week 2 endocrine Flashcards
(238 cards)
1
Q
What is homeostasis?
A
The regulation and maintaining of a constant internal environment, despite changing conditions
2
Q
Is homeostasis the same as equilibrium?
A
NO, as the ion concentration is not in equilibrium when our body is in steady state
3
Q
What is dynamic steady state
A
Ions moves between extra and intra cellular fluid, until a steady state is reached
4
Q
What is feedback control
A
It is a way to maintain homeostasis
It occurs when our body is not in the set point
5
Q
What is a setpoint?
A
It is the normal range of function for our body. When pass the normal range, feedback response is activated to bring our body back to setpoint range
6
Q
what is negative feedback
A
It is a mechanism to maintain homeostasis
When our body is back to steady state negative feedback loop turn off the response loop
7
Q
What is positive feedback
A
It is a feedback loop for change, opposite to homeostasis
It further stimulate and reinforce the response, until a outside factor turns off the loop
Doesn’t occur often
8
Q
When is outside factor needed to turn off a loop?
A
For a positive feedback loop
9
Q
What is the regulation of cortisol secretion
A
negative feedback, upstream suppress
10
Q
How is cortisol released
A
Hypothalamus release CRH stimulating hormone, which stimulate anterior pituitary to release ACTH stimulating hormone, which stimulate adrenal cortex to release cortisol to target tissue
11
Q
How is cortisol secretion regulated
A
When enough cortisol is made, it inhibits the release of ACTH and CRH through upstream suppress, so release of cortisol is stopped, and homeostasis can be achieved
12
Q
What type of feedback loop is the release of oxytocin and control of uterine contraction? How does it occur
A
Positive feedback loop
Baby drop lower in uterus stimulate the start of child birth, which cervical stretch stimulate oxytocin release. Oxytocin cause uterine contraction, which push baby against the cervix, causing cervix stretch, which further stimulate oxytocin release. A reinforcement loop
Stop until the baby is delivered
13
Q
What are the three types of local control of intercellular communication
A
Gap junction, contact dependent, and autocrine
14
Q
What is gap junction
A
It forms direct cytoplasmic connections between adjacent cells, allowing the movement of small ions/ molecules
15
Q
What is contact dependent local control
A
It is the bind of membrane proteins between two adjacent cells, allowing signal to be passed through the interaction of membrane molecules on two cells
16
Q
What is autocrine?
What is autocrine VS paracrine signal
A
It is the movement of molecules (signal) through interstitial fluid in a short distance
Autocrine signal: act on the same cell that secrete the signal
Paracrine: signal diffuse and act on adjacent cells
17
Q
What are the two main type of signals for long distance communication
A
Electrical signal that pass through neurons, chemical signal that travel through circulatory system
18
Q
What are the two main systems for long distance communication, and what is used by them as signals?
A
Endocrine system, using hormone
Nervous system using neurotransmitters and neurohormones (neuroendocrine)
19
Q
What is the mechanism of the three main signals/ molecules for long distance communication
A
Hormone: secreted by endocrine gland /cells into blood, only act on target cells with corresponding receptors
Neurotransmitter: chemical secreted by neuron that diffuse through a small gap to the target cell
Neurohormones: Chemicals that is released by neurons into blood, act on distant target with corresponding receptors
20
Q
What is reflex?
A
Long distance communication, which is mediated by a number of different factors
21
Q
What is simple VS complex reflex?
A
Simple: mediate by either endocrine or nervous system only
Complex: mediate by both systems, and go through serval integrating system
22
Q
What is the mechanism of local control VS complex control
A
The goal for both is to maintain homeostasis
Local: local change occurs, and local cells initiate local responses
Reflex: response is controlled by cells at distant sites
Big systematic change is sensed by numbers of different areas, which send message to brain, Brain initiate a response, and a reflex response is initiated by cells at distant site
23
Q
What is central VS peripheral receptor?
