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the endocrine system Flashcards

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1
Q

what does the nervous and endocrine system do?

A

coordinates all of the body systems
-the nervous system through the action of neurons and the neurotransmitters they secrete
-the endocrine system uses hormones produced by endocrine structures to produce their effects

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2
Q

what do endocrine glands do?

A

secrete their contents directly into the blood

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3
Q

what are some examples of endocrine glands?

A

-pituitary
-thryoid
-parathyroid
-adrenal
-pineal

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4
Q

what do exocrine glands do?

A

secrete their contents into a lumen or duct

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5
Q

give examples of what exocrine glands secrete…

A

-sudoriferous (sweat)
-sebaceous (oil)
-mucous
-digestive glands

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6
Q

what is the general function of hormones?

A

-help to regulate different functions
-growth and development
-reproduction
-establish circadian rhythms

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7
Q

what are examples of the functions hormones help to regulate?

A

-extracellular fluid homeostasis
-metabolism
-muscle contraction
-glandular secretion
-immune functions

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8
Q

what does the endocrine consist of?

A

endocrine glands and hormone secreting cells

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9
Q

what are the two types of local hormones?

A

-autocrine hormones
-paracrine hormones

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10
Q

what are autocrine hormones?

A

-hormones that are secreted and bind to the same cells
-e.g interleukin-2 (IL-2) released by helper T cells, stimulates the same cell to proliferate generating more helper T cells, secreting more IL-2 and strengthen the immune response.

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11
Q

what are paracrine hormones?

A

-hormones that are secreted into the interstitial fluid and act on nearby cells e.g gas NO-released from endothelial cells to cause relaxation of nearby smooth muscle cells inducing vasodilation

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12
Q

what are endocrine (circulating) hormones?

A

-hormones that are secreted into the interstitial fluid then absorbed into the blood stream to be carried systemically to any cell that displays the appropriate type of receptor
-various cells respond differently to the same hormone

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13
Q

give an example of how an endocrine circulating hormone works.

A

-insulin which stimulates the secretion of glycogen in liver cells but the synthesis of triglycerides in adipose cells

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14
Q

what do lipid soluble hormones do?

A

bind to receptors in the cytoplasm or nucleus of a cell

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15
Q

what are the three different types of lipid soluble hormones?

A

-Steroid hormones-inc aldosterone,cortisol,testosterone,oestrogen
-Thyroid hormones-T3 (triiodothyronine) T4 (thyroxine)
-Gases-Nitric oxide-which is both a hormone and neurotransmitter

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16
Q

what is the action of lipid soluble steroid hormones?

A

to transport protein functions and:
-Increase solubility in blood
-Slow rate of hormone loss in the urine
-Provide a ready reserve of hormone

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17
Q

what do water soluble hormones do?

A

-they bind to the receptors on the plasma membrane of a cell

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18
Q

what are the three different types of water soluble hormones?

A

-amine hormones
-peptide hormones/protein hormones
-eicosanoid hormones

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19
Q

what are the different amine hormones?

A

-Adrenaline
-Noradrenaline
-dopamine (tyrosine),
-histamine (histidine),
-seratonin and melatonin (tryptophan

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20
Q

what are the different peptide hormones/protein hormones?

A

-Amino acid polymers 3-49 aa/50-200 aa
-Peptide-oxytocin,antidiuretic hormone
-Protein-human growth hormone,insulin

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21
Q

what are eicosanoid hormones?

A

-they are derived from arachidonic acid/membrane lipids
-they can be prostaglandins and leukotrienes
-local hormones are secreted by all cells except RBC

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22
Q

what are the actions of water soluble hormones?

A

-some hormones act via increasing cAMP
-some hormones act via decreased cAMP
-there is also alternative second messengers

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23
Q

which water soluble hormones act via increasing cAMP?

A

-Antidiuretic hormone (ADH)
-Thyroid stimulating hormone (TSH)
-Adrenocorticotropic hormone (ACTH)
-adrenaline/epinephrine

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24
Q

which water soluble hormone acts via decreasing cAMP?

