Exam 1 Flashcards
1
Q
The number of cells in the human body?
A
35 trillion
25 trillion are red blood cells
2
Q
Define homeostasis?
A
The healthy balance constantly maintained by the body’s cellular processes.
All the body systems work together to maintain homestasis
“what goes in must go out”
3
Q
What are the components of energy?
A
Work, heat, and potential energy
4
Q
How does anesthesia impair homestasis?
A
Anesthetics impairs almost all control sensors - so the body will no longer maintain it’s own homeostasis (that is now our job).
5
Q
Describe how peripheral circulatory beds maintain homeostasis?
A
Increased cellular metabolism causes a nutrient deficency, blood flow increases to supply more nutrients (breakdown of ATP and release of adenosine). The increased inflow of nutrients also causes an increased outflow of blood and waste products.
DELIVER ONLY ENOUGH TO MEET TISSUE NEEDS
“what goes in must go out”
6
Q
Describe how the GI system can maintain homeostasis?
A
Returns depleted nutrients to the bloodstream
7
Q
Describe how the kidneys can maintain homeostasis?
A
The kidneys buffer the pH when out of range and assist in blood pressure control.
8
Q
Describe how the liver can maintain homeostasis?
A
By riding toxins from the blood stream, esp. ethanol.
Liver contains many peroxisomes.
9
Q
What is the major feedback system in the body and describe how it functions?
A
The negative feedback system. The body has sensors that detect a change, the controller is alerted of this change and initiates a negative/opposing change to counteract the effects and maintain homeostasis. Once returned to normal, the contoller stops.
Think of an air conditioning thermostat (turns on when temperature is out of normal, tells the AC/heater to turn on to return the temperature to normal range.)
10
Q
Describe 4 ways the body can regulate a decrease in MAP?
A
- Increase sympathetic outflow (norepinephrine).
- Decrease parasympathetic outflow.
- Increase AVP/ADH (vasopressin)
- Decrease ANP (vasodilatory hormone).
These can all be working simultaneously to maintain homeostasis.
11
Q
Define postive feedback?
A
The stimulus produces a change and the body responds by amplifying this change.
12
Q
What are the 2 types of postitive feedback?
A
Physiologic and pathologic
13
Q
Why would a physiologic postive feedback be less likely to enter a vicious cycle?
A
Physiologic feedback contains checkpoints/safty valves to control respones.
14
Q
Describe how birth is an example of good positive physiologic feedback?
A
Oxytocin is released which causes uterine contractions, the baby is pushed onto the cervix and causes it to stretch, and the cervical stretch causes more oxytocin release.
Birth is the checkpoint that ends the positive feedback loop.
15
Q
Describe how the clotting cascade can be a good positve physiologic feedback?
A
Endothelial injury begins the clotting cascade and the platelet plug is formed, TXA 2 helps vasospasm. Clotting speeds up as time goes on and the feedback stops when bleeding is controlled.
16
Q
How would not having a checkpoint in positive feedback effect the outcome?
A
Without a checkpoint the response will continue and eventually cause deaths or other bad effects (ex: cornary artery blockages and massive blood loss).
17
Q
Describe positive feedback in sepsis/necrosis?
A
Cells begin dying faster than the body can replicate them/get rid of them. The toxic byproducts of cell death leak into the environment and other cells begin to die.
18
Q
Describe positive feedback in severe acidosis?
A
The CNS is affected and can no longer compensate with hyperventilation, the reduced respiratory drive worsens the acidosis, and continues to worsen the CNS.
19
Q
Describe positive feedback in diabetic renal inflammation/hyperfiltration?
A
Nephrons begin to die and they don’t regenerate, putting more strain on the remaining nephrons. With the increased work and with age, these nephrons also die.
20
Q
Describe positive feedback in severe hemorrhage?
A
Blood loss leads to decreased MAP which causes reduced coronary blood flow. The low coronary blood flow causes decreased cardiac output which further reduces the MAP.
With less severe hemmohage, negative feeback will compensate. After more than 20% blood loss, negative feedback can’t keep up and positive feedback will lead to death.
21
Q
Describe the relationship between physiologic systems and and anesthetics?
