Question # 5: What does the all-or-none law mean and how does it relate to volta

Question

Question # 5: What does the all-or-none law mean and how does it relate to voltage gated channels?

Question # 6: What is the difference between a relative refractory period and an absolute refractory period?

Question # 7: What does it mean when we say an action potential propagates down an axon and how does this relate to the nodes of Ranvier?

Question # 8: What is a firing rate and how does it relate to neurotransmission?

Question # 9: Where are neurotransmitters stored and how are they released?

Question # 10: Explain the 3 ways in which neurotransmitters are cleared from the synapse?

Question # 3: What is the difference between an electrostatic attraction and a concentration gradient?

Explanation / Answer

What does the all-or-none law mean and how does it relate to voltage gated channels?

All or None law states that action potential occurs when a neuron is sufficiently stimulated beyond the threshold. But the stimulus is below the threshold the action potential does not occur at all.

Voltage gated channels on the trigger zone and axon always begin with the depolarization which is based on the principle of All or None. It either does not occur at all or exhibits the same peak voltage regardless of stimulus strength.

What is the difference between a relative refractory period and an absolute refractory period?

Absolute refractory period is the period after Action potential in which neuron cannot generate another action potential because Sodium channels are inactive where time gated channels close which do not allow Sodium ions to enter the cell

Relative Refractory period occurs when neurons are hyperpolarized. The neurons has Potassium channels opened allowing Potassium ions to leak from the cell. Neurons can generate another action potential in relative refractory period if stimulus is high

What does it mean when we say an action potential propagates down an axon and how does this relate to the nodes of Ranvier?

After the initiation of action potential at the axon hillock, the action potential travels down along the axon towards the axon terminus. The action potential is irreversible, completed once it begins, it is self propagating, non decremental,and the signal maintains the same strength regardless of distance.

In non myleinated nerve fibers action potential conduction is a chain reaction of potentials and propagates continuously like electrical current. In myelinated fibers saltatory conduction occures where Sodium ions at Nodes of ranvier generates action potential due to which positive charge flows rapidly along axon and depolarizes membrane. The signal grows weaker with distance, depolarization of membrane at next Node of Ranvier opens Sodium channels triggering new action potential

What is a firing rate and how does it relate to neurotransmission?

Increasing firing rate of a neuron results in the quantity of neurotransmitters released and relays high stimulus strength to the postsynaptic neuron. Excitatory Post synaptic Potentials increase the number of action potentials above the spontaneous firing rate whereas the Inhibitory post synaptic potentials decrease the number of action potentials below the spontaneous firing rate.

Where are neurotransmitters stored and how are they released?

A neurotransmitter is a molecule which transmits signals from the presynaptic neuron to the post synaptic neuron across a synapse. The neurotransmitters are stores and released from the synaptic vesicles. When an action potential is arrived at the presynaptic neuron, it triggers the release of Calcium ions by which the synaptic vesicles fuse with the presynaptic membrane causing the release of neurotransmitter

Explain the 3 ways in which neurotransmitters are cleared from the synapse?

Neurotransmitters are cleared from the synapse by:

1. Enzymatic degradation which is an active process in which special enzymes in the synapse destroy the neurotransmitters (For example Acetylcholinesterase cleaves Acetylcholine, Monoamino oxidases and Catechol Ortho Methyl transferases cleave Noradrenaline, Adrenaline etc)

2. Active Neuronal Reuptake in which the nerve terminal absorbs the neurotransmitter and recycles it for another cycle

3. Diffusion where the neurotransmitters slowly move out of the synapse by passive transport using the concentration gradient

What is the difference between an electrostatic attraction and a concentration gradient?

Concentration gradient results in the movement of particles in random motion to move from high concentration to low concentration

Electrostatic attraction refers to the tendency of attraction of oppositely charged substances. Concentration gradient, Electrostatic pressure, Permeability of the membrane to ions and active ion transport helps in establishing the resting membrane potential

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects