B14 - Hormonal Communication Flashcards
1
Q
What is the endocrine system?
A
- made up of endocrine glands
- uses hormones to send information about changes in the environment around the body to bring about a response
2
Q
What are endocrine glands?
A
- group of cells which are specialised to secrete chemicals known as hormones directly into the bloodstream
- e.g. pancreas secretes insulin and glucagon and adrenal glands secrete adrenaline
3
Q
What are the functions of the glands (pituitary, thyroid, adrenal, thymus, pancreas)?
A
- pituitary:
- produces growth hormone, controlling growth of bones and muscles,
- ADH hormone which increases reabsorption of water in the kidneys
- gonadotrophins which control development of ovaries and testes
- thyroid:
- produces thyroxine which controls rate of metabolism and rate that glucose is used up in respiration
- promotes growth
- adrenal:
- produces adrenaline which increases heart rate and breathing rate
- raises blood glucose level
- thymus:
- produces thymosin which promotes production and maturation of white blood cells
- pancreas:
- produces insulin which converts excess glucose into glycogen in the liver
- glucagon which converts glycogen to glucose in the liver
4
Q
What are the functions of the gender specific glands (pineal, ovary, testes)?
A
women:
- pineal: produces melatonin which affects reproductive development and daily cycles
- ovary : produces oestrogen, which controls ovulation and secondary sexual characteristics (during puberty)
- progesterone: which prepares the uterus lining for the receiving an embryo
- men:
- testes (singular testis): produces testosterone which controls sperm production and secondary sexual characteristics
5
Q
What are exocrine glands?
A
- secrete chemicals through ducts into the organs or to the surface of the body
- e.g. digestive system
6
Q
What are hormones?
A
- chemical messengers that carry information from one part of the body to the other
- this includes:
- steroids (cortisol)
- proteins (insulin)
- glycoproteins (FSH)
- polypeptides (glucagon)
- amine (adrenaline)
- tyrosine derivatives (thyroid)
- ** they are chemically different but share similar characteristics **
7
Q
When are hormones secreted?
A
- in response to change in concentration of a substance e.g. blood glucose
- they are secreted directly into the blood when a gland is stimulated
- once secreted, they travel via the plasma across the body
- diffuse out of the blood and bind to specific hormone receptors (on membrane/cytoplasm of cells in the target organ)
- once bound to the receptors, the hormones stimulate the cells to produce a response
8
Q
What are steroid hormones?
A
- lipid soluble
- can pass through the lipid component of the cell membrane (can enter cell)
- binds to steroid hormone receptors (nucleus/cytoplasm) to form hormone-receptor complex
- the HRC formed acts as transcription factor which facilitates or inhibits the transcription of a specific gene (e.g. oestrogen)
9
Q
What are non-steroid hormones?
A
-
hydrophilic
- cannot pass through the cell membrane
- instead they bind to specific receptors on the cell surface membrane of the target cell
- triggers a cascade reaction which is mediated by chemicals called second messengers
- e.g. adrenaline
10
Q
What is the difference between hormonal and neuronal communication?
A
- hormones not directly released onto the target cells
- resulting in slower and less specific communication than neuronal
- hormones not broken down as fast as neurotransmitters
- so they have a longer lasting and widespread effect than neuronal communication
11
Q
What is the difference between the hormonal and nervous system?
A
- hormonal:
- communication is by chemicals (hormones)
- transmission by blood system (slow)
- hormones travel to all parts of the body (only target cells respond)
- widespread and long lasting response
- effect may be permanent/irreversible
- nervous:
- communication via nerve impulses
- transmission by neurons (rapid)
- nerve impulses travel to specific parts of the body
- localised and short-lived response
- effect is temporary/reversible
12
Q
What does the adrenal gland consist of?
A
- adrenal cortex - think ‘outside the CORE(tex):
- outer region of the glands
- produces cortisol (stress hormone)/aldosterone (water regulation)
- adrenal medulla:
- inner region of the glands
- produces non-essential hormones like adrenaline (stress)
13
Q
What is released by the adrenal cortex?
