Phy Sci 165 Combined Study Guides

Relationship between sound frequency and displacement of hair cells in the cochlear membrane

- Each hair cell responds to similar frequencies of displacement Afferent neurons from: - Basal-Proximal Region (hair cells closer to base) displaces high frequency - Middle Region displaces middle frequency - Apical End Region displaces low frequency

What factors influence length constant?

- Myelination increases membrane resistance - Increasing axon diameter reduces internal resistance

What happens when weakly electric fish sense an object in the water?

- Objects in the water distorts electric field - The field is sensed by electrosensory receptors in skin that depolarize with inward current, and hyperpolarize with outward current. - The receptors synapse spiking neurons that increase firing rate for inward current and hyperpolarize with outward current allowing the animal to sense and object in the environment.

Results of Crayfish stretch receptors bathed in TTX

- TTX eliminates action potentials ~ magnitude of stretch - membrane depolarizes ~ magnitude of stretch

dark current

- comes from an open cation channel gated by cGMP - in the dark, cGMP is synthesized

Adaptation used to survive in extreme heat conditions - Ground Squirrel

- controlled hyperthermia by periodic activity out of burrows - huddling at night conserves energy by saving body heat

artificial time-delay amplifier in insects

- detect direction of a sound source - interaural delay is not the arrivial of sound at 2 sides of body, it is the delay in sound reverberating through trachael system

Nernst equation

- determination of cell potential under non-standard conditions - relates measured cell potential to reaction quotient - allows determination of equilibrium constants

spatial code of activation by odorants

- each olfactory receptor neuron expresses 1 olfactory receptor - sensory neurons with the same receptor converge in the same spot in antennal lobe (glomerulus)

Explain the experimental set-up and significance of the Ussing chamber.

- frog skin between 2 compartments, divided into apical and basolateral sides of the mebrane - measures transepithelial fluid transport - follows net movement of water or solute across the membrane - amount of electrical current tells us how much biological current is carried by ions - when electrical current counteracts biological current, voltage across membrane goes to 0

absolute refractory period

- inactivation of voltage gated Na channels - period of time in which a cell is incapable of repeating an action potential

B-ecdysone significance

- increase of ecdysone from prothoracic gland coordinates metamorphic changes needed for growth and the timing of each molt

JH

- juvenile hormone that maintains growth phase and eventual sexual maturation

JH significance

- postpones metamorphosis until insect's size and age is attained - Increase of JH doesn't allow backwards slide bc of commitment peak - if JH, secreted from corpus allatum, is increased at molt, then molt is into the same stage (larva-larva) - if JH absent, molt is into next developmental stage (larva - pupa) - JK strong in adult to coordinate maturation of sex organs

length constant

- root of membrane resistance over internal resistance - distance over which voltage decays to 63% (-37%)

B-ecdysone

- steroid hormone needed for metamorphosis

What factors affect diffusion rate of a substance?

- surface area - substance concentration gradient - cotransporters using the concentration gradient of another substance - lipid solubility - diffusion thickness - quantity of transporters - ATPase

Adaptation used to survive in extreme heat conditions - Kangaroo Rats

- very low cutaneous water permeability - cool their exhaled air via nasal countercurrent exchangers - produce highly concentrated urine - restrict fecal water loss by reabsorption of water in food - metabolic water generation

threshold potential of action potentials

- voltage across cell membrane at which an action potential occurs 50% of the time - outward Inward K increases linearly with increasing V m: I Na increases nonlinearly with increasing V m - When V m reaches the point where outward I k < inward I Na, this is the threshold.

Adaptation used to survive in extreme heat conditions - Desert beetle

- water is recaptured as it condenses under the elytra and is reabsorbed at the abdomen - coloration, white elytra absorbs less infrared (IR) which makes the animal cooler and lose less water - active in cooler shade - orients body parallel to the sun's rays and absorbs less IR

Name the properties of Viscid spider silkWeb types made, stress, strain, breaking stress, maximum extensibility in relation to F-stop

- web types made: catching spiral of orb-web - stress: low tensile strength - strain: high strain before breaking - breaking stress: low stress before breaking - maximum extensibility: high, larger distance over which insect is slowed down --> smaller F-stop necessary to stop it

Name the properties of MA spider silk: Web types made, stress, strain, breaking stress, maximum extensibility in relation to F-stop

- web types made: dragline, web frame - stress: high tensile strength - strain: low strain before breaking - breaking stress: high stress before breaking - maximum extensibility: low, smaller distance over which insect is slowed down --> larger F-stop necessary to stop it

Describe each step of amino acid absorption from the gut lumen.

1. Amino acids are cotransported and energized by the K+ concentration gradient. 2. AAs and K diffuse down their concentration gradient into the bloodstream. 3. K+ diffuses along its concentration gradient into Goblet cells. 4. An H+/K+ antiporter moves K+ out, energized by the proton concentration gradient. 5. H+ is removed via proton pump ATPase.

artificial time-delay amplifier in insects (Steps)

1. Ear drum on one side connected to respiratory trachae system 2. sound pressure travels to other ear and creates time delay (delta t) 3. Sound reverberates before exciting ear on other side of body after delay 4. Produces ongoing disparity --> delay in sound reverberating through the system

spatial code of activation by odorants significance

A given odorant might activate some fraction of receptors and thus, activate some fraction of glomeruli. This provides a spatial code of brain activity corresponding to the odor.

Structure of Photoreceptors

Cilia (microvilli) of each photoreceptor arranged in parallel (and different photoreceptors cilia are orthogonal to one another)

Explain how the structure of photoreceptors affects the ability to see polarized light.

Each receptor is maximally stimulated by E-vector of polarized light oriented in parallel with cilia

Conclusions of Crayfish stretch receptors bathed in TTX

Receptor potential has an excitatory ionic current distinct from that which generates action potentials

Where does electroreception occur on weakly electric fish?

The tail houses modified muscle tissue that generates an electrical filed without contractile properties.

What is fluorescence recovery after photobleaching? Explain what is happening conceptually in this method at each labeled point on the graph below.

a. before photobleach b. laser photobleaches membrane, causes a hole in fluorescence c. recovery of green fluorescence begin due to lateral diffusions d. membrane can't fully recover since the destroyed proteins are irreversible, but lateral diffusion allows recovery over time

ostrich

concentrates urine to minimize water loss

driving force

difference between membrane potential and equilibrium potential Vm = Ea

hypotonic

inside of the cells have a higher substrate concentration than the solution, so water from the solution moves into the cell to make the concentration between the inside and outside of the cell equal (reach dynamic equilibrium)

myelination: definition, effect of increasing/decreasing myelination of length constant

layer of myelin around axons - increase: increases length constant - decrease: decreases length constant

dark current significance

light activates G-protein phosphodiesterase that inactivates cGMP and shuts the channel

axon diameter: definition, effect of increasing/decreasing myelination of length constant

radius of the axon - increase: increases length constant - decrease: decreases length constant

hypertonic

solution has a higher substrate concentration than inside the cells, so water inside the cell goes to the outside solution to make the concentration between the inside and outside of the cell equal (reach dynamic equilibrium

isotonic

solution has an equal substate concentration to the cells, cells and solution are in dynamic equilibrium

Time constant of an excitable cell

time is takes for V m to reach 63% of V max in response to current injection tau = RC V(t) = Vmax (1-e^-t/tau)