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A level- Biology > Hormonal Communication > Flashcards

Hormonal Communication Flashcards

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1
Q

Define endocrine gland

A

Group of specialised cells which secrete hormones

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2
Q

Define exocrine gland

A

Group of specialised cells which secrete chemicals through ducts into organs or to the surface of the body

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3
Q

Define hormone

A

Chemical messengers which travel around the body in the bloodstream

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4
Q

Define target tissue

A

Specific cells that hormones act on to stimulate a response

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5
Q

List 8 endocrine glands, the hormone they secrete and the general role of each hormone.

A
  1. Pituitary gland (In brain)- growth hormone, anti-diuretic hormone and gonadotrophins (control development of ovaries and testes.
  2. Pineal gland (brain)- melatonin (affects reproductive development and daily cycles)
  3. Thyroid gland (neck)- thyroxine (controls rate of metabolism and rate that glucose is used up in respiration and promotes growth)
  4. Adrenal gland (above kidney)- adrenaline (increases heart and breathing rate and raises blood-sugar level)
  5. Testis- produces testosterone (controls sperm production and secondary sexual characteristics)
  6. Thymus (chest)- thymosin (promotes production and maturation of white blood cells)
  7. Pancreas (stomach area)- insulin (converts excess glucose into glycogen in the liver) and glucagon (converts glycogen back to glucose in the liver)
  8. Ovary- oestrogen (controls ovulation and secondary sexual characteristics),and progesterone, (which controls ovulation and secondary sexual characteristics and prepares the uterus lining for receiving an embryo)
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6
Q

Describe how hormonal communication occurs.

A
  1. Hormones are secretes into the blood when a gland is stimulated.
  2. Once secreted, the hormones are transported in the blood plasma all over the body.
  3. The hormones diffuse out of the blood and bind to specific receptors for the hormone, found on the membranes, or in the cytoplasm of cells in the target organs.- target cells
  4. Once bound to their receptors the hormones stimulate the target cells to produce a response
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7
Q

State the location of the adrenal glands in the body and describe their structure.

A
  1. Two small glands that are located on top of each kidney and are made up of two distinct parts surrounded by a capsule.
  2. The adrenal cortex- the outer region of the glands, produces hormones vital to life e.g. cortisol and aldosterone
  3. The adrenal medulla- the inner region of the glands. This produces non-essential hormones, such as adrenaline which helps the body react to stress.
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8
Q

Describe the role of the adrenal cortex and the hormones produced by it.

A 
Production of hormones by adrenal cortex is controlled by hormones released from the pituitary gland in the brain. 
3 main types of hormones:
1. Glucocorticoids
2. Mineralocorticoids
3.Androgens
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9
Q

Describe the function of glucocorticoids

A

The release of these hormones from the adrenal cortex is controlled by the hypothalamus

  1. Include cortisol which helps regulate metabolism by controlling how the body converts fats, proteins, and carbs to energy.
  2. It also helps regulate blood pressure and cardiovascular function in response to stress
  3. Another glucocorticoid hormone released is corticosterone. This works with cortisol to regulate the immune response and suppress inflammatory reactions
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10
Q

Describe the function of mineralocorticoids

A

Release from adrenal cortex is mediated by signals triggered by the kidney
1. Main one is aldosterone- helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids.

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11
Q

Describe the function of androgens

A
  1. Small amounts of male and female sex hormones are released
  2. Small impact compared to main sex hormones but still important
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12
Q

Describe the role of the adrenal medulla and the functions of the hormones produced.

A

Released when the sympathetic nervous system is stimulated. This occurs when the body is stressed
Two hormones secreted by medulla:
1. Adrenaline
2. Noradrenaline

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13
Q

Describe the function of adrenaline

A
  1. This increases the heart rate sending blood quickly to the muscles and brain.
  2. It also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
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14
Q

Describe the function of noradrenaline

A
  1. Works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils, widening of air passages and the narrowing of blood vessels in non-essential organs
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15
Q

Define histology

A

The study of the microscopic structure of tissues.

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16
Q

Describe the roles of the pancreas.

A

Two main functions:

  1. Exocrine gland- to produce enzymes and release them via a duct into the duodenum
  2. Endocrine gland- to produce hormones and release them into the blood
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17
Q

What is the role of the pancreas as an exocrine gland

A
  1. Most of pancreas is made up of exocrine glandular tissue
  2. This tissue is responsible for producing digestive enzymes and an alkaline fluid known as pancreatic juice.
  3. The enzymes and juice are secreted into ducts which eventually lead to the pancreatic duct.
  4. From here they are released into the duodenum, the top part of the small intestines.
  5. The pancreas produces three important types of digestive enzymes: amylases, protesases and lipases
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18
Q

Describe the role of the pancreas as an endocrine gland

A
  1. Responsible for producing insulin and glucagon- essential role in controlling blood glucose concentration.
  2. Within the exocrine tissue there are small regions of endocrine Islets of Langerhans.
  3. The cells of the islets of Langerhans are responsible for producing insulin and glucagon, and secreting these hormones directly into the bloodstream
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19
Q

Draw a diagram of a pancreas section, label it and annotate with the functions of the structures labelled.

