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IB Biology HL > Option D5 Hormones and Metabolism > Flashcards

Option D5 Hormones and Metabolism Flashcards

1
Q

Endocrine system

A

Comprised of ductless glands that release chemicals into the blood to regulate body functions.
- Slower to initiate than the nervous system, but has a more prolonged response

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2
Q

Hormone

A

A chemical messenger that is transported indiscriminately via the bloodstream to act on distant target cells.
- Specific (will only activate cells/tissues that possess an appropriate target receptor)

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3
Q

Endocrine glands

A

Secrete their hormones directly into the bloodstream rather than through a duct.

  • Major glands: pancreas, adrenal gland, thyroid gland, pineal gland, and gonads
  • Some organs (ex. adipose tissue) can secrete hormones despite not being an endocrine gland
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4
Q

Neuroendocrine glands

A

The hypothalamus and pituitary gland, which function to link nervous and endocrine systems.

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5
Q

Pineal gland

A
  • Secretes: melatonin
  • Targets: many organs
  • Function of hormone: a biological clock
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6
Q

Pituitary gland

A
  • Secretes: FSH/LH, ADH, growth hormone, oxytocin, and prolactin
  • Targets: ovaries, kidneys, many organs, uterus, and breast tissue respectively
  • Function of hormone: menstrual cycle, osmoregulation, growth/division, birth contractions, and milk production respectively
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7
Q

Thyroid gland

A
  • Secretes: thyroxin
  • Targets: liver
  • Function of hormone: metabolic rate
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8
Q

Adrenal glands

A
  • Secretes: adrenaline and cortisol
  • Targets: many organs (for both)
  • Function of hormone: fight or flight and anti-stress respectively
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9
Q

Pancreas

A
  • Secretes: insulin/glucagon
  • Targets: liver
  • Function of hormone: regulation of blood glucose levels
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10
Q

Ovaries

A
  • Secretes: estrogen/progesterone
  • Targets: uterus
  • Function of hormone: menstrual cycle
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11
Q

Testes

A
  • Secretes: testosterone
  • Targets: many organs
  • Function of hormone: male characteristics
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12
Q

Steroid hormones

A
  • Lipophilic (fat-loving), meaning they can freely diffuse across plasma membranes
  • Bind to receptors in the cytoplasm/nucleus of the target cell to form an active receptor-hormone complex
  • Activated complex will move into the nucleus and bind directly to DNA, acting as a transcription factor for gene expression
  • Examples: those produced by the gonads (ex. estrogen, progesterone, and testosterone)
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13
Q

Peptide hormones

A
  • Hydrophilic and lipophobic (fat-hating), meaning they cannot freely cross plasma membranes
  • Bind to receptors on the surface of the cell, which are typically coupled to internally-anchored proteins
  • Receptor complex activates a series of second messengers
  • Examples: insulin, glucagon, leptin, ADH, and oxytocin
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14
Q

Second messengers

A

A series of intracellular molecules that initiate cell activity when activated by the receptor complex.

  • Enables the amplification of initial signal
  • Examples: cyclic AMP, calcium ions, nitric oxide, and protein kinases
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15
Q

Hypothalamus

A

The section of the brain that links the nervous and endocrine systems in order to maintain homeostasis.

  • Receives information from nerves and initiates endocrine responses
  • Secretes neurochemicals (releasing factors) into a portal system which target the anterior pituitary gland
  • Secretes hormones directly into blood via neurosecretory cells that extend into the posterior pituitary lobe
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16
Q

Pituitary gland

A

Receives instructions from the hypothalamus and consists of two lobes (anterior and posterior).
- Lies adjacent to the hypothalamus and is in direct contact due to a portal blood system

17
Q

Anterior pituitary gland (adenohypophysis)

A

Releasing factors from the hypothalamus are released into portal vessels by neurosecretory cells, stimulating endocrine cells in the anterior pituitary to release specific hormones into the bloodstream.
- Example: releasing factor GnRH triggers the release of LH/FSH from the anterior pituitary

18
Q

Posterior pituitary gland (neurohypophysis)

