M1 Study Guide Flashcards
1
Q
anterior
A
in front of; toward the front surface
2
Q
posterior
A
in back of; toward the back surface
3
Q
dorsal
A
toward the back of the human body
4
Q
ventral
A
toward the belly side of the human body
5
Q
superior
A
closer to the head
6
Q
inferior
A
closer to the feet
7
Q
cranial (cephalic)
A
toward the head end
8
Q
caudal
A
toward the rear or tail end
9
Q
rostral
A
toward the nose or mouth
10
Q
true anatomical position
A
body is erect.
head facing directly forward.
arms hanging down and lateral to trunk/torso with palms of hands facing forward.
legs slightly apart with feet/toes facing directly forward with feet flat on the ground.
11
Q
what are the 2 body cavities and what do they each contain
A
dorsal: contains CNS (brain and spinal cord).
ventral:
- thoracic (lungs and heart).
- abdominal (GI organs, kidneys, spleen, adrenal glands).
- pelvic (bladder/urethra, terminal portions of GI tract, reproductive organs).
12
Q
what do serous membranes do
A
line body cavities and organs
13
Q
parietal layer
A
outer layer of membrane lining interior wall of a body cavity
14
Q
visceral layer
A
inner layer of membrane lining the external surface of organ(s)
15
Q
serous cavity
A
thin space between parietal and visceral layers that contains a very small amount of fluid that acts as a surfactant to reduce friction between the 2 layers when they slide against each other
16
Q
parietal pleura
A
outer layer of the lungs
17
Q
visceral pleura
A
inner layer of the lungs
18
Q
cell biology/cytology
A
study of cellular structure
19
Q
cell physiology
A
study of cellular function
20
Q
2 types of imaging techniques
A
Scanning electron microscopy (SEM): offers 3d views that allows for study of surface features
Transmission electron microscopy (TEM): offers 2d views through thin-cut sections and is optimal for visualizing internal structures of a cell or within an organelle
21
Q
what is max resolution of light microscope
A
0.2 - 0.5 microns
22
Q
what can you visualize with a light microscope
A
mitochondrion
nucleus
lysosome
typical human cell
23
Q
what can you not visualize with a light microscope
A
ribosome
typical protein
plasma membrane
structures that form the cytoplasmic skeleton
24
Q
define nonmembranous organelles and list them
A
lack membranes and are in direct contact with cytoplasm.
ribosomes
centrosome/centrioles
cilia/flagella
cytoskeleton
nucleolus
25
define membranous organelles and list them
surrounded by 1 or 2 lipid bilayer membranes.
2 lipid bilayer membranes: nucleus (nuclear envelope) and mitochondria.
1 lipid bilayer membrane: lysosomes, peroxisomes, endoplasmic reticulum, golgi body, plasma membrane
26
structure of the nucleus
Largest organelle within a cell with round/ovoid body located near the cell center.
Double membrane nuclear envelope contains nuclear pores that allow molecules to pass between nucleus and cytoplasm.
No membrane-bound organelles in the nucleus.
Contains chromatin
27
function of the nucleus
stores and transmits genetic info in the form of DNA.
genetic info sent to cytoplasm where ribosomes read the codon sequence of mRNA to code for a serious of amino acids
28
structure of nucleolus
spherical, densely stained filamentous structure within the nucleus
28
function of nucleolus
site of ribosomal RNA (rRNA) synthesis and protein components of ribosomal subunits, which then move to the cytoplasm through nuclear pores
29
what are ribosomes and the types
Packages of rRNA and protein.
Types:
- Free ribosomes: throughout cytosol; synthesize proteins used inside the cell from mature mRNA.
- Membrane-bound ribosomes: attached to rough ER; synthesize protein needed for export or use within the cell membrane
- Mitochondrial proteins: produced by special ribosomes within mitochondria.
29
location and function of rough ER
continuous with nuclear envelope with attached ribosomes that synthesize, process and packages proteins for export from the cell or to cell membrane.