A
Central : in or close to the brain, such as eyes, nose, ears and tongue
Peripheral: lie outside brain, such as temperature change, pressure, pH, etc
24
Q
What are the two type of sensor for homeostatic reflex pathway
A
Specialized cells or structure, which convert stimulus to electrical signals
Cell membrane/ intracellular receptor protein
25
What type of reflex is insulin release
It is a simple endocrine reflex
26
What is the specificity of neural VS endocrine relex
Neural: each neuron terminate a single/ limited number of adjacent target cell
Endocrine: most cells are exposed to hormone, but only cells with receptor can response
27
What is the speed of endocrine VS neural reflex
Neural: very rapid
Endocrine: much slower, speed depends on the type of hormones
28
What is the duration of action of neural VS endocrine reflex
Neural: usually very short
Endocrine: usually longer
29
What is the intensity of stimulus for neural and endocrine reflex
Neural: signals are identical in strength, intensity of signal depends on the frequency
Endo: intensity depends on amount of hormone released (concentration)
30
What is exocrine
Substances are excreted to the external relative to self, such as sweat, digestive enzyme
31
What is hormone and endocrine
Endocrine is secreting substances inside
Hormone is chemical secreted by endocrine into the bloodstream
32
What is primary VS secondary endocrine organs
Primary: Main function is to release hormones
Secondary: Has some other primary functions beside releasing hormones
33
Is heart a endocrine organ?
Some cell types on heart has endocrine function, but the whole heart is not a endocrine organ
secondary endocrine organ
34
Can hormone act on multiple tissues?
Yes, as long as the tissue has the receptor
35
How is hormone transported?
Through blood to distant targets
36
Does the hormone action last forever?
No, it must be terminated, turn off through negative regulation
37
What are the main functions of hormone?
1: maintain homeostasis
2: initiate change in body if positive feedback
38
How are hormone identified in today?
Purify hormone extract and test in biological assay
39
In term of physical property, what are the two main classification of hormones?
Hydrophilic: water soluble hormone, ca dissolve in plasma
lipophobic, cannot cross plasma membrane
Hydrophobic: not water soluble, cannot dissolve in plasma
lipid soluble, can cross plasma membrane
40
How does hydrophilic and lipophilic hormones cross membrane and travel in blood?
Hydrophilic: cross membrane through vesicles, dissolve in plasma and free flow
Lipophilic: Diffuse through plasma membrane, travel in blood in carrier protein
41
What type of hormone is peptide/ protein hormone
Hydrophilic
42
What type of hormone is steroid?
Hydrophobic
43
What type of hormone is catecholamine?
hydrophilic
44
What type of hormone is thyroid hormone?
Hydrophobic
45
How id hydrophilic VS phobic hormone synthesized and released?
Hydrophilic: synthesis in advance, store in vesicles and release through exocytosis
Hydrophobic: Synthesis on demand, and release through diffusion
46
Base on biochemical property, what are the 3 types of hormones
1: Peptide/ protein hormone (3 or more amino acids)
2: steroid ( derived from cholesterol)
3: Amine/ monoamine ( single amino acids)
47
What type of hormone is insulin in term of biochemistry
Peptides
48
What type of hormone is catecholamines? in term of biochemistry
Monoamine
49
What type of hormone is estrogen (sex hormones) in term of biochemistry
steroid
50
What type of hormone is cortisol in term of biochemistry
steroid
51
What type of hormone is most type of hormones?
Peptide/ protein hormone
52
What is the length of half life of peptide protein in plasma
Short
53
How is peptide hormone synthesis, packaged and relase?
In the ER, preprohormone is made through translation of mRNA by ribosome
The signal sequence is cleaved off to form prohormone
Prohormone travel to golgi complex through vesicles, and is further processed and cleaved
The active hormone is then formed, and is released to blood upon signal, and travel to target
54
What are the two types of things that preprohormone can contain? (what can be on the single long chain of preproohormone protein)
1: Contain several copies of the same hormone, along with other peptides and signal sequence
2: Contain more than one type of hormone, along with other peptide fragments
55
What determine what active peptide hormone is released? (how is it cleaved )
The specific proteolytic processing enzyme, as well as the cell type
56
How is insulin processed?
