Excitable cells Flashcards
What do dorsal and ventral mean
Back & belly
what do cranial and caudal mean
head end & tail end
what do proximal and distal mean
close to and far away
what do anterior and posterior mean
front and back end
what is rostral interchangeable with
it is interchangeable with anterior and cranial in quadrupeds
what do medial and lateral mean
towards the midline & away from it
What are the two main subdivisions of the nervous system
central nervous system (CNS)
& peripheral nervous system (PNS)
What are motor/efferent neurons/nerves used for.
They carry signals TOWARDS the target tissue or organ
what are sensory/afferent neurons/nerves used for
detect change in the environment and carry signal about change to CNS
What are the two main structures in the CNS
Brain and spinal cord
what are the 4 main subdivisions of the CNS (this is including the divisions of the brain)
Forebrain, midbrain, hindbrain and spinal cord
What are the two main divisions of the PNS
sensory (afferent) division and motor (efferent division)
What type of nerves make up the Peripheral nervous system
cranial nerves & spinal nerves
What are the two division of the motor division of the PNS
Autonomic nervous system & Somatic nervous system
What are the two division of the motor division of the PNS
Autonomic nervous system & Somatic nervous system
Which of the two motor nervous systems is responsible for VOLUNTARY control
Somatic
which of the two nervous systems is responsible for INVOLUNTARY control
autonomic
what are the two subdivisions of the autonomic nervous system
Sympathetic and parasympathetic
What is the function of the sympathetic division of the ANS
mobilises body systems during activity
(Fight or flight response)
what is the function of the parasympathetic division of the ANS
Housekeeping functions & energy conservation
What brain divisions are common to all vertabrates
olfactory bulb, cerebral hemispheres, cerebellum, optic, tectum, medulla oblongata
What is special about jellyfish and other primitive animals that dont move
they do not have a nervous system but have a nerve net
what is the nervous system of arthopods like
organised, have a nervous brain and ventral nerve cords
where are the telencephalon & diencephalon located
forebrain
what forms part of the brain stem and also contains the mesencephalon
midbrain
what contains the rhombencephalon
hindbrain
what does the brainstem consist of
the midbrain and hindbrain
what are the inital 3 layers of an embryo and what do they become
endoderm- linings of organs
mesoderm - bones and muscles
ectoderm - nervous system & skin
What is the notocord derived from and what is it important for
- derived from the mesoderm & important for signalling
What is Anencephaly
a condition in which the neural tube closes,the anterior pore does not seal and the brain doesnt develop - fatal
What is spina bifida
it is resultant of failure for the posterior neural tube to close.
It typically results in paralysis
How many ventricles does the brain have and where are they?
- There are two lateral ventricles located at the top. The third ventricle is located in the centre and the 4th is located at the bottom, near the brainstem
What is the function of the brains ventricles
They contain CSF and act to provide nutrients, remove waste and cushion and support the brain
How do you decrease neural tube defects at birth?
by supplementing diet with folic acid in early pregnancy
what increases the risk of spina bifida
anti epilepsy/bipolar drugs interfere with folate metabolism
how many swellings are there at the rostral end of the neural tube when an embryo is 3-4 weeks old
there are 3 swellings and they become the primary Vesicles within the brain (forebrain,midbrain & hindbrain )
what is the oldest part of the brain
brainstem
what is the oldest part of the brain
brainstem
which part of the brain is the decision matrix
brainstem
What is hydrocephalus and how can it occur
an excess of CSF in the brainstem and can occur due to an injury to another part of the brain
what does the diencephalon contain
it contains the thalamus (used in sleep, & concious movement) and the hypothalamus (used in homeostasis and reproduction)
What is cerebella agnesis
complete absence of the cerebellum. Non-fatal, can result in mild cognitive impairment & medium motor problems
What is the neocortex
