1
Q
Describe ECF
A
where cells reside, take up O2 and nutrients, discharge waste. divided into interstitial fluid, blood plasma and lymph fluid. 20% body weight. Na+ is most abundant cation.
2
Q
Describe ICF
A
cell membrane barrier. 40% body weight, K+ most abundant
3
Q
Fluid compartment percentages for:
- total body weight
- ICF
- ECF
- Interstitial fluid
- PV
A
- total body weight = 60%
- ICF = 40%
- ECF = 20%
- Interstitial fluid = 15%
- PV = 5%
4
Q
Improper compartmentalization of fluids
A
Edema
5
Q
Homeostasis
A
balanced internal condition of cells
- maintained = physiology
- not maintained = pathophysiology
ex. maintenance of blood glucose and body temp
6
Q
Dynamic constancy
A
always changing but helps maintain constant of our body (equilibrium)
7
Q
Equilibrium
A
process of homeostasis; condition where variable is constant but no amount of energy input is required to maintain constancy (no net change)
8
Q
Components of homeostatic system
A
- stressor = triggers mechanism
- sensor = detects stress
- control center = signals traveling from controlling gland to take action upon the stressor
- effector = takes action
- effect = result from effectors
9
Q
Hyperthermia: Negative Feedback Loop
A
- stressor = hyperthermia / high body temp
- sensor = heat receptors in the skin
- control center = hypothalamus
- effector = increased activity of sweat glands
- effector = increased blood flow to the skin
- effect = perspiration evaporates thus colling the skin
10
Q
Hyperglycemia : Negative Feedback Loop
A
- stressor = hyperglycemia/ high blood glucose
- sensor = pancreas beta cells
- control center = pancreas
- effector = insulin released in blood
- effector = liver and muscle cells uptake glucose from blood
- effect = decreased blood glucose
11
Q
Afferent path
A
PNS to CNS
12
Q
Efferent Pathway
A
CNS to PNS
13
Q
Example of a Positive Feedback Loop within a Negative System
A
Coagulation - accelerating of clotting
14
Q
Childbirth : Positive Feedback Loop
A
- stressor = pressure of fetus on uterine wall
- sensor = afferent nerve endings within the uterine wall
- control center = hypothalamus
- effector = production and release of oxytocin in the blood
- effector = increase in uterine contractions
- effect = intensification of contractions
15
Q
Harmful effects of positive feedback system
A
-fever: continues to rise unless fever reducing medication is given
- chronic HTN: BV narrow causing increased pressure, further damaging BV
- decreased blood flow to brain: decrease in sympathetic nerve activity = decrease in BP = decreased blood flow
- anaphalaxis: overproduction of histamines
16
Q
Most abundant cation in ICF
A
K+
17
Q
Most abundant cation ECF
A
Na+
18
Q
Plasma Membrane Functions
A
acts as “gatekeeper”
-binding sites for enzymes
19
Q
Plasma Membrane
A
selective barrier to passage of molecules; impermeable to Na+
-phospholipid bilayer with hydrophilic heads (polar/outside) and hydrophobic tails (nonpolar/inside)
20
Q
Phospholipid Bilayer
A
amphipathic:
hydrophilic heads - polar regions (outside)
hydrophobic tails - nonpolar regions (inside)
21
Q
Hydrophobic molecules
A
pass easily through the membrane (attracted to middle of bilayer lacking H2O
ex. O2, CO2, H2O
22
Q
Hydrophilic Molecules
A
do not pass easily through the membrane since they are attracted to the polar water molecules in the ECF and cytosol
ex. proteins
23
Q
integral membrane proteins
A
cannot be extracted without disrupting the bilayer.
