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A Level Biology > Hormonal Communication > Flashcards

Hormonal Communication Flashcards

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1
Q

What is an endocrine gland?

A

A group of cells which are specialised to secrete chemicals- eg hormones, into the blood.

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2
Q

Why are hormones referred to as chemical messengers?

A

Because they carry information from one part of the body to another.

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3
Q

Which part of the blood do hormones travel in?

A

The plasma

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4
Q

How do hormones reach their target cell?

A

Secreted directly into the blood

Transported in the plasma all throughout the body

Hormones diffuse out of the blood and bind to specific receptors

Receptors are found on plasma membranes or in the cytoplasm of target cells.

Once bound to their receptor a response is produced.

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5
Q

How do steroid hormones take effect?

A

Lipid solubles hormones.

Pass through the phospholipid part of cell membrane and bind to steroid hormone receptor to form a hormone-receptor complex.

Receptors may be present in the cytoplasm by or nucleus depending on the hormone.

Hormone receptor complex acts as a transcription factor which facilitates or inhibits the transcription of specific genes.

Eg Oestrogen works in this way.

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6
Q

How do non steroid hormones take effect?

A

They’re hydrophilic so cannot pass through the cell membrane.

Instead they bind to specific receptors on the cell surface membrane of the target cell.

This triggers a cascade reaction mediated by secondary messengers.

Eg the function of adrenaline.

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7
Q

Hormones vs neuronal communication. Differences?

A

Hormones are slower and less specific than neuronal communication.
Hormones can have a longer lasting and more widespread effect.

Hormone effect may be permanent or irreversible / neurones effect is temporary and reversible.

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8
Q

What is the adrenal cortex?

A

The outer region of the adrenal glands. This produces hormones that are vital to life such as cortisol and aldosterone.

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9
Q

What is the adrenal medulla and what does it do?

A

The inner region of the glands.

Produces the non essential hormones such as adrenaline which helps the body react to stress.

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10
Q

What are the 3 types of hormones produced in the adrenal cortex?

A

Glucocorticoids

Mineralcorticoids

Androgens

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11
Q

What is a glucocorticoid?

A

Includes cortisol which helps to regulate metabolism by controlling how the body conveys fats, proteins and carbohydrates into energy.
Also helps to regulate blood pressure and cardiovascular function in response to stress.

Corticosterone works with cortisol to regulate immune response and suppress inflammatory reactions.

Release of these is controlled by the hypothalamus.

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12
Q

What are mineralcorticoids and what do they do?

A

Main one is aldosterone which controls blood pressure by maintaining the balance between salt and water concentrations in blood and body fluids.

Mediated by signals triggered by the kidney.

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13
Q

What are androgens?

A

Small amounts of male and female hormones released - the impact being relatively small compared to larger amounts of hormones. Still important though especially in women after the menopause.

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14
Q

What hormones are secreted by the adrenal medulla?

A

Adrenaline

Noradrenaline

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15
Q

What does adrenaline do?

A

Increases heart rate sending blood quickly to the brain and muscles. Rapidly raises BGC by converting glycogen to glucose in the liver.

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16
Q

What does noradrenaline do?

A

Works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils, widening of air passages in the lungs and the narrowing of blood vessels in non essential organs (= higher blood pressure)

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17
Q

What are the 2 main functions of the pancreas?

A

As an exocrine gland - produce enzymes and release them via a duct in the duodenum

As an endocrine gland - to produce hormones and release them into the blood.

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18
Q

Describe the role of the pancreas as an exocrine gland?

A

Most of pancreas made up of exocrine glandular tissue. Tissue is responsible for producing digestive enzymes and an alkaline fluid known as pancreatic juice. The enzymes and Juice are secreted into ducts which lead to pancreatic duct, then released into duodenum (top of small intestine)

Pancreas produces;
Lipases
Amylases
Proteases

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19
Q

Describe the role of the pancreas as an endocrine gland?

A

Produces insulin and glucagon responsible for the regulation of BGC.

Within regions of exocrine system there are small regions of endocrine tissue called islets of langerhans.

The cells of the islets of langerhans are responsible for producing insulin and glucagon And secreting the hormones directly into the bloodstream.

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20
Q

What do islets of langerhans look like under the microscope?

A

Lightly stained

Large spherical clusters

Endocrine pancreas tissue

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21
Q

What do pancreatic acini look like under the microscope?

A

Darker stained, small berry like clusters

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22
Q

What are the 2 types of cells within the islets of langerhans?

A

Alpha cells

Beta cells

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23
Q

What do the alpha cells produce?

A

Produce and secrete glucagon

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24
Q

What do the beta cells produce?

A

Produce and secreted insulin.

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25
Q

How to tell the difference under a microscope?

A

Alpha cells are larger and more numerous than beta cells within an islet.

Use differential stain - beta cells are stained blue and alpha cells stained pink.

26
Q

What 3 things can increase BGC?