A
Alterations in physiologic systems (someone who is not healthy) changes how they responed to anesthetics.
Administiring anestheics alters a systems physiology (“takes control systems offline”).
22
Q
Describe the function of a lysosome?
A
Reside within the cell and destroy things when no longer needed with acidity.
The byproducts of breakdown can be recycled.
23
Q
Describe the function of a peroxisome?
A
They neutralize toxins by oxidation reactions.
Primary toxin being ethanol. Many peroxisomes are in the liver.
Think rust leading to malfunction.
24
Q
Describe the structure of the cell membrane?
A
It is made up of a phospholipid bilayer. The heads are polar and hydrophilic, the tails are nonpolar and hydrophobic (made of lipids).
25
The intracellular fluid is primarily what?
70-85% water
## Footnote
Except fat cells
26
The nuclear envelope (or membrane) protects the nucleus how?
It is comprised of a double phospholipid bilayer with small pores that are highly selective.
27
Why is the nucleus highly protected?
Because it contains DNA. It is protecting it from virus and bacteria.
28
What class of drug can enter the nucleus?
Steroids
29
Where is the endoplasmic reticulum located?
It is an extension of the nucleus.
30
What is the purposes of the endoplasmic reticulum?
Used for storage (calcium), and producing protiens and lipids.
31
Describe how a protien is created in the cell?
DNA contains the protein code sequence. DNA is transcribed to RNA. RNA transports the code out of the nucleus to the ribosome. The ribosome takes these instructions and forms an amino acid chain and forms the protien. Proteins that will leave the cell go to the Golgi apparatus for final modifications and packaging.
32
What occurs in the granular/rough endoplasmic reticulum?
Protein production by ribosomes.
| These protiens are not ready after this stage.
33
What occurs in the smooth endoplasmic reticulum?
Fat production
34
What occurs in the golgi apparatus?
The proteins that arrive from the rough ER are modified to their final state and then packaged to leave the cell.
35
How are protiens transported to the golgi apparatus and out of the cell?
By transport vesicles and secretory vesicles, respectively.
36
What is the purpose of proteins on the cell wall?
They help water soluble or polar compounds cross the cell membrane.
| Each protien has specific task
## Footnote
These molecules need help because without it they cannot cross the hydrophobic center of the cell membrane.
37
What is the purpose of sugars in the cell?
On the cell wall they are attached to proteins and:
1. They help identify other cells.
2. They are "sticky" and help the cell attach to other cells around it.
3. They typically have (-) charge and will repel protiens (-).
Intracellularly:
They are a source of energy via glycolysis.
38
Are all protiens produced in ribosomes within the rough ER?
About 95% are, the other 5% are made in ribosomes within the cytosol that do not require packaging or modification.
39
What is an enzyme and what is its purpose?
Typically a protien, ending in "-ase" that catalyze chemical reactions.
40
What is the purpose of filaments and proteins in the cell wall?
They are structural components that help the cell maintain it's shape.
41
What are organelles?
Distinct structures that perform specific tasks within the cell.
42
Can all cells replicate themselves?
No, RBC contain no nucleus and therefore cannot replicate themselves.
## Footnote
Cells that cannot regenerate have nearby progenerator tissues that aid in replication.
43
What are some cells that do not replicate or do not replicate very fast?
RBC, neurons, cardiac cells, and nephrons.
## Footnote
RBC need progenitor cell to replicate.
44
After this age, nephrons begin die off more rapidly?
40-45 years old.
45
How many nephrons are there per kidney?
~1 million
46
What are some motility mechanisms for a cell?
Flagella help move the cell. Cilia are structures on the outside of the cell that move the environment around the cell.
| Cilia - mucous in the airway.
47
Where is genetic material located within the cell?
In the nucleus as DNA, RNA, and as mitochondrial DNA.
48
Mitochondrial DNA comes from?
Inherited maternally.
49
What are some compounds that are typically insoluble in water?
Cholesterol, steroid hormones, lipids, nitrous gas
50
What are some water soluble substances?
Ions, proteins (some), carbohydrates (sugar), gases like CO2, buffers, some drugs
50
How much water is in a healthy adult?
60% of their body weight.
51
Where is most of the body's water located?
The intracellular fluid (ICF).
