1/17 Britton Somatosensory Neurotransmission: Touch, Pain, and Temperature Flashcards by Aditi Iyer

Sensory Receptors-Basic Function

1) sensory receptors are _______
2) sensory receptors covert stimuli in the environment (touch, temp, pressure) into _____ _____ in sensory neurons
3) the conversion process is called _____ ______

transducers
action potentials
sensory transduction

How well did you know this?

Not at all

Perfectly

______ like muscle spindles and golgi tendon organs relay info about muscle length and tension

Proprioceptors

How well did you know this?

Not at all

Perfectly

Rods and cones in the retina that respond to light

Photoreceptors

How well did you know this?

Not at all

Perfectly

_______are stimulated by chemicals in the environment (taste, smell) as well as internal chemical in plasma

Chemoreceptors

How well did you know this?

Not at all

Perfectly

______ are cutaneous receptors for touch and pressure

Mechanoreceptors

How well did you know this?

Not at all

Perfectly

________- detect the sensations of warm and cold

Thermoreceptors

How well did you know this?

Not at all

Perfectly

________-mediate potentially harmful stimuli such as pain, extreme heat, and extreme cold

Nociceptors

How well did you know this?

Not at all

Perfectly

Each of the principal types of sensation that we can experience-pain, touch, sight, sound, is called _______ of sensation

Modality

How well did you know this?

Not at all

Perfectly

The nature of the sensory receptor varies between:

Sensory modalities

How well did you know this?

Not at all

Perfectly

the sensory receptor may be a _____ ______ at the end of a peripheral nerve

Specialized structure

How well did you know this?

Not at all

Perfectly

many sensory receptors are ______ _____ cells

Specialized epithelial cells (touch, vision, taste, hearing)

Not smell

How well did you know this?

Not at all

Perfectly

if the sensory receptor is a specialized structure where will it synapse?

On a 1st order neuron

How well did you know this?

Not at all

Perfectly

the sensory receptor may be ____ _____ endings of 1st order neurons

free nerve endings (touch, temp, pain, smell)

How well did you know this?

Not at all

Perfectly

When the receptor is also the 1st order neuron where does it synapse?

There is no need for a synapse

How well did you know this?

Not at all

Perfectly

Sensory receptors on the skin are:

Cutaneous receptors that mediate the sensations of touch, pressure, pain, temperature

How well did you know this?

Not at all

Perfectly

Sensory receptors on the skin: associated sensory nerves are classified as _____ fibers according to ______

A-beta, A-Delta, and C fibers; diameter and degree of myelination

How well did you know this?

Not at all

Perfectly

What are the 3 sensory receptors associated with the skin?

Mechanoreceptors, Thermoreceptors, and Nociceptors

How well did you know this?

Not at all

Perfectly

What types of sensory receptors are associated with mechanoreceptors and what is their associated afferent type?

Most are A-beta; only outlier is free nerve endings, which are A-delta and C fibers

How well did you know this?

Not at all

Perfectly

what type of sensory receptors are associated with thermoreceptors and what is their associated afferent type?

Warm receptors - C fibers
Cold receptors - A-delta

How well did you know this?

Not at all

Perfectly

Warm receptors (thermoreceptors) are _______

Free nerve endings

How well did you know this?

Not at all

Perfectly

What type of sensory receptors are associated with nociceptors and what is their associated afferent type?

A-delta, except polymodal (free nerve endings) are C fibers

How well did you know this?

Not at all

Perfectly

Classification of Neuron Fibers

Structural Classification: (3 different types of neurons)

unipolar
bipolar
multipolar

How well did you know this?

Not at all

Perfectly

Classification of Neuron Fibers

Functional

sensory
interneuron
motor neuron

How well did you know this?

Not at all

Perfectly

Classification of Neuron Fibers

Direction from CNS

afferent
efferent

How well did you know this?

Not at all

Perfectly

# Classification of Neuron Fibers Chemical

- adrenergic - cholinergic - GABAergic

# Classification of Neuron Fibers Diameter and myelination

Speed of conduction (A, B, and C fibers)

_____ can be classified according to their conduction velocity

Nerve fibers

What type of nerve fiber is the fastest and has the largest diameter?

A-alpha fibers

A-alpha fibers are _____ neurons

Motor

Which type of nerve fiber is the slowest?

Type C (slow pain) Postganglionic autonomic nerves, olfaction

_____ fibers are unmyelinated

Type C

What results in faster conduction velocites?

larger size (diameter) and myelination

Sensory afferent nerve fibers are _______ in many aspects. What nerve fibers are associated?