Proinsulin contain disulfide bond, which keep molecules intact
The c-peptide is cleaved off from proinsulin to form active insulin
57
What is one way to measure insulin release, that does not involve the actual insulin hormone
Measure C-peptide levels
58
How is steroid made?
Synthesized from cholesterol only, and is made on demand
59
Why is steroid made on demand?
If it is made in advance, it can leak out of the cell
60
What is the length of half life of steroid
Long
61
How does steroid reach target cell
Through diffusion into cells, or endocytosis of steroid hormone carrier proteins
62
Where is the receptor of steroid
Cytoplasm, or nucleus receptors
It can also act on membrane receptor
63
How is different steroid made?
Same cholesterol form different steroid, depending on enzyme and cell type
64
What steroid is made in ovaries?
Estrogen
65
What steroid is made in adrenal cortext
Aldosterone (retain water)
Cortisol (long term stress)
66
What is used to make amine hormone
Only from tryptophan or tyrosine
67
What is melatonin made from? what type of hormone does it behave like
From tryptophan, behaves like peptide or steroid depending on receptor
68
What is catecholamine made from? what type of hormone does it behave like
Tyrosine, behaves like peptide
69
What is thyroid hormone made from? what type of hormone does it behave like
tyrosine, behaves like steroid
70
Where is melatonin made in?
Pineal gland that is deep in brain
71
How does the same tyrosine make different hormones?
Catecholamine or thyroid hormone is made depending on the location
Different endocrine gland, different enzyme
72
Where is catecholamine made?
Adrenal medulla
73
Where is adrenal mendulla?
In the middle of the adrenal gland
74
What is an important catecholamine
Adrenaline (epinephrine), convert from tyrosine through a numbers of different enzymes
75
How is hormone release controlled? (how does the release happen)
Endocrine cells directly sense stimuli, which can be other hormone from complex reflex pathway, then secrete the hormone
76
How does glucose stimulate insulin release
Glucose bind to glut2 receptor, trigger signalling cascade inside a pancreatic beta cell, which eventually increase ATP level in cell
ATP blocks ATP sensitive potassium channel, reduce outflow of K+, making the cell more +ve
This change MP and depolarization, open voltage gated calcium channel
Ca2+ influx signal insulin release through exocytosis
77
Why is hypothalamus and anterior pituitary important?
They release hormones that regulate (stimulate) the release of several other hormone
Hypothalamus-->anterior pituitary-->peripheral endorcrine gland
78
How is hypothalamus and anterior pituitary stimulated hormone release regulated?
-ve feedback loop
When target response is reached, peripheral gland hormone inhibit anterior pituitary and hypothalamus, and anterior pituitary also inhibit hypothalamus
79
What is anterior VS posterior pituitary
Pituitary gland is made up from two different tissue
Anterior is endocrine gland that actually release hormone
Posterior is not endocrine gland, it can only release hormone, not making hormone
80
What is hormone interaction
Most cells are sensitive to more than one hormone, so interactive effects is exhibited
81
What is synergistic effect
Multiple hormones act together for greater effect
82
What is permissive effect
One hormone enhance the target organ's response to another later hormone, "permit" the 2nd hormone to work
83
What is antagonistic effect
One hormone oppose the effect of another hormone
84
What happen when the concentration of ligand keep increasing
The receptor will be saturated, no more receptor bidning
85
What are the four properties of receptor?
High affinity to ligand
Saturable
reversible
Specific
86
How is intracellular signal receptor response operated?
Lipophilic signal diffuse through cell membrane, bind to intracellular receptor (cytosolic/ nuclear), trigger slower response related to gene activity (synthesis of target protein)
87
How is extracellular signal receptor responses operated?
Extracellular signal molecules bind to membrane receptor, trigger responses in cell through signalling pathway, showing rapid cell response (modification of existing target protein)
88
What are the two main type of receptors? (location wise)
Intracellular (bind lipid soluble hormone), cytosolic or nuclear, directly alter gene transcription
Plasm membrane receptor
89
How does peptide hormones act on receptor?