29
Structure of golgi apparatus
Cup-shaped, closely apposed, flattened, membranous sacs with associated vesicles typically situated near nucleus/rough ER.
Cis-face: side of protein entry
Cisternae: site of protein modification.
Trans-face: side of protein exit.
30
structure and function of smooth ER
Has no attached ribosomes.
Synthesizes phospholipids, steroids, and fats.
Functions in detoxifying harmful substances like alcohol.
30
function of golgi apparatus
Concentrates, modifies, and sorts proteins arriving from rough ER prior to their distribution via vesicles that will remain in the cell (lysosome) or to the outside of the cell via exocytosis
31
location and function of lysosomes
Formed in golgi complex and filled with digestive enzymes.
Pumps in H+ ions until internal pH reaches 5.0 (acidic).
Functions:
- digest foreign substances (ex. bacteria)
- digest/recycle components of the cell's organelles (autophagy)
- cell destruction (autolysis)
31
function of peroxisomes
contain enzymes (catalases) that oxidize toxic organic material (alcohol, aldehydes, hydrogen peroxide)
32
structure and function of mitochondria
Double membrane organelle with central cavity matrix and inner membrane (crista).
Mitochondrial DNA almost exclusively from mother as sperm mitochondria broken off during fertilization and fail to enter the egg cell.
Function: ATP generators and can self-replicate if needed
33
structure and function of cytosol
Takes up 55% of cell volume; contains 75-90% water.
Site of many important chemical reactions - production of ATP, synthesis of building blocks for organelles.
34
structure and function of cytoskeleton
Network of protein filaments through cytosol that are continuously reorganized that provides cell support and gives cell its characteristic shape.
Filaments types:
- Microfilaments (actin): locomotion and division
- Intermediate filaments (multiple proteins): anchor organelles
- Microtubules (tubulin): flagella, cilia, and centrosomes
35
location and function of centrosome
Near nucleus with 2 centrioles oriented perpendicular.
9 clusters of 3 microtubules (9+0 array).
Function: formation of cilia and flagella basal bodies; development of mitotic spindle during cell replication
36
general structure of cilia and flagella
Shaft contains pairs (doublets) of microtubules along with central pair (9+2 array).
Basal body derived from centriole, so microtubule arrangement is the same (ex. triplet microtubules in 9+0 array).
37
differences between cilia and flagella
cilia are short and multiple projecting from the cell membrane (respiratory cilia) and typically have coordinated movements (some cilia are non-motile) while flagella are long, single, and exhibit wavelike movements
38
main contents of cell membrane
Phospholipids.
Cholesterol and Glycolipids.
Proteins
39
composition of phospholipids
make up 75% of cell membrane lipids in bilayer configuration.
Polar parts: heads containing phosphate and glycerol.
- hydrophilic and face a watery environment (cytoplasm or external environment).
Nonpolar parts: fatty acid tails.
- hydrophobic and line up next to each other within the membrane.
Amphipathic
40
composition of cholesterol and glycolipids
Cholesterol (20% lipid composition) and glycolipids (5%) scattered among double row of phospholipid molecules.
Hydrophobic cholesterol contains stiff steroid rings and hide within the hydrophobic cell membrane (allows for cell rigidity) around the fatty acid tails of phospholipids.
41
types of proteins in the cell membrane
Integral proteins
Peripheral proteins
Transmembrane proteins Glycoproteins
42
Integral proteins
extend into or completely across cell membrane.
all are amphipathic with hydrophobic portions hiding among the phospholipid fatty acid tails
43
Peripheral proteins
lie proximal to the inside of the cell membrane within the cell's cytoplasm.
ex. G proteins = guanine nucleotide binding protein
44
Transmembrane proteins
Integral proteins extending completely across cell membrane.