A
  1. Islets of langerhans-
    a) lightly stained
    b) large and sperical clusters
    c) endocrine pancreas
    d) produce and secrete hormones
  2. Pancreatic acini
    a) darker stained
    b) small, berry-like clusters
    c) exocrine pancreas
    d) produce and secrete digestive enzymes
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20
Q

Identify the components of the pancreas in a photomicrograph of a stained section.

A

p387

  1. Dark pink surroundings is the pancreatic acini
  2. Light pink big circle in the middle of pancreatic acini is the islet of Langerhan
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21
Q

Define α-cell

A
  1. Present in the islet of Langerhan
  2. They produce and secrete glucagon
  3. stained pink
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22
Q

Define β-cell

A
  1. Present in the islet of Langerhan
  2. They produce and secrete insulin
  3. stained blue
23
Q

Define Islet of Langerhans

A

Specialised cells within the pancreas responsible for producing insulin and glucagon

24
Q

Define acinus

A

A small sac-like cavity in a gland, surrounded by secretory cells

25
Q

Define tubule/central duct/pancreatic duct

A
  1. Exit way for enzymes produced by the acini into the small intestine
  2. A tube leading from the pancreas to the duodenum
26
Q

Define insulin

A
  1. A globular protein hormone involved in the regulation of blood glucose concentration
27
Q

Define glucagon

A
  1. A hormone formed in the pancreas which promotes the breakdown of glycogen to glucose in the liver.
28
Q

Describe and explain how the ultrastructure of the α- and β-cells in the islets of Langerhans is specialised to manufacture and secrete hormones.

A

frr

29
Q

State the “normal” blood glucose concentration.

A

90mg cm-3

30
Q

Name the two hormones involved in regulating blood glucose concentration

A
  1. Insulin

2. Glucagon

31
Q

State the condition in which insulin is released and from which cells, and describe how insulin has its effect on cells.

A
  1. Produce by the β-cells of the islets of Langerhans in the pancreas
  2. If blood glucose concentration is too high β-cell detect this rise in blood glucose concentration and respond by secreting insulin directly into the blood stream
  3. Virtually all body cells have insulin receptors on their cell surface membrane (except rbc)
  4. When insulin binds to its glycoprotein receptor, it causes a change in the tertiary structure of the glucose transport protein channels.
  5. This causes the channels to open allowing more glucose to enter the cell.
  6. Insulin also activates enzymes within some cells to convert glucose to glycogen and fat
32
Q

State the effects insulin has on cells.

A

Lowers blood glucose concentration by:

  1. Increasing the rate of absorption of glucose by cells, in particular skeletal muscle cells
  2. Increasing the respiratory rate of cells- this increases their need for glucose and causes a higher uptake of glucose from the blood
  3. Increasing the rate of glycogenesis- insulin stimulates the liver to remove glucose from the blood by turning the glucose into glycogen and storing it in the liver and muscle cells
  4. Increasing the rate of glucose to fat conversion
  5. Inhibiting the release of glucagon from the α-cells of the islets of Langerhans
33
Q

Define glycogenesis

A
  1. Production of glycogen from glucose- decreases blood-sugar concentration
34
Q

Define glycogenolysis

A
  1. Process in which glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream
35
Q

Define gluconeogenesis

A
  1. Production of glucose from non-carbohydrate sources which is released into the blood stream
36
Q

Describe 3 other factors that affect blood glucose concentration.

A
  1. Respiration- some of the glucose in blood is used by cells to release energy. This is required to perform normal body functions.
  2. Diet- When you eat carbohydrate-rich foods such as pasta and rice etc, the carbohydrates the contain are broken down in the digestive system to release glucose
  3. Stress- increases blood-sugar levels
37
Q

Explain why insulin must be constantly secreted in order to maintain its effect

A
  1. Insulin is broken down by enzymes in the cells of the liver.
  2. Therefore to maintain its effect it has to be constantly secreted
38
Q

Explain why it is important that insulin is constantly being broken down by enzymes

A
  1. As your blood-glucose concentration returns to the normal, you do not want to maintain a higher level of glycogenesis
  2. So it needs to be constantly broken down to ensure you don’t have too low a blood-glucose concentration
39
Q

State the condition in which glucagon is released and from which cells, and describe how glucagon has its effect on cells.

A
  1. Produced by the α-cells of the islets of Langerhans in the pancreas
  2. If blood glucose concentration is too the low, the α-cells detect this fall in blood glucose concentration and respond by secreting glucagon directly into the bloodstream
  3. Only cells in the body which have glucagon receptors are the liver cells and fat cells - theses are the only cells that can respond
  4. As blood-glucose returns to normal, this is detected by α-cells, when it rises above a set level, the α-cells reduce their secretion of glucagon- negative feedback
40
Q

State the effect glucagon has on cells.

A
  1. Glycogenolysis- the liver breaks down its glycogen store into glucose and releases it backs into bloodstream
  2. Reducing the amount of glucose absorbed by the liver cells
  3. Increasing gluconeogenesis- increasing the conversion of amino acids and glycerol into glucose in the liver
41
Q

Draw a flow chart showing the negative feedback system that controls blood sugar level.

