Sensory Physio - Introduction Flashcards
Epicritic sensations are
the mild or light sensations. Such sensations are perceived more accurately.
Examples of epicritic sensations are:
- Fine touch or tactile sensation
- Tactile localization
- Tactile discrimination
- Temperature sensation with finer range between 25°C and 40°C.
Protopathic sensations are
the crude sensations. These
sensations are primitive type of sensations.
Examples of Protopathic sensations are:
i. Pressure sensation
ii. Pain sensation
iii. Temperature sensation with a wider range, i.e. above 40°C and below 25°C
Synthetic senses are
…the sensations synthesized at cortical level, by integration of impulses of basic sensations. Two or more basic sensations are combined in some of the synthetic senses.
Best examples of synthetic senses are
vibratory sensation, stereognosis and two-point discrimination.
Mechanoreceptors function
They detect mechanical deformation (compression or stretching of the receptor or of tissues adjacent to the receptor) of the receptor.
Cutaneous corpuscular receptors may be categorized as
encapsulated and nonencapsulated receptors.
Which receptors have encapsulated endings?
Pacinian corpuscle Meissner corpuscle Ruffini ending Krause end-bulb Golgi-Mazzoni corpuscle (pressure)
Golgi-Mazzoni corpuscle is a receptor for
pressure
The expanded or encapsulated endings are not necessary for cutaneous sensation. True or false?
True. They only function as mechanoreceptors for tactile stimuli.
What are the mechanoreceptors?
(I) Merkel’s discs
(ii) Meissner’s corpuscle
(iii) Pacinian corpuscle
(iv) Ruffini corpuscle
(v) hair-follicle plexus.
Fine touch or discriminatory touch sensation is carried by
…the so-called low-threshold mechanoreceptors.
Two types of sensory afferents are associated with these mechanoreceptors
Fast-adapting (FA) and slow-adapting (SA).
Both the FA and SA afferents are further subdivided into two types, based on their receptive field properties into…
i) Type I units, with small receptive fields with well-defined borders. (ii) Type 2 units with wider receptive fields
What is the receptive field?
The area covered by the receptor
There are cold-sensitive spots and heat-sensitive spots in the skin. True or false?
True
There are __ times more cold-sensitive spots as compared to heat-sensitive spots.
4-10
Number of cold spots per cm2 of skin in lips, fingers, trunk
Lips (15-25)
Fingers (3-5)
Trunk (1)
Types of receptors for skin tactile sensibilities (epidermis and dermis)
- Free nerve endings
- Expanded tip endings
- Spray endings
- Ruffini’s endings
- Encapsulated endings
-Hair end-organs
Types of receptors with expanded tip endings
Merkel’s discs
Plus several other variants
Types of receptors with encapsulated endings
Meissner’s corpuscles
Krause’s corpuscles
Free nerve endings - Location, Modaity, Fibre Type
- Location: Everywhere in the skin
- Detects: pain, touch, pressure
- C-fibres
Meissner’s corpuscle - Location, Modaity, Fibre Type
- Location: Non-hairy part of the skin (glabrous skin), fingertips, lips
- Description: Elongated, encapsulated nv endings, excite Aβ fibres
Free nerve endings are found in…
…hairy skin, root of hair, cornea but not encapsulated endings.
Merkel’s discs - Location, Description
Location: Fingertips, hairy skin parts
Description: Expanded tip, forms Iggo dome receptor, excite Aβ fibres
Which receptor forms Iggo dome receptor?
Merkel’s discs
Hair end organ - Location
Hairy skin parts
Ruffini end organ - Location, Description, Modality
- Location: deeper layer of skin, deeper tissues, joint capsules
- Description: Encapsulated, multi branched
Meissner’s corpuscle detects…
Light touch, low frequency vibration
Merkel’s discs detect
Touch (steady state signals), Texture
Hair end organ detects…
Movement of object on the surface of the skin
Ruffini end organ detects…
…continuous state of deformation
Slow-adapting receptors examples
- Ruffini endings
- Muscle spindles and Golgi tendon
- Receptors of the macula in the vestibular apparatus
- Pain receptors
- Baroreceptors of the arterial tree
- Chemoreceptors of the carotid and aortic bodies
Fast-adapting receptors examples
Hair-end
Meissner’s corpuscle
Pacinian corpuscle
Pacinian corpuscle
- Location: Underneath the skin (dermis), facial tissues of the body
- Description: lamellated, rapidly adapting
Pacinian corpuscle detects…
Pressure, tissue vibrations
Fast pain sensation is carried by __ and slow pain sensation is carried by __ of nerve fibers.