Function
1. Channels
- aquaporins
- ion leak channels
2. Receptors
- ionotropic
- metabotropic
3. Enzymes
- adenylyl cyclase
- phospholipase C
Crucial in the activation of 2nd messengers intracellularly
45
Glycoproteins
Sugar portion facing extracellular fluid to form a glycocalyx, which protects the cell from being digested or, in the case of the corneal surface, also allows for tear film adherence
46
what type of structures are membranes
fluid structures (oil layer) and are self-sealing when punctured.
can rotate and move freely but need to stay in one-half of lipid bilayer because it is difficult for the hydrophilic portion to pass through hydrophobic core of bi-lipid layer
47
what is the lipid bilayer permeable to
nonpolar (uncharged) molecules, including oxygen, CO2, and steroids, as well as to very small amount of small, polar (charged) molecules like water.
flows through gaps that form in hydrophobic core of membrane as phospholipids move about
48
aquaporins
specialized membrane transporters that do water transport
49
what do very large molecules use to pass through the membrane
vesicular transport
ex. endocytosis and exocytosis
50
what is total body water mostly
intracellular fluid (about 2/3 volume)
51
what is extracellular fluid mostly
interstitial (about 3/4 of extracellular volume)
52
what needs to happen for homeostasis to be maintained
fluid intake - mostly obtained through eating and drinking - must roughly equal fluid output - mostly through urination and sweat
53
where is na+ and cl- conc. highest
plasma and extracellular fluid
54
where is k+ conc. highest
intracellular fluid
55
where is ca2+ conc highest
extracellular fluid and is vital in muscle contraction and the process involved in neurotransmitter release from the transmissive segment of a neruon
56
where are phosphate ions, proteins, and ATP conc. highest
intracellular
57
where is glucose conc. highest
outside cell as it passes into the cell for metabolism via glucose transporters
58
why are feedback loops important and what are the types
Important in maintaining a physiological condition (ex. body temp) within a normal range around a set point.
1. positive feedback: reinforcement of stimulus; requires major event to restore homeostasis
2. negative feedback: opposite action to stimulus to restore homeostasis; most common feedback loop of the two
59
what substances have a greater conc. outside the cell
O2, Na+, and Cl-
60
what substances have a greater conc. inside the cell
CO2, K+
61
chemical gradient
membranes maintain difference in conc. of a substance inside vs outside of the membrane
62
electrical gradient
membranes maintain a difference in charged ions between inside and outside of membrane
63
why is there a negative charge inside cell membrane and positive charge outside cell membrane in resting state
due to leakier k+ (non-gated) ion channels vs. other ion leak channels within the cell membrane
64
what impacts the RMP
cells type
65
equilibrium potential
Ion is in equilibrium (diffusion and electrical forces are equal so there is no net movement of an ion into or out of a cell).
Nernst equation.
Goldman-Hodgkin-Katz (GHK) equation.
66
Nernst equation
used to determine equilibrium potential that is necessary to balance an ionic conc. across plasma membrane so net movement of that ion is zero.
Assumes membrane is perfectly permeable to specific ion.
67
Goldman-Hodgkin-Katz (GHK) equation
incorporates ion conc. into it; provides more accurate calc. of the RMP for a particular cell type
68
types of passive transport
osmosis.
simple diffusion.
facilitated diffusion.
69
osmosis
Net movement of water through selectively permeable membrane.
The higher the osmolarity, the lower the water conc. and vice cersa
70
osmotic pressure
required min. pressure applied to a solution to stop osmosis
71
non-penetrating solutes
cannot cross membrane from extracellular environment unassisted
72
isotonic solution
no change in cell shape
73
hypertonic solution
crenation of cell = cell shrinkage
74
hypotonic solution
cell expansion.
lysis/hemolysis if expansion is great enough to rupture cell membrane
75
simple diffusion
Water and solutes can disperse in presence/absence of membrane down conc. gradient.
When molecules are evenly distributed, equilibrium has been reached.