A

-growth hormone inhibiting hormone (GHIH)

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25
what are the hormones that are alternative second messengers
-Calcium ions -Cyclic guanosine monophosphate (cGMP) -inositol triphosphate (IP3) -Diacylglycerol (DAG)
26
what does the responsiveness of a target cell depend on?
-hormone concentration in blood -the number of hormone receptors on the target cells -influence of other hormones
27
what are the three different effects on hormones?
-permissive effect -synergistic effect -antagonist effect
28
what is the permissive effect ?
-it is the effects that requires recent or simultaneous exposure to second hormones and this can increase the number of receptors for the other hormone or the synthesis of an enzymes required for the other hormones actions
29
what is an example of a permissive effect?
-adrenaline stimulation of lipolysis which is much more powerful in the presence of thyroid hormones
30
what is the synergistic effect?
-two hormones have greater impact than individually
31
what is an effective of a synergistic effect?
-oocyte development which requires action of PSG and oestrogen, neither is sufficient alone
32
what is the antagonistic effect?
-where two hormones have opposing actions
33
what is an example of an antagonistic effect?
-insulin which promotes the synthesis of glycogen and glucagon which stimulates the breakdown go glycogen on liver cells
34
what is hormone secretion regulated by?
-signals from the nervous system -chemical changes in the blood -other hormones
35
what are the two systems hormones work via?
-negative feedback -positive feedback
36
give an example of the negative feedback control of hormone secretion...
-Blood Ca2+ level is controlled by the parathyroid hormone (PTH). -Low blood Ca2+ stimulates the parathyroid glands to release PTH=PTH action increases Ca2+ levels. -If the Ca2+ levels get too high, PTH production ceases and thyroid gland secretes calcitonin (CT) to lower the Ca2+ levels.
37
give an example of a positive feedback of hormone secretion...
during childbirth where the hormone oxytocin stimulates contraction of the uterus -uterine contraction in turn stimulates more oxytocin release
38
what is the hypothalamus?
-major link between the nervous and endocrine systems -controls the pituitary gland
39
what is the pituitary gland?
-pea shaped structure that secretes 7 hormones -there are two anatomically and functionally distinct portions -it is regulated by the hypothalamus -there is the anterior pituitary
40
how is the anterior pituitary stimulated and suppressed?
-stimulated=releasing hormones from the hypothalamus -suppressed=inhibiting hormones of the hypothalamus
41
what hormones are related by the anterior pituitary?
-human growth hormone (hGH) aka somatotropin -thyroid stimulating hormone (TSH) -follicle stimulating hormone (FSH) -luteinizing hormone -prolacin -adrenocorticotropic hormone (ACTH) aka corticotropin -melanocyte-stimulating hormone (MSH)
42
what does hGh do?
-stimulates liver, muscle,cartilaage,bone and other tissues to synthesise and secrete insulin like growth factors (IGFs) which promote the growth of body cells, protein synthesis, tissue repair ,lipolysis and the elevation of blood glucose conc
43
what does TSH do?
-stimulates synthesis and secretion of thyroid hormones by thyroid glands
44
what does FSH do?
-in females it initiates the development of oocytes and induces ovarian secretion of oestrogen -in males,it stimulates the testes to produce sperm
45
what does LH do?
-in females it stimulates the secretion of oestrogen and progesterone,ovulation and formation of the corpus luteum -in makes it stimulates th testes to produce testosterone
46
what does prolactin (PRL) do?
-together with other hormones, promotes milk production by mammary glands
47
what does ACTH do?
-stimulate secretion of glucocorticoids (mainly cortisol) by adrenal cortex
48
what does MSH do?
-its exact role is unknown bit it may influence brain activity, when present in excess it can cause darkening of the skin
49
what are the target tissues of each hormone the anterior pituitary stimulates?
-hGH=liver and other tissues -TSH=thyroid glands -FSH-ovaries,testes -LH-ovaries,testes -prolactin-mammary glands -ACTH-adrenal cortex -MSH-brain
50
what does the posterior pituitary do?
-stores and releases the hormones oxytocin and ADH -it does not synthesise hormones
51
what are the actions of oxytocin?
-stimulates contraction of smooth muscle cells of the uterus during childbirth - stimulates contraction of myoepithelial cells in mammary glands to cause milk ejection
52
what is the action of ADH?
-conserves body water by decreasing urine volume, decreases water loss through perspiration, raises blood pressure by constricting arterioles
53