Heterogenous A-Beta A-Delta C fibers

What type of nerve fibers have a medium conduction velocity and a medium diameter?

- A-beta (touch and pressure) - A-Gamma (motor neurons to muscle spindles)

What type of nerve fibers have a small diameter and a medium conduction velocity?

- A-delta; touch, pressure, temp, fast pain - B-preganglionic autonomic nerves

Sensory mechanoreceptors sense:

Touch and pressure

Name the sensory mechanoreceptors on the skin

Free nerve endings Merkel discs Pacinian corpuscle Meissner's corpuscle Hair-end organ Ruffini endings

_____ _____ is the critical first step in all sensory processing

Sensory transduction

What activates a sensory receptor?

Environmental stimuli such as pressure or temperature, which gets converted into a neuronal AP

The transduction process couples ______ detection (activation of a receptor) to the opening or closing of _____ channels in the receptor membrane. This leads to:

Stimulus; ion channels; current flow across the membrane (changes membrane potential)

Current flow across the membrane will result in:

A change in membrane potential

A change in membrane potential in a sensory receptor will cause a _____ ______, which will increase or decrease the likelihood that neuronal APs will occur

Receptor potential

Another name for receptor potential

Generator potential

the _______ is the non-propagated depolarizing potential recorded in a sensory receptor after an adequate stimulus is applied

Receptor potential

The _______ is the non-propagated depolarizing potential recorded in a sensory receptor after an adequate stimulus is applied

Receptor potential

What makes the receptor potential a graded response?

The magnitude of the receptor potential is proportional to the strength of the stimulus

True or false: the receptor potential is a graded response, which is different from the all or nothing neuronal AP

True - as the stimulus increases, the magnitude of the receptor potential also increases

When a receptor potential reaches a critical ______ in stimulus strength, an AP is generated in the sensory nerve

Threshold

The strength of a stimulus is then conveyed in the sensory nerve by the ______ of AP

Frequency

what is it called when a receptor stimulus is converted to a recognizable sensation

Sensory coding

The quality and strength of a sensory stimulus is determined by?

Properties of the sensory receptors

What are the 4 attributes of stimuli that all sensory systems encode?

- modality - intensity - duration - location (receptive field)

Modality

Mode of stimuli that can be sensed by the receptor

What are examples of mechanical modalities?

Touch, pressure, vibration

What are examples of chemical modalties?

- Bradykinin - Prostaglandin - pH - histamine

What are the temperature modalities?

Hot and cold

What is the intensity of a stimulus coded by? (2 things)

- the # of receptors activated - the frequency of APS (stronger stimuli produce a HIGHER frequency of APs)

What is population coding?

The number of receptors activated

What is frequency coding?

Frequency of APs

Sensory Coding: Duration 1. ________ is a decrease in the size of the receptor potential with a constant stimulus 2. _____ ______ receptors keep stimulating APs as long as the stimulus is present 3. _____ ______ receptors respond maximally but briefly when a stimulus is presented; their response ______ if the stimulus is maintained

1. Adaptation 2. Slowly Adapting Receptors 3. Rapidly Adapting Receptors; decreases

Examples of slowly adapting receptors

Merkel disc, Ruffini corpuscle (detect sustained pressure)

Examples of rapidly adapting receptors

Meissner's and Pacinian corpuscle (can detect next pressure quickly applied)

The ______ ______ of a sensory neuron is the region of the skin within which a tactile stimulus evokes a sensory response in its axon

Receptive field

The accuracy by which tactile stimuli can be sensed varies in different regions of the body is called:

Mechanosensory discrimination

How big is the receptive field of mechanosensory neurons on the fingertips?

1-2mm

How big is the receptive field on the palms?

5-10 mm

How can the variation of receptive fields be measured?

Two point discrimination test

Two Point Discrimination Test 1) a technique that measures the _______ inter-stimulus distance required to perceive 2 simultaneously applied stimuli as ______ 2) measures the ______ distance on the skin between neighboring receptive fields for touch

1) minimal, distinct 2) minimum

Smaller discrimination point means:

Smaller receptive field

Mechanosensory discrimination is due to:

- density of mechanoreceptors - size of receptive fields

Mechanoreceptors in the fingertips are 3-4x _______ and ______ than in other areas of the hand

More numerous and dense

Mechanoreceptor: Free Nerve Ending Name the associated afferent nerve type, location, adaptation, and modality

- A-delta, C - Superficial, all skin - Modality: light touch - Adaptation: slow

Mechanoreceptor: Merkel's Disk Name the associated afferent nerve type, location, adaptation, and modality