A

Diet

Glycogenolysis

Gluconeogenesis

27
Q

What is glycogenolysis?

A

Glycogen stored in the liver and muscle cells is broken down into glucose which is released into the blood stream increasing BGC

28
Q

What is gluconeogenesis?

A

Production of glucose from non carbohydrate sources. Eg the liver is able to make glucose from glycerol (lipid) and amino acids. This glucose is then released into bloodstream increasing BGC.

29
Q

How can BGC be reduced?

A

Respiration

Glycogenesis

30
Q

What is glycogenesis?

A

Production of glycogen. When BGC too high, excess glucose taken in through the diet is converted into glycogen which is stored in the liver.

31
Q

Describe the binding of insulin to its receptor?

A

When insulin binds to its glycoprotein receptor it causes a change in the tertiary structure of the glucose transport protein channels. This causes the channels to open allowing more glucose to enter the cell.

Insulin also activated enzymes within some cells to convert glucose into glycogen and fat.

32
Q

How does insulin lower BGC?

A

Increases the rate of absorption of glucose by cells

Increases respiratory rate in cells

Increases the rate of glycogenesis

Increases the rate of glucose to fat conversion

Inhibiting the release of glucagon from the alpha cells of the islets of langerhans

33
Q

Where is insulin broken down?

A

By enzymes in the cells of the liver. Therefore it has to be constantly secreted to maintain its effect.

34
Q

What cells detect BGC and how do they react to this?

A

When BGC returns to normal this is detected by the beta cells of the pancreas. When it falls below a set level, the beta cells reduce their secretion of insulin- and example of a negative feedback system.

35
Q

What do the alpha glucose cells detect?

A

Glucagon is produced by the alpha cells of the islets of langerhans in the pancreas. If the BGC is too low, the alpha cells detect the fall in BGC and respond by secreting glucagon directly into the bloodstream.

36
Q

Which cells in the body have glucagon receptors?

A

Liver cells and fat cells. Therefore these are the only cells that respond to glucagon.

37
Q

How does glucagon increase blood glucose concentration?

A

Glycogenolysis

Reducing the amount of glucose absorbed by the liver cells

Increasing gluconeogenesis

38
Q

Why is BGC system described as self regulating?

A

Because it is the level of glucose in the blood that determines the quantity of insulin and glucagon released

39
Q

Describe the mechanism of insulin secretion by beta cells?

A

At normal BGC, potassium channels in plasma membrane of B cells are open and potassium ions diffuse out. Inside of cell is at -70mV.

When BGC rises, glucose enters the cell by a glucose transporter.

The glucose is metabolised inside the mitochondria resulting in ATP production.

ATP binds to potassium channels and causes them to close. (ATP sensitive potassium channels)

Potassium ions can no longer diffuse out of the cell, the PD reduces to around -30mV and depolarisation occurs.

Depolarisation causes voltage gated calcium channels to open.

Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis.

40
Q

Describe type 1 diabetes?

A

Patients unable to produce insulin.
Beta cells in islet of langerhans do not produce insulin. Cause is not known and it cannot be prevented or cured, but symptoms can be treated.

Evidence suggests that an autoimmune response causes an attack on beta cells which inhibits their function.

41
Q

Explain type 2 diabetes?

A

Patients cannot effectively use insulin and control their blood sugar levels.
Either because the Beta cells do not produce enough insulin or the body cells do not respond properly to insulin.
Often the glycoprotein receptor on cell membrane doesn’t work properly and the cells lose their responsiveness to insulin and therefore do not take up enough glucose, leaving it in the blood stream.

42
Q

What can cause type 2 diabetes?

A

Excess body weight
Excessive overeating of refined carbs
Physical inactivity
Age and unhealthy habits.

43
Q

How is type 1 diabetes treated?

A

Controlled by regular injections and is said to be insulin dependent.

Testing of sugar levels must be done frequently by pricking their finger, the blood is then analysed by the machine that gives a reading of their BGC. Based on the BGC the correct dose of insulin can be administered.

If too much is administered = hypoglycaemia
Too little insulin administered = hyperglycaemia.

44
Q

How is type 2 diabetes controlled?

A

Regulate carbohydrate intake via dieting and matching this to their exercise levels, often increasing exercise.

Overweight people are told to lose weight.

In some cases this is not enough and drugs need to be used to control BGC, these can include drugs that stimulate insulin production, slow down the rate at which the body absorbs glucose from the intestine and even insulin injections.

45
Q

Advantages of producing insulin from GM bacteria over animals?

A

Human insulin is produced in a pure form - less likely to cause allergic reaction.

Insulin can be produced at higher quantities.

Production costs are cheaper.

Concerns over religious / ethics are overcome.

46
Q

How could stem cells be used to treat type 1 diabetes?

A

Type 1 diabetes stems from a loss of single cell type, and there’s evidence that a small no. Of islet cells can restore insulin production.

