animal phys Flashcards
What are the two proteins that are most involved in establishing cell resting potentials?
Sodium-potassium exchange pump;
one kind of potassium ion channel
Who first said: ‘Constancy of the internal environment is the condition of free life’?
Claude Bernard
What can you use to measure the voltage across a cell membrane?
A microelectrode.
What functions does the resting membrane potential serve?
Provides energy for various things, including:
transport of substances
electric signals
cell volume
How do ions move across a cell membrane?
Through open ion channels (driven by electrochemical gradient);
or by the action of ATP-driven pumps
What determines the net direction in which ions move through open channels?
The electrochemical gradient
What two features are responsible for the resting potential?
Unequal concentration of potassium either side of cell membrane (more concentrated inside); and open potassium channels in resting cell membrane
What does the equilibrium potential for an ion mean?
Electrical potential (votage) across cell membrane at which the electrical and concentration (or chemical) gradients for the ion are equally balanced
What is the name of the equation that describes the relationship between a membrane potential and concentration gradient for an ion?
Nernst equation
Which are the major inorganic ions involved in electrical signalling in neurons and muscle cells?
Potassium; sodium; calcium; chloride
What is an increase in membrane polarity from resting potential called?
hyperpolaristion
How fast do spikes travel?
between 1m/s-100m/s
In which animal, and by who, was the ionic mechanism for a spike first demonstrated?
Squid; Hodgkin & Huxley
In what ways do properties of voltage gated Na+ and K+ channels differ?
Sodium channels open faster and get deactivated
What ensures that spikes are discrete events?
Sodium channel inactivation – means there is a refractory period following a spike during which a second spike cannot be triggered
What channels open in a presynaptic terminal to trigger the release of neurotransmitter?
voltage gated calcium channels
What technique is used to measure ion flow through a single channel?
patch clamping.
Give 3 examples of model synapses and the main findings from them.
Neuromuscular junction: Mechanism of psps
Squid giant axon: how pre synaptic potential regulates neurotransmitter
Electric ray organ: structure of a transmitter receptor plus channel
Who developed the patch clamping technique?
Neher & Sackmann
What does ‘IPSP’ stand for?
Which ions are usually involved in generating IPSPs?
Inhibitory postsynaptic potential
Either chloride or potassium
How can venoms immobilise potential prey – what are their possible sites of action?
Neuromuscular synapses
What compound or compounds specifically stop the sodium-potassium exchange pump from working?
oubain
Where does TTX come from?
Bacteria; found inside tissues and venom glands of various animals – primarily pufferfish
Where does atraxotoxin come from and what does it do?
Funnel web spider; stops the inactivation of the voltage-gated sodium channels in axons of some animals
What substance blocks the axonal voltage-gated potassium channel?
Tetraethylammonium (TEA); apamine – bees; dendrotoxin - mambas
What kind of toxin is Prof. Olivera famous for researching, and what animals produce these toxins?
Conotoxin (from cone snails)
How does ‘botox’ work?
Blocks neuromuscular junction by blocking exocytosis of neurotransmitter
What is the excitatory neurotransmitter that lobster motor neurons use?
Glutamic acid
What kind of chemical is curare?
and what is its major use
alkaloid and for muscle relaxation in surgery
What is ‘transduction’?
Conversion of a stimulus into electrical signals in a sensory receptor cell.
What causes a receptor potential in a sensory receptor cell?
Transduction leads to a change in the flow of ions through channels in the cell membrane.
What is the name for the class of sense organs that monitor movements of parts of the body?
proprioceptors
What is the coiled structure of the inner ear of mammals or bird called?
cochlea
What length is a sarcomere stretched to for max force ?
2-2.25 micrometers
What is a metabotopic receptor?
In metabotropic receptors, the protein that absorbs energy from the environment is separate from the ion channels.
What is the photo-pigment?
Rhodopsin: an aldehyde (retinal) associated with a protein (opsin).
What does light do to rhodopsin ?
Changes the conformation of the retinal, from 11-cis retinal to its isomer, all-trans-retinal. This stretches covalent bonds with the opsin, which activates an enzyme-like site on the opsin.
Who discovered lateral inhibition?
hardline
What does lateral inhibition do?
Enhances detection of edges in images
Name the neuron types on the vertebrate retina.
Photoreceptors (rods & cones) Bipolar cells Retinal ganglion cells Horizontal cells Amacrine cells
Which of these types are responsible for lateral interactions?
Horizontal cells
Amacrine cells
Who made significant discoveries about responses of neurons in the visual cortex in the late 1950s?
David Hubel and Torsten Wiesel
Where is the ‘site of decision’ in a vertebrate motor neuron?
Axon hillock
Who was the first person to make intracellular recordings showing how they integrate different psps?
J C eccles
who developed the sliding filament theory ?
A F Huxley and HE Huxley
What is the structure at which sarcoplasmic reticulum associates with a t-tubule called?
triad
At what shortening speed do most muscles develop maximum power?
0.4 of maximum speed
Who conducted the experiment on cell membrane resting membrane potential ?
Hodgkin & Horowicz