76
influences on diffusion rate: different in conc.
the greater the difference in conc., the faster the rate of diffusion
77
influences on diffusion: temperature
the higher the temperature, the faster the rate of diffusion
78
influences on diffusion: size
the larger the size of the diffusing substance, the slower the rate of diffusion
79
influences on diffusion: surface area
increase in surface area, increases the rate of diffusion
80
influences on diffusion: distance
increasing diffusion distance, slows rate of diffusion
81
permeability coefficients
measures the rate at which molecules diffuse across membranes (simple diffusion)
82
major factor limiting diffusion across a membrane
Hydrophobic interior of its lipid bilayer.
However, O2, CO2, fatty acids, and steroid hormones are all nonpolar molecules that diffuse rapidly through membranes (simple diffusion).
Lipophilic (lipid-loving) substances move through phospholipid bilayer with relative ease.
Polar molecules do not diffuse readily through plasma membrane and vast majority require protein transporter
83
diffusion types
Simple: involves no transport mech. and small, uncharged, nonpolar molecules can readily pass thorugh phospholipid bilayers of plasma membrane.
Facilitated: requires membrane protein transporter via ion channels or carrier protein
84
what ions use transmembrane protein channels to diffuse into and out of cells down their respective conc. gradient
Na+, K+, Cl-, Ca2+
85
what is specificity determined by
pore size of the channel, charge, and binding sites
86
what are the 2 types of channels
non-gated (leak) channels.
gated channels.
87
Non-gated (leak) channel qualities
always open (ions and water)
88
Gated channel qualities
Open and close in response to a stimulus result in neuron excitability.
1. Voltage-gated channels: open in response to change in voltage; action potentials
2. Chemical-gated/Ligand-gated channels: open and close in response to specific chemical stimulus (ex. hormone, neurotransmitter, ion); graded potentials (EPSPs and IPSPs)
3. Mechanically-gated channels: will open with mechanical stimulation; action potentials
89
Sodium channels
Mediate fast depolarization (rapid influx of Na+ down its electrochemical gradient) and conduct electrical impulses throughout excitatory cells like neurons and muscles.
Na+ channel blockers slow rate and amplitude of the initial, rapid depolarization of an action potential reduces cell excitability and conduction velocity
90
Examples of Na+ channel blockers
Class I antiarrhythmic medications, anesthetics, TTX/tetrodotoxin.
Irreversibly binds to binding site on Na+ channel, blocking on influx into cell preventing depolarization; highly neurotoxic; found in several species of bacteria and amphibians like certain newts.
Pufferfish
91
Potassium channels
K+ outflow mediates hyperpolarization at a slower rate than depolarization
92
K+ channel blockers
TEA (tetraethylammonium): used to treat heart arrythmias.
HTN: only used in research.
KCl: lethal execution procedure - blocks repolarization
93
Facilitated diffusion
many molecules (ex. glucose) are too large/charged to get into the cell without help.
protein transporters (carriers) are specific to a molecule and brings them into and out of cells by conformation changes.
do not require ATP
94
active transport
utilizes ATP or an ion (typically Na+) to drive substances against conc. gradients (ex. low to high conc.)
95
primary active transport
ATP is hydrolyzed to ADP to produce energy needed to drive the pump
96
primary active transport pumps
Na+/K+ ATPase pump: in every cell; helps maintain membrane potential; pumps ions against their gradient - 3 Na+ out and 2 K+ in with ATP.
H+ ATPase pump (proton pump).
Ca2+ ATPase pump.
97
secondary active transport
use of electrochemical gradient across membrane via transporter ion
98
symporters (cotransporters)
symport secondary active transport.
move 2 molecules in same direction across the cell membrane - one down its gradient and the other against its conc. gradient.
99
antiporters (countertransporters)
antiport secondary active transport.
move 2 molecules in opposite directions across the cell membrane - one down its gradient and the other against its conc. gradient.