a highly developed 6-layer structure of the cortex that mammals have, the number of neurons is related to intelligence
why does cortical folding occur
to increase processing power/intellignece as it increases the number of cortical neurons
what is a dip in the cortex fold called
sulcus
what is a peak in the cortex fold called
gyrus
what is the frontal lobe used for
actions, motor control, speech control and emotion
what is the parietal lobe used for
sensory & language functions
how does sensory info enter the spinal chord
via dorsal roots (afferent neurons)
what do the ventral roots of the spinal cord contain
motor info (efferent neurons)
What is grey matter and what kind of structure does it have
neural cell bodies
butterfly structure
what is white matter
myelinated axons
what is the function of the occipital lobe
visual processing
what is the function of the temporal lobe
memory as well as sensory and language based info
Where is the somatomotor cortex( aka the primary motor cortex)
in the frontal lobe
which lobe is the somatosensory cortex located in
parietal lobe
What does decussation (to become crossed) mean in a neurological sense
we see contralateral motor and sensory pathways : the right side of the brain controls and receives sensory signals from the left side of the body and vice versa
What did golgi invent and how did this help him
invented silver staining, allowed to see structure of typical neuron due to staining
Which two principles did Cajal develop
Principle of dynamic polarisation
Principle of connectional specificity
what is the principle of dynamic polarisation
- neurons have preferred transmittance directions
what is the principle of connectional specificity
neurons do not make random connections, they contact other neurons and only the specified structures on them
what is the resolution of the human eye
0.1mm
what is the resolution of a Light microscope
0.1μm
what is the resolution of a Electron microscope
0.1nm
What is a disadvantage of using an electron microscope
the cells have to be fixed (dead)
what is florescence
- a property in which if a substance has light of particular wavelength shone on it, it emits light of a different wavelength
how is immunoflourescence labelling done
Prepare selective antibody tagged with fluorescent label
Add to tissue and allow to bind strongly
Wash off any free labelled antibody
Look for where the fluorescence is
Image distribution of fluorescence (corresponds to target proteins distribution)
what is often tagged with flourophores to locate specific cell components
antibodies
what is a limitation of flourescence staining
you need to have antibodies against proteins that only occur in neurons or whatever you’re comparing them to
what is confocal microscopy
-focusing a laser at diff levels in a piece of tissue thats been labelled with a fluorescent probe, and look to see where the fluoresces is coming from,
Which organisms have dorsal nerve cords?
vertebrates
What are glia
the supporting cells of the nervous system
in which region of the brain do glia outnumber neurons 17:1
thalamus
what is the primary role of glia
support the neurons
Which types of glia are found in the CNS
astrocytes, microglia, oligodendocytes, ependmyial cells
which type of glia is the most abundant
astrocytes
what is the function of astrocytes
regulate composition of extracellular fluid, important in proliferation & differentiation of neural stem cells
what do oligodendrocytes and schwann cells do
myelinate axons of neurons (oligo’s do it to many axons and schwann cells do it to a single axon)
what types of glia are found in the PNS
satellite cells and schwann cells
What kind of genetic disease is Huntington’s disease and what gene defect causes it
autosomal dominant disorder & caused by abnormallity in huntingtin gene
what is brainbow
:Genetically modifying an animal so that its cell produce random combos of up to 4 fluorescent dyes so cells will randomly be one of 100 diff colours.
what two types of protein deposits characterise alzheimers
Amyloid beta plaques and tau clumps (which form neurofibrillarly tangles)
List and briefly describe the three main components of the neuronal cytoskeleton.
Microtubules. Polymers of tubulin, 20 nm wide. Role: structure and support. Neurofilaments: 10 nm wide: mechanical strength. Microfilaments: actin polymers 5 nm. Tethered to membrane, mediate shape changes.
