Chapter 14 Hormones Flashcards
What is an endocrine gland?
A group of cells which are specialised to secrete hormones directly into the blood stream
What is an exocrine gland?
A group of cells which are specialised to secrete chemicals into ducts and to body surfaces
What is a hormone?
Chemical messengers which travel around the body in the blood stream
What are some examples of glands and the hormones they secrete?
Pituitary- Master Gland, stimulating e.g FSH, growth hormones, ADH
Thyroid- Thyroxine, contrast rate of metabolism
Ovaries/Testes- Oestrogen/Testosterone for secondary sex characteristics
What types of compounds can hormones be?
Steroids, Proteins, Glycoproteins, Polypeptides, Amines, or Tyrosine Derivatives
What are target cells?
Target cells contain receptors specific to a certain hormone, having a complementary shape, on the cell surface membrane or in the cytoplasm
What are the steps from when a hormone is produced to meeting the target cell?
Hormones are secreted into the blod stream from the gland when stimulated e.g by a nerve impulse
The hormone is transported in the blood plasma and diffuses out of the blood to bind to the complimentary glycoprotein receptor at the target cell
How do steroid hormones elicit a response? Give an example of a steroid hormone
Steroid hormones are lipid soluble, meaning they can pass through the cell surface membrane
They bind to their complimentary receptor in the cytoplasm or nucleus of the cell
The hormone-receptor complex acts as a transcription factor of the desired gene, causing transcription to begin, end, amplify, or dampen.
E.g Oestrogen
How do non-steroid hormones elicit a response? OCR. Give an example of a non-steroid hormone
Non-Steroid hormones are water soluble, so hydrophilic, so cannot pass through the cell surface membrane
They bind to a complementary receptor in the phospholipid bilayer
Changes to internal protein which activates adenylyl cyclase
Catalyses the conversion of ATP into cAMP
cAMP activates PKA, which can phosphorylate and activate enzymes for a cellular response
E.g Adrenaline
Compare hormonal and neuronal communication
Hormones vs nerve impulses
Bloodstream vs Neurones for transmission
Slow vs Fast
Widespread vs Specific
Long lasting vs short lived
Can be permanent vs temporary
Where is the adrenal gland located? What are the components of the adrenal gland?
On top of the kidney
Outermost layer= Capsule
Outer layer= Adrenal Cortex
Inner Layer=Adrenal Medulla
What types of hormones does the adrenal cortex secrete?
(Vital to life)
Glucocorticoids
Mineralocorticoids
Androgens
What hormones are glucocorticoids and what do they control?
What controls the secretion of these?
Cortisol regulates metabolism of the cell by controlling how fats/ proteins/ carbohydrates are converted to energy.
Helps regulate blood pressure and cardiovascular response to stress
Corticosterone + Cortisol regulates immune system and suppresses inflammation
Controlled by the hypothalamus
What hormones is a mineralocorticoid and what does it control?
What controls the secretion of this?
Aldosterone- controls blood pressure by controlling balance of salt/water in blood and body fluids
Release controlled by signals from the kidney
What are androgens and their role?
Male/Female sex hormones which are released in small amounts
Particularly important during menopause
Impact minimal compared to Oestrogen/Testosterone
What hormones are secreted by the adrenal medulla? When are they secreted?
Adrenaline and Noradrenaline
Released in times of stress, when the sympathetic nervous system is stimulated
What is the impact of adrenaline?
Increases heart rate
Divert blood to muscles and the brain
Converts glycogen to glucose in the liver, increasing blood glucose concentration (for increased respiration)
Increase breathing rate
(Works with noradrenaline)
What is the impact of noradrenaline?
Increasing heart rate
Widening pupils
Widening air passages of the lung
Narrowing blood vessels to non-essential organs, thus increasing blood pressure
(Works with adrenaline)
What is the exocrine function of the pancreas?
Secretes digestive enzymes such as amylases, proteases, and lipases, and alkaline pancreatic juice into small ducts
The small ducts travel into the pancreatic duct which travels to the duodenum (the top of the small intestine)
What is the function of the pancreas as an endocrine gland?
Regulates blood glucose concentration via secretion of glucagon and insulin
What is the structure of the pancreas?
Most of the pancreas is exocrine tissue, called pancreatic acini, appearing in smaller berry like clusters
Islets of langerhans are the endocrine tissue, appearing lighter and much larger in size.
Within this there are alpha and beta cells. Alpha cells are larger and more numerous, usually stained pink, and Beta blue
Within the pancreatic tissue, there are also pancreatic ducts, blood vessels, and connective tissue
There are capillaries within Islets of Langerhans
How can you tell the difference between blood vessels and pancreatic ducts in microscopy?
Blood vessels will have block coloured centres. They will be a different colour. If cross section, see blood vessel wall. Or if transect, see blood vessels through.
Pancreatic ducts will have the same colour as the acini and pale centres. Sometimes they are just white lines. They will be joined by other ducts feeding into it.
What is glycogenolysis?
The break down of glycogen into glucose
What is glycogenesis?
The formation of glycogen from glucose
What is gluconeogenesis?
The formation of glucose from non-carbohydrate sources, such as glycerol or amino acids
What factors affect blood glucose concentration?
Glycogenesis
Glycogenolysis
Gluconeogenesis
Diet- intake of carbohydrate sources, absorbed in the small intestine
Respiration- uses up cell glucose, take in blood glucose
Rate of absorption of glucose for cells
What is the base level of blood glucose?
