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A Level Biology > Chapter 14: Hormonal Communication > Flashcards

Chapter 14: Hormonal Communication Flashcards

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1
Q

Using a named example explain the function of an endocrine gland.

A

Produce + secrete hormones directly into the bloodstream.

E.g. Adrenal Glands –> adrenal medulla produces adrenaline.

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2
Q

Describe the pathway triggered by stimulus in hormonal communication.

A
  1. Stimulus detected.
  2. Gland stimulated.
  3. Hormone secreted.
  4. Travels in blood plasma.
  5. Hormone and receptors complementary.
  6. Binds to receptors in cytoplasm or membrane of target cells to produce a response
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3
Q

What is the role of the pancreas as an endocrine gland?

A

Has islets of Langerhans –> made up of alpha and beta cells.

Beta cells = produce and secrete insulin –> converts excess glucose to glycogen –> lower BGC.

Alpha cells = produce and secrete glucagon –> converts glycogen back into glucose –> increase BGC

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4
Q

What is the role of the pancreas as an exocrine gland?

A

Produce and secrete digestive enzymes (amylase, protease, lipase) + pancreatic juice through pancreatic ducts into duodenum of small intestine.

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5
Q

Define glycogenolysis

A

Glycogen in liver + muscle cells broken down into glucose.

Glucose released into bloodstream increasing BGC.

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6
Q

Define gluconeogenesis

A

Glucose produced from non-carbohydrate sources.

E.g. liver –> produces glucose from glycerol (lipids) or amino acids.

Glucose released into bloodstream increasing BGC.

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7
Q

Define glycogenesis

A

Production of glycogen.

When BGC too high –> excess glucose converted into glycogen and stored in the liver.

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8
Q

How is insulin secretion controlled?

A
  1. At normal BGC –> K+ channels in plasma membrane of beta cells are open –> K+ ions diffuse out of cell –> p.d. = -70mV inside cell with respect to outside.
  2. When BGC rises –> glucose enters cell via a glucose transporter.
  3. Glucose metabolised inside mitochondria –> produces ATP.
  4. ATP binds to K+ channels –> causes them to close –> ATP-sensitive potassium channels.
  5. K+ ions no longer diffuse out of cell –> p.d. = -30mv –> depolarisation occurs.
  6. Depolarisation –> causes voltage gated Ca2+ channels to open.
  7. Ca2+ ions enter cell –> cause secretory vesicles to release insulin by exocytosis.
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9
Q

Describe the role glucagon plays in the control of blood glucose conc.

A

Increase BGC.

Binds to receptors on liver cells.

Causes glycogenolysis.

Inhibit insulin secretion.

Conversion of triglycerides to fatty acids.

Gluconeogenesis.

Negative feedback –> inhibit glucagon secretion.

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10
Q

Explain how hormones return blood glucose conc. to normal after a meal.

A

Causes BGC to rise –> rise detected by beta cells in islets of Langerhans.

Beta cells release insulin into blood –> insulin binds to glycoprotein receptors on cell surface membrane.

Cells absorb more glucose.

Cell respiration rate increases.

Glycogenesis increases –> conversion of glucose into glycogen –> decreases BGC.

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11
Q

Evaluate using pancreatic beta islet cell transplants to treat diabetes.

A

Advantages:

  • Permanent cure.
  • No reliance on drugs.

Disadvantages:

  • Could be rejected.
  • Person’s immune system permanently repressed.
  • Not enough donor organs available.
  • Person becomes susceptible to infections.
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12
Q

Evaluate use of stem cells to treat diabetes.

A

Advantages:

  • Permanent cure.
  • No reliance on drugs.
  • No risk of rejection.
  • Stem cells readily available.

Disadvantages:

  • Technology not ready yet.
  • Embryos have to be destroyed.
  • Risk of tumours developing.
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13
Q

Evaluate use of insulin injections/medication to treat diabetes.

A

Advantages:

  • Readily available.
  • Dose can be altered easily.
  • Cheap.

Disadvantages:

  • Reliant on drugs.
  • Side effects.
  • Person has to inject themselves.
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14
Q

Role of adrenaline?

A

Triggers glycogenolysis.

More glucose respired.

More ATP respired.

More ATP produced –> more muscle contraction.

Increase BGC.

Hydrophilic hormone –> cannot pass through cell membrane.

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15
Q

Actions of adrenaline?

A
  1. Adrenaline binds to receptor on the outside of a cell.
  2. It activates adenylyl cyclase on the inside of the cell.
  3. This enzyme converts ATP into cyclic AMP.
  4. Cyclic AMP acts as a second messenger that activates other enzymes (e.g. Protein Kinase A).
  5. These enzymes convert glycogen to glucose.
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16
Q

Why do people feel cold in times of stress?

A
  • Less blood in skin to keep it warm –> explains the cold.

- Blood redirected to muscles to aid movement.

17
Q

Explain how the nervous and endocrine system work together to enable body to respond to danger.

