General Biology2 Summers |
Respiration and oxygen availability Heart and Circulation/Transport Nutrition, Digestion, Metabolism Excretion and Elimination |
Chemical Messengers Sexual Reproduction Neuronal Structure & Signals Sensory Reception |
text:Biological Science 5th Edition - Freeman ..: Read Chap 47 for this lecture Integration of Neural Function Neuromuscular Action - Behavior syllabus Figures acronyms end |
XV. Sensory Reception A. Neural Sensory Receptors are Transducer Neurons 1. convert external stimulus into a neural impulse a. stretch/displacement reception, photoreception, chemoreception B. Stretch and Displacement Reception 1. associated with touch, hearing, balance, temperature 2. specialized dendrites are placed so that mechanical changes will cause them to bend a. bending stretches the membrane to open ion channels which allows for depolarization i. depolarization begins the action potential 3. phonoreception a. hair cells - size and length associated with different frequencies of sound 4. nociception - pain 5. touch and balance a. equilibrium receptors in the vestibular apparatus of the inner ear evolved from lateral line of fishes C. Chemoreception 1. taste and smell 2. chemically alter neuronal (receptor) membrane permeability a. ions may cross the membrane ® depolarization ® Action Potential D. Photoreception 1. sight, temperature, light a. many photoreceptors are capable of detecting light without delineating images i. infrared sensitive heat pits of pit vipers ii. parietal eye of lizards (1) lens (2) connected to pineal - melatonin secretion in darkness 2. Retina (neural lining) contains photosensitive molecules a. found in the rods and cones = photoreceptive neurons i. in membranes of flattened discs in the outer segment of these neurons (1) away from the lens b. Rhodopsin i. pigment made from opsin (protein) and retinal (vitamin A derivative) ii. energy from light causes a configurational change in retinal, unbends it (bleaching) iii. activated rhodopsin binds a G protein, closing membrane channels, hyperpolarizing the cell (1) stops the ions from leaking in or out iv. hyperpolarization travels down the neuron just as depolarization would v. signal is graded - more hyperpolarization with more light (1) depolarization in normal neurons is all or nothing: graded responses come from the number of neurons depolarizing