peter simmons Flashcards
discuss the different components of extracellualr fluid
20% blood plasma which is contained in blood vessels
80% interstitial fluid which is contianed outside the blood vessels
concentrations of Cl, Na, Ca and K differ between the internal cells environment and the extracellular environment, where are the concentrations of each ion the highest
K+ is in higher concentration within cells
Na+, Cl- and Ca+ are at a higher concentration outside of cells
who coined the word homeostasis and who came up with the principles
walter cannon coined the word
claude bernard came up with the ideas for homeostasis
discuss the general anatomy of a neuron
dendrite; receive electrical signals
cell body; house nucleus
axon; carry spike away from cell body
terminal; transmit signal to next neuron via neurotransmitter
discuss 3 types of neuron cell
and discuss which of the 3 does not spike
bipolar cell in retina
purkinje cell in cerebellum with bushy dendrites
pyramidal cell in cerebral cortex with long dendrite and long axon
bipolar cell doesnt spike and doesnt have a long axon
discuss how the resting potential of a cell is maintained
1) Na/K pumps actively transport 3 Na’s out for every 2 K’s moved into the cell against their concentration gradients; the intracellular cytoplasm becomes 60-80mV more negative than the extracellular fluid
2) K channels are open; K moves out of the cell down their concentration gradient which then causes the inside to become more negatively charged, drawing K ions back into the cell. An electrochemical gradient is established (gradient of charge and concentration)
discuss evidence sorrounding
a) the fact that there is a voltage difference across the cell membrane
b) an experiment demonstrating how membrane potential changes
a) microelectrodes have been used to demonstrate that the outside the more positively charged than the inside
b) Horowitz and Hodgkins varied the external concentration of K+ and this changed the potentiol across the cell membrane
what is Nerst’s equation
voltage = ratio of internal K+ ions to extracellular K+ ions
what would happen when a frog and an invertebrate were palced in seawater
1) frog’s permeable skin would mean the frog becomes dehydrated due to water being drawn out of cells due to seawater having lower water ppotentiol
2) invertebrate wouldnt become dehydrated because its bodily fluid has a similar water potentiol to sea water
discuss the sequence of events leading to a spike
1) a depolarising signal causes some Na channels to open,
2) if enough depolarisation occours to exceed threshold potneitol, then volatge gated Na channels open, polarity reversed and the indside because more positive than the outside of the cell by 50mV
3) Na channels close (refractory period) and voltage gated K channels open
4) K leaves the cell (overshoot) and depolarises the cell again
5) Na/K pump resets resting potentiol
what causes the refractory period (keeping the spikes seperate)
closing of the Na channels
what is the purpose of the voltage gated K channels being slower than the voltage gated Na channels
everything happens in the correct order
how long is the refractory period
1-2 ms
what is the name for cells that can spike
excitable
what are spikes used for
long distance communication. without spikes electrical signals would fade away over distance as neurons are poor conductors of electricity
where is a spike generated and how do spikes travel
generated at the axon hillock (where the cell body meats the axon)
spikes travel for propogation; one part of the axon is excited which excites the next part fo the neuron
spikes are conducted a different speeds, which factors determine the speed of conduction
1) temperature; conduction is faster in higher temperatures
2) width of axon; wide axons conduct faster
3) present of myelin; presence of a myelin sheet causes saltatory conduction to occour which is quicker (spike jumps between gaps in myelin called nodes)
discuss the structure of myelin?
are vertebrate neurons myelinated?
are inverttebrate neurons myelinated?
what disease are associated with muations affecting myelination
glial cells acting as a lipid membrane
nodes are the gaps in the glial cells
vertebrate neurons are sometimes myelinated
invertebrates are not usually myelinated
multiple sclerosis
discuss the structure of voltage gated channels and how they open
voltage hated channels are mainly a helix shape, with their electrical charged on the outside of the protein. when the stimulus causes enough depolariasation to reach threshold potentiol, the channel spins and changes shape allowing entry of ions
what causes the release of neurotransmitter from the presynaptic knob
how does this neurotransmitter releases cause a PSP in the next neuron
the spike reaches the presynaptic knob and causes voltage gated calcium channels to open; when calcium enters the presynaptic knob it causes a cascade of reactions leading to vesicles of neurotransmitter moving to and fusing to the pre synaptic membrane
neurotransmitter binds to a chemically gated Na channel in the post synaptic membrane, causing entry of Na
which part of the process of synaptic transmission takes the longest
opening of the calcium channels in the presynaptic knob
discuss the different neurotransmitter used by vertebrates and arthropods
vertebrates use Acetylcholine
arthropods use glutamic acid (Glu)
what are the differences between spikes and post synaptic potentials (PSP’s)
spikes are caused by voltage gated channels where as PSP’s are caused by chemically gated channels.
