Chapter 2: Heller and Schiff Flashcards
Touch
Defined as the variety of sensations evoked by stimulation of the skin by mechanical, thermal, chemical, or electrical events
Touch, for the most part, is a
Proximal sense (meaning we feel things that are close to us or actually contact us”
For a stimulus to be perceived it must actually come in contact with the _____
Skin
The skin itself is a multilayered sheet some ____ and __kg in weight
1.8m squared in area
4kg in weight (8.8lbs) on average adult
Skin is the bodies largest _____, protecting the rest of the body from _______ (due to its waterproofing), _______, and ________
Organ
Dehydration , physical injury, and ultraviolet radiation
The skin is also involved in the _______ mechanisms that regulate body temperature and blood pressure
homeostatic
Skin might be ____ or _____, ____ or ____, ____ or ____ (glabrous), ______ or ______
flat or furrowed
loose or tight
hairy or smooth (smooth = glabrous)
thick or thin
On the fingertips, ____ and ____ form intricate patterns of whorls and loops
Ridges and valley
these from in the 3rd or 4th month of fetal life
Outmost layer of the skin is called the:
Epidermis (which an be subdivided in several other layers)
The surface of the skin, the ______ is made up of dead or keratinized cell bodies from the deeper subdivisions of the epidermis that might have migrated outward as the skin renews itself from the inside out
corneum
Glabrous skin facts
- No hairs
- Overall density of end organs is greater
- Surface of glabrous skin is ridged as a result of dermal intrusions, called ‘plugs’ into the epidermis
Immediately below this protective layer of cellular ghosts is the _______, and below that is the _____
- epidermis proper,
- dermis
Dermis
A layer of nutritive and connective tissues (papalrri
Cutaneous end organs
Structures that are suspected of being responsible for transducing mechanical, thermal, chemical, or electrical energy into neural signals
-are found within the dermal layer or at the epidermal-dermal interface
Sweat glands (numbering over 2 million)
are found in the dermal layer or at the epidermal-dermal interface
In hairy skin
Hair follicles and the structures associated with them are embedded in the dermis (associated structures = fine muscle filaments(erector pilorus)
Fine muscle filaments(erector pilorus)
Reveal their presence in “hair-raising” experiences by the presence of goosebumps
Below the dermis
We find layers of connective tissue (superficial fascia) and subcutaneous fat that lie between the skin and the supportive formations of muscle and bones
A common experimental procedure involve:
Pushing on the skin - mechanically deforming it, either with infrequent pressure pulses or repetitive vibration
Viscoelastic
When the skin is touched, the energy the imposed on it at that point will be transmitted through the medium (it is “viscous”)
-Some (some is super important as it is not all) of the energy will be absorbed and stored, and is used to return the skin to its original state (skin is elastic)
As energy moves in a wave into the skin, it produces shearing forces that dissipate with distance from the source according to the ______
inverse square law
Mechanical vibration can also generate travelling _________ across the surface of the skin that may be transmitted over long distances
waves of energy
Surface waves may be reduced by placing a _______ around the moving contractor (as the waves will go very far with the vibrations)
static ring (surround)
^^^^
However, deeper waves may still tend to spread laterally
Thus the use of a surround may restrict the number of the most superficial receptors stimulated, but might not have an effect on the involvement of deeper ones
_________ will tend to spread laterally through whatever paths exist
Chemical or electrical
The electrical stimuli may find paths of least resistance through the _____ and ______ exudate in the pores of the sweat gland
Salty and electrically conductive
Any attempt to adjust the ______ above or below its normal level results in activation of local and central homeostatic mechanisms that strive to offset heat or cold
skins temperature
-therefore, changing the skin temp can influence blood pressure, peripheral nervous system
Cutaneous end organs suspected for transducing tactile stimuli in neural signals
Merkel’s disks (dermis), Ruffini cylinders, and Meissne’s Corpuscles
Merkel’s disks, Ruffini cylinders, and Meissne’s Corpuscles are found where?
Upper regions of the dermis
Pacinian corpuscles
Found in the subcutaneous connective and fatty tissues
-found primarily in glabrous skin, and do exist at much lower density in hairy skin
Single unit recording (best method available)
Used to determine which end organ produces a specific neural response to tactile stimulus
Method: A fine electrode is used to pick up the response of a single nerve fiber
Limitations: Only works to find out how a unit responds to tactile stimulation, not which end organ produces that response
A unit is classified as being ‘slowly adapting’ or having ‘a punctuate receptive field’ (small)
rather than being the response of a free nerve ending, or a ruffini cylinder
Microneurography
Relatively new method, provides the most direct measure possible through simultaneously recording a single-unit activity and human sensation
- conducted on awake humans through percutaneous (through the skin) microelectrodes instead of by dissection
- Found through this method they could electrically stimulate a single-unit nerve fiber and evoke tactile sensations that were localized to a particular region of skin
Cutaneous receptors are likely to be tightly packed in regions such as the _____,________,______
fingertips
lips
genitals
On the fingers, palms, and soles of the feet, the skin is smooth and is referred to as ________
The skin almost everywhere else on the body has hair andis simply and appropriately referred to as ____
glabrous
Hairy skin
Free nerve endings are found where?
Found throughout the body, even in body sites that devoid of any other type of colex cutaneous formation
The anatomy of the types of cutaneous end organs found in mammalian skin can be divided into two broad categories
1) Free (bare) nerve endings
2) Nerve endings either associated with or encapsulated within accessory structures
Free nerve endings
Fine sensory fibrils, which means the ends of neurons
Common encapsulated types incude:
Pacinain Merkel Meissner Ruffini Kruase and Basket endings (found around hair follicles)
The common encapsulated sensory endings range from
bare fibers, apposed to sensory cells (such as those found in merkel cell complex), to the intricately wrapped neruite found in the onion-like pacinian corpuscle
As of yet, physiological experiments _________ isolate single cutaneous end organs within the skin
Cannot !!
Defining the receptive field of “that unit”
The skin site, where , for example, mechanical stimulation evokes neural activity (opposed to say thermal stimulation) defines the field
The receptive field may be ______ ( perhaps a whole finger) or _______ (a mm or so)
Large
Punctate
The responses of the microneurography test are based on
1) Rate of adaptation
2) Size of receptive field
Units in glabrous skin sensitive to noninjurous mechanical stimuli have been classified into __ groups
Four (Large / small / fast/ slow)
The larger the fiber (A-fibers being the biggest, C-fibers being the smallest) that faster the rate of conduction
CRAZY
Two kinds of pain felt with injury
The sharp, fast component vs the dull, slow one
Homeostatis
Certain setpoints your body has (37 degrees celsius for instance for body temp)
Mechanical stimulation
Vibration and pressure (pressure pulses)
vibration vs pulse
Pulse = single pressure Vibration = has waves and a frequency
Inverse square law
Increase the distance by 2, reduce intensity by 4
Increase by 5, decrease by 25 (just square the number)
To get stimulus invariance you need
Variance
Subcutaneous =
below the skin
Classification by structure
What end organ produces a specific neural response
Due to more than one being present, for single-unit recording, they could not specifically identify
Merkel’s disks (dermis), Ruffini cylinders, and Meissne’s Corpuscles individual effects
The end organs, the presumed receptors, are scattered throughout the depth and breadth of skin, but
The density of innervation considers varies considerably, depending on the location of the body that is examined.
