Revision card/Mistakes Flashcards
(42 cards)
Which of the following is NOT an endocrine gland?
Spleen
Adipose tissue, heart and kidneys have recently been identified as endocrine glands. Parathyroid is an example of a ‘classic’ endocrine gland.
Which statement regarding the endocrine system is correct?
hormones can affect more than one target organ
False: hormones are released into the bloodstream via ducts
Unlike the transmission of ‘messages’ by nervous system in which effects are limited to specific innervated cells only, effects of a hormone can be expressed on multiple target organs.
Is POMC a hormone?
NO
Choose the best option concerning the synthesis of steroid hormones.
NOT: StAR proteins transport synthesised cholesterol towards the cell membrane for secretion
cholesterol is obtained from the transport products of LDL via the action of esterase.
StAR proteins transport cytoplasmic cholesterol towards mitochondria for further modification to give cortisol. Fatty acid esters are broken down in the cytoplasm by esterase. Since steroid hormones are lipophilic, they diffuse through the cell membrane..
Is this statement true
thyroglobulin is used to transport ACTH.
ACTH is a protein/polypeptide hormone, hence does not need transporters.
Concerning the mechanism of action of ACTH, which statement is true?
is this false or true:
ACTH receptors are intracellular in nature
ACTH receptors are linked to G-proteins.
Energy is obtained from the dephosphorylation of ATP to cAMP by adenylate cyclase. Activated PKA up-regulates levels StAR proteins and fatty acid esters in the cell. ACTH receptors are located on the plasma membrane, unlike steroid hormones receptors which are found in the cytoplasm.
The lack of this substance during fetal development results in cretinism if untreated.
Cretinism occurs if untreated within a few months of birth. Fetal development and growth are some of the roles of iodothyronines. Iodothyronines are produced by the thyroid gland which is in turn stimulated by thyrotrophin.
Which of the following is NOT an effect of high circulating levels of prolactin?
erythropoiesis.
NOT:
- breast lactogenesis
- stimulation of T cells
- renal water reabsorption
- reduction in LH released
Which of the following suppresses the circulating levels of prolactin?
dopamine.
Thyrotrophins, suckling and oestrogens increase levels of prolactin while SS decreases levels of growth hormones.
Vasopressin (VP):
and oxytocin synthesis involve different neurophysins
Neurophysin is also breakdown product of pre-provasopressin in addition to glycopeptide and VP. VP stimulates water reabsorption. VP and oxytocin differ by 2 amino acids in their sequence and both are nonapeptides i.e. consist of 9 amino acids.
Vasopressin (VP):
and oxytocin synthesis involve different neurophysins
Neurophysin is also breakdown product of pre-provasopressin in addition to glycopeptide and VP. VP stimulates water reabsorption. VP and oxytocin differ by 2 amino acids in their sequence and both are nonapeptides i.e. consist of 9 amino acids.
Which physiological effect is NOT due to vasopressin?
insulin release
Oxytocin and its actions.
one stimulus of oxytocin release is mechanical i.e. suckling
Oxytocin acts on the myoepithelial cells of the breast (post partum i.e. during lactation) and the myometrium during partuition (contraction of the uterus).
With reduced insulin action,
hepatic glucose output is increased via glycogenolysis and gluconeogenesis.
Concerning the 2nd option: lipolysis is increased (not decreased) especially in omental fatty tissues, glycerol and NEFAs are produced. Concerning the 4th option: Atheroma formation is more widespread.
GLUT-4.
is this true:
consists of hydrophobic components in the cell membrane
is present in muscle and adipose tissue.
GLUT-4 is a channel (consisting of hydrophilic interior and hydrophobic exterior) carrying glucose INTO the cells. It is responsive to insulin and its actions are enhanced by insulin. Glucose uptake into cells is enhanced by a factor of 7.
In the liver
glycerol-3-phosphate is converted to glucose via gluconeogenesis
Which of the options is also known as thyroxine?
3,5,3’,5’-tetra-iodothyronine
Identify one of the two substances that undergo the coupling reaction to give T3 and T4.
T1 + T2 give a T3 while 2 T2s give a T4.
3,5,3’-tri-iodothyronine is T3, 3,5,3’,5’-tetra-iodothyronine is T4, 3-monoiodotyrosine globulin is T1 and 3,5-diiodotyrosine is T2.
This substance is the main product of the thyroid glands
3,5,3’,5’-tetra-iodothyronine
Deiodonation of this substance from its biologically reactive to inactive state gives the compound reverse T3 (rT3).
It is the deiodination of T4 by the appropriate deiodinase which produces rT3 so correct answer is, yet again, T4.
Corticotrophin releasing hormone (CRH) stimulates secretion of ACTH from the anterior pituitary. Which other substance from the hypothalamus potentiates the action of CRH?
vasopressins
This hormone is controlled by the neurosecretions dopamine and thyrotrophin releasing hormone (TRH
prolactins
The thyroid gland originates from
Thyroglossal duct.
The thyroid gland originates from the thyroglossal duct which itself originates from the foramen caecum.
Which of the following is a clinical feature of myxoedema:
Deepening voice is one of the features of primary hypothyroidism (myxoedema). Other common features are weight gain with reduced appetite, depression, tiredness, cold intolerance, bradycardia, and constipation