Spikes are fixed amplitude discrete events where as PSP’s have to add to together to increases amplitude
Spike travel much longer distances than PSP’s and have a larger voltage
how many molecuels of Ach are needed to opent the chemically gated Na channels in the post synaptic membrane
2
who developed patch clamping and what is it
Neher and Sakmann. placing an electrode over a single ion channel
what are the three pieces of evidence for the idea that synapses are chemical and not electrical
1) theres a physcial gap
2) pippeting ach into cleft causes a psp
3) similar chemicals have the same chemical in their pre synaptic knob that causes PSP’s
what is unusal about the giants giant axon in the stellate ganglion
its a relay axon (causes a spike in the post synaptic axon)
which animal has much of its muscle converted to electric shock generating muscle
do these muscles contract? what is their function?
electric rays
the muscle does not contract, but it used to defentd the animal against predators
define neurotoxin and venom
a neurotoxin is a substances which acts on the nervous system to cause ill health
venom is a mixture of neurotoxins screted by animals
what are plant neurotoxins called
alkaloids
discuss the functions of neurotxins to animals and to physiological research
animals use neurotxins defensively to disable prey
neurotoxins can be used to investigate how the nervous system works
which scientist studied neurotoxins
claude bernard
what is the function of sensory neurones
convert physical and chemical signals into electric ones which are transmitted to the CNS for interpretation
a stimulus alters the ion flow into the cell
what are the two types of receptors in sensiry neurone cells
ionotrophic receptor cells; the stimulus directly opens the ion channel. for example a volatile chemical may may bind to the receptor channel and change its conformational shape
metabotrophic receptor cells; the stimulus binds to a G protein receptor, which activates a G protein leading to a cascade of effects involving secondary messengers leading to the channel being opened
what is a proprioreceptor
a receptor that monitors changes in body part position; mechanoreceptors in a crayfish’s tail
whats the difference between tonic stretch receptors and phasic stretch receptors;
phasic stretch receptors are more sensitive to changes in chretch
which group of animals posses hair cells?
what is the funciton of hair cells?
name 3 examples of animals using hair cells?
vertebrates have hair cells
they are cells 3 ‘hairs’ (cilia) and perform transduction. when the hairs are moved in a direction opens ion channels. no spike is performed but the cell releases neurotransmitters to a cell which can spike
fish have them in their lateral line sensory system to pick up stimuli of moving water
present in balance organs and indicate body position
Presen in mammalian inner ear and pressure waves moving them activate the receptor cells
in terms if sound, what are the three things an animal can distinguish
tone; frequency of soundwaves
loudness; amplitude of sound waves
source of sound;
what are two accessory structures that help animals capture environmental stimuli
lens of eye
ears
what is the name of the tissue with the 5 layers of cells involved in phototransduction
retina
what are the 2 types of photo receptors in vertebrates, how many of each are there and what are there function
Rods; 120 million
broad colour sensitiivity but particularly sensitive to low light levels
Cones; 5 million
sensitive to particular colours; are good for details in bright light
discribe the 5 layers of cells within the retina
retinal ganglion cells horizontal cells bipolar cells amacrine cells retinal ganglion cells
how many retinal ganglion cells are there
1.3 million
discuss the series of events that ococur when conditions become light
a photon hits the 11-cis retinal aldehyde of the rhodopsin molecule in the rod’s inner membrane, and causes it to change into an all-trans-retinal, which causes a confmarional change of the opsin protein, which activates a G protein, which releases its subunit which activates a phosphodiesterase (PDE) enzyme, which hydrolyses cGMP into gmp, causing Na channels to close, and hyperpolarisation of the rod cell to occour, this means no neurotransmitter is released to signal the bipolar cells
what is the G protein in the rod disc organelle inner membrane called
transducin
discuss the resting potentiol of rod cells
-35mV (rest)
how are vertebrates different to invertebrates in terms of phototransduction
invertebrates membrane depolarise (become less negative) upon photon action, where as vertebrates hyperpolarise
discuss adaption of photoreceptors
if the light stimulus intensity increases, then the effect a single photon has is reduced. means photoreceptors arent saturated and they can work over a broad range of light intensities
what is the name for the relative strength of two stimuli
contrast
equal ______ in stimulus strength cause equal _____ in response
contrasts
increments
what does lateral inhibition enhance
detection of edges
how much of body biomass does a human brain make up?
