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A-level Biology > 5.14 - Hormonal communication > Flashcards

5.14 - Hormonal communication Flashcards

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1
Q

endocrine gland

A

a group of cells which are specialised to secrete hormones directly into the bloodstream
e.g. pancreas, adrenal glands

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2
Q

pituitary gland

A
  • base of brain
  • growth hormones that control growth of bones and muscles
  • ADH which increases reabsorption of water in the kidneys
  • gonadotrophins which control development of ovaries and testes
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3
Q

thyroid gland

A
  • produces thyroxine which controls rate of metabolism and the rate that glucose is used up in respiration and promotes growth
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4
Q

adrenal gland

A
  • on top of kidneys
  • produces adrenaline which increase heart and breathing levels and raises blood sugar level
  • made of two distinct parts, the adrenal cortex and the adrenal medulla surrounded by a capsule
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5
Q

testis

A
  • produces testosterone, which controls sperm production and secondary sexual characteristics
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6
Q

Pineal gland

A
  • brain
  • produces melatonin which affects reproductive development and daily cycles
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7
Q

Thymus

A
  • produces thymosin which promotes production and maturation of white blood cells
  • in chest
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8
Q

pancreas

A
  • produces insulin which converts excess glucose into glycogen in the liver
  • produces glucagon, which converts glycogen back into glucose in the liver
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9
Q

Ovary

A
  • produces oestrogen and progesterone, which controls ovulation and secondary sexual characteristics
  • progesterone also prepares the uterus lining for receiving an embryo
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10
Q

exocrine glands

A
  • secrete chemicals through ducts into organs or to the surface of the body
  • e.g. glands in the digestive system
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11
Q

steroid hormones

A
  • lipid souble
  • pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex in the cytoplasm or the nucleus
  • hormone-receptor complex acts as a transcription factor which facilitates or inhibits the transcription of a specific gene
  • e.g. oestrogen
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12
Q

non-steroid hormones

A
  • hydrophilic so cannot pass directly through the cell membrane
  • bind to specific receptors on the cell surface membrane of the target cell
  • triggers a cascade reaction mediated by chemicals called second messengers
  • e.g. adrenaline
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13
Q

hormonal vs nervous system

A

Hormonal:
- communication through chemicals
- transmission by blood system
- transmission usually relatively slow
- hormones travel to all parts of the body, but only target organs respond
- response is widespread
- response is slow
- response is often long lasting
- effects may be permanent and irreversible
Nervous:
- communication by nerve impulses
- transmission by neurones
- rapid transmission
- nerve impulses travel to specific parts of the body
- response is rapid
- response is localised
- response is short lived
- effect is temporary and reversible

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14
Q

adrenal cortex

A
  • outer region of adrenal glands
  • produces hormones that are vital to life such as cortisol and aldosterone
  • production of hormones controlled by hormones released from the pituitary gland
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15
Q

adrenal medulla

A
  • inner region of adrenal glands
  • produces non-essential hormones such as adrenaline (helps body react to stress)
  • hormones released when the sympathetic nervous system is stimulated (when the body is stressed)
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16
Q

Glucocorticoids

A
  • produced by the adrenal cortex
  • include cortisol which helps regulates metabolism by controlling how the body converts fats, proteins and carbohydrates to energy and helps regulate blood sugar cardiovascular function in response to stress
  • also includes corticosterone, which works with cortisol to regulate immune response and suppress inflammatory reactions
  • release of these hormones are controlled by the hypothalamus
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17
Q

Mineralocorticoids

A
  • produced by adrenal cortex
  • includes aldosterone which helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids
  • its release is mediated by signals triggered by the kidney
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18
Q

Androgens

A
  • released by the adrenal cortex
  • small amounts of male and female sex hormones are released
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19
Q

Adrenaline

A
  • secreted by the adrenal medulla
  • increases the heart rate sending blood quickly to the muscles and brain
  • rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
20
Q

