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Anatomy & Physiology 1 > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

What is the difference between endocrine and exocrine glands?

A

Exocrine glands have ducts for delivery of substances to membrane surface and produce nonhormonal substances (e.g. sweat, saliva), endocrine glands are ductless and produce hormones.

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2
Q

What are hormones?

A

Long distance chemical signals that travel in blood or lymph

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3
Q

What are the two main classes of hormones?

A

Amino acid based hormones and steroids

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4
Q

What are the two major mechanisms of hormone action depending on chemical nature?

A

Water soluble hormones (peptides) and lipid soluble hormones.

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5
Q

Which type of hormone can move freely through the cell membrane?

A

Lipid-soluble hormones

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6
Q

What are the three factors that target cell activation depend on?

A

Blood concentrations of the hormone, relative number of receptors on/in target cell, and affinity of binding between receptor and hormone

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7
Q

What is up-regulation?

A

Target cells form more receptors in response to hormone

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8
Q

What is down-regulation?

A

Target cells lose receptors in response to the hormone

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9
Q

What are the two ways that hormones can circulate through blood?

A

Free or bound (attached to protein carrier)

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10
Q

What are the three ways hormones may interact with each other?

A

Permissiveness, synergism, antagonism

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11
Q

What is permissiveness?

A

One hormone cannot exert its effects fully without the presence of another hormone.

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12
Q

What is synergism?

A

Interaction of more than one hormone produces the same effects at the target cell and their combine effects are amplified (yield result more than additive).

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13
Q

What is antagonism?

A

One or more hormones oppose the action of another hormone (i.e. glucagon and insulin)

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14
Q

How are blood concentrations of hormones controlled?

A

Negative feedback systems

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15
Q

What are the three stimuli that trigger hormone synthesis/release?

A

Humoral, neural, hormonal

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16
Q

What are humoral stimuli?

A

Changing blood concentrations of ions and nutrients directly stimulates hormone secretion

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17
Q

What are neural stimuli?

A

Nerve fibers stimulate hormone release

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18
Q

What are hormonal stimuli?

A

Hormones stimulate other endocrine organs to release their hormones (trophic effect)

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19
Q

What are the two lobes of the pituitary gland called?

A

Anterior (adenohypophysis) made of glandular tissue and Posterior (neurohypophysis) made of neural tissue

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20
Q

What are the six hormones released by the anterior pituitary?

A

Thyroid stimulating, adrenocorticotropic, follicle stimulating, luteinising, growth, prolactin

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21
Q

What is the role of thyroid stimulating hormone (TSH)?

A

Stimulates normal development and secretory activity of the thyroid

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22
Q

What is the role of adrenocorticotropic hormone (ACTH)?

A

Stimulates adrenal cortex to release corticosteroids

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23
Q

What is the role of gonadotropins (FSH and LH)

A

Stimulates gamete (egg/sperm) production and promotes gonadal hormone production

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24
Q

What is the role of growth hormone (GH)?

A

Promotes protein synthesis (skeletal muscle) and encourages use of fats for fuel

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25
Q

What is the role of prolactin (PRL)?

A

Stimulates milk production

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26
Q

What two hormones does the posterior pituitary store?

A

Antidiuretic hormone (ADH) and oxytocin, released in response to nerve impulses

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27
Q

What is the role of antidiuretic hormone (ADH)?

A

Responds to changes in solute concentration of the blood. If solute concentration is high, inhibits urine formation to minimise loss of fluid. If solute concentration is low, hormone NOT released to allow water loss

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28
Q

How does alcohol affect antidiuretic hormone (ADH)?

A

Inhibits the release of antidiuretic hormone (ADH) and causes copious urine output, even when the body is dehydrated.

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29
Q

What is the role of oxytocin?

A

Stimulates uterine contractions during childbirth, triggers milk ejection, sexual arousal/orgasm in males and females

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30
Q

What are the two hormones involved with breast milk and what are their roles?

A

Prolactin is involved in the production of milk, oxytocin is responsible for triggering the ejection of milk.

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31
Q

What are the functions of the endocrine system?

A

Acts with the nervous system to coordinator and integrate activity of body cells, influences metabolic activities. Responses are slower but tend to last longer than those of nervous system

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32
Q

Which type of hormone cannot penetrate the cell membrane?

A

Water soluble (peptide) hormones

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33
Q

How are hormones removed from the blood?

A

Degrading enzymes (kidneys/liver) and half-life

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34
Q

What is half-life?

