* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Life: The Science of Biology, Ninth Edition
Membrane potential wikipedia , lookup
Patch clamp wikipedia , lookup
Action potential wikipedia , lookup
Nervous system network models wikipedia , lookup
Resting potential wikipedia , lookup
NMDA receptor wikipedia , lookup
Single-unit recording wikipedia , lookup
Endocannabinoid system wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Biological neuron model wikipedia , lookup
Chemical synapse wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Synaptogenesis wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Sensory substitution wikipedia , lookup
Evoked potential wikipedia , lookup
End-plate potential wikipedia , lookup
Electrophysiology wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Neurotransmitter wikipedia , lookup
Signal transduction wikipedia , lookup
Molecular neuroscience wikipedia , lookup
SENSORY RECEPTION © 2012 Pearson Education, Inc. Ch. 46 Opener 1 Sensing Infrared Radiation Ch. 46 Opener 2 Echolocating around an Obstacle Course Fig. 27.2 Sensory Receptors Sensory receptors = specialized cells or neurons that detect – conditions of the external and internal world Sensory receptors convert stimulus to action potential – This is called sensory transduction Message of stimulus carried to CNS – Interpretation of stimulus depends on area of CNS stimulated © 2012 Pearson Education, Inc. • Sensory transduction begins with a receptor protein that opens or closes ion channels in response to stimulus • Changes in ion flow change membrane potential of sensory cell • Receptor potential = membrane potential of sensory cell Sensory Receptor May be Found on Plasma Membrane of a Separate Sensory Cell or on a Sensory Neuron © 2012 Pearson Education, Inc. Figure 46.6 The Skin Feels Many Sensations Sensory receptor on Separate Sensory Cell – Vision – Taste – Hearing – balance Sensory receptor on specialized sensory nerve ending – Pain – Heat – Touch – smell Changes in receptor potential lead to formation of action potentials in sensory neurons If receptor found on sensory neuron stimulus triggers action potentials in receptor cell itself © 2012 Pearson Education, Inc. Sweet receptor 2. sugar molecules bind to sweet receptors 2 Sugar molecule (stimulus) Membrane of a sensory receptor cell Signal transduction 3 pathway Ion channels Sensory receptor cell 4 Ion 3. the binding triggers some ion channels in the membrane to close and others to open 4. Change in ion flow change in membrane potential (receptor potential) of sensory cell LE 49-14 Taste pore Sugar molecule Sensory receptor cells Taste bud Tongue Sensory neuron G protein Adenylyl cyclase Sugar Sugar receptor ATP cAMP Protein kinase A SENSORY RECEPTOR K+ CELL Synaptic vesicle Ca2+ Neurotransmitter Sensory neuron How is stimulus interpreted? Different stimuli trigger different receptors and sensory cells; which trigger different sensory neurons and travel to different parts of brain “Sugar” interneuron “Salt” interneuron Sugar receptor cell Salt receptor cell Brain Taste bud Sensory neurons No sugar Increasing sweetness Taste bud No salt Increasing saltiness How is INTENSITY of stimulus detected? The stronger the stimulus, – the more neurotransmitter released by the receptor cell and – the more frequently the sensory neuron transmits action potentials to the brain. Repeated stimuli may lead to sensory adaptation, the tendency of some sensory receptors to become less sensitive when they are stimulated repeatedly. © 2012 Pearson Education, Inc. The stronger the stimulus, – the more neurotransmitter released by the receptor cell and – the more frequently the sensory neuron transmits action potentials to the brain. “Hairs” of a receptor cell Neurotransmitter at a synapse Sensory neuron Fluid movement Fluid movement More neurotransmitter molecules Fewer neurotransmitter molecules Action potentials Action potentials 1 Receptor cell at rest 2 Fluid moving in one direction 3 Fluid moving in the other direction Repeated stimuli may lead to sensory adaptation, the tendency of some sensory receptors to become less sensitive