BIOL 453 - Professor Tagide DeCarvalho PDF

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Professor Tagide DeCarvalho...

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Central pattern generators Thursday, October 4, 2018 9:09 AM

Xenopus - clawed frog exhibits rhythmic swimming behavior as an escape behavior Wave of antagonistic muscle contractions on both sides alternately. Fictive preparation - no brain, no muscle movement (bungarotoxin is a neurotoxin that blocks synaptic transmission at the neuromuscular junction) to isolate firing patterns of spinal cord neurons. Neuromuscular junction - acetylcholine. Blocking muscle movement removes sensory feedback to nerves from the muscle, and keeps the specimen still while there are electrodes in the neurons. Sensory receptor in muscle - stretch receptor (fires more when relaxed/more stretched) Patellar stretch reflex Central pattern generator - CPG - neural circuit that produces rhythmic motor neuron firing. (tadpole) There are two half-centers, a left and a right with excitatory and inhibitory motor neurons. Positive feedback loop among excitatory neurons. When a half center on the left side is active, it is inhibiting the corresponding half center on the right side. Neuromodulation - one neuron --> many neurons Slow, neurotransmitters diffuse over large distances Synaptic transmission - one neuron --> one neuron Rapid action potentials that release neurotransmitters received by ligand-gated ion channels Short distances 10.23.18 Jamming avoidance response EOD = electric organ discharge An object in the electric field causes an increase in amplitude but no change in frequency. Fish change their frequencies when they encounter another fish. (one goes higher, one goes lower) CPG regulates frequency of EOD, but there is no internal reference of what the frequency is. These fish have electroreceptors all over their bodies. Level 1: 2 types of electroreceptors: T: time coder P: amplitude coder nE: command center Pacemaker neurons are the CPGs. Level 2: ELL: somatotopic connectivity Level 3: Torus semicircularis

Divided into laminae (sheets of cell bodies) Self versus non-self (changes in amplitude help recognize non-self)

Medial and lateral styloconica are involved in taste. Deterrence by rosemaric acid, same response to canna.

BIOL 453 Thursday, November 1, 2018 9:19 AM

Circadian rhythms and biological clocks Daily rhythms of many behaviors, chronobiology Experiment: demonstration of mouse locomotion circadian rhythm --> endogenous cues maintained rhythm in constant darkness. (internal clock) Free-running period - activity in the absence of exogenous cues The cycle does change slightly in the absence of exogenous cues. Actograms are used to show chronobiological data. Entrainment - external cues modify the internal clock Most effective when light cue is presented during the normal "dark" period Eclosion - adult fly emerges from pupal state In Drosophila - period gene transcription is regulated by the circadian rhythm. Suprachiasmatic nucleus (SCN) is the "clock" center of the brain, the pacemaker for the rest of the body. 11.08 Large scale navigation: migration and homing Homing: being able to locate home territory when foraging, etc. Underlying genetic component to compass direction and length of journey. (white stork & golden plover) Homing & long distance orientation (Starlings use a time-compensated sun compass). Overcast light - polarization patterns & UV wavelengths (pigeon) Star compass (songbirds) Fixate on points that are stationary and due north Magnetic compass experimental setup: Helmholtz coil generates a uniform magnetic field --> changed the direction of magnetic north and the birds oriented to that. Clockwise north up (opposite Earth's magnetic field) Counterclockwise south up ("control" magnetic field)

Salmon life cycle - olfactory imprinting hypothesis They come back home based on smell

Neuromodulation Tuesday, November 20, 2018 9:07 AM

Motivation: internal "factors" affect behavioral patterns Neural plasticity: neural circuits can produce difference behavioral outputs to the same stimulus. Two mechanisms: 1. Structural reorganization (when changes in motivation occur slowly, alterations in behavior are large, and the new motivational state needs to be maintained for a long period) a. Neurogenesis b. Dendritic changes 2. Biochemical switching (changes in motivation are fast, alterations in behavior are gradual and not large) a. Neurotransmitters b. "Diffuse" release - persist longer than neurotransmitters, slow acting receptors Dendritic plasticity: electric fish seasonal changes Chirps: short-term changes in frequency and amplitude as communication. Used by males to attract females during the breeding season. Breeding season environmental conditions simulated in the lab. Chirp-controlling neurons alter electric organ discharge during mating season. The length of the neurons is different based on what quadrant they are in relative to a ventricle. Unknown factor from ventricle changes the physiology....