Module 1: Endocrine Physiology Flashcards
1
Q
What are the 6 functions of the endocrine system?
A
- Maintain constant internal environment via regulation of metabolism and water/electrolyte balance
- Adaptive Stress response
- Growth and development
- Reproduction
- Red blood cell production
- Integrating with the ANS in regulating both the circulation and digestive function
2
Q
In general, what are hormones?
A
Hormones are chemical substances that are secreted directly into the blood at low quantities.
3
Q
What do hormones do? What do they inflict on?
A
They exert a physiological effect at a distant target tissue
4
Q
What are the two major categories of hormones?
A
Hydrophilic and lipophilic
5
Q
Describe the properties of hydrophilic hormones
A
- Highly water soluble
- Low lipid solubility
- Found unbound to carrier molecules within the plasma
6
Q
What are the two major kinds of hydrophilic hormones?
A
Peptide hormones
Amines
7
Q
Describe peptide hormones
A
They are made of peptides or proteins
8
Q
Describe amines
A
Hormones based on a single amino acid residue
9
Q
What are the two types of amine hormone?
A
Catecholamines
Thyroid hormones
10
Q
Describe catecholamines. Give an example
A
Can be both free or bound to carrier molecules
Ex., nonepinephrine and epinephrine
11
Q
T/F
Thyroid hormones are hydrophilic
A
False! Even though they are an amine hormone, they are not hydrophilic
12
Q
What is the precursor to peptide hormones
A
Preprohormones
13
Q
What are the 4 stages of peptide hormone synthesis?
A
- Synthesis
- Packaging
- Storage
- Secretion
14
Q
Describe the synthesis stage of peptide hormone synthesis
A
Precursor proteins called preprohormones are synthesized by ER ribosomes
15
Q
Describe the packaging stage of peptide hormone synthesis
A
The preprohormones are processed into active hormones and packaged into secretory vesicles
16
Q
Describe the storage of peptide hormones
A
The vesicles they are contained in are stoped in the cell until the signal for release occurs
17
Q
Describe the secretion stage of peptide hormones
A
The appropriate signal initiates exocytosis of the vesicles and the hormones are released into the blood
18
Q
Describe lipophilic hormones
A
They are highly soluble in lipids and poorly soluble in water
They require carrier molecules to be transported
19
Q
What general hormones are lipophilic hormones?
A
Amine thyroid and steroid hormones
20
Q
What are all steroid hormones synthesized by?
A
Cholesterol
21
Q
What determines the specific steroid hormone that is produced?
A
Depends on the specific enzymes within that cell of that tissue
22
Q
How are steroid hormones stored
A
AHAH Trick question
They aren’t. They are released as they are synthesized
23
Q
How do bound hormones interact with their target cells?
A
They are constantly binding and rebinding. The unbound state is when they are active and able to act on target cells
24
Q
How can one determine if a hormone will act on a specific cell
A
It depends if the cell expressed a specific receptor for that hormone
25
What kind of hormone binds to specific receptors on the outside of their target cells
Peptide hormones
26
What kind of hormone binds to specific receptors inside their target cell. Why?
Lipophilic hormones
Because they can slip through the cell's plasma membrane
27
How do peptide hormones produce an effect on a cell once it binds to the receptor?
It activates second messenger systems
28
Describe Cyclic AMP as a secondary messenger
- Extracellular messenger binds to a receptor, activating a G-protein. This shuttles and activates adenyl cyclase molecules
- The adenyl cyclase molecules convert ATP to cAMP, which activates protein kinase A
Protein kinase A enzymes then phosphorylate and activate target proteins, which bring about the desired response
29
Put the steps of cAMP messaging in the correct order:
G-protein activated
Protein kinase A phosphorylates target proteins
Proteins bring about response
adenyl cyclase converts ATP to cAMP
cAMP activates protein kinase A
adenyl cyclase molecules are activated
Extracellular messenger binds
Extracellular messenger binds
G-protein activated
Adenyl cyclase activated
Adenyl cyclase converts ATP to cAMP
cAMP activates protein kinase A
Protein kinase A phosphorylates target proteins
Proteins bring about response
30
In the secondary messenger system involving calcium: What initiates the reaction?
An extracellular messenger binding to a receptor
31
In the secondary messenger system involving calcium: an extracellular messenger binding to the receptor activates what?
A G-protein
32
What is the involvement of the activation of a G protein in the In the secondary messenger system involving calcium
Activates several phospholipase C enzymes
33
In the secondary messenger system involving calcium: what do the phospholipase C enzymes do?
