5.1.4 - Hormonal Communication

Question 1

Endocrine system

Answer 1

Works alongside neuronal system to react to changes ; uses hormones to send information about changes in the environment around the body to bring about a designated response

Question 2

Endocrine glands

Answer 2

Make up the endocrine system ; group of cells which are specialised to secrete chemicals ; they are known as hormones and are secreted directly into the bloodstream (pancreas and adrenal glands for example)

Question 3

Pituitary gland?

Answer 3

Makes several hormones which in turn control the release of other hormones ; close proximity to the hypothalamus ensures that the nervous and hormonal responses of the body are closely linked and coordinated

Question 4

Pineal gland

Answer 4

Produces melatonin which affects reproductive development and daily cycles

Question 5

Thymus

Answer 5

Produces thymosin which promotes production and maturation of white blood cells

Question 6

Pancreas

Answer 6

Produces insulin which converts excess glucose into glycogen in the liver ; and glucagon, which converts glycogen back to glucose in the liver

Question 7

Ovary

Answer 7

Produces oestrogen which controls ovulation and secondary sexual characteristics
Progesterone prepares the uterus lining for receiving an embryo

Question 8

Testis

Answer 8

Produces testosterone which controls sperm production and secondary sexual characteristics

Question 9

Adrenal gland

Answer 9

Produces adrenaline which increases heart and breathing rate and raises blood sugar level

Question 10

Thyroid gland

Answer 10

Produces thyroxine which controls rate of metabolism and rate that glucose is used up in respiration and promotes growth

Question 11

Pituitary gland

Answer 11

Produces growth hormones which control growth of bones and muscles ; ADH (which increases water reabsorption in kidneys) and gonadotrophins which control development of ovaries and testes

Question 12

Exocrine glands difference

Answer 12

Secrete chemicals through ducts into organs or to the surface of the body

Question 13

Hormones?

Answer 13

They are chemical messengers because they carry information from one part of the body to another ; they can be steroids, proteins, glycoproteins, polypeptides, amines or tyrosine derivatives

Question 14

How are hormones secreted directly into the blood?

Answer 14

When a gland is stimulated ; this can occur as a result of a change in concentration of a particular substance such as blood glucose concentration or a nerve impulse/another hormone

Question 15

Once secreted…?

Answer 15

Hormones are transported in the blood plasma all over the body ; they diffuse out of the blood and bind to specific receptors for that hormone found on the membranes or in the cytoplasm of cells in the target organs - these are known as target cells

Question 16

What happens once bound to target cells?

Answer 16

Hormones stimulate the target cells to produce a response

Question 17

Why does the type of hormone matter?

Answer 17

It determines the way it causes it’s effect on a target cell ; steroid and non-steroid hormones

Question 18

Steroid hormones

Answer 18

Lipid soluble ; pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex ; the receptors may be in the cytoplasm or the nucleus depending on the hormone
Hormone receptor complex formed acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene - oestrogen is an example

Question 19

Non-steroid hormones

Answer 19

Hydrophilic so cannot pass directly through the cell membrane ; they bind to specific receptors on the cell surface membrane of the target cell - triggers a cascade reaction mediated by chemicals called second messengers (adrenaline is a non-steroid hormone)

Question 20

Hormones vs neuronal

Answer 20

Hormones are not released directly into their target cells - slower/less specific form of communication than neuronal communication
Hormones are not broken down as quickly as neurotransmitters so they can result in a much longer and widespread effect

Question 21

Hormone vs nervous communication

Answer 21

Communication is by chemicals called hormones and nervous is by nerve impulses

Question 22

Hormonal vs nervous transmission

Answer 22

Blood system vs neurones

Question 23

Speed of transmission hormonal vs nervous

Answer 23

Relatively slow vs very rapid

Question 24

Travelling around the body - hormonal vs nervous

Answer 24

Hormones travel to all parts of the body but only target organs respond
Nerve impulses travel to specific parts of the body

Question 25

Area of response? Hormonal vs nervous?

Answer 25

Widespread vs localised

Question 26

Length of response? Hormonal vs neuronal?

Answer 26

Long-lasting vs short lived

Question 27

Effect - hormonal vs neuronal?

Answer 27

Permanent and irreversible / temporary and reversible

Question 28

Adrenal glands

Answer 28

Located on top of each kidney and are made up of two distinct parts surrounded by a capsule

Question 29

Adrenal cortex?

Answer 29

Outer regions of the glands ; produces hormones that are vital to life (like cortisol and aldosterone)

Question 30

Adrenal medulla?

