Cell bio- endocrinology Flashcards
(213 cards)
1
Q
What is the hypothalamic-pituitary axis and what does it control?
A
hypothalamus and pituitary gland function in a coordinated fashion to orchestrate many parts of the endocrine system
2
Q
what does the H-P axis regulate? (4)
A
thyroid
adrenal glands
reproductive glands
controls growth, milk production/election and osmoregulation
3
Q
what are two types of negative feedback for the H-P axis?
A
short-loop
long-loop
4
Q
how does the long loop of negative feedback for the H-P axis function?
A
final hormone concentration affects the hypothalamus (higher concentration= more inhibition for production in the hypothalamus)
5
Q
how does the short loop of negative feedback for the H-P axis function?
A
hormones produced in the hypophysis affects the production in the hypothalamus
6
Q
what is hypophysis?
A
pituitary gland
7
Q
How does positive feedback of the H-P axis function?
A
higher concentration of hormone= more is produced
controlled so that not too much is produced
8
Q
what is an example of negative and positive feedback of the H-P axis?
A
negative= cortisol production positive= estrogen production
9
Q
what is the hypothalamus a place of and what is it composed of?
A
neurological and endocrine connection
composed of more than 12 nuclei (group of neurons)
10
Q
what are 7 functions of the body that are regulated by nuclei in the hypothalamus?
A
endocrine system body temp appetite sexual behavior defense reactions circadian rhythm vegetative system
11
Q
What are 6 hormones that are released by the hypothalamus that control anterior pituitary secretion (via releasing or inhibiting hormones)?
A
Thyrotropin releasing hormone (TRH)
corticotrpin releasing hormone (CRH)
gonadotrphin releasing hormone (GnRH)
growth hormone releasing hormone (GHRH)
growth hormone inhibiting hormone (Somatostatin/GHIH)
prolactin inhibiting hormone (Dopamine/PIH)
12
Q
what is the role of neurons in the hypothalamus?
A
synthesize and secrete the hypothalamic releasing and inhibitory hormones
13
Q
where do neurons originate in the hypothalamus?
A
various parts
14
Q
how do the endings of nerve fibers in the hypothalamus differ than from nerve endings in the CNS? (3)
A
dosen’t transmit signals
secrete hormones into the tissue fluids
hormones are immediately absorbed into the hypothalamic-hypophysial portal system (carried directly to the sinuses of the anterior pituitary gland)
15
Q
where is the hypophysis (pituitary gland) located?
A
in the sella turcica (bony cavity at the base of the brain)
connected to the hypothalamus by the pituitary stalks (infundibulum)
16
Q
what are the two portions of the hypophysis?
A
anterior pituitary (adenohypohysis) posterior pituitary (neurohypophysis)
17
Q
where does the anterior hypophysis originate from?
A
Rathke’s pouch (embryonic invagination of the pharyngeal epithelium)
18
Q
How many major types of cells are contained in the anterior pituitary and and what kind of nature do they have?
A
5 major types with epithelioid nature, each produces a different type of hormone
19
Q
what are the 5 major types of cells in the anterior pituitary and what do they produce?
A
somatotropes- produce growth hormone (GH)- 50%
corticotropes- produce adrenocorticotropin (ACTH)- 20%
lactotropes- produce prolactin
thyrotropes- produce thyroid stimulating hormone (TSH)
gonadotropes- gonadotropic hormones= luteinizing and follicle-stimulatins (LH and FSH)
20
Q
what are the 3 different appearances that the anterior pituitary cells show under alight microscope?
A
acidophilic (light pink)
basophilic (dark purple)
chromophobis (light purple)
21
Q
What types of cells are acidophilic (2) and what stain are they dyed with?
A
aomatotropes, lactotropes
acid dye- eosin
22
Q
what types of cells are basophilic (3) and what stain are they dyed with?
A
corticotropes, thyrotropes, gonadotropes
basic dye- haematoxylin
23
Q
what types of cells are chromophobic (1) and what stain are they dyed with?
A
non functional cells (don’t secrete hormones)
do not stain
24
Q
What are 5 peptide hormones produced by the anterior pituitary?