- A-beta - Superficial, all skin - Adaptation: slow - Modality: pressure

Mechanoreceptor: Pacinian Corpuscle Name the associated afferent nerve type, location, adaptation, and modality

- A-beta - Deep, all skin - Adaptation: Rapid - Modality: vibration

Mechanoreceptor: Meissner's Corpuscle Name the associated afferent nerve type, location, adaptation, and modality

- A-beta - Superficial, Glabrous Skin - Adaptation: rapid - Modality: vibration

Mechanoreceptor: Hair Follicle Receptor Name the associated afferent nerve type, location, adaptation, and modality

- A-beta - Superficial, hairy skin - Adaptation: slow - Modality: bending of hair

Mechanoreceptor: Ruffini's ending Name the associated afferent nerve type, location, adaptation, and modality

- A-beta - Deep, hairy skin - Adaptation: slow - Modality: pressure

_____ _______ gives us the ability to differentiate information through the sense of touch

Tactile discrimination

Thermoreceptors examples

- Warm receptors (free nerve endings) - Cold receptors

Nociceptors examples

Mechanical, Thermal, Polymodal (all free nerve endings)

Nociceptors and thermoreceptors are relatively ___________ on _______ or _______ in hairy or glabrous skin and deep tissues

unspecialized; unmyelinated C fibers; myelinated A-delta fibers

Like mechanoreceptors, _______ transduce a variety of stimuli into _____ potentials

nociceptors receptor (stimuli can be tissue damage from a cut, strong mechanical pressure, extreme heat, etc.)

nociceptors are often referred to as ______ _____ fibers

Polymodal nerve fibers (different modes of pain detected)

Nociceptors detect ______ stimuli

Noxious (harmful, injurious)

1) nociceptors express a wide variety of _____ channels that transduce the ______ potential into a ______ 2) the resulting _____ potential (depolarization) triggers the activation of _____ channels which will generate a _______ neuronal AP

1) ion, receptor, neuronal AP 2) receptor, ion, propagating

Sensory Transduction at Nociceptors: the transduction process couples _______ to _______ in the receptor membrane

stimulus detection (activation of a receptor) to the opening or closing of ion channels

Sensory transduction involves a complex of molecular ________ present on distinct subsets of nerve fibers

Transducers (ion channels)

Ion channels involved in transduction

- Acid sensing channels (ASIC) - Purinergic Ion channels - Piezo mechanosensitive channels - ANO1 (Ca2+-gated chloride channels) - Transient Receptor Potential channels (TRP)

Acid sensing ion channels (ASIC) activated by:

Protons (H+)

Purinergic ion channels activated by:

ATP

Piezo mechanosensitive channels activated by:

Mechanical sensation

Activation of nociceptors leads to current flow across the membrane, generates a ______ potential, which will result in neuronal APs

Receptor potential

Transient Receptor Potential Channels (TRP) 1. these are a ______ of ion channels 2. TRP channels that open in response to stimuli result in _______ and the generation of _____ potentials 3. TRP channels are found on _____ _____ _____ of polymodal neurons (temp and pain sensing)

1. superfamily 2. depolarization, receptor 3. free nerve endings

TRP-V (TRP-vanilloid) - what modalities does this channel respond to? What is this channel stimulated by?

- responds to heat and pain - stimulated by capsaicin, the spice in chili peppers

TRP Channels: Heat, Cold and Pain Transducers TRP-M (TRP-melastatin) is stimulated by?

Stimulated by cold and menthol

TRP channels are localized to:

Trigeminal, vagal, and dorsal root ganglia

TRP channels transduce what stimuli into _____ fluxes?

- Visual, chemical, thermal, mechanical, painful, and osmotic stimuli - Ca2+ fluxes

Examples of TRP channels

- TRP-V - TRP-M - TRP-A

TRP Channels: Heat, Cold and Pain Transducers TRP-A (TRP-ankyrin repeat) What modality does this channel respond to? what is this a transducer for?

responds to heat transducer for pungent chemicals

______ blocks TRPV1 which is a major component of ______

Cetylpyridinium chloride; Scope mouthwash

The discovery of TRPV1 in sensory neurons The majority of transducers belong to the thermo-sensitive _____ family of ion channels

TRP family of ion channels

What are the 3 types of pain that are generally distingushed?