how is oxytocin secreted?
-by neurosecretory cells of the hypothalamus in response to uterine distention and stimulation of nipples
54
how is ADH secreted?
-by neurosecretory cells of the hypothalamus in response to elevated blood osmotic pressure, dehydration,loss of blood volume, pain or stress
55
what are inhibitors of ADH?
-low blood pressure -high blood volume -alcohol
56
what are the target tissues of oxytocin and antidiuretic hormone?
-oxytocin=uterus,mammary glands -ADH-kidneys,sudoriferous (sweat) glands, arterioles
57
homeostatic action of ADH blurt
58
what are pineal glands?
-small endocrine glands attached to the roof of the third ventricle
59
what do pineal glands do?
-secrete the hormone melatonin which contributes to maintaining the biological (seasonal and daily cycles) -more melatonin is secreted in darkness and the pineal gland is very developed in animals
60
what is a thyroid gland?
-butterfly shaped gland located inferior to the larynx and anterior to the trachea
61
what does the thyroid gland do?
-together with hGH and insulin, the thyroid hormone accelerates body growth, particularly the growth of the nervous and skeletal systems
62
what are the hormones that the thyroid gland secretes, state their source?
-T3 (triiodothyronine) and T4 (thyroxine) or thyroid hormones from follicular cells -calcitonin (CT) from parafollicular cells
63
what is the action of T3 and T4?
-increase basal metabolic rate -stimulates synthesis of proteins -increases the use of glucose and fatty acids for ATP production -increase lipolysis -enhances cholesterol secretion -accelerates body growth and the development of the nervous system
64
what is the action of calcitonin?
-lowers blood levels of Ca2+ and HPO4 2- by inhibiting bone resorption by osteoclasts and by accelerating uptake of calcium and phosphates into bone extracellular matrix
65
what is the control of secretion of calcitonin?
-high blood Ca2+ level stimulate secretion, low blood Ca2+ levels inhibit secretion
66
what is the control of secretion of T3 and T4?
-secretion is increased by thyrotropin-releasing hormone (TRH) which stimulates the release of thyroid-stimulating hormone (TSH) in response to low thyroid
67
what is the general actions of thyroid hormones?
-increase basal metabolic rate -stimulate synthesis if Na+/K+ ATPase -increase body temp (calorigenic effect) -stimulate protein synthesis -increase the use of glucose and fatty acids for ATP production -stimulate lipolysis -enhance some actions of catecholamines -regulate development and growth of nervous tissue and bones
68
what are parathyroid glands?
two pairs of small, round masses of tissue attached to the posterior surface of the lateral lobes of the thyroid gland
69
what is the hormone produced by parathyroid glands and state the source?
-parathyroid hormone (PTH) -the source is chief cells
70
what is the control of secretion of parathyroid hormone?
-low blood Ca2+ levels stimulate its secretion and high blood Ca2+ levels inhibit its secretion
71
what is the action of the parathyroid gland?
-it increases blood Ca2+ and Mg2+ levels and decreases blood HPO4 2- levels, it increase bone resorption by osteoclasts -increases Ca2+ reabsorption and HPO4 2- excretion by kidneys -it promotes formation of caltricol (active form of vitamin D) which increases the rate of dietary Ca2+ and Mg2+ absorption
72
how are the adrenal glands?
-there are two adrenal glands, one superior to each kidney (suprarenal glands)
73
what are the two distinct regions of the adrenal gland?
-the adrenal cortex=contains steroid hormones like cortisol -adrenal medulla=secretes catecholamines like adrenaline
74
what are the adrenal cortex hormones and their source?
-mineralocorticoids (mainly aldosterone) from zone glomerulosa cells -glucocorticoids (mainly cortisol) from zone fasciculate cells -androgen (mainly DHEA) from zone reticularis cells
75
how is mineralocorticoids secreted?
-increased blood K+ level and angiotensin II stimulates its secretion
75
how is glucorticoids and androgens secreted?
-glucocorticoids-ACTH stimulates release,corticotropin releasing hormone (CRH) promotes ACTH secretion in response to stress and low blood levels of glucocorticoids androgens-ACTH stimulates secretion
76
what do mineralocorticoids do?
increase blood levels of Na+ and water and decrease the blood levels of K+
77
what do glucocorticoids do?
increase protein break down (except in the liver),they stimulate gluconeohenesis and lipolysis and provide resistance to stress,dampen inflammation and depress immune responses
78
what do androgens do?
assist in the early growth of axillary and pubic hair in both sexes,in females it contributes to libido and are a source of oestrogen after menopause
79
what are the adrenal medulla hormones?
epinephrine and norepinephrine from chromaffin cells