70-100mg / 100cm3
Outline the flowchart for changes in blood glucose concentration
Decrease in blood glucose detected by alpha cells
Secrete glucagon- initiate measures. Paracrine, stops beta cells
Back to normal
Increase in blood glucose detected by beta cells
Secrete insulin, paracrine, stops alpha cells
Back to normal
How does insulin reduce blood glucose concentration?
Increases absorption of glucose into cells by causing changes in tertiary structure of glucose transport proteins
Increase respiration of cells, use up glucose
Increase glycogenesis
Inhibit alpha cells, gluconeogenesis and glycogenolysis, negative feedback
Which cells do insulin and glucagon target?
Insulin- all body cells
Glucagon- liver (hepatocytes) and fat cells
How does glucagon increase blood glucose concentration?
Increases glycogenolysis
Increases gluconeogenesis
Decreases absorption of glucose back into cells
Inhibits Beta cells, glycogenesis, negative feedback
Biochemically, how does glucagon work? What are the pathways used?
1) Glucagon binds to its complementary G
Protein Coupled Receptor, causing a tertiary change in the receptor
2) Conformational change promotes GDP to GTP with coupled G protein
3) Binding of GTP to G protein causes a conformational change, leading to the
dissociation of its subunits.
4) The subunits interact with Adenyl Cyclase. This promotes and CATALYSES the conversion of ATP into cAMP.
5) cAMP activates proteins like Protein Kinase A, PKA.
6) PKA phosphorylates enzymes and other molecules such as transcription factors responsible for glycogenolysis.
Cell response elicited.
How is insulin secreted?
1) With normal blood glucose concentrations, Potassium channels are open, and K+ ions diffuse of the cell. R.P = -70mv. ADP higher than ATP
2) When the blood glucose conc. rises, glucose enters the cell via glucose transport proteins (normally a low affinity)
3.) Glucose is metabolised at the mitochondria, meaning there is greater ATP than ADP.
4.) ATP binds to the ATP Sensitive Potassium channels, causing them to shut
5.) K+ can no longer diffuse out. -30mV. Depolarisation occurs.
6.) As a result, the voltage-gated Ca2+ channels open, allowing Ca2+ ions to diffuse in.
7.) Ca2+ ions bind to the motor proteins causing conformational changes, allowing them to move secretory vesicles containing insulin to move to the cell surface membrane, to leave via exocytosis.
Biochemically, how does insulin work? What pathways are involved?
1) Insulin binds to a Tyrosine Kinase Receptor, complementary to the hormone. This receptor has intrinsic enzyme activity.
2) The corresponding enzyme phosphorylates signalling molecules, activating them.
3.) These molecules then move vesicles containing glut-transporters to the cell surface membrane, increasing diffusion of glucose into the cell.
4.) Further mechanisms are initiated for glycogenesis and increasing respiration
What is type 1 diabetes and how is it currently treated?
Condition where the pancreas is unable to produce insulin. ONLY BETA CELLS damaged, but alpha cells not functioning. Likely caused by an autoimmune response targeting pancreatic cells.
Incurable, but treated with regular insulin injections, checking blood glucose conc regularly and apparently glucagon?
What is type 2 diabetes and how is it currently treated?
Condition where the cells cannot effectively use insulin or not enough insulin is produced.
Could be due to glycoprotein not function correctly
Risk factors include obesity, age, and a sedentary lifestyle.
Regulate carbohydrate intake, increase exercise, lose weight
Sometimes medicines to decrease glucose uptake , or insulin injections
How was and is medical insulin produced? What are the benefits to this method?
Originally from the pancreas of cows/pigs upon slaughtering but their was the risk of allergic reactions
Now isolation of gene for insulin in humans isolated, and genetically engineered into bacteria.
Pure. Produced in high quantities. Cheaper. And less ethical concerns. But can be difficult to use and side effects like hardening of skin.
How can stem cells be used to treat diabetes? What are the pros and cons of this treatment?
Totipotent stem cells, either differentiate before and inject, or insert and induce pathways, to turn into beta cells
Only a few cells needed to replicate later
Could be from ‘spare’ embryos, or umbilical cords
Unlimited source. Low risk of rejection. No need for insulin.
But ethical concerns and side effects may still be unknown.
How does adrenaline bind to a cell?
Adrenaline diffuses out of the bloodstream and binds to its glycoprotein receptor on the cell surface membrane of a cell
The shape of the glycoprotein receptor is complementary to the shape of adrenaline
What can you conclude about a hormone which has a complimentary receptor on a the cell surface membrane of the cell?
It is not lipid based / is polypeptide based
So a non-steroid hormone, which binds to its glycoprotein receptor
Cell signalling
Produces a secondary messenger within the cell to elicit a response
What should you include when drawing a biological drawing?
Completed lines
Annotations parallel to x axis
Only label what you see, with some annotiations
Colours of what you see
A good size
Scale and scale bar
Title and schedule scientific name
Magnification
When should a T-Test be used?
When you are comparing the means of two pieces of data
Why is the SD more useful than range ?
Less impacted by anomalies
Takes into account all data values
With comparing the effectiveness of medicines with diabetes, what factors should be assessed/controlled?
Type of diabetes
Age, Gender
Baseline blood glucose conc
How effective a treatments been- how can this be measured
How does the impact of steroid and non steroid hormones differ?
As steroid alter transcription of genes, longer lasting effect, but usually take longer to initiate
Non-steroid for faster response but short lived, continually generated e.g insulin