Aδ fibers, C type
Static position sense refers to
… conscious perception of the orientation of the different parts of the body with respect to one another.
Dynamic proprioception sense refers to…
Conscious perception of the rate of movement of body parts
Proprioceptors are also stretch receptors. True or false?
True
2 types of stretch receptors associate with skeletal muscle.
Tendon receptors
Muscle spindle
Tendon receptors are found in
the muscle-tendon junction.
Tendon receptors function
- They respond to maintained tension in the muscle fascicles (or fibres) and tendon.
–They respond to rate or velocity of tension developed i.e. they respond to increasing muscle force with an increase in the firing rate.
–It is suited to monitor total force extended by the muscles
Muscle spindles function
–They determine joint angulation in mid-ranges of motion.
–They detect stretch in muscle fibres
–The detect the rate of change of length of muscle fibre
–They function to maintain muscle length.
Joint receptors are slowly adapting. True or false?
True
Joint Receptors function
They sense the degree of flexion of various skeletal joints.
How does muscle spindle function as sensory receptors?
The central region of each of the fibers has few or no actin and myosin filaments. Therefore, this central portion does not contract when the ends do. Instead, it functions as a sensory receptor
Muscle spindle receptor is excited in 2 ways:
- Lengthening the whole muscle
- Contraction of the end portions
Intensity of a stimulus
A measure of the energy content (or concentration, in the case of chemical stimuli) available to interact with the sensory receptor.
Coding is…
the conversion of receptor potentials into a pattern of action potentials that conveys relevant sensory information to the CNS
A single afferent neuron with all its receptor endings makes up a
sensory unit
Receptive field of a neuron
The portion of the body that, when stimulated, leads to activity in a particular afferent neuron
What determines the intensity of a stimulus?
Increase in receptors stimulated and frequency of impulses
What happens as the stimulus increases?
- The frequency of impulses or action potentials is also increases.
- Higher threshold receptors are recruited to increase the number of receptor stimulated
Different receptors can be excited in one of several ways to cause receptor potentials:
1) By mechanical deformation of the receptor, which stretches the receptor membrane and
opens ion channels
2) application of a chemical to the
membrane, which also opens ion channels
(3) change of the temperature of the membrane, which alters the
permeability of the membrane;
(4) by the effects of
electromagnetic radiation, such as light on a retinal visual receptor, which either directly or indirectly changes the receptor membrane characteristics and allows ions to flow through membrane channels.
The maximum amplitude of most sensory receptor potentials is
about 100 millivolts, but this level occurs only at an extremely high intensity of sensory stimulus
Which cations come in to generate RP in most sensory neurons?
Na and Ca. K and Cl go out.
Which cations come in to generate RP in rods and cones?
Others; Na closes
Which cations come in to generate RP in vestibulocochlear hair cells?
K comes in
Types of MS intrafusal fibers:
- nuclear bag muscle fibers (1-3)
* nuclear chain fibers (3-9
The primary sensory nerve ending (the 17µm) is excited by __ while the secondary ending is usually excited by ___
both the nuclear bag and the nuclear chain fibers, only nuclear chain fibers
Which of the primary and secondary nerve endings of muscle spindle carry out static and dynamic responses?
Both do static, only primary does dynamic
Regions of a receptor
(a) a transducer region
(b) a spike generator region.
Which region of a receptor is responsible for transduction?
The transducer region
Location of transducer region
At the end of the nerve terminal
The first AP of a cutaneous sensory neuron is generated at the axon hillock. True or false?
False. The first AP is generated at the first node of Ranvier
In mechanoreceptors, the Na+ channel comes under the category of
degenerins, so named because with hyperexpression of these receptor-channels, they cause degeneration of the neurons associated with them
Appearance of Krause end bulb receptors in general area
They have a mulberry-like appearance.