- amphipathic
- transmembrane
- loop through the membrane
- form channels to help with transmission of chemical signals
24
Q
peripheral membrane proteins
A
bound to polar region of the integral proteins and on the cytosol surface
25
Membrane components
- rich in unsaturated fatty acids
- **steroid cholesterol**: temperature buffer in PM wedged between phospholipid molecules
- **carbohydrates**: facilitate cell to cell recognition by interacting with other surface molecules
26
Role of Steroid Cholesterol in Plasma Membrane
**temperature buffer** between phospholipid molecules
- **cool temp** = maintains fluidity by preventing tight packing
- **high temp** = restrains movement of phospholipids to reduce fluidity
27
Functions of membrane proteins
**-transport:** channels hydrolyzing ATP to pump substances across; can be selective
**-enzymatic activity:** uses enzyme to facilitate transport
**-signal transduction:** specific shape for signal to send message (ex. hormone)
**-cell to cell recognition:** identification tags for specific recognition (glycoproteins and glycolipids)
**-intracellular joining:** shapes fit and connect (gap junctions)
**-attachment of ECF and cytosol:** stabilizes location of membrane proteins
28
Membrane fluidity is influenced by:
temperature & components
29
Molecules that cannot pass through the membrane easily:
- **large polar molecules** (glucose)
- **charged molecules** (H+, Na+, Cl-, Ca2+)
30
Molecules that can easily pass through the membrane:
- **gases** (O2 & CO2)
- **hydrophobic molecules** (benzene)
- **small polar molecules** (H2O & ethanol)
31
Carbohydrates and lipids combine to form:
Glycolipids (cell identity markers)
32
carbohydrates and proteins combine to form:
glycoproteins (cell identity markers)
33
Diffusion of substance across membrane with no energy investment
Passive Transport
34
Simple Diffusion
-Passive Transport
**-no energy required / down concentration gradient from high conc. to low conc.**
- lipid soluble molecules (O2, CO2, H2O)
- ex. sugar dissolving in water
35
Facilitated Diffusion
-Passive Transport
**-uses transport proteins to move hydrophilic molecules down the concentration gradient (high to low)**
**-channel proteins**: formation of channel to move substance across membrane (sometimes specific)
**-carrier proteins**: specific size or shape that a molecule must fit in order for carrier protein to bind & bring it to the other side of the membrane
36
Factors affecting permeability of membrane
**-lipid solubility**
-**size** (small is easier to pass than large)
**-ion charge**: _hydrophilic_ (polar - cannot pass easily) + _hydrophobic_ (nonpolar - can pass easily)
**-presence of channels and transporters**: allows passage of hydrophilic substances
37
Osmosis
-Passive Transport: down conc. gradient from high to low
**-diffusion of water (solution) across semipermeable membrane from hypotonic to hypertonic solution**
**-solvent diffuses until equal concentration of water inside and outside of the cell**
-**aquaporins**: water channels / protein pores (always open)
38
Solution
**homogeneous mixture of 2 or more components**
-contains solvent & solute
39
Solute
components in smaller quantities within a solution
40
Solvent
dissolving medium (water)
41
Osmotic pressure
needed to keep the cell in equilibrium with H2O
**-increase concentration of solutes = increase in osmotic pressure**
42
Tonicity
ability of solution to cause a cell to lose or gain water based on the concentration of solutes
43
Cytolysis
cells swell and burst
44
Plasmolysis
cells shrink / shrivel
45
Equal concentration of water inside and outside of the cell
**isotonic solution**
-no net movement of water
46
More H2O outside of the cell than inside of the cell
**hypertonic solution** (shriveled - plasmolysis)
-movement of water outside of the cell (towards Na+)
47
More H2O inside of the cell than outside of the cell
**hypotonic solution** (swollen; may burst - cytolysis)
-movement of water into the cell (towards Na+)
48
Using energy from ATP & membrane pumps to move substances up concentration gradient (from low concentration to high concentration) across the membrane
Active Transport
49
Sodium Potassium Pump (Na+/K+ pump)
-inside the cell has high K+, low Na+
**-moves 3 Na+ out of the cell, 2 K+ into the cell while hydrolyzing ATP**
-uses 30% of cell's energy
\*normally sodium would flow into the cell (since it's the most abundant ECF cation) but the pump forces the opposite
50
Steps of Na+/K+ Pump Mechanism
1. 3 Na+ bind to cytoplasmic side of the protein
2. Phosphate is transferred from ATP to protein
