major hormones are secreted from anterior pituitary gland and how many of them are trophic
Seven major hormones are secreted by the anterior pituitary, four of which are trophic hormones
trophic hormones
are hormones which have another endocrine gland as the target organ
identify trend in hormones secreted by anterior pituitary gland
hormones appear to have both releasing and inhibitory factors
The releasing function is dominant
Prolactin is an exception; inhibited by dopamine
name the 7 hormones released from the anterior pituitary gland
Growth Hormone Prolactin Follicle-stimulating Hormone Luteinizing Hormone Thyroid-stimulating Hormone Adrenocorticotrophic hormone Endorphins
list the hormones released from hypothalamus
Growth hormone releasing hormone Prolactin releasing hormone ADH Oxytocin Gonadotrophin-releasing hormone Thyrotrophin-releasing hormone Corticotrophin-releasing hormone
Hypothalamus-pituitary axis
The control and secretion of these hormones is under the direction of the hypothalamus which releases special neurohormones
hormones secreted in posterior pituitary gland
oxytocin
ADH - vasopressin
where is the pars intermedia and what hormone does it release
Boundary between the anterior and posterior lobes of the pituitary
Melanocyte-stimulating hormone (MSH)
An increase in MSH will cause a darkening in humans
cushing’s syndrome
high levels of adrenocoroticotropic hormone production - high MSH levels - > abnormal darkening
