endocrine Flashcards
1
Q
what does the endocrine system do?
A
Integration and coordination with hormones in response to stress, the body’s internal environment, metabolism, growth and development and reproduction
2
Q
what is homeostasis?
A
the ability to regulate its internal conditions typical using feedback systems to minimize variation regardless of external environment
3
Q
what are hormones?
A
molecules, secreted by endocrine cells into circulating blood, that act on cells that express their specific receptors
Some molecules are both hormones and neurotransmitters, both bind with specific receptors
Hormones are very cell specific.
4
Q
what is an autocrine cell?
A
receptor on its own surface
5
Q
what is a paracrine cell?
A
cell next door so it doesn’t go into blood just the matrix
6
Q
A
7
Q
what is a negative feedback loop?
A
accomplished what’s needed and sends a signal to stop producing. Reduces the effect of the stimulus.
8
Q
what are the characetristics of a negative feedback loop?
A
Variable
Sensor
Integrator
Effector
9
Q
what is an example of a negative feedback loop?
A
shivering when cold
10
Q
what is a positive feedback loop?
A
ends with an event that will cause something “explosive event”. Increases the effect of the stimulus
11
Q
what is a feed-forward mechanism?
A
anticipatory response that starts a feedback loop in anticipation of a change about to occur. Usually a reflex
12
Q
A
13
Q
what are the characteristics of steroid hormones?
A
Derived from cholesterol
Lipid soluble
Not stored
Target = inside cell
Transported in blood bound to plasma proteins
14
Q
what are the caracteristics of tyrosine hormones (general)?
A
Derived from tyrosine
15
Q
what are the 2 types of tyrosine hormones?
A
catecholamines and thyroid hormones
16
Q
what are the characteristics of catecholamines?
A
In cytosol
Stored in chromaffin granules
Transported through blood half bound to plasma proteins
Target = surface of cell
17
Q
what are the characteristics of thyroid hormones?
A
n colloid
Stored in colloid
Transported through blood mostly bound to plasma proteins
Target = inside cell
18
Q
describe the mecahnism of the cAMP second messanger system for hydrophilic hormones;
A
Binding of messenger to receptor activated G protein - activates adenylyl cyclase
Adenylyl converts ATP to cAMP
cAMP activated protein kinase A
Protein kinase A phosphorylates inactive target protein
Cellular response initiated
19
Q
describe the mechanism of the calcium ion mechanism for hydrophilic hormones:
A
Binding of messenger to receptor activated G protein - activates phospholipase C
Phospholipase C converts PIP2 to IP3 and DAG
IP3 can;
Mobilize intracellular Ca2 to activate calmodulin which creates a complex. The complex activates CaM kinase which phosphorylates inactive target protein to activate it
DAG activates protein kinase C which phosphorylates inactive target protein to activate it which initiates response
20
Q
every level of a second messenger does what?
A
amplifies the response
21
Q
what is the sella turcica?
A
protective pocket on the sphenoid bone for the pituitary gland. Shaped like a saddle.
22
Q
how many lobes does the pituitary have and what are they?
A
2
anterior
posterior
23
Q
what is the only thing anterior and posterior pituitary have is common?
A
location
24
Q
describe the neural pathway of the posterior pituitary;
A
1: the hormone is made and packaged in cell body of neuron
2: vesicles are transported down the cell
3: vesicles containing hormone are stored in posterior pituitary
4: hormones are released into blood
25
what are 2 hormones of the posterior pituitary?
oxytocin and ADH
26
what are the 2 most well known events oxytocin is involved in?
breastfeeding and childbirth
27
describe the feedback mechanism for birth;
Signals from cervix (stretch) - oxytocin release - uterine smooth muscle contraction
28
describe the feedback loop for breastfeding;
ignals induced by suckling - oxytocin release - mammary gland smooth muscle contractions to expel milk
29
what else releases oxytocin?
orgasms
30
describe the role of the hypothalamus for the endocrine system;
Site of interaction between nervous and endocrine
Many interconnections with other parts of the brain
Emotions and stresses affect endocrine function
31
what does ADH control?
body fluid volume and concentration
32
what does ADH target?
kidney and smooth muscle
33
what does ADH do in the kidney?
reduce urinary output and conserve water
34
what does ADH do at smooth muscle?
causes vasoconstriction
35
how does ADH limit urine production?
