hormonal communication

What is endocrine communication

Specialised glands secrete hormones into the bloodstream, circulatory system carriers hormone to target cell/tissue, lipid soluble soluble steroid hormones diffuse into cell and bind to complementary receptor in cytoplasm, peptide hormones bind to complementary receptor on cell surface membrane

What are hormones

Signalling molecule that are released into blood plasma from endocrine glands with specific target cells on which they act by binding to glycoproteins on the extracellular side of plasma membrane

What do exocrine glands secrete

Secret substances via ducts straight to targets cells on epithelial layers of internal or external body surfaces eg sweat glands, salivary glands, instead of hormones

Describe structure of adrenal glands

Located above kidneys, have cortex on outside and medulla in middle with lots of blood vessels

What hormones does the adrenal medulla secrete

Adrenaline, noradrenaline

When does the adrenal medulla secret adrenaline and noradrenaline

When the sympathetic nervous system is stimulated when the body is stressed

What are the effects of adrenaline

Increases blood glucose levels by converting glycogen to glucose in the liver, increases heart rate to send blood quickly to heart and brain, reduces blood flow to non essential organs eg digestive syste,

Using the secondary messenger model how does adrenaline result in an increase in blood glucose conc

Adrenaline bonds to membrane receptor, activates G protein, activated adenyl cyclase enzyme, adenyl cyclase catalyses conversion of ATP to cyclic AMP, cAMP stimulate the hydrolysis of glycogen to glucose

What are the effects of noradrenaline

Works with adrenaline in response to stress, widens air passages in lungs, increases heart rate, narrows blood vessels in non essential organs leading to higher blood pressure

What hormones does the adrenal cortex secrete

Mineral corticoides, glucocorticoids, androgens

What controls the production of hormones from the adrenal cortex

Controlled by hormones released from the pituitary gland

What is an example of mineralcorticoids and give its function

Aldosterone which targets kidney and gut to control concentration of Na+ and K+ ions in the blood, also helps control blood pressure by maintain balance between water and salt conc in body and body fluids

What signals the release of aldosterone

The kidney

What are examples of glucocorticoids

Cortisol and corticosterone

What is the role of cortisol

Helps regulate metabolism by controlling how body converts fats, proteins and carbs to energy, helps regulate BP and cardiovascular function in response to stress

How does corticosterone work

Release is controlled by the hypothalamus, works alongside cortisol to regulate immune response and suppress inflammatory reactions

What are androgens and what is their role

Are small amounts of sex hormones particularly important for women after the menopause howere impact is relatively mall compared to larger amounts of other sex hormones eg oestrogen and testosterone

Describe histology of pancreas

Made up of alpha and beta cells in islet of langerhans, alpha cells and larger and more numerous than beta, IoL appear lightly stained as large spherical clusters, the pancreatic acini appear darker and like small berry like clusters → is exocrine tissue

What hormone do alpha cells release

Glucagon

What hormone do the beta cells release

Insulin

What is the majority of the pancreas made up of

Exocrine glandular tissue, pancreatic acini, responsible for producing digestive enzymes and pancreatic juice

Why is it important that blood glucose concentration remains stable

To maintain blood water potential (prevents osmotic lysis/ crenation of cells), to maintain constant concentration of respiratory substrate (organism maintains a containt level of activity regardless of environment conditions )

Define negative feedback

Self regulatory mechanisms which return internal environments to optimum when there is a fluctuation

Glycogenesis

When the liver converts glucose into the storage polymer glycogen

Glycogenolysis

Liver hydrolyses glycogen into glucose which can diffuse into the blood

Gluconeogenesis

Liver converts glycerol and amino acids into glucose

Outline the role of glucagon when blood glucose concentration decreases

Alpha cells in islets of langerhans in pancreas detect decrease and secrete glucagon into bloodstream, glucagon binds to the surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis, glucose diffuses from liver into bloodstream, alpha cells detect the blood glucose concentration has returned to optimum and stop producing glucagon

Using the secondary messenger model explain how glucagon works

Hormone receptor complex forms, conformational change to receptor activate G protein, activated adenyl Cyclase which converts atp to cyclic AMP, cAMP activates protein kinase A pathway which results in glycogenolysis

What happens when blood glucose concentration increases

Beta cells in islets of langerhans in pancreas detect and secrete glucagon into insulin into bloodstream, insulin bind to surface receptors on target cells to increase cellular glucose uptake, activate enzymes for glycogenesis and stimulate adipose tissue to synthesis fat

How do beta cells control insulin secretion

Cell membrane has potassium and calcium ion protein channels, K+ channels are normally open so flowout of B cell, when glucose conc I high, glucose moves into cell, is metabolised to form ATP, ATP closes the K+ channels, causes a build up of K+ which alters the potential difference across the cell member (depolarisation), the change in PD causes the Ca2+ channels to open, Ca2+ ions cause vesicles of insulin to travel via cytoskeleton and fuse with cell membrane releasing insulin via exocytosis

How does insulin lead to a decrease in blood glucose concentration

Increases permeability of cells to glucose, increases glucose concentration gradient, triggers inhibition of enzymes for glycogenolysis // insulin binds to receptor in plasma membrane, receptor signal to cel and make vesicles carrying glucose transporters proteins to fuse with membrane, glucose can then diffuse down conc gradient and into cell

How is the pancreas an exocrine gland

Secretes digestive enzymes eg amylase, trypsin and lipase to the duodenum via the pancreatic duct

What does amylase break down

Starch to simple sugars

What do proteases eg trypsin break down

Proteins to amino acids

What do lipases break down

Lipids to fatty acids and glycerol

How is thee pancreas an endocrine gland

Releases hormones into the blood

What cause T1 diabetes

Body can’t produce insulin due to autoimmune response which attacks the beta cells of the islets of langerhans

How is T1 diabetes controlled

By injecting insulin from an animal source of genetically modified bacteria

What are the advantages of making insulin using GM bacteria

Human insulin is produced in a pure form so less likely to cause allergic reactions, insulin can be produced in larger quantities, production costs are cheaper, concerns over using animal products are overcome

What are the advantages of using stem cell therapy for t1 diabetes

Donor avaibality is not an issue as stem cells produce unlimited source of new beta cells, reduced likelihood of rejected as embryonic stems cells aren’t generally rejected, no longer have to inject insulin

Totipotent stem cells

Have ability to grow into any type of body cell

What are some negatives of using stem cell therapy

Early human embryo has to be destroyed however would usually be a “spare” from IVF,

What cause T2 diabetes

Glycoproteins are damaged or become less responsive to insulin, strong positive correlation with poor diet/ obesity

How is T2 diabetes controlled

By controlling diet and an exercise regime