Convert PIP2 into IP3 and DAG
34
In the secondary messenger system involving calcium: what is the purpose of IP3?
It mobilizes intracellular calcium ions, which activate calmodulin
35
In the secondary messenger system involving calcium: the calcium-calmodulin complex activate what? What does this do?
It activates calcium-calmodulin-dependent protein kinase, which phosphorylates and activates target proteins
36
In the secondary messenger system involving calcium: what do the target proteins do?
Bring about the desired response
37
How do steroid and thyroid hormones bring about a response within the cell?
They produce effects by regulating gene transcription and protein synthesis
38
Put these steps of lipophilic hormones and protein synthesis in order:
1. Free lipophilic hormone diffuse across the plasma membrane and/or the nuclear membrane to interact with intracellular receptors
2. DNA binding activates specific genes and produces mRNA
3. The hormone receptor complex binds to the hormone response element within the DNA
4. The mRNA binds to a ribosome and proteins are synthesized
5. The mRNA leaves the nucleus
6. The synthesized proteins lead to the cellular response of the hormone
1
3
2
5
4
6
39
T/F
Neurotransmitters belong to the nervous system, and hormones belong to the endocrine system
True!
40
T/F
Hormones are transported across a synaptic cleft
False!
Neurotransmitters are transported across a synaptic cleft; hormones are transported by the blood
41
___ are produced by endocrine glands, ___ are produced by neurons
hormones; neurotransmitters
42
T/F
Hormones must only travel a short distance, while neurotransmitters can travel a long distance
False!
Hormones can travel a long distance, whereas neurotransmitters can only travel short
43
T/F
endocrine responses are fast
False!
They are quite slow
Mins to hours
44
T/F
Nervous control is rapid in response
True
45
T/F
Nervous control is long, effects can last after stimuli stops
False
That is endocrine control.
Nervous control is brief and ends when stimulus stops
46
T/F
Nervous control is hardwired to one specific target
True!
47
T/F
Endocrine control can apply to many different targets
True
48
Describe the structural elements and location of the pituitary gland
- Small gland
- Divided into two lobes; posterior and anterior
- Located in a bony cavity at base of skull
49
T/F
The two pituitary lobes have no communication with each other
True
50
What is the posterior pituitary gland comprised of? What is its other name
Comprised of neural-like tissues called the neurohypophysis
51
What is the anterior pituitary gland comprised of? What is its other name?
Comprised of glandular epithelial tissues, also called the adenohypophysis
52
What is a common function of the two anterior pituitary lobes?
Both release hormones that regulate the functions of other endocrine glands or organs
53
How is the posterior pituitary lobe connected to the hypothalamus?
Through neural pathways
54
How is the anterior pituitary lobe connected to the hypothalamus?
By a vascular link called the hypothalamic-hypophyseal portal system
55
Hormones of the posterior pituitary gland and produced where?
In the neuron cell bodies in the hypothalamus
56
How do posterior pituitary gland hormones get to the posterior pituitary?
They are packaged in vesicles and transported down the axons to the nerve endings in the posterior pituitary
57
What are the two hormones released from the posterior pituitary?
Vasopressin
Oxytocin
58
What is the other name for vasopressin?
Antidiuretic hormone (ADH)
59
What are the functions of vasopressin
Enhances the retention of water by the kidneys
Causes contraction of arteriolar smooth muscle
60
What are the functions of oxytocin?
Stimulating contraction of uterine smooth muscle cells during childbirth
Promoting milk ejection during breastfeeding
61
T/F
All hormones synthesized by the posterior pituitary are peptide hormones
False!
All hormones synthesized by the anterior pituitary are peptide hormones
62
Describe tropic hormones
Hormones that once released, stimulate other endocrine glands to release their hormones
63
T/F
The anterior pituitary gland both synthesizes and releases peptide hormones
True
64
What are the 6 hormones of the anterior pituitary?
Growth Hormone
Adrenocorticotropic Hormone
Luteinizing Hormone
Thyroid-Stimulating Hormone
Follicle Stimulating Hormone
Prolactin
65
What is the growth hormone also known as (abbreviation/other name)
GH
Somatotropin
66
What are the functions of growth hormone?
Responsible for regulating overall body growth
Involved in metabolism
67
What is adrenocorticotropic hormone also known as (abbreviation/other name)
ACTH
Adrenocorticotropin
68
What are the function(s) of ACTH?