3. Phosphorylation changes the shape of the protein, moving 3 Na+ out and across the membrane
4. K+ binds to the protein, causing phosphate release
5. Release of the phosphate changes the shape of the protein, moving 2 K+ across the membrane and into the cytoplasm of the cell
51
Bulk Transport
allows small particles or groups of molecules to enter or leave the cell without actually passing through the membrane
- exocytosis
- endocytosis
52
Exocytosis
bulk tranport
**-vesicles fuse with plasma membrane and release large groups/particles to ECF**
-how hormones are secreted
53
Endocytosis
bulk transport
**-plasma membrane develops small particles of fluid that seal onto itself to create a vesicle and then enters the cell**
-phagocytosis + pinocytosis
54
type of Endocytosis
cell engulfs particle by creating a vacuole (specific particle)
Phagocytosis
55
Intracellular Communication
**between 2 cells; critical for survival and functionality of the cell**
- nervous system and endocrine system
- nervous tissue and skeletal muscle tissue
56
A cell is a battery with opposite charges
**positive** charge is **OUTSIDE**
**negative** charge is **INSIDE**
57
Polarization
any state where the membrane potential is other than 0 mV
58
Depolarization
the membrane becomes less polarized than the resting potential
**-influx Na+ (exceeds threshold)**
-open by positive feedback → transmit signals to the brain
\*voltage gated Na+ channels
59
Repolarization
the membrane returns to the resting potential after having been polarized
-inactivate Na+ channels, activate K+ channels
\*voltage gated K+ channels
60
Hyperpolarization
the membrane becomes more polarized + positive than the resting potential (overshoot)
(K+ channels are slow to close → hyperpolarization)
61
Resting Membrane Potential (RMP)
the voltage (charge) difference across the cell membrane when the cell is at rest- often negative voltage
-maintained by Na+/K+ pump
62
Leakage Channels
constantly open + allow K+ ions to flow freely across the plasma membrane
-without these, there would be an equilibrium that would never change (same charge inside and outside of the cell)
63
Peak of Action Potential
Na+ decreases
64
Rising Phase
Na+ channels open membrane potential and shift towards equilibrium potential for Na+
65
Threshold
membrane potential at which voltage gated channels open
-55mv
66
No voltage = no action potentials →
unable to create movement of skeletal muscle
-charge across the membrane is 0 mV
67
3 Factors producing resting membrane potential (RMP)
1. **presence of fixed non-diffusable anions in the cell** (attract positively charged ions from outside into the cell via leakage channels)
2. **preferential permeability of the plasma membrane**
3. **Na+/K+ pump**
68
Effectors on membrane potential
- fixed ions (negatively charged inside the cell - do not diffuse into the ECF)
- cellular proteins
- phosphate groups
- other organic compounds (attracting positively charged ions from ECF into the cell via leakage channel)
69
Cells are primarily permeable to
**K+**
(K+ leakage channels are in more abundance than Na+ leakage channels)
70
K+ diffuses down conc. gradient out of the cell via leakage channel
**increase in K+ intracellularly, decrease in K+ extracellularly**
-attracted to negative charge within the inner membrane
71
Graded Potential
**-ALL OR NONE; can lead to an action potential or stops**
-small change within the RMP
**-must occur in order to depolarize the neuron to threshold before an action potential can begin**
-stimulus is **NOT** strong enough = **NO ACTION POTENTIAL**
72
Synaptic Potential
type of graded potential that **leads to an action potential**
## Footnote
**-to change the RMP, you must modify the ionic flow in relation to how much Na+ is outside the cell vs. how much K+ inside the cell - accomplished by FACILITATED DIFFUSION**
73
How to change the Resting Membrane Potential (RMP)
**you must modify the ionic flow in relation to how much Na+ is outside the cell vs. how much K+ inside the cell -** accomplished by **FACILITATED DIFFUSION**
74
Ligand Gated Channels
**open via chemical stimulation**
- infusion of Na+ to ICF the cell and K+ to ECF
- cholinergic channels require ACh or neurotransmitter to open → **binding to neurotransmitter causes DEPOLARIZATION of plasma membrane**
- prevalent in dendrites + neuron body
- Na+ going out \> K+ moving in
**-LIGAND CHANNELS stimulate need for positive charge (Na+ influx) to get ACTION POTENTIAL**
75
Increasing Ach at dendrites opens more ligand gated channels, meaning
greater degree of depolarization
76
Greater chemical stimulus = greater \_\_\_\_\_
DEPOLARIZATION
77
in order to reach threshold, you need a ….