Increases the permeability of renal collecting tubule cells to water thus more water will be reabsorbed in kidneys and less urine produced. Mediated by binding to specific receptors
ADH binds, ATP is transformed into cAMP which increases the permeability
36
what does the concentration of ADH rise in response to?
increased osmolarity in the ECF
37
what is one key factor that ADH does other than maintaining concentration and volume?
makes you thirsty
38
desrcribe how high osmolarity in the ECF triggers secretion of ADH;
hypothalamic osmoreceptor neurons (lie outside the BBB) detect the changes. High osmolarity causes outside cells to shrink and induces ADH secretion
39
describe how low blood volume induces secretion of ADH;
ocated in low pressure, complaint vessels that accommodate blood volume changes and buffer arterial pressure changes. Sensory nerve endings detect the amount of “stretch” and signal PVN and SON. decreased stretch causes ADH to recover the fluid volume.
40
describe the osmoreceptor loop;
Variable: increased ECF osmolarity
Sensor: osmoreceptors in hypothalamus
Integrator: SON and PVN nuclei in hypothalamus - increased ADH
Effector: kidney collecting tubule - increased water reabsorption
41
describe the stretch receptor loop;
Variable: decreased blood volume
Sensor: stretch receptor neurons around large vein and cardiac atria
Integrator: SON and PVN in hypothalamus - increased ADH
Effector: kidney collecting tubule - increased water reabsorption
42
why does alcohol make you thirsty?
inhibits ADH but as alcohol is disposed of in the system it increases dehydration to make you secrete more ADH
43
what is the blood brain barrier?
Specialized endothelial with tight junctions strictly control environmental exposure and protect the brain
44
where is the blood brain barrier lackinh?
where hormones are intended for entry to circulation
where neurons need to respond to stimuli from circulation
45
what hormones do the anterior pituitary produce?
TSH, ACTH, PROLACTIN, GH, LH and FSH
46
what are the "trophs" and what do they produce?
Somatotropes: produce GH
Lactotrophs: produce prolactin
thyrotrophs: produce TSH
Gonadotrophs: produce LH and FSH
Corticotrophs: produce ACTH
47
describe the feedback mechanism of the hypothalamic-hyposeall portal system;
Hormonal and neural input hit the hypothalamic neurosecretory neuron which secretes hormone 1 which goes through a short portal system
The anterior pituitary is activated from hormone 1 to secrete hormone 2 which goes into systemic circulation
Hormone 2 activates the target endocrine gland which secretes hormone 3 before being sent into general circulation
Finally elicits the physiological effect on target cells
Hormone 3 has a negative effect on the anterior pituitary and hypothalamus
48
if hormone 1 is deficient in the hypothalamic-hypophyseal portal system what will happen to 2 and 3?
they will also be low and the loop will be reduced
49
describe what hormone 1 is in the hypothalamic-hypophyseal portal system;
hypothalamic releasing hormones
Stimulate release of a specific hormone from cells of anterior pituitary
Thyrotropin releasing hormone (TRH)
Corticotropin releasing hormone (CRH)
Growth hormone releasing hormone (GHRH)
Prolactin releasing hormone (PRH)
Gonadotropin releasing hormone (GNRH)
Inhibiting hormones: prolactin inhibiting hormone (dopamine) and growth hormone inhibiting hormone (GHIH)
50
describe what hormone 2 is in the hypothalamic-hypophyseal portal system;
glycoprotein family, POMC family or GH/Prolactin family.
Glycoprotein: hydrophilic, produced and stored in anterior pituitary cells (gonadotrophs or thyrotrophs). FSH and LH (gonadal target. Stimulate follicle development and spermatogenesis), TSH (acts on thyroid to stimulate secretion of thyroid hormones)
POMC: CRH from hypothalamus stimulates production of POMC by corticotrophs. Here, the large POMC glycoprotein pro-hormone is cleaved to produce; ACTH, beta-endorphins and gamma-lipotropin
GH/prolactin: proteins. Prolactin stimulates milk production.
