This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Ch. 10 The Nervous System: Sensory Systems I) General Principles of Sensory Physiology * Afferent – from periphery to CNS (remember affect vs. effect), either visceral (stimuli that arise within the body) or sensory (external stimuli) a) Visceral include chemoreceptors that monitor O 2 , CO 2 , and H + levels in the blood; baroreceptors which keep tabs on blood pressure; and mechanoreceptors in the GI tract that monitor stretch or distension; although the brain utilizes this information, we are not consciously aware of these stimuli b) Sensory System divided into somatosensory system (aka somesthetic), which deals with skin receptors and proprioception , the perception of limbs and the body; the special senses are touch, taste, smell, etc. c) Receptor Physiology – breakdown! – specific sensory receptors (specialized neuronal structures) detect a specific form of energy (modality, like light or sound waves) under the law of specific nerve energies – the modality to which a receptor responds best is called its adequate stimulus i) Sensory Transduction (1) The function of sensory receptors is transduction, or converting one form of energy into another, e.g. sensory transduction, in which receptors convert energy of the sensory stimulus into changes in membrane potential called receptor potentials (or generator potentials). These resemble postsynaptic potentials because they are GRADED potentials caused by opening and closing of ion channels, BUT they’re triggered by sensory stimuli and NOT bindings of neurotransmitters (2) Sensory receptors are either: (a) Specialized structures at the peripheral end of an afferent neuron (b) A separate cell that communicates via chemical synapse ii) Adaptation – some receptors continue to respond to a stimulus for as long as the stimulus is applied, but most adapt, which is a decrease over time in the magnitude of the receptor potential when a stimulus is constant (1) Tonic receptors (slowly adapting) can function in signaling the intensity of a prolonged stimulus (stretch, proprioreceptors) (2) Phasic receptors adapt quickly, and occasionally show a second smaller response called an off response (olfactory receptors, Pacinian corpuscles detect vibration in the skin) d) Sensory Pathways i) The specific neural pathways that transmit information pertaining to a particular modality are referred to as labeled lines , and each sensory modality follows its own ii) A sensory unit is a single afferent neuron and all the receptors associated with it, which are all the same type iii) The area over which an adequate stimulus can produce a response in the aff neuron is called the receptive field 1 iv)...
View Full Document
This note was uploaded on 04/07/2008 for the course APK 2105 taught by Professor Brooks during the Spring '07 term at University of Florida.
- Spring '07