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Metabolism > Session 7 > Flashcards

Session 7 Flashcards

0
Q

What types of feedback are there?

A
  • Negative

- Positive

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1
Q

What are the components of control systems?

A
  • Communication
  • Control centre
  • Receptor
  • Effector
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2
Q

What is a biological rhythm?

A
  • Set point can vary over time instead of being a fixed value
  • Cortisol levels, menstrual cycle
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3
Q

What does the body water consist of?

A
  • Intracellular fluid
  • Extracellular fluid
  • Blood plasma
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4
Q

What is osmalality and Na+ concentration monitored by?

A
  • Osmoreceptors in hypothalamus
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5
Q

What happens if osmolality of blood plasma increases?

A
  • Antidiuretic hormone is released from the posterior pituitary gland
  • Increased reabsorption of water from urine in collecting ducts of kidney
  • Osmolality of blood plasma decreases
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6
Q

What are endocrine hormones?

A
  • Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
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7
Q

What is the hierarchy of control of glands?

A
  • Hypothalamus
  • Anterior pituitary gland
  • Endocrine glands
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8
Q

What are the classes of hormone?

A
  • Peptide/polypeptide hormones
  • Glycoprotein hormones
  • Amino Acid derivatives
  • Steroids
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9
Q

What are peptide/polypeptide hormones?

A
  • Short or long chains of amino acids

- Eg insulin, glucagon, growth hormone, placental lactogen

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10
Q

What are glycoprotein hormones?

A
  • Large protein molecules with carbohydrate side chains

- Eg anterior pituitary hormones: luteinizing hormone, follicle stimulating hormone, thyroid stimulating hormone

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11
Q

What are amino acid derivative hormones?

A
  • Small molecules synthesised from amino acids

- eg adrenaline, thyroid hormones (thyroxine)

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12
Q

What are steroids?

A
  • Derived from cholesterol

- Eg cortisol, aldosterone, testosterone, oestrogen

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13
Q

How are hormones transported?

A
  • Hydrophilic hormones (peptide; glycoprotein and adrenaline): in bloodstream dissolved in blood plasma
  • Hydrophobic (steroid; thyroid): need specialised transported proteins
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14
Q

What form of the hormone is biologically active?

A
  • Free form (unbound to protein)
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15
Q

What is the role of carrier proteins?

A
  • Increase solubility of hormone in plasma
  • Increase half-life
  • Readily accessible reserve
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16
Q

How do hormones produce a response?

A
  • Bind to receptors in or on target cells
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17
Q

What does the magnitude of response to a hormone depend on?

A
  • Concentration of active hormone at target tissue
  • Receptor number
  • Affinity of hormone for receptor
  • Degree of signal amplification (enzymes involved - cascade)
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18
Q

What are the steps involved in hormone action?

A
  • If a hormone cannot cross membrane it binds to a receptor on the cell surface
  • Activates a Second messenger
  • Second internal messenger exerts metabolic effects eg modifying enzyme action
19
Q

Which hormones can cross cell surface membrane?

A
  • Steroid hormones

- Instead bind to receptors inside cell (cytoplasmic/nuclear)

20
Q

What hormones are produced by the anterior pituitary gland and what do they do?

A
  • Thyroid stimulating hormone (affects thyroid gland)
  • Adrenocorticotrophic hormone (affects adrenal gland)
  • Leuteinizing hormone (affects ovary and testes function)
  • Follicle stimulating hormone (affects ovary and testes function)
  • Growth hormone (affects metabolism)
  • Prolactin (affects breast development and milk production)
21
Q

What are tropic hormones?

A
  • Hormones that control the secretion of others
22
Q

Which hormones released by the anterior pituitary gland are tropic hormones?

A
  • Thyroid stimulating hormone
  • Adrenocorticotrophic hormone
  • Leuteinizing hormone
  • Follicle stimulating hormone
23
Q

How is the secretion of tropic hormones controlled?

A
  • Negative feedback: when the hormone that they control increases in concentration, the tropic hormone secretion reduces and when the hormone they control decreases in concentration the tropic hormone secretion increases
  • Eg when thyroid hormone is high, this negatively feedsback and thyroid stimulating hormone secretion decreases
  • Also releasing and inhibiting hormones
24
Q

What are releasing and inhibiting hormones?

A
  • From nerve cells in hypothalamus to anterior pituitary gland via hypophyseal portal vessels (specialised blood vessels)
  • How the brain controls hormone secretion
25
Q

Give examples of releasing and inhibiting hormones

A
  • Thyrotrophin releasing hormone: stimulates thyroid stimulating hormone release
  • Corticotrophin releasing hormone: stimulates Adrenocorticotrophic hormone release
  • Somatotrophin releasing hormone: stimulates growth hormone release
  • Somatostatin: inhibits growth hormone release
26
Q

How are hormones inactivated?