Nociceptive, inflammatory, neuropathic

Inflammatory pain is associated with ______ caused by tissue inflammatory conditions, which can lead to:

damage; chronic pain syndromes

Neuropathic pain 1) a ______ pain state, characterized by _____ and or _____ nerve injury 2) can lead to? 3) tends to be refractory to:

1) chronic, peripheral and/ or central nerve 2) chronic pain syndromes characterized by hyperalgesia, allodynia, fibromyalgia 3) pharmacological treatment

Types of nociceptive pain

Fast and slow

Fast pain (sharp, pricking) - ____ localized and transmitted by _____ fibers

Well; A-delta

Slow pain (dull, aching) - _____ localized, transmitted by ______

Poorly; C fibers

Inflammatory mediators induce pain by activating ______

Nociceptors

Examples of neuropathic pain

traumatic nerve injury diabetic neuropathy chemotherapy induced peripheral neuropathy (CIPN)

What is an 'inflammatory soup'

describes the mixture of substances released from damaged tissue, immune cells, and bacteria

Nociceptor activation and transduction is triggered through a wide variety of ____ channels what are some of the ion channels that get activated?

Ion; GPCR's, RTK's, ligand gated ion channels. other channels and pores

Nociceptors arise from cell bodies in the _______ that send ____ axonal process to the periphery and the other into the _______

DRG or trigeminal ganglion; 1; spinal cord or brainstem

The nociceptive signal is transmitted to the _____ synapse in the spinal _____ horn by releasing a variety of neurotransmitters at the synapse, such as:

- Central - Dorsal - Substance P, Glutamate, Calcitonin, Calcitonin gene related peptide (CGRP)

1) Dental pulp contains: 2) What types of fibers are present?

1) abundant sensory fibers of TG neurons 2) A-delta and C fibers

The nociceptive signal is conducted through either _____ or _____ to the _______ of the ______

- myelinated A-delta fibers - unmyelinated C fibers - lamina I and II of the dorsal horn in the spinal cord

Characteristics of A-delta fibers in DENTAL PAIN Myelination:? Location of terminals:? Pain Characteristics: ?

- Yes - Principally in region of pulp-dentin junction - Sharp, pricking

characteristics of C- fibers in DENTAL PAIN Myelination:? Location of terminals:? Pain Characteristics: ?

- No - Distributed throughout pulp - Burning, aching, less bearable than A-delta fiber sensations

Sensory Pathways Steps Involved in Transmitting Sensory Info 1) information transmitted from _____ receptors to the _____ cortex via a series of neurons 2) order of sensory afferent neurons 3) synapses are made in _____ ______

1) peripheral, cerebral 2) 1st, 2nd, 3rd, 4th order sensory afferent neurons 3) relay nuclei

Relay Nuclei 1) often ______ pathways, where 2 or more neurons synapse with the 1 neuron 2) ______ may also be located in the relay nuclei 3) the relay nuclei process the info they receive via _______ which may be excitatory or inhibitory? (give examples)

1) converging 2) interneurons 3) interneurons Excitatory: ACh Inhibitory: GABA and Glycine

Sensory Pathways 1) _______ are closest to the sensory receptor 2) cell bodies are located in a ______ or _______ ganglion

1) 1st order or primary sensory neurons 2) DRG or cranial nerve ganglion EXCEPT: auditory, olfactory, and visual systems

In some cases, the 1st order neuron is also the receptor cell, termed-

Free nerve endings

2nd order neurons 1) axons of the 2nd order neurons (descend/ascend) from the spinal cord to the next relay located in the ______ 2) en route, the axons of 2nd order neurons ______ _____ _____ (decussation) either in the spinal cord or in the brain stem

1) ascend, thalamus 2) cross the midline-decussation

3rd Order Neurons are typically located in the ______

Thalamus

4th Order Neurons reside in the _____ area of the ______ cortex

Sensory area of the cerebral cortex

What is the sensory nerve that innervates the orofacial region?

trigeminal nerve (CN V)

______ stimuli in teeth are transmitted in primary ______ neurons (1st order neurons) located in the trigeminal ganglion via ______ order neurons in the brain stem to the brain

noxious, afferent, 2nd

What are the 2 major ascending somatosensory pathways?

- Dorsal Column-Medial Lemniscal (DCML) - Lateral Spinothalamic Tract (LST)

What sensory information is relayed in the DCML pathway

Mechanoreceptors, proprioceptors

What sensory information is relayed in the LST pathway

Thermoreceptors, nociceptors

Somatosensory sensations from all areas of the body go to the _____ cortex

Sensory

______ ______ is a neurological 'map' of the portions of the cortex dedicated to processing sensory information from different regions of the body

Sensory homunculus

1/17 Britton Somatosensory Neurotransmission: Touch, Pain, and Temperature Flashcards

(131 cards)