Chapter 46 - Guyton Flashcards
Mechanoreceptors
detect compression or stretching of tissues
Thermoreceptors
detect changes in temperature
Nociceptors
pain receptors, detect damage occurring in tissues
Electromagnetic receptors
detect light in the retina
Chemoreceptors
detect taste, smell, oxygen level in arterial blood, osmolality of body fluids, carbon dioxide concentration, other chemical factors
Differential sensitivity of receptors.
they are sensitive to one type of stimuli and not others (rods and cones to light but not heat/cold, pain only receptive to pressure once it is enough to cause damage)
What is the “labeled line” principle?
each nerve tract terminates at a specific point in the central nervous system, and the type of sensation felt when a nerve fiber is stimulated is determined by the point in the nervous system to which the fiber leads
What is the receptor potential?
type of stimulus that excites the receptor, its immediate effect is to change the membrane electrical potential of the receptor
Mechanisms of receptor potentials.
1) mechanical deformation of the receptors (stretching of the receptor membrane and ion channels open) 2) application of chemical to the membrane (ion channels open) 3) change of temperature (alters the permeability of the membrane) 4) electromagnetic radiation (changes the receptor membrane characteristics and allows ions to flow through channels)
Maximum amplitude of most sensory receptors.
100 mV
The more the receptor potential rises above threshold level, the greater the frequency of what?
action potentials
What allows sensory receptors to have an extreme range of response, from very weak to very intense?
frequency of repetitive action potentials
transmitted from sensory receptors increases approx. in proportion to the increase in receptor
potential; very intense stimulation of the receptor causes progressively less and less additional increase in numbers of action potentials
What is adaptation of sensory receptors?
adapt either partially or completely to any constant
stimulus after a period of time; pacinian corpuscle
adapts extremely rapidly and hair receptors adapt
within a second or so, whereas some joint capsule and muscle spindle receptors adapt slowly
How do mechanoreceptors adapt?
receptor potential occurs at onset of compression; accommodation (inactivation of Na channels as fiber gradually accommodates stimulus)
What are tonic receptors?
slowly adapting receptors that can transmit signal as long as stimulus is present; examples are muscle spindles, Golgi tendons, pain, baroreceptors, chemoreceptors of carotid and aortic bodies