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BIOMOLECULES AND CELLS > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

Define hormones

A

Molecular signals released by specific cell types and influence other cells.

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2
Q

Hormone activity

A

Hormones are secreted into the interstitial fluid, passed into the blood then travel to target call.

They act at a distance.

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3
Q

Paracrine and autocrine activity

A
  • Hormones are released into the interstitial fluid and act on nearby cells (act locally)
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4
Q

What are the three main groups of hormones?

A
  • peptides / proteins
  • steroid hormones
  • amines
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5
Q

Describe how peptides/ proteins are transported

A
  • water soluble
  • easily transported in blood
  • packaged within vesicles and secreted via exocytosis

e.g. insulin

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6
Q

How are Steroid hormones (lipids) transported?

A
  • lipid soluble
  • can easily cross membrane (via diffusion) therefore not stored in vesicles
  • need carriers to travel in the blood

e.g. testosteron

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7
Q

Solubility of Amines

A
  • can be water-soluble or lipid soluble so mode of action differs
    e. g. epinephrine (water soluble), thyroxine (lipid soluble)
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8
Q

What are the two types of glands in the body?

A
  • exocrine

- endocrine

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9
Q

Describe the function of endocrine glands

A
  • collection of cells that secrete hormones

e. g. endocrine pancreas secretes insulin and glucagon directly into blood

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10
Q

Describe the function of exocrine glands

A
  • have ducts carry molecules to specific location

e. g. exocrine pancreas secretes enzymes (not hormones) via duct to duodenum

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11
Q

What are the 2 main parts of the adrenal gland and what hormones are produced in these areas?

A
  • outer cortex: cortisol, aldosterone

- inner medulla: epinephrine, norepinephrine

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12
Q

What is the function of cortisol?

A

Regulates a wide range of processes and helps the body respond to ongoing stress

Has an anti-inflammatory effect, and reduces the immune system activity (high levels can be detrimental)

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13
Q

How do we know when we are stressed and which process is first?

A
  • Emotion and cognitive abilities are affected first and then the physiological responses occur
  • stress is first detected by the brain and then the hypothalamus
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14
Q

What process occurs to increase energy in times of stress?

A

Break down of glycogen is into glucose is stimulated.

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15
Q

Effects of epinephrine vs cortisol?

A
  • epinephrine: released within seconds of exposure to stress, and decreases within minutes
  • cortisol take minutes to be released but the effects last for hours.
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16
Q

Where are the receptors located that detect cortisol vs. epinephrine?

A
  • Cortisol: steroid hormone and can cross lipid membrane and has a nuclear receptor. Switches on RNA to synthesise a protein.
  • Epinephrine (amino acid derived): Membrane bound receptors and stimulates enzymes already present to stimulate a quick response.
17
Q

Define neurohormone

A
  • any hormone produced and released by neuroendocrine cells (neurons that secrete hormones) into the blood.
18
Q

Describe the posterior pituitary and the process that lead to the release of hormones.

A
  • Hypothalamic neurons produce ADH, Oxytocin.
  • they travel via the neurons’ axon to the axon terminal and is stored in vesicles.
  • neurohormones are released into the posterior pituitary and then into capillaries.
19
Q

Describe the anterior pituitary and the process that lead to the release of hormones.

A
  • Neurons in the hypothalamus are very short and end on the portal vessels.
  • Portal vessels receive neurohormones (releasing factors) from hypothalamus
  • Hormones travel a short distance via the blood to the anterior pituitary
  • hormones released by the anterior pituitary make their way into the bloodstream.
20
Q

Compare the anatomy and function of the posterior and anterior pituitary.

A

Length of neurons

  • A: short
  • P: long

Both have capillary systems

  • A: hormones arrive via portal vessels
  • P: hormones arrive via axon terminals

Type of tissue

  • A: Cellular
  • P: Neural
21
Q

What type of tissue are both the anterior and posterior pituitary made up of?

A

Epithelial tissue: Since they both involve the release hormones (secretory function)

22
Q

Describe the synthesis of thyroxine.

A
  1. A follicle cell takes up iodine from blood.
  2. cell synthesises thyroglobulin.
  3. thyroglobulin and iodine are secreted into the follicle lumen. Thyroglobulin is iodinated.
  4. Iodinated thyroglobulin is taken up by follicle cell
  5. Enzymes digest thyroglobulin into T3 and T4
  6. T3 and T4 are secreted into the blood
23
Q

What is the function of thyroxine?

A
  • Regulates the metabolic rate of most cells.

- crucial for normal development and growth

24
Q

Describe the cell signalling pathway of thyroxine.

A

Thyroxine binds to nuclear receptors to activate transcription of enzymes involved in energy metabolic pathways.

25
Q

Hyperthyroidism causes

A
  • antibodies bind to the TSH receptors on thyroid gland
  • this binding mimics the binding of TSH
  • there is constant stimulation and hence continuous cell division
  • high levels of thyroxine and low levels of TSH
  • negative feedback occurring but ineffectual since antibodies cannot be removed.

Therefore thyroid gland increases in size.

26
Q

Treatment for hyperthyroidism

A

Inhibit the enzyme thyroperoxidase and prevent the iodination of thyroglobulin.

27
Q

Hypothyroidism causes and treatment

A
  • most often due to low dietary iodine
  • no negative feedback occurring due to low thyroxine levels
  • so thyroid gland constantly produces thyroglobulin, however it is poorly iodinated
  • still results in enlarged thyroid gland
28
Q

Treatment for hypothyroidism

A

Daily, synthetic form of T4 (thyroxine)

29
Q

What are tropic hormones?

A

A hormone that stimulates an endocrine gland to grow and secrete it’s hormones
- in humans anterior pituitary gland releases the most tropic hormones

30
Q

What are the 4 main tropic hormones?

A
  • FSH
  • LH
  • TSH
  • ACTH
31
Q

What hormones are released from the posterior pituitary?

A
  • ADH

* Oxytocin

32
Q

How is TSH regulated in the body?

A
  1. external or internal stimuli signals hypothalamus
  2. hypothalamus produces TRH
  3. TRH signals anterior pituitary to produce TSH
  4. thyroid gland is signalled to produce thyroxine
    - if thyroxine levels are too high, negative feedback occurs
33
Q

What is TRH and TSH? What releases them?

A

TRH: thyrotropin-releasing hormone
• released by the hypothalamus to stimulate anterior pituitary

TSH - thyroid stimulating hormone (also known as thyrotropin)
• released by anterior pituitary and stimulates the thyroid gland

34
Q

What is the function of ACTH?

A
  • tropic hormone produced in the anterior pituitary

* function is to regulate the levels of steroid hormone cortisol released from the adrenal gland

BIOMOLECULES AND CELLS (32 decks)

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