strong stimulus that occurs for a long period of time to trigger an action potential
78
Decaying Depolarization
if the stimulus is too small and the distance is too short then it will not reach the length of the axon
## Footnote
**-no action potential produced**
79
Voltage Gated Channels open at what voltage charge?
-55 mV (threshold potential)
80
Once threshold is met, voltage gated channels open:
→ influx of Na+
→ stimulus ends, repolarization occurs (K+ moves into the cell)
→ reaches threshold again (hyperpolarized)
81
Voltage Gated Channels
open once the potential threshold is met (-55 mV)
## Footnote
**-starts action potential process**
82
Na+ Voltage Gated Channels
1st to open - **DEPOLARIZATION**
- creates a positive charge inside the cell
- FAST
83
K+ Voltage Gated Channels
2nd to open - **REPOLARIZATION**
- creates a negative charge once threshold is met
- **SLOW** to open/close → repolarization OVERSHOOTS its normal RMP
84
Na+ channels are **deactivated** → _____ stops
Depolarization stops
-then, K+ channels open and the cell returns to a repolarized state (outside of the cell = positive + / inside of the cell = negative -) → HYPERPOLARIZATION
85
Absolute Refractory Period
cannot generate another action potential
86
Relative Refractory Period
**action potential goes below the RMP (hyperpolarization)**
-can generate an action potential but needs a very strong stimulus
87
Resting Stage of A.P. Generation
**polarized, overall negative charge**
- nerve cell = -90 mV (quick A.P.)
- pacemaker cell = -60 mV (slow A.P.)
- skeletal cell = -83 mV
**\*maintained by Na+/K+ pump**
88
Cell body of a Neuron
**input zone**
houses the nucleus and organelles
89
Dendrites
**input zone**
-projections that increase surface area to receive and send signals towards the nucleus
90
Axon
**conduction zone**
tubular extension conducting A.P. away from the body
91
Axon Terminal
**output zone**
influences other cells by sending signals (hormone or chemical release)
92
Classification of Neurons by **Poles**
→ **unipolar**: one pole (embryonic stage)
→ **bipolar**: 2 poles; axon and dendrites are on opposite ends
→ **multipolar**: nucleus has multiple poles
93
Classification of Neurons by **Function**
→ **motor** = efferent (CNS to PNS); long axon with short dendrites
→ **sensory** = afferent (PNS to CNS); short axon with long dendrites
94
Classification of Neurons by **Length**
→ **golgi type 1**: long axon; body is CNS; axon reaches remote periphery organs
→ **golgi type 2**: short axon; present in spinal cord and cerebral cortex
95
Electrical Synapse
**transmits signals through ions between cells (electrical charge)**
- utilizes gap junctions
- quick and bidirectional
96
Chemical Synapse
**neurotransmitter binds to a receptor at post-synaptic site**
-slow and one directional
97
Steps in Neurotransmission
1. Neurotransmitter molecules are synthesized and packed in vesicles
2. An action potential arrives at the presynaptic terminal
3. Voltage gated Ca2+ channels open and Ca2+ enters the cell
4. An increase in Ca2+ triggers fusion of synaptic vesicles with the presynaptic membrane
5. Transmitter molecules diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic cell
6. Bound receptors activate the postsynaptic cell
7. A neurotransmitter breaks down + is taken up by the presynaptic terminal or other cells, or diffuses away from the synapse
98
Excitatory Post-Synaptic Potential (EPSP)
**influx of Na+ = uptake**
-trying to produce an A.P.
