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When the neuron is at its resting potential the fluid inside the axon has what?
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When a neuron is in a resting state the majority of the particles in the fluid surrounding the neuron are?
polarized
What affect does lowering extracellular calcium have on the resting membrane potential of a neuron?
Low calcium levels in the extracellular fluid increase the permeability of neuronal membranes to sodium ions, causing a progressive depolarization, which increases the possibility of action potentials. These action potentials may be spontaneously generated, causing contraction of skeletal muscles (tetany).
The all-or-none principle states that?
In the simplest sense, the all-or-none principle of neuronal firing means that a neuron will either fire or it won't, there is no "half" firing. When a neuron receives excitatory input, its sodium (Na) channels open and allow Na to flow into the cell, depolarizing it (a resting neuron has a membrane potential of -65mV relative to extracellular fluid outside the cell). Once the neuron has been sufficiently excited above some threshold (typically -55mV), the cell fires, or sends an action potential down its axon to its terminal button. This electrical signal causes a series of chemical actions within the cell which results in neurotransmitters being released from the cell, to be picked up by other neurons. As long as a neuron reaches the threshold, it will always result in a large influx of Na ions, bringing the membrane potential to about +40mV, which will propagate down the cell as an action potential. If the neuron does not reach this threshold, it will not depolarize or create an action potential.
What is the importance and function of cytosol to the brain?
Cytosol is the fluid found inside cells and is the medium where cellular metabolism takes place. It has a slightly different composition to the fluid found outsides cells (extracellular fluid). In neurons, this difference in fluid composition is critical for cell signaling because it creates an electrochemical potential gradient across the cell membrane. When ions flux in and out of the cell (driven by chemical gradients and 'ion pumps') their charge alters the electrical potential difference across the cell membrane (i.e., think of the membrane as an insulator separating positive and negative charges). If enough positive charge enters a neuron then it will fire (release it's neurotransmitters).
What is the purpose of the action potential?
An action potential can also be called a nerve impulse which is known to be stimulated by an external stimuli or upon internal excitation.This action potential travels through a neuron and involves charged ions (the key ones are sodium ions and potassium ions) that cross the membrane barrier of the neuron.In the longitudinal section of the axon of the neuron (the part that carries the signal which may be covered in Schwann cells to protect the it) the action potential cycle occurs.There are four main stages: The Resting Membrane Potential, Depolarization, Repolarization, and the Refractory Period.In the Resting Membrane Potential Stage there is an active force that maintains the resting membrane potential at -70 mV. This active force is the Sodium Potassium Pump where three sodium ions leave the nerve cell and two potassium ions enter. With the Sodium Potassium Pump, it transports these ions actively and so ATP is required. In addition to the Sodium Potassium Pump, there are voltage-sensitive potassium slow leak channels that are involved with passive transport and there are also voltage sensitive sodium gates that are passive sodium channels. They are normally impermeable to sodium however it can't pass through unless there is an electrical current to open it.In the Depolarization Stage, an external stimuli occurs altering the tertiary structure of sodium gates allowing the nerve cell membrane to become more permeable to sodium than potassium. Therefore, sodium floods in passively making the extracellular fluid (ECF) more negative and the intracellular fluid (ICF). Now the voltage inside the cell is +50 mV compared to the previous stage where it was -70 mV.Once the cell has reached a voltage of +50 mV, sodium gates close and so the inflow of sodium ions into the cell are discontinued. Because of the altered concentration gradient of ions in the Depolarization Stage, it causes the potassium channels to alter their shape. As a result, there is an inflow of potassium ions outside of the cell and the inside becomes negative again. This stage is known as the Repolarization Stage. This prevents the signal from going backwards. The voltage inside the cell is now at -80 mV.In the last stage, Refractory Period, the Sodium Potassium Pump actively re-establishes the resting membrane potential. It takes time to reestablish the sodium and potassium concentrations to -70 mV.Please note that depolarization cannot occur until the resting membrane potential is reached (-70 mV).As an aside, the action potential follows the All or None Principle. This means that larger signals do not create larger action potentials. A neuron must always reach -70 mV before the signal is passed along a neuron. Therefore, the action potential will occur fully or not at all.The action potential is an electrical event occurring when a stimulus of sufficient intensity is applied to a neuron or muscle cell, allowing sodium to move into the cell and reverse the polarity.Normally neurones (neurons, or nerve cells) maintain a resting potential of -70mV across their membrane by the active pumping of 3Na+ ions out of the cell for every 2 K+ ions pumped into the cell by a Na+/K+ pump. When the neurone is stimulated, sodium ion channels open in the membrane and sodium ions flood in to the cell down an electrochemical gradient by diffusion, increasing the potential of the cell to +40mV. This is called depolarisation. At this point the sodium channels close, and potassium ion channels open. Potassium ions flood out of the cell down their electrochemical gradient, decreasing the cell's membrane potential. This is called repolarisation. There is a slight overshoot where too many potassium ions diffuse out of the cell, and there is hyperpolarisation where the cell's membrane potential falls below its normal -70mV, but this is corrected and the resting potential is once again restored. This is the sequence of events that makes up a single action potential. Action potentials are transmitted by saltatory conduction in the neurone, and impulses jump from node to node along the axon of the neurone.