A

The time for hormone plasma concentration to decrease by half (ranges from seconds to a week)

35
Q

Where is iodide located in the thyroid gland?

A

Cytoplasm of follicular cells

36
Q

Aside from the sympathetic nervous system, what is the other primary mediator of acute stress?

A

The adrenal medulla

37
Q

What is the major difference between neurotransmitters and hormones?

A

Hormones reach their destination via the blood

38
Q

Why do second messenger-activating hormones circulate in minute quantities?

A

Small concentrations of hormone can activate many intracellular signals via amplification

39
Q

What are the two related compounds of thyroid hormone (TH)?

A

T4 (thyroxine) and T3 (triiodothyronine)

40
Q

What does thyroid hormone play a role in?

A
  • Maintaining blood pressure
  • Regulating tissue development and growth
  • Development and maturation of skeletal and nervous systems
  • Reproductive capabilities
41
Q

How is the synthesis and release of thyroid hormone (TH) controlled?

A
  1. Hypothalamus produces TRH
  2. Anterior pituitary produces TSH
  3. Thyroid secretes its hormones

Thyroid hormones levels provide negative feedback to inhibit release of TRH and TSH.

42
Q

What do the numbers represent in T3 and T4?

A

The number of iodine atoms attached to the molecule (3 or 4 respectively)

43
Q

Which thyroid hormones (TH) compound is more reactive than the other?

A

T3, ten times more reactive than T4

44
Q

What hormone is primarily responsible for decreasing calcium blood concentration?

A

Calcitonin

45
Q

What are the main differences between hormonal and neural controls of body functioning?

A

Neural controls initiate responses more rapidly but for a shorter duration and short distance. Neural controls are delivered by action potentials/neurotransmitters at specific locations. Hormonal responses are slow and long distance. They can affect anywhere blood reaches.

46
Q

What are the major endocrine organs?

A

Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus, adrenal glands, pancreas, gonads (testes & ovaries)

47
Q

What are paracrines?

A

Short distance chemical signals that act locally (within same tissues) but affect cell types other than those releasing the paracrine chemicals (i.e. one group of pancreatic cells releasing chemicals that affect a different group of pancreatic cells).

48
Q

What are autocrines?

A

Short distance chemical signals that exert their effects on the same cells that secrete them (i.e. certain prostaglandins released by smooth muscle cells cause those same cells to contract)

49
Q

What is endocrinology?

A

The scientific study of hormones and the endocrine organs.

50
Q

What type of organ is the hypothalamus? Why?

A

Neuroendocrine organ, it has neural functions and also produces and secretes hormones.

51
Q

Describe the cyclic AMP second-messenger mechanism of water-soluble hormones.

A
  1. Hormone (first messenger) binds receptor.
  2. Receptor activates G protein.
  3. G protein activates enzyme adenylate cyclase.
  4. Adenylate cyclase converts ATP to cAMP (second messenger).
  5. cAMP activates protein kinases.
52
Q

In cyclic AMP signalling, how is the G protein similar to a light switch?

A

It is ‘off’ when GDP is bound to it, and ‘on’ when GTP is bound (reaction continues to trigger target cell response).

53
Q

Describe the direct gene activation mechanism of lipid-soluble hormones.

A
  1. Steroid hormone diffuses through plasma membrane and binds to intracellular receptor.
  2. The receptor-hormone complex enters the nucleus.
  3. The receptor-hormone complex binds a specific DNA region.
  4. Binding initiates transcription of the gene to mRNA.
  5. The mRNA directs protein synthesis.
54
Q

Describe the synthesis of thyroid hormone (TH).

A
  1. Thyroglobulin is synthesised and discharged into the follicle lumen.
  2. Iodide (I-) is trapped (actively transported in).
  3. Iodide is oxidised to iodine.
  4. Iodine is attached to tyrosine in colloid, forming DIT and MIT.
  5. Iodinated tyrosines are linked together to form T3 and T4.
  6. Thyroglobulin colloid is endocytosed and combined with a lysosome.
  7. Lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into bloodstream.
55
Q

Which hormone is primarily responsible for controlling calcium balance in the blood?

A

Parathyroid hormone (PTH)

56
Q

What are the three layers of the adrenal cortex?

A

Zona glomerulosa (outer layer), zona fasciculata (middle layer), zona reticularis (innermost layer)

57
Q

What type of hormones does the zona glomerulosa produce?

A

Mineralocorticoids

58
Q

What type of hormones does the zona fasciculata produce?