51
describe the hypothalamic-hypophyseal portal vascual system;
Neurosecretory neurons in hypothalamus secretes releasing and inhibiting hormones into portal system
Goes through the hypothalamic-hypophyseal portal
Endocrine cells of anterior pituitary secrete anterior pituitary hormones into systemic blood
52
what is the carcadian rhythm?
hypothalamic releasing hormones, their anterior pituitary hormones and target cell hormones exhibit circadian rhythms. Prolactin is the only exception. Arise from intrinsic neural oscillators
53
what are the characteristics of the carcadian rhythm?
1 major peak/24 hrs. Related to sleep/wake cycle. Each anterior pituitary hormone peaks at different times. Endocrine activity of target organs reflects the oscillation.
54
where is cortisol produced and when does it peak?
produced in the adrenal cortex by ACTH. peaks first thing in the morning.
55
what does ACTH do?
targets adrenal gland cortex and modulates secretion of adrenal cortex hormones; aldosterone, cortisol and androgens
56
what are the characteristics of growth hormone?
Increased lipolysis, protein synthesis, use of fatty acids, collagen synthesis, cartilage growth
Promotion of hypertrophy and hyperplasia
Decreased glycogen synthesis and glucose use
57
what is the epiphyseal plate?
zone for bone growth. Thickens during growth
58
what are the major inputs for the growth hormone feed back loop?
exercise, stress, low blood glucose, diurnal rhythm
59
what are the minor inputs for the growth hormone feedback loop?
high blood amino acids, low blood fatty acids
Ghrelin
60
describe the feedback loop for growth hormone;
Go to the hypothalamus to produce GHIH and GHRH
They activate the anterior pituitary somatotroph that releases GH
It can go to the liver t0 make IGF1 and promote actions related to growth
Or it can be used for metabolic actions unrelated to growth
61
how is secretionof growth hormone stimulated?
Stress
Exercise
Hypoglycemia
Amino acids
First 2 hours of deep sleep
62
what is gigantism?
Abnormally large growth due to excess growth hormone during childhood before closure of growth plates
63
what is acromegaly?
Over secretion of GH after growth plates have closed. Height unchanged but thicker mature bones
64
what is turners syndrome?
Females
Have short stature, GH is recommended at puberty
65
what is pituitary dwarfism?
GHRH, GH or IGF 1 deficiency
66
what is laron dwarfism?
Unresponsive GH receptors
67
what is cretinism?
Hypothyroidism
Thyroid hormones are permissible for action of GH
Poor long bone growth as a result of thyroid hormone insufficiency.
68
68
what is achondroplasia?
Gene defect for cartilage FGF receptors impairs bone ossification
69
what does the medualla of the adrenal gland arise from?
ectoderm
70
what does the cortex of the adrenal gland arise from?
mesoderm
71
in the adrenal cortex, what parts secret cortisol and androgens?
fasciculata and ZFR
72
what type of hormones are adrenal cortex hormones?
cholesterol derived
73
how is cholesterol transported through the blood?
as LDL
74
what receptor do androgens bind to?
androgen receptor
75
what receptor does cotrisol bind to?
glucocorticoid receptor
76
what receptor does aldosterone bind to?
mineralocorticoid receptor
77
what is the rate-limiting SCC enzyme induced by?
angiotensin II or elevated plasma potassium in the outer zone
ACTH in the middle zone
78
describe what ATCH does in the 3 zones of the adrenal cortex;
stimulates and maintains cellular growth
up regulates LDL receptors
79
what does too much ACTH cause?
hypertrophy
80
what does too little ACTH cause?
atrophy
81
what are the biological effects of cortisol?
carb, proteib and fat intermediary metabolism
protects during acute stress
anti-inflammatory and immunosuppressive
permissive actions for other hormones
82
what are the metabolic effects of cortisol?
raises blood glucose (gluconeogenesis)
raises blood amino acids
raises blood fatty acid levels
83
how is cortisol protective during stress?
stress stimulates CRH/ACTH/cortisol secretion
metabolic actions increase "raw materials" needed to respond to stress
84
how does cortisol have anti-inflammatory and immunosuppressive effects?
