L13 - Endocrine System

Question 1

What is endocrinology?

Answer 1

study of the homeostatic mechanisms that are controlled by hormones

Question 2

What is a hormone?

Answer 2

blood-borne chemical mediator released from endocrine glands that act on distant target cells

Question 3

What does endocrine refer to?

Answer 3

hormones which pass directly through to the blood stream e.g. insulin

Question 4

What does exocrine refer to?

Answer 4

hormones which pass through ducts e.g. digestive enzymes

Question 5

What are general principles of the endocrine system?

Answer 5

• endocrine glands may produce multiple hormones (pituitary) and hormones may be produced by multiple endocrine glands (sex steroids)
• hormones may have more than one target/function
• rate of secretion of some hormones varies in a cyclic pattern

Question 6

What does autocrine refer to?

Answer 6

self-regulating hormones which affect the cell that produced it

Question 7

What does paracrine refer to?

Answer 7

hormones which affect cells in the near vicinity (histamine)

Question 8

What affects the movement of hormones?

Answer 8

their permeability/solubility

hormones can be lipophilic or hydrophilic

Question 9

What is a neurohormone?

Answer 9

a neurocrine secreted into the bloodstream

Question 10

What are three major groups of neurohormones?

Answer 10

those from the anterior and posterior pituitary gland and catecholamines (made by modified adrenal medulla neurons)

Question 11

What are tropic hormones?

Answer 11

a hormone that controls the secretion of another hormone

often have names that end in tropin e.g. thyrotropin (TSH)

Question 12

What are the characteristics of lipophilic hormones?

Answer 12

act intracellularly as able to permeate target cell membrane

Question 13

What are the characteristics of hydrophilic hormones?

Answer 13

dissolvable in water/solution and target receptors on cell membrane

Question 14

What are the characteristics of nontropic hormones?

Answer 14

exert and effect directly on target cell/organ

Question 15

How are steroid hormones shuttled around the body?

Answer 15

via carrier proteins

Question 16

How do steroid hormones result in a response?

Answer 16

activate genes for transcription and translation; may have nongenomic actions

Question 17

From which molecules are steroid hormones produced?

Answer 17

cholesterol

Question 18

What are the characteristics of catecholamines?

Answer 18

made in advance (hydrophilic), dissolved in plasma, short half life, receptor located on PM, activation of second messenger systems (NA, A)

Question 19

What are the characteristics of thyroid hormones?

Answer 19

made in advance (lipophilic), bound to carrier proteins, long half life, receptor located on nucleus, activation of genes for transcription/translation (thyroxine)

Question 20

From which molecules are amines produced?

Answer 20

tyrosine

Question 21

What is the mechanism of action of peptides and catecholamines?

Answer 21

bind to surface receptors -> generate an intracellular signal or “second messenger” (hydrophobic)

Question 22

What is the mechanism of action of steroids?

Answer 22

altering gene expression and production of new proteins (lipophilic) e.g. thyroid hormones

Question 23

What are some of the influences on plasma/hormones concentration?

Answer 23

• the hormone’s rate of secretion by the endocrine gland (major factor)
• rate of metabolic activation (for a few)
• extent of binding to plasma proteins (for lipophilic)
• rate of metabolic inactivation/excretion (for all)

Question 24

How are steroid hormones removed from the body?

Answer 24

liver first makes it inactive then conjugation increases solubility in water

Question 25

How are amines removed from the body?

Answer 25

by specific circulating degrading enzymes

Question 26

How are large peptides removed from the body?

Answer 26

receptor-mediated endocytosis

smaller peptides = kidneys

Question 27

What are the different types of negative feedback control?

Answer 27

long loop and short loop negative feedback control

Question 28

How is hormone function regulated?

Answer 28

down-regulation e.g. target cell desensitisation
antagonism e.g. insulin and glucagon which act together but in opposite directions (fine-tuning)
synergism: multiple stimuli and effect is more than additive
permissive: first hormone cannot exert effect without presence of second e.g. cortisol and adrenaline

Question 29

What hormones does the anterior pituitary gland produce?

Answer 29

ACTH (adrenocorticotropin)
PRL, FSH, LH (reproduction)
TSH (thyroid)
GH (growth hormone)

Question 30

What hormones does the posterior pituitary gland produce?

Answer 30

Vasopressin (ADH) and Oxytocin

Question 31

What is decreased hormone activity caused by (hyposecretion)?

Answer 31

increased removal from blood and abnormal tissue response e.g. lack of receptors and lack of enzyme for cell response
treatment = hormone administration

Question 32

What is increased hormone activity caused by (hypersecretion)?

Answer 32

decreased removal from blood and decreased plasma protein binding
treatment = tumour removal, inhibiting drugs

Question 33

What is primary hypo/hypersecretion caused by?

Answer 33

abnormal gland

Question 34

What is secondary hypo/hypersecretion caused by?

Answer 34

normal gland; excessive stimulation