A
  1. Insulin and glucagon are antagonistic hormones, that is, they work against each other
  2. The system of maintaining blood glucose concentration is said to be self-regulating, as it is the level of glucose in the blood that determines the quantity of insulin and glucagon that is released.
  3. Blood glucose concentration is not constant, but fluctuates around a set point as the result of negative feedback.
  4. In times of stress adrenaline is released by the body, which raises the blood glucose concentration to allow more respiration to occur
42
Q

Describe how insulin is secreted by beta cells in response to a high blood glucose concentration.

A
  1. At normal blood glucose concentration levels, potassium channels in the plasma membrane of β cells are open and potassium ions diffuses out of the cell.
  2. When blood glucose concentration rises, glucose enters the cell by a glucose transporter.
  3. The glucose is metabolised inside the mitochondria, resulting in the production of ATP
  4. The ATP binds to potassium channels and causes them to close. They are known as ATP-sensitive potassium channel.
  5. As potassium ions can no longer diffuse out of the cell, the potential difference reduces and depolarisation occurs.
  6. Depolarisation causes the voltage-gated calcium channels to open
  7. Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis
43
Q

Define diabetes mellitus

A
  1. Medical condition which affects a person’s ability to control their blood-glucose concentration
44
Q

Define Type 1 diabetes

A
  1. Patients with type 1 diabetes are unable to produce insulin.
  2. The β-cells in the islets of Langerhans do not produce insulin.
  3. The cause of type 1 diabetes is not known, so at the moment, the disease cannot be prevented or cured, but it is possible to treat the symptoms
  4. Evidence suggests that it arises as a result of an autoimmune response where the body’s own immune system attacks the β-cells.
45
Q

Define type 2 diabetes

A
  1. Patients with type 2 diabetes cannot effectively use insulin and control their blood-sugar levels.
  2. This is either because the person’s β cells do not produce enough insulin or the person’s body cells do not respond properly to insulin
  3. This is often because the glycoprotein insulin receptor on the cell membrane does not work properly
  4. The cells lose their responsiveness to insulin and therefore do not take up enough glucose leaving it in the bloodstream.
46
Q

Define hyperglycaemia

A

An excess of glucose in the bloodstream, it is a common effect of uncontrolled diabetes.

47
Q

Define hypoglycaemia

A

Deficiency of glucose in the bloodstream

48
Q

How is type 1 diabetes treated

A
  1. Type 1 diabetes is controlled by regular injections of insulin and is therefore said to be insulin dependent
  2. People regularly test their blood glucose concentration.
  3. Based on the concentration the person can work out the dose of insulin they need to inject.
  4. The insulin administered increases the amount of glucose absorbed by cells and causes glycogenesis to occur resulting in a reduction of blood glucose concentration.
  5. Too little or too much results in hyper/hypoglycaemia
49
Q

How is type 2 diabetes treated

A
  1. Regulate persons carbohydrate intake through their diet and matching this to their exercise
  2. Some cases this is not enough so drugs also have to be used.
  3. These drugs can be ones that stimulate insulin production, drugs that slow down the rate at which the body absorbs glucose from the intestine and ultimately even insulin injections
50
Q

List 4 benefits of using insulin produced from genetically engineered bacteria rather than from pigs to treat diabetes. For each benefit explain why the benefit exists.

A
  1. Human insulin is produced in a pure form- means it is less likely to cause allergic reactions
  2. Insulin can be produced in much higher quantities
  3. Production costs are must cheaper
  4. People’s concern over using animal products in humans, which may be religious or ethical, are overcome
51
Q

Describe how stem cells could be used to treat diabetes

A
  1. Diabetes researchers have been searching for ways to replace the faulty β cells in the pancreatic islets of diabetic sufferers
  2. As type 1 diabetes results from the loss of a single cell type and there is evidence that a relatively small number of islet cells can restore the insulin production,
  3. It is likely that the stem cells used in diabetes would be taken from embryos.
  4. Totipotent stem cells have the potential stem cells have the potential to grow into any body’s cell types.
52
Q

Describe the potential benefits of stem cell treatment for Type 1 diabetes over insulin injection or whole pancreas transplantation.

A
  1. Donor availability would not be an issue- stem cells could produce an unlimited source of new β cells
  2. Reduced likelihood of rejection problems as embryonic stem cells are generally not rejected by the body. Stem cells can also e made by somatic cell nuclear transfer.
  3. People no longer have to inject themselves with insulin
53
Q

Describe one risk of using stem cells to treat Type 1 diabetes.

A
  1. Slight risk of rejection
  2. Risk that stem cells transplanted into the body might induce the formation of tumours as a result of unlimited cell growth.
54
Q

Explain why stem cell treatment is not likely to be suitable for treating Type 2 diabetes.

A
  1. All body cells faulty in type 2, not possible to replace all.
  2. In type 1 it is only one type of cell so it may be possible to replace that cell type using stem cells that are programmed to differentiate into the β cells in the pancreas.

A level- Biology (46 decks)

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