80
how are the adrenal medulla hormones secreted?
its secretion is stimulated by sympathetic preganglionic neurons when they release acetylcholine
81
what do the adrenal medulla hormones do?
enhance the effects of sympathetic division of the autonomic nervous system (ANS) during stress
82
what is the pancreas?
-an endocrine system tissue that is located posterior and inferior to the stomach -it is both an endocrine and exocrine gland
83
what are the different pancreatic hormones and their source?
-glucagon-from alpha cells of pancreatic islets -insulin from beta cells of pancreatic islets -somatostatin from delta cells of pancreatic islets -pancreatic polypeptide from Fcells of pancreatic islets
84
how is glucagon secreted?
-by decreased blood levels of glucose,exercise,protein meals
85
what inhibits the secretion of glucagon?
-somatostatin and insulin
86
how is insulin secreted?
-by increase blood levels of glucose, acetylcholine(by parasympathetic vagus nerve fibres),amino acids (arginine and leucine),glucagon GIP,hGH and ACTH
87
what inhibits insulin secretion?
somatostatin
88
what inhibits the secretion of somatostatin?
-pancreatic polypeptides
89
what causes the secretion of pancreatic polypeptide?
-meals containing protein, fasting,exercise and acute hypoglycaemia
90
what inhibits the secretion of pancreatic polypeptide?
elevated blood glucose levels
91
what does glucagon do?
-raises the blood glucose level by accelerating the breakdown of glucose in the liver (glycogenolysis),converting other nutriteints into glucose in the live (gluconeogenesis) and then releases glucose into the body
92
what does insulin do?
-lowers blood glucose level by accelerating the transport of glucose into cells, converting glucose into glycogen (gyconeogenesis) and decreasing glycogenolysis and gluconeogenesis,this increases lipogenesis and stimulates protein synthesis
93
what does somatostatin do?
inhibits secretion of insulin and glucagon and slows the absorption of nutrients from the gastrointestinal tract
94
what does the pancreatic polypeptide do?
-inhibits somatostatin secretion, gallbladder contraction and secretion of the pancreatic digestive enzymes
95
what happens when the blood glucose is low (hypoglycaemia)?
-alpha cells secrete glucagon -this converts glycogen into glucose (glycogenolysis) -this forms glucose from lactic acid ans certain amino acids (gluconeogenesis) -glucose released by hepatocytes raises blood glucose level to normal -if the blood glucose continues to rise hyperglycaemia inhibits the release of glucagon
96
what happens when the blood glucose is too high (hyperglycaemia)?
-beta cells secrete insulin -insulin acts on body cells to -accelerate facilitated diffusion of glucose into cells -speed conversion of glucose into glycogen (glycogenesis) -increase the uptake of amino acids and increase protein synthesis speed synthesis of fatty acids (lipogenesis) -slow glycogenolysis -slow gluconeogenesis -blood glucose levels fall -if it continues to fall,hypoglycemia inhibits the release of insulin
97
what is the thymus?
-an endocrine tissue located superiorly to the heart -it secretes thyroxin and promotes the proliferation and maturation of t-cells
98
what do T cells do?
-they are a type of white blood cell (lymphocyte) that destroys microorganisms and foreign substances
99
what are the ovaries?
-paired oval bodies located in the female pelvic cavity -they produce several steroid hormones
100
what are the different ovarian hormones?
-estrogens and progesterone -relaxin -inhibin
101
what does oestrogen and progesterone do?
-with gonadotropic hormones of the anterior pituitary ,they regulate the female reproductive cycle and oogenesis -maintain pregnancy -prepare mammary glands for lactation -promote the development and maintenance of female secondary sex characteristics
102
what does relaxin do?
-increases flexibility of pubic symphysis during pregnancy and helps dilate uterine cervix during labour and delivery
103
what does inhibin do?
inhibits the secretion of FSH from the anterior pituitary
104
what are the testes?
-oval glands that lie in the scrotum -testosterone is the main hormone produced and secreted -the hormone inhibin is also secreted
105
what does the testosterone do?
-stimulates descent of testes before birth -regulates spermatogenesis -promotes the development and maintenance of male secondary sex characteristics
106
what are the other tissues that contain endocrine cells?
-vitamin D-mineral homeostasis -angiotensinogen-increases blood pressure -secretin-increases secretion of pancreatic juice -atrial natriuretic peptide (ANP)-decreases blood pressure -gastrin-increases stomach motility -erythropoietin (EPO)-increase RBC production

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