It cannot pass through membrane, so it binds to surface receptor and activate intracellular processes through second messengers (signalling cascade)
90
How does steroid hormone act on receptor
Pass through membrane and bind to internal receptor (nucleus)
Influence gene expression (alter gene transcription), slow effects
91
What is hormone response element
Specific DNA sequences,
When hormone-receptor complexes translocate into nucleus, and bind to the HRE on the DNA, either activate or inhibiting gene transcrpition
92
What type of receptor is GPCR?
membrane receptor
93
What are the 4 types of membrane receptor
receptor channel
GPCR
receptor enzyme
integrin receptor
94
What can happen when ligand bind to GPCR (very general)
Open ion channel/ alter enzyme activity
95
What happen when ligand bind to receptor enzyme (very general)
activates intracellular enzyme
96
What happen when messenger bind to receptor ion channel
The channel is open, and ions can move through, altering the cell's electrical properties
97
What type of protein is GPCR
A very large 7 membrane spanning proteins, which cytoplasmic tail links to the G-protein
98
What system is used by G-protein for signal transduction
G protein coupled adenylyl cyclase cAMP system
99
WHat are the two secondary messenger used by GPCR? (G alpha q)
DAG and IP3
100
What happen when Gs is activated?
When ligand bind to GPCR, G alpha unit exchange GDP to GTP
GTP bound alpha subunit move to adenylate cyclase, which activate cAMP using ATP
cAMP activates PKA, which phosphorylate downstream protein, leading to cell response
101
How does cAMP amplify target cell response
One signal binding to GPCR leading to the activation of adenylate cylase through G Protein, which is an amplifier enzyme that converts ATP to cAMP
cAMP further activates PKA, whcih phosphorylate other proteins
This starts from a single signal, and ends up with massive cell responses
102
What happen when Gq is activated
Upon GCRP binding, Gq will be activated
Gq activate PL-C (phospholipase C), which convery phospholipids into DAG and IP3
DAG remain in the membrain, and activate PK-C, which phosphorylate downstream proteins
IP3 diffuse in to cytoplasm, and cause the release of Ca2+, which create Ca2+ signal and trigger cell response
103
What are the two amplifier in GPCR pathway
Adenyl cyclase and PL-C
104
what is GaI?
Inhibitory regulative G protein, which inhibit adenyl cyclase
No cAMP will be produce
105
What are the 3 main types of G protein, and their target, and their activity on target
1: Gs, stimulate adenyl cyclase
2: Gq, stimulate PL-C
3: Gi, inhibit adenyl cyclase
106
What receptor mediate fight or flight responses? What do they respond to
GPCR, in response to epinephrine
107
What is the fight or flight response on liver
Increase glucose release, which is used for energy
108
What is the fight or flight response on fat
Increase fatty acid release, which is used for energy
109
What is the fight or flight response on heart
Increase muscle contraction, so heart beat faster, and more blood is sent
110
What is the fight or flight response on skeletal muscle
Decrease vasoconstriction, so more blood flow
111
What is the fight or flight response on intestine, skin or kidney
Increase vasoconstriction, so blood flow is limited
112
What is the general blood flow pattern under Fight or flight response
More blood flow to organs that are important for F or F, less blood flow to less important organ
113
What is the effect of binding epinephrine to alpha-receptor
a-receptor is on intestinal blood vessel, so vessel constrict
114
What is the effect of binding epinephrine to beta2-receptor
B2-receptor is found on skeletal muscle blood vessels, so vessel dilate
115
What G protein is related to a1-receptor, in term of epinephrine bidning
Gq
116
What G protein is related to a2-receptor, in term of epinephrine bidning
Gi
117
What G protein is related to b1/b2-receptor, in term of epinephrine bidning
Gs
118
What is down regulation VS up regulation
Down: not sensitive to response, so inhibiting receptor activity
Up: increase receptor activity
119
What is receptor desensitization
Making the receptor less sensitive to hormone
120
How to turn on/ off receptors through membrane recycling?