100
2 types of vesicular transport
Endocytosis: bringing something into the cell by phagocytosis (cell eating) or pinocytosis (cell drinking).
- receptor-mediated endocytosis: something binding to a receptor on the cell membrane.
Exocytosis: contents released from cell across cell membrane.
- vesicles form inside cell then fuse to cell membrane where contents are released into extracellular.
- cell membrane of vesicle replaces cell membrane that is lost during endocytosis
101
what is the extracellular fluid rich in
Na+ and Cl- ions
102
what is the intracellular fluid rich in
K+, negatively-charged proteins and amino acids, etc.
103
where do graded potentials occur
receptive segment of the neuron (dendrites and soma)
104
what binds to signal a graded potential
binding a ligand to an ion channel.
ex. neurotransmitter, hormone, etc.
105
what is the amplitude of response dependent on in a graded potential
strength of stimulus
106
is a graded potential signal propagation long or short
short distance.
ex. synapse to neuron cell body
107
where are individual graded potentials summated and what happens if it reaches threshold
summated at initial segment of the neuron.
if membrane potential reaches threshold an action potential will be initiated in the initial segment of a neuron
108
what happens immediately prior to depolarization
stimulus from multiple graded potentials in the soma changes membrane charge at the axon hillock (initial) from -70 to -55
109
what happens when membrane reaches threshold
voltage-gated Na+ channels rapidly open and Na+ streams into the cell as the membrane potential changes rapidly to +30 mV
110
what happens at full depolarization
full depolarization = +30 mV.
voltage-gated Na+ channels are inactivated: remain open but Na+ cannot pass through anymore due to a gate at the entrance.
voltage-gated K+ channels begin to slowly open and repolarization begins: membrane potential moves towards negative charge at a slower rate than what was experienced with depolarization.
111
what happens during repolarization
outflow of K+ from the cell returns the membrane potential back to -70 mV.
112
what causes hyperpolarization
too much K+ leaves the cell and the membrane potential reaches -90 mV before returning to -70 mV with the help of ion leak channels and the Na+/K+ ATPase pump
113
what happens when the cell is polarized
both voltage-gated Na+ and K+ channels close.
back to -70 mV.
cell is ready for next action potential.
114
what is saltatory conduction
propagating impulse.
local changes in the charge of the axonal surface and axoplasm between nodes of Ranvier move depolarization/repolarization process down to the next node and so on, all the way to the neuron's synapse with a downstream neuron or effector
115
when does continuous conduction occur
no nodes (ex. unmyelinated axon)
116
what is the refractory period
time during an action potential when a neuron generally cannot generate another action potential
117
absolute refractory period
not even the strongest stimulus will generate another action potential even when the membrane potential is above the threshold
118
relative refractive period
strong-enough stimulus to reach threshold may generate another action potential even if the cell has yet to return to the polarized state (RMP)
119
origin of graded and action potentials
graded: arise on dendrites and cell bodies.
action: arise only at trigger zone on axon hillock
120
channel types of graded and action potentials
graded: ligand or mechanically-gated channels.
action: voltage-gated ion channels
121
conduction of graded and action potentials
graded: localized (non-propagated).
action: propagated along axonal surface
122
amplitude of graded and action potentials
graded: can vary depending on strength of stimulus.
action: constant (all-or-none)
123
duration of graded and action potentials
graded: as long as stimulus lasts.
action: about 1 ms
124
is there a refractory period for graded/action potentials
graded: no.
action: yes, due to nature of voltage-gated channels
125
what is continuous conduction
step-by-step depolarization of each portion along the entire length of the axolemma of unmyelinated axons
126
what is saltatory conduction
depolarization occurs only at the nodes of Ranvier of myelinated axons where there is a high density of voltage-gated ion channels.
- current carried by ions flows through extracellular fluid from node-to-node down the axon.
- propagation speed of a nerve impulse not related to stimulus strength.
127
types of fibers
A fibers: largest and provide fastest impulse propagation; myelinated (somatic sensory and motor fibers).