limits immune response
suppresses all steps in inflammation
destroys lymphocytes and reduces antibody production
85
what is the effect of exogenous corticosteroids on the ACTH feedback loop?
inhibits CRH which is at the top if the loop therefore it will inhibit the ones that follow
86
in the absence of cortisol what happens to the effectiveness of other hormones?
they are less effective
87
what is cushing's syndrome?
hypersecretion of cortisol;
excessive CRH or ACTH
possible ACTH secretibg tumor elsewhere in the body
adrenal cortex tumors that secrete cortisol without ACTH
high blood glucose and protein catabolism
fat redistribution to throax and abdomen
moon-face
88
what is adrenogenital syndrome?
sex steroid hypersecretion;
steroid production in ideoendent from ACTH control
newborn females - sex reversal
mature women - masculinization
young males - precocious puberty
89
what is addisons disease?
adrenocortical insufficiency ;
adrenal cortex being destroyed by autoimmune
lack of adrenal hormone production from level of hypothalamus or anterior pituitary
90
what autonomic nervous system component is the adrenal medulla a modified component of?
sympathetic
91
describe the synthesis of catecholamines;
tyrosine - DOPA (by tyrosine hydroxylase) - dopamine - 20% noepi, 80% epi (by transferase enzyme induced by cortisol)
92
are catecholamines essential for life?
no
93
aside from the stress responses from the ANS what stress responses are specific to the endocrine system?
increased secretion of cortisol, ADH, aldosterone, glucagon and growth hormone
94
what is the role of cortisol during stress?
increases metabolic fuels
permissive for catecholamine stimulated vasoconstriction
induces enzyme roduction of epi
95
what is the role of ADH and aldosterone during stress?
retention of sodium and water to protect ECF and blooc volume
96
what is the role of glucagon during stress?
opposes effects of insulin to increase blood glucose
97
what is synergism?
the interaction or cooperation of two or more organizations, substances, or other agents to produce a combined effect greater than the sum of their separate effects.
98
describe the HPA axis:
stress and dinural stimulate the hypothalamus to released CRH which activates the anterior pituitary to released ACTH which stimulates the adrenal cortex to release cortisol
99
where are serum binding proteins primarily produced?
liver
100
what is serum albumin?
a large plasma protein present in high concentration
101
which has a longer molecule life, peptide or lipophilic hormones?
lipophilic
102
where is the thyroid gland located?
in the neck, below chin
103
how many thyroid hormones are there and what are they?
2
T3 and T4
104
how must iodine be obtained?
through diet
105
describe the synthesis of thyroid hormones;
1: follicular cell synthesizes enzymes and thyroglobulin for colloid
2: I is co-transported into the cell with Na and transported into the colloid
3: thyroid peroxidase oxidizes iodine ions, MITS and DITS couple to form T3 and T4
4: thyroglobulin is taken back into the cell
5: intracellular enzymes separate T3 and T4 to form protein
106
what enzyme oxidizes iodine ions so they are incorporated into thyroglobulin?
thyroid oxidase
107
what 2 tyrosine moieties couple to make T3 and T4?
MITS and DITS
108
is thyroid binding with proteins reversible or irreversible?
reversible
109
how is T4 converted to T3?
deionation in liver and kidneys
110
how much circulating T3 has been converted from T4?
80%
111
which is more bioactive, T3 or T4?
T3 - principal thyroid hormone
112
what is every step of the thyroid hormone loop controlled by?
TSH
113
how is TSH production controlled?
by hypothalamic TRH (thyrotropin releasing)
114
describe the feedback loop of thyroid hormone production;
stress/cold in infants signals the hypothalamus to produce TRH which signals the anterior pituitary to release TSH which signals they thyroid gland to make thyroid hormone
115
what does a deficiency of TSH cause?
atrophy of the thyroid gland
116
what does excess TSH do?
causes hypertrophy and hyperplasia of cells
117
what is an enlarged thyroid called?
goiter
118
what is the bioacitvity of thyroid hormones?
metabolism
growth and development
nervous system development and function
119
what is basal metabolic rate
an estimate of an individuals lowest energy expenditure required to maintain vital functions
120
what is the net effect of normal amounts of thyroid hormones?
