Quiz #1: Neurons and Action Potentials (6) Flashcards
What are the components of total body fluid?
- Intracellular fluid (2/3)
- Extracellular fluid (1/3)
a. Plasma (1/5)
b. Interstitial fluid (4/5)
c. Minor ECF (lymph/transcellular fluid)
What are the factors influencing the rate of net diffusion in a substance across a plasma membrane?
- concentration gradient
- distance
- surface area of membrane
- lipid solubility
- molecular weight
What happens to the net diffusion when you increase the distance?
Decreased rate of net diffusion
What happens to the net diffusion when you increase concentration gradient of a substance?
Higher rate of net diffusion
What happens to the net diffusion when you increase the surface area of a membrane?
Higher rate of net diffusion
What happens to the net diffusion when you increase lipid solubility
Higher rate of net diffusion
What is tonicity?
the effect a solution has on cell volume
What happens to the net diffusion when you increase molecular weight of a substance?
Decreased rate of net diffusion
What is the osmolarity of ECF when it is isoosmotic?
Equal to RBC
What is the osmolarity of ECF when it is hyperosmotic?
Higher than RBC
What is the osmolarity of ECF when it is hypoosmotic?
Lower than RBC
What is the net diffusion of water in isoosmotic solution?
zero
What is the net diffusion of water in hypoosmotic solution?
into the RBC
What is the net diffusion of water in hyperosmotic solution?
Out of the RBC
What is the shape of the RBC in isoosmotic solution?
normal
What is the shape of the RBC in hypoosmotic solution?
swells
What is an isoosmotic effect on a RBC?
Isotonic
What is the shape of the RBC in hyperosmotic solution?
shrinks
What is an hypoosmotic effect on a RBC?
hypotonic
What is an hyperosmotic effect on a RBC?
hypertonic
What are the two types of transport of molecules across the plasma membrane?
- Simple diffusion
- Assisted membrane transport
What are the two types of assisted membrane transport?
- Carrier-mediated transport
- Vesicular transport
What are the two types of vesicular transport?
- Exocytosis
- Endocytosis
What are the two types of carrier-mediated transport?
- facilitated diffusion
- active transport
What are the two types of facilitated diffusion?
- channels
- carriers
Why is there the saturation of assisted membrane transport?
Due to the limited amount of carriers of facilitated diffusion
What are the two types of active transport?
- primary
- secondary
What are the changes to the membrane potential?
- Depolarization
- Repolarization
- Hyperpolarization
Where does K+ move and what does it do?
To the ECF
ECF becomes more positive
ICF becomes more negative because membrane is impermeable to A-
Where does Na+ move to and what does it do?
Na+ moves to ICF
ICF becomes more positive
The ECF becomes more negative due to negatively charged ions (like Cl-)
What is repolarization?
- return to resting potential after depolarization
What is depolarization?
- decrease in potential
- membrane becomes less negative
What is hyperpolarization?
- increase in potential
- membrane more negative
What is resting potential?
- potential at which the membrane doing nothing rests at
Are the voltage gate Na+ channels and K+ channels open or closed at resting potential?
Voltage gated Na+ channels: closed
Voltage gated K+ channels: closed
Are the voltage gate Na+ channels and K+ channels open or closed at depolarization (before threshold)?
Voltage gated Na+ channels: closed
Voltage gated K+ channels: closed
Are the voltage gate Na+ channels and K+ channels open or closed at depolarization (after threshold)?
Voltage gated Na+ channels: OPEN
Voltage gated K+ channels: closed
Are the voltage gate Na+ channels and K+ channels open or closed at repolarization?
Voltage gated Na+ channels: closed
Voltage gated K+ channels: OPEN
Are the voltage gate Na+ channels and K+ channels open or closed at hyperpolarization?
Voltage gated Na+ channels: closed
Voltage gated K+ channels: OPEN (for first half)
What is the membrane permeability during resting potential?
close to zero
What is the membrane potential throughout an action potential?
Resting: -70mV
Depolarization (to thres.): >-70 to -50
Depolarization (after thres): >-50 to +30
Repolarization: <+30 to -70
Hyperpolarization: <-70
What is the membrane permeability during depolarization (to threshold)?
high for Na+
What is the membrane permeability during depolarization (after threshold)?
high for Na+
What is the membrane permeability during repolarization?
high for K+
What is the membrane permeability during hyperpolarization
high for K+
What is the one stage the voltage gated Na+ channels are open?
Depolarization (after threshold)
What is the 1.5 times the voltage gated K+ channels are open?
repolarization
hyperpolarization (1st half)
What are the steps of a neuron receiving a signal?
- input zone
- trigger zone
- conducting zone
- output zone
What is the input zone of a neuron
receives incoming signals from other neurons through dendrites
What is the trigger zone?
Initiates action potentials in axon hillock
What is the conducting zone?
conducts action potentials in undiminishing fashion over long distances
axon
What is the output zone?
Where neurotransmitters are released from axon terminals that influences other cells
A stronger stimuli will generate:
a higher frequency of action potentials
A stronger stimuli in a region causes more neurons to reach _________.
threshold
What is contiguous conduction?