After ligand binds to membrane receptor, the ligand receptor complex is endocytose in cell, trapping the receptor inside, turning it off
Receptor and ligands are separated, and the ligand is sent to lysosome or golgi
When receptor is needed, vesicles transport the receptor to the cell membrane, and exocytose it to the membrane, now the receptor is recycled and can bind to new ligand
121
How does epinephrine cause diverse responses in our body
Through binding to different receptors
122
What are the 3 locations of calcium
Extracellular matrix, extracellular fluid and intraceullar
123
Where is mostof the calcium located?
99% in bone
124
What happen to excess calcium
Move from cell to extracellular fluid, then move to kidney and output through urine (remove)
124
What happen to dietary calcium intake
Absorb in small intestine, transport through extracellular fluid to bone
125
Is bone static?
No, it is living tissue that is constantly formed and resorbed
126
What is the main form of calcium in tissue
In crystals, called hydroxyapatite, which is a calcium phosphate complex
Small fraction is ionized, and is exchangeable
127
What are the 3 cells that are responsible for bone formation and maintenance
1: Osteoblast for bone formation
2: Osteoclast for breaking down bone
3: Osteocytes for bone maintenance
128
What is osteocytes?
It is previously osteoblasts, that got trapped inside the bone matrix
It lost building ability, so only for maintenance
129
What is calcium turnover in bone, at the age of 0 VS adult
Infant: 100%
Adults: 18%, still active
130
What is the size of osteoclast?
It is large, as it is a fusion of multiple cells, multinucleated
131
How does bone resorption work?
Osteoclast is attached to the bone matrix, and it secrets HCL acid
Low pH will eats away the bone
It also secrets protease that works in low pH
The calcium will then get sent to blood and become part of the free Ca2+ pool
132
What is carbonic anhydrase? How does it work in bone resorption
It is used to produce free proton and bicarbonate
The free proton is used to make HCl by osteoclasts
133
Why is bone remodelling important?
It helps repair old bone with new tissue, as well as address change in Ca2+ need in body
134
Why is osteoclast important, when bone fracture happen (broke bone)
It helps smoothing out and polishing the new grown bone to how it used to look like
135
How is osteoclast formed?
Osteoclast precursor has RANK, which is a receptor activator
By binding the RANK to the RANKL ligand on osteoblast, differentiation and fusion occur, and osteoclast is formed, and bone resorption can occur
136
How to block RANK and RANKL interaction
OPG (osteoprotegrin) is released by osteoblast, which binds to RANKL, blocking RANK RANKL interaction, and osteoclast formation will be inhibited
137
What is Denosumab drug
It is an antibody that mimics the OPG effect, and bind to RANKL
138
What are the 3 hormones that control plasma Ca2+ level
PTH (parathyroid hormone)
Calcitriol
Calcitonin
139
Where is PTH released from
Parathyroid gland (chief cells)
140
What is the function of PTH
Increase plasma Ca2+ concentration
141
What is the stimulus for PTH secretion
Low plasma Ca2+, which is sensed by parathyroid gland
142
What is the sensitivity of parathyroid cells
Extremely sensitive to plasma CA2+ level
As soon as [Ca2+] decrease to a certain point, a spike of PTH is released
143
How does Ca2+ sensing receptor monitor extracellular Ca2+
When there's sufficient Ca2+, it will bind to the GPCR calcium sensing receptor, which inhibits cell growth, reduce PTH synthesis and secretion
When there's no Ca2+ binding, all these inhibition will be off, so PTH will be synthesized and released
144
How does VDR act to inhibit PTH?
VDR binds to vitamin D3, and inhibit PTH synthesis
145
Where does PTH act on?