what is cerebella ataxias
aberrant movement coordination
what do ions have around them in solution
a hydration shell
what is the effective size of an ion based on
the hydration shell around the ion
what is the size of the hydration shell dependent on
charge density , smaller the ion, higher the charge density so larger the shell
what are some physiologically useful ions
Na+
K+
Cl-
what are some biochemically useful ions
Mg2+ and trace metals e.g Fe3+ & Zn2+)
is Ca2+ biochemically or physiologically important
it is both
what is the primary hydration shell
- the layer of water molecules that immediately contact the ion
do smaller or larger ions of the same size have greater mobility
larger ions do, they have a smaller hydration shell so have a smaller ‘effective’ size
what action do pumps perform
primary active transport
what is antiporting
the exchange of ions in an opposite direction
what is symporting
an ion aiding in transport of another ion in the same direction
give an example of one symporter and one antiporter
symporter- SGLT (Sodium-glucose linked transporter)
Anti-porter- sodium calcium exchanger
what is electrophoresis / electrophoretic movements
ion movement under the influence of an electric field
what is the total gradient equal to
the electrochemical gradient
what is OHMS law (as a word equation)
Current (I) = Volts (V)/ Resistance(R)
Current(I) = Volts (V) x Conductance (1/R)
what does ohms law state
the direction ions move in is determined by the electrochemical gradient
what influences the movement of ions
size of electrochemical gradient
nature of ion
number of open channels
properties of ion channels
what is selectivity in regards to ion channels
only taking specific ions
what is selectivity in regards to ion channels
only taking specific ions
what is permeability in regards to ion channels
degree to which ions are allowed to flow through
what is the conc of Sodium ions in & out of the cell (mM) & what is the ratio
150 outside, 15 inside (10:1 ratio)
what is the conc of potassium ions in & out of the cell (mM) & what is the ratio
5 outside, 100 inside (1:20 ratio)
what is the conc of calcium ions in & out of the cell (mM) & what is the ratio
2 outside, 0.0002 inside (10000:1)
what is the conc of chloride ions in & out of the cell (mM) & what is the ratio
150 outside, 13 inside (11.5:1 ratio)
sodium and calcium both diffuse ____ the cell as both of their conc gradients favour this movement
in to
Potassium and chlorine both have _________ concentration and chemical gradients so it is _________ their movement
opposing
hard to predict
if total work > 0 then ?
energy is needed to move ions across the membrane
if total work < 0 then ?
energy is released when ions move across the membrane
when the nernst equation is in equilibirum, there is no net movement , why?
The electrical gradient exactly balances out the chemical gradient
why is resting membrane potential not the same as EK (equilibirium potential)
Sodium ions can also cross the membrane and this has consequences for Ek , RMP is more positive than equilibrium potential
Because PK (permeability to potassium) is 40x greater than PNa (permeability to sodium, what does this mean for the relationship of of Resting membrane potential and EK
RMP is much closer to EK (equilibirum potential for potassium) than ENa (equilibrium potential for sodium)
what is the GHK (Goldmann-Hodgin-Katz) equation and why is it used
it is a weighted form of the nernst equation and it allows us to calculate resting membrane potential
What is the reason that the resting membrane potential of neurons is close to the equilibrium potential of potassium (EK)?
The resting membrane potential of neurons is close to EK because the membrane is more permeable to potassium ions than any other ion at rest.
What is the primary ion responsible for establishing the resting membrane potential in neurons?
Potassium ions are the primary ion responsible for establishing the resting membrane potential in neurons.
What is the first ion current to activate during an action potential?
The first ion current to activate during an action potential is the inward sodium current (Na).
What ion current is responsible for repolarization of the neuron during an action potential?
The outward potassium current (K) is responsible for repolarization of the neuron during an action potential.
What is the ion current responsible for the hyperpolarizing afterpotential seen after an action potential?
The activation of the potassium current .
you just need to know that its a potassium current
: What is the mechanism by which voltage-gated ion channels open and close?
in the voltage across the membrane, which cause conformational changes in the channel protein.
: What is the mechanism by which voltage-gated ion channels open and close?
in response to changes in the voltage across the membrane, which cause conformational changes in the channel protein.
What is the significance of the selectivity filter in voltage-gated ion channels?
ensures that only ions with the appropriate charge and size can pass through the channel pore.
what kind of structure do voltage gated potassium channels have
tetramers, crystal structure, composed of 4 individual subunits
What is the mechanism of inactivation in voltage-gated sodium channels?
cytoplasmic segment of the channel protein blocks the channel pore.
What is the importance of inactivation in voltage-gated sodium channels for the action potential?
ensures that the sodium current is not forever continuous,
helps contribute to the rising and falling phases of the action potential.
What is the difference between fast and slow inactivation in voltage-gated sodium channels?
Fast = occurs rapidly after the channel opens, slow =over a longer period of time, results in a decrease in channel conductance.
What is the absolute refractory period?
period after a fired action potential in which the neuron requires a greater stimulus to create another (the dip)
What is the relative refractory period?
period during which the neuron can generate another action potential, but only in response to a stronger-than-normal stimulus.
