Endocrine system Flashcards
1
Q
What are the patterns of hormone secretion (3)
A
- Episodic secretion - different at certain points of the day (daily)
- diurnal variation - monthly
- set point regulation - different at different points of life cycle (over years)
2
Q
What is the endocrine axis
A
Cascade effect allows amplification of signal in very small amounts
3
Q
what are the primary endocrine glands (8)
A
- pineal gland
- hypothalamus
- pituitary gland - anterior and posterior
- thyroid and parathyroid glands (parathyroid within thyroid but has a distinct endocrine function)
- thymus
- adrenal gland
- pancreas
- Reproductive endocrine glands
4
Q
What are the secondary endocrine glands (6)
A
- skin
- heart
- liver
- stomach
- kidney
- small intestine
5
Q
What are the different roles of hormones (5)
A
- intracrine - hormone acts inside a cell binding to receptors in the cell
- autocrine (local) - hormone that binds to receptors on the outside of the same cell
- paracrine - hormone secreted by cells acting on adjacent cells
- endocrine (whole-body response, hormone travels long distance)- a hormone is secreted by endocrine glands to distant target cells
- neuroendocrine - neurosecretory cell releases hormones to distant target cells
6
Q
What are the types of chemical signalling (3)
A
- Synaptic
- Paracrine
- Endocrine
7
Q
What is synaptic chemical signalling (3)
A
- presynaptic cell releases hormones to receptor
- receptor becomes activated
- activated effector molecules enter the postsynaptic cell
8
Q
What is paracrine chemical signalling (3)
A
- presynaptic cell releases hormones to receptors on neighbouring cells
- receptors become activated
- activated effector molecules enter the neighboring postsynaptic cells
9
Q
What is endocrine chemical signalling (3)
A
- presynaptic cell releases hormones into the bloodstream
- hormones bind to receptors on a distant cell, activating it
- activated effector molecules enter the distant postsynaptic cell
10
Q
What are the hypothalamic - anterior pituitary hormones
A
- Dopamine → prolactin
- TRH → TSH → T3, T4
- CRH → ACTH → cortisol
- Somatostatin → GH → liver IGF
- GHRH → GH → liver IGF
- GnRH → FSH → sex hormones
11
Q
What is the function of the adrenal glands (2)
A
- Inner medulla = adrenaline /noradrenaline - fight or flight
- Outer cortex = cortisol/aldosterone - blood pressure, salt, kidney function & fluid concentration
12
Q
What are the side effects of long-term systemic corticosteroid exposure (7)
A
- Neuropsychiatric - minor mood changes, depression, anxiety
- Ophtalmologic - cataracts, glaucoma
- Dermatologic - skin atrophy, ecchymosis, acne
- Metabolic/endocrine - hyperglicemia, dsylipidemia, weight gain, adrenal suppression
- Musculoskeletal - osteoporosis, fracture, myopathy
- Cardiovascular - hypotension, CHD, ischemic heart disease, heart failure
- Gastrointestinal - nausea, vomiting
13
Q
How is the growth hormone secreted (3)
A
- Hypothalamus GHRH & GHIH
- Anterior pituitary GH
- Multiple tissues, adipose tissue, muscle & liver
14
Q
What are the effects of the growth hormone (4)
A
- Multiple tissues = cell division, growth promotion
- Adipose tissue = glucose uptake, lipolysis
- Muscle = glucose uptake, amino acid uptake
- Liver = IGF secretion
15
Q
What are the classifications of hormones (3)
A
- Protein and peptide hormones
- Steroid hormones
- Tyrosine derivatives
16
Q
What are the amino acid-derived hormones (4)
A
- Thyroid = double tyrosine with 3 or 4 iodine atoms, inactivated by deiodinases - half life = days
- Catecholamines = derived from tyrosine - half life = minutes
- Serotonin & melatonin = tryptophan
- Histamine = glutamic acid
17
Q
What are steroid hormones (6)
A
- Derived from cholesterol
- Cholesterol → pregnenolone
- Half-life = several days
- eliminated by inactivating metabolic transformations
- Excreted in urine or bile
- Diffuse out of cell and do not require a specific secretory mechanism
18
Q
What are thyroid hormones (4)
A
- T4 had iodine at 5’ T3 does not
- T4 = most abundant product of the thyroid
- T4 = pro-hormone, converts into T3
- Secreted under the direction of TSH or thyrotropin
19
Q
What are peptide hormones (3)
A
- Synthesised by cells with many rER and Golgi apparatus
- Secreted by exocytosis
- Exocytosis is triggered by increased calcium levels of cellular depolarisation.
20
Q
How does the secretion of thyroxine differ
A
- Levels change over weeks/months
- Due to the long half-life
21
Q
How are cellular responses generated for peptide and steroid hormones (2)
A
- Peptide hormone → membrane receptor → second messenger → cellular response
- Steroid hormone → intracellular receptor → cellular response
22
Q
What are the different receptor types (4)
A
- Channel linked - Calcium = GnRH = LH & FSH
- Enzyme-linked = Insulin
- G-protein coupled = majority of hormones (insulin, glucagon & oxytocin)
- Intracellular = steroid and TH hormones
23
Q
What are examples of second messenger hormones (7)
A
- Cyclic AMP
- Adrenaline and noradrenaline
- glucagon
- thyroid-stimulating hormone
- calcitonin
- parathyroid hormone
- antidiuretic hormone
24
Q
What is the steroid hormone action (5)
A
- steroid hormone passes through plasma membrane
- steroid hormone binds to specic receptor protein in the cytoplasm or nucleus
- hormone-receptor complex enters the nucleus and binds to DNA causing gene transcription
- Protein synthesis is induced
- Protein is produced
25
What is the thyroxine mechanism of action (5)
1. Thyroxine (T4) is secreted by the thyroid to the bloodstream binding to transport proteins
2. In the target tissue T4 is converted to T3 by deiondinases
3. T3 and some T4 enter target cells by diffusing through the membrane or transporter proteins
4. T3 binds to thyroid hormone receptors (THRs) in the nucleus
5. T3 triggers conformational change initiating the transcription of target genes that regulate cellular processes