52
How much of the body's water is in the ICF?
2/3 of the water is in the ICF
53
How much of the body's water is in the ECF?
1/3 of the total body water is in the ECF
54
How much of the ECF is the plasma volume?
1/4-1/5 of the ECF volume
55
What are the components of the ECF?
Plasma and interstitial fluid.
56
What is plasma?
The fluid in the vasculare system not including blood cells.
57
How much of the ECF is the interstitial fluid?
3/4-4/5 of the ECF is interstital fluid.
58
What seperates the intracellular fluid from the interstitial fluid?
Cell membrane
59
What seperates the interstital fluid from the plasma?
Capillary membrane
60
What is the difference in permeability between the capillary and cell membrane?
The cell membrane is much more selective, needs pumps or controllers for polar molecules to cross. The capillary membrane allows small molecules like ions to cross but does not allow larger molecules like proteins to cross- they stay in the plasma.
## Footnote
Water can cross both easily in order to maintain osmolarity.
61
What is the difference between steady state and equilibrium?
Steady state describes the regulated differences and equilibrium means the same inside as outside.
62
What is the normal plasma sodium level?
140 or 142
63
What is the relationship between plasma and intracellular concentrations of sodium?
There is 10 times more sodium in the plasma than the ICF.
| 10:1
64
How can you quickly estimate serum osmolarity?
Multiple the plasma sodium concentration by 2.
65
What is the relationship between plasma and intracellular potassium?
There is 30 times more potassium intracellularly.
## Footnote
30:1
66
What is the normal potassium level in the plasma?
4.0
67
What is the relationship between ECF and ICF concentrations of calcium?
There is almost no calcium in the ICF. The ratio is 1:10,000
68
What is the relationship of magnesium present in the ECF and ICF?
There is much more magnesium in the ICF
69
Why is the ICF so low in calcium and what is calciums function?
It is so that the cell has a low threshold for activation by extracellular calcium for things like muscle movement. Calcium turns cell functions on.
70
What is the function of magnesium in the ICF?
It is a cofactor for many reactions intracellularly.
71
What is chloride's role in the chemistry of ECF?
Chloride is the primary anion in the ECF.
72
In what cellular space is chloride most present?
The ECF
## Footnote
Think NaCl -salt, both in the ECF
73
In what space is HCO3- more present?
In the ECF
74
HPO4 is found in higher concentrations in what cellular space?
The ICF.
## Footnote
Think ATP… lots of ATP in the cell which means lots of phosphate groups!
74
What is HCO3- role in the body's water chemistry?
It is the primary buffer of the ECF.
75
What are the 3 functions of phospate in the role of water chemistry?
1. The primary buffer in the ICF
2. Phosphorylate: attaches and detaches from proteins to turn them on and off
3. Used for energy storage in the from of ATP
## Footnote
Remeber: ATP is only found in the ICF, and contains lots of phospate. Therefore, lots of phospate in the ICF.
76
Where are amino acids found primarily?
In the ICF.
## Footnote
Remember: Amino acids build proteins and proteins are made intracellularly...so lots of amino acids in the ICF
77
Where can you find the higher concentration of creatine and why?
In the ICF because ceratine is stored in skeletal muscles for a short-term energy source from phosphocreatine.
## Footnote
The dephosphorylation of phosphocreatine releases energy.
78
Where is the higher concentration of lactate found and why?
In the ICF, it is a byproduct of intracellular metabolism.
79
In what fluid space will you find ATP and why?
Only in the ICF, it is too valuable to the cell.
80
What is adenosine useful for in the body?
Adenosine can cross the cell membrane and can cause an increase in blood flow to an area to meet increased cellular metabolic needs.
| Adenosine is a vasodilator
## Footnote
ATP can be dephosphorylized all the way to adenosine when the cell is in high metabolic demand.
81
Where is glucose found in higher concentrations and why?
Glucose is higher in the ECF. Cells dont make glucose, they rely on glucose delivery from outside the cell and use it readily for energy or it is stored away.
82
In what fluid compartment is protein more readily found and why?
The ICF , proteins are made intracellularly and are abundant in the cell and cell membrane.
83
What is the relationship between protein concentrations in the plasma and interstitial fluid?
