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A Level Biology > Hormonal Communication > Flashcards

Hormonal Communication Flashcards

1
Q

What is the purpose of the endocrine system

A

Communication around the body
- Hormones travel round the circulatory system to target cells

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2
Q

2 types of hormone

A
  • protein/peptide hormone
    E.g. adrenaline, insulin, ADH
  • steroid hormone
    E.g. oestrogen, testosterone
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3
Q

Protein hormones

A

• not soluble through the phospholipid bilayer
• They bind to receptors on the cell surface membrane and release a second messenger inside the cell

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4
Q

Steroid hormones

A

• Steroid hormones can pass through the membrane, enter the cell and the nucleus
• They have a direct effect on the DNA in the nucleus.

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5
Q

When are hormones secreted

A

When the gland is stimulated
- this can be done by a change in concentration or stimulated by electrical impulses

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6
Q

2 types of gland

A

Endocrine and exocrine

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7
Q

Endocrine gland

A

Are a group of cells that release a hormone directly into the blood
E.g. thyroid, adrenal, pancreas, pituitary

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8
Q

Exocrine gland

A

Are a group of cells which surround a duct and secrete their hormones into this
E.g. salivary glands, liver (bile)

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9
Q

The pancreas contains endocrine glands and contains cells that produce digestive enzymes. Why are the cells that produce digestive enzymes described as exocrine?

A

Because digestive enzymes are released into ducts

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10
Q

Pathway from stimulus to respomse

A

Stimulus —> receptors —> hormone —> effectors —> response

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11
Q

First messengers

A

Non steroid hormones
- signalling molecules that bind to receptors (glycoproteins) on the cell surface membranes and initiate an effect
- usually cause the release of another signalling molecule (second messenger)

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12
Q

Second messenger

A

Stimulates a change in the activity of the cell

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13
Q

What is a G protein

A

Activated when the hormone binds to the receptor
- the G protein

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14
Q

Example: adrenaline

A
  1. Adrenaline is a first messenger.
  2. It binds to specific receptors on the plasma cell membrane of many cells e.g. hepatocytes
  3. When adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase.
  4. Activated adenylyl cyclase catalyses the production of a second messenger called cyclic AMP (cAMP) from ATP.
  5. cAMP activates a cascade eg: a cascade of enzyme reactions to make more glucose available to the cell by catalysing the breakdown of glycogen into glucose
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15
Q

Adrenaline

A
  • produced in medulla of adrenal gland
  • peptide hormone / non steroid hormone
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16
Q

Structure of adrenal gland

A

Cortex (broken into 2 sections)
Medulla
Blood vessels

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17
Q

Effects of adrenaline / noradrenaline

A
  • increase HR
  • increase blood flow
  • increase blood pressure
  • Glycogenolysis (glycogen broken down into glucose)
  • dilating of pupils
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18
Q

Aldosterone (mineralocorticoids)

A
  • produced in cortex (outermost layer)
  • steroid hormone
    Role:
  • sodium and potassium ions reabsorption in kidneys
  • control of blood pressure
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19
Q

Cortisol (glucocorticoids)

A
  • produced in cortex (middle layer)
  • steroid hormone
    Roles:
  • regulating metabolism of carbohydrates, fats and proteins
  • released in response to stress and as a result of low BGL
20
Q

How do steroid hormones work

A

• Passes through the cell surface membrane of the target cell.
• Binds with a receptor in the cytoplasm.
• The receptor-steroid hormone complex enters the nucleus of the target cells and binds to a receptor on the chromosomal material.
• This binding stimulates the production of mRNA which code for the production of proteins

21
Q

Androgens

A

Regulation of sexual characteristics and cell growth

22
Q

Pancreas

A
  • endocrine tissue in the pancreas is called islets of Langerhans
  • they are found in cluster around capillaries
  • made up of 2 types of cell: alpha cells and **beta cells*
23
Q

What do alpha cells secrete

A

GLUCAGON

24
Q

What do beta cells secrete

A

INSULIN

25
Q

What do ducts always have on a micrograph

A

White space around it

26
Q

What do electron micrographs of pancreas cells look like

A

Islets of Langerhans- largest circle, very pale pink/white

Ducts always have white space around it

Alpha cells are pink

Beta cells are purple

acini are also visible and are just pancreatic cells

27
Q

What is diabetes

A

A condition in which the homeostatic control of blood glucose has failed / deteriorated

28
Q

What happens to the kidneys when someone has diabetes

A
  • their insulin function is disrupted which allows the glucose concentration in the blood to rise
  • the kidneys are unable to filter out this excess glucose in the blood and so it often appears in the urine
  • the increased glucose conc also causes the kidneys to produce large quantities of urine, making the individual feel thirsty due to dehydratiom
29
Q

