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Structure & Function 6 > Physiology of the Hypothalamus Pituitary Axis I&II > Flashcards

Physiology of the Hypothalamus Pituitary Axis I&II Flashcards

1
Q

What is the endocrine system?

A

it is a major regulatory system that coordinated life - sustaining responses and functions

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2
Q

what system works with the endocrine system in order to monitor and adjust physiologic activities?

A

the nervous system

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3
Q

what are neurotransmitters?

A

they are chemical messengers

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4
Q

what response does the nervous system perform?

A

short-term very specific responses to environment al stimuli

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5
Q

what does the endocrine system regulate?

A

longer-term ongoing metabolic processes throughout the body

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6
Q

what are hormones (in simple terms)?

A

chemical messengers (‘to excite’)

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7
Q

Name five pure endocrine glands:

A

pituitary
pineal
thyroid
parathyroid
adrenal

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8
Q

name 4 organs which contain endocrine cells:

A

pancreas
thymus
gonads
hypothalamus

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9
Q

what are endocrine cells?

A

they are glandular secretory cells that release hormones directly into the blood, lymphoid system or interstitial fluids

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10
Q

each hormone specificity?

A

each hormone is typically produced by a specific gland and has specific target organs

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11
Q

hormones can be divided into four classes according to their chemical structures, what are these classes?

A

amino acid derivatives
peptide and protein hormones
steroid hormones
fatty acid compounds

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12
Q

describe the chemical structure of amino acid derivative hormones?

A

these are derivatives of tyrosine
thyroid hormones and catecholamines

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13
Q

describe the chemical structure of peptide hormones:

A

chains of amino acids and they are the largest group of hormones
all pituitary hormones

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14
Q

describe the chemical structure of steroid hormones:

A

derived from cholesterol
reproductive organs, adrenal cortex, placenta

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15
Q

describe the chemical structure of fatty acid compounds, hormones:

A

derived from arachidonic acid
eicosanoids e.g. prostaglandins and leukotrienes
Coordinate cellular activities and affect enzymatic activity in ECF

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16
Q

What are diseases of endocrine glands often known as?

A

as hormones imbalances

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17
Q

treatments of diseases of endocrine glands include?

A

steroids
hormones
peptides and proteins
many other drugs
and treatments can often take a long time

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18
Q

do not confuse diseases of endocrine glands with?

A

with exocrinopathy (which represents a disease of the exocrine system

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19
Q

give examples of endocrinopathies in animals?

A

pituitary dwarfism
diabetes insipidus
hypo/hyperthyroidism
hypo/hypercalcaemia
hypo/hyperparathyroidism
diabetes mellitus
insulinoma

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20
Q

what is pituitary dwarfism?

A

secrete too little growth hormone in young animals

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21
Q

what is diabetes insipidus?

A

secrete too little antidiuretic hormone

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22
Q

what is hypo/hyperthyroidism?

A

secrete too little/too much thyroid hormone

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23
Q

what is hypo/hypercalcaemia?

A

circulating calcium too low/too high

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24
Q

what is hypo/hyperparathyroidism?