A
growth hormones cortiotropin thyrotropin prolactin gonadotropins
25
function of growth hormones
promote growth of the entire body by affecting protein formation, cell multiplication and cell differentiation
26
function of corticotropin
controls secretion of some of the adrenocortical hormones, which affect metabolism of glucose, proteins and fats
27
function of thyrotropin
controls the secretion rate of thyroxine and thriiodothyronine by the thyroid gland= control the rates of most intracellular chemical reactions in the body
28
function of prolacitn
promotes mammary gland development and milk production
29
function of gonadotropins
gontrol growth of the ovaries and testes, as well as their hormonal and reproductive activities
30
what is another name for posterior pituitary?
neuro-hypophysis
31
where does the neuro-hypophysis originate from and what is it made up of?
originates from a neural tissue outgrowth from the hypothalamus
made up of glial-like cells and axons of large neurons= magnocellular neurons
32
where are the hormones produced for the posterior pituitary and where are they transported?
hormones are produces in the hypothalamus and transported in the axoplasm to the pituitary
33
what are the twp peptide hormones secreted by the neuro-hypophysis?
antidiuretic hormone or vasopressin
| oxytocin
34
function of ADH
control the rate of water excretion into the urine, helping to control the concentration of water in the body fluids
35
function of oxytocin (2)
helps express milk from the mammary gland to the nipples during suckling
helps deliver the baby at the end of gestation
36
what are the 4 steps of hormone synthesis/secretion viz neurohypophysis?
1. hypothalamic neurons secrete hormones
2. hormones are transported alson the hypothalamic-hypophyseal tract to the posterior pituitary
3. hormones are stores in axon terminals in the posterior pituitary
4. hormones are released into the blood then hypothalamic neurons fire
37
What is the pancreas and where is it located?
a mixed gland organ in the digestive and endocrine system
| located in the abdominal cavity behind the stomach
38
what are the two categories of the pancreas?
exocrine and endocrine
39
what types of cells are involved in the exocrine pancreas and what is their function? (2/2)
acinar and duct cells
involved in GI function
secrete enzymes into the lumen of the duodenum
40
how is the endocrine pancreas organized?
in islets= islets of langerhans
41
what are the 4 cell types that make up the islets of langerhans and what do they produce?
alpha cells (20%)- glucagon
Beta cella (70%)- insulin
Delta/D cells (5%)- somatostatin
F/PP/gamma cells (5%)- pancreatic polypeptide
42
what are all hormones produced in the endocrine pancreas involved in?
glucose metabolism and the regulation of blood glucose levels
43
what type of hormone is insulin, what type of cell is it produced by, as a response to what?
polypeptide hormone
produced by beta cells
in response to hyperglycemia
44
6 steps of insulin synthesis and secretion
1. mRNA on ribosome of ER binda AA to a peptide chain= preprohormone. the chain is direction into the ER lumen by a signal sequence of AA
2. enzymes int he ER remove the signal sequence, creating inactive prohormone
3. prohorome passes from the ER to the Golgi
4. secretory vesicles containing enzymes and prohormone bud off the Golgi. enzymes cut the prohormone into active peptides and peptide fragments
5. secretory vesicle releases its contents by exocytosis into the extracellular space
6. the hormone moves into the circulation for transport to its target
45
what is insulin made up of?
a protein consisting of 2 chains (alpha and beta) connected by 2 disulfide bridges
46
what variables govern insulin release? (4)
nutritional, neural, paracrine and endocrine
47
What 3 molecules affect the release of insulin?
glucose
AA
FA
48
How is insulin released from beta cells?
glucose transporter (GLUT2) in the membrane surface
49
what directly affects glucose concentration inside the beta cells?
extracellular fluid glucose concentration
50
what does an increase glucose concentration lead to?
insulin secretion and synthesis
51
what does the secretion of insulin follow?
biphasic kinetics
52
what are the two phases of secretion of insulin and what do they each involve?
acute phase: involves the release of preformed insulin
| chronic phase: involved the synthesis of protein
53
How does insulin act on target cells?
after release, binds to a specific membrane receptor on target tissues= receptor tyrosine kinase
54
which tissues have insulin receptors? (3)
insulin-sensitive tissues
liver
muscle
fat/adipose
55
what is the net effect of insulin, and now does it accomplish it?
