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A LEVEL Biology > Chapter 14 Hormonal Communication > Flashcards

Chapter 14 Hormonal Communication Flashcards

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1
Q

What is the endocrine system made up of?

A

Endocrine glands
= a group of cells which are specialised to secrete hormones (directly into the bloodstream)

e.g. pancreas gland and adrenal gland

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2
Q

Pituitary gland??

A

At the base of the brain makes several hormones - its close proximity to the hypothalamus ensures that the nervous and hormonal responses of the body are coordinated.

  • produces GROWTH hormone
  • produces ANTI-DIURETIC hormone (increases water absorption in the kidneys)
  • produce GONADOTROPHINS (control the development of ovaries and testes)
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3
Q

Pineal gland??

A
  • produces MELATONIN (affects the reproductive development and daily cycles)
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4
Q

Thyroid gland??

A
  • produces THYROXINE (controls rate of metabolism, rate at which glucose is used up, and promotes growth)
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5
Q

Thymus??

A
  • produces THYMOSIN (promotes production and maturation of white blood cells)
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6
Q

Adrenal gland??

A
  • produces ADRENALINE (increases heart and breathing rate and raises blood sugar level)
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7
Q

Pancreas??

A
  • produces INSULIN (converts excess glucose into glycogen in the liver and glucagon which converts glycogen back into glucose)
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8
Q

Testis??

A
  • produces TESTOSTERONE (controls sperm production and secondary sexual characteristics)
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9
Q

Ovary??

A
  • produces OESTROGEN (controls ovulation and secondary sexual characteristics)
  • produces PROGESTERONE (prepares the uterus lining for receiving an embryo)
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10
Q

What is the diff between ENDOcrine glands and EXOcrine glands?

A

EXOcrine glands secrete chemicals through ducts into organs, or to the surface of the body.

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11
Q

Types of hormones?

A

(1) steroids

(2) proteins

(3) glycoproteins

(4) polypeptides

(5) amines

(6) tyrosine derivatives

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12
Q

When are hormones secreted generally?

A

When a gland is stimulated - which can occur as a result of…
- a change in conc.
- another hormone
- nerve impulse

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13
Q

Target cells??

A

Once secreted the hormones are transported in the blood plasma all over the body.

Hormones diffuse out of the blood and bind to specific receptors of that hormone
- found on the membranes or in the cytoplasm of cells in the target organs = target cells

Once bound to their receptors the hormones stimulate the target cells to produce a response.

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14
Q

What are steroid hormones?

A

They are LIPID SOLUBLE.
- they pass through the lipid component of the cell membrane
- they bind to steroid hormone receptors = hormone-receptor complex
(receptors either in cytoplasm or nucleus)

e.g. Oestrogen

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15
Q

What does the hormone-receptor complex do?

A

Attaches to DNA…

Acts as a transcription factor which either inhibits/facilitates the transcription of a specific gene.

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16
Q

What are non-steroid hormones?

A

They are hydrophilic so cannot pass directly through the cell membrane.
- they bind to the specific receptors at the surface membrane of the target cell

  • this triggers a cascade reaction mediated by chemicals called SECOND MESSENGERS

e.g. Adrenaline

17
Q

Hormonal v.s. Neuronal communication?

A

Hormones are to released directly onto their target cells = slower and less specific form of communication.

Hormones are not broken down as quickly as neurotransmitters, therefore have a longer lasting and widespread response.

18
Q

What are the adrenal glands?

A

3cm- 5cm

  • located at the top of each kidney and made up of 2 distinct parts surrounded by a capsule

(1) ADRENAL CORTEX
- outer region of the glands
- produces the ESSENTIAL hormones (e.g. cortisol and aldosterone)

(2) ADRENAL MEDULLA
- inner region of the glands
- produces the NON-essential (e.g. adrenaline)

19
Q

What are the 3 main types of hormones produced by the adrenal cortex?

A

The production of hormones by the adrenal cortex is controlled by hormones released from the pituitary gland.

(1) GLUCOCORTICOIDS (release controlled by hypothalamus)
- CORTISOL (regulates metabolism - by controlling how the body converts fats, proteins, and carbs into energy) AND (regulates blood pressure and cardiovascular function in response to stress)

  • CORTICOSTERONE (works with cortisol to regulate immune response and suppress inflammatory reactions)

(2) MINERALCORTICOIDS (release triggered by kidneys)
- ALDOSTERONE (which helps controls blood pressure by maintaining the balance between salt and water conc. in blood and body fluids).

(3) ANDROGENS
- small amounts of male/female sex hormones
(relatively small impact compared to those of larger amounts - oestrogen and testosterone)
- still important especially in women after menopause.

20
Q

What are the hormones secreted by the adrenal medulla?

A

The hormones of the adrenal medulla are released when the sympathetic nervous system is stimulated (when the body is stressed).