B fibers: medium-sized; somewhat myelinated (autonomic).
C fibers: smallest with slowest impulse propagation; unmyelinated (somatic sensory and autonomic fibers).
128
what type of axons allow for fastest/slowest conduction of an impulse
fastest conduction: myelinated and large-diameter axons.
slowest conduction: unmyelinated and small-diameter axons.
129
what are synapses
locations where an axon of an upstream (presynaptic) neuron 'communicates' with the dendrite(s) of a downstream (postsynaptic) neuron or effector (ex. muscle, gland, etc.)
130
what are the types of synapses
Mechanical synapses: channels pulled open by physical movement.
- ex. cochlear hair cells, muscle spindles.
Electrical synapses: currents (ions) pass through gap junctions rapidly between bound presynaptic and postsynaptic neurons
- ex. cardiac and smooth muscle, retina.
Chemical (ligand) synapses: most common type; presynaptic neuron contains synaptic vesicles (containing neurotransmitter), mitochondria, and the active zone while postsynaptic neuron is separated by synaptic cleft and contains receptors that bind to a specific neurotransmitter
131
where are neurotransmitters synthesized and stored
Synthesized: axon terminal.
Stored: protein-coated (clathrin) membranous vesicles.
- Vesicles formed by budding and pinching of cell membrane during endocytosis.
- Vesicles filled with neurotransmitter - manufactured within neuron or recycled from synaptic cleft, such as choline from enzymatic degradation of acetylcholine by acetylcholinesterase.
- Vesicles are loosely docked to active zones within presynaptic cell by SNARE proteins.
132
what happens when voltage-gated Ca2+ channels open
allows for influx of ions down their conc. gradient into the presynaptic axon terminal
133
what does Ca2+ influx allow for
binding of these ions to synaptotagmin, which interacts with SNARE proteins embedded in the cell membrane, allowing for vesicle to the presynaptic axon terminal membrane and release of the neurotransmitter into the synaptic cleft.
134
what is a MEPP
MEPP = minimum end plate potential.
quantum of neurotransmitter released from a vesicle is required to initiate even smallest potential possible on postsynaptic cell
135
what do multiple quanta neurotransmitter generate
multiple MEPPs which may trigger a graded potential
136
what does the summation of multiple excitatory graded potentials generate
action potential in the initial segment if the membrane potential has at least reached the threshold
137
ways neurotransmitter removal can occur to stop the signal
1. actively transported back into presynaptic axon terminal ('reuptake') - some drugs like Prozac inhibit reuptake of neurotransmitter serotonin.
2. transported to nearby glial cells for degradation.
3. diffuses down conc. gradient away from receptor site.
4. enzymatically degraded (ex. acetylcholinesterase degrades neurotransmitter acetylcholine).
138
why are graded potentials that generate in the receptive segment either excitatory or inhibitory
do not require a threshold stimulus unlike action potentials.
139
EPSPs vs. IPSPs
EPSPs result in greater influx of Na+ into cell vs. outflow of K+ resulting in mem. potential, becoming more pos / less neg than resting membrane potential (depolarization).
IPSPs result in greater outflow of K+ and influx of Cl- vs. Na+ influx resulting in net hyperpolarization of the cell (membrane potential becomes more neg than resting membrane potential).
140
spatial summation
numerous EPSPs, IPSPs (or both) are initiated by different presynaptic neurons around same time
141
temporal summation
numerous EPSPs or IPSPs (not both) are initiated by same presynaptic neuron.
Example 1: presynaptic neuron will initiate EPSPs on postsynaptic neuron while another presynaptic neuron will initiate IPSPs on same postsynaptic neuron.
Example 2: presynaptic neuron will initiate EPSPs on postsynaptic neuron while another presynaptic neuron will also initiate EPSPs on the same postsynaptic neuron.