A
- controlled by hormones released by pituitary gland
- glucocorticoids:
- cortisol helps regulates metabolism by controlling conversion of fats, proteins and carbohydrates to energy
- helps regulate blood pressure/cardiovascular function
- another hormone is corticosterone (works with cortisol to regulate immune response/suppress inflammatory reactions)
- release is controlled by hypothalamus
- mineralcorticoids:
- aldosterone controls blood pressure by maintaining balance between salt and water concs. in blood/bodily fluids
- release mediated by signals triggered by kidney
- androgens:
- small amount of male and female sex hormones released
- impact is small compared to oestrogen and testosterone (released by ovaries and testes)
- important in women after menopause
14
Q
What is released by the adrenal medulla?
A
- hormones released by the sympathetic nervous system when the body is stressed:
- adrenaline:
- increases heart rate
- sending blood quickly to the muscles and brain
- rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver to use for energy
- noradrenaline:
- hormone works with adrenaline in response to stress
- causing increased heart rate (more oxygen transported around body)
- widening of pupils (to allow more light)
- vasoconstriction in non essential organs (increasing blood pressure)
- widening of air passages in lungs etc.
15
Q
What is the function of the pancreas?
A
- controls blood glucose conc. and helps with digestion
- glandular organ
- exocrine gland:
- to produce enzymes and release them via the duct into the duodenum (first part of small intestine, further absorbs what leaves the stomach)
- endocrine gland:
- to produce hormones and release them into the blood
16
Q
What is the function of the pancreas as an exocrine gland?
A
- mostly made up of exocrine glandular tissue
- responsible for producing digestive enzymes and alkaline fluid (pancreatic juice)
- enzymes and juices are secreted into ducts which lead to the pancreatic duct, then released into the duodenum (top of small intestine)
- produces 3 main hormones:
- amylase - breaks down starch into simple sugars e.g. pancreatic amylase
- proteases - break down proteins into amino acidse.g. trypsin
- lipases - breaks down lipids into fatty acids and glycerol e.g. pancreatic lipase
17
Q
What is the function of the pancreas as an endocrine gland?
A
- responsible for release of insulin and glucagon (help control blood glucose conc.)
-
within exocrine tissue there are small regions of endocrine tissue called *islets of Langerhans
- produce insulin and glucagon
- they are secreted directly into the bloodstream
18
Q
What is the difference between endocrine and exocrine glands?
A
- endocrine
- islets of langerhans
- lightly stained
- large, spherical clusters
- endocrine pancreas
- produce and secrete hormones
- exocrine:
- pancreatic acini (acinus singular)
- darker stained
- small, berry clusters
- exocrine pancreas
- produce and secrete digestive enzymes
19
Q
What are the types of cells in islets of Langerhans?
A
- α (alpha) cells:
- produce and secrete glucagon
- stained pink
- β (beta) cells
- produce and secrete insulin
- stained blue
- alpha cells are larger and more numerous than beta cells
20
Q
What reasons might cause blood glucose concentration to increase?
A
- diet:
- includes carb-rich foods (pasta/rice) and sweet foods (sucrose)
- they are broken down in digestive system to release glucose which is absorbed into the bloodstream
-
glycogenolysis: (splitting of glycogen)
- where glycogen in the liver/muscle is broken down into glucose
- released into the bloodstream
-
gluconeogenesis: (formation of new glucose)
- the production of glucose from non-carbohydrate sources
- e.g. from glycerol (lipids) and amino acids
- released into the bloodstream
21
Q
What reasons may cause blood glucose concentration to decrease?
A
- respiration:
- some of the glucose is used by cells to release energy
- during exercise, more glucose is needed for the muscles to contract
- higher level of physical activity = higher demand for glucose
-
glycogenesis: (formation of glycogen)
- where excess glucose is taken in through the diet and is converted into glycogen (stored in liver)
22
Q
Which cells do not have insulin receptors on their cell surface membrane?
