endocrine system assignment 1

Question 1

what are hormones?

Answer 1

control metabolic activities

bind to receptors and induce a change in gene expression or cell function

Question 2

what are the hormones derived from the amino acid tyrosine?

Answer 2

thyroid hormones (thyroxine, triiodothyronine)
catecholamines ( epinephrine, norepinephrine, dopamine)

Question 3

name the hormones derived from the amino acid tryphtophan?

Answer 3

serotonin

melatonin

Question 4

what are the differences between peptide hormone and steroid hormone?

Answer 4

peptide hormones:
polar, cannot pass through plasma membrane
freely travel in the blood stream, no need of special carriers
bind to extracellular receptors and trigger the transmission of second messengers

steroid hormones:
can pass through plasma membrane
insoluble in blood and carried by specific proteins
bind to intracellular/ intranuclear receptors
remain in circulation longer than peptide hormones since transported by carrier proteins

Question 5

name the second messengers used in peptide hormone activation mechanism

Answer 5

cyclic adenosine monophosphate (cAMP)
cyclic guanosine monophosphate (cGMP)
calcium (Ca 2+)

Question 6

differentiate up and down regulation

Answer 6

up regulation:
low levels of hormone–> cells become more sensitive–>increase the number of hormone receptors

down regulation:
high levels of hormone–> cells become less sensitive–> decrease in number of hormone receptors

Question 7

what is the function of G-protein?

Answer 7

transmit signals from outside of a cell to the inside

Question 8

what is the function of the enzyme Adenylate cyclase?

Answer 8

it converts ATP to cAMP (cyclic Adenosine monophosphate)

Question 9

what is meant by phosphorylation?

Answer 9

this is when an enzyme attaches a phosphate group to another molecule

Question 10

name the hormones in which Ca ions act as a second messenger

Question 11

what is the effect of thyroid hormones bound to mitochondria

Answer 11

thyroid hormones bound to mitochondria affect the rate of ATP production

Question 12

give the different steps in the formation of Thyroxine

Answer 12

Thyroid Releasing Hormone (TRH)–> anterior pituitary–> thyroid stimulating hormone (TSH)–>thyroid gland–> thyroxine and triiodothyronine

Question 13

what are the different stimuli which trigger endocrine reflexes? give examples

Answer 13

1. Humoral stimuli 
       changes in ECF composition, Ca2+
2. Hormonal stimuli
        arrival or removal of a hormone
3. Neural stimuli
        neurotransmitters at neuroglandular or neuromuscular junctions

Question 14

what primary factor determines each cell’s hormonal sensitivities

Answer 14

depends on the presence or absence of specific receptors

Question 15

if a person was dehydrated, how would the amount of ADH released by the posterior pituitary lobe change

Answer 15

it would release more ADH

Question 16

which hormone is responsible for the production of somatomedins

Answer 16

growth hormone stimulates liver then synthesizes somatomedins

Question 17

give an example for positive feedback control of hormone

Answer 17

results in the secretion of tropic hormones which stimulate the production of other hormones

ovulation is the result of positive feedback

Question 18

what is the effect of elevated levels of cortisol on the secretion of Adrenocorticotropic hormone, ACTH, produced by the anterior pituitary

Answer 18

the secretion of ACTH is decreased

Question 19

which hormones are released due to the stimulation of sympathetic nervous system

Answer 19

epinephrine

norepinephrine