Answer 30

Inner regions of the glands ; produces non-essential hormones like adrenaline which help the body react to stress

Question 31

3 main types of hormones produced by the adrenal cortex?

Answer 31

Glucocorticoids Mineralocorticoids Androgens

Question 32

Glucocorticoids?

Answer 32

These include cortisol which help regulate metabolism by controlling how the body converts fats, proteins and carbohydrates to energy. It also helps regulate blood pressure and cardiovascular function in response to stress. Corticosterone is another glucocorticoid which works with cortisol to regulate immune response and suppress inflammatory reactions - this is controlled by the hypothalamus

Question 33

Mineralocorticoids

Answer 33

Main one produced is aldosterone which helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids ; release is mediated by signals triggered by the kidney

Question 34

Androgens

Answer 34

Small amounts of male and female sex hormones are released ; their impact is relatively small compared with the larger amounts of hormones (oestrogen and testosterone) released by the ovaries or testes after puberty - very important in women after menopause

Question 35

Adrenal medulla?

Answer 35

Hormones here are released when the sympathetic nervous system is stimulated - this occurs when the body is stressed

Question 36

Hormones secreted by the adrenal medulla?

Answer 36

Adrenaline Noradrenaline

Question 37

Adrenaline?

Answer 37

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

Question 38

Noradrenaline

Answer 38

Hormone works with adrenaline in response to stress by producing effects such as increased heart rate, widening of the pupils, widening of air passages in the lungs and the narrowing of blood vessels in non-essential organs (leading to increased blood pressure)

Question 39

Where is the pancreas found?

Answer 39

Upper abdomen - behind the stomach ; a glandular organ which plays a big role in producing and secreting hormones and digestive enzymes Controls blood glucose concentration and digestion

Question 40

Functions of the pancreas

Answer 40

Exocrine gland - produces enzymes and releases them via a duct into the duodenum Endocrine gland - produce hormones and release them into the blood

Question 41

Role as an exocrine gland?

Answer 41

Most of the pancreas is made up of exocrine glandular tissue ; this is responsible for producing digestive enzymes and an alkaline fluid known as pancreatic juice - they are secreted into ducts which eventually lead to the pancreatic duct and from there they are released into the duodenum (the top part of the small intestine)

Question 42

Pancreas produces 3 types of important digestive enzymes

Answer 42

Amylases - break down starch into simple sugars (pancreatic amylase) Proteases - break down proteins into amino acids (trypsin) Lipases - break down lipids into fatty acids and glycerol (pancreatic lipase)

Question 43

Role as an endocrine gland

Answer 43

Responsible for producing insulin and glucagon - within the exocrine tissue there are small regions of endocrine tissue called Islets of Langerhans ; these cells are responsible for producing insulin and glucagon and secreting these hormones directly into the bloodstream

Question 44

Histology of the pancreas - appearance

Answer 44

Islets of Langerhans ; lightly stained Pancreatic acini ; darker stained

Question 45

Histology of the pancreas - shape

Answer 45

Islets : large, spherical clusters Pancreatic acini : small, berry-like clusters

Question 46

Histology of the pancreas - type of tissue

Answer 46

Islets of Langerhans - endocrine pancreas Pancreatic acini - exocrine pancreas

Question 47

Histology of the pancreas - function

Answer 47

Islets of Langerhans : produce and secrete hormones Pancreatic acini : produce and secrete digestive enzymes

Question 48

Within the islets of Langerhans?

Answer 48

There are two types of cells Alpha cells - produce and secrete glucagon Beta cells - produce and secrete insulin

Question 49

Alpha cells vs beta cells

Answer 49

Larger and more numerous than beta cells within an islet

Question 50

Staining of islets?

Answer 50

Very difficult to distinguish between cell types within an islet so differential staining is often used ; beta cells are stained blue and alpha cells are stained pink

Question 51

Glucagon and insulin

Answer 51

Carried into the bloodstream by granules

Question 52

Why does blood glucose matter?

Answer 52

Important that concentration of glucose is kept constant - without control it would range from very high levels after a meal to very low levels ; thus wouldn’t have enough glucose for respiration - this is kept constant by insulin and glucagon

Question 53

Describe glucose

Answer 53

Small and soluble molecule that is carried in the blood plasma ; normally maintained at around 90 mg cm^-3

Question 54

How does blood glucose concentration increase?

