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biology year 13 a-level rev rev revision > Chapter 14 - Hormonal Communication > Flashcards

Chapter 14 - Hormonal Communication Flashcards

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1
Q

What is Endocrine Communication?

A
  • Glands secrete hormones into bloodstream
  • Circulatory system carries hormone to target cell/tissue
  • Lipid-soluble steroid hormones diffuse into cell + bind to complimentary receptor in cytoplasm - Peptide hormones bind to complimentary receptor on cell-surface membrane
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2
Q

Describe the structure of the adrenal glands

A
  • located above kidneys

- has a central medulla, surrounded by an external cortex, surrounded by an outer layer.

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3
Q

What hormone does the medulla secrete?

A

Adrenaline - responds to stress, danger or excitement as part of fight or flight response.

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4
Q

Which horomes does the cortex secrete?

A
  • Mineralocorticoids - e.g. aldosterone, targets kidney and gut to control conc. of Na+ and K+ in blood.
  • Glucocorticoids - e.g. cortisol + corticosterone, stimulates increase in blood glucose concentration.
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5
Q

Why is it important that blood glucose concentration remains stable?

A
  • Maintain healthy blood water potential, to prevent osmotic lysis / crenation of cells.
  • Maintain constant concetration of respiratory substrate : organism maintains constant level of activity regardless of environment conditions.
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6
Q

Define negative feedback

A
  • Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation.
  • Different mechanisms are responsible for dealing with an increase/decrease in normal level for greater control.
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7
Q

Define Glycogenesis

A

Liver converts glucose into storage polymer glycogen

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8
Q

Define Glycogenolysis

A

Liver hydrolyses glycogen into glucose, which diffuses into the blood

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9
Q

Define Gluconeogenesis

A

Liver converts glycerol + amino acids into glucose

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10
Q

Outline the role of glucagon when blood glucose concentration decreases

A
  1. alpha cells in islets of langerhans (pancreas) detect decrease + secrete glucagon into the bloodstream.
  2. Glucagon binds to surface receptors on liver cells + activates enzymes for glycogenolysis + gluconeogenesis
  3. Glucose diffuses from liver to bloodstream
  4. alpha cells detect increased BGC and stop producing glucagon (negative feedback)
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11
Q

What is the secondary messenger model for glucagon?

A
  1. Hormone-receptor complex forms
  2. Conformational changes to receptor activates G-protein
  3. Activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP)
  4. cAMP activates protein kinase A pathway
  5. results in glycogenolysis
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12
Q

Outline what happens when blood glucose conc. increases

A
  1. B cells in islets of langerhans in pancreas detect + secrete insulin to bloodstream
  2. Insulin binds to surface receptors on target cells to:
    A. increase cellular glucose uptake
    B. activates enzymes for glycogenesis
    C. stimulate adipose tissue to synthesise fat
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13
Q

Describe how insulin leads to a decrease in blood glucose concentration

A
  • Increases permeability of cells to glucose
  • Increases glucose concentration gradient
  • Triggers inhibition of enzymes for glycogenolysis
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14
Q

How is insulin secretion controlled?

A
  1. B cells have K+ + Ca2+ ion channels to maintain potential difference (-70mV)
  2. As Glucose Conc. increases, glucose enters B cells via facilitated diffusion
  3. Respiration of glucose produces ATP. ATP-gated K+ channels close, K+ ions no longer diffuse out of cell.
  4. P.D. in cell becomes more positive = depolarisation. Ca2+ ion channels open. Ca2+ triggers exocytosis of insulin.
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15
Q

Describe exocrine function of pancreas

A

Secretes digestive enzymes e.g. amylase, tripase, and lipase to the duodenum via the pancreatic tract.

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16
Q

Explain causes of Type 1 Diabetes

A

Body cannot produce insulin e.g. due to autoimmune disease which attacks B cells of islets of langerhans

17
Q

How can type 1 diabetes be controlled

A

Inject insulin from animal source or genetically modified bacteria - possible future treatment involving stem cells to produce new B cells.

18
Q

Explain causes of Type 2 Diabetes

A

Glycoprotein receptors become damaged or become less responsive to insulin.

19
Q

How can type 2 diabetes be controlled

A
  • Strong correlation w/ poor diet + obesity.

- Treat by controlling diet + exercise regime.

20
Q

What is the difference between Steroid and non-Steroid hormones?

A
  • Steroid hormones = lipid soluble - forms hormone-receptor complex inside the cell.
  • Non-Steroid hormones = lipid insoluble - forms hormone-receptor complex on cell surface. Causes cascade reactions, mediated by secondary messenger chemicals.
21
Q

What are some differences between the hormonal system and the nervous system?

A
  • Hormonal - hormones, transported via blood, response widespread and slow, slow transmission, long-lasting effect.
  • Nervous - nerve impulses, transmission via neurones, response localised and rapid, fast transmission, short-lived effect.
22
Q

What is the difference between adrenaline and noradrenaline?

A

(both secreted from adrenal medulla)

  • Adrenaline increases heart rate, increases blood glucose concentration. (converts glycogen to glucose in the liver)
  • Noradrenaline widens pupils, widens lung air passage, and narrows blood vessels in non-essential areas (higher blood pressure)
23
Q

What are the 2 main functions of the pancreas?

A
  • Exocrine - produce enzymes + release via a duct in the duodenum
  • Endocrine - produce horomes + release into the blood.
24
Q

What are the main products of the pancreas’s exocrine function?

A
  • Amylase - break down starch into simple sugars e.g. pancreatic amylase
  • Proteases - break down proteins into amino acids e.g. trypsin
  • Lipases - break down lipids into fatty acids + glycerol - e.g. pancreatic lipase.
25
Q

What is the difference between the alpha and beta cells in the islets of langerhans

A

a - produce + secrete glucagon

b - produce + secrete insulin

26
Q

What is the normal blood glucose concentration?

A

roughly 90 mgcm^-3

27
Q

What are ways to increase blood glucose concentration?

A
  • Eat carb-rich foods, or sugary foods.
  • Glycogenolysis
  • Gluconeogenesis
28
Q

What are ways to decrease blood glucose concentration?

A
  • Respiration - higher activity = higher demand for glucose = decreased blood glucose
  • Glycogenesis

biology year 13 a-level rev rev revision (13 decks)

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