Introduction to Endocrinology Flashcards
look at endocrine axes
1
Q
What is the definition of a hormone?
A
- A hormone is a chemical messenger that is secreted directly into the blood by discrete specialised cells in response to a specific stimulus and which are transported to a distant target tissue where it exerts it specific effect
2
Q
What does Ernest Starling state about hormones?
A
- mediate cell to cell communication
- regulate physiological processes
- maintain homeostasis
3
Q
There are various endocrine glands in the body - What are they responsible for?
A
- for hormone production
4
Q
What do endocrine glands secrete?
A
- secrete hormones into the bloodstream
5
Q
Other than endocrine glands what can also produce hormones?
A
- organs
- tissues
6
Q
What are primary endocrine tissues like?
A
- tissue is solely endocrine in nature
7
Q
What are examples of primary endocrine tissues?
A
- pituitary gland
- adrenal gland
8
Q
What are secondary endocrine glands?
A
- tissues combine, major endocrine function with related functions
9
Q
What are examples of secondary endocrine tissues?
A
- hypothalamus
- pancreas (insulin)
10
Q
What are tertiary endocrine tissues?
A
- tissues has only a minor endocrine function with a major primary functions
11
Q
What are examples of tertiary endocrine tissues?
A
- ovaries which release oestrogen and then the growth of follicles
- kidney main function is filtration but also secretes some hormones
- the heart
- the intestines
12
Q
What is the function of a hormone?
A
- the function of a hormone is to regulate the activity of its target cells in a specific manner
13
Q
How does the endocrine glands maintain hormone function?
A
- they receive constant rapid information about the state of systems being regulated
14
Q
What does the endocrine glands receiving constant information ensure?
A
- ensures that the release of the hormone can be tailored to meet the requirements of the target cells
15
Q
How can hormones be tailored to meet requirements of target cells?
A
- this is achieved by feedback mechanisms, mainly negative feedback
16
Q
What do feedback systems allow for?
A
- the levels of hormones are tightly controlled, and homeostasis is maintained
17
Q
What are the classification of hormones?
A
- protein and peptide hormones
- steroid hormones derived from cholesterol
- amino acids derivatives
- fatty acids derivatives
18
Q
How are protein and peptide hormones synthesized?
A
- synthesised from amino acids
19
Q
What are protein and peptide hormones like in terms of size?
A
- they vary in size
20
Q
What is the structure of a peptide hormone?
A
- quite short
- consist of only single chain of few amino acids
21
Q
What is the structure of a protein hormone?
A
- larger chains of amino acids or consists of more peptide chains
22
Q
Where are protein and peptide hormones stored?
A
- stored in secretory vesicles until needed
- released upon a signal
23
Q
What is the size of a glycoprotein hormone?
A
- large molecule
24
Q
What are examples of glycoproteins?
A
- Gonadotrophins which include …
- luteinising hormone (LH)
- follicle stimulating hormone (FSH)
- thyroid stimulating hormone (TSH)
25
Where are gonadotrophins (glycoprotein peptide hormones) from?
- from the anterior pituitary
26
What is the structure of a glycoprotein peptide hormone?
- consists of two distinct peptide chains (called alpha and beta subunits) which are linked together by non-covalent bonds
27
What is the alpha subunit in a glycoprotein peptide hormone common to?
- LH
- FSH
- TSH
- chorionic gonadotrophin (CG)
28
In a glycoprotein peptide hormone what is the beta subunit responsible for?
- biological specificity
- which makes the hormone unique in function
29
What process do glycoprotein peptide hormones go through?
- they are glycosylated
30
What are steroid hormones?
- The steroids are a large class of lipids
31
Where are steroid hormones synthesized mainly and what is their common precursor?
- they are synthesised mainly in the adrenal cortex, testis, ovary and placenta from a common precursor which is cholesterol
32
Steroid hormones all have a common structure - what is this?
- consist of 3 six-membered rings and 1 five membered ring
33
Hormones can be derived from amino acids such as tyrosine which is a precursor for what hormones?
- adrenaline
- noradrenaline
- dopamine
- thyroid hormones = thyroxine (T4) and triiodothyronine (T3)
34
What are hormones derived from fatty acids called?
- eicosanoids
35
Hormones that have been derived from fatty acids have two major classes of messengers - what are these?
1. prostaglandins (PG's)
2. leukotrienes (LTs)
36
What are the messengers derived from in hormone derived fatty acids?
- derived from arachidonic acid (AA)
37
What type of lifespan do hormone derived from fatty acids have?
- short half-life act near the site of synthesis
38
Where are PG's formed?
- in most tissues of the body
39
The type of PG formed varies depending on what?
- on the type of down-stream enzymes present
40
PG's produced in the uterus have a role in what?