anabolic
121
what is the net effect of pathologically high amount of thyroid hormones?
catabolic
122
thyroid hormone deficient children show...
slowed growth
123
what is the effect of thyroid hormone on nervous system function?
increases sympathetic activity
increases catecholamine receptor expression
increases speed of nervous reflexes
124
what is hypothyroidism?
low secretion of thyroid hormone
125
what is hyperthyroidism?
excess secretion of thyroid hormone
126
what can cause hypothyroidism?
failure of thyroid gland
failure of hypothalamus or anterior pituitary
lack of iodine
127
waht is caused by hypothyroidism?
myxedema
128
what causes hyperthyroidism?
autoimmune disease (graves) in which TSI stimulates TSH receptors
thyroid tumor secreting thyroid hormones
excess secretion of TRH or TSH by hypothalamus or anterior pituitary
129
what is caused by hyperthyroidism?
bulging eyes (exophthalmos)
130
what causes goiter?
hypothyroidism due to lack of iodine
hyperthyroidism due to excess TRH/TSH
131
why is calcium homeostasis essential?
bones and teeth
all cells
nerve and muscle function
blood clotting
132
what are the 3 hormones responsible for calcium homeostasis?
oarathyroid hormone
calcitonin
vitamin D
133
how is calcium regulated in the ECF?
exchange between bone and ECF
renal excretion
134
what type of receptor do the cheif cells in the parathyroid have?
calcium ion sensing
135
what type of hormone is PTH?
peptide
136
what type of feedback loop is PTH controlled by?
negative
137
what does PTH act on?
bones, kidneys and GI
138
what are osteoblasts?
create new bone by secreting organic matrix and mineralizing it with calcium phosphate crystals
139
what are osteocytes?
arise from entombed osteoblasts. involved in calcium regulation but do not create bone
140
what are osteoclasts?
dissolve bone by solubilizing the crystals
141
what does PTH stimulate?
movement of ionized ca2 from bone to ECF
bone dissolvinf activity of osteoclasts
tips bone remodeling in favour of resorption
142
what is fast exchange associated with for PTH?
osteocytic-osteoblactic bone membrnae
143
what is slow exchange associated with for PTH?
dissolution of the bone by osteoclasts
144
what do osteoblasts secrete?
RANKL (decrease bone mass) and OPG (increase bone mass)
145
what is the effect of PTH on the kidneys?
increase renal reabsorption of calcium and increase excretion of phosphate
146
what is the feedback loop associated with PTH?
lowered plasma Ca2 stimulates the parathyroid to produce PTH which signals the KIdney to increase renal tubular Ca reabsorption and decrease urinary excretion of Ca, and also signals the bone to mobilize Ca2
147
what type of effect does calcitonin have on bone remodeling?
an opposite effect to PTH
148
what type of hormone is calcitonin?
peptide
149
what is the feedback mechanism for calcitonin;
an increase in plasma Ca2 signals thyroid C cells to produce calcitonin which will decrease plasma Ca2
150
how is vitamin D derived?
from skin by action of sunlight and from some foods
151
what type of hormone is vitamin D?
steroid
152
how is vitamin D activated?
by addition of 2 hydroxyl groups
1st in liver
2nd in kidneys
153
how is kidney hydroxylation enzyme stimulated?
PTH
low plasma ionized calcium
low plasma ionized phosphate
prolactin
154
when plasma ionized calcium is high, renal hydroxylation produces...
an inactive form of vitamin D3
155
what are the effects of activated vitamin D3?
increases total body calcium
increases ECF ionized calcium
156
what is hypoparathyroidism?
caused by autoimmune disease or physical damage to glad
low PTH = low plasma Ca2
causes increased neuromuscular excitability
paresthesia
tetany
157
what is hyperparathyroidism?
1: hypersecreting parathyroid tumor
hypercalcemia
depressed muscle and nerve excitability
increased fracture risk
risk of kidney stones
2: chronic renal disease or Vit D deficiency causing hypocalcemia
impairs GI absorption of calcium
bone demineralization
kids = rickets
adults = osteomalacia
158
what affects vitamin D profuction?
skin pigmentation
159
what risks are associated with vitamin D deficiency?
risk of cancer
cardiovascular disease
autoimmune disease
MS
osteoporosis
160
what is osteoporosis?
brittle bone disease
bone resorption is greater than formation
161
what percent of the pancrease is endocrine?
