What are sensory receptors - ✔✔ components of the nervous system that that provide us with information about our external and internal
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Sensory receptor (aka transducer) general function - ✔✔ to respond to a stimulus and initiate sensory input to the CNS
Involves converting stimulus energy into an electrical signal. Original energy form detected is specific to the type of sensory receptor
Energy is always transducer to electrical energy and sent along a sensory neuron
What two features are critical to allow sensory receptors to function as transducers - ✔✔ 1. Sensory receptors, like neurons and muscle cells, establish and maintain a RMP across their plasma membrane
2. Sensory receptors contain modality gated channels within their plasma membranes.
What is a receptive field - ✔✔ the area within which the dendritic endings of a single sensory neuron are distributed.
Small receptive field provides us with the ability to identify the stimulus location more specifically
Only nerve signals that reach the _____ of the brain result in our conscious awareness - ✔✔ cerebral cortex
A sensory receptor must be able to provide the CNS with what characteristics regarding a stimulus - ✔✔ modality (form of a stimulus) - provided by a given type of sensory receptor relaying sensory input along designated sensory neurons to specific regions of the CNS
location
intensity - A greater or more intense stimulus results in both the most sensitive sensory receptors initiating nerve signals more frequently and the less sensitive sensory receptors (which are not typically active) initiating nerve signals
duration - all sensory receptors become less sensitive to a constant stimulus and initiate a progressive decrease in nerve signals
What is adaptation - ✔✔ The decrease in sensitivity to a continuous stimulus
Difference in adaptation is used to categorize sensory receptors as either tonic or phasic receptors
Tonic receptors - ✔✔ demonstrate limited adaptation
In response to a constant stimulus, tonic receptors continuously generate nerve signals and only slowly decrease the number relayed to the CNS
Phasic receptors - ✔✔ exhibit rapid adaptation to a constant stimulus. Generate nerve signals only in response to a new (or changing) stimulus and quickly decrease the number of nerve signals relayed to the CNS
What three criteria are used to categorize sensory receptors - ✔✔ receptor distribution
stimulus origin
modality of stimulus
Sensory receptor distribution - ✔✔ May be classified based upon their distribution in the body - General or Special senses
General sense receptors - ✔✔ Distributed throughout the body and simple in structure. Subdivided into two categories based upon their location - Somatic sensory and visceral sensory
Somatic sensory receptors - tactile receptors housed within both the skin and mucous membranes. Monitor several types of stimuli (object texture, pressure, stretch, vibration, temperature and pain). Also within joints, muscles, and tendons and conclude joint receptors, muscle spindles and Golgi tendon organs. Detect stretch and pressure relative to position and movement of the skeleton and skeletal muscles.
Visceral sensory receptors - ✔✔ located in the walls of the viscera and blood vessels.
Detect stretch in the smooth muscle within the walls of internal organs, chemical changes in the contents within their lumen (CO2 levels in blood), temperature and pain
Special senses - ✔✔ Located only within the head and are specialized, complex sense organs.
Olfaction (smell), gustation (taste), vision (sight), hearing (audition), and equilibrium (head position and acceleration)
Sensory receptors can also be classified based upon where the stimulus originates. What are the classificaitons? - ✔✔ Exteroceptors - detect stimuli from the external environment. Include somatic sensory receptors of the skin and mucous membranes, as well as the receptors of the special senses. Respond to a stimulus outside of the body. [Show Less]