It is 5 times higer in the plasma
## Footnote
Remember: Proteins have a hard time crossing the capillary membrane and usually stay in the plasma (think albumin)
84
What does total osmolarity relate to?
The total number of dissolved compounds in a fluid sample.
85
Why is the corrected osmolarity lower than the total osmolarity.
All the ions do not readily dissociate from each other due to differneces in charge.
| i.e not all the independent compounds are accounted for
## Footnote
Na+ and Cl- may be very close together and appear like one compound instead of two different.
86
What is the corrected osmolarity of the ECF and ICF?
280-283
87
What is the relationship of the osmolarity of the ICF, plasma, and interstitial fluid? Why?
The osmolarity is the same because water can move freely across both the capillary and cell membranes and correct for any solute imbalances.
## Footnote
Water will follow the higher concentration of sodium and balance the solution
88
What are glycolipids?
Sugars attached to lipids inside the cell membrane.
89
Why can cholesterol be found in the cell membrane?
Cholesterol is hydrophobic, lipid soluble (composed of mainly C and H)
| The inner cell membrane is composed of fatty acids that are hydrophobic
90
What is a glycoprotein?
A protein with a sugar attached, in the cell membrane
91
What does the term glycocalyx refer to?
The sum of the external sugar structures on the cell wall
## Footnote
Used a lot for immune system functions (identification of other cells)
92
Describe the structure of cholesterol as well as its location on the cell wall?
Cholesterol mostly resides inside the cell membrane with only the OH group facing inwards/outwards of the membrane. It is planar and rigid at normal body temperatures.
93
What effect does cholesterol have on membrane fluidity?
It decreases membrane fluidity (more rigid)
## Footnote
Rememeber: Increased cholesterol level make blood vessels "stiff"
94
How many sets of mitochondrial DNA are there?
12-20
95
What is glycolysis?
The consumption of intracellular sugars to make ATP.
96
What charge do external sugars typically carry?
Negative charge
97
What is normal total osmolarity?
~300 mOsm/L
98
What is the total osmotic pressure within all compartments?
~5400 mmHg, all of the dissolved solutes exert lots of pressure in the ECF and ICF.
## Footnote
Remeber: Normal BP ~120 mmHg
99
What can Acetyl-CoA be used for?
Can be used to make cholesterol and ATP by glycolysis and oxidation reactions.
100
Where does our body get cholesterol?
20% is exogenous and 80% is endogenous
101
What 6 molecules are metabolites of cholesterol?
Progesterone, aldosterone, cortisol, androstenedione, estradiol (E2), and testosterone (T).
102
What effect does the structure of cholestrol derivatives have on receptors?
Many of the derivatives are very similar in structure, expecpt for minor changes. Thus, some metabolites can bind to each others receptor sites. The body has mechanisms to combat this.
| Aldosterone and cortisol
103
What are the precurors that are attached to the cell membrane?
1. Arachidonic Acid
2. Phosphatidylinositol (PI)
3. Phosphatidylserine (cytosolic)
4. Phosphatidylethanolamine
5. Phosphatidylcholine (PCh)
6. Cholesterol
7. Sphingomyelin
104
What is Phosphatidylinositol (PI) a precursor for?
Smooth muscle contraction, phosphorylates to IP3 (inositol triphosphate).
105
Describe the function of Phosphatidylserine (cytosolic)?
It acts as an immune marker, it is facing inwards in healthy functioning cells. When facing the outside of the cell, the immune system detects it and destroys what it is attached to.
106
Describe the importance and role of flipase?
Flipase keeps it facing inwards towards the cell, when it jumps to the ECF membrane, flipase "flips" it back by using ATP. When ATP is deficent (ischemia), flipase can't flip it and phosphatidylserine remains on the ECF membrane, causing the immune system to target and kill that cell.
## Footnote
Can be bad when large tissues are affected, like MI or stroke. Good for infected cells.
107
What is the role of phosphatidylcholine?
Storage of choline that is used to assemble acetylcholine.
108
What does sphingomyelin do?
Helps make myelin
109
What are 3 arachidonic acid metabolism pathways?