2%
162
what hormones are secreted by the islets of langerhans?
beta cells (insulin and amylin)
alpha cells (glucagon)
D cells (GHIH)
PP cells (pancreatic polypeptide)
163
what is the role of insulin?
stimulates uptake and storage of energy substrates
164
what is the role of glucagon?
stimulates production of glucose by the liver
165
waht is the function of somatostatin?
inhibition of exocrine and endoccrine pancreatic secretion
166
what is the function of pancreatic polypeptide?
inhibition of exocrine pancreatic secretion
167
what is the role of pancreatic hormones?
provide constant supply of glucose to CNS
168
what are the absorptive and postabsorptive states?
fed and fasted states, respectively
169
what is the most significant regulted variable?
blood glucose concentration
170
insulin is dominant in what state?
fed
171
glucagon is dominant in what state?
fasted
172
what other factors influence insulin secretion?
increase in blood amino acid level
entry of glucose into small intestine (stimulates GIP and GLP)
increase in parasympathetic activity
173
what do glucose transporters do?
accomplish passive facilitated diffusion of glucose across cellular membranes
174
which glucose transporter is insulin dependent?
GLUT-4
175
is insulin needed in exercising muscle?
no
176
is insulin needed for glucose uptake by brain or liver?
no
177
what decreases affinity of receptors?
excess glucocorticoids
178
what down regulates receptors?
chronically high insulin
179
if the affinity of receptors is decreased and receptors are downregulated, what is the result?
insulin resistance
180
what upregulates receptors?
starvation
181
what are the major effects of insulin on carb metabolism?
increase in glycogenesis in skeletal muscle and liver
decrease hepatic gluconeogenesis
increased glucose upatke by fat cells and resting skeletal muscle
182
how is insulin abused by athletes?
inject insulin and eat high sugar foods to increase glycogen storage
183
what are the major effects of insulin on fat metabolism?
increase in transport of fatty acids into fat cells
increase of TAG synthesis
activates enzymes that catalyze synthesis of fatty acids from glucose - inhibits lipolysis
184
what are the effects of insulin on protein metabolism?
increase transport of blood amino acids
increase protein synthesis
inhibits protein degradation
185
what is the second messenger system for glucagon?
cAMP
186
what is hypoglycemia?
hyper-secretion of insulin
beta cell tumor
overdose of insulin
187
what is diabetes mellitus?
under secretion or resistance to insulin
188
what is type 1 diabetes?
autoimmune destruction of beta cells usually in children
189
what is diabetes insipidus associated with?
ADH deficiency
190
what is A1C?
a measure of glycosylation state of hemoglobin
191
for non-diabetics what is an average A1C result?
5%
192
what can uncontrolled glucose usually cause?
metabolic disease
193
what is gestational diabetes?
glucose intolerance with onset or first recognition during pregnancy
194
what are the risks associated with gestational diabetes?
fetal malformation, macrosomia, metabolic complications
195
what is type 2 diabetes?
impaired insulin secretion or resistance
196
what does chronic overeating influence?
high blood glucose, high insulin secretion
down-regulates insulin receptors
197
what do TZDs do for type 2 diabetes?
improve A1C and glucose control
increased fat storage. reducing circulating fatty acids, blood glucose, hyperinsulinemia
198
what are the competing behavioural states?
appetite and satiety
199
what is satiety?
the feeling of fullness
200
where are satiety and appetite controlled?
hypothalamus
201
what is the glucostatic theory?
blood glucose levels ultimately control the feeding and satiety centers
202
what is the lipostatic theory?
the level of body fat regulates the feeding and satiety centerss
203
where is leptin produced?
adipose tissue
204
when does ghrelin increase?
in response to decreased body fat and increased muscle mass
205
what characterizes metabolic syndrome?
high blood glucose
high blood pressure
high TAG
low HDL
obesity of abdominal area