Directly act on bone and kidney
146
How does PTH act on bone
It acts on the osteoblast, increasing cAMP
Thus increase RANKL and inhibit OPG expression
More osteoclasts are formed, so more bone resorption
147
How does PTH act on kidney
Increase calcium reabsorption from urine to blood
Increase calcitriol synthesis
148
What is calcitriol made from?
From vitamin D3, goes through multiple enzymatic steps
149
What are the 3 organs that are crucial for calcitriol development
Skin, liver, kidney
150
How is calcitriol formed
In skin, vitamin D3 precursor (7-dehydrocholesterol) is converted to vitamin D3( cholecalciferol) using UV ray
In liver, D3 is converted to 25-dehydroxycholecalciferol
In kidney, PTH activate it into active calcitriol, aka vitamin D3 hormone
151
How does calcitriol act
Primary: increase Ca2+ uptake in small intestine, from dietary source
Other: renal Ca2= reabsorption, mobilization from bone
152
What is included in calcium supplement
Calcitriol, which helps better absorbing the calcium
153
What type of hormone is calcitriol in term of physical properties
It is lipophilic so it can diffuse pass plasma membrane and bind to intracellular receptor
154
How does calcitriol act on VDR
It binds to VDR, and the complex will go in nucleus, bind to DNA vitamin D3 response element
This alter the translation, and increase the production of Ca2+ channel, binding protein, transporter in the intestine and kidney, helping absorption
155
How do hormones correct a calcium deficit
Increase PTH release, which increase bone resorption as well as the release of calcitriol
Calcitriol increase kidney calcium reabsorption and absorption of calcium from intestine
156
What is also released when bone is broken down
PO4 phosphate
157
How does PTH control phosphate
PTH increase bone break down, so release phosphate release as well
It decrease phosphate reabsorption in kidney, so excess PO4 can be removed
158
How does calcitriol maintai PO4/
Calcitriol is usually presented in body, and to form bone using Ca2+, PO4 is also required
Calcitriol increase reabsorption of PO4 from kindey, and absorption of PO4 in intestine, so enough PO4 can be presented to form bone
159
Where is calcitonin secreted
C cell
160
What type of hormone is calcitonin, in term of bch
peptide hromone
161
How is calcitonin release triggered?
By high level of calcium in blood, sense this using Ca2+ sensing receptor in C cell
162
What does Calcitonin do?
In tones down calcium level, by reducing osteoclast activity, stimulate osteoblast, and inhibit calcium reabsorption in kidney
163
What is the role of calcitonin in human body?
Possible: protect the skeleton during pregnancy and lactation, by reducing lost of calcium
164
Where is the majority of water in our body
Intracellular fluid, with 2/3 of the water
165
How is the water in extracellular fluid distributed
75% in interstitial fluid, the other 25% in plasma
166
What is water homeostasis?
Water gain from intake and metabolic production, minus the output, equal to zero
167
What happen when there's excessive water loss
The water homeostasis is disrupted, which can cause disease
It leads to less extracellular fluid, resulting in decreased blood pressure
168
What is the consequence of too much water?
Difficulties in breathing and walking
169
Where is urine formed?
Nephron in kidney, by filtration, reabsorption and secretion
170
What happen to the urine mode when there's excess water loss/ (general)
It changes to hold on to more fluid, and to reestablish homeostasis
171
How to get to the amount of solute excreted as urine, from amount filtered
Amount filtered- amount reabsorbed back to blood stream+ amount secreted
172
Why is most filtrate reabsorbed, instead of excreting as urine?
Want to hold on to certain ions, as well as some H2O
173
What is the responsibility of nephron
It is the functional unit in kidney, responsible for filtration, excreting waste, regulate blood volume, control electrolytes and pH of blood
174
Where does blood vessels meet the nephron
Glomerulus
175
What is the significance of kidney to vitamin D
Vitamin D3 hormone is activated by PTH in the kidney
176
What is used to maintain the homeostasis of water
Hormones
177
What are the 3 hormones responsible for regulating water homeostasis
Aldosterone
Vasopressin
Atrial natriuretic peptide (ANP)
178
What type of hormone is vasopressin, in terms of function
Antidiuretic hormone (ADH), used to prevent excess urine formation
179
Where is vasopressin made and secreted?