(1) ADRENALINE
- increases the heart rate sending blood quickly to the muscles and brain
- rapidly raises blood glucose conc. levels by converting glycogen into glucose in the liver

(2) NORADRENALINE
- works with adrenaline in response to stress
- increases heart rate
- widens pupils
- widens air passages in the lungs
- narrowing of blood vessels in non-essential organs (higher blood pressure)

21
Q

What are the 2 main functions of the pancreas in the body?

A

(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

22
Q

Pancreas’ role as an EXOcrine gland? AND what three digestive hormones does it produce?

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

(1) AMYLASE - breaks down starch into simple sugars

(2) PROTEASE - breaks down proteins into amino acids

(3) LIPASES - breaks down lipids into fatty acids and glycerol

23
Q

Pancreas’ role as an ENDOcrine gland?

A
  • the pancreas is responsible for producing insulin and glucagon (roles in blood glucose conc.)

Within the exocrine tissue, there are regions of ENDOcrine tissue = ISLETS OF LANGERHANS
- responsible for producing insulin and glucagon and secreting these directly into the blood

24
Q

Histology of the pancreas? (diff between pancreatic acini and islets)

A

Appearance
- islets = LIGHTLY stained
- acini = DARKER staines

Shape
- islets = large, spherical clusters
- acini = small, berry-like clusters

Type of tissue
- islets = endocrine pancreas
- acini = exocrine pancreas

Function
- islets = produce and secrete hormones
- acini = produce and secrete digestive enzymes

25
Q

Different types of cells in the Islets of Langerhans?

A

(1) a = alpha cells = produce and secrete GLUCAGON

(2) ß = beta cells = produce and secrete INSULIN

  • alpha cells are larger and more numerous than beta cells within an islet.
26
Q

What type of staining do you use on the pancreas?

A

Differential staining

ß cells = blue
a cells = pink

27
Q

What is glucose?

A

Glucose is a small, soluble molecule that is carried in the blood plasma.
- it is normally maintained at a concentration of approx. 90mg/cm^3 of blood

28
Q

When can blood glucose conc. INCREASE?

A

(1) Diet
- when you eat carb-rich foods (high in starch or sucrose)
- carbs are broken down into glucose
- glucose released is absorbed into the bloodstream, and blood glucose conc. rises

(2) GLYCOGENOLYSIS
- glycogen stored in the liver and muscle cells is broken down into glucose and released into the blood

(3) GLUCONEOGENESIS
- the production of glucose from non-carb sources

29
Q

When can blood glucose conc. DECREASE

A

(1) Respiration
- some of the glucose in the blood is used up by cells to release energy.

(2) GLYCOGENESIS
- the production of glycogen (store when glucose conc. is too high)

30
Q

How do the islets of Langerhans react when blood glucose conc. is too high?

A

Insulin is produced by the BETA cells of the islets.

Beta cells detect the rise in conc. and respond by secreting insulin directly into the bloodstream.

31
Q

INSULIN??

A

Most body cells have insulin receptors on their cell surface membrane.
- 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 activates enzymes within some cells to convert glucose to glycogen and fat
32
Q

How does insulin lower blood glucose conc. ?

A

(1) increasing the rate of absorption of glucose by cells

(2) increasing the respiratory rate of cells - increases their need for glucose

(3) increasing the rate of glycogenesis - stimulates the liver

(4) increasing the rate of glucose to fat conversion

(5) inhibiting the release of glucagon from the alpha cells of the islets

33
Q

Negative feedback??

A

When blood glucose conc. falls below a set level…

  • the beta cells detect this and reduce their secretion of insulin

When blood glucose conc. rises above a set level…

  • the alpha cells detect this and reduce their secretion of glucagon
34
Q

GLUCAGON??

A

Glucagon is produced by alpha cells of the islets.

The only cells that have glucagon receptors are the liver and fat cells.

35
Q

How does glucagon raise blood glucose conc. ?

A

(1) glycogenolysis - liver breaks down glycogen store into glucose

(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

36
Q

Why is the system o maintaining blood glucose conc. considered to be self-regulating?

A

It is the level of glucose in the blood that determines the quantity of insulin and glucagon that is released.

37
Q

Control of insulin secretion (mechanism)?

A

(1) at normal levels, POTASSIUM channels in the plasma membrane of beta cells are open and K+ ions diffuse out of the cell.
- the inside of the beta cell is at a potential of -70mV

(2) when conc. rises, glucose enters the cell by a glucose transporter

(3) the glucose is metabolised inside the mitochondria - producing ATP

(4) the ATP binds to the potassium channels and causes them to close
= ATP-sensitive potassium channels

(5) as K+ ions can no longer diffuse out of the cell, the potential reduces to -30mV and DEPOLARISATION occurs

(6) Depolarisation causes the voltage-gated CALCIUM channels to open

(7) Ca2+ (calcium ions) enter the cell and cause secretory vesicles to release the insulin they contain by EXOCYTOSIS.

A LEVEL Biology (4 decks)

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