1. Prostaglandin and TXA2 formation via COX 1 and COX 2
2. Leukotryine formation by lipoxygenase (LO).
3. HETE/EET formation.
110
Describe the prostaglandin formation pathway?
1.Arachidonic Acid becomes PGG2 and then PGH2 in sequential reactions by COX 1/COX 2.
2.PGH2 becomes a number of prostaglandins and TXA2 by prostaglandin synthases.
111
What role do prostaglandins play?
They increase the sensitivity to pain.
112
What is TXA 2 (thromboxane A2) function?
Causes vasospasm (squeezing) when blood vessels are injuried to reduce bleeding.
113
Where is COX 1 and COX2 found?
COX 1 is widespread in the body. COX 2 is turned on in response to pain and is also found in the kidneys and heart.
114
What is a good COX 1 inhibitor drug?
Aspirin
115
Why would aspirin have a risk of increased bleeding?
Because it irreversibly binds to COX1 inhibiting it. Which will prevent the formation of TXA2 - which aids in control of bleeding.
116
What is a good COX 2 drug?
Naproxen
117
How are leukotrines formed? what are their function?
Arachidonic acid becomes leukotrines by the enzyme lipoxygenase (LO). Leukotrines are responsible for immune mediated inflammation.
## Footnote
Singulair inhibits leukotrines.
118
What is HETE/EET?
They are derived from arachidonic acid and are mediators in acute renal failure.
##Footnote
Very big, stay on cell wall
119
What is simple diffusion and what are some examples?
Where molecules move across the membrane without the use of energy or binding.
Examples: gases move independently across the cell, Na+, Cl-, and H2O move across via channel protiens.
120
What is the channel protein the allows water across the cell?
Aquaporin channel protien, water can also go through other ion channels
121
What governs the diffusion of molecules across the cell wall?
1. Chemical gradient: high to low solute concentration.
2. Electrical gradient: postively charged area to negatively charged area.
122
Describe facilitated diffusion?
Molecules bind to a membrane protein, cause a conformation change, and moves from one side to the other. This does not require energy; molecules are still moving with the chemical/electrical gradient.
123
What is an example of facilitated diffusion?
GLUT transporters.
124
Where are GLUT-1 transporters found?
In RBC
125
How do GLUT-4 transporters work? Where are they found?
They respond to insulin by adding more GLUT transporters on the cell membrane to increase the speed of glucose transportation into the cell to decrease serum glucose levels. Found in muscle and fat.
| Facilitated Diffusion
126
Describe active transport and it's necessity?
The transportation of molecules across the cell wall against their gradient. Because they are moving molecules where they wouldn't normally travel by themselves, this transportation requires the use of energy. Active tranporters also speed the rate of transportation of ions.
127
Describe the 2 types of active transport covered in class? What are some examples?
1. Primary: The pump directly uses ATP to perform it's function. Sets up concentration gradients.
-Na+/K+/ATPase pump, Proton pump, Calcium ATPase pump.
2. Secondary: Does not directly use ATP. Uses the elctrochemical gradient (stored energy) set up by primary transporters to "pull" or "co-transport" molecules in/out.
-NCX, SGLT
128
Explain how the NCX (Na Ca Exhanger) functions?
The membrane protein pulls 3 Na+ into the cell while simultaneously pushing 1 Ca 2+ out of the cell. Becuase Na+ *wants* to go into the cell, it uses sodium's elctrochemical gradient (stored energy) to push calcium out - against it's gradient.
129
How does the SGLT funtion? Where is it important?
The membrane protein binds to Na+ in the ECF (that already wants to come into the cell), and attaches a glucose at the same time and pulls both Na+ and glucose intracellularly. It uses sodium's electrochemical gradient (stored energy) to co-transport gluocse along with it.
Important in kidneys.
130
How does the Na+/K+/ATPase pump function? Why is this pump important?
1.The pump attaches 3 Na+ intracellularly and 2 K+ extracellularly - then uses the dephosphorylation of ATP to transport the ions against their concentration gradients.
2. It is important in setting up action potentials. Also sets up the gradient (stored energy) that secondary active transporters utilize to perform their function.
131
Where may you not find Na+/K+/ATPases and why?
Neurons, because these pumps use a lot of ATP that some cells like neurons do not have enough of to operate this pump.
