Flashcards in Animal Physiology 1 Deck (66):
Who said 'constancy of internal environment is the condition of free life'
Who coined the term 'homeostasis'?
Why is it not good to link body temp. to homeostasis?
Ectotherms/endoderms regulate temperature differently
What is a cell's maintained resting potential?
-60mV - -80mV
How is resting potential measured?
using an intracellular microelectrode
What 2 factors are involved with maintaining homeostasis?
Unequal distribution of K+
Selective permeability of cell membranes to K+
How is cell resting potential maintained and established?
K+ ion channel
How does the Na+/K+ pump work?
Uses energy (ATP) to move ions against their conc. gradient
In what ratio is Na+ exported and K+ imported?
How does K+ leave cell when channel is open?
How can K+ equilibrium be calculated?
Which part of a neuron spikes?
What kind of channels are in the axon?
What kinds of channels are in the dendrites?
What is a spike?
brief, pulse-like electrical event
How does a spike travel?
How long does a spike last?
1/1000th of a second
What is the function of a spike?
Amplifies electrical signal and carries electrical excitation along axon
What's occurring at resting potential?
K+ channels open
Membrane potential at constant value
Whats happening when threshold is reached?
Na+ channels open
Na+ enter neuron via diffusion
(this is the electrochemical gradient for sodium)
What happens in the rising phase?
More and more Na+ enter axon
Axon becomes less negative (~50mV)
Electrochemical gradient and conc. gradient are equal
Give an example of a model synapse?
Frog neuromuscular synapse
How is neurotransmitter released?
Excitation opens voltage gated Ca++ channels in presynaptic terminals
Ca++ enters cell causing strong electrochemical gradient
Increased Ca++ causes synaptic vesicles to fuse with pre-synaptic membrane
What organism is it very clear to see two axons involved in synaptic transmission?
Giant squid axon
What is evidence for neurotransmitter release and who did the study?
Llinas and Nicholson injected aequorin into pre-synaptic terminal while recording pre/post potentials
Who developed patch clamping?
Neher and Sakmann
What kind of channels does a PSP have?
What are toxins used for?
Who looked into effect of curare on muscle?
What toxins target sodium-potassium pump? Where is it from?
Alkaloid found in foxgloves
What targets voltage-gated Na+ channels? Where is it from?
TTX - found in pufferfish
Who researched TTX? How does it work?
Hodgkin and Huxley
It blocks Na+ channel like a cork
What toxin inactivates Na+ channels?
Atracotoxin - made my Sydney funnel web spider
What targets voltage-gated K+ channels?
What targets voltage-gated Ca++ channels?
Who discovered cone shells and conotoxins?
How does a cone shell release its toxin?
What toxins target neurotransmitter release?
Botulinum toxin - used in botox, blocks exocytosis
Black widow spider venom - uncontrolled exocytosis
What targets the neurotransmitter receptors?
Alkaloid curare - blocks nAch
Alpha bungarotoxin from Bungarus - sticks to nAch receptors
What are the neurotransmitters used in vertebrates and arthropods?
Vertebrates - acetylcholine
Arthropods - glutamate
What does a sensory cell do?
transduce physical or chemical information into electric signals
Name a model receptor cell
Crayfish abdominal stretch receptor
What is a proprioceptor
Sense organ that monitors the position or change in position of an animal's body parts
In crayfish, which type or stretch receptor adapts more strongly? Which is less strong?
Phasic - adapts more strongly, initial stretch causes many spikes then adaptation occurs
Tonic - sustains spikes throughout duration of stretch
What range of tone can humans hear?
10Hz - 20kHz
What range of tone can dogs hear?
40Hz - 60kHz
What range of tone can a bat hear?
20Hz - 150kHz
Where is the basilar membrane least stiff and widest?
What is a good model organism to see photoreceptor cells?
Necturus, a salamander
What are rod cells sensitive to?
low light levels
What are cone cells sensitive to?
good for detail in bright light
What is the dark resting potential?
What absorbs light photons?
photopigment molecule Rhodopsin
What are rhodopsins made up of?
What is activated when a light photon is absorbed?
11-cis-retinal ---> all-trans-retinal
Transducing in disc membrane activated
Phosphodiesterase in disc membrane activated
What is high in conc. in in the cytoplasm in the dark?
cyclic GMP - opens a sodium channel
Why is amplification necessary?
high sensitivity in low light conditions
Why is adaptation important?
Allows photoreceptors to work in a range of light intensities
What organism is a model for image processing?
Limulus - horseshoe crab
What do mirror neurons respond to?
The site of objects moving in particular ways
Which part of the brain is associated with facial recognition?
Who established centre-surround receptive field?
Who theorised that neurons in the visual cortex respond to light/dark sports poorly but lines or edges vigorously
Hubel and Wiesel
What is integration?
Neuron combines different PSPs it receives, enables nervous systems to make decisions
What are the two types of integration?