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Biology > 14 - Hormonal communications > Flashcards

14 - Hormonal communications Flashcards

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1
Q

what is the endocrine system?

A
  • it is made up of endocrine glands
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2
Q

what are endocrine glands?

A
  • a group of specilised cells that secrete chemicals (hormones)
  • they are secreted into the blood stream
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3
Q

what are exocrine glands?

A

secrete chemicals through ducts into organs or the surface of the body, e.g. sweat gland, sebaceous gland, glands in digestive system. ​

Some glands have endocrine & exocrine functions.​

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4
Q

Growth hormone
where is it produced, what is its function?

A

Pituitary gland
Stimulates the growth of muscles and long bones.

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5
Q

ADH
where is it produced, what is its function?

A

Pituitary gland
Stimulates reabsorption of water from kidney tubules.

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6
Q

Gonadotrophins
where is it produced, what is its function?

A

Pituitary gland
Controls development of ovaries and testes

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7
Q

Melatonin
where is it produced, what is its function?

A

Pineal gland
Reproductive cycles and circadian rhythms (and sleep)​

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8
Q

Thyroxine
where is it produced, what is its function?

A

Thyroid gland
Influences the rate of metabolism, growth and development of young animals.

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9
Q

Thymosin
where is it produced, what is its function?

A

Thymus
Promotes production and maturation of WBCs

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10
Q

Insulin/glucagon
where is it produced, what is its function?

A

Pancreas
Controls blood glucose levels

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11
Q

Adrenaline
where is it produced, what is its function?

A

Adrenal gland
Increases HR, BR and raises blood glucose levels

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12
Q

Progesterone
where is it produced, what is its function?

A

Ovary
Prepares the uterus lining for receiving an embryo

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13
Q

Oestrogen
where is it produced, what is its function?

A

Ovary
Development of female 2o sexual characteristics, ovulation

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14
Q

Testosterone
where is it produced, what is its function?

A

Testes
Development of male 2o sexual characteristics, sperm production

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15
Q

What is a hormone?

A

A hormone is a chemical made by an endocrine gland that travels in the blood to the target cells.

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16
Q

2 types of pathway, according to the distance the signal travels​ are:

A

Paracrine signalling
Endocrine signalling

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17
Q

Endocrine signalling

A

involves signalling over long distances and signalling molecules are carried in blood (hormones) ​

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18
Q

Paracrine signalling

A

occurs between cells close together e.g. neurotransmitters, histamine produced by white blood cells

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19
Q

hormones in cell signalling

A

Hormones must be detected by receptor molecules.​

These are proteins or glycoproteins on or in cell surface membrane.​

Some receptors are found in cytoplasm because some hormones can diffuse through phospholipid bilayer.​

Hormone binding to the receptor causes specific effect in the target cell (organ).

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20
Q

2 types of hormone:

A

Non-Steroid hormones​
Steroid hormones

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21
Q

Steroid hormones

A

A steroid hormone is lipid-soluble so can diffuse through cell surface membrane. ​

It binds to receptor to form hormone-receptor complex. This can move into the nucleus and act as a transcription factor to switch genes on or off.​

Oestrogen works in this way.​

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22
Q

Non-Steroid hormones

A

Not soluble in the phospholipid membrane (as they are hydrophilic) so do not enter the cell (‘first messengers’). ​

They bind to the receptors on the cell surface membrane and trigger the release of a ‘second messenger’ inside the cell.​

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23
Q

describe the features of the adrenal glands

A

Each gland is divided into the outer adrenal cortex…​

…and the inner adrenal medulla.​

Both regions are well supplied with blood vessels and produce hormones which are directly secreted into the blood.​

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24
Q

what controls the production of hormones in the adrenal cortex

A

controlled by hormones released from pituitary glands in the brain​

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25
Q

Hormones released from the adrenal cortex​:

A

Glucocorticoids
mineralocorticoids
Androgens

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26
Q

what are examples of glucocorticoids
- How is their release controlled?

A

Cortisol
Corticosterone
-release of these hormones is controlled by the hypothalamus​

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27
Q

what is an example of mineralocorticoids
- how is their release controlled

A

Aldosterone
-​release is mediated by signals triggered by kidney​

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28
Q

What is cortisol?
what group is it?
Where is it released?
how is its release controlled?

A

Involved in regulation of metabolism . Helps regulate blood pressure and cardiovascular function in response to stress

Glucocorticoid

adrenal cortex​

release of these hormones is controlled by the hypothalamus

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29
Q

What is Corticosterone?
what group is it?
Where is it released?
how is its release controlled?

A

Works with cortisol to regulate immune response and suppress inflammatory reactions

Glucocorticoids​

adrenal cortex
​
release of these hormones is controlled by the hypothalamus

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30
Q

What is Aldosterone?
what group is it?
Where is it released?
how is its release controlled?