When a neuron is in a resting state the majority of the particles in the fluid surrounding the neuron are?
polarized
What would happen to a resting membrane potential if the sodium potassium transport pump was blocked?
During depolarization, sodium (Na) rushes into the neuron through Na channels (at the Nodes of Ranvier between the bundles of myelin "insulation"). Less Na in the extracellular fluid would mean there would be less to rush in. So, the neuron would not be depolarized as well. The resting membrane potential would be more positive on the inside.
What affect does lowering extracellular calcium have on the resting membrane potential of a neuron?
Low calcium levels in the extracellular fluid increase the permeability of neuronal membranes to sodium ions, causing a progressive depolarization, which increases the possibility of action potentials. These action potentials may be spontaneously generated, causing contraction of skeletal muscles (tetany).
The all-or-none principle states that?
In the simplest sense, the all-or-none principle of neuronal firing means that a neuron will either fire or it won't, there is no "half" firing. When a neuron receives excitatory input, its sodium (Na) channels open and allow Na to flow into the cell, depolarizing it (a resting neuron has a membrane potential of -65mV relative to extracellular fluid outside the cell). Once the neuron has been sufficiently excited above some threshold (typically -55mV), the cell fires, or sends an action potential down its axon to its terminal button. This electrical signal causes a series of chemical actions within the cell which results in neurotransmitters being released from the cell, to be picked up by other neurons. As long as a neuron reaches the threshold, it will always result in a large influx of Na ions, bringing the membrane potential to about +40mV, which will propagate down the cell as an action potential. If the neuron does not reach this threshold, it will not depolarize or create an action potential.
What is the importance and function of cytosol to the brain?
Cytosol is the fluid found inside cells and is the medium where cellular metabolism takes place. It has a slightly different composition to the fluid found outsides cells (extracellular fluid). In neurons, this difference in fluid composition is critical for cell signaling because it creates an electrochemical potential gradient across the cell membrane. When ions flux in and out of the cell (driven by chemical gradients and 'ion pumps') their charge alters the electrical potential difference across the cell membrane (i.e., think of the membrane as an insulator separating positive and negative charges). If enough positive charge enters a neuron then it will fire (release it's neurotransmitters).
What is the fluid inside the cell?
The fluid inside the cell is the cytoplasm
Is a crate resting on a loading ramp an example of static friction or fluid friction?
me
What is the purpose of the action potential?
An action potential can also be called a nerve impulse which is known to be stimulated by an external stimuli or upon internal excitation.This action potential travels through a neuron and involves charged ions (the key ones are sodium ions and potassium ions) that cross the membrane barrier of the neuron.In the longitudinal section of the axon of the neuron (the part that carries the signal which may be covered in Schwann cells to protect the it) the action potential cycle occurs.There are four main stages: The Resting Membrane Potential, Depolarization, Repolarization, and the Refractory Period.In the Resting Membrane Potential Stage there is an active force that maintains the resting membrane potential at -70 mV. This active force is the Sodium Potassium Pump where three sodium ions leave the nerve cell and two potassium ions enter. With the Sodium Potassium Pump, it transports these ions actively and so ATP is required. In addition to the Sodium Potassium Pump, there are voltage-sensitive potassium slow leak channels that are involved with passive transport and there are also voltage sensitive sodium gates that are passive sodium channels. They are normally impermeable to sodium however it can't pass through unless there is an electrical current to open it.In the Depolarization Stage, an external stimuli occurs altering the tertiary structure of sodium gates allowing the nerve cell membrane to become more permeable to sodium than potassium. Therefore, sodium floods in passively making the extracellular fluid (ECF) more negative and the intracellular fluid (ICF). Now the voltage inside the cell is +50 mV compared to the previous stage where it was -70 mV.Once the cell has reached a voltage of +50 mV, sodium gates close and so the inflow of sodium ions into the cell are discontinued. Because of the altered concentration gradient of ions in the Depolarization Stage, it causes the potassium channels to alter their shape. As a result, there is an inflow of potassium ions outside of the cell and the inside becomes negative again. This stage is known as the Repolarization Stage. This prevents the signal from going backwards. The voltage inside the cell is now at -80 mV.In the last stage, Refractory Period, the Sodium Potassium Pump actively re-establishes the resting membrane potential. It takes time to reestablish the sodium and potassium concentrations to -70 mV.Please note that depolarization cannot occur until the resting membrane potential is reached (-70 mV).As an aside, the action potential follows the All or None Principle. This means that larger signals do not create larger action potentials. A neuron must always reach -70 mV before the signal is passed along a neuron. Therefore, the action potential will occur fully or not at all.The action potential is an electrical event occurring when a stimulus of sufficient intensity is applied to a neuron or muscle cell, allowing sodium to move into the cell and reverse the polarity.Normally neurones (neurons, or nerve cells) maintain a resting potential of -70mV across their membrane by the active pumping of 3Na+ ions out of the cell for every 2 K+ ions pumped into the cell by a Na+/K+ pump. When the neurone is stimulated, sodium ion channels open in the membrane and sodium ions flood in to the cell down an electrochemical gradient by diffusion, increasing the potential of the cell to +40mV. This is called depolarisation. At this point the sodium channels close, and potassium ion channels open. Potassium ions flood out of the cell down their electrochemical gradient, decreasing the cell's membrane potential. This is called repolarisation. There is a slight overshoot where too many potassium ions diffuse out of the cell, and there is hyperpolarisation where the cell's membrane potential falls below its normal -70mV, but this is corrected and the resting potential is once again restored. This is the sequence of events that makes up a single action potential. Action potentials are transmitted by saltatory conduction in the neurone, and impulses jump from node to node along the axon of the neurone.
What is a velocity potential?
A velocity potential is a scalar function whose gradient is equal to the velocity of the fluid at that point. If a fluid is incompressible and has zero viscosity (an ideal fluid) its velocity as a function of position can always be described by a velocity potential. For a real fluid this is not generally possible.
What happens to the membrane potential of a neuron during an action potential?
1. A neurotransmitter (NT) released from another cell (or in some cases the same cell) will diffuse across the synaptic cleft and bind to a recipient receptor. 2. The receptor will then change it's permeability to certain ions in the extracellular fluid, allowing the ions to flux into the cell (the exception here would be pharmacological agents designed to occupy the receptor without leading to a conformation change) 3. The influx of ions will alter the membrane potential. If the NT is inhibitory (e.g. GABA), then the GABA receptor that it binds to will increase its permeability to negatively charged ions (chloride) and thereby lower the local resting membrane potential (which is normally -70mV). If the NT is excitatory (e.g. glutamate) then the glutamte receptor (AMPA or NMDA) will increase its permeability to positively charged ions (sodium) which will increase the resting membrane potential from -70mV. 4. If enough NTs bind then the local membrane potentials will summate - and in the case of excitatory NTs - cause the membrane potential to change (by opening of voltage-gated ion channels) to around 0-20mV leading to an action potential 5. The action potential, which is generated in an 'all or none fashion' at the axon hillock, will then propagate all the way down the axon to the axon terminal causing the release of stored NTs (although not all NTs are stored - e.g. NOS) 6. NTs released from the presynaptic cell will then diffuse across the synaptic cleft and bind their postsynaptic receptor (normally located on a dendrite, although also located on the cell body themselves) and the whole process starts all over again
The major ingredient of the fluid inside the cells of all organisms?
Cytoplasm is the fluid inside the celols of all organisms.
Extracellular fluid is found everywhere in the body EXCEPT?
Extracellular is outside cells and intracellular is inside, so that extracellular fluid would not be inside cells.