Stimulates secretion of cortisol by the adrenal cortex
69
LH stands for what hormone?
Luteinizing hormone
70
What does LH do in females?
Stimulates the secretion of estrogen and progesterone from the ovaries
Is responsible for ovulation and formation of the corpus luteum
71
What does LH do in males?
Stimulates the release of testosterone from the interstitial cells of Leydig
72
What is thyroid-stimulating hormone also known as? (abbreviation/other name)
TSH
Thyrotopin
73
What are the function(s) of TSH?
Stimulates the release of thyroid hormones from the thyroid gland
74
What is the abbreviation of Follicle-stimulating hormone?
FSH
75
What is the function of FSH in females?
Stimulates the grown and development of ovarian follicles and promotes secretion of estrogen by the ovaries
76
What is the function of FSH in males?
Is required for sperm production
77
What is the abbreviation for prolactin?
PRL
78
What is a unique characteristic of Prolactin compared to the other 5 hormones of the anterior pituitary
It is the only anterior pituitary hormone that is not tropic
79
What is the function of prolactin in females?
Enhances breast development and milk production
80
What are the 7 Hypothalamic Hormones?
Thyrotropin-Releasing Hormone
Gonadtropic-Releasing Hormone
Growth Hormone Inhibiting hormone
Corticotropin - releasing hormone
Growth hormone releasing hormone
Prolactin releasing hormone
Prolactin inhibiting hormone
81
What is the abbreviation and function of Thyrotropin releasing hormone?
TRH
Stimulates the release of TSH and prolactin
82
What is the abbreviation and function of Gonadotropin releasing hormone?
GnRH
Stimulates the release of FSH and LH
83
What is the abbreviation and function of Growth hormone inhibiting hormone?
GHIH
Inhibits the release of growth hormone and TSH
84
What is the abbreviation and function of corticotropin releasing hormone
CRH
Stimulates the release of ACTH
85
What is the abbreviation and function of growth hormone releasing hormone?
GHRH
Stimulates the release of growth hormone
86
What is the abbreviation and function of prolactin releasing hormone?
PRH
Stimulates the release of prolactin
87
What is the abbreviation and function of prolactin inhibiting hormone?
PIH
Inhibits the release in prolactin
88
How does the hypothalamus control its release of hormones
- Able to sample and monitor blood
- Receives input from brain areas involved in stress and emotion
89
Describe the general chain of command of hypothalamic hormones
Hypothalamic neuro-secretory neuron
(hormone released)
Anterior pituitary
(hormone released)
Target endocrine gland
(hormone released)
Target cells
90
T/F
Hypothalamic hormone release is under neuronal control
False
It can be influenced by both neuronal and hormonal influences
91
Describe the location of the thyroid gland
- Located over the trachea, below the larynx
92
Describe the structure of the thyroid gland
Consists of two lobes connected by a thin section of the gland called the isthmus
93
Describe the function of the thyroid
To produce and secrete hormones
94
What are the secretory cells of the thyroid gland called?
Follicular cells
95
How are the follicular cells arranged?
Arranged to form hollow spheres
96
What are C cells?
They secrete calcitonin within the thyroid gland
97
That is the substance that fills the inside of the follicles called?
The colloid
98
What is the colloid made of? What is its function?
Made of thyroglobulin, is where the thyroid hormones are synthesized and stored
99
From which amino acid are thyroid hormones produced from?
Tyrosine
100
T/F
Thyroid hormones contain fluorine
FALSE
They contain iodine.
U were close. But not close enough
101
What are the two hormones that the thyroid produces?
T3 and T4
102
How do T3 and T4 differ?
Differ in their speed and intensity of action
T3 contains 3 iodine molecule, whereas T4 contains 4.
T4 represents 90% of the thyroid hormones secreted
T3 is the most active though
103
How does iodine circulate within the body?
Circulates as Iodide
104
How is iodide taken up by follicular cells?
Through a process called iodide tapping
Iodide is driven against its concentration gradient using a Na+-cotransporter that moves Na+ down its concentration gradient
105
What is iodide organification?
The conversion of iodide to idodine
106
The attachment of one iodine to a tyrosine molecule creates what?
With two iodine molecules?
monoiodotyrosine (MIT)
Diiodotyrosine (DIT)
107
T/F
One MIT and one DIT creates T3
True!
108
T/F
Two MITs create T4
False!
There is no coupling of two MITs
T4 is created by two DITs coupling
109
How do thyroid hormones impact metabolic rate and heat production?
