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Neuro - Physiology 2: (PHY501) > Neurohormones > Flashcards

Neurohormones Flashcards

1
Q

How are neurohormones released?

A

→ DIrectly in the blood circulation

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2
Q

What is point to point communication like?

A

→ Fast and restricted

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3
Q

What are the secretory hypothalamus neurons like?

A

→ Slow but widespread

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4
Q

What are networks of interconnected neurons of the autonomic nervous system like?

A

→ Fast

→ widespread influence

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5
Q

What are diffuse modulatory systems like?

A

→ Slower and widespread

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6
Q

What are the 4 characteristics of the endocrine system?

A

→ Mediators travel within blood vessels
→ utilises chemical mediators
→ slow communication
→ long lasting effects

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7
Q

What are the 4 characteristics of the nervous system?

A

→ Signalling along nerve fibres
→ Transmission of electrical impulses
→ fast communication
→effects are short acting

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8
Q

What are neurohormones produced by?

A

→ specialised nerve cells called neurosecretory cells

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9
Q

What can neurohormones act like?

A

→ Neurotransmitters

→ autocrine or paracrine messengers

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10
Q

What are the 3 types of hormones?

A

→ Protein and peptide
→ amino acid derivatives
→ steroid hormones

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11
Q

What are the 4 features of protein and peptide hormones?

A

→ Vary considerably in size
→ Can be synthesised as large precursors prior to secretion
→ post translationally modified
→ can have multiple subunits synthesized independently and assembled

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12
Q

What are 2 features of amino acid derivative neurohormones?

A

→ Mostly tyrosine derived

→ Neurotransmitter that can also act as a hormon

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13
Q

What are 3 examples of amino acid derivative neurohormones?

A

→ adrenaline
→ noradrenaline
→ dopamine

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14
Q

Where are steroid hormones derived from?

A

→ Class of lipids derived from cholesterol

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15
Q

What are 5 examples of steroid neurohormones?

A 
→ Cortisol
→ Aldosterone
→ testosterone
→ progesterone
→ estradiol
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16
Q

What is the base of the brain called?

A

→ Hypothalamus

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17
Q

What is the hypothalamus connected to?

A

→ pituitary

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18
Q

Where do magnocellular neurons project to?

A

→ posterior pituitary

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19
Q

What hormones are secreted from the posterior pituitary?

A

→ Vasopressin

→ oxytocin

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20
Q

Where are neurohormones released in the anterior pituitary?

A

→ Portal system

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21
Q

What time frame are circadian rhythms?

A

→ 24 hour cycle

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22
Q

What time frame are pulsatile rhythms?

A

→ less than 24 hours

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23
Q

What time frame are infradian rhythms?

A

→ longer than 24 hours

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24
Q

What is an example of hormones that follow the circadian cycle?

A

→ Cortisol
→ GH
→ PRL

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25
Q

What is an example of a hormone that follows pulsatile cycles?

A

→ Gonadotrophins

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26
Q

What is an example of an infradian rhythm?

A

→ Menstrual cycle

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27
Q

Where is the pituitary?

A

→ Sella turcica

→ in the sphenoid bone

28
Q

Where are hypothalamic hormones secreted?

A

→ portal vein system

→ at the median eminence

29
Q

Describe the pathway of gonadotrophin releasing hormone?

A

→ neurons release GnRH
→ transported to the anterior hypothalamus and acts on receptors
→ Induces release of FSH and LH

30
Q

Describe the pathway of growth hormone?

A

→ Growth hormone releasing hormone is transported to the anterior pituitary
→induces release of growth hormone

31
Q

Describe the pathway of CRH?

A

→ Corticotropin releasing hormone is a peptide released to the capillary system
→ it gets transported to the anterior pituitary
→ this releases ACTH and acts on the adrenal cortex
→ induces the release of cortisol

32
Q

Describe the pathway of thyrotropin releasing hormone?

A

→ thyrotropin releasing hormone is delivered to the anterior pituitary
→ causes the release of TSH
→ TSH acts on the thyroid and induces the release of thyroxine

33
Q

Describe the pathway of vasopressin?

A

→ Magnocellular neurons release vasopressin in the posterior pituitary
→ Vasopressin acts on the kidney and has an anti-diuretic effect

34
Q

Describe the pathway of oxytocin?

A

→ Magnocellular neurons release oxytocin in the posterior pituitary
→ oxytocin acts on the uterus to induce uterine contraction
→ oxytocin acts on mammary glands to induce milk ejection

35
Q

Describe the ACTH axis to release cortisol?

A

→ Stress activates the HPA axis
→ Stress activates the hypothalamus to release corticotrophin releasing hormone (CRH)
→This acts on receptors in the anterior pituitary which releases ACTH
→ ACTH is released in the blood
→ ACTH acts on receptors in the adrenal cortex to release cortisol

36
Q

What is the effect of ACTH?

A

→ Mobilises energy for fight or flight

37
Q

Describe how cortisol release is terminated?

A

→ Cortisol induces a negative feedback effect

→ It acts on cortisol receptors in the pituitary or in the hypothalamus to inhibit CRH or ACTH

38
Q

What happens to the HPA axis during chronic stress?