A

secrete too little/too much parathyroid hormone

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25
what is diabetes mellitus?
secrete too little insulin (or insulin resistance)
26
what is insulinoma?
tumour secreting too much insulin
27
what does the hypothalamus form?
it forms the floor of a part of the brain called the diencephalon
28
what does the thalamus form?
forms the walls of the diencephalon
29
what nerve fibres does the hypothalamus have?
it has afferent and efferent nerve fibres linking to other parts of the central nervous system
30
what does the hypothalamus serve as a link between?
between the neuro and endocrine systems
31
where does the hypothalamus receive information from?
receives info from the body about internal and external environment and co-ordinates activities of various organs and tissues via endocrine and autonomic nervous systems
32
what is the pituitary also known as?
the hypophysis
33
where is the pituitary located?
in small pocket of the sphenoid bone of the skull in the base of the braincase
34
what is the pituitary linked to the hypothalamus by?
the infundibulum
35
pituitary gland consists of how many parts, and what are these parts?
3 parts anterior lobe intermediate lobe posterior lobe
36
anterior lobe of the pituitary?
adenohypophysis - most pituitary hormones
37
intermediate lobe of the pituitary?
melanocyte stimulating factor
38
posterior lobe of the pituitary?
neurohypophysis - oxytocin and ADH
39
what is the posterior lobe of the pituitary?
it is an extension of the hypothalamus and is a part of the CNS ADH and oxytocin are released from axon terminals
40
what are the anterior and intermediate lobes of the pituitary?
these are epithelial tissue derived from the oral cavity and contain endocrine cells
41
what does the pituitary control?
the endocrine system
42
hypothalamus and pituitary working together?
form a complex and also dominant component of the endocrine system work together to control various different glands in the body in addition to having their own endocrine functions/hormone
43
what is the hypothalamic-pituitary-portal system?
release of pituitary controlled by the hypothalamus
44
blood brain barrier
protect from certain toxins floating around the body blood vessels have holes in endothelium lining - these allow nutrients to leave bloodstream into extracellular fluid and bathe cells but NO holes in blood vessels coming to brain as we can't afford risk - tightly packed cells protects potential leak of toxins so active transport systems that move nutrients from blood stream into brain
45
what two hormones does the posterior pituitary release?
ADH and oxytocin
46
ADH aka?
vasopressin
47
ADH and oxyotcin?
both are peptide hormones that are composed of nine amino acids, seven of which are conserved
48
what neurons does the posterior pituitary consist of?
consists of neurosecretory neurons with the cell bodies residing within the hypothalamus in two defined nuclei and the axons of those cells residing in the posterior pituitary where the neurohormones can be relesed
49
what are the two defined nuclei within the cell bodies of posterior pituitary function?
supraoptic nucleus paraventricular nucleus
50
ADH involved in what mechanism?
negative feedback mechanism
51
describe the negative feedback mechanism includingnADH?
hypothalamus detects decrease in blood volume and increase in osmolarity makes animal thirsty and stimulates ADH producing neurons in hypothalamus ADH released into blood which acts on the tubular cells of the collecting ducts in kidney when ADH conc high, more aquaporins are incorporated into the luminal membranes of the tubular cells so more water absorbed from collecting ducts blood volume increases + osmolarity decreases animal no longer thirsty & ADH production decreases lower ADH concentration in the blood results in fewer aquaporins and less water reabsorption - diuresis
52
what does ADH do?
regulation of water permeability of the renal distal tubules and collecting ducts - via insertion of aquaporin channels
53
what muscle does ADH cause contraction of?
of arteriolar smooth muscles
54
what are regulators of ADH secretion?q
extracellular osmolarity and extracellular fluid volume are primarily regulators of ADH secretion
55
what does water deprivation cause - ADH?
increases osmolarity of plasma and fluids bathing the brain
56
what does hyperosmolarity induce?
induces loss of intracellular water from osmoreceptors neurons in or near hypothalamus leading to release of ADH
57
what does water ingestion suppress - ADH?
supresses the firing of these osmoreceptors
58
ignoring water content, when is ADH also produced?
when there is a decrease in blood volume or blood pressure
59
what feedback mechanism is oxytocin involved in?
in positive feedback mechanism
60
what is oxytocin essential for?
uterine contractions during parturition contraction of myoepithelial cells in mammary alveoli for milk let-down
61
