Bio 152 Final Notecard Bulk Transport oxygenate tissues far away from lungs during digestion during hormone signaling Cephalization concentrating sensory organs and NS components at front of body NS 3 nerve cell types 1 Sensory neurons activated by sensory input from the environment 2 Interneurons process info from sensory neurons transmit to to different body region 3 Motor neurons produce suitable responses by stimulating muscles Signal Transmission high enough 1 Stimuli are received by the dendrites cell body 2 Synaptic stimuli are summed at the axon hillock action potential is triggered if the sum is 3 Action potentials are conducted to the axon terminal cause release of neurotransmitters these bind to receptors on the postsynaptic cell membrane create a new signal in postsynaptic neuron Outside has higher conc of Na Ca2 Cl Inside has higher conc of K Action Potential When nerve cell is excited membrane potential becomes less negative inside of cell becomes less negative than outside of the cell Increase in membrane potential depolarization Resting potential 70 mV Threshold potential 55 mV Max potential 40 mV A Resting potential Na outside K inside channels closed B Stimulus Threshold Some Na channels open NA comes in If threshold is passed they all open C Depolarization Na channels open Na comes in cell becomes positive Chain reaction of Na channels opening down the axon D Repolarization Na channels close K channels open K moves out cell becomes negative E Refractory Period K leaves as K channels slowly close Cell is more negative than usual F Return to resting potential Both Na and K channels close Na K pump returns Na and K to the right places Saltatory propagation increase speed of signal transmission Synapses 1 Synaptic transmission begins w action potential conduction to axon terminal 2 Depolarization open Ca2 channels 3 Vesicles fuse w postsynaptic membrane release neurotransmitters into synaptic cleft 4 Neurotransmitters bind to receptors on postsynaptic cell that are ligand gated ion channels change in membrane potential 5 After inactivation neurotransmitters are reabsorbed into presynaptic terminal stored in vesicles Glial cells surround neurons provide them w nutrition support Neurotransmitter Release Ca2 bind to calmodulin starts signal transduction pathway Calmodulin activated PK2 PK2 phosphorylates synapsin causes active proteins to release vesicles Vesicles are docked adjacent to membrane where snare proteins await release Vesicles are snared fused recycled to store neurotransmitters No summation multiple EPSPs widely spaced in time don t set off a p Temporal summation EPSPs arrive quickly at a synapse set off a p Spatial summation EPSPs at 2 or more diff synapses set off a p Cancellation EPSP IPSP may cancel each other out no a p Summed EPSPs EPSPs and IPSPs PNS sensory motor nerves CNS brain spinal cord PNS Somatic voluntary sending responding to external stimuli conscious reactions Autonomic involuntary regulated internal bodily functions unconscious reactions Sympathetic Parasympathetic Parasympathetic rest and digest Sympathetic fight or flight Muscle Contraction contraction Acetylcholine binds to muscle membrane receptors depolarization of muscle cell Motor endplate synapse between motor neuron muscle fiber Afferent Neurons transmits impulse from sensory receptors in skin to CNS to CNS Efferent Neurons transmits impulse from CNS to muscles away from CNS Rapid Response in Reflex Circuit 1 Strike patellar tendon w reflex hammer 2 Stretch receptor in extensor muscle sends signal along sensory nerves 3 Sensory neuron synapses w motor neuron in spinal cord 4 Motor neuron sends excitatory signal to same extensor muscle contracts 5 Inhibitory interneuron inhibit contraction of opposing flexor muscle Reciprocal inhibition stretch receptors of knee extensors are activated they also inhibit active of opposing muscles Chemoreceptors respond to molecules that bind to specific protein receptors on cell membrane Mechanoreceptors respond to physical deformations of their membrane produced by touch Deformation of receptor membrane opens Na channel depolarization Photoreceptors respond to light by closing Na channels hyperpolarized Inhibit firing rate of other neurons in eye rather than exciting them Electroreceptors allow fish to detect weak electrical signals Thermoreceptors respond to heat cold Nociceptors pain receptors A P Firing Rate Nerve impulse need to Convey strength of signal Carry info about weak signals Convey location of signal course Filter out unimportant background signals Adaptation sensory receptors reduce firing rate if stimulus continues for a while Enhances edge border detection by reducing excitation of adjacent interneurons Lateral Inhibition G protein Extracellular ligand specific 3 subunits alpha beta gamma Receptor binds its ligand it changes shape energizing G protein Signal transduction pathway is invoked subunits interact w other proteins A p produced when odorants bind to membrane receptors sent to olfactory interneurons Odor molecules bind to receptors G protein release signal transduction pathway G proteins phosphorylate adenyl cyclase activates cAMP opens Ca2 Na Cl A p travels down sensory neuron to glomerulus sensory neuron synapses w channels depolarization interneurons relay info to brain Sweet bitter savor G protein coupled Salty Na depolarize open Ca2 channels Sour H channels depolarize inhibit K channels Smell Taste Hair Cells Stereocilia movement causes ion channels to open depolarization Neurotransmitters bind to receptors alter firing rate Statocysts w statolith gravity Vestibular System Hair cells in semicircular canals sense angular motions balance Outer ear transmits sounds into ears Middle ear amplifies waves that strike eardrum Inner ear hair cells convert fluid pressure waves into electrical impulse that is sent to brain Focus on close objects ciliary muscles contract lens rounds increase light bending Focus on far objects ciliary muscles relax lens flattens reduce light bending The Eye Opsin convert light energy into electrical signals in receptor Cones color Cones most concentration in fovea center Rods cells in periphery Photoreceptors increase or decrease firing rate in retina rods light Phototransduction Cascade neurotransmitters No light Na into rod cell membrane potential is positive cell releases Light phototransduction cascade activated hyperpolarization b c of leak K channels K flows out cell becomes negative no