A

Releases hormones produced by the hypothalamus itself via neurosecretory cells.
- Neurosecretory cells extend into the posterior lobe from the hypothalamus and release hormones into the blood

19
Q

Targets of pituitary hormones

A

Mnemonic device: MARGE

  • Metabolism (ex. thyroxin）
  • Adult development (ex. LH/FSH in triggering puberty)
  • Reproduction (ex. LH/FSH control menstruation)
  • Growth (ex. growth hormone)
  • Equilibrium/homeostasis (ex. maintaining water balance through ADH)
20
Q

Growth hormone (somatotropin)

A

An anabolic peptide hormone that stimulates growth.

  • Acts directly to reduce the formation of adipose cells (less nutrients stored as fat)
  • Acts indirectly via insulin growth factors (IGF) produced by the liver to increase muscle mass and bone size
21
Q

Somatotropin as performance enhancers

A
  • The use of human growth hormone is banned in sports, with proven cases of doping strictly punished
  • Traditional urine testing could not detect doping, which historically made bans difficult to enforce
  • Recent blood tests can now identify between natural and artificial variants of growth hormone
22
Q

Lactation

A

The production and secretion of milk by maternal mammary glands following birth.
- Predominantly controlled and regulated by oxytocin and prolactin

23
Q

Prolactin

A

Responsible for the development of mammary glands and the production of milk.

  • Secreted by the anterior pituitary in response to the release of PRH (prolactin releasing hormone) from the hypothalamus
  • Effects are inhibited by progesterone, which prevents milk production from occurring prior to birth
24
Q

Oxytocin

A

Responsible for the release of milk from the mammary glands (milk ejection reflex).

  • Produced in the hypothalamus and secreted by neurosecretory cells that extend into the posterior pituitary
  • Triggered by the stimulation of sensory receptors in the breast tissue by the suckling infant
  • Creation of a positive feedback look will result in continuous oxytocin secretion until infant stops feeding
25
Q

Types of cell signalling

A
  • Autocrine: when chemicals released by the cell stimulate the cell itself.
  • Paracrine: when chemicals released stimulate a neighbor cell
  • Endocrine: when chemicals released travel in the bloodstream to activate distant cells
26
Q

Types of secretion

A
  • Constitutive: hormones released as they are produced (with vesicles fused with the cell membrane)
  • Regulated: hormones are stored in vesicles and released following an external signal
27
Q

Peptide hormones

A
  • Synthesized to require further processing to activate
  • Stored in vesicles for regulatory secretion
  • Mostly polar and water-soluble (can travel freely in blood)
  • Binds to receptors on cell membrane and transduce signal via the use of second messenger systems
  • Gene expressions can change
  • Examples: insulin, glucagon, and prolactin
28
Q

Steroid hormones

A
  • Synthesized in a series of reactions from cholesterol
  • Released immediately (constitutive secretion)
  • Generally non-polar and require carrier proteins to travel in blood
  • Binds to intracellular receptors to change gene expression directly
  • Slower onset, longer duration in changes of gene expression
  • Examples: cortisol, estrogen, progesterone, and testosterone
29
Q

Amino acid derivatives (hormone)

A
  • Synthesized from amino acid tyrosine
  • Stored before release (but mechanism varies)
  • Some (ex. adrenaline) are polar, others are protein-bound
  • Acts on membrane or nuclear receptors
  • Function like peptides or similar to steroids
  • Examples: adrenaline and thyroxin
30
Q

Negative feedback

A

Involves a response that is the reverse of the change detected (it functions to reduce the change).
- Examples: thermoregulation, blood sugar regulation, osmoregulation

31
Q

Positive feedback

A

Involves a response that reinforces the change detected (it functions to amplify the change).
- Examples: childbirth, lactation, ovulation, blood clotting

32
Q

Goiter

A

A condition whereby the individual develops an enlarged thyroid gland because of an iodine deficiency.

  • Thyroxin contains iodine and cannot be produced if iodine is deficient in the diet
  • Iodine is not a component of most diets (common in seafood but not others)

IB Biology HL (32 decks)

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