- have a role in embryo implantation and in foetal membranes
- role in parturition
41
PG's found in seminal vesicles promote what?
- sperm motility
42
How do hormones exert their effects?
- exert their effects by binding to receptors
43
What are the two types of hormone receptors a cell can have?
- cell-surface receptors
- intracellular receptors
44
What types of hormones would bind to cell-surface receptors?
- protein and peptide hormones
45
What type of hormone would bind to intracellular receptors and why would they bind?
- steroid hormones
- due to lipids being able to be taken into cells
46
What reproductive hormone is released by the hypothalamus?
- gonadotrophin-releasing hormone (GnRH)
47
What reproductive hormone is released by the pineal gland and what is this hormone associated with?
- melatonin
- associated with seasonality and breeding
48
What reproductive hormones are released by the anterior pituitary?
- LH
- FSH
- prolactin (milk secretion)
49
What reproductive hormone is released by the posterior pituitary and what is it important in?
- oxytocin
- important in parturition and milk let down
50
What reproductive hormones are released by the gonads?
- oestrogen and progesterone
- testosterone
51
What reproductive hormones are released by the placenta?
- oestrogens
- progesterone
- chorionic gonadotrophin
- prostaglandins (parturition)
52
What type of hormones are LH and FSH?
- gonadotrophins
53
What type of hormones are oestrogen and progesterone, and testosterone?
- steroids
54
What type of hormone is GnRH and what does it consist of?
- peptide hormone consisting of 10 amino acids
55
Where is GnRH synthesised?
- synthesised in the hypothalamus
56
What are GnRH derived from?
- derived from post-translation modification of precursor molecule
57
What type of manner are GnRH hormones secreted in?
- secreted in a pulsatile manner
58
What is the half-life of GnRH in a ewe?
- 7 mins
59
How does GnRH bind?
- binds to GnRH receptor on gonadotroph cells in anterior pituitary
60
How are gonadotrophins - LH and FSH secreted?
- secreted by gonadotroph cells in anterior pituitary, in response to GnRH
61
What type of molecules are LH and FSH?
- glycoproteins
62
What is the half-life of LH?
- 30 mins
63
What is the half-life of FSH?
- 3-4 hours
64
What receptors do LH and FSH bind to?
- bind to receptors in the gonads
65
Both LH and FSH have an effect on what?
- Will affect both testes and ovaries
66
What does FSH have an effect on?
- sperm production
- stimulation, growth, and maturation of follicle
67
What does LH effect?
- effects testes
- effects on ovulation, progesterone secretion and corpus lutetium formation
68
What are the gonadal steroids?
- progestins
- oestrogens
- androgens
69
What are the progestins?
- progesterone
- 17 alpha-hydroxyprogesterone
- 20 alpha hydroxyprogesterone
70
What are the oestrogens?
- oestradiol
- oestriol
- oestrone
71
What are the androgens?
- testosterone
- 5 alpha dihydrotestosterone
- androstenedione
- dehydroepiandrosterone
72
What does testosterone induce?
- induces and maintains differentiation of male somatic tissues
- induces secondary sex characteristics of males (deep voice, body hair, penile growth)
73
What does testosterone support?
- supports spermatogenesis (production of sperm)
74
What type of behaviour does testosterone influence?
- sexual
- aggressive
75
What does testosterone promote in the body?
- protein anabolism
- somatic growth
76
What does testosterone regulate the secretion of?
- regulates the secretion of gonadotrophins (negative feedback)
77
oestradiol stimulates the growth and activity of what?
- mammary gland
- endometrium
78
What does oestradiol prepare the uterus for?
- spermatozoal transport
79
What does oestradiol prepare the endometrium for?
- prepares endometrium for progesterone action (i.e., induce progesterone receptors)
80
What does oestradiol increase?
- increases vascular permeability and tissue oedema
81
What does oestradiol regulate the secretion of?
- regulates the secretion of gonadotrophins
82
What type of behaviour is oestradiol associated with in some species?
- sexual behaviour
83
What characteristics does oestradiol stimulate in females?
- secondary sex characteristics
84
What is oestradiol required for?
- normal physiological processes in the heart, muscle, bone, brain and liver
85
What does progesterone prepare the uterus for?
- to receive conceptus
86
What does progesterone do during pregnancy?
- depresses uterine activity
87
What effect does progesterone have on mammary glands?
- stimulates growth
- suppression on secretion of milk
88
What does progesterone promote the formation of?
- formation of non-penetrable cervical mucous
89
What effects does progesterone cause on the CNS?
- neuroprotective effects on CNS
90
Progesterone regulates the secretion of what?
- regulates gonadotrophin secretion through negative feedback