to lower the blood concentration of glucose, FA and AA
promote intracellular conversion of these compounds to their storage forms:
glycogen, triglycerides, proteins
56
what processes does insulin increase/decrease in the liver? (2/3)
increase glycogen synthesis and lipogenesis
| decrease glycogenolysis, gluconeogenesis and lipolysis
57
what processes does insulin increase/decrease in muscles? (4/2)
increase glucose transport, glycogen synthesis, AA uptake, protein synthesis
decrease glycogenolysis, protein degradation
58
what processes does insulin increase/decrease in fat? (3/2)
increase glucose transport, glycogen synthesis and lipogenesis
decrease glycogenolysis and lipolysis
59
How does insulin facilitate glucose entry into muscle and fat cells?
increase the number of specific glucose transporters (GLUT 4) in the cell membrane
60
what two organs metabolize insulin?
liver and kidneys
61
how is insulin inactivated? (2) what is its half-life?
specific enzymes reduce the disulfide bonds
chains are subjected to protease activity= reduce them to peptides and AA
half life is 10 min
62
what type of hormone is glucacon and what type of cell is it produced by?
polypeptide hormone produced by alpha cells
63
how is glucacon synthesized and released and what is its half life?
synthesides the same way as insulin and released by exocytosis
half-life= 5 min
64
what is the physiological action of glucagon compared to insulin?
glucagon is the opposite of insulin
65
what are the effects of glucacon and what are 3 examples?
centered int he liver and enhance the availability of glucose to the other organs of the body (increase blood glucose)
1. decrease glycogen synthesis
2. breakdown of liver glycogen- glycogenolysis
3. increase in liver gluconeogensis
66
what is glucagon synthesis stimulated by and what does glucagon work with insulin to do?
stimulated by decreased glucose concentration
| works with insulin to maintain blood glucose concentration
67
what is glucose counterregulation?
hormones that oppose the action of insulin
68
what are 4 counterregulatory hormones and what are they produced by?
glucagon= produced by pancreatic alpha cells
epinephrine= produced by the adrenal medulla
cortisol= produced by the adrenal cortex
growth hormone= produced by the adenohypophysis
69
what is pancreatic somatostatin produced and how?
produced by delta cells in the same way as other protein hormones
70
what type of actions does somatostatin have and what are 2 examples?
inhibitory actions
1. decreased motility and secretory activity of GI tract
2. inhibits secretion of all endocrine cell types of the Islet of Langerhans (glucacon is more affected than insulin)
71
what is pancreatic polypeptide produced by?
F/PP cells
72
what is the secretion of pancreatic polypeptide stimulated by (3) and how does inhibition occur?
GI hormones, vagal stimulation, protein ingestion
| inhibition occurs through somatostatin
73
where are the effects of pancreatic polypetide directed toward and what are 2 examples?
effects are directed toward the GI tract
1. increase gut motility and gastric emptying
2. inhibits secretion of pancreatic enzymes and the contraction of the gallbladder
74
what are the two layers of the adrenal gland and what are their origins?
adrenal cortex- mesodermal in origin
| adrenal medulla- ectoderminal in origin
75
what are the three zones of the adrenal cortex?
zona glomerulosa
zona fasiculata
zona reticularis
76
what type of homone does the zona glomerulosa produce and what is an example?
mineralo corticoids
| aldosterone
77
what type of hormone does the zona fasiculata produce and what are 2 examples?
cluco corticoids
| cortisol, corticosterone
78
what type of hormone does the zona reticularis produce and what are 2 examples?
sex steroids
| androgens, estrogens
79
what type of hormone does the medulla produce and what are two examples?
catecholamines
| epinephrine, norepinephrine
80
what type of hormones does the adrenal cortex produce and what are the hormones derived from?
produces steroid hormones derived from cholesterol
81
what are 3 intracellular features that all cells of the adrenal cortex have?
an abundance of lipid droplets containing cholesterol esters
mitochondria
smooth ER
82
what does the production of adrenal steroids involve?
the classic pathways for steroid biosynthesis
83
what is the first step of production of adrenal steroids and what is regulated by?
