endocrine cell signalling

Question 1

describe autocrine regulation of the endocrine system

Answer 1

chemicals released from the cell binds to target receptors on the same cell. this is a negative feedback loop

Question 2

describe paracrine regulation of the endocrine system

Answer 2

chemicals released from the cells bind to receptors on adjacent cells.

Question 3

describe endocrine regulation - where the chemicals are transported

Answer 3

chemicals released form secretory cells are usually transported via the circulatory system to reach target cells to create a cellular response

Question 4

what is the classical definition of a hormone?

Answer 4

Any substance elaborated by one cell to regulate another cell. May be delivered by autocrine, paracrine, or endocrine routes

Question 5

how do hormones create a biological response?

Answer 5

generally the result of an amplification of a signal transduction cascade

Question 6

which endocrine gland provides the highest level of endocrine control?

Answer 6

hypothalamus

Question 7

how does the hypothalamus integrate activities of nervous & endocrine systems?

Answer 7

1) Secretion of regulatory hormones which control activity of anterior pituitary cells

2) Synthesises hormones & transports them to the posterior pituitary via the infundibulum

3) Direct neural control function: hypothalamic autonomic centres control secretion of Adrenaline & Noradrenaline by the adrenal medulla.

Question 8

what time is there a cortisol spike at?

Answer 8

around 9am

Question 9

how does diurnal control of hormone levels work?

Answer 9

responds to external cues e.g. light and dark causing fluctuations, and are influenced by rate of elimination in the body

Question 10

what are the 3 classes of hormones based on structure?

Answer 10

-steroid hormones (cholesterol backbone)
-amine-derived
-peptides

Question 11

what are examples of steroid hormones?

Answer 11

cortisol, oestrogen & testosterone

Question 12

what is an example of an amine-derived hormone?

Answer 12

adrenaline

Question 13

what are examples of peptide hormones?

Answer 13

oxytocin, growth hormone, insulin

Question 14

describe steroid hormones

Answer 14

Lipids derived from cholesterol
Synthesis rate controls amounts
Once synthesised steroids are secreted, they are not stored
Steroids are hydrophobic & lipophilic and are transported in blood plasma by binding to carrier proteins (~90%). ‘Free’ (or unbound) steroids are biologically active.

Question 15

where is cortisol secreted form and what does it do?

Answer 15

secreted from adrenal cortex plays a role in mediating stress responses

Question 16

how do steroid hormones work?

Answer 16

pass through plasma membrane initiating 2 step process:
1) Activated hormone-receptor complex forms within the cell
2) The complex binds to DNA & activates specific genes –> Gene activation leads to production of key proteins

Question 17

describe amine hormones

Answer 17

-Catecholamine Amine hormones are hydrophilic and are transported unbound or ‘free’ in blood plasma
-Thyroid amine hormones are bound to carrier proteins
-Secreted from thyroid & adrenal medulla
-Amines like adrenaline (epinephrine) stored as vesicles in the cytoplasm until needed
-Amine hormones bind to membrane bound receptors to evoke cellular responses

Question 18

describe peptide hormones

Answer 18

-Peptide hormones are hydrophilic and are transported unbound or ‘free’ in blood plasma
-Large majority of hormones produced
-Synthesised as precursor molecules and stored in secretory vesicles
-Different end hormones can be made by cleaving a common precursor with a different enzyme

Question 19

where are peptide hormones secreted from?

Answer 19

pituitary , parathyroid, heart, stomach, liver, kidneys

Question 20

what is the structure of peptide hormones?

Answer 20

May be composed of a ring structure due to disulfide bonds as in the case of somatostatin

may be composed of 2 chains e.g. insulin held together by disulfide bonds

Question 21

what do cortisol and thyroxine bind to in the blood?

Answer 21

Cortisol-binding globulin (CBG) – binds cortisol in a selective manner (also some aldosterone)

Thyroxine-binding globulin (TBG) – binds thyroxine (T4) selectively [also some triiodothyronine (T3)]