**-quick succession → EPSP wins over IPSP and generates an ACTION POTENTIAL**
**-depolarization** of neurotransmitter
99
Inhibitory Post-Synaptic Potential (IPSP)
**influx Cl- = downtake**
-counteracts EPSP
**-hyperpolarization** of neurotransmitter
100
Ionotropic Receptors
**open ion channels and ligand gated channels**
- neurotransmitter binds to receptor that is linked to an ion channel
- ion channels open → movement of ions across membrane (in/out)
\*features of the ion channel determine which ions flow through
\*post-synaptic membrane is depolarized or hyperpolarized, depending on what ions flow into the cell
1. Na+ driven transport of choline occurs
2. Acetylcholinesterase breaks down ACh
3. Nicotinic ACh receptor channel activation
4. Membrane depolarization
5. Action potential excitation
6. Muscle contraction
101
Metabotropic Receptors
**activates signal transduction pathway**
- secondary messengers produce post-synaptic response → increase intracellular Ca2+ via opening of ion channels
- neurotransmitter binds to receptor linked to signal transduction pathway
- determines possible activation or inhibition of downstream enzymatic pathway
- possibility of final cellular response
- increase Ca2+ / open + close of ion channels
1. Na+ driven co-transport of choline occurs
2. Acetylcholinesterase breaks down ACh
3. Muscarinic ACh receptor activation
4. Release of alpha GTP / G protein
5. Activation of inward K+ channel
6. Membrane hyperpolarization
7. Decrease in heart rate
102
Excitatory Neurotransmitters (amino acid derivatives)
G.A.S.
glutamate
aspartate
serotonin
103
Inhibitory Neurotransmitters (amino acid derivatives)
GABA
glycine
serotonin
104
Amine Neurotransmitters
dopamine
epinephrine
norepinephrine
acetylcholine (ACh)
histamine
105
Peptide Neurotransmitters
dynorphin
substance P
106
Termination of Synaptic Response
- Enzymatic degradation
- Diffusion away from postsynaptic receptors
- Re-uptake into presynaptic nerve terminal
- Desensitization of postsynaptic receptor to ligand
107
Neuromuscular Junction (NMJ) aka Motor End Plate
nerve ending location
- ending of action potential
- ACh released from nerve terminal acts at nicotinic receptors at NMJ
108
An action potential that travels DOWN the motor axon ALWAYS elicits ________ in muscle fibers and contraction of muscle fibers
action potentials
109
Contiguous Conduction
unmyelinated fibers
- A.P. spreads along every portion of the membrane
- travels slowly
110
Saltatory Conduction
myelinated fibers
- propagates A.P. much faster than contiguous conduction (50x faster)
- A.P. does not need to be regenerated along the whole axon
111
Multiple Sclerosis (M.S.)
myelin degenerates and cannot conduct A.P. as fast
-resulting nerve damage disrupts communication between the brain and the body
112
Synapse
junction between 2 neurons
- can also interact with muscle cells or gwinns
- site of neuronal communciation
113
Primary means in which one neuron directly interacts with another
synapse
114
Presynaptic Neuron
**sends the signal (action potential) towards synapse**
-converts electrical signal to chemical signal in order to cross the cleft
115
Synaptic Knob
contains the synaptic vesicles
116
Synaptic Vesicles
store the neurotransmitter & fuse with presynaptic membrane to release (exocytosis) neurotransmitter
117
Synaptic Cleft
space in between the presynaptic and postsynaptic neurons
118
What converts an **electrical** signal to a **chemical** signal?
presynaptic neuron
119
Postsynaptic Neuron
**receives the signal (action potential) and propagates away from synapse**
-receives chemical signal and generates electrical signal
120
What converts a **chemical** signal to an **electrical** signal?