Answer 54

Diet Glycogenolysis Gluconeogenesis

Question 55

Diet

Answer 55

When you eat carbohydrate rich foods such as pasta and rice and sweet foods such as cakes and fruit (high levels of sucrose) ; the carbohydrates are broken down to release glucose and this is absorbed into the bloodstream causing blood glucose concentration rises

Question 56

Glycogenolysis

Answer 56

Glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream increasing blood sugar concentration

Question 57

Gluconeogenesis

Answer 57

Production of glucose from non-carbohydrate sources ; liver is able to make glucose from glycerol and amino acids - glucose is released into the bloodstream and causes an increase in blood glucose concentration

Question 58

Lysis

Answer 58

Splitting

Question 59

Neo

Answer 59

“New”

Question 60

Genesis

Answer 60

Means birth;origin

Question 61

Decreasing blood glucose concentration?

Answer 61

Respiration Glycogenesis

Question 62

Respiration

Answer 62

Glucose in the blood is used by cells to release energy : however during exercise more glucose is needed as the body needs to generate more energy in order for muscle cells to contract - higher level of activity = higher demand for glucose = greater the decrease of blood glucose concentration

Question 63

Glycogenesis

Answer 63

Production of glycogen ; when blood glucose concentration is too high, excess glucose taken in through the diet is converted into glycogen which is stored in the liver

Question 64

Insulin

Answer 64

Produced by the beta cells of the islets in the pancreas ; if too high then beta cells detect this rise in blood glucose and respond by secreting insulin directly into the bloodstream

Question 65

Insulin receptors?

Answer 65

All body cells have insulin receptors on their cell surface membrane (except RBCs) ; when insulin binds to its glycoproteins 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 activates the enzymes within some cells to convert glucose to glycogen and fat

Question 66

Insulin lowers blood glucose concentration by

Answer 66

Increasing rate of absorption of glucose by cells (skeletal muscle cells in particular) Increasing respiratory rate of cells ; increases the need for glucose and causes a higher uptake of glucose from the blood Increasing 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 Increasing the rate of glucose to fat conversion Inhibiting the release of glucagon from the alpha cells of the islets

Question 67

How is insulins effect maintained?

Answer 67

Insulin is broken down by enzymes in the cells of the liver ; thus to maintain its effect it has to be constantly secreted and it may continue for several hours after eating As blood glucose concentration returns back 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 (NEGATIVE FEEDBACK) - ensures changes are reversed and returned back to the set level

Question 68

Glucagon

Answer 68

Produced by the alpha cells of the islets in the pancreas ; if blood glucose concentration is too low - the alpha cells detect this fall in blood glucose concentration and respond by secreting glucagon directly into the bloodstream

Question 69

Which two cells in the body have glucagon receptors?

Answer 69

LIVER CELLS AND FAT CELLS ; ONLY CELLS WHICH RESPOND TO GLUCAGON

Question 70

How does glucagon increase blood glucose concentration?

Answer 70

Glycogenolysis - 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

Question 71

As blood glucose concentration returns to normal…

Answer 71

Detected by the alpha cells of the pancreas ; when it rises above a set level the alpha cells reduce their secretion of glucagon - this is another example of negative feedback ; causes the corrective measures to be switched off

Question 72

Interaction of insulin and glucagon

Answer 72

Work together to maintain a constant blood glucose concentration ; they are antagonistic hormones (they work against each other)

Question 73

LOOK AT PAGE 390

Answer 73

Looked at diagram 😊

Question 74

System of maintaining blood glucose concentration?

Answer 74

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 ; blood glucose concentration is not constant but fluctuates around a set point as the result of negative feedback - in time of stress adrenaline is released by the body, one of the effects of this hormone is to raise the blood glucose concentration to allow more respirations tissue occur

Question 75

Control of insulin secretion

Answer 75

When blood glucose concentration rises above the set level ; detected by beta cells in the islets and insulin is released

Question 76

Mechanism of insulin secretion

Answer 76

1) Normal blood glucose concentration levels mean potassium channels in plasma membrane of beta cells are open and potassium ions diffuse OUT OF THE CELL ; the inside of the cell is -70mV with respect to the outside of the cell 2) When blood glucose concentration rises ; glucose enters the cell by a glucose transporter and is metabolised inside the mitochondria resulting in the production of ATP 3) ATP binds to potassium channels and causes them to close ; they are known as ATP-sensitive potassium channels 4) As potassium ions cannot diffuse out of the cell anymore, the potential difference is reduced to -30mV and depolarisation occurs 5) Depolarisation means voltage-gated calcium channels open and calcium ions now enter the cell and cause secretory vesicles to release the insulin they contain by excocytosis

Question 77

Diabetes

Answer 77

Unable to regulate blood glucose concentration ; it is a chronic disease - diabetes mellitus

Question 78

What can patients not do with diabetes?