cholesterol is used to form pregnenolone (occurs in mitochondrion)
regulated by ACTH/corticotropin (limits rate of synthesis)
84
What are the 4 mechanisms of action of ACTH on adrenocortical steroidenesis
1. stimulation of the uptake of LDL, which are further processed to free cholesterol
2. stimulation of the hydrolysis of stored cholesterol esters to generate free cholesterol
3. stimulation of the transport of cholesterol into mitochondria, where cleavage of cholesterol side chain occurs
4. promotion of the binding of cholesterol to the enzyme
85
where do steroid hormones bind?
to intracellular receptors (in the cytosol or nucleus)
86
what do hormones do to the receptor after they bind?
alter the ability of the protein to control the transcription of specific genes
87
There an overlap of activity between what to steroid hormones?
glucocorticoids and mineralocorticoids
88
what are the 6 steps of steroid hormone transport?
1. hydrophobic steroids are bound to plasma protein carriers (unbound hormones diffuse into the cell)
2. receptors are int he cytoplasm or nucleus
3. receptor-hormone complex binds to DNA and activates or represses one or more genes
4. activated genes create new mRNA that moves back into the cytoplasm
5. translation produces new proteins for cell processes
6. some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses
89
where does metabolism of adrenocortical hormones occur?
in the liver
90
what does metabolism of adrenocortical hormones entail and two examples?
modification of the hormones for excretion
1. conjugation with sulfates and glucoronides reduces their biological potency
2. water soluble for passage in the urine
91
what is the clearance half-life for cortisol and aldosterone?
```
cortisol= 60 min
aldosterone= 20 min
```
92
what type of hormone does the zona glomerulosa produce and an example?
mineralocorticoids= aldosterone
93
what is the purpose of aldosterone?
role in electrolyte balance and regulation of blood pressure
94
where are the actions of aldosterone carried out?
distal tubules in the kidneys and in the salivary and sweat glands
95
what is the result of aldosterone?
retention of Na
| secretion of K and H
96
5 steps of aldosterons action in the distal tubule cells
1. aldosterone combines with cytoplasmic receptor
2. hormone-receptor complex initiates transcription in the nucleus
3. new protein channels and pumps are made
4. aldosterone-induced proteins modify existing proteins
5. result is an increased na re-absorption and k secretion
97
What is the production of aldosterone regulated by?
renin-angiotensin-aldosterone-system (RAAS)
98
what is the stimuli for aldosterone secretion caused by?
the decrease in ECF volume/plasma sodium concentration
99
What changes are perceived by the cells of the macula densa? (2)
sodium and chloride changes
100
what is another major regulatory factor for mineralcorticoid secretion, what does it stimulate, and what is the stimulation independent of?
potassium
increase in K stimulates zona glomerulosa
independent of RAAS- direct stiulation of the zona glomerulosa cells
101
Where are glucocorticoids produced and what is the major glucocorticoid produced?
Zona Fasiculata
| Cortisol
102
What is cortisol and when is it released?
a stress hormone
| released after environmental or internal challenges
103
what stimulates cortisol secretion?
ACTH produced from adeno-hypophysis
104
What is ACTH and what is its secretion controlled by?
corticotropin
| controlled by Gorticotropin releasing factor/hormone (CRF/CRH) from the hypothalamus
105
what are three things that can influence the H-P axis?
clucocortioids, stress and diurnal rhythm
106
what is the release of cortisol directly proportional to?
the level of stress
107
when does the effects of cortisol occur and what happens after that step?
after binding to nuclear receptors located in the cytosol
| the H-R complex migrates to the nucleus and stimulates or inhibits expression of specific genes
108
what are 6 effects of cortisol on carb metabolism?
stimulates synthesis of enzymes involved in gluconeogenesis during stress
causes mobilization of AA from extrahepatic tissues
antagonizes insulin's effects to inhibit gluconeogenesis in the liver
decreases glucose utilization by cells
potentiates the action of glucagon and epinephrine on glucose metabolism
can cause Diabetes Mellitus "steroid diabetes"
109
what is the main substrate for enzymes involved in gluconeogenesis during stress?
