Chapter 10 Flashcards
Perception
The conscious interpretation of the world based on the sensory systems, memory, and other neural processes
Visceral afferents
Visceral receptors transmit info to the CNS by this class of afferent neurons
Chemoreceptors- monitor O2, CO2, H+ lvls in blood
Baroreceptors- certain vessels that monitor blood pressure
Mechanoreceptors- gastrointestinal that monitor stretch or distention
Somatosensory system
Necessary for perception of sensations in the skin(somesthetic) and position of limbs (proprioception) which depends on muscles and joint receptors
Sensations: pressure, temperature, pain, and body position
Special senses
Vision Hearing Balance Equilibrium Taste Smell
Adequate stimulus
The modality which a receptor responds best to
Sensory transduction
Receptors convert the energy of a sensory stimulus into changes in mem potential call receptor potential or generator potentials (opening and closing of ion channels)
Sensory receptor forms
1: specialized structure at the peripheral end of an afferent neuron uses mem potential to propagate action potentials
2: separate cell that communicates through a chemical synapse with an associated afferent neuron used the release of neurotransmitters
Slowly adapting or tonic receptors
Show little adaptation and can function in signaling the intensity of a prolonged stimulus
Best respond to pressure
Ex. Muscle stretch receptors
Rapidly adapting or phasic receptors
Adapt quickly and thus function best in detecting changes in stimulus intensity
Best responds to vibration
Off response- some show a second smaller response upon termination of a stimulus
Ex. Olfactory receptors, pacinian corpuscles, which detect vibration in the skin
Labeled lines
The specific neural pathways that transmit info pertaining to a particular modality, each modality follows its own line
Sensory unit
Comprises a single afferent neuron and all the receptors associated with it of the same type
Receptive field
The area over which and adequate stimulus can produce a response in the afferent neuron
First order neuron
The afferent neuron that transmits info from the periphery to CNS
They may diverge within the CNS and communicate with several interneurons
Interneurons may receive converging input from several first order neurons
Thalamus
Major relay nucleus for sensory input, consist of second order neurons
Third order neurons
Form synapses with second order neurons, and transmit info to the cerebral cortex for sensory perception
Sensory coding
How a sensory receptor determines the location, strength, and type of stimulus
Stimulus type- coded by receptor and pathway(s) activated
Sensory strength- coded by the frequency of action potential and number or receptor activated
Sensory location (tactile, proprioceptive, and visual stimuli)- coded by receptive fields
Acuity
Precision with which the location of a stimulus is perceived
Depends on size, number, and overlap of receptive fields called lateral inhibition
Localization is more accurate in places of smaller receptive fields, however done by the overlapping of fields
Lateral inhibition
A stimulus that strongly excites receptors in a given location inhibits activity in the afferent pathways of other nearby receptors
Synesthesia
May hear colors, see sounds, or taste shapes
Due to developmental anomalies in the wiring of CNS, where different pathways intertwine
Two point discrimination
Measure of tactile acuity, the ability of a person to perceive two fine points pressed against the skin as two distinct points
Two point discrimination threshold; The minimum distance between two points to be perceived as separate of two diff afferent neurons
Close areas: lips finger tips (great acuity)
Further apart: back, thigh, upper arm (low acuity)
Somatoreceptors
Proprioreceptors- muscles joints
Mechanoreceptors- pressure force vibration
Thermoreceptors- skin temp
Nociceptors- tissues damaging pain, noxious stimuli
Widest variety of Receptor types
Free nerve endings
Somatic sensory receptor types that lack identifiable specialized structures
Mechanoreceptors in skin
Superficial layers epidermis: Merkel’s disks and Meissner’s corpuscles ( only hairless glabrous areas)
Inner layer dermis: hair follicle receptors, pacinian corpuscles, Ruffini’s endings
Size of receptive fields vary greatly
Thermoreceptors in the skin
Respond to temp change around receptors and tissues not external air.
Warm receptors: respond to 30°C-45°C TRPV
Cold receptors: respond to 35°C-20°C TRPM, TRPA
Actions potentials frequency increases to 45°C, then decrease rapidly
Free nerve endings with temp sensitive ion channels called (TRP) channels