Example 3: presynaptic neuron will initiate IPSPs on postsynaptic neuron while another presynaptic neuron will also initiate IPSPs on same postsynaptic neuron.
142
result of 2 simultaneous EPSPs
produce greater EPSP
143
result of 2 simultaneous IPSPs
produce greater IPSP
144
result of IPSP and EPSP
cancel each other out
145
what do 2 EPSPs elicited in rapid succession sum to
produce larger EPSP
146
what do 2 IPSPs elicited in rapid succession sum to
produce larger IPSP
147
different types of circuits neural pathways can involve
diverging
converging
reverberating
parallel-after-discharge
148
myasthenia gravis
Autoimmune disease: body produces antibodies against Ach receptor.
- Damage to Ach receptor affects neurotransmission to muscles, and pt. can present clinically with symptoms of diplopia (double vision) and/or ptosis (droopy eyelid).
- Treatment: inhibitor of acetylcholinesterase that allows more time for Ach to bind to still-functioning Ach postsynaptic receptors.
149
multiple sclerosis (MS)
Autoimmune disease: affects neurotransmission by producing antibodies against myelin sheath of myelinated axons.
- Plaques form in white matter of CNS.
- Optic nerve can be affected as its myelinated - pt. can present with color vision defects, blurred vision, peripheral vision defects
150
what do botox injections block
synaptic release of excitatory neurotransmitter from presynaptic axon terminal which ultimately relaxes muscle.
ex. removes wrinkles, relieves eyelid spasms
151
what are neurotransmitters synthesized by and stored in
synthesized by neurons.
stored in synaptic vesicles in presynaptic axon terminal (knobs).
152
what are neurotransmitters released by
released from vesicles that are fused to the membrane of the synaptic knob secondary to the actions of Ca2+, synaptotagmin, and SNAREs
153
where do neurotransmitters bind
to receptor on postsynaptic neuron (or effector) as first messenger
154
what do neurotransmitters trigger
physiological response downstream by initiating graded excitatory or inhibitory postsynaptic potential (EPSPs and IPSPs)
155
what neurotransmitters trigger EPSPs
excitatory
156
what neurotransmitters trigger IPSPs
inhibitory
157
what are neuromodulators and what can they act as
Substances.
Agonists: mimicking action of neurotransmitter.
Antagonists: blocking action of neurotransmitter.
Facilitators: enhancing effect of neurotransmitter.
Inhibitors: reducing effect of neurotransmitter.
158
what binds to synaptic receptors
ligands
159
Ionotropic receptors
Ligand binds to an ion-channel receptor, rapidly opening the channel and allowing for influx of that ion through the channel into or out of postsynaptic cell.
Quick acting.
Response quickly tapers off.
160
Metabotropic receptors
Water-soluble ligands binds to receptor which triggers G-protein - 2nd messenger mech. that activates the opening of ion channels of another integral protein within cell membrane allowing for influx of ions into or out of postsynaptic cell.
Slower acting.
Response lasts longer than ionotropic.
161
what do g proteins serve as
a 'switch' to couple a receptor to an ion channel in the cell membrane
162
general steps of g proteins
1. Ligand binds to transmembrane receptor and results in change in its conformation.
2. Following receptor conformation, GDP molecule bound to g protein is replaced with GTP, which activates g protein.
3. activated g protein binds to enzyme that is embedded in cell membrane, which activates/inhibits this enzyme.
- one enzyme/ion channel is activated, GTP on g protein alpha subunit is cleaved into GDP and phosphate; g protein is now inactivated.
4. specific 2nd messenger is activated by enzyme when bound by g protein
5. 2nd messenger then activates particular protein kinase which will stimulate (or inhibit) signal pathways within cell
163
what are the specific 2nd messengers activated by the enzyme when bound by g protein
Cyclic AMP (cAMP).
Cyclic GMP (cGMP).
Diacylglycerol (DAG).
Inositol triphosphate (IP3).
Ca2+.
Arachidonic acid.
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