Answer 78

Unable to metabolise carbohydrates properly - in particular glucose

Question 79

What two causes of diabetes?

Answer 79

Does not produce enough insulin or cannot effectively respond to insulin - thus blood glucose concentration remains high

Question 80

Common effect of uncontrolled diabetes?

Answer 80

Hyperglycaemia - over time this can lead to serious damage to many body systems like nerves/blood vessels

Question 81

Type 1 Diabetes

Answer 81

Unable to produce insulin and the beta cells in the islets do not work - cause is not known and thus the disease cannot be prevented or cured Conditions arise as a result of autoimmune response where the own immune system attacks the beta cells (CHILDHOOD - people develop symptoms quickly)

Question 82

Type 2 Diabetes

Answer 82

Cannot effectively use insulin or do not respond properly to insulin/produce enough insulin - GLYCOPROTEIN insulin receptor on the cell membrane does not work properly and the cells lose their responsiveness to insulin (leave glucose in bloodstream)

Question 83

Causes for type 2 Diabetes

Answer 83

90% of people have type 2 diabetes and this is largely as a result of excess body weight, physical inactivity and habitual/excessive overeating of carbohydrates - symptoms are less severe

Question 84

Risk of type 2 diabetes

Answer 84

Increases with age - but nowadays also seen as children

Question 85

Symptoms of diabetes

Answer 85

High blood glucose concentration Glucose present in urine Excessive urination (polyuria) Excessive thirst (polydipsia) Constant hunger Weight loss + blurred version + tiredness

Question 86

How do symptoms of diabetes arise?

Answer 86

Blood glucose concentration remains high and level of glucose in cells is low

Question 87

Type 1 Diabetes treatment

Answer 87

Controlled by regular injections of insulin - insulin dependent ; a prick test first determines the blood glucose concentration which allows them to work out the dose of insulin they need to inject

Question 88

What does insulin administered do?

Answer 88

Increases amount of glucose absorbed by cells and causes Glycogenesis to occur (reduces blood sugar concentration

Question 89

Too low insulin?

Answer 89

Hyperglycaemia- which can also result in unconsciousness and death ; thus careful monitoring/dose regulation is required

Question 90

If the person injects themselves with insulin?

Answer 90

Causes blood glucose levels to drop quickly

Question 91

Control in type 2 diabetes

Answer 91

Regulate carbohydrate intake through their diet and match this to exercise levels - increases exercise levels and weight loss is needed

Question 92

What else can be done to control type 2 diabetes?

Answer 92

Drugs may also have to be used to stimulate insulin production or slow down the rate at which the body absorbs glucose (slow down breakdown thus less glucose in bloodstream)

Question 93

Original insulin production

Answer 93

Pancreas of cows and pigs

Question 94

Disadvantages of early insulin?

Answer 94

Very expensive and could cause allergic reactions as they differed slightly

Question 95

Advantages of insulin production via GM bacteria?

Answer 95

Less likely to cause allergic reactions Insulin can be produced in much higher quantities Cheaper Religious/ethical concerns are overcome

Question 96

Stem cell treatment in diabetes

Answer 96

Replace the faulty beta cells in pancreatic islets ; after a year patients have no symptoms BUT demand far outweighs their availability and the risk of having transplantable can also be greater than diabetes itself

Question 97

What drugs are needed with stem cell treatment?

Answer 97

Immunosuppressant drugs that are required to ensure the body accepts the transplanted pancreas - leaves the person susceptible to infection

Question 98

Immunosuppressant drugs

Answer 98

Prevent rejection of cells which increases metabolic demand of insulin-producing cells - eventually this exhausts their capacity to produce insulin

Question 99

What type of stem cells are needed?

Answer 99

Totipotent for potential to grow into any body cell type ; likely they be taken from embryos - destroyed a potential JIA,m life and the embryo are used a source for stem cells - they are spare embryos for infertility treatments/terminated pregnancies

Question 100

Stem cell advantages

Answer 100

Donor availability - produce an unlimited number of cells Reduced likelihood of rejection No longer have to inject themselves with insulin

Question 101

Disadvantage stem cells

Answer 101

Uncontrolled control over growth/differentiation means they may form tumours