Bio 152 Final NotecardBulk Transport: oxygenate tissues far away from lungs, during digestion, during hormonesignalingCephalization: concentrating sensory organs and NS components at front of bodyNS 3 nerve cell types:1. Sensory neurons - activated by sensory input from the environment2. Interneurons - process info from sensory neurons + transmit to to different body region3. Motor neurons - produce suitable responses by stimulating musclesSignal Transmission1. Stimuli are received by the dendrites + cell body2. Synaptic stimuli are summed at the axon hillock, action potential is triggered if the sum ishigh enough3. Action potentials are conducted to the axon terminal → cause release ofneurotransmitters → these bind to receptors on the postsynaptic cell membrane → createa new signal in postsynaptic neuronOutside 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 cellbecomes less negative than outside of the cell- Increase in membrane potential = depolarization- Resting potential: -70 mV- Threshold potential: -55 mV- Max potential: +40 mVA. Resting potential- Na+ outside, K+ inside → channels closedB. Stimulus / Threshold- Some Na+ channels open → NA+ comes in- If threshold is passed they all openC. Depolarization- Na+ channels open, Na+ comes in → cell becomes positive- Chain reaction of Na+ channels opening down the axonD. Repolarization- Na+ channels close, K+ channels open- K+ moves out → cell becomes negativeE. Refractory Period- K+ leaves as K+ channels slowly close- Cell is more negative than usualF. Return to resting potential- Both Na+ and K+ channels close- Na+ / K+ pump returns Na+ and K+ to the right placesSaltatory propagation increase speed of signal transmissionSynapses1. Synaptic transmission begins w/ action potential conduction to axon terminal2. Depolarization open Ca2+ channels3. Vesicles fuse w/ postsynaptic membrane → release neurotransmitters into synaptic cleft4. Neurotransmitters bind to receptors on postsynaptic cell that are ligand/gated ionchannels → change in membrane potential5. After inactivation, neurotransmitters are reabsorbed into presynaptic terminal + stored invesiclesGlial cells: surround neurons + provide them w/ nutrition + supportNeurotransmitter 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 neurotransmittersSummed EPSPs- 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.EPSPs and IPSPs- Spatial summation: EPSPs at 2 or more diff. synapses set off a.p.- Cancellation: EPSP + IPSP may cancel each other out → no a.p.PNS: sensory + motor nervesCNS: brain + spinal cordPNS- Somatic (voluntary) - sending + responding to external stimuli; conscious reactions- Autonomic (involuntary) - regulated internal bodily functions; unconscious reactions- Sympathetic + ParasympatheticParasympathetic = “rest and digest”Sympathetic = “fight or flight”Muscle Contraction- Acetylcholine binds to muscle membrane receptors → depolarization of muscle cell +contraction- Motor endplate = synapse between motor neuron + muscle fiberAfferent 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 Circuit1. Strike patellar tendon w/ reflex hammer2. Stretch receptor in extensor muscle sends signal along sensory nerves3. Sensory neuron synapses w/ motor neuron in spinal cord4. Motor neuron sends excitatory signal to same extensor muscle → contracts5. Inhibitory interneuron inhibit contraction of opposing flexor muscleReciprocal inhibition: stretch receptors of knee extensors are activated, they also inhibit activeof opposing musclesChemoreceptors: respond to molecules that bind to specific protein receptors on cell membraneMechanoreceptors: respond to physical deformations of their membrane produced by touch- Deformation of receptor membrane opens Na+ channel → depolarizationPhotoreceptors: respond to light by closing Na+ channels → hyperpolarized- Inhibit firing rate of other neurons in eye rather than exciting themElectroreceptors: allow fish to detect weak electrical signalsThermoreceptors: respond to heat + coldNociceptors: pain receptorsA.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 signalsAdaptation: sensory receptors reduce firing rate if stimulus continues for a whileLateral Inhibition- Enhances edge + border detection by reducing excitation of adjacent interneuronsG-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 proteinsSmell- 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-channels → depolarization- A.p. travels down sensory neuron to glomerulus → sensory neuron synapses w/interneurons → relay info to brainTaste- Sweet, bitter, savor = G-protein coupled- Salty = Na+ depolarize + open Ca2+ channels- Sour = H+ channels depolarize + inhibit K+ channelsHair Cells- Stereocilia movement causes ion channels to open + depolarization- Neurotransmitters bind to receptors → alter firing rate- Statocysts w/ statolith = gravityVestibular System- Hair cells in semicircular canals sense angular motions - balanceOuter ear - transmits sounds into earsMiddle ear - amplifies waves that strike eardrumInner ear - hair cells convert fluid pressure waves into electrical impulse that is sent to brainThe Eye- Focus on close objects - ciliary muscles contract → lens rounds → increase light bending- Focus on far objects - ciliary muscles relax → lens flattens → reduce light bending- Opsin - convert light energy into electrical signals in receptor- Photoreceptors increase or decrease firing rate in