A
- red blood cells
23
Q
What is the role of insulin?
A
- produced by beta cells in islets of Langerhans
- all body cells have insulin receptors on cell surface membrane
- when insulin binds to glycoprotein receptors, it causes a change in the tertiary structure of glucose transport protein carriers
- this allows more glucose to enter the cell
- it also activates enzymes to convert glucose to glycogen and fat
24
Q
How does insulin lower blood glucose concentration?
A
- increases rates of absorption of glucose by cells (skeletal muscle cells)
- increases respiratory rate of cells (increases glucose uptake)
- increases rate of glycogenesis by stimulating liver to remove glucose from the blood
- increases rate of glucose to fat conversion
- inhibits the release of glucagon from alpha cells of islets of Langerhans
- it is broken down by enzymes in liver cells
- depending on the food eaten, it will be secreted after a certain amount of time
- when blood glucose conc. returns to normal, the beta cells detect this and reduce their secretion of it (negative feedback)
25
Which are the only cells in the body to have glucagon receptors?
- liver and fat cells
26
How does glucagon increase blood glucose concentration?
- *glycogenolysis*:
- liver breaks down its glycogen store into glucose and releases it into bloodstream
- reduces amount of glucose absorbed by liver cells
- increases *gluconeogenesis*:
- increases conversion of amino acids and glycerol into glucose in the liver
- as blood glucose conc. returns to normal, alpha cells in pancreas detect thus
- when it rises above a set level, they reduce their secretion of glucagon (negative feedback
27
What is the negative feedback on blood glucose concentration?
- as glucose conc. returns to normal, alpha cells detect this
- when it rises above a set level, the secretion of glucagon is reduced
28
How do insulin and glucagon work together to maintain a constant blood glucose concentration?
- blood glucose conc. is self-regulating as level of glucose determines the quantity of insulin/glucagon released
- e.g. during stressful situations, adrenaline is released and increases blood glucose conc. to increase rate of respiration
- insulin:
- beta cells detect *rise* in blood glucose level
29
What controls insulin secretion?
- at normal blood glucose levels, K channels of beta cells are open
- potassium ions diffuse *out* of the cell
- potential of inside the cell is -70mV (millivolts)
- when blood glucose rises, glucose enters by glucose transporter
- glucose is then *metabolised* inside mitochondria
- production of ATP
- ATP binds to potassium channels and causes them to close
- they are ATP-sensitive potassium channels
- potassium ions can no longer diffuse out of the cell
- potential diff. reduces to around -30 mV (inside potential increases)
- so depolarisation occurs
- depolarisation causes voltage-gated (dependant on voltage) calcium ions to open
- calcium ions enter cell and cause secretory vesicles to release insulin by exocytosis
30
What is hyperglycemia?
- diabetes occurs when you are unable to metabolise carbohydrates properly (glucose)
- *hyperglycaemia* = raised blood sugar due to uncontrolled diabetes
- can lead to serious damage of many body systems (nerves and blood vessels)
31
What is type 1 diabetes?
- unable to produce insulin at all
- β cells in the islets of Langerhans do not produce insulin
- cause is unknown
- disease cannot be prevented or cured
- may be due to an autoimmune response where the body's own immune system starts attacking its β cells
- ** begins in childhood and people can develop symptoms of this disease quickly **
32
What is type 2 diabetes?
- cannot effectively use insulin to control blood sugar levels
- *glycoprotein* insulin receptors on cell membrane does not work properly
- cells lose responsiveness to insulin
- can be caused by excess body weight, physical inactivity, or overeating of refined carbohydrates
- similar symptoms to type 1 but are less severe and develop slowly
- so is only diagnosed *after* complications have arisen
- risk increase with age (but is now being seen in children recently)
33
What is the treatment for type 1 diabetes?
