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Flashcards in peter simmons Deck (83):

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



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



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



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


what is the name of the tissue with the 5 layers of cells involved in phototransduction



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



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



equal ______ in stimulus strength cause equal _____ in response



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



apart from humans, which other animals has a large brain weight:body mass



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



how long is a sacromere

2 um


what is the name of the protein which connects myosin to the Z line



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



define velocity in terms of muscles

the speed at which a muscle contracts,


when a muslce is doing work, what is it doing



what is the equation for work



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



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