A

Glucocorticoids

59
Q

What type of hormones does the zona reitularis produce?

A

Gonadocorticoids (sex hormones)

60
Q

What is the primary function of mineralocorticoids?

A

Regulating electrolyte (mineral salt) concentrations in extracellular fluids, particularly Na+ and K+

61
Q

What is the most potent mineralocorticoid?

A

Aldosterone, accounting for more than 95% of mineralocorticoids produced. Reduces excretion of Na+ from the body by stimulating Na+ reabsorption and causes K+ secretion into kidney tubules for elimination from the body.

62
Q

What are the primary functions of glucocorticoids?

A

Influence energy metabolism of most body cells, help us resist stressors and keep blood glucose levels fairly constant to maintain blood pressure.

63
Q

What is the most significant glucocorticoid?

A

Cortisol

64
Q

What are androgens?

A

Male sex hormones

65
Q

What are most gonadocorticoids secreted by the adrenal cortex?

A

Weak androgens, most of which are converted in tissue cells to more potent male hormones (i.e. testosterone), and some converted to estrogens.

66
Q

What hormones are produced and stored in the adrenal medulla? What are their ratios?

A

Epinephrine (adrenaline) 80% and norepinephrine (noradrenaline) 20%

67
Q

What are the main effects of adrenaline (epinephrine)?

A

Potent stimulator of metabolic activies and dilator of small airways (bronchioles).

68
Q

What are the main effects of noradrenaline (norepinephrine)?

A

Peripheral vasoconstriction (effects blood pressure)

69
Q

Explain how the short-term stress response works.

A
  1. Action potentials triggered by the hypothalamus in response to stressors activate sympathetic nervous system.
  2. Action potentials travel along preganglionic sympathetic axons to the adrenal medulla.
  3. Adrenal medulla secretes epinephrine (80%) and norepinephrine (20%).
  4. Epinephrine and norepinephrine reinforce otrher sympathetic responses to ready body for exertion (fight or flight).
70
Q

Explain how the long-term stress response works.

A
  1. Stressors cause hypothalamic neurons to release corticotropin-releasing hormone (CRH).
  2. CRH travels via portal system of blood vessels to anterior pituitary.
  3. Anterior pituitary cells (corticotophs) releas adrenocorticotopic hormone (ACTH).
  4. ACTH travels in blood to adrenal cortex.
  5. Adrenal cortex synthesises and releases glucocorticoids (i.e. cortistol) and some mineralocorticoids (i.e. aldosterone).
71
Q

What is the main secretory product of the pineal gland?

A

Melatonin

72
Q

What is the main effect of melatonin?

A

Day/night cycles (highest at night to make us drowsy, lowest at noon).

73
Q

Which organ has both exocrine and endocrine cells?

A

Pancreas

74
Q

What is the function of the exocrine pancreatic cells?

A

Produces an enzyme rich juice for digestion

75
Q

What is the function of the endocrine pancreatic cells?

A

Alpha cells produce glucagon (hyperglycaemic hormone) and beta cells produce insulin (hypoglycaemic hormone)

76
Q

What are the main effects of glucagon secretion?

A

Targets liver to break down glycogen to glucose, synthesis of glucose from lactic acid and non-carbohydrates, release of glucose to blood.

77
Q

What is glycogenolysis?

A

Breakdown of glycogen to glucose

78
Q

What is gluconeogenesis?

A

Synthesis of glucose from lactic acid and from non-carbohydrate molecules

79
Q

What the three ways insulin lowers blood glucose?

A

Enhances transport of glucose into body cells (especially fat and muscle), inhibits breakdown of glycogen to glucose, inhibits conversion of amino acids or fats to glucose.

80
Q

What are the two most important hormones produced by the ovaries?

A

Estrogens and progesterone

81
Q

What are estrogens and progesterone responsible for?

A

Maturation of female reproductive organs, appearance of female secondary sex characteristics, breast development and cyclic changes in uterine mucosa (menstrual cycle)

82
Q

What is the placenta and what hormones does it secrete?

A

The placenta is a temporary endocrine organ that sustains the fetus during pregnancy. It secretes estrogens, progersterone and human chorionic gonadotropin (hCG).

83
Q

What are the main effects of testosterone, the primary hormone produces in the testes?

A

Initiates maturation of male reproductive organs, appearance of secondary sex characteristics and sex drive, necessary for normal sperm production, maintains reproductive organs in functional state.

Anatomy & Physiology 1 (2 decks)

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