Noradrenaline

A
  • secreted by adrenal medulla
  • works with adrenaline in response to stress, increasing heart rate, widening pupils, widening of air passages in the lungs, narrowing of blood vessels of non-essential organs (resulting in higher blood pressure)
21
Q

Function of pancreas

A
  • as an exocrine gland, to produce enzymes and release them via a duct into the duodenum
  • as an endocrine gland, to produce hormones and release them into the blood
22
Q

The pancreas as an exocrine gland

A
  • most of the pancreas is made up of exocrine glandular tissue
  • responsible for producing digestive enzymes and alkaline pancreatic juice
  • the enzymes and fluid are secreted into ducts that lead into the pancreatic duct
  • they are then released into the duodenum (top part of small intestine)
  • produce amylases that break down starch into simple sugars (e.g. pancreatic amylase)
  • produce proteases that break down proteins into amino acids (e.g. trypsin)
  • produces lipases that break down lipids into fatty acids and glycerol (e.g. pancreatic lipase)
23
Q

the pancreas as an endocrine gland

A
  • responsible for producing insulin and glucagon, which play an essential role in controlling blood glucose concentration
  • there are small regions of endocrine tissue within the exocrine glandular tissue called the islets of Langerhans
  • the cells of the islets of Langerhans are responsible for producing insulin and glucagon and secreting them into the bloodstream
24
Q

islets of Langerhans

A
  • large spherical clusters of endocrine tissue in the pancreas that secrete insulin and glucagon
  • contain alpha cells that produce and secrete glucagon
  • contain beta cells that produce and secrete insulin
  • when differential staining is applied to the tissue, the beta cells are stained blue and the alpha cells are stained pink
25
Q

increasing blood glucose concentration

A
  • Diet, carbohydrate rich foods such as pasta and rice (rich in starch) and sweet food such as cakes and fruit (high in sucrose) are broken down in the digestive system to release glucose, which is absorbed into the bloodstream
  • Glycogenolysis, glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream
  • Gluconeogenesis, the production of glucose from non-carbohydrate sources
    e.g. the liver can make glucose from glycerol and amino acids
26
Q

decreasing blood glucose concentration

A
  • Respiration, some of the glucose in the blood is used by cells to release energy. The higher the demand of physical activity, the higher the demand for glucose and the greater the decrease of blood glucose concentration
  • Glycogenesis, the conversion of excess glucose into glycogen in the liver
27
Q

Role of insulin

A
  • if the blood glucose concentration is too high, the beta cells of the islets of Langerhans in the pancreas detect this and respond by secreting insulin into the bloodstream
  • virtually all body cells have insulin receptors on their cell surface membrane. When insulin binds to its glycoprotein receptor, it causes a change in the tertiary structure of the glucose transport protein channels, causing them to open allowing more glucose to enter the cell
  • also activated enzymes in some cells to convert glucose into glycogen and fate
  • as blood glucose concentration returns to normal, this is detected by the beta cells. When it falls below a set level, the beta cells reduce their production of insulin (negative feedback)
28
Q

how does insulin reduce blood sugar concentration

A
  • increases rate of absorption of glucose by cells, especially skeletal muscle cells
  • increases respiratory rate of cells to increase their need for glucose, leading to a higher uptake from the blood
  • increasing the rate of glycogenesis (stimulates the liver to turn glucose into glycogen and store it in the liver and muscle cells)
  • increasing the rate of glucose to fat conversion
  • inhibiting the release of glucagon from the alpha cells
29
Q

role of glucagon

A
  • if the blood glucose concentration is too low, the alpha cells of the islets of Langerhans in the pancreas detect this and respond by secreting glucagon into the bloodstream
  • unlike insulin, the only cells in the body that have glucagon receptors are liver and fat cells, so these are the only cells that respond to glucagon
  • as blood glucose concentration returns to normal, this is detected by the alpha cells of the pancreas. When it rises above a set level, the alpha cells reduce their secretion of glucagon (negative feedback)
30
Q

how does glucagon raise blood sugar concentration?

A
  • Glycogenolysis, the liver breaks down its glycogen store into glucose and releases it back into the bloodstream
  • reducing the amount of glucose absorbed by the liver cells
  • increasing gluconeogenesis, increasing the conversion of amino acids and glycerol into glucose in the liver
31
Q

control of insulin secretion

A
  • at normal glucose levels, potassium channels in the plasma membrane of beta cells are open and potassium ions diffuse out of the cell. The inside of the cell has a potential of -70mV
  • when blood glucose concentration rises, glucose enters the cell by a glucose transporter
  • the glucose is metabolised inside the mitochondria, resulting in the production of ATP
  • the ATP binds to potassium channels and causes them to close (ATP-sensitive potassium channels)
  • as potassium ions can no longer diffuse out, the potential difference reduces to around -30mV and depolarisation occurs
  • depolarisation causes the voltage-gated calcium channels to open
  • calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis
32
Q

type 1 diabetes

A
  • the beta cells in the islets of Langerhans are unable o produce insulin
  • the cause is not yet known so the disease cannot be prevented or cured
  • normally begins in childhood and symptoms develop quickly
  • evidence suggests that in many cases the condition arises as a result of an autoimmune response attacking the beta cells
33
Q

type 2 diabetes

A
  • patients who have type 2 diabetes cannot effectively use insulin to control their blood sugar levels
  • either because their beta cells do not produce enough insulin or the person’s body cells do not respond properly to insulin
  • often because the glycoprotein insulin receptor on the cell membrane does not work properly
  • cells lose their responsiveness to insulin, so do not take up enough glucose, leaving it in the bloodstream
  • more common than type one diabetes
  • largely as a result of excess bodyweight, physical inactivity, excessive overeating of (refined) carbohydrates
  • risk of type 2 diabetes increases with age
  • symptoms similar to type 1, but are often less severe and develop slowly
34
Q

treatment of type 1 diabetes

A
  • controlled by regular injections of insulin
  • people have to regularly test their blood glucose concentration normally by pricking their finger
  • insulin injected increases the amount of glucose absorbed by cells and causes glycogenesis to occur, resulting in a reduction of blood glucose concentration
  • insulin is a protein, so cannot be taken by mouth as it would be digested
  • if too much insulin is injected, they may become hypoglycaemic (very low blood glucose) which can result in unconsciousness
  • too low an insulin dose can result in hyperglycaemia (very high blood sugar) which can also result in unconsciousness
35
Q

treatment of type 2 diabetes

A
  • regulate the person’s carbohydrate intakes through their diet and matching this to their exercise levels
  • overweight people often encouraged to lose weight
  • in some cases, diet and exercise are not enough to control blood glucose concentration, so drugs have to be used
  • includes drugs that stimulate insulin production, slow down the rate at which the body absorbs glucose from the intestine or insulin injections
36
Q

why are pancreas transplants rarely used in diabetes treatment?

A
  • demand for transplantable pancreases outweighs their availability
  • risk of having a transplant can also be a greater health risk than diabetes itself
  • immunosuppressant drugs used to prevent rejection increases the metabolic demand on insulin-producing cells, which eventually exhausts their capacity to produce insulin
37
Q

potential use of stem cells in diabetes treatment

A
  • as type 1 diabetes results from the loss of a single cell type (beta cells) and there is evidence that a relative small number of islet cells can restore insulin production, the disease is a perfect candidate for stem cell therapy
  • totipotent cells have the potential to grow into any of the body’s cell types
  • scientists researching the best type of stem cells and signals required to promote their differentiation into beta cells
  • cells would have to be obtained from destroying embryos, but each treatment does not require a separate embryo so donor availability would not be an issue, as stem cells can divide indefinitely
  • reduced likelihood of rejection problems
  • people no longer have to inject themselves with insulin
38
Q