Made in hypothalamus, secreted in posterior pituitary
180
What are the primary functions of vasopressin?
Increase water reabsorption in kidneys, so water is conserved, fluid homeostasis is maintained, and blood volume/ pressure is increased
Regulating permeability of cells in the kidney, increasing reabsorption and decrease urine formation
181
What are the stimulus for vasopressin release
Main: High plasma osmolarity, detect by osmoreceptors in hypothalamus
Low blood pressure, detect by reduced stretch of walls of heart atria/ aortic and carotid arteries
182
What is the pathway of vasopressin release
Upon stimulus, hypothalamus release ADH vasopressin to posterior pituitary, then it is released and traveled to kidney (nephron), and increase water reabsorption
183
What is plasma osmolarity
How " salty" the plasma is, how concentrated is the ions in blood
184
What happen when plasma osmolarity pass the setpoint
Spike of vasopressin release, as well as the feeling of thirsty
185
How does vasopressin increase water reabsorption
Vasopressin bind to receptor in nephron, that induce cAMP and signalling cascade, which insert aquaporin-2 water pores in the apical membrane facing the filtrate by exocytosis
Water pores allow the absorb of water from filtrate into blood
186
What happen to the urine, when vasopressin is presented
It becomes more concentrated
187
What type of hormone is aldosterone, in term of bch
steroid
188
Where is aldosterone made
Adrenal cortex, zona glomerulosa
189
What are the main functions of aldosterone
Increase Na+ reabsorption, which helps retain H2O, as sodium will pull water
Increase K+ excretion
190
Where does aldosterone act on
Distal tube and collecting duct in kidney
191
How is the synthesis of aldosterone controlled? (what feedback? What is the stimulator? Inhibitor)
Control by -ve feedback
Stimulators: High [K+] in plasma, or renin-angiotensin II via blood pressure
Inhibitor: high osmolarity of extracellular fluid
192
How does aldosterone act? (mechanism of action)
Aldosterone diffuse in from blood to nephron
Combine with cytoplasmic receptor, and initiate the transcription in nucleus
Translation and protein synthesis make new protein channel and ATP pumps
Channels are on apical membrane for K+ secretion and Na+ reabsorption
Pumps are on the basal membrane facing the blood, pump 3 Na+ out (to the blood), 2 K+ in (away from blood)
Also prevents the degradation of apical Na+ channel
193
For the nephron, what does the apical membrane face? What about basal
Basal: facing blood (outside nephron is blood)
Apical: facing the filtrate
194
Where is renin secreted from?
Renal juxtaglomerular cells, which is sensitive to blood pressure, since they are right next to blood vessels
195
When is renin secreted
When blood pressure drops
196
What is the renin-angiotensin-aldosterone pathway
When blood pressure drops, renin is secreted by kidney, which meet the angiotensinogen precursor protein, secreted by liver
Precursor protein is cleaved to another precursor protein (angiotensin 1), which meets the angiotensin converting enzyme (ACE) secreted by lung, and is leaved by the ACE to Angiotensin 2
197
What does angiotensin 2 do?
Act on hypothalamus to release thirst signal
Act on blood vessels and cause vasoconstriction
Act on adrenal cortext and stimulate aldosterone secretion, which retain salt and water
All these result in increase in blood pressure
198
What is natriuretic peptides?
A family of tiny peptide molecules, acting as a hormone, stimulate water release
199
Where is natriuretic peptides excreted from
From secondary endocrine glands
200
Where is ANP released from
Atrial natriuretic peptide, is released from atrial myocardial cells (in heart atrium) and neurons
201
What is the effect of ANP
Increase K+ reabsorption, decrease Na+ and H2O reabsorption
Suppresses renin, aldosterone, vasopressin
202
What is the stimulus of ANP release
When a big stretch is sensed in heart, this indicates the blood pressure is too high, too much water
203
What does ANP do
Dilates blood vessels, decrease blood volume, increase renal fluid excretion
204
What does ANP do to hypothalamus
Decrease the release of vasipressin
205
What does ANP do to the GFR?