AA derived from muscle
110
Where are AA mobilized from during carb metabolism and what are the AA used for?
muscle
| more substrate for gluconeogenesis
111
what does decreased in glucose utilization by cells cause?
decreases in GLUT4 translocation in skeletal muscle= insulin resistance
112
What are the two causes of Diabetes Mellitus?
increased gluconeogenesis & refuction in glucose utilization
can also result fro chronic admnistration of glucocorticosteroids
113
what are the two effects of cortisol on protein metabolism?
reduces cellular protein
| increases liver and plasma proteins
114
What are the two causes of reduced cellular protein?
decreased protein synthesis
| increased catabolism of proteins already in the cells
115
what are the two effects of corticol on fat metabolism?
increases mobilization of FA from adipose tissue
| can cause obesity
116
what are two causes of fat mobilization?
enhanced oxidation of FFAs in cells
| shift in the metabolism from glucose to fat utilization
117
what are the 5 immumosuppressive and anti-inflammatory effects of cortisol?
stabilizes lysosomal membranes
decrease formation of prostaglandins and leukotrines production
reduces secretion of histamine by mast cells
decreases phagocytosis and suppresses antibody formation
prevents capillary dilation, fibrin deposition and connective tissue synthesis
118
What two molecules are produced by the zona reticularis?
androgens
| Some glucocorticoids
119
what are androgens and that do they interact with?
hormones that interact with male sex hormone receptors
120
what are two androgen hormones and what can two hormones can they be converted to?
Dehydroepinadrosterone and androstenedione
| can be converted to testosterone and estrogens
121
what produces and regulates androgens?
ACTH
122
what type of androgens are not significant in most animals?
adrenal androgens
123
what is the adrenal medulla and what does it secrete?
a postsynaptic ganglia of the sympathetic nervous system
| secretes neurotransmitters into the blood
124
What does the medulla produce and what is the primary one?
Catecholamine
| epinephrine
125
What is epinephrine produced by, from what AA and what other hormone is also produced?
by chromaffin cells from the AA tyrosine
| norepinephrine is also produced
126
what initiates synthesis in the medulla?
acetychole release from the preganglionic nerve fibers
127
what does the synthesis in the medulla begin with?
the conversion of tyrosine to DOPA by the enzyme tyrosine hydroxylase
128
what are the 4 end products of tyrosine?
DOPA
dopamine
epinephrine
norepinephrine
129
what happens to DOPA in the cytosol?
converted to dopamine
130
what happens to dopamine in the chromaffin granules?
converted to norepinephrine by dopamine-beta hydroxylase
131
what happens to norepinephrine in the cells that secrete epinephrine?
NE returns to cytosol where it is converted to epinephrine
132
what is the action of catecholamines involved in?
regulation if intermediary metabolism and responses that allow animals to adjust to situations involving acute stress
133
what are the actions of catecholamines mediated by and what are the 4 types?
adrenergic receptors located on target tissues
alpha 1 & 2
beta 1 & 2
134
what are the 5 effects of alpha 1 adrenoceptors?
```
vasoconstriction
increased peripheral resistance
increased blood pressure
mydriasis
increased closure of internal sphincter of the bladder
```
135
what are the 3 effects of the alpha 2 adrenoceptor?
inhibition of norepinephrine release
inhibition of acetylcholine release
inhibition of insulin release
136
what are the 4 effects of the beta 1 adrenoceptor?
tachycardia
increased lipolysis
increased myocardial contractility
increased release of renin
137
what are the 5 effects of the beta 2 adrenoceptor?
```
vasodilation
slightly decreased peripheral resistance
bronchodilation
increased muscle and liver glycogenolysis
increased release of glucagon
relaxed uterine smooth muscle
```
138
what does the aciton of catecholamines stimulate and what is its effect?
alpha receptors in arterioles of most visceral organs cause contraction of arteriolar smooth muscle
raises blood pressure, restricts blood flow
139
what are two effects to respond to the stressor or raised blood pressure and restricted blood flow?
cause vasodilation of skeletal muscle and liver arterioles
| increase heart rate and force contraction of each heart beat
140
action of catecholamines increase what, which increases the availability of what?
breakdown of glycogen in liver and muscle
| increase of glucose availability
141
What are the two effects of the increased breakdown of glycogen in liver and muscle?
stimulates lypolisis in adipose tissue
| increase basal metabolic rate
142
what are the actions of catecholamines prelare the animal for?
