Bio Lesson 10: Organisms sense their environment 3 categories of receptors and function - sensory receptors detect info from both inside and outside the body - receptors that detect stimuli within the body interoceptors - Receptors that detect stimuli from outside the body exteroceptors - Receptors are categorized by the type of stimuli they respond to; 3 types: 1. Mechanoreceptors: detect mechanical forces Touch (pain and pressure) Hearing (special sense) Balance (special sense) 2. Chemoreceptors: detect chemical stimuli Taste (special sense) Smell (special sense) pH 3. Electromagnetic receptors: detecting electromagnetic energy like light and heat Vision (special sense) Conveying sensory information - 4 steps in the process 1. stimulation: occurs when the stimulus impinges on a receptor 2. transduction: stimulus energy converted into graded potentials in the sensory neurons dendrites 3. transmission: graded potentials are transformed into action potentials along the axon of the sensory neuron and conveyed to the CNS 4. interpretation: brain forms a perception of the stimulus; perception may not be the exact match to reality (optical illusions) Sensory transduction and transmission - Conveying information from sensory neurons to the brain - EPSP: Ligand gated ion channels - ligand is the neurotransmitter released by the presynaptic neuron - Receptor potential is very similar to EPSP except that instead of receiving stimulation from another neuron the receptor receives a stimulation from a stimulus to which it is sensitive Stimulus gated ion channels: opens when the cell is touched Receptor potential is formed: typically in form of depolarization; graded potential larger the stimulus, larger the depolarization In order for the action potential to be formed, the receptor potential must exceed the threshold potential Action potentials ARE NOT GRADED all or nothing - Large stimulus produces a large receptor potential which gets converted into very frequent action potentials Mechanoreceptors - Come in many forms: pain heat cold touch and pressure - Nociceptors
Pain Noxious substances and tissue damage Free nerve endings Particular concentrated where pain is likely to occur -
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- Fall '08
- Biology, cilia