- Thyroid hormone increases basal metabolic rate by increasing oxygen consumption and energy expenditure
- A natural consequence of this increase is increased heat production
110
How do thyroid hormones affect intermediary metabolism?
- Thyroid hormone influences the enzymes involved in fuel metabolisms
111
How does a low concentration of thyroid hormone affect intermediary metabolism
- conversion of glucose and glycogen and protein synthesis are favoured
112
How does a high concentration of thyroid hormone affect intermediary metabolism?
- thyroid hormone causes the breakdown of glycogen to glucose and the degradation of proteins
113
Describe the thyroid's hormones sympathomimetic functions
Thyroid hormone can increase a target cell's response to catecholamines by increase the number of catecholamine receptors
114
How are thyroid hormones released?
The follicular cells engulf part of the thyroglobin-containing colloid and create hormone filled vesicles, which are degraded by lysosomes, releasing all of the MIT, DIT, T3 and T4 from the thyroglobin.
The T3 and T4 immediately cross into the blood
115
Describe how thyroid hormones affect the cardiovascular system
They can increase both heart rate and strength of contraction to increase cardiac output
They also increase blood volume and flow
116
Describe how thyroid hormone affects growth
- Stimulates the release of GH and insulin-like growth factor
117
If there is little TSH, thyroid glands do what?
They shrink in size
118
If there is excess TSH, thyroid glands do what?
The thyroid gland follicles get larger and increase in number
119
What is hypothyroidism?
Low thyroid or under-active thyroid
120
Why does primary failure of the thyroid gland occur?
Antibodies target the thyroid gland and impair its ability to produce thyroid hormones
121
What characterizes primary failure of the thyroid gland occur?
Low levels of T3 and T4, but elevated levels of TSH
Occurs because no T3 or T4 being produced to provide negative feedback and decrease the production of TRH and TSH
122
Why does secondary failure of the thyroid gland occur?
Occurs when the hypothalamus/pituitary fail to secrete adequate TRH/TSH
123
What characterizes secondary failure of the thyroid gland?
Low levels of T3/T4 as well as TRH/TSH, depending on the location of the function
124
What characterizes an inadequate dietary supply of idodine?
Low T3 and T4 levels and elevated TSH
125
T/F
Primary failure of the thyroid gland is the most common type of hypothyroidism
False
Inadequate dietary supply of iodide is the most common cause
126
What is cretinism? What is its symptoms?
Thyroid hormone deficiency acquired from birth
Dwarfism and intellectual disability
127
What are the 6 common symptoms of hypothyroidism?
- Cold intolerance
- Slower reflexes
- Reduced mental alertness
- Easy to fatigue
- Slow, weak heart rate
- Weight gain due to decreased basal metabolic rate
128
What is hyperthyroidism?
Increased levels of thyroid hormone
129
What are the effects of a tumor in the hypothalamus or anterior pituitary
- Either increased TRH or TSH secretion
- Tumors ignore the negative feedback, resulting in elevated T3 and T4, as well as elevated TRH/TSH
130
What are the effects of a thyroid gland tumor
- Results in an increased secretion of thyroid hormones
- Observed as elevated T3 and T4 and decreased TSH
131
What is Graves' Disease?
Most common cause of hyperthyroidism
Body produces an antibody that targets and activated TSH receptors on follicular cells
132
What is Graves' Disease characterized by?
High levels of T3 and T4 and low levels of TSH
133
What are the 5 common symptoms of hyperthyroidism?
- Increased heart rate
- Excessive heat production
- Muscle weakness due to skeletal muscle protein degradation
- Mood swings due to increased CNS mental awareness
- Elevated basal metabolic rate that causes weight loss
134
What is a goiter?
An enlarged thyroid gland
135
What causes a goiter?
Any condition that leads to increased TSH
136
T/F
Goiters can arise from both hypothyroidism and hyperthyroidism
True
- It is anything that leads to increased TSH
137
Where are the adrenal glands located?
At the top of the kidneys
138
Where is the adrenal cortex located?
Is the outer layers of the adrenal gland
139
What kind of hormone does the adrenal cortex secrete?
steroid hormones
140
What is the inner layer of the adrenal gland called?
The medulla
141
What kind of hormones does the adrenal medulla secrete?
catecholamines
142
The adrenal cortex can be divided into what 3 distinct zones?
- The zona glumerulosa
- The zona fasciculata
- The zona reticularis
143
What are the three main categories of adrenal cortex hormones?