fight or flight response
143
what does the thyroid tissue consist of?
sac-like structures = thyroid follicles
144
what are follicle cells and what do they synthesize?
a single layer of epithelium
| synthesize the thyroid hormones
145
what are follicles filled with and what is their function?
filled with colloid= viscous protein rich fluid
| storage of thyroid hormones
146
What type of cells are located outside the follicles?
parafolicullar cells or C cells
147
what do parafolicullar cells secretes and what is its function?
secretes calcitonin
| hormone that regulates Ca metabolism
148
what two molecules are important for production of the hormone?
tyrosine
| iodine
149
what is tyrosine a part of?
a large protein= thyroglobulin
150
where is thryoglobulin formed and where is it secreted into?
formed within follicle cell and secreted into the colloid
151
what does thyroglobulin contain and what is its function?
contains many tyrosine AA
| substrate that combines with iodine to form thyroid hormones
152
where does iodine come from, what is it converted to and where, where it it transported to?
comes from diet
converted to iodide in the intestinal tract
transported to the thyroid
153
how to follicle cells trap the iodide?
through active transport by the Na/I cotransporter
154
what molecule oxidized iodine to iodide?
thyroid peroxitase
155
what is binding of iodine with the thyroglobulin molecule called?
organification of the thyroglobulin
156
how many iodine molecules can tyrosyl ring accommodate and what are they?
2 iodine molecules
1 molecule= monoiodotyrosine (MIT)
2= diiodotyrosine (DIT)
157
What happens after the tyrosyl ring is bound to iodine molecules?
TOP catalyses the coupling of two of the iodinated thyrosines
158
what are the two possible products of the fusion of two iodinated tyrosines?
2 DIT= T4/thyroxine/thyronine/tetraiodothyronine
| MIT + DIT= T3/triiodothyronine
159
what happens to thyroid hormones when they remain attached to thyroglobulin?
stored in the colloid until secretion= thyroid stores a large reserve of hormone
160
what three molecules are bound to thyroid hormone to pass through membranes?
thyroglobulin
albumin
thyroxine binding 3 albumin= T4
161
what does the secretion of thyroid hormones involve?
endocytosis of iodinated thyroglobuin back into the cell
162
what is the role of lysosomal enzymes in thyroid hormone synthesis?
cleaves hormones (MIT, DIT, T3 and T4) from thyroglobulin after it enters the cell
163
What happens to T3/T4 and MIT/DIT after they are released from the thyroglobulin?
T3 & T4 are lypophilic and freely pass through the membrane
MIT & DIT are deiodinated and products (iodine and tyrosine) are recylec to form new hormones
164
what stimulates thyroid secretion?
stimulation by TSH= thyroid-stimulating hormone, released by adeno-hypophysis
165
What is the thyroid releasing hormone released by?
thypothalamus
166
what is a positive feed back and 2 negative feedback stimulants for thyroid?
```
positive= cold
negative= stress on hypothalamus, product from target home suppresses release of TSH
```
167
How are thyroid hormones transported?
in plasma attached to proteins produced by the liver
168
What thyroid hormones are free in circulation?
T3 and T4
169
what happens to T4 once it enters the target cell?
it will be converted to T3 by iodothyronine deiodinases in the cytosol
170
what is the primary role of thyroid hormones?
control of metabolism
171
how does the thyroid hormone control metabolism?
bind to nuclear receptors and initiate the transcription of mRNA
172
What three factors of metabolism are controlled by the thyroid?
basal metabolic rate of cells
| carbohydrate metabolism and fat metabolism
173
what affect does thyroid hormones have on the mitochondria?
increase the number of mitochondria and its activity= increase rate of formation of ATP
174
what is Basal metabolic rate?
the minimal rate of energy expenditure per unit time at rest
175
How do cellular enzyme react in response to thyroid hormones and what is ian example?
increase the activity
| NA-K-ATPase
176
what are two clinical consequences of the functioning of thyroid?
```
hyper= weight loss
hypo= weight gain
```
177
what is the result of stimulation of carb metabolism?
glucose uptake, glycolysis, gluconeogenesis, GI absorption
178
What is the result of stimulation of fat metabolism? (2)
enhance mobilization, increase FFAs
| plasma and liver fat are decreased
179
what two effects does the thyroid have on the heart?
increase blood flow and cardiac output
| increase heart rate
180
how does the thyroid increase blood flow and heart rate?
vasodilation
| direct effect on excitability of the heart
181
what are 2 effects of the GI from thyroid?
increase appetite and food intake
| increase GI motility
182
what does thyroid cause in amphibians?
metamorphosis
183
how does they thyroid affect growth and development? (2)
permit maturation of the nervous system, sympathetic nervous system and CNS
allow long bones to grow and mature properly
184
what can occur if there are inadequate amounts of thyroid hormones?
reduced mental abilities
185
what is the main role of the parathyroid gland?
metabolism of calcium and phosphate
186
what is the role of phosphate and what % is in bones, intracellular and ECF?
buffer system
85% bones
14% intracellular
1% ECF
187
What is phosphate the composition of and what are three examples?
cell membrane and intracellular components
| nucleic acid, ATP, ADP
188
what percentage of Ca is in bones, intracellular and ECF?
bones= 99
intracellular= 0.9
ECF=0.1
189
what are 7 roles of Ca?
```
muscle contraction
nerve cell activity
release of hormones by exocytosis
activation of several enzymes
coagulation
maintenance of membrane stability
structural integrity of bones and teeth
```
190
how is blood Ca separated by % (3)
50% ionized = iCa
40% bound to proteins
10% combined with other anions
191
is iCa biologically active or inactive?
active
192
the regulation of Ca levels involves what?
the control of the movement of Ca between the ECF and 3 organs
193
what 3 organs are involved in Ca regulation?
Bones
GI tract
Kidney
194
what 3 hormones are involved in Ca regulation?
PTH
VIT D
Calcitonin
195
how many types of parathyroid cells are there in the grandular tissue and what are they?
2
active cells= chief cells
inactive/degenerated= oxyphil cells
196
what is the function of chief cells and of oxyphil cells?
```
chief= produce PTH
oxyphil= unknown function
```
197
what are parathyroid cells very sensitive to?
decline of iCa
198
what does a drop in iCa cause in parathyroid cells?
activates receptors in membrane
199
How is PTH produced?
preprp-PTH is synthesized in ER and cleaved to pro-PTH
| pro is removed by Golgi and PTH is secreted by exocytosis
200
where is PTH metabolized (2) and what is its half-life?
kidney and liver
| 5-10 min
201
What are the 2 effects of PTH?
increase Ca and decrease phosphate conc in ECF
202
what type of effect does PTH have on bone and kidney and on GI metabolism of CA
Bone and kidney= direct effect
| GI= indirect
203
how does PTH directly affect bones? (2)
binds to receptors on osteocytes and stimulates osteocytic-osteolysis= pump Ca from fluids withbone canaliculi into ECF and blood
binds to receptors on bone osteoblast cells and stimulates the production of osteoclast-activating factor= releases Ca and PO4
204
gow doe PTH directlly affect kidneys? (3)
acts on distal convoluted tubules to inc absorption of Ca
dec renal phosphate absorption of prozimal tubules
activation of VIT D
205
how fro PTH indirectly affect GI?
calcitriol stimulates the active transport of dietary Ca across the intestinal epithelium
206
why is calcitrol important to most animals?
without it, they are unable to acquire enough Ca from the diet to support bone structure and regulation of Ca entering the blood
207
what are two exceptions to requiring calcitriol, and why?
horse and rabbit
| intestinal mechanisms absorb Ca all the time
208
what is PTH regulated by, and how?
free (ionized) Ca conc in the blood
| dec in iCA stimulates PTH secretion, vise versa
209
what and where is calcitonin produced?
by parafolicullar cell/ C cell in the thyroid gland
210
what does calcitonin act as?
counterbalance to PTH
211
what are 4 actions of calcitonin?
dec movement of Ca in the bone
Dec bone reabsorption through an inhibitory effect on ostoclasts
inc movement of phosphate from ECF into bone
inc renal excretion of Ca and phosphate
212
what is calcitonin secretion regulated by?
Ca- inc Ca stimulates secretion
213
what stimulates secretion of calcitonin, and what are 3 examples?
GI hormones
| Gastrin, secretin, glucagon
