S6: haematology in systemic disease & introduction to the endocrine system + endocrine control of appetite

Question 1

Explain the common haematological abnormalities that can occur in patients with non-haematological systemic diseases

Answer 1

Anaemia can result from lack of response in the haemostatic loop eg. chronic kidney disease the kidney stops making erythropoietin
Anaemia can result from marrow being unable to respond to EPO eg. after chemotherapy
Anaemia of chronic disease eg. rheumatoid arthritis, iron is not made available to marrow for RBC production

Question 2

Describe anaemia of chronic disease due to iron dysregulation

Answer 2

Sufficient iron in the body but not available to the developing RBCs
Cytokines released by immune cells
Increased production of hepcidin by liver
Inhibition of ferroportin -> decreased iron released from RES system & decreased iron absorption in gut
Plasma iron reduced -> inhibition erythropoietin in bone marrow (anaemia)

Question 3

Describe the common causes and clinical significance of neutropenia, neutrophilia, lymphocytosis, and eosinophilia

Answer 3

Neutropenia (low neutrophils) = immunosuppression, autoimmune kidney disease, sepsis
Neutrophilia (high neutrophils) = bacterial infection, inflammation, steroids
Lymphocytosis (high lymphocytes) = viral infection
Eosinophilia (high eosinophils) = parasitic infections

Question 4

Describe the main features of control systems in the body

Answer 4

Stimulus
Receptor = detects stimuli
Afferent pathway
Control centre = determines set point
Efferent pathway
Effector = causes change

Question 5

List examples of biological rhythms

Answer 5

Circadian rhythm (biological clock in brain)
Eg. temperature, eating/drinking pattern, light

Question 6

Define the term ‘hormone’ and list the features of communication processes involving hormones

Answer 6

Hormones = chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
Autocrine: hormone signal acts back on the cell of origin
Paracrine: hormone signal carried to adjacent cells over a short distance via interstitial fluid
Endocrine: hormone signal released into bloodstream and carried to distant target cells
Neurocrine: hormone originates in neurone and after transport down axon released into bloodstream and carried to distant target cells

Question 7

List the classes of chemical substances which can act as hormones

Answer 7

1) Peptide/polypeptide = short chains of amino acids, all water soluble, eg. insulin, glucagon
2) Amino acid derived = synthesised from aromatic amino acids, adrenal medulla hormones water soluble, thyroid hormones lipid soluble eg. adrenaline, melatonin
3) Glycoproteins = large protein molecules, all water soluble eg. LH, FSH
4) Steroids = all derived from cholesterol, all lipid soluble eg. cortisol, aldosterone

Question 8

Describe how hormones are transported and act upon target cells

Answer 8

Some hormones travel in the blood but most hormones must bind to proteins to their target cells
Water soluble hormones bind to cell surface receptors
Lipid soluble hormones bind to intracellular receptors

Question 9

Explain the ways in which hormone secretion may be controlled

Answer 9

1) Rate of production
2) Rate of delivery
3) Rate of degradation

Question 10

Describe and outline the control of appetite

Answer 10

Appetite control centre (satiety centre) is in the hypothalamus
Arcuate nucleus plays a central role in controlling appetite
Two types of primary neurones: stimulatory neurones that promote hunger and inhibitory neurones that promote satiety
Primary neurones synapse with secondary neurones and the signals integrated to alter feeding behaviour

Question 11

Discuss the hormones involved in the control of appetite

Answer 11

Ghrelin = peptide hormone released from stomach wall when empty, stimulates appetite
PYY = short peptide hormones released by cells in the ileum and colon in response to feeding, suppress appetite, blunted PYY response following food intake in obese humans
Leptin = peptide hormone released into blood by fat cells, stimulates inhibitory neurones & inhibits the excitatory neurones, suppress appetite, induces expression of uncoupling proteins in mitochondria 
Insulin = supresses appetite 
Amylin = peptide hormone secreted by B cells in pancreas, suppress appetite, pramlintide is an amylin analogue for treatment of type 2 diabetes