- controlled by regular injections of insulin and is *insulin-dependent*
- regularly check blood glucose conc. by pricking finger (blood drop is analysed by the machine)
- based on blood glucose level, they can determine the dosage of insulin needed
- insulin injected increases joint of glucose absorbed and causes *glycogenesis* (reduction of blood glucose conc.)
- inject too much insulin = hypoglycemia (very low blood glucose conc.) may occur
- insulin dose too low = hyperglycemia
- both can result in unconsciousness and maybe even death (hyperglycemia = too high blood glucose)
34
What is the treatment for type 2 diabetes?
- regulate carbohydrate intake through diet and matching this to exercise levels,
- lose weight if overweight
- sometimes drugs may be used
- includes those that stimulate insulin production
- drugs that slow down rate of glucose absorption from intestine
- even insulin injections may be used
35
What is medically produced insulin?
- structure of human insulin was identified and was made by genetically modified bacteria
- produced in a pure form so it reduces the chance of an allergic reaction
- produced in higher quantities
- production costs are much cheaper
- overcomes ethical/religious concerns (animal products)
36
What is the use of transplants in diabetes treatment?
- many type 1 diabetes patients receive pancreas transplants
- after a year, over 80% have no symptoms
- but the *demand* for transplantable pancreas outweighs their *availability*
- it also has a higher risk than diabetes itself (*immunosuppressant* drugs are needed to ensure body *accepts* the pancreas)
- injection of pancreatic *beta islet cells* has also been used to cure diabetes
- but fewer than 8% have been successful
- immunosuppressant drugs used to prevent rejection of these cells increases metabolic demand of insulin producing cells (exhausts capacity to produce it)
37
What are symptoms of diabetes?
- high blood glucose conc.
- glucose present in urine (cells don’t take it up)
- excessive need to urinate (polyuria)
- excessive thirst (polydipsia)
- constant hunger
- weight loss
- blurred vision
- tiredness
38
What is the use of stem cells in diabetes treatment?
- since type 1 is the loss of a single cell type (small no. of islet cells can be used to restore it)
- totipotent cells can grow into any body cell type
- stem cells are likely to be obtained from embryos which has to be destroyed (potentially destroying human life)
- but since spare embryos (infertility treatments/terminated pregnancies) are used they would have been destroyed anyways
- ** each treatment does not require one single embryo (can be used for many treatments) **
39
What are advantages of stem cells over current therapies?
- donor availability is not an issue (stem cells can produce an *unlimited* source of new beta cells)
- reduced likelihood of rejection problems
- embryonic cells are usually not rejected by the body
- stem cells can also be made by somatic cell nuclear transfer (SCNT)
- people do not need to inject insulin
- ** control of growth of the stem cells is limited so unlimited cell growth may result in the formation of tumours **
40
What is the fight or flight response?
- an example of the coordination between the nervous and endocrine system
- instinct that all mammals possess
- once a threat is detected by the *autonomic* nervous system, hypothalamus communicates with the *sympathetic* and *adrenal-cortical* system (nerve impulses/hormones)
41
What happens when a change/threat is detected?
- sympathetic nervous system send impulses to the glands and smooth muscles
- tells adrenal medulla to release adrenaline/noradrenaline (increased heart rate)
- release of other hormones from adrenal cortex is controlled by the release of hormones from *pituitary gland*
- hypothalamus stimulates the pit. gland to secrete ACTH
- travels in the bloodstream to adrenal cortex and activates release of many hormones
42
What are the physiological responses of the fight or flight response?
- heart rate increases
- pumps more oxygenated blood around the body
- pupils dilate
- allows more light in for better vision
- arterioles in skin constrict
- more blood is sent to major muscles (brain, heart, ventilation)
- blood glucose level increases
- increases respiration to allow for muscle contraction
- smooth muscle of airways relaxes
- allows more O2 into the lungs
- non-essential systems shut down
- focuses resources on emergency functions
- difficulty focusing on small tasks (not important)
- brain is solely focused on where threat is coming from