It increase the glomerular filtration rate, so more filtrate flows in nephron, and more H2Om excretion
206
Where is the adrenal gland?
Sits on top of kidney
207
What is adrenal gland make up of?
Adrenal medulla on the inside, surround by adrenal cortex on the outside
They are different tissues with very different function
208
What hormone is released from adrenal medulla
Catecholamine--> epinephrine
209
How is the release of catecholamine from adrenal medulla regulated?
Preganglionic sympathetic neuron, which extends from spinal cord to adrenal medulla, stimulate the chromaffin cells, and epinephrine is release into blood
210
What is the stimulus for epinephrine release
Activation of the sympathetic nervous system
211
What does epinephrine do to the respiratory system
Bronchodilator, so more O2 can be taken in
212
When is epi pen used?
Used to fight severe allergic reaction- anaphylactic shock
213
How does epi-pen counter the symptoms of anaphylactic shock
Anaphylactic shock cause bronchospasm, which constricts the airways, respiratory failure
Epinerphrine is a bronchodilator, which opens up the airway and allow more air in
Other effects are vasoconstriction and dilation
214
What is released in zona glomerulosa?
Aldosterone
215
What is released in zona fasciculata
Cortisol (glucocorticoids
216
What is released in zona reticularis
sex hormones
217
What is androgens?
Sex steroid
218
Where is androgen made in
Zona reticularis on the adrenal cortex
219
What is the strength of androgens made in adrenal cortex
It is weak, comparing to the one made in reproductive organs
It is less than 20% activity
220
What can increase the release androgen (hint: upstream)
ACTH
221
What is the effect of adrenal cortex androgen in child, adult man, adult woman
Child: male prenatal development, and contribute to andrenarche (pubic hair, acne, etc) at onset of puberty for both male and female
Adult man: no role
Adult woman: maintain pubic and axillary hair, source of estrogen after menopause (stop of period)
222
What is cortisol?
Main glucocorticoids, made from zona fasciculata of the adrenal cortex
223
What pathway is used to control cortisol release
Hypothalamic-pituitary-adrenal pathway
224
How often is cortisol secretion?
Continuous, as it is essential for life
225
What is the main goal of cortisol
Mediate long term stress
226
What type of metabolic effects does cortisol have primarily
catabolic
227
what does cortisol protect us against?
Hypoglycemia (low glucose in body stream), through permissive effect
228
What are the 4 main metabolic effects of cortisol
1: Promote gluconeogenesis
2: break down of skeletal muscle portein, use as AA source
3: Lipolysis, breakdown fat
4: supress immune system
229
What is a clinical use of analog of cortisol
Use to suppress immune system, inhibiting inflammatory responses
230
What is the consequence of long term cortisol drug usuage
Inhibition of ACTH secretion due to excess -ve feedback upstream regulation
Atrophy of cortisol secreting cells (decrease cell size)
231
What is addison's disease
Chronic disease, aka adrenal insufficiency
Hypoexcretion of adrenal steroid hormone
232
What is the cause of Addison's disease
Destruction of adrenal cortex by autoimmunity, or infections
233
What are the symptoms of Addison's disease
Hypotension: low blood pressure, due to water loss, due to insufficient aldosterone
Hypoglycemia, due to low glucose level, due to insufficient cortisol
234
Is Addison's disease always chronic
No
It can be acute sometimes, which is very dangerous and fatal
235
What is cushing's syndrome?
Adrenal hormone disorder, excess of cortisol
236
What is the cause of cushing's syndrome
Tumour: secretes excess cortisol
Cortisol therapy: intake excess cortisol
237
What some symptoms of Cushing's syndrome
Hyperglycemia
Muscle protein breakdown
Lipolysis, but build up fat on trunk and face (cushing)
Increased appetite
Mood elevation, depression
Difficulty with learning/ memory
