Endocrine physiology Flashcards
What is the purpose of the endocrine system? (4)
To allow communication in a multi-cellular organism
To allow integration of whole body physiology
To allow rapid adaptive changes to occur
To allow chronic maintenance of metabolism
What are the 3 main types of hormones?
Amine (aa derived)
Peptide
Steroid (lipid/cholesterol derived)
What type of hormone are secreted from the adrenal medulla? Give the main 2 examples of this type
Amine hormones
- Epinephrine
- Norepinephrine
What type of hormone are secreted from the adrenal cortex? Give the main 3 examples of this type
Steroid hormones
- Aldosterone (salt)
- Cortisol (sugar)
- Androgens (sex)
What type of effect/action does epinephrine/norepinephrine secreted from the adrenal medulla have?
Action similar to that of sympathetic nerves
What are steroids derived from?
Cholesterol
True or False: Steroid hormones can not be stored in cells
True, they diffuse lipid bilayers
Why does the removal of circulating steroid/thyroid hormones take longer than that of peptide/amine hormones?
Steroid hormones are water insoluble and are so transported in the blood mainly bound to plasma proteins. Binding prevents the steroids from being excreted/metabolised (cleared from circulation)
How is it that steroid hormones exert their effects? (What is their most common signalling method)
Bind to intercellular receptors that directly alter gene transcription
Define permissiveness
This is when a particular hormone must be present for another hormone to be able to exert its full effects
Define the term ‘tropic’ hormone
A hormone that stimulates the secretion of another hormone
Type 2 diabetes mellitus is an example of which type of endocrine disorder: hyposecretion, hypersection, hyporesponsiveness, hyperresponsiveness
Hyporesponsiveness: cells don’t respond to insulin
What is meant by a portal system?
Vein between two capillary beds
Define the term hormone
A signalling molecule secreted from specialised endocrine tissue
From which embryological layer is the adrenal cortex derived from?
Mesoderm
From which embryological layer is the adrenal medulla derived from?
Ectoderm
Name the adrogens secreted from the Zona Recticularis layer of the adrenal cortex
Androstenedione
Dihydroxyepiandtostenedione
What does the neurohypohysis refer to?
The posterior pituitary gland
Name the portal system connecting the hypothalamus to the anterior pituitary gland
Hypothalamo-hypophysis portal vessels
What is the anterior pituitary gland embryologically derived from?
Rathke’s pouch
State the actions of vasopression
Acts to increase BP
Vasoconstriction of arterioles (V1a)
Kidneys (called ADH) - water reabsorption (V2) via aquapourins
State the actions of oxytocin
Uterine muscle contraction
Contraction of myoepithelial cells in lactacting breasts
What is the name of the capillary bed located at the infundibulum that makes up the hypothalamo-hypophyseal portal circulation?
Median eminance
State the actions of thyroid hormones
Increase metabolic rate Increase O2 consumption Temp homestasis Increase CO Permissive effects on adrenaline and GH
Name the enzyme used in the synthesis of thyroglobulin and the oxidation of I- to I
Thyroperoxidase
Name the protein channel that allows the entry of I- into the colloid
Pendrin
What does MIT/DIT stand for
Monoiodotyrosine
Diiodotyrosine
State the physiological functions of cortisol
Stress hormone (longer term response) Maintains BP Metabolic homeostasis - maintains glucose levels/ Anti-inflammatory/immune functions Development and differentiation
State the functions of cortisol in stress
Mobilised glucose stores (anti-insulin)
Increases vascular reactivity/increased CVR performance
Inhibition of growth
Inhibition of inflammation
What are the actions of GH
1) Stimulate precursors to differentiate and secrete IGF-1
2) Stimulate IGF-1 release from the liver
3) Anti-insulin effects
4) Protein syn
State the action of IGF-1
Stimulate cell division
Where is parathyroid hormone release from?
CHIEF cells of the parathyroid homrone
Where is calcitonin produced?
Parafollicular C cells of thyroid follicles