A
  1. Danger detected by autonomic nervous system.
  2. Hypothalamus stimulates sympathetic nervous system.
  3. Nerve impulse triggers release of hormones (adrenaline + noradrenaline) from adrenal medulla.
  4. Adrenaline –> glycogenolysis in liver cells –> (cAMP second messenger, which activates other enzymes to break down glucagon into glucose).
  5. Increase blood glucose used for respiration/create energy for muscle contraction.
  6. Pituitary gland stimulates adrenal-cortical system –> hormones released from adrenal cortex (ACTH).
18
Q

Explain why blood pH varies during exercise

A

Increased respiration –> increases production of CO2.

CO2 dissolves in blood to form carbonic acid –> lowers blood pH.

19
Q

Explain why an increase in pH leads to a decrease in heart rate

A
  1. Chemoreceptors detect increase in pH.
  2. Frequency of impulses sent to medulla oblongata decrease.
  3. Decrease in impulses sent to SAN.
  4. SAN decreases heart rate.
20
Q

Name examples of endocrine glands.

A
  • Pituitary gland –> growth hormone, ADH, gonadotrophin.
  • Thyroid gland –> thyroxine –> control metabolism rate.
  • Adrenal gland –> produce adrenaline.
  • Testis –> testosterone.
  • Pineal gland –> melatonin.
  • Thymus –> thymosin –> produce + mature WBC.
  • Pancreas –> insulin, glucagon.
  • Ovary –> oestrogen, progesterone.
21
Q

Name the three main hormones produced by the adrenal cortex.

A
  • Glucocorticoids –> e.g. cortisol (regulate metabolism) + corticosterone (regulate immune system).
  • Mineralocorticoids –> e.g. aldosterone (control blood pressure).
  • Androgens –> male + female sex hormones released.
22
Q

How does insulin lower BGC?

A
  • Increase rate of absorption of glucose by cells.
  • Increase respiratory rate of cells.
  • Increase rate of glycogenesis.
  • Increase rate of glucose to fat conversion.
  • Inhibit release of glucagon from alpha islet cells.
23
Q

What is the effect of exercise on cardiac output?

A
  1. Increased muscular/metabolic activity.
  2. More CO2 produced by tissues –> increased aerobic respiration.
  3. Blood pH lowers.
  4. Medulla oblongata increases frequency of impulses to SAN via sympathetic nervous system.
  5. SAN increases heart rate.
  6. Increased blood flow removes CO2 faster.
  7. CO2 levels return to normal.
24
Q

Function + location of baroreceptors?

A
  • Detect changes in blood pressure.
  • Low BP –> heart rate increases to prevent fainting.
  • Present in aorta, vena cava, carotid arteries.
25
Q

Function + location of chemoreceptors?

A
  • Detect changes in chemical (CO2)/pH levels.

- Located in aorta, carotid artery, medulla.

26
Q

Explain why increase in blood pressure leads to decrease in heart rate.

A
  1. Baroreceptors detect increase in BP.
  2. Impulses send to medulla oblongata centre which decreases heart rate.
  3. Medulla oblongata sends impulses along parasympathetic neurones (vagus nerve) to SAN which decreases heart rate.
  4. BP returns to normal
27
Q

Explain why decrease in blood pressure leads to increase in heart rate.

A
  1. Baroreceptors detect decrease in BP.
  2. Impulses send to medulla oblongata centre which increase heart rate.
  3. Medulla oblongata sends impulses along sympathetic neurones (accelerator nerve) to SAN which increases heart rate.
  4. BP returns to normal.
28
Q

Describe how negative feedback is used to control BGC.

A
  1. Beta cells/alpha cells detect increase/decrease in BGC.
  2. High BGC –> beta cells produce insulin:
  • Increased uptake of glucose by liver through glucose transport proteins in cell surface membrane.
  • Glucose converted to glycogen –> glycogenesis.
  • Increase use of glucose in respiration.
  1. Low BGC –> alpha cells produce glucagon:
  • Increased conversion of glucose to glycogen –> glycogenolysis.
  • Increased conversion of non-carbohydrate compounds to glucose –> gluconeogenesis.
  • Glucose leaves cells by facilitated diffusion through glucose channels.
29
Q

Suggest how the adrenaline molecule can cause different effects in different target tissues.

A
  • Different tissues have different adrenaline receptors.
  • Causing cAMP conc. to increase or decrease.
  • Second messenger may be different.
  • cAMP activates other enzymes.
30
Q

Outline the hormonal + nervous mechanisms involved in control of heart rate.

A
  • Adrenaline increases heart rate.
  • Cardiovascular centre in medulla oblongata.
  • Nervous connection to SAN controls frequency of waves of depolarisation.
  • Vagus nerve –> decreases HR.
  • Accelerator nerve –> increases HR.
  • High BP detected by baroreceptors.
  • Low blood pH detected by chemoreceptors.
  • Baroreceptors + chemoreceptors in carotid arteries/aorta.
31
Q

Explain how type 1 diabetes is caused.

A
  • Unable to produce insulin.
  • Beta cells damaged by body’s own immune system.
  • Genetic.
  • Triggered by virus/external factor.

A Level Biology (21 decks)

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