A

Helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids

Mineralocorticoids​

adrenal cortex

release is mediated by signals triggered by kidney

31
Q

what are androgens

A

Androgens are produced in small amounts and can be converted elsewhere in the body to female hormones (oestrogens) and male hormones (other androgens)

32
Q

what controls the production of hormones in the adrenal medulla

A

Hormones are released when the adrenal medulla is stimulated by the autonomic sympathetic nervous system (ACh released as the NT). ​

This occurs when the body is stressed.

33
Q

what hormones are released adrenal medulla?

A

Adrenaline
Noradrenaline

34
Q

what is adrenaline
where is it released from

A

This increases the heart rate by sending blood quickly to the muscles and brain. It also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver​ (glycogenolysis)

adrenal medulla

35
Q

what is noradrenaline
where is it released from

A

This hormone 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 narrowing of blood vessels in non-essential organs

adrenal medulla

36
Q

explain the pancreas as an exocrine gland

A

Composed largely of exocrine glandular tissue​

Produces alkaline pancreatic juice which contains digestive enzymes and is secreted into duodenum via the pancreatic duct​

Exocrine cells that produce enzymes are called acinar cells, clustered in groups called acini​

Ductal cells lining the pancreatic ducts produce bicarbonate that makes the pancreatic juice alkaline

37
Q

explain the pancreas as an endocrine gland

A

Small regions of endocrine tissue called islets of Langerhans​

Produce the hormones insulin and glucagon which are secreted directly into the bloodstream ​

Alpha cells secrete glucagon​

Beta cells secrete insulin

38
Q

Pancreatic Juices

A

Fluid containing enzymes that is produced by most cells in the pancreas and carried to the small intestine.

39
Q

Trypsinogen​

A

. An inactive protease enzyme produced by the pancreas that’s converted to its active form when it enters small intestine.

40
Q

Acini​

A

A small group of exocrine cells in the pancreas

41
Q

Pancreatic Duct

A

carries the pancreatic juices to the duodeneum (small intestine) from the pancreas.​

42
Q

Islets of langerhans​

A

Areas of alpha and beta cells in the pancreas

43
Q

Beta Cells​

A

Found in the islets of Langerhans and produce insulin to lower blood glucose levels

44
Q

Alpha Cells​

A

. Produce Glucagon to increase blood glucose levels

45
Q

Glycogenesis​

A

The production of glycogen

46
Q

glucose too high

A

e.g. after dinner?​

​

… detected by alpha cells which reduce secretion of glucagon​

​

…Detected by beta cells which secrete insulin into the blood.​

​

…Insulin targets hepatocytes, muscle cells & other cells, inc. some in brain.

47
Q

glucose Too low? (below 4 mmol dm-3)​

A

RESPIRATION !​

Perhaps when you haven’t eaten for a number of hours or you’ve just done some exercise!​

​Alpha cells secrete glucagon into the blood

Detected by beta cells which STOP insulin secretion​

Glucagon targets hepatocytes and fat cells ONLY, which, again, have specific receptors

48
Q

Let’s look at the action of insulin in more detail:​

A
  1. Insulin secreted from beta cells and binds to glycoprotein receptors on target cells
  2. Activated insulin receptor initiates signalling cascade via second messengers which causes a change of glucose transport protein channels, causing them to OPEN
  3. Glucose enters cell and enzymes (also activated by the signaling cascade downstream of the insulin receptor) are activated to convert the glucose to glycogen (glycogenesis, 4) and fat (6).
49
Q

what does insulin result in

A

This all results in the following:​

  • increases rate of absorption of glucose (esp skeletal muscle cells)​
  • Increases respiratory rate of cells​
  • increases rate of glycogenesis (glucose to glycogen)​
  • Increases rate of conversion of glucose -> fat​
  • also inhibits the release of glucagon from a cells of the islets of Langerhans​
50
Q

How does glucagon work to raise blood glucose?

A
  1. Glucagon binds to receptor on the target cell membrane.
  2. Activated G-protein dissociates and triggers intracellular signaling cascades via cAMP
  3. Ultimately glycogen is converted to glucose (glycogenolysis)
  4. Amino acids and fats converted to glucose (gluconeogenesis)
51
Q

Release of insulin from beta cells​

A

1) Normally K+ channels in plasma membrane are open allowing K+ ions to diffuse out

Normally Ca+ channels in plasma membrane are closed.
=more negative inside the cell -70mV

2) If glucose levels are high, glucose moves into the cell through a glucose transporter

3) The glucose is metabolized to produce ATP ​(enzyme = glucokinase)

4) The ATP causes ATP-sensitive potassium channels to close

5) The build up of K+ ions alters the potential difference across the membrane (becomes less negative, approx -30mv)

6) Change in potential difference causes voltage-gated calcium ion channels to open

7) Calcium ions cause vesicles of insulin to fuse with membrane = insulin released by exocytosis

52
Q

Hyperglycaemia​

A

High blood glucose levels (enough to cause adverse effects)​

53
Q

Hypoglycaemia ​

A

Low blood glucose levels (enough to cause adverse effects)​

54
Q

Diabetes Mellitus​

A

a chronic disease where the body cannot effectively control blood glucose levels​

