Physio Chapter 4
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T or F: membrane voltage will always be measured from OUTSIDE the cell
False: Inside the cell
The ICF contains ____ of the body's water.
(this multiple choice question has been scrambled)
How much of the body's water are in the ECF? What are its component?
1/3 of the body's water = 3/4 are interstitial fluid + 1/4 plasma
T or F: Inside the cell contains more Sodium than potassium.
- False: inside the cell contains more potassium.
- Inside = 150mM K+ and 15mM Na+
- Outside = 5mM K+ and 150mM Na+
How are the sodium and potassium gradients being regulated within and outside the cell even though they are always against the homeostatic gradient?
Sodium and potassium pumps are keeping these levels using ATP.
Explain what happens to the cell membrane and potassium when the membrane is only permeable to potassium.
- The potassium will naturally want to leave the cell because the concentration of potassium outside is much lower than inside, so when it the membrane is permeable to K+, the ions leave and the charge inside the cell becomes more negative.
- The negative powers wans to then pull the K+ ions back inside, creating a balance
What is the charge inside the cell when the membrane is permeable to potassium?
Veqm K+ = -90mV
What happpens to the cell membrane and sodium when the membrane is only permeable to sodium? What is the net chage inside the cell?
- The sodium wants to go inside the cell, making inside the cell more positive.
- Veqm Na+ = +60mV
What is the typical resting potential voltage for the cell membrane typically around?
Vrest = -70mV
- 1. Soma - cell body
- 2. Dendrites - brings in information
- 3. axon
- 4. Axon Hillock
- 5. Synaptic terminals/boutons
- 6. Microtubules
What are the 4 characteristics of Graded Potentials? (according to notes)
- 1. Short-lived changes in membrane potential (voltage)
- 2. They're local: changes happens in portions of the membrane.
- 3. Typically occurs in the soma + dendrites
- 4. Continuously variable (positive or negative)
What are the 4 characteristics of Action Potential? (according to notes)
- 1. Long-lasting
- 2. Travels long distances
- 3. Found in the axons
- 4. "all or none" - either goes all the way to the end of the axon, or it won't go at all
What are the two volage gates for action potentials found along the axon?
- 1. Voltage K+ channel
- 2. Voltage Na+ channel
T or F: Voltage gated Na+ channels oen fast, so vast amounts of sodium ions can rush through
What is absolute refraction and what is the importance of it?
- This is when the cell cannot be excited again, a period of rest
- It is important because it keeps the action potential going in one direction by making sure multiple channels will not open randomly or too soon.
What material around the axon helps signals pass through the axon faster and more efficiently?
Why does the resting potential have a -70mV value?
When the membrane is at resting potential, it is more permeable to K+, which will make the potassium want to leave the cell (inside the cell = -90mV). However, during this time it is also somewhat permeable to sodium, which cancels some of the potential produced by the K+.
What is polarization?
any time membrane potential is other than 0 mV, is either positive or the negative direction
What is depolarization?
when the inside of the cell becomes LESS negative than at esting potential (with the potential moving closer to 0 mV
What is repolarization?
The membrane returns to resting potential after having been depolarized
What is hyerpolarization?
The membrane becomes more polarized the inside becomes more negative than at resting potential with the ppotential moving even farther from 0 mV
T or F: When a graded potential occurs locally in a nerve or muscle cell membrane, the rest of the membrane remains at resting potential.
What is a synapse? What are the 2 types?
- Juntions between presynaptic and postsynaptic neurons
- 1. electrical synapse
- 2. chemical synapse
Which type of synapse is most common? Where are both relatively found?
- Chemical is the most common
- Electrical synapses have been identified in the NS, and specialized locations such as the pulp of a tooth and retina of the eye.
In an electrical synapse, two neurons are connected by ____ junctions. Where are these kinds of junctions numerous in?
gap: smooth and cardiac muscle
- a) synaptic knob
- b) synaptic cleft
- c) synaptic vesicle
- d) presynaptic neuron
- e) postsynaptic neuron
Where is the subsynaptic membrane located? what is its significance?
On the postsynaptic neuron. It is where released neurotransmitters bind to because it contains specific protein receptors.
What is the definition of a chemical synapse? How are neurotransmitters transfered?
- It is where chemical messengers transmit information one way across a space seperating two neurons.
- 1. The axon terminal of the presynaptic neuron, which conducts its action potentials towawrd the synaptic knob.
- 2. The synaptic knob contains synaptc vesicles, which stores neurotansmitters.
- 3. The neurotransmitters exit the presynaptic neuron into the gap between the pre and postsynaptic neurons called the synaptic cleft.
What are the two types of synapses and how are they defined?
Excitatory synapse and inhibitory synapse: the type depends on the resulting permeability changes that occur when the neurotransmitter changes the subsynaptic receptor-channels.
In an excitatory synapse, what ions become permeable and how? Which ion is more prominent in moving across the membrane and why is this?
- Na+ and K+ are simultaneously allowed passage.
- - The Na+ will enter the cell, while the K+ moves outwards.
- - More Na+ will move into the cell ue to both the concentration and electrical gradients favoring it, while K+ only has the gradient forces working for it.
T or F: Due to increased sodium entering the cell at an excitatory synapse, this makes the cell most positive which brings it to threshold for an action potential.
False: too few channels are involved at a single subsynapptic membrane to permit adequate ion flow, the cell won't reach theshold, but instead bring it close to it. This makes the cell more ready for an action potential.
What NT does the nicotinic cholinergic receptor accept? And is it excitory or inhibitory?
What NT does the muscarinic cholinergic receptor take? is it excitory or inhibitory?
acetylcholine: both excitory or inhibitory
What kind of NT does AMPA receptors take? What kind of NT is it (what is it made of)? Is it Excitory or inhibitory?
Glutamate an amino acid, usually excitory
What kind of NT does NMDA receptor take? What kind of NT is it? excitory or inhibitory?
Glutamate, an amino acid, usually excitory
What is GABA? what does it do?
a NT that is usually inhibitory, opens choloride channels
What is serotonin? Where does it come from? 3 parts
a NT. Comes from indolamines -> typtophan -> 5H -> serotonin
What is the common name for epinephrine?
What is the common name for norepinephrine?
What is the adj. for adrenaline?
What are the type of adrenergic receptors? What are they receptors for?
- 1. alpha adrenergi receptors
- 2. beta adrenergic receptors
- for adrenaline
How do NTs become cleared from the post synaptic neuron? (3 ways)
- 1. Enzymes can break down NTs
- 2. reuptake: pumps that suck NTs back into presynaptic
- 3. diffusion out of synapse
Which NT is similiar to caffeine?
What NTs are peptides? (2)
What is signal transduction?
pertains to ho the signal from the NT gets translated into an action
How does signal transduction begin?
Stats with a receptor activating a G-protein.
How does PKA get activated during signal transduction?
- A receptor is activated by a ligand, which signals th G-protein to turn on Adenlyl cyclase.
- Adnelyl cyclase makes cAMP
- cAMP activates protein kinase A (PKA)
What are the benefits of 2nd messenger pathway? (3)
- 1. Amplification
- 2. Control: multiple 2nd messenger pathways can control another
- 3. Flexibility: some single ligands can produce different results; while in contrast, different ligands can produce the same effect.
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