Mineralocaroticoids
Glucocorticoids
Sex homes
144
What do mineralocorticoids influence?
Influence mineral (electrolyte) balance
145
Where are mineralocorticoids produced?
Produced mainly in the zona glomerulosa
146
What do glucocorticoids influence?
Play a role in glucose, lipid, and protein metabolism
147
Where are glucocorticoids produced?
Mainly in the zona fasciculata and the zona reticularis
148
Where are the sex hormones produced?
Produced in the gonads, and in lower quantities in the zone fasciulata and the zona reticularis
149
Aldosterone is a major hormone under which of the three adrenal cortex hormones?
Mineralcorticoid
150
What is the primary glucocorticoids?
cortisol
151
What are the metabolic affects of cortisol?
- Stimulates gluconeogenesis
- Stimulates protein degradation
- Inhibits glucose uptake
- Breaks down lipid stores to mobilzie free fatty acids that can be used as a fuel source
152
What is gluconeogensis?
Production of glucose from non-carbohydrate precursors, amino acids
153
How does cortisol play a role in stress?
Cortisol causes a shift away from protein and fat stores while increasing carbohydrate stores, which allows for increased availability of glucose ensures adequate brain activity
154
For cortisol secretion, the hypothalamus secretes ___ which causes then anterior pituitary to secrete ___
CRH; ACTH
155
The ACTH stimulates the adrenal glands to ___ cortisol
reduce
156
T/F
Cortisol secretion is highest in the evening and lowest in the morning
False
It is highest in the morning and lowest at night
157
T/F
Stress leads to a large increase in CRH release from the hypothalamus
True
158
What is the "male" sex hormone secreted from the adrenal cortex?
Androgen
159
What is the "female" sex hormone secreted from the adrenal cortex?
Estrogen
160
What is DHEA? What is its role?
An important adrenal cortex hormone
In females: is important for growth of pubic and armpit hair, enhancement of the growth spurt at puberty, or maintenance of the female sex drive
161
T/F
Adrenergic receptor B1 is excitatory
True
162
T/F
Adrenergic receptor B2 Is inhibitory
True
163
T/F
Adrenergic receptor A1 are found presynaptically
False
They are found postsynaptically
164
Adrenergic receptor A2 is found presynaptically
True!
165
Is A2 excitatory or inhibitory. What about A1?
A1 is excitatory
A2 is inhibitory
166
What are the effects of epinephrine on metabolism?
-Increases blood glucose
-Enhances liver gluconeogensis
- Stimulates glycogenolysis in skeletal muscle
- Promotes lipolysis to increase circulating free fatty acids
167
What is glycogenolysis?
Breakdown of glycogen to glucose
168
How are insulin and glucagon impacted by stress?
- Increase in blood sugar
- Increased glucagon secretion will break down glycogen stores to produce glucose and decreasing insulin secretion will reduce the rate at which glucose is removed from the circulation
169
How does ACTH play a role in stress?
It resists stress
170
How does the Remin-Angiotensin-Aldosterone system play a role in stress?
Increases blood pressure
171
Provide a summary of the integrated stress response (don't answer, just read)
Once the hypothalamus receives input concerning physical and emotional stressors, it activates the sympathetic nervous system, secretes CRH to stimulate ACTH and cortisol release, and triggers release of vasopressin.
Activation of the sympathetic nervous system brings about the secretion of epinephrine which influences secretion of insulin and glucagon
Vasoconstriction due to catecholamine release means less blood flow to the kidneys, setting the renin-angiotensin-aldosterone system in motion
Through these mechanisms, the hypothalamus is able to integrate the responses of the sympathetic and endocrine systems in times of stress
172
What is hyperaldrenalism?
Refers to conditions in which the adrenal glands secrete excessive amounts of the hormones they produce
173
Describe cortisol hypersecretion
Occurs due to the overstimulation of the adrenal cortex by CRH/ACTH or adrenal tumors hypersecreting cortisol independent of ACTH, and ACTH-secreting tumors located other than the pituitary
174
Buffalo hump and moon face are a physical characteristic of which pattern of hyperadrenalism?
Cortisol hypersecretion
175
hyperaldesteronism is what?
Excessive secretion of aldosterone
176
What are the symptoms of hyperaldesteronism?
Excess Na+ retention, K+ depletion, and high blood pressure
177
Describe primary adrenocortical insufficiency
Occurs when all the layers of the adrenal cortex are under-secreting
Often caused by autoimmune destruction of the cortex
178
How can primary adrenocortical insufficiency affect the body?