An action potential moves step-by-step along an UNMYELINATED axon, depolarizing each successive segment of the axonal membrane
What is the process of continuous conduction?
- previous active ares are returned to resting potential (in refractory period)
- adjacent area that was brought to threshold by local current flow now active at peak of action potential
- new adjacent inactive area into which depolarization is spreading will soon reach threshold
- remainder of axon remains at resting potential
What are the two parts of the refractory period?
- absolute refractory period
- relative refractory period
What is the absolute refractory period?
Brief period of time after an action potential when a neuron is unable to send more action potentials, no matter how strong the stimulus
What is the relative refractory period?
Period of time that occurs after an action potential when a cell membrane changes to an unexcitable state and gradually returns to its resting state
What is the difference between absolute refractory period and relative refractory period?
During the absolute refractory period, a new action potential cannot be elicited. During the relative refractory period, a new action potential can be elicited under the correct circumstances.
What specifically happens in the ion influx during the absolute refractory period?
Na+ enters
What happens to the ion influx during the relative refractory period?
K+ leaves
What is saltatory conduction?
Process that allows action potentials to travel quickly down myelinated axons by jumping from one node of Ranvier to the next
What is myelination?
- axons covered with myelin
- formed by glial cells
- CNS: oligodendrocytes
- PNS: schwann cells
What are some common neurotransmitters?
Achetylcholine
Norepinephrine
Dopamine
Serotonin
Glutamate
GABA
Glycine
What the the things that carry NT called?
synaptic vesicles
What is the gap between the axon terminal presynaptic neuron and dendrite of the postsynaptic neuron called?
synaptic cleft
What causes the release of neurotransmitters?
Calcium influx
What are the types of neurotransmitter receptors?
- ligand-gated ion channels
- g-protein coupled receptors
Ligand-gated ion channel example
- NT (ACh) released from presynaptic neuron activated nicotinic ACh receptors on the postsynaptice cell (msucle fiber)
activation = increase permeability to Na+ and K+ - cell depolarizes
- muscle contraction
G protein-coupled receptor example
- ACh binds muscarinic ACh receptors which activated G protein-coupled receptors on the postsynaptic membrane
- Opens K+ channels
- Posysynaptic membrane hyperpolarizes
- excitation of cells is inhibited
_____________ receptors are classified as ligand-gated ion channels while ____________ receptors are G-protein-coupled receptors.
- nicotinic
- muscarinic
Activation of nicotonic receptors does what?
increase Na+ and K+ permeability
Activation of muscarinic receptors does what?
increases K+ permeability
What is the outcome of a nicotinic receptor?
depolarize membrane potential
muscle contraction
What is the outcome of a muscarinic receptor?
hyperpolarize membrane potential
reduce force and rate of contraction
What is convergence of input?
one cell is influenced by many others
What is divergence of output?
one cell influences many others
What is grand postsynaptic potential?
the total potential in the postsynaptic neuron is a sum of all EPSPs and IPSPs occurring approximately at the same time
What does EPSP stand for and what does it mean?
excitatory postsynaptic potential (EPSP)
postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential
What is IPSP?
Inhibitory postsynaptic potentials (IPSPs)
Type of synaptic potential that make it less likely for a postsynaptic neuron to generate an action potential
What are the types of grand postsynaptic potential?
- no summation
- temporal summation
- spacial summation
- EPSP-IPSP cancellation
What is no summation?
Addition of all potentials is not enough for action potential
nothing cancels out just not enough to reach threshold potential
What is temporal summation?
Temporal summation involves a single presynaptic neuron rapid-firing signals to a single postsynaptic neuron’s synapse.
Because the signals are received in rapid succession, they compound into a greater signal
What is spatial summation?
Spatial summation involves multiple presynaptic neurons simultaneously sending signals to a single neuron
What is EPSP-IPSP cancellation?
One excitatory and one inhibitory signal cancel each other out for no summation
What is a graded potential?
Small change in the membrane potential of a neuron that occurs in response to sensory input or stimuli
Magnitude of the graded potential is determined by the strength of the stimulus, and can be either excitatory or inhibitory
Every stimulus (big or small) elicits a response
What is a neuromuscular junction?
Specialized synapse that connects the end of a motor nerve to a muscle
SLIDE QUESTION: Select the TWO conditions in which the rate of net diffusion across a cell membrane of a substance would be highest.
A. Decrease in the concentration gradient of the substance
B. Increase the thickness of the membrane
C. Increase the surface area of the membrane that is available for diffusion
D. Increase the lipid solubility of the substance
E. Increase the molecular weight of the substance
C/D
SLIDE QUESTION: What happens to the charge of the cell when the cell membrane is more permeable to Na+?
Depolarization (charge increases and becomes more positive)
SLIDE QUESTION: What happens to the charge of the cell when the cell membrane is more permeable to Na+?
A. Reverse polarize
B. Hyperpolarizes
C. Depolarizes
D. Repolarize 39
C
SLIDE QUESTION: Excitatory postsynaptic potentials are considered as ___ potentials.
A. Action
B. Graded
B. Graded
SLIDE QUESTION: Excitatory postsynaptic potentials causes membrane ___.
A. Depolarization
B. Repolarization
C. Hyperpolarization
A. Depolarization