A

→ Cortisol levels are increased
→ Hypersensitivity of the axis leads to high levels of basal cortisol
→ Depression and anxiety related disorders

39
Q

Describe the TSH axis?

A

→ Thyrotropin releasing hormone (TRH) from the hypothalamus stimulates the anterior pituitary to release TSH
→ TSH acts on the thyroid to increase T4/T3 secretion
→Thyroxine exerts negative feedback on the pituitary receptors

40
Q

What is the most potent thyroid hormone?

A

→ T3

41
Q

What is the effect of TSH?

A

→ Targets tissues containing a deiodinase enzyme to convert T4 to T3

42
Q

What does hyperthyroidism lead to?

A

→ Anxiety

43
Q

What does hypothyroidism lead to?

A

→ Cognitive impairments such as apathy

44
Q

Where is prolactin released from?

A

→ Lactotrophs in the anterior pituitary

45
Q

What is the relationship between dopamine and prolactin?

A

→ Dopamine is released into the bloodstream and inhibits prolactin release

46
Q

Where are vasopressin and oxytocin synthesized in?

A

→ Supraoptic and paraventricular nuclei in the hypothalamus

47
Q

What is the difference between vasopressin and oxytocin?

A

→ 2 peptides

48
Q

What is vasopressin release stimulated by?

A

→ Changes in the activity of the osmoreceptor complex in the hypothalamus

49
Q

What is the function of vasopressin?

A

→ Controls plasma osmolality by regulating water excretion

→ Stimulates vascular smooth muscle contraction in the DCT to reduce water loss and raise blood pressure

50
Q

When is oxytocin elevated?

A

→ Parturition
→ Lactation
→ Mating

51
Q

What is oxytocin released in stimulus to?

A

→ Peripheral stimuli of cervical stretch receptors and suckling at the breast

52
Q

What is the function of oxytocin?

A

→ Regulates contraction of smooth muscle
→ uterus during labour
→ contraction of vas deferens during ejaculation

53
Q

Describe the RAAS system

A

→ Kidneys release renin
→ Renin cleaves angiotensinogen from the liver to angiotensin I
→ Angiotensin I → angiotensin II in the lungs
→ Angiotensin II constricts vessels
→ It acts on the subfornical organ which gives the signal to release vasopressin from the pituitary
→ blood pressure increases

54
Q

Describe the role of oxytocin during childbirth

A

→ During labour the baby starts pushing on the uterus which stretches
→ There is stimulation of neurons that signal the magnocellular neurons to release oxytocin
→ Oxytocin acts on its receptors in the uterus to cause contractions
→ Baby moves forward which causes stretching
→ stretching causes further oxytocin release which is +ve feedback

55
Q

What makes voles monogamous?

A

→ High levels of oxytocin in the reward centres of the brain

56
Q

What does oxytocin deficiency lead to?

A

→ Antisocial behaviour

57
Q

What stimuli activate the RAAS system?

A

→ dehydration

→ low blood pressure due to blood loss

58
Q

What are the 4 receptor mechanisms?

A

→ Dimerisation pathway
→ G protein/adenylate cyclase pathway
→ DAG/IP3 pathway
→ Nuclear and steroid pathways

59
Q

How does the dimerisation pathway work?

A

→ Binding of insulin and growth hormone to cell surface receptors leads to dimerisation of receptors
→ this recruits tyrosine kinases which phosphorylates target proteins and induces biological responses

60
Q

How does the G protein pathway work?

A

→ binding of a hormone to GPCR results in conformational changes in the receptor
→ leading to GTP exchange for GDP and activation of adenylate cyclse
→Stimulation of adenylate cyclase leads to an increase in cAMP
→ cAMP activates PKA which phosphorylates target proteins to initiate gene expression

61
Q

What 3 hormones use G proteins?

A

→ TSH and ACTH

→ Oxytocin is Gq coupled

62
Q

How does the DAG/IP3 pathway work?

A

→ Oxytocin binds to GCPRS
→ stimulates phospholipase C
→ PIP2 → IP3 and DAG
→ IP3 stimulates Ca2+ release from intracellular stores
→ DAG activates PKC
→ PKC stimulates the phosphorylation of proteins and alter enzyme activities to initiate a biological response

63
Q

How do nuclear and steroid pathways work?

A

→ Steroid hormones diffuse across the plasma membrane of target cells and bind to intracellular receptors in the cytoplasm
→ The receptors function as hormone regulated transcription factors controlling gene expression

64
Q

What do nuclear receptors share?

A

→ Transcriptional activation domain
→ Zn2+ finger DNA binding domain
→ Ligand binding domain

65
Q

What are the 6 effects of a pituitary adenoma?

A 
→ loss of visual field (pressure on optic nerve) 
→ too much GH (acromegaly) 
→ Hypogonadism and infertility 
→ Hypopituitarism 
→ Hyperprolactinemia 
→ Cushing syndrome (too much ACTH)
66
Q

What are the symptoms of hypothyroidism?

A

→ cold hands
→ cold feet
→ lack of energy

Neuro - Physiology 2: (PHY501) (21 decks)

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