the endocrine system

Question 1

what does the endocrine system regulate

Answer 1

-development
-growth
-reproduction
-parturition (giving birth, +ve feedback)
-lactation
-metabolism
-blood pressure
-concentrations of ions in blood
-behaviour

Question 2

basic principles of endocrine signalling

Answer 2

-signalling molecules/mediators known as hormones are secreted from endocrine cells into the bloodstream
-endocrine cells: close proximity to capillary beds, found in endocrine tissues or glands
-endocrine glands don’t have ducts
-enables cell signalling across long distant target cells
-signalling is low
-signalling is specific to receptors but not specific to particular tissues/organs
-variety of locations of receptors meaning a variety of response
-hormones can be proteins (insulin), amino acid derived (adrenaline) or steroid (estradiol which is a type of oestrogen)
-hormone type influences its cell membrane permeability- dictating properties e.g. time of synthesis, released and receptor location

Question 3

type of hormone : synthesis

Answer 3

-peptides : from amino acids
-AA derived: derivatives of tyrosine (AA), requires a specific enzymes
-steroids : metabolites of cholesterol, requires specific enzymes

Question 4

type of hormone : release

Answer 4

-peptides : secretory granules, exocytosis
-AA derived: vesicles via exocytosis except thyroid hormone
-steroids: lipid soluble

Question 5

type of hormone: receptors

Answer 5

-peptides : cell membrane surface receptors
-AA derived: cell membrane surface receptors, except thyroid hormone
-steroids: diffuse into cells, bind to intracellular/ nuclear receptors

Question 6

type of hormone : response time

Answer 6

-peptides : seconds to a min
-AA derived: seconds to mins (except thyroid hormone)
-steroids: hours to days

Question 7

what are the 7 endocrine glands

Answer 7

1)pituitary- anterior and posterior
2) thyroid
3) parathyroids (4 smaller glands)
4) adrenals (cortex (outside) and medulla (in centre))
5) ovaries
6)testes
7) endocrine pancreas

Question 8

endocrine tissues

Answer 8

-hypothalamus
-kidneys
-GI tract
-heart
-liver
-adipose tissues
-all have endocrine cells in them but have other functions than just released hormones

Question 9

what’s the adenohypophysis

Answer 9

-located in anterior lobe of pituitary
-develops from an upward projection of the pharynx
-have shorter axons
-smaller diameter neurons
-troph cells stimulated by releasing hormones carried in the hypophyseal portal system from hypothalamic neurons
-portal system takes blood from one organ straight to another without it being re- oxygenated

Question 10

what’s the neurohypophysis

Answer 10

-located in the posterior lobe of the pituitary
-develops from a downward projection of the brain
-contains lots of different nuclei
-have 2 neurosecretory cells called supraoptic nucleus and paraventricular nucleus
-these cells release and spread neurohormones into intracellular fluid to travel around the body
-releases hormones from large diameter neurons directly into systemic circulation

Question 11

what’s does the thyroid gland do

Answer 11

-T3 and T4 AA derived hormones
-synthesis and release depends upon hypothalamic-pituitary hormones and iodine as iodine is needed in order to make thyroid hormone
-hormones bind to nuclear receptors and regulate transcription
-metabolism and development and growth is also regulated

Question 12

what does the parathyroid gland do

Answer 12

-contains parathyroid hormone (PTH)
-regulates plasma calcium and plasma phosphate
-targets bones, intestines and kidneys

Question 13

what’s a simple negative feedback loop

Answer 13

plasma [Ca2+] sense by chief cells
-increased plasma [Ca2+]
-this decreases PTH release
-this decreases kidney tubule reabsorption (less resorption means more calcium extracted)
-this decreases bone Ca2+ resorption
-which decreases intestinal Ca2+ absorption
-results in lower plasma [Ca2+]

Question 14

what does the adrenal gland do

Answer 14

-adrenal cortex releases steroid hormones: glucocorticoids e.g. cortical, and mineralcorticoids e.g. aldosterone
-adrenal medulla : neuronal properties, has chromatin cells which release adrenaline, and releases catecholamines such as adrenaline and noradrenaline

Question 15

what’s hierarchy control

Answer 15

-emotional/stress fat situation
-cortical control initiates release
-negative feedback loop: inhibition of the release of releasing hormone, inhibition of release of tropic hormone
-example: hypothalamic-pituitary-adrenocortical axis

Question 16

what does the endocrine pancreas do

Answer 16

-not exocrine (digestion)
-contains islets of langerhans: b cells release insulin, a cells produce glucagon, both released into portal blood to influence the liver

Question 17

simple negative feedback with the example of the endocrine pancreas

Answer 17

-increased blood glucose
-b cells of islets of langerhans release insulin
-liver= decreases glucose synthesis, muscle increase glucose synthesis
-decreases of blood glucose

Question 18

what do the gonads (ovaries ) do

Answer 18

-cells with the developing follicles of the ovary produce steroid hormones- oestrogen and progesterone

Question 19

what do the gonads (testes ) do

Answer 19

-leydig cells in the testes produce the steroid hormone testosterone
-stimulates protein synthesis
-can lead to development and growth