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Biology > B14 - Hormonal Communication > Flashcards

B14 - Hormonal Communication Flashcards

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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
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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
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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
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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
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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
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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 **
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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
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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)
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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
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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
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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
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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)
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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
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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.
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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
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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
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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

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