How does the refractory period allow action potentials to spread directionally?
preventing the action potential from re-activating in the region of membrane that has just undergone an action potential. ensures that the action potential can only propagate in one direction, from the initial site of depolarization to the axon terminals
What type of genetic mutation is associated with Dravet Syndrome?
mutations in the SCN1A gene, which encodes the voltage-gated sodium channel **Nav1.1.
What are some examples of epilepsies that have been shown to respond to treatment with cannabinoids?
Dravet Syndrome, and some forms of focal epilepsy.
what changes in ion currents cause the refractory period to occur
due to inactivation of Na current and activation of K current
is transmission within dendrites active or passive
passive
is current attenuated in dendrites or axons
dendrites (due to current leaking out of the cell membrane)
what is length constant dependent on
Rm (inversly proportional to leakiness)
Ri( resistance, want as low as possible)
And diameter
how can the efficiency of transmission through cables be increased
increasing insulation (increases Rm)
having better conductance cores (decreases Ri)
having cables with larger diameters
What are some of the key electrical properties of cables?
Resistance, capacitance, and inductance.
How do axons transmit signals?
through the generation and propagation of action potentials.
What is the length constant?
the distance where the voltage drops to 37% of its original value.
What factors determine the length constant?
Rm (inversely proportional to leakiness), Ri (resistance, we want as low as possible, lower resistance, higher conductivity) and diameter (want large).
How do unmyelinated neurons transmit signals?
via a wave of action potentials that travel along the length of the axon.
How do unmyelinated neurons transmit signals?
via a wave of action potentials that travel along the length of the axon.
How do myelinated neurons transmit signals?
via saltatory conduction, - rapid propagation of action potentials along the myelinated segments of the axon and passive transmission across the non-myelinated segments.
what is density of sodium channels of axons compared to dendrites
(100-200 Na channels per μm/ 2 per μm)
what is special about the axon hillock
v high density of sodium channels
thought to be where action potential started off in the axons
how do we tend to get a bigger length constant in nature
(higher Rm & a larger diameter, NOT better conducting cores)
what is special about the squids giant axon and why is this not suitable for other animals
Increased axonal diameter
no good for animals w/ complex nervous systems - fat heads
Myelination
How does myelination improve the conduction velocity of neurons?
reducing the capacitance and resistance of the axon membrane,
decreases the leak of current and increases the thickness of the insulation around the axon.
What is the relationship between axon diameter and conduction velocity?
Conduction velocity increases with axon diameter.
What is multiple sclerosis?
chronic autoimmune disorder characterised by demyelination of CNS neurons caused by an immune attack on oligodendrocytes that provide myelin sheath
what is the density of sodium channels at internodes
20/μM
what is the density of sodium channels at nodes of ranvier
estimated 1200 sodium channels /μM,
what is saltatory conduction
a wave of action potentials interspersed by segments of rapid cable conduction
How is MS diagnosed?
MRI scanning
Visual evoked potential (VEP) test
What are some treatments for MS?
disease-modifying therapies (DMTs),
Some DMTs are injectable, while others are oral or infused.
What are the pathological mechanisms of multiple sclerosis?
Caused by an immune attack on oligodendrocytes that provide myelin sheath insulation that facilitates saltatory conduction
which neuron fibres have a large diameter(13-20micrometres) and are myelinated whilst conducting fast transmission
A-alpha fibres
Which neuron fibre has a medium diameter (6-12micrometres), is myelinated and conducts intermediate speed transmission
A-Beta fibres
which neuron fibre has a small diameter (1-5 micrometres), a very thin myelin sheath and conducts slow transmission
A-delta fibres
which neuron fibre has a Very small diameter(0.2-1.5 micrometres), NO myelin sheath and conducts very slow conduction
C fibres
What auto-immune disorder is characterised by schwann cells being attacked & the peripheral nervous system neurons becoming demyelinated
Guillain-Barre Syndrome
What is the difficulty in action potentials jumping between neurons?
Action potentials cannot easily jump between neurons due to the synaptic gap.
Is there a direct transmission of action potentials between neurons?
