L22+23 Bioelectricity: Action Potentials and Synapses in Neurons

Question 1 of 13

1

The timing and sequence of events leading up to and when carrying out an action potential in a neuron are critical.
Firstly, ❌ gated ❌ channels open, and begin to ❌ the cell. If the threshold potential of ❌ is reached, the ❌ gated Na+ channels open and the cell begins to rapidly depolarise (an ❌ function) as Na+ ❌ the cell. When the membrane potential reaches +30mV it is at it's maximum, and this is is the ❌ which causes propagation along the axon without losing amplitude. At +30mV, the Na+ channels ❌ and the ❌ open. ❌ rapidly leaves the cell, and ❌ occurs. ❌ beyond the RMP usually occurs.
The cell is returned to RMP by pumping the ions against their gradient, which is done by Na+/K+ ATPase.

Drag and drop to complete the text.

stimulus

Na+

depolarise

-59mV

voltage

excitatory

enters

exits

action potential

close

voltage gated K+ channels

K+

repolarisation

Hyperpolarisation

Explanation

Question 2 of 13

1

The refractory period is one mechanism that determines the direction of propagation of an action potential. Choose the correct statements about refractory periods.

Select one or more of the following:

There are two refractory periods.
The initial refractory period is the absolute refractory period.
The relative refractory period follows the absolute refractory period.
The relative refractory period is the shortest of the periods (in ms)
There is no response during the absolute period
The relative period requires a large stimulus
The absolute period is measured from the opening of voltage gated Na+ channels to the action potential
The relative period is measured from the action potential to the hyperpolarisation of the cell
The refractory period is an intrinsic feature of the Na+ channels

Explanation

Question 3 of 13

1

The mechanism of the refractory period:

Select one or more of the following:

depends on the inactive state of K+ channels after activation
relies on the fact that inactive channels do not respond to the electric field
prevents backward movement
relies on an inactive but open state

Explanation

Question 4 of 13

1

The action potential 'leaping' over the Nodes of Ranvier as it propagates is saltatory conduction.

Select one of the following:

True
False

Explanation

Question 5 of 13

1

Choose the incorrect statement about electrical synapses.

Select one of the following:

They are linked by gap junctions.
There is a direct connection between neurons.
Charge needs to be 'stored' at the terminus of the presynaptic neuron.
It is the fastest method of synapsing.

Explanation

Question 6 of 13

1

Choose the incorrect statement about chemical synapses.

Select one of the following:

There is no physical link between the two neurons.
The propagation of the action potential is direct.
A chemical messenger/neurotransmitter has to be 'stored' in the synaptic knob of the presynaptic neuron.
It is slower than electrical synapses.
The NMJ is an example of a specific chemical synapse.

Explanation

Question 7 of 13

1

Choose the correct statements about the structure of pre- and post- synaptic neurons.

Select one or more of the following:

Stimulus gated Na+ channels are most critical and most concentrated at the input zones of neurons.
Stimulus gated Ca+ channels at the presynaptic knob allow vesicle release.
Vesicles containing neurotransmitter reside in the postsynaptic knob.
Mitochondria are present at the synapse.

Explanation

Question 8 of 13

1

Without a higher concentration of calcium in the ECF compared to the ICF, you cannot trigger the release of vesicles in a synapse.

Select one of the following:

True
False

Explanation

Question 9 of 13

1

Stimulus gated channels also act as receptors.

Select one of the following:

True
False

Explanation

Question 10 of 13

1

If stimulus gated channels are Cl- or K+, hyperpolarisation occurs and this is inhibitory.

Select one of the following:

True
False

Explanation

Question 11 of 13

1

Which of these is not a method of closing/switching off a synapse?

Select one of the following:

Degradation by enzymes
Reuptake of neurotransmitter into the knob
Diffusion/reuptake of neurotransmitter into glia cells
Mitochondrial uptake of neurotransmitter

Explanation

Question 12 of 13

1

Choose the correct statement. EPSP is:

Select one of the following:

Excitatory Post Synaptic Potential (Net depolarisation)
Excitatory Pre Synaptic Potential (Net hyperpolarisation)
Electric Post Synaptic Potential (Net depolarisation)
Electric Post Synaptic Potential (Net hyperpolarisation)

Explanation

Question 13 of 13

1

IPSP stands for Inhibitory Post Synaptic Potential, and is a net depolarisation due to K+ or Cl- channels.

Select one of the following:

True
False

	Created by Mer Scott over 7 years ago