fight or flights response

A
  • a set of physical response automatically triggered by the body when a potentially dangerous situation is detected
  • intended to help mammals survive by preparing the body to either run or fight
  • once a threat is detected by the autonomic nervous system, the hypothalamus communicates with the sympathetic nervous system and the adrenal-cortical system
  • the sympathetic nervous system uses neuronal pathways to initiate body reactions
  • the adrenal-cortical system uses hormones in the bloodstream
  • the combined affects of these two systems results in the fight or flight response
39
Q

fight or flight physiological responses

A
  • the sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release adrenaline and noradrenaline into the bloodstream
  • the hypothalamus stimulates the pituitary gland to secrete ACTH which travels in the bloodstream to the adrenal cortex, where it activates the release of hormones that prepare the body to deal with a threat
  • heart rate increases to pump more blood around the body
  • pupils dilate to take in as much light as possible for better vision
  • arterioles in skin constrict, so more blood goes to major muscle groups, brain, heart and muscles of ventilation
  • blood glucose level increases, to increase respiration to provide energy for muscle contraction
  • smooth muscles of airways relax to allow more oxygen in the lungs
  • non essential systems like digestion shut down, to focus resources on emergency functions
  • difficulty focusing on small tasks as brain is solely focused on where the threat is coming from
40
Q

action of adrenaline

A
  • trigger the liver cells to undergo glycogenolysis so glucose is released in the bloodstream to allow respiration to increase so more energy is available for muscle contraction in the flight or fight response
  • is a hydrophilic hormone, so cannot pass through cell membranes
  • when adrenaline binds with receptors on the surface of a liver cell, the enzyme adenylyl cyclase present in the cell membrane is activated
  • adenylyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner surface of the cell membrane in the cytoplasm
    -the increase in cAMP levels activates specific enzymes called protein kinases which phosphorylate/activate other enzymes
  • an enzyme activated triggers the conversion of glycogen into glucose
  • adrenaline is the first messenger and cAMP is the second messenger. One hormone molecule can cause many cAMP molecules to form.
41
Q

controlling heart rate

A
  • heart rate is involuntary and controlled by the autonomic nervous system
  • the medulla oblongata (brain) is responsible for controlling heart rate and making any necessary changes
  • two centres within the medulla oblongata linked to the SAN in the heart by motor neurones
  • one increases heart rate by sending impulses through the sympathetic nerous system transmitted by the accelerator nerve
  • one decreases heart rate by sending impulses through the parasympathetic nervous system transmitted by the vagus nerve
42
Q

two types of receptors which provide information that affects heart rate

A
  • baroreceptors (pressure receptors) detect changes in blood pressure. Present in the aorta, vena cava and carotid arteries
  • chemoreceptors (chemical receptors) detect changes in levels of particular chemicals in the blood such as carbon dioxide. Located in the aorta, carotid artery and the medulla
43
Q

how do chemoreceptors provide information that affects heart rate

A
  • sensitive to changes in the pH of the blood
  • if carbon dioxide levels in the blood increase from increased metabolic activity, the pH decreased because carbonic acid is formed where the carbon dioxide interacts with water in the blood
  • if the chemoreceptors detect a decrease in blood pH, a response is triggered to increase the heart rate
  • blood therefore flows more quickly to the lungs so the carbon dioxide can be exhaled
44
Q

how do baroreceptors provide information that affects heart rate

A
  • if blood pressure is too high, a response is triggered to decrease heart rate, bringing the blood pressure back to normal
  • if blood pressure is too high, a response is triggered to decrease heart rate, bringing the blood pressure back to normal
45
Q

heart rate - hormonal control

A
  • heart rate is also influenced by the presence of hormones
  • in times of stress, adrenaline and noradrenaline are released
  • they affect the pacemaker region of the heart itself by increasing the frequency of impulses produced by the SAN

A-level Biology (24 decks)

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