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
Q
Which are the only cells in the body to have glucagon receptors?
A
- liver and fat cells
26
Q
How does glucagon increase blood glucose concentration?
A
-
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
Q
What is the negative feedback on blood glucose concentration?
A
- as glucose conc. returns to normal, alpha cells detect this
- when it rises above a set level, the secretion of glucagon is reduced
28
Q
How do insulin and glucagon work together to maintain a constant blood glucose concentration?
A
- 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
Q
What controls insulin secretion?
A
- 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
Q
What is hyperglycemia?
A
- 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
Q
What is type 1 diabetes?
A
- 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
Q
What is type 2 diabetes?
A
- 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
Q
What is the treatment for type 1 diabetes?
A
- 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
Q
What is the treatment for type 2 diabetes?
A
- 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
Q
What is medically produced insulin?
A
- 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
Q
What is the use of transplants in diabetes treatment?
A
- 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
Q
What are symptoms of diabetes?
A
- 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
Q
What is the use of stem cells in diabetes treatment?
A
- 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
Q
What are advantages of stem cells over current therapies?
A
- 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
Q
What is the fight or flight response?
A
- 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
Q
What happens when a change/threat is detected?
A
- 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
Q
What are the physiological responses of the fight or flight response?
A
- 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