Postsynaptic Neuron
121
Electrical Synapse
A.P. impulses conduct directly between adjacent cells through **gap junctions** (visceral, muscular, embryonic tissues)
**-bidrectional / fast**
-direct ionic current from one cell to the next
122
Chemical Synapse
**membranes are close but do not touch with the presence of synaptic cleft**
**-one directional / indirect transmission / slow** (transmission due to connection with synaptic cleft)
→arrival of nerve impulse
→depolarizing phase of nerve impulse opens voltage gated Ca2+ channels → Ca2+ influx in presynaptic terminal
→triggers exocytosis of synaptic vesicles and chemical release of hormone
→ ion channels open in postsynaptic membrane
123
Types of Chemical Synapses
- **axodendritic** (axon + dendrite)
- **axosomatic** (axon + soma)
- **axoaxonic** (axon + axon)
124
Spatial Summation
results from build up of neurotransmitter released simultaneously by several presynaptic end bulbs
125
Temporal Summation
one end bulb continues to release a neurotransmitter in rapid succession
126
Paracrines
exert effects on neighboring cells (local)
127
Neurotransmitters
short range
-diffuse across membrane and join to target cell (neuron, muscle or gland)
128
Hormones
long range
- secreted into the blood by endocrine glands in response to a signal
- exert effects on target cell that is a distance away
129
Neurohormones
hormones released into the blood by neurosecretary neurons
-blood distributes to the target cell
130
Myelin Sheath
concentric layers of protein alternating with lipid
- wrap around the axon 100+ times
- myelinated nerve fiber insulated by myelin sheath
- produced by Schwann cells outside of the CNS
- produced by oligodendrocytes inside the CNS
131
Classification of Nerve Fibers
**structure**: myelinated vs. unmyelinated
**distribution**: somatic nerve fibers (muscles) vs. autonomic nerve fibers (visceral)
**origin**: cranial nerves (brain) vs. spinal nerves
**function**: sensory nerve fibers (PNS to CNS - afferent) vs. motor nerve fibers (CNS to PNS - efferent)
**secretion of neurotransmitter**: adrenergic nerve fibers vs. cholinergic nerve fibers
132
NERNST Equation
used to calculate the value of **equilibrium potential** in a particular cell for a particular ion
**Vm = 61 / z x log base 10 x [C]o / [C]i**
**\*use Na+ or K+ to get as close to equilibrium potential as possible since they are most abundant ions**
\*significant for hyperkaelemia (high K+ in blood)
133
NERNST Equation: **Vm**
Vm = equilibrium potential for any ion
134
NERNST Equation: **Z**
Z = valence of ions (electrons in outer shell)
135
NERNST Equation: **[C]o**
concentration of ion X outside of the cell (mol)
136
NERNST Equation: **[C]i**
concentration of ion X inside of the cell (mol)
137
Hyperkaelemia
high K+ in blood
**-RMP shifted to a less negative value → more K+ outside of the cell**
- common in DKA → causes fatal arrythmia due to cell's ability to reach A.P. threshold much faster (increased excitability)
- K+ follows sugar; rapidly flows through the leaky channels outside of the cell
\> 6 K+ value = RISK
138
Mitochondria
major site of ATP production
139
Anaerobic Respiration
use 2 ATP + produce 2 lactic acid
140
Aerobic Respiration
use 2 ATP, produce 34 ATP
141
K+ channels activated → cell turns to _____ state
Repolarized
142
How steroid cholesterol affects the plasma membrane
\*acts as a temperature buffer in PM
**higher temp** → cholesterol packs tightly = less fluid membrane
**lower temp** → more fluid
143
Solvent
dissolving medium (water)
