Overview of Hormonal Secretion Flashcards
What type of secretion is hormonal?
Endocrine = into blood
What are the X2 types of hormone delivery into the blood?
Explain each or these.
1) endocrine = hormone released from cell to blood
2) neuroendocrine = hormone released from nerve into blood
Name some examples of neuroendocrine secretion.
1) hypothalamus
2) posterior pituitary
3) adrenal medulla
Explain each of the following:
1) merocrine
2) apocrine
3) holocrine
4) endocrine
5) paracrine
6) autocrine
1) merocrine = hormone filled vesicles in cells fuse with cell membrane
2) apocrine = hormones create vesicles for release from cell membrane
3) holocrine = cell dies to release hormone
4) endocrine = hormone release into blood
5) paracrine = hormones released act locally
6) autocrine = hormone released acts on the same cell which released it
What are the X3 main classes of hormones?
1) proteins/peptides
2) steroids
3) amines
How do peptide/protein hormones circulate in the blood?
Unbound as they are polar
Why is the rate of steroid hormone release slow?
It relies on the rate of production as they are not stores in the cells of the gland
How do steroid hormones circulate on the blood?
Bound to albumin as they are all derived from fat soluble lipids
What is the general structure of a steroid?
X3 six carbon ring structures
X1 five carbon ring structure
What are amine hormones?
They are hormones derived from tyrosine
Give examples of amine hormones.
Catecholamines
Thyroid hormones (T3 and T4)
How are thyroid hormones stored?
In the thyroid bound to thyroglobulin
How are thyroid hormones found in blood?
Circulating bound to proteins as they are lipid soluble
How do the catecholamines circulate in blood?
Freely and unbound as they are are water soluble
What fourth, smaller group of hormones do thromboxane and prostaglandins fall under?
Eicosanoids
What generic precursor are ecosanoids synthesised from?
Arachidonic acid
Which groups of hormones are linked to neurosecrectory cells?
Proteins and catecholamines
Where will the receptor be found for protein and catecholamines hormones?
Why?
On the cell surface as these type of hormones are polar therefore can not cross lipid membranes
Where will the receptor be found for steroid and thyroid hormones?
Why?
Intracellularly and these type of hormones are lipid-soluble (non-polar) therefore can cross the lipid membrane
What is another name for the anterior pituitary?
Adenohypophosis
What is another name for the posterior pituitary?
Neurohypophysis
From what buffalo cavity outgrowth does the anterior pituitary form?
Rathke’s pouch
From what does the posterior pituitary evaginate from to form?
The diencephalon (forebrain)
How is posterior pituitary hormone release controlled?
Directly from neural projections from the hypothalamus
Which X2 nuclei are involved in posterior pituitary control?
PVN = paraventricular nuclei
SON = supraorbital nuclei
What connects the hypothalamus with the posterior pituitary gland?
A pituitary stalk called the infundibulum
What hormones does the posterior pituitary secrete?
ADH and oxytocin
In which hypothalamic nuclei is ADH synthesised?
PVN and SON
In which hypothalamic nuclei is oxytocin synthesised?
PVN only
What stimulates ADH release?
High plasma osmolarity, decreased blood volume and decreased blood pressure (in that order)
What stimulates oxytocin release?
Cervix stretching
How is anterior pituitary hormone release controlled?
The hypothalamus synthesises and secretes releasing factor hormones into the surrounding vessels which then triggers anterior pituitary synthesised hormones to be released.
Through which network of vessels does the hypothalamus trigger anterior pituitary hormone releases?
The pituitary portal system
Where do the nerve axons for releasing factor release into the pituitary portal system terminate?
At the median eminence at the base of the hypothalamus
How many hormones does the anterior pituitary synthesise and release?
How many of these are trophic? Can you name these?
What does trophic mean?
Which hormone of the anterior pituitary is not trophic?
X6
X5
- thyroid stimulating hormone
- follicle stimulating hormone
- adrenocorticotrophic hormone
- leutinising hormone
- growth hormone
Tropic = stimulates other endocrine glands downstream
Prolactin = NOT trophic
What are the X6 hypothalamic hypophysiptrophic hormones?
What doe each of these stimulate?
1) thyroid releasing hormone = TSH
2) dopamine = inhibits prolactin
3) corticotrophic releasing hormone = ACTH
4) gonadotropin releasing hormone = LH and FSH
5) growth hormone releasing hormone = GH
6) somatostatin = inhibits GH
Why are hypothalamic hypophysiotrophic hormones difficult to measure?
They are only released in small amounts therefore are almost undetectable at a wider circulatory level
