Midterms: Sensory Physiology Flashcards by Lili Popp

What does each receptor sense :
Mechanoreceptors for
Thermoreceptors for
Nociceptors for

Mechanoreceptors for Mechanical Stimuli (tactile, hearing, balance, Baroreceptors)
Thermoreceptors for Temperature (Hot and Cold)
Nociceptors for Pain (free nerve endings)

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What does each receptor sense :
Electromagnetic receptors for
Chemoreceptors for

Electromagnetic receptors for Light (cones&rods)
Chemoreceptors for Chemical (pH, CO2, etc.,)

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What is DIFFERENTIAL SENSITIVITY?

Each type of receptor is highly sensitive to one type of stimulus for which itis designed. So a receptor can be unresponsive to other types of sensory stimuli.

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States that We directly perceive in the first instance the activity of our nerves, rather than properties in the external world (The CNS)

Muller’s Doctrine of Specific Nerve Energies

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What is LABELED LINE PRINCIPLE?

Every sensory modality is recognized by a specific receptor. each sensory nerve tract terminates at a specific point in the CNS, and the type of sensation felt when a nerve fiber is stimulated is determined by the point in the nervous system to which the fiber leads.

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Local potential that are being produced by your receptor

RECEPTOR POTENTIAL

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States that Increased stimulus = Increase AP frequency

Stevens power law

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If a stimulus reaches the maximum amplitude (100%), will the person experience an increase AP if more stimulus is added?

No, The person will only perceive the stimulus at 100% even if you add more what the person will perceive is 100%

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T or F
Rapidly-adapting, tonic receptors;
Slowly-adapting, phasic receptors

FALSE
Rapidly-adapting, phasic receptors;
Slowly-adapting, tonic receptors

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Mechanism of accommodation of receptor adaptation

inactivation of Na channels of nerve fibers

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At some point, the AP will gradually disappear. So that the CNS will not be bombarded with multiple sensory signals.
What mechanism is this called?

Receptor adaptation

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In duration and example,
Rapid adapting vs Slow adapting vs non adapting

Rapid = Minutes e.g. Sensation of wearing an underwear
Slow = Days or more, e.g. “normal” High blood Pressure
Non adapting = acute, eg pain

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Requirements for Receptor Adaptation

constant, non-changing stimulus
low to moderate intensity

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List the largest to smallest Sensory nerve fibers and why

Type A = Biggest (Wider Diameter; Alpha - largest myelinated neuron, fastest)

Type B = 2nd ( Myelinated )
Type C = Slowest (Unmyelinated)

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Spital Summation vs Temporal Summation

Spital = Simultaneous
Temporal = Continuous

A specific region of sensory space in which an appropriate stimulus can drive an electrical response in a sensory neuron + The smaller the receptive field, the more sensitive it is (e.g. fingertips)

Receptive feilds

most connections from input fiber to output fiber

DISCHARGE ZONE

Zone where there is less connection of input and output fibers than the discharge zone

FASCILITATED ZONE

INHIBITORY ZONE occurs when?

Transmission of signals is canceled

prolongation of signal by a neuronal pool

After discharge

Synaptic AD vs Reverberatory AD

Synaptic after discharge = long-acting NTA, neuropeptides
Reverberatory circuit = increased output pulse rate; fatigue of synaptic junction

What causes continuous output signals

caused by instrinsic neuronal excitability
caused by continuous signals from reverberating circuits
output frequency is modified by excitatory or inhibitory influence

automatic short-term adjustment of pathway sensitivity by the fatigue mechanism

synaptic fatigue

What is a neuronal pool?

A neuronal pool consists of interconnected neurons within the central nervous system that work together to perform specific functions.

Describe the concept of stimulatory field.

The stimulatory field of a neuronal pool refers to the area where input fibers synapse with output fibers, determining the functional connectivity of the neurons.

What are threshold and subthreshold stimuli?

Threshold stimuli are strong enough to generate an action potential, while subthreshold stimuli are not strong enough to do so.

Define the discharge zone within a neuronal pool.

The discharge zone includes neurons that are directly stimulated by input fibers, leading to their activation and firing of action potentials.

Explain the concept of facilitated zone.

The facilitated zone consists of neurons that receive fewer connections from input fibers compared to the discharge zone, making them more likely to be stimulated indirectly through facilitation.

What is the role of the inhibitory zone within a neuronal pool?

The inhibitory zone contains neurons that cancel or inhibit signals from the discharge zone, helping to regulate the overall activity of the neuronal pool.

Describe divergence in neuronal circuits.

Divergence refers to the spread of signals from a single source neuron to multiple neurons, amplifying the signal and allowing it to influence multiple pathways.

Explain convergence in neuronal circuits.

Convergence involves multiple source neurons converging onto a single target neuron, integrating signals from different sources.

What is a reverberatory circuit, and how does it relate to epilepsy?

A reverberatory circuit is a feedback loop within a neuronal pool that sustains activity over time. In epilepsy, continuous excitation within such circuits can lead to seizures.

What is synaptic fatigue, and how does it affect neural processing?

Synaptic fatigue is the temporary decrease in synaptic transmission efficiency due to prolonged activity. It can lead to short-term adjustments in pathway sensitivity and may contribute to cognitive fatigue.

What are inhibitory circuits, and how do they regulate neural activity?

Inhibitory circuits involve feedback loops that inhibit excitatory neurons, helping to regulate the overall activity level within a neuronal pathway or pool.