Totipotent stem cells can be used to produce these islet cells. These would often come from embryos which means that to obtain the stem cells the early embryo must be destroyed, although they are often destroyed anyway as they come from terminated pregnancies or spare from infertility treatments.

47
Q

What are the advantages of stem cells over other current therapies?

A

Donor availability would not be an issue- stem cells could produce an unlimited source of beta cells.

Reduces / eradicates the need for insulin injections

Reduced likelihood of rejection as embryonic stem cells are generally not rejected by the body. Stem cells can also be made by somatic cell nuclear transfer.

48
Q

Explain what happens when a threat is detected by the autonomic nervous system?

A

The hypothalamus communicates with the sympathetic nervous system and the adrenal-cortical nervous system. The sympathetic nervous system uses neuronal pathways to initiate body reactions whereas the adrenal-cortical system uses hormones in the blood stream.

The combined effect of these results in the fight or flight response.

49
Q

What does the sympathetic nervous system do in fight or flight response?

A

Sends out impulses to glands and smooth muscles and tells the adrenal medulla to release adrenaline and noradrenaline into the blood stream.
These stress hormones cause several changes to the body including Increased heart rate.

50
Q

Role of hypothalamus in fight or flight response?

A

Controls release of other stress hormones. Hypothalamus stimulates the pituitary gland to secrete hormones such as ACTH which travels in the blood to the adrenal cortex where it activates the release of many hormones that prepare the body to deal with a threat.

51
Q

Physiological responses to fight or flight?

A 
Heart rate increase
Pupils dilate 
Arterioles in skin constrict
BGC increases
Smooth muscle of airways relax
Non essential systems (digestion) shut down
Difficulty focusing on small tasks.
52
Q

Explain the function of adrenaline abs how it takes effect?

A

Adrenaline is hydrophilic so cannot pass through cell membranes- so it binds to receptor sites.

  1. Adrenaline binds to its receptor causing the enzyme Adenylyl Cyclase (present in cell membrane) to be activated.
  2. Adenylyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner cell membrane in the cytoplasm.
  3. The increase in cAMP levels activates specific enzymes called protein kinases which phosphorylate, and hence activate, other enzymes. In this instance, enzymes are activated which trigger the conversion of glycogen into glucose.
53
Q

Which nervous system is heart rate controlled by?

A

Involuntary = autonomic nervous system.

54
Q

What do the two centres within the medulla oblongata linked to the SAN do?

A

One centre increases heart rate by sending impulses through the sympathetic nervous system, these impulses are transmitted by the accelerator nerve.

One centre decreases heart rate by sending i pulsed through the parasympathetic nervous system, these impulses are transmitted by the vagus nerve.

55
Q

What are the 2 types of receptor which provide information that affects heart rate?

A

Baroreceptors

Chemoreceptors

56
Q

What are baroreceptors?

A

Pressure receptors. These receptors detect changes in blood pressure. Baroreceptors are present in the aorta, vena cava, and carotid arteries.

57
Q

What are chemoreceptors?

A

Chemical receptors. Detect changes in in the level of particular chemicals in the blood such as carbon dioxide. Chemoreceptors are located in the aorta, the carotid artery and the medulla.

58
Q

What happens if chemoreceptors detect an increase in carbon dioxide level in the blood?

A

If CO2 level in the blood increases, the pH decreases in the blood because carbonic acid is formed when CO2 reacts with water in the blood. Chemoreceptors detect decrease in pH in blood, a response is triggered to increase heart rate, which will mean that more CO2 will be exhaled as blood travels to the heart more quickly

59
Q

What happens when carbon dioxide levels in blood decrease?

A

Decrease in CO2 = increases in blood pH.
This change is detected by chemoreceptors in wall of carotid arteries and the aorta. This results in a reduction in the frequency of nerve impulses being sent to the medulla oblongata. In turn, this reduces the frequency of impulses being sent to the SAN via the sympathetic nervous system, and thus heart rate decreases back to normal levels.

60
Q

What happens if baroreceptors detect blood pressure is too high?

A

Impulses are sent to the medulla oblongata centre which decreases heart rate. The medulla oblongata sends impulses along parasympathetic neurones to the SAN which decreases the rate at which the heart beats. This reduces blood pressure back to normal.

61
Q

What happens if baroreceptors detects blood pressure is too low?

A

Impulses are sent to medulla oblongata centre which increases heart rate. The medulla oblongata sends impulses along sympathetic neurones to the SAN which increases the rate at which the heart beats. Blood pressure increases back to normal.

62
Q

What else can heart rate be impacted by other than neuronal communication?

A

Hormonal controls.
Heart rate is also influenced by the presence of hormones. In times of stress, adrenaline and noradrenaline are released, these affect the pacemaker region of the heart itself, they speed up heart rate by increasing the frequency of impulses produced by the SAN.

A Level Biology (22 decks)

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