What are the 2 types of diabetes

A

Type I and Type II

30
Q

Type I diabetes

A
  • begins in childhood due to an autoimmune response where the body’s immune system (T cells) attacks the **beta cells* of the islets of Langerhans in the pancreas
  • the pancreas fails to produce sufficient insulin to control BGL
  • the lack of insulin also affects glycogen stores which results in an individual feeling fatigued
  • may experience a ‘hypo’- if BGC reaches a dangerously high level after a meal, organ damage can occur
31
Q

Type II diabetes

A
  • more common than type I
  • usually develops in this 40+
  • pancreas still produces insulin, but receptors have reduced in numbers or no longer respond to it. This reduced sensitivity to insulin occurs in the liver and fat storage tissues
  • lack of response to insulin means there is a reduced glucose uptake which leads to an uncontrolled high blood glucose concentration. This can cause the B cells to produce larger amounts of insulin which ultimately damages them
32
Q

Risk factors for type II diabetes

A
  • obesity
  • physical inactivity
  • high BP
  • high blood cholesterol
  • genetics
  • specific ethnic groups are more likely to develop the condition
33
Q

Diabetes and blood pressure

A
  • individuals with poorly controlled diabetes often suffer from high blood pressure
  • the high blood glucose concentration lowers WP of the blood which causes more water to move from the tissues into the blood vessels by osmosis
  • as a result, there is a larger volume of blood within the circulatory system which causes BP to increase
34
Q

Which of the following is not an endocrine gland or does not contain endocrine tissue:

A- gall bladder
B- ovaries
C- pancreas
D- pituitary

A

A- gall bladder

35
Q

3 ways glucose can enter the bloodstream

A
  1. Absorption in the gut following carbohydrate digestion
  2. Hydrolysis of glycogen stores
  3. Lipids/lactate and amino acids converted into glucose
36
Q

2 hormones which help regulate BGL

A

Insulin and glucagon

37
Q

What do alpha and beta cells act as

A

Receptors
- detect level of blood glucose
not receptors on cell surface membrane

38
Q

What happens when BGL are too low

A
  1. Alpha cells secrete glucagon, beta cells stop secreting insulin
  2. Glucagon binds to receptors in the cell surface membranes of liver cells
  3. This binding causes a conformational change in the receptor protein that activated a G protein
  4. This activated G protein activated the enzyme adenylyl cyclase
  5. Active adenylyl cyclase catalyses the conversion of ATP to cAMP (second messenger)
  6. cAMP binds to Protein Kinase A enzymes, activating them, leading to an enzyme cascade resulting in the breakdown of glycogen to glucose
39
Q

BGL too low (simplified)

A
  1. Glucagon binds to liver cells membrane receptors
  2. G protein is activated
  3. Adenylyl cyclase converts ATP to cAMP
  4. cAMP initiates enzyme cascade
40
Q

BGL too high

A
  1. High BGL detected by beta cells in the pancreas
  2. Glucose molecules enter B cells by facilitated diffusion
  3. Cells respire the glucose and produce ATP
  4. High concentration of ATP causes K+ channels in the B cells to close, causing a change in membrane potential
  5. Causes voltage gated Ca+ channels to open
  6. Increase in calcium ions causes B cells to secrete insulin
  7. Insulin containing vesicles move to cell surface membrane and release insulin into the capillaries by exocytosis
  8. Insulin (hormone) enters the blood stream and circulates around the body
  9. BGL returns to normal
41
Q

Action of insulin

A

Target cells: muscle cells, fat storage cells, adipose tissue and liver cells

  • They have glucose transporter proteins in their surface membranes
  • These membrane proteins allow for the uptake of glucose molecules via facilitated diffusion
  • The rate of glucose uptake for these cells is limited by the number of glucose transporter proteins present
  • Insulin binds to specific receptors on the membranes of target cells, which stimulates them to activate/add more glucose transporter proteins to their cell surface membrane which increases the permeability of the cells to glucose.
42
Q

Role of the liver

A
  • plays a vital role converting glycogen to glucose
  • both insulin and glucagon have specific receptors on the membranes of hepatocytes
43
Q

Insulin and glucagon result in different responses:

A

Glycogenesis synthesis of glycogen from glucose

Glycogenolysisthe breakdown of glycogen to glucose

Gluconeogenesis synthesis if glucose from non carbohydrate molecules

44
Q

What does insulin trigger

A

Glycogenesis
(Glycogen to glucose)

45
Q

What does glucagon trigger

A

Glycogenolysis
(Breakdown of glycogen to glucose)

Gluconeogenesis
(Synthesis of glucose from non-carbohydrate molecules)

46
Q

What is the function of acini

A

Secrete digestive enzymes

A Level Biology (26 decks)

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