how much oxygen does it use
2%
20%
apart from humans, which other animals has a large brain weight:body mass
crow,
squirral,
hummingbird
discuss the cerebral cortex in birds comapred to fish, amphibians and reptiles
large and smooth
fish, amphibians and reptiles have a small and folded cerebral cortex
which part of the brian is used for facial recognition
temporal lobe (just above cerebellum)
what is the grandmother cell concept
a specific nueron will spike within the temporal lobe when you see your grandmother and other groups of neurons will spike to recognise other images
discuss lateral inhibition in eyes with reference to receptive fields
each cone/rod has a path infront of it in which incoming light is picked up.
retinal ganglion cells are ‘on central’ or ‘off central’ depending on weather light in the central part or the periphral part of the receptive field stimulates the cell
discuss spatial and temporal summation
spatial summation is when different axon synapses add together; simultaneous excitation must occour
temporal summation is when the same synapse causes PSP’s; the second PSP’s must occour before the first has diminshed
discuss the difference between an inhibitory synapse and an excitatory synapse
at excitatory synapses, a spike in the pre synaptic neuron is more likely to cause a spike in the post synaptic neuron
in an inhibitory synapse, a spike in the pre synaptic neuron is less likely to cause a spike in the post synaptic neuron. hyperpolarisation occours rather than depolarisation
how many skeletal muscles to humans have
650-850
how long is a sacromere
2 um
what is the name of the protein which connects myosin to the Z line
titin
what is the name of muscle cells and what do they consist of
muscle cells are called muscle fibres and they consist of many myofibrils
what is the mechanism by which excitation along a T tubule causes calcium release from a sarcoplasmic reticulum
depolarisation of T tubule activates a DHP receptor, which opens the ryanodine receptor and allows acalcium to leave the sarcoplasmic reticulum
what ensures that antagonistic muscles arent activated at the same time
an IPSP occours in the motor neuron for one of the muscles while an EPSP occours in the motor neuron for the other muscle
what is a ganglia in the nervous system?
and what animal is the model organism for this
a ganglia is a cluster of cell bodies
sea slug/sea hare (aplysia)
what does touching a sea hare do
causes gill withdrawn to protect the gills (graded strength of response depending on touch)
causes inking from the inking sac (all or nothing)
the same sensory neuron excited both motor neurons
define force
the ability to hold up a weight
what define force
how many cross brideges there are, therefore longer sacromeres can generate more force, such as those in invertebrates
what is maximum force called
tetanus
define velocity in terms of muscles
the speed at which a muscle contracts,
when a muslce is doing work, what is it doing
shortening
what is the equation for work
work=forcexdistance
what is the meaning of power
the rate of work (the rate of shortening
what is the equation for power
force x distance x speed
discuss the muscle problem
muscles achieve high force by forming number of cross bridges, but to contract quickly (fast velocity) cross bridges must be broken and remade. high force and high velocity dont occour at the same time
name an animal that has overcome the muscle problem
locust
what does max power involve
intermediate volocity and force
what is a motor unit
a motor neuron and the miscle fibres it innervates
what do tonic muscle fibres possess and why do they need them
they possess more than one NMJ (collection of synapses from different motor neurons) they posses multiple sites of excitation because the fibres dont spike, and the PSP created decreases with distance traveled
what is the name of a proprioreceptor in muscles that is a
muscle spindle
are insect muscles innervated my a few or many motor neurons
very few. the locust flight muscles are innervated by a single motor neuron
do inhibitory motor neurons exist in verebrates or invertebrates
only in invertebrates