Both aldesterone and cortisol are deficient
Patients display hyperkalemia, which affects cardiac rhythms
Display hypoatremia, which causes hypertension
179
Describe secondary adrenocortical insufficiency
- Occurs if there is a problem in the hypothalamus or anterior pituitary
- Characterized by reduced ACTH and cortisol deficiency
180
What are common symptoms of secondary adrenocortical insufficiency?
Severe fatigue, loss of appetite, weight loss, nausea, vomitting, muscle weakness, irritability
181
Describe anabolic reactions
Leads to the synthesis of larger organic macromolecules from smaller subunits
- Useful for repair, growth, and storage
182
Describe catabolic reactions
The breakdown of larger organic macromolecules either through the process of hydrolysis or oxidation
183
How is excess glucose stored?
In the liver and skeletal muscle as glycogen
Once glycogen stores are full, any additional glucose is converted into free fatty acids and glycerol
184
How are excess fatty acids stored?
As triglycerides
185
How are excess amino acids stored?
They are not stored, but rather used fro structural proteins or are converted into glucose and fatty acids
186
Describe the absorptive state
Anabolism dominates
Simple carbohydrates are converted in the liver to glucose
Ingested fats and proteins are either immediately used or stored
187
Describe the post-absorptive state
Several hours after ingesting food
Catabolism dominates
Glycogen stores in the liver and skeletal muscle become the primary energy source
188
Describe the purpose of glycerol
An energy source
Comes from the backbone of triglycerides when broken down
Converted to glucose by the liver
189
Describe the purpose of lactic acid
Formed by glycolysis
Can be converted to glucose by the liver
190
Describe the purpose of ketone bodies
Produced in the liver in times of glucose shortages
Acetyl-CoA is formed through oxidation of free fatty acids which are converted into ketone bodies
191
What are the islets of Langerhans?
The clusters of cells found throughout the pancreas. There are 4 major types
192
What are the 4 major cells in the islets of Langerhans?
Alpha cells
Beta cells
Delta cells
PP cells
193
What is the purpose of alpha islets of langerhans?
Produce and secrete glucagon
194
What is the purpose of beta islets of langerhans?
Produce and secrete insulin
195
What is the purpose of delta islets of langerhans?
produce and secrete somatostatin
196
What is the purpose of PP islets of langerhans?
Secrete pancreatic polypeptide; may play a role in reducing appetite
197
What is somatostatin?
Slows down the digestive system to inhibit digestion and absorption of nutrients
Can be released by the hypothalamus where it inhibits the secretion of growth hormone and TSH
198
Describe insulin
Small peptide hormone
Dominant hormone in the absorptive state and plays a role in anabolism
199
Describe 4 ways insulin affects carbohydrates
increase uptake of glucose into cells
Inhibits glycogenolysis in the liver
Stimulates glycogenesis in skeletal mucle and in the liveer
Inhibits gluconeogenesis in the liver
200
What are factors that increase blood glucose
Glucose absorption in the digestive tract
Glycogenolysis of glycogen
Gluconeogenesis
201
What are factors that decrease blood glucose?
Transport of glucose into cells
Urinary excretion of glucose
202
What effects does insulin have on Fats?
- Lowers blood free fatty acids and promotes storage as triglycerides
- Inhibits lipolysis
203
What effects does insulin have on proteins?
Promotes the uptake of amino acids
Enhances activity of enzymes involved in protein synthesis
Inhibits degradation of proteins
204
What is the difference between osteoblasts and osteoclasts?
Osteoblasts deposit new bone
Osteoclasts dissolve bone
205
Describe IGF- 1
Release primarily in liver
Mediates most of the growth promoting actions of GH
206
Describe IGF - II
- Important during fetal development
- Not stimulated by GH
207
Describe the structure and location of the parathyroid
4 small glands located on the back of the thyroid gland
208
What is the primary purpose of the parathyroid?
To raise plasma calcium levels
209
Describe calcitonin
Secreted from the thyroid gland
Actions are opposite from PTH
Acts on osteoclasts to decrease their activity
210
What is the main function of vitamin D?
Increase the intestinal absorption of calcium
211
How does PTH affect the bones?
Enhances osteoclast activity and inhibits osteoblast activity
212
How does PTH affect the kidney?
Stimulates the reabsorption of calcium, to remove PO4- and to activate vitamin D
213
As calcium levels lower, secretion of PTH ___?
Increases