55
Q

Type 1 diabetes

A

Beta cells do not produce insulin​

Often caused by an autoimmune response ​

Usually develops during childhood​

typically managed with a combination of dietary changes, blood glucose monitoring, & insulin injections.​

Sometimes treated with panaceas transplants or beta cell injections.​

  • donors are limited and immunosuppressant drugs must be used​
  • But this does usually cure the diabetes
56
Q

Type 2 diabetes​

A

Beta cells do not produce enough insulin, or body cells do not respond to insulin.​

Caused by obesity, inactivity, excessive intake of carbohydrates.​

Variety of factors including the generally elevated levels of blood insulin desensitises cells to insulin. Glycoprotein insulin receptors stop working.​

Generally occurs in older people but can happen at any age​

Management involves reduction of carbohydrate consumption, increasing exercise, losing weight.​

Some drugs can be used to stimulate insulin production or reduce absorption of glucose in the gut. Insulin injections are sometimes used but this is much less common than in type 1.

57
Q

Symptoms of diabetes

A

The inability to control blood glucose levels can result in extended periods of Hyperglycaemia that can be fatal.​

If the body does not produce insulin, glucagon levels rise, triggering glycogenolysis in the liver, further raising blood glucose.​

This causes excessive urination, resulting in a loss of glucose, minerals & water.​

Other symptoms include:​

  • Dehydration​
  • Tachycardia​
  • Hyperventilation​
  • Hypotension​
  • Thirst​
  • Excessive urination​
  • Vomiting​
  • Abdominal pain​
  • Loss of consciousness
58
Q

Diabetic ketoacidosis

A

The lack of insulin also causes fat cells to switch to metabolising fatty acids for respiration.​

This results in the excessive production of ketone bodies which acidify the blood.​

59
Q

Flight or fight response​ overview

A

Autonomic nervous system detects a threat.​

Hypothalamus communicates with the sympathetic nervous system & adrenal-cortical system.​

Sympathetic nervous system directly acts on smooth muscles & glands as well as stimulating the adrenal medulla.​

Activation of adrenal-cortical system also causes release of ≈30 hormones by the adrenal cortex.​

  • CRF = corticotropin-releasing factor​
  • ACTH = Adrenocorticotropic hormon
60
Q

Action of adrenaline​

A

Triggers liver cells to undergo glycogenolysis so glucose is released into the bloodstream. This allows respiration to increase so more energy is available for muscle contraction

61
Q

what is the SAN linked to

A

medulla oblongata

62
Q

receptors in blood vessels. The stimuli that they detect are:​

A

blood pressure​

carbon dioxide concentration of blood​

pH of blood

63
Q

Chemoreceptors

A

detects changes in blood pH​

​

Located in the aorta & carotid arteries (neck), and medulla oblongata.​

Send information to cardiac regulatory centre about concentration of CO2

Increase in acidity => increase in HR

64
Q

Baroreceptors

A

in the walls of the aorta, vena cava and carotid arteries​

​

Detect increase in blood flow and blood pressure ​

​

Stretch receptors are stimulated ​

​

Send nerve impulses along sensory neurones to cardioregulatory centre in the medulla oblongata

65
Q

if BP too high …

A

the cardio inhibitory centre sends nerve impulses along the parasympathetic neurones (the vagus nerve) to the SAN to decrease heart rate.

66
Q

if BP too low

A

the cardio acceleratory centre sends nerve impulses along the sympathetic neurones to the SAN to increase heart rate.

67
Q

control of heart rate​- decrease

A

Nervous (autonomic) control

Parasympathetic neurone secretes acetylcholine at the SAN synapse. ​

Acetylcholine binds to receptors in the SAN which reduces the rate of impulses sent from the SAN to the heart muscle so heart rate decreases.​

68
Q

control of heart rate​- increase

A

Sympathetic neurone secretes noradrenaline at the SAN synapse.​

Noradrenaline binds to receptors in the SAN which increases the rate of impulses sent from the SAN to the heart muscle so heart rate increases.

69
Q

Define homeostasis​

A

Maintaining a stable internal environment around a set point, within a narrow range.​

70
Q

What variables are maintained by homeostasis?​

A

Blood glucose, Blood pH, Body temperature, Water balance, Sodium/potassium ions.​

71
Q

What is a negative feedback system? (provide an example)​

A

Negative feedback systems work to reverse the initial stimulus. When used in homeostasis there will be two responses that work antagonistically, i.e. one that increases and one that decreases. These work to maintain the desired conditions. E.g. blood glucose control using insulin & glucagon.​

72
Q

What is a positive feedback system? (provide an example)​

A

Positive feedback systems work to reinforce the initial stimulus. A stimulus triggers a response which increases the stimulus which increases the response etc. etc. ​

73
Q

Endotherms​

A

Control their body temperature within strict limits​

Use a variety of mechanisms to control body temperature independent of external temperature

74
Q

Ectotherms

A

Are NOT able to control body temperature​

Rely on external sources of heat and Body temperature fluctuates with external temperature​

May use behavioural mechanisms to control body temperature

Biology (24 decks)

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