Endocrine intro Flashcards
What is the endocrine system involved with?
growth and development
sex differentiation
metabolism
adaptation (digestion, nutrient storage, electrolyte/water metabolism, reproductive functions)
autocrine
into ECF and affect same cells that produce them
eg. insulin from pancreatic beta cells affects the same cells
paracrine
secreted into ECF and affect nearby cells of a different type
eg. steroids on ovaries
endocrine
hormone secreted into circulation that targets distant cells
endocrine vs synaptic signalling
synaptic - NTs from one nerve to another nerve/muscle across a synapse
endocrine - hormone travels through bloodstream to target cell
example of a single hormone exerting effect on different tissues
Estradiol
acts on ovarian follicle, maturation
uterus to stimulate growth and maintain cyclic changes
mammary gland, ductal growth
hypothalamic-pituitary system (gonadotropins and prolactins)
bone, skeletal integrity
general metabolic processes
single function regulated by several hormones
lipolysis (release of fatty acid from adipose tissue) catecholamines insulin glucagon cytokines tumor necrosis factor alpha
Where are hormone receptors located?
surface of the cell
in the cell
How do receptors on the surface of the cell act?
act through second-messenger mechanisms
How do receptors located in the cell act?
they modulate the synthesis of enzymes, transport proteins or structural proteins
categories of hormones
amines
peptides and proteins
steroids
examples of amine hormones
adrenaline
noradrenaline
thyroid hormones T3 and T4
examples of peptide and protein hormones
insulin
growth hormone
examples of steroid hormones
cortisol
aldosterone
testosterone
What gland do AD and NAD come from?
adrenal medulla
gland for insulin?
Islets of Langerhans
gland for growth hormone?
anterior pituitary
gland for steroid hormones (cortisol, aldosterone, testosterone)?
adrenal cortex
What hormones circulate unbound in blood?
peptide and protein
What hormones circulate attached to transport carriers?
steroid and thyroid hormones
How do hormones travel in the bloodstream?
free, unbound molecules
attached to transport carriers
What factors affect the response of a target cell to a hormone?
number of receptors present (up and down regulation)
affinity of these receptors for hormones
Are steroids hydrophilic or hydrophobic?
hydrophobic
Can unbound or bound hormones diffuse into the cell?
unbound
Where are steroid hormone receptors located?
in the nucleus or cytoplasm
How do steroid hormone receptors work?
- unbound hormone diffuses through target cell
- receptor hormone complex binds to DNA and activates/represses one or more genes
- activated genes create new mRNA (transcription) that moves to cytoplasm
- translation produces new proteins
- some hormones bind to membrane receptors that use 2nd messenger systems to create rapid responses
What hormones use intracellular interaction?
oestrogens testosterone progesterone adrenal cortical hormones thyroid hormones
What controls hormone levels?
- diurnal fluctuations within sleep-wake cycle
- regulated by feedback mechanisms that monitor glucose and water
- regulated by feedback mechanisms that involve hypothalamic-pituitary-target system
what part of the brain is coordinating center for endocrine?
hypothalamus
example of positive feedback
hypothalamus sends impulse to posterior pituitary
posterior pituitary releases oxytocin
produces milk
suckling stimulates nerves in breast to send impulse to hypothalamus
negative feedback
1. inc glucose levels beta cells release insulin body/liver takes up more glucose glucose declines 2. glucose declines alpha cells release glucagon liver breaks down glucagon and releases glucose glucose rises
endocrine disease classification?
hormone excess
hormone deficiency
hormone hypersensitivity
non-functioning tumours
Measures for assessing hormone levels
blood tests urine tests stimulation and suppression tests genetic tests imaging biopsy