when they are stimulated repeatedly. Figure 29.3B_3 Fluid movement Fewer neurotransmitter molecules 3 Fluid moving in the other direction LE 49-2a Weak muscle stretch Muscle Stretch receptor Membrane potential (mV) Dendrites Strong muscle stretch –50 Receptor potential –50 –70 –70 Action potentials 0 0 –70 –70 Axon 0 1 2 3 4 5 6 7 Time (sec) Crayfish stretch receptors have dendrites embedded in abdominal muscles. When the abdomen bends, muscles and dendrites stretch, producing a receptor potential in the stretch receptor. The receptor potential triggers action potentials 0 1 2 3 4 5 6 7 Time (sec) in the axon of the stretch receptor. A stronger stretch produces a larger receptor potential and higher frequency of action potentials. Chemoreceptors Olfaction (smell) – Pheromones and VNO Gustation (taste) © 2012 Pearson Education, Inc. Fig. 27.4-1 Fig. 27.4-2 Figure 46.5 Taste Buds Are Clusters of Sensory Cells Figure 46.4 Olfactory Receptors Communicate Directly with the Brain Mechanoreceptors Hearing and Balance – Hair cells Lateral line in fish Pain, touch, muscle movements – Stretch receptors © 2012 Pearson Education, Inc. LE 49-8 Middle ear Inner ear Outer ear Semicircular canals Stapes Middle ear Incus Skull bones Auditory nerve, to brain Malleus Pinna Tympanic Auditory membrane canal Eustachian tube Tympanic membrane Oval window Cochlea Round window Eustachian tube Tectorial membrane Hair cells Bone Cochlea duct Vestibular canal Basilar membrane Axons of To auditory sensory neurons nerve Auditory nerve Tympanic canal Organ of Corti Figure 46.10 Hair Cells Have Mechanosensors on Their Stereocilia LE 49-2b No fluid movement “Hairs” of hair cell Fluid moving in one direction More neurotransmitter Neurotransmitter at synapse Less neurotransmitter –50 –50 –70 Action potentials 0 –70 Membrane potential (mV) –50 Receptor potential Membrane potential (mV) Membrane potential (mV) Axon Fluid moving in other direction –70 0 Vertebrate hair cells have specialized cilia or microvilli (“hairs”) that bend when surrounding fluid moves. Each hair cell releases an excitatory neurotransmitter 0 –70 –70 0 1 2 3 4 5 6 7 Time (sec) –70 0 1 2 3 4 5 6 7 Time (sec) at a synapse with a sensory neuron, which conducts action potentials to the CNS. Bending in one direction depolarizes the hair cell, causing it to release more 0 1 2 3 4 5 6 7 Time (sec) neurotransmitter and increasing frequency of action potentials in the sensory neuron. Bending in the other direction has the opposite effects. Thus, hair cells respond to the direction of motion as well as to its strength and speed. Figure 46.9 Sensing Pressure Waves in the Inner Ear Figure 46.9 Sensing Pressure Waves in the Inner Ear (Part 1) Figure 46.11 Organs of Equilibrium Figure 46.12 The Lateral Line Acoustic System Contains Mechanosensors Photoreceptors Detect various regions of electromagentic spectrum – Visible light – Infra-red – UV © 2012 Pearson Education, Inc. Figure 46.17 Convergent Evolution of Eyes Figure 46.21 The Human Retina Figure 46.19 Rods and Cones Figure 46.13 Light Changes the Conformation of Rhodopsin LE 49-20 Rod Outer segment Disks Inside of disk Cell body cis isomer Light Enzymes Synaptic terminal Cytosol Retinal Rhodopsin Opsin trans isomer Figure 46.20 Absorption Spectra of Cone Cells Figure 46.14 A Rod Cell Responds to Light (Part 2) Figure 46.15 Light Absorption Closes Sodium Channels LE 49-21 Light Active rhodopsin INSIDE OF DISK EXTRACELLULAR FLUID PDE Plasma membrane Inactive rhodopsin Transducin Disk membrane Membrane potential (mV) 0 Dark Light cGMP –40 GMP Na+ Hyperpolarization –70 Time CYTOSOL Na+ LE 49-22 Dark Responses Light Responses Rhodopsin inactive Rhodopsin active Na+ channels open Na+ channels closed Rod depolarized Rod hyperpolarized Glutamate released No glutamate released Bipolar cell either depolarized or hyperpolarized, depending on glutamate receptors Bipolar cell either hyperpolarized or depolarized, depending on glutamate receptors LE 49-23 Retina Optic nerve To brain Retina Photoreceptors Neurons Cone Rod Amacrine cell Optic nerve Ganglion fibers cell Horizontal cell Bipolar cell Pigmented epithelium