A
  • Steroid hormones: small change in chemical structure that increases water solubility; can be exerted from the body in urine or via bile
  • Protein hormones: more extensive chemical changes; are degraded to amino acids that are refused
27
Q

Where does hormone inactivation take place?

A
  • Kidneys

- Liver

28
Q

What are the components of the hypothalamic-pituitary-adrenal axis?

A
  • Hypothalamus (releases corticotrophin releasing factor)
  • Anterior pituitary gland (releases adrenocorticotrophic hormone)
  • Adrenal cortex/zone fasciculata (releases cortisol)
29
Q

How is the hypothalamus-pituitary-adrenal axis controlled?

A
  • Negative feedback of Adrenocorticotrophic hormone on Corticotrophin releasing hormone release
  • Negative feedback of cortisol on Adrenocorticotrophic hormone release and corticotrophin releasing hormone release
30
Q

Where is appetite controlled?

A
  • Satiety centre located in arcuate nucleus in the hypothalamus
31
Q

What types of neurones does the arcuate nucleus contain?

A
  • Primary: senses metabolite levels (glucose and fatty acids) in blood; responds to hormones
  • Secondary: synthesises input from primary neurones; co-ordinates a response via vagus nerve
32
Q

How can primary neurones be sub-divided?

A
  • Excitatory: stimulates appetite via release of peptides neuropeptide Y (NPY) and agouti-related peptide (AgRP)
  • Inhibitory: suppress appetite by release of prohormone pro-opiomelanocortin (POMC)
33
Q

What can POMC be cleaved into?

A
  • Several peptide hormones:
    ~ B-endorphin (reward system - feelings of euphoria/tiredness)
    ~ adrenocorticotrophic hormone (ACTH)
    ~ a-melanocyte stimulating hormone (a-MSH) - suppresses appetite
34
Q

What hormones feedback from the gut to the hypothalamus?

A
  • Ghrelin
  • PYY
  • Leptin
  • Insulin
  • Amylin
35
Q

What is the structure and function of Ghrelin?

A
  • Peptide hormone
  • Released from stomach walk when empty
  • Stimulates excitatory neurones in arcuate nucleus
  • Stimulates appetite
  • Filing of stomach inhibits Ghrelin release
36
Q

What is the function of PYY?

A
  • Peptide hormone
  • Released from wall of small intestine
  • Suppresses appetite
37
Q

What is the function of Leptin?

A
  • Peptide hormone
  • Released from adipocytes
  • Stimulates inhibitory neurones in arcuate nucleus
  • Suppresses appetite
  • Induces expression of uncoupling proteins in mitochondria so energy is dissipated as heat
38
Q

What is the function of insulin?

A
  • Suppresses appetite

- Same mechanism as Leptin but less important

39
Q

What is the function of Amylin?

A
  • Peptide hormone
  • Secreted from B cells in pancreas
  • Suppresses appetite
40
Q

What are the pattern of symptoms for metabolic syndrome?

A
  • Insulin resistance
  • Dyslipidaemia
  • Glucose intolerance
  • Hypertension
  • Central adiposity
41
Q

What is the WHO criteria for metabolic syndrome?

A
  • Waist hip ratio: >0.9 men; >0.85 women
  • BMI: >30 kg/m2
  • Blood pressure: >140/90 mmHg
  • Triglycerides: >1.7 mM
  • HDL: 7.8 mM
  • Glucose uptake in lowest quartile
42
Q

What is insulin resistance associated with?

A
  • Dyslipidaemia (high VLDL; high LDL; low HDL lol)
  • is highly atherogenic
  • Increased risk of hypertension
43
Q

What is the Barker hypothesis?

A
  • Studies showed that some adult diseases (coronary heart disease, hypertension, type 2 diabetes) are related to low birth weight
  • Suggests that the experience of the foetus in utero during development somehow determines the future health of the individual
44
Q

What is fetal programming?

A
  • Fetus adapts to conditions in utero eg supply of nutrients
  • Biochemical adaptations become programmed in, predisposing to adult disease conditions
  • Programming involves switching genes on and off at critical times during fetal development
45
Q

What is the definition of epigenetics?

A
  • An epigenetic trait is a stably inherited phenotype resulting from changes in a chromosome without alterations in the DNA sequence
46
Q

How is it possible for low birth weight to passed on through several generations?

A
  • Epigenetics: adaptations in the phenotype can be passed down (without changes in DNA)
  • Mechanism involves methylation of DNA at crucial positions and changes in histone structure, causes suppression of gene transcription

Metabolism (11 decks)

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