Chapter 12 somatosensation exam Flashcards
Somatic sensation is divided into what categories?
Touch, pain. temperature, and body position
What are sensory receptor responsible for?
encode intensity, duration, position, and sometimes direction
What are the two major types of skin?
Hairy and glabrous (hairless) such as the backs and palms of the hand, lips, and soul of the feet.
What is the function of skin?
The outer layer of the skin is called the epidermis and the inner layer of the skin is called the dermis. Skin provides an essential protective layer, prevents body fluids from evaporating in hot environments, and provides our most direct contact with the world.
What are mechanoreceptors?
Mechanoreceptors are sensitive to body distortion such as stretching or bending. They are spread throughout the body. At the heart of all the mechanoreceptors are unmyelinated axon branches that are sensitive to stretching, bending, pressure, and vibration. The receptors get depolarize therefore sodium channels open up.
What is pacinian corpuscle?
Pacinian corpuscle is the largest mechanoreceptor which lies deep in the dermis and can be as long as 2mm and 1mm in diameter. They have higher density in the fingers.
What are Ruffini’s endings?
Ruffini’s endings are types of mechanoreceptors found in both hairy and glabrous skin but they are smaller than pacinian corpuscles.
What are meissner corpuscles?
Meissner corpuscles are types of mechanoreceptors found in the ridges of glabrous skin (the raised parts of the fingertips). They are one-tenth the size of pacinian corpuscles.
What are Merkel’s disks?
Merkel’s disks are located within the epidermis. Each consists of a nerve terminal and a flattened non-neural epithelial cell (Mark cell)
What are krause end bulbs?
Krause end bulbs lie in the border of dry skin and mucous membrane such as around the lips and genitals. The nerve terminals look like knotted balls of string.
What are the receptor field sizes of the mechanoreceptors?
Meissner corpuscle and merkel’s disk have smaller receptor fields compared to Pacinian corpuscle and Ruffini’s endings
What is the adaptation rate of the mechanoreceptors?
Meissner’s and Pacinian corpuscle tend to respond quickly at first but then stop firing even though the stimulus continues, they are said to be rapidly adapting. However, Merkel’s disk and Ruffini’s ending are slowly adapting and generate more sustained responses during a strong stimuli.
What are receptor fields and how can they be mapped?
The receptor field is an area of the receptor array that upon stimulation generates a neural signal. Introducing a microelectrode into the median nerve of the arm, it is possible to record the action potentials from a single sensory axon and map its receptive field on the hand with a fine stimulus probe.
Why are fingertips much better for Braille reading than the elbow?
- There is a higher density of mechanoreceptors in the skin of the fingertip.
- Fingertips are enriched with receptors with smaller receptor fields such as Merkel’s disk and Meissner’s corpuscle.
- There is more brain tissue
- High resolution discriminations (know exactly where something is happening)
What are primary afferent axons?
Axons bring information from the somatic sensory receptors to the spinal cord or brain stem. They enter the spinal cord through dorsal roots and their cell bodies lie in the dorsal root ganglia.