No, action potentials are not directly transmitted between neurons.
what is a gap junction
a structural feature of electrical synapses formed by proteins in the membranes of two neurons docking to each other. It is a 3.5 nanonmetre gap
what are the proteins that form gap junctions called and what are their subunits called
Connexons, made up of 6 connexins
relative to an ion channel, what is the structure of connexons like
bigger than ion channels, big enough for both ions and small molecules (things up to 1000 molecular weight) to be transported between 2 neurons
What do electrical synapses provide between neurons?
Electrical synapses provide a continuous cytoplasmic connection between neurons.
Are electrical synapses fast or slow?
Electrical synapses are fast.
How are neurons connected in electrical synapses?
Neurons are connected by gap junctions in electrical synapses, allowing direct ion flow between them.
are electrical synapses common or uncommon in vertebrate nervous systems
uncommon, used in systems where you need an escape reflex
what is a limitation of gap junctions and electrical synapses
need specialised situations, not very flexible & don’t have as much plasticity as chemical synapses
drosophilia flies have an escape system using electrical synapses
What are the gap junctions in drosophilia flies formed by and what happens to these in the mutant version
Innexins, in the mutant flies, these become disrupted meaning the escape reflex is disabled
What is the main form of communication in a chemical synapse?
through the release of chemical neurotransmitters.
How is the electrical signal transformed in chemical synapses
transformed into chemical signals, which bathe the second neuron and excite an electrical signal in the second neuron.
What is Synaptic Dysfunction
abnormalities or impairments in the communication between neurons at synapses, leading to disruptions in normal neural signalling.
What is Long-Term Potentiation (LTP)
process by which synaptic strength is enhanced, resulting in an increased efficiency of neural communication.
What does excitotoxicity mean?
pathological process in which excessive stimulation of neurons, particularly through the activation of glutamate receptors, leads to cellular damage and neuronal death.
What does channelopathy mean?
(CHANNEL-opathy)
term used to describe a group of disorders that arise from dysfunctional ion channels in cells.
What does synaptopathy mean?
Synaptopathy refers to disorders or conditions characterized by impaired synaptic function.
Outline what astrocytes are and their role.
Astrocytes are a type of glial cell in the central nervous system (CNS) that play diverse roles in supporting neuronal function.
What can cause synaptic dysfunction?
It can result from various factors, such as alterations in neurotransmitter release, impaired receptor function, or structural changes in synapses.
What is LTP a mechanism for?
It is considered a cellular mechanism underlying learning and memory formation. LTP involves the strengthening of existing synapses or the formation of new synapses.
Outline how excitotoxicity can occur.
It can occur in various neurodegenerative diseases and stroke, where excessive glutamate release overwhelms the ability of neurons to maintain ion homeostasis.
What can channelopathies lead to?
abnormalities in the electrical signalling of neurons, muscles, or other tissues, resulting in various clinical manifestations.
Examples include cystic fibrosis, long QT syndrome, and epilepsy
What is the primary way neurons communicate in animal nervous systems?
Neurotransmission (chemical signaling) is the primary way neurons communicate, providing high flexibility and plasticity.
What are some ways in which synaptopathies can be expressed biologically?
abnormalities in neurotransmitter release, synaptic connectivity, or synaptic signalling
Leads to disrupted neural communication.
Who discovered the first neurotransmitter and what was it?
Otto Loewi discovered the first neurotransmitter, which is acetylcholine.
What are some examples of synaptopathies?
autism spectrum disorders, schizophrenia, and Alzheimer’s disease.
What can happen to astrocytes during disease?
undergo reactive gliosis - become hypertrophic, proliferate, and release various inflammatory molecules.
can contribute to neuroinflammation and tissue damage.
what does stimulating the heart via the vagus nerve do?
slows it down
What are microglia and what is their role?
resident immune cells of the CNS and act as the primary mediators of immune responses in the brain.
What can happen to microglia in disease?
can undergo morphological changes, transitioning from a resting state to an amoeboid/phagocytic state.
Become activated & release pro-inflammatory cytokines and can contribute to neuroinflammation.
What can happen to oligodendrocytes in disease?
can be damaged or destroyed, leading to demyelination.
How are natural toxins used in studying synaptic function
by selectively affecting specific components of the synaptic process.
What is neuