Pain and Itch Mechanisms

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Questions and Answers

What type of receptors respond specifically to chemical ligands?

Photoreceptors

Thermoreceptors

Mechanoreceptors

Chemoreceptors (correct)

Which sensory receptor responds to temperature changes?

Photoreceptors

Rheoreceptors

Thermoreceptors (correct)

Mechanoreceptors

Which of the following receptors is involved in the sense of hearing?

Thermoreceptors

Mechanoreceptors (correct)

Chemoreceptors

Nociceptors

What structure is typically involved in the transmission of sensory information for specialized receptors?

Myelinated axons Signup and view all the answers

Which type of sensory neuron receptive field is found in more sensitive areas of the body?

Small receptive fields Signup and view all the answers

What is the role of synaptic vesicles in sensory receptors?

Releasing neurotransmitters Signup and view all the answers

What kind of nerve endings are associated with pain and itch sensations?

Free nerve endings Signup and view all the answers

For visual stimuli, which receptors are activated?

Photoreceptors Signup and view all the answers

The convergence of sensory neurons results in what type of receptive fields?

Large receptive fields Signup and view all the answers

What type of receptors senses steady pressure and texture?

Merkel receptors Signup and view all the answers

Which sensory receptor is primarily responsible for sensing vibrations?

Pacinian corpuscle Signup and view all the answers

What happens to the area of the brain that represents a lost finger?

Adjacent areas take over its function Signup and view all the answers

What type of sensory information do free nerve endings of nociceptors primarily respond to?

Noxious stimuli Signup and view all the answers

What is the function of Meissner's corpuscles?

Responding to flutter and stroking movements Signup and view all the answers

Which part of the body does the thalamus relay sensory signals from?

Left side Signup and view all the answers

What determines the duration of a series of action potentials in response to a stimulus?

The duration of the stimulus Signup and view all the answers

Which type of receptors are primarily associated with continuous monitoring of bodily parameters?

Tonic receptors Signup and view all the answers

What is the function of receptor adaptation?

To ignore irrelevant stimuli for homeostasis Signup and view all the answers

Which of the following is NOT considered a modality of somatic senses?

Sound perception Signup and view all the answers

What type of stimulus would a baroreceptor respond to?

Pressure changes Signup and view all the answers

Which of the following stimuli would likely lead to receptor adaptation?

Consistent low-level noise Signup and view all the answers

Which sense is mainly associated with nociception?

Pain Signup and view all the answers

How does the body typically respond to stimuli that threaten homeostasis?

Focusing attention on them Signup and view all the answers

What would be a likely characteristic of a phasic receptor?

Rapidly adapting to changing stimuli Signup and view all the answers

Which of the following modalities would you associate with proprioception?

Determining body position Signup and view all the answers

What leads to the formation of a secondary receptive field?

Convergence of multiple primary sensory neurons Signup and view all the answers

What happens when fewer neurons converge in sensory pathways?

The secondary receptive fields become smaller Signup and view all the answers

How are simultaneous subthreshold stimuli processed?

They sum to initiate an action potential Signup and view all the answers

Why do two stimuli within the same secondary receptive field appear as a single point?

Only one signal is transmitted to the brain Signup and view all the answers

What is the result of two-point discrimination on the skin surface?

The brain perceives distinct stimuli accurately Signup and view all the answers

What occurs when two points fall outside the overlapping secondary receptive fields?

They are recognized as distinct stimuli Signup and view all the answers

How does convergence affect the perception of stimuli?

It results in the fusion of multiple sensory inputs Signup and view all the answers

What is the implication of having smaller secondary receptive fields?

Greater ability to discriminate between two distinct points Signup and view all the answers

What role do secondary sensory neurons play in the perception of stimuli?

They gather and integrate signals from multiple primary neurons Signup and view all the answers

What does the term 'two-point discrimination' refer to?

The capacity to identify two separate stimuli as distinct Signup and view all the answers

What phenomenon enhances the perception of a stimulus?

Inhibition of lateral neurons Signup and view all the answers

Which of the following describes how stimulus intensity is coded?

By the number of receptors activated and frequency of action potentials Signup and view all the answers

What is the main function of tonic receptors?

To maintain a constant response to a persistent stimulus Signup and view all the answers

How is the duration of a stimulus coded?

By the duration of action potentials Signup and view all the answers

What happens to some receptors during prolonged exposure to a stimulus?

They adapt and cease to respond Signup and view all the answers

What occurs when the strength of a stimulus increases?

Frequency of action potentials is directly proportional to stimulus strength Signup and view all the answers

Which term describes receptors that respond strongly to changes in stimulus intensity?

Phasic receptors Signup and view all the answers

What does the term 'frequency coding' refer to in the context of sensory systems?

The frequency of action potentials generated Signup and view all the answers

What role do lateral neurons play in perception?

They enhance the perception of a stimulus Signup and view all the answers

Which aspect of action potentials is less affected when comparing tonic and phasic receptors?

Duration of action potentials Signup and view all the answers

Study Notes

Sensory Receptors Overview

Types of Sensory Receptors: Include chemoreceptors (taste, smell), mechanoreceptors (pressure, sound, hearing), thermoreceptors (temperature), and photoreceptors (vision).
Free Nerve Endings: Unmyelinated axons responsible for detecting pain and itch sensations.
Receptor Types: Specialized cells, such as hair cells in the ear, release neurotransmitters to sensory neurons, generating action potentials.

Receptive Fields

Convergence Effect: Multiple primary sensory neurons can converge, resulting in larger receptive fields for less sensitive areas, leading to a reduced ability to discriminate between two stimuli (two-point discrimination).
Secondary Receptive Fields: Smaller fields are formed with fewer converging neurons, allowing for better discrimination of stimuli.

Properties of Stimulus

Intensity Coding: Determined by the number of activated receptors and the frequency of action potentials (frequency coding).
Duration Coding: Implied by the duration of action potentials; receptors can adapt and cease responding to sustained stimuli.
Tonic vs. Phasic Receptors: Tonic receptors continuously monitor certain parameters (e.g., blood pressure), while phasic receptors respond only briefly to changes in stimuli.

Action Potentials and Receptor Adaptation

Action Potential Response: The frequency of action potentials correlates with the intensity of the stimulus; duration varies with the pattern of action potentials at the axon terminal.
Receptor Adaptation: Allows the body to ignore non-threatening stimuli, such as persistent smells.

Somatic Senses

Modalities of Somatic Senses: Include touch, proprioception, temperature, and nociception (pain and itch).
Sensitivity Mapping: The area of the sensory cortex dedicated to body parts corresponds to their sensitivity; higher sensitivity is observed in areas like the fingertips.

Sensory Receptors in the Skin

Merkel Cells: Detect steady pressure and texture.
Meissner's Corpuscles: Respond to flutter and stroking movements.
Pacinian Corpuscles: Sense vibration.
Hair Follicle Receptors: Free nerve endings can detect hair movement and noxious stimuli.

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Description

Explore the intricate mechanisms behind pain and itch through the study of free nerve endings and the role of unmyelinated axons. This quiz delves into sensory receptors and their functions, shedding light on how our bodies perceive these sensations.