132
What is cholesterol used for in foods?
To make substances creamier, like ice cream.
## Footnote
Membrane fluidity increases at lower temperatures.
133
What compounds are important in surfactant production?
Phosphatidyl's
134
Where can you find leukotryines and prostaglandins after they are produced? Why?
The move off of the cell wall into the cellular fluid because they are much smaller than arachidonic acid.
135
Where do statins work to inhibit cholesterol?
HMG-CoA reductase
136
How much pressure does 1 mOsm of a solution exert?
19.3 mmHg per mOsm of solution.
137
How can you calculate osmotic pressure?
Multiply the osmolarity (in mOsm) by 19.3 mmHg.
138
Describe the difference between osmolarity and osmolality? Why do we use osmolarity?
Osmolality is the quantity of dissolved solutes in 1 Kg (1L) of water. Osmolarity is the quantity of dissolved solutes per 1 L of solution. We osmolarity because we don't draw only blood from patients, it is a solution with many other molecules.
| Osmolality is technically more accurate but impratical
139
What do mEq and mOsm represent?
A *quantity* of something
140
This function uses 60-70% of a cell's energy use?
The Na+/K+/ATPase pump.
141
At rest, what is the charge inside the cell? Why?
It is electronegative. Because the Na+/K+/ATPase pump causes a net removal of 1+ charge per cycle (Na+). Cytosolic membrane proteins also have a net negative charge.
142
What cellular function is the primary source of intracellular Na+?
The NCX pump. 3 Na+ are moved inside the cell per pump and 1 Ca 2+ is moved out.
143
Describe why breakdown of the Na+/K+/ATPase pump would cause cellular edema?
Breakdown of the pump can occur due to lack of ATP. The pump breaking down causes an increase in intracellular osmolarity (more Na+ is building up inside the cell). This causes more water to stay within the cell, leading to cellular edema.
144
Describe the difference in rate of diffusion between simple and facilitated diffusion as concentration increases?
Facilitated Diffusion: as concentration of a substance increases the rate of diffusion increases with it initially until the proteins reach Vmax. At that point diffusion plateaus because they are maximum speed.
Simple Diffusion: as concentration increases, rate of diffusion increases linerally. There is no Vmax, becuase the electrochemical gradient is driving diffusion, not the activity of a pump. (the greater the difference in concentration, the faster the movement).
145
How does membrane lipid solubility effect net diffusion rate of a substance?
The more lipid soluble, the faster the movement across the membrane.
146
How does the size of a particle effect net diffusion rate of a substance?
The smaller the particle, the faster it moves across the membrane.
147
How does the number of pores effect net diffusion rate of a substance?
The less pores for travel, the slower the movement across the membrane.
148
How does kinetic movement effect net diffusion rate of a substance?
The higher the temperature, the faster substances will travel across the membrane.
149
How can physical pressure effect net diffusion rate of a substance?
The more pressure the faster the rate of movement.
## Footnote
Higher or lower blood pressure
150
How can electrical charge effect net diffusion rate of a substance?
The greater the difference in electronegativity, the faster the rate of diffusion. (Positive to negative).
151
During osmosis in a controlled setting, why doesn't all the water displace to the area of increased osmolarity?
Because gravity prevents some of the water from moving all the way across.
152
What membrane structures contribute to intraellular electronegativity?
The membrane proteins often have internal subunits (GPCR) and those carry a net negative charge and they are arranged to face the cytosolic side of the membrane.
153
What is the Nernst potential (equilibrium potential)?
This equation shows what a concentration of 1 ion will change in the intracellular membrane potential. Prevents ion from moving across.
EMF (mV) = +/- 61 x log(concentration inside/concentration outside)
154
How do you know when to use a + or - in the nernst equation?
Cations will use - and anions will use +
155
What is the difference in permeability between Na+ and K+?
They are both permeable to the cell but K+ is 10 times more permeable.
| So K is the primary ion that determines membrane potential.
156
The normal cell's electrical charge is around -80mV. If K+ contributes -91mV and Na+ contributes +61, why is the cell electronegative?
Because K+ is 10x more permable than Na+ and therefore contributes 10x more the cells electronegativity.
| The Goldman Equation
157
What is the Goldman Equation (GHK)?
It states that each ion gradient contributes to the membrane potential only to the extent that the cell is permeable to that ion.
## Footnote
i.e. The more permeable ions contribute more the cell's charge or membrane potential.
158
What is Vrm?
Resting membrane potential
159
Describe "leak channels"?
Leak channels are ion channels that allow the near constant inflow/outflow of ions. Specifially K+ and Na+.
160
How does the cell keep all of the K+ from leaking out of the cell?
It is because of the equilibrium potential of K+ and the resting membrane potential of cell.
Ek = -90mV and Vrm = -80 mV, therefore the positively charged K+ ion is being "pulled" into the cell, despite it wanting to move out based on its electrochemical gradient.
## Footnote
The cell is already almost at Ek, meaning close to being at equilibrium and not wanting to move at all.
161
What is cell polarization?
The difference in charge between the inside and outside of the cell.
## Footnote
Polarized at rest, -mV
162
What is depolarization?
To be come less polar, or more positively charge.
| Usually means stimulated. Means the cell's Vrm has increased.
163
What is hyperpolarization?
To be come more polar, or more negatively charged.
| Usually means inhibited; harder to excite.
164
What is repolarization?
To return to Vrm from a depolarized state.
165
What can cause hyperpolarization during the repolarization phase?
The influx of K+ to repolarize the cell can "overshoot" Vrm and temporarily make the cell hyperpolarized. This occurs because the VG K+ channel is slow to close.
166
Describe the structure of voltage gated Na+ channels?
They are closed at rest and allow the influx of Na+ during depolarization once threshold is met. The protein has an inner gate (H-gate/inactivation gate) and outer gate (M-gate/activation gate). In the middle is a selectivity filter that ensures only Na+ can pass through. The action of opening and closing is very fast.
167
Describe the action of a voltage gated Na+ channel?
At rest, the M-gate is closed and the H-gate is open. Once activated the M-gate opens first (activated), then immediately followed by the H-gate closing (inactivated). The cell then must repolarize to open the H-gate or reset the channel.
168
Describe the structure and function of the voltage gated K+ channel?
It has only and inner gate that is closed at rest. It also has a selectivity filter for the K+ ion. The gate opens to repolarize the cell and is slower (to open and close) than the voltage gated Na+ channel. It closes when Vrm is restored.
169
How does the voltage gated Na+ channel cause depolarization?
Because the positively charged ions flood into the negatively charged cell, temporarily shifting the Vrm to positive.
170
How does the voltage gated potassium channel aid in repolarization?
Because the cell has become postive due to depolarization by Na+ influx, by releasing intracellular postively charged K+, the cell can restore it's Vrm, and bring it back to negative. This speeds the cells return to Vrm and the resetting of V-G Na+ channels.
171
What is meant by the term "driving force"? What contributes to it?
What causes an ion to want to move into or out of the cell. Determined by: concentration gradient, ionic charge, and intracellular charge.
172
What would the membrane potential (Vrm) have to be to keep a ion from moving down it's concentration gradient?
It would have to be equal to the nernst potential for that ion.
173
Why doesn't Na+ flood into the cell all the time through it's leak channels?
Because there are not that many Na+ leak channels as compared to potassium, so entry is limited.
174
Do you have to have current running across the membrane to maintain its mV?
No, there just needs to be a *potential* for current. But most of the time this is being controlled by ions moving back and forth.
175
What drug class inhibits V-G Na+ channels? Where does it inhibit?
-*caine* derivatives, at the ECF side of he pump.
| Ex: Lidocaine and Bupivicaine
176
What position's are the M-gate and H-gate in at rest in a VG Na+ channel?
The M-gate is closed and the H-gate is open.
177
What position's are the M-gate and H-gate during inactivation in a VG Na+ channel?
M-gate open and H-gate closed.
178
How does the VG Na+ channel reset itself or prepare for another action potential?
The M-gate has to close first and then H-gate can reopen, which brings the channel back to resting posititon.
179
What does hematocrit represent?
The percentage of the vasculature volume that is blood cells.
180
What is the plasma equation when given HCT?
Plasma = BV (1-HCT)