kitten not coming out - case 2 what do you do?
check cervix open and palpate - check animal in right orientation
62
secretion of hypophysiotropic hormones?
secretions regulated by one or more hypothalamic hypophysiotrophic hormones
63
what type of hormones are hypophysiotrophic hormones?
small peptide hormones
64
long loop feedback?
hormones released from the peripheral endocrine gland provides feedback to the pituitary or hypothalamus
65
short loop feedback?
hormones from the pituitary provides feedback to the hypothalamus
66
ultra-short feedback?
the hormones released by the endocrine organ directly provides feedback to the endocrine organ of origin
67
time period in which episodic secretions occurs over?
over the course of 24 hour period (circadian rhythms)
68
growth hormone is what type of hormone?
peptide hormone consisting of a single chain - 191 amino acids
69
growth hormone necessary for
growth
70
final outcome of growth is not ultimately determined growth factor - also depends on?
on genetic determination appropriate and adequate diet freedom from chronic disease/stressful environment normal levels of growth-influencing hormones
71
growth hormone of pituitary?
most abundant hormone produced by the anterior pituitary
72
secretion of growth hormone?
age dependant secretion
73
continued secretion growth hormone beyond growth phase means?
it plays other roles as well
74
what is control of growth hormone secretion regulated by?
by two hypothalamic-hypophysiotrophic hormones
75
GHRH?
growth hormone releasing hormone this stimulates synthesis and secretion of growth hormone
76
GHIH?
growth hormone inhibiting hormone (somatostatin) inhibits GH secretion (and other off-target effects)
77
what controls the secretion of GH?
growth hormone feedback mechanisms also control secretion of GH GH feedback onto hypothalamus to inhibit GHRH and promote GHIH - true mechanism is uncertain
78
intermediate lobe function? (fish and bird etc.)
similar origins to the anterior pituitary absent in birds regulates camo in fish, amphibians and reptiles
79
melanotropes?
these produce MSH (melanocyte stimulating hormone)
80
what does MSH scatter?
it scatters melanin granules and concentrates light reflecting particles called iridophores around the nucleus of melanocytes
81
increased MSH can result in?
in darker pigmentation but is not the primary cause of colour variation
82
MSH is structurally similar to what and what does this result in?
similar to ACTH (adrenocorticotrophic hormone) so excessive production of ACTH can also cause hyperpigmentation such as in Addison's disease
83
what controls the release of pituitary hormones?
it is controlled by the hypothalamus
84
what does the posterior lobe of the pituitary gland contain?
the posterior lobe contains nerve fibres, glial cells and blood vessels and is part of the central nervous system
85
why is the posterior lobe part of the central nervous system?
as it is connected to the hypothalamus via axons
86
what are the anterior and intermediate lobes of the pituitary connected to the hypothalamus via?
via the hypothalamic-pituitary-portal system
87
describe features of the hypothalamic pituitary portal system?
it has two capillary beds in series hypothalamic neuroendocrine cells can release neurohormones directly into the first capillary bed neurohormones then travel through portal vessels of infundibulum to second capillary bed which surrounds the endocrine cells of the anterior and intermediate lobes
88
what system is the hypothalamic-pituitary-portal system similar to?
similar to hepatic portal system
89
what does the posterior pituitary consist of/
consists of neurosecretory neurons with the cell bodies that secrete ADH and oxytocin residing within the hypothalamus in two defined nuclei: supraoptic and paraventricular nuclei
90
hypothalamic-pituitary-portal system:
arterial blood coming in to feed the brain releasing hormones are released into veins that are coming out of brain + into anterior pituitary the blood supply for the anterior pituitary cells is coming from veins the anterior pituitary cells are releasing their hormones into veins that go around the body and into glands system is like veins going into veins
91
what is a portal system?
veins into veins
92
NOT RELEVANT TO THIS BUT: what is hepatic portal system?
blood going into GI tract absorbs all nutrients from GI tract Then drains into liver and then veins leave liver and go towards the heart So you have a venous system going into a venous system before going to heart and finding way into artery before leaving heart
93
where do the cells that secrete oxytocin sit in the brain?
in the supraoptic nucleus
94
where do the cells that secrete ADH sit in the brain?
in the paraventricular nucleus
95
where do the axons of the cells secreting oxytocin and ADH in the brain reside?
in the posterior pituitary where the neurohormones can be released
96

Structure & Function 6 (19 decks)

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