Quantitative Cell Physiology - Exam 2

How are ion channels related to cell membrane polarization?

The opening and closing of ion channels change membrane permeability and, therefore, ion influx and efflux. This net movement of ions impacts the cell’s polarization.

How is a graded potential different from an action potential?

A graded potential has variable strength and is better for short distance communication. An action potential is all or nothing (either it happens or not) and is the same strength every time. It is better for long distance signals.

What happens after an action potential? What are these time periods called? How do they control the direction of the action potential?

After an action potential, there is an absolute refractory period (none of the Na+ channels are reset, another AP CANNOT occur) and a relative refractory period (some Na+ channels are reset, AP can occur with larger than normal signal). These prevent the AP from traveling backwards (because previous area/neurons are inactive).

How do neurons connect? Be able to draw this

The axon terminal of the pre-synaptic neuron connects to the dentrite of the post-synaptic neuron. The synaptic cleft is a small open space between them.

How do we quantify neuronal speed? What specific properties of neurons impact the speed of the action potential?

Conduction velocity is the measure of neuronal speed. The “cable properties” govern this speed through the length constant and time constant. Physical change that impacts these can be thicker axon, myelin sheath, gaps in myelin sheath. (Know how each of these impact membrane resistance, cytoplasmic resistance, etc.)

What is the definition of a neurotransmitter?

Chemicals synthesized and released by the presynaptic cell. In order to be a NT, the molecule must create the same response when exogeneously given (i.e., as a drug).

How do neuronal cell membrane features contribute to its function?

Can the same neurotransmitter be inhibitory and excitatory? How?

Yes, it depends on what type of receptor receives the NT. Different receptors can accept the same NT but have different outcomes.

Where are neurotransmitters synthesized? How are they moved within the cell?

Neurotransmitters are synthesized in different locations depending on size: large ones are made in the cell body, while smaller ones are synthesized at the axon terminal. Large NT are moved to the axon terminal by fast axonal transport, while the enzymes needed for the smaller NT are moved using slow axonal transport.

How is the Central Nervous System compartmentalized for function?

CNS is mainly the integrator of information gathered by the Peripheral NS.

How does a cell distinguish between different types of energy (like a photon vs a pressure wave)?

Cells have specific receptors that can only be activated by one type of stimulus (i.e., vertical pressure). If those receptors are activated, the cell knows what the specific stimulus was to cause that.

What is the common mechanism in sensory transduction?

Usually, the cell receptors convert the physical stimulus into an electrochemical signal, mediated by the opening/closing of ion channels.

How is the intensity of a stimulus encoded?

The intensity of a stimulus can be determined by how many receptors are activated and the frequency by which they are activated.

What is the difference in tonic vs phasic signal generation?

Tonic receptors adapt slowly, while phasic receptors adapt quickly.

How does the lens of the eye modulate incoming light?

The lens of the eye focuses the light that enters into one focal point that reaches the retina.

How is the amplitude of sound calculated?

What are the types of primary sensory neurons (as opposed to specialized epithelial cells)?

Are some sensory receptors constitutively active? Which ones?

At the cellular level, what are some similarities between hearing and balance?

What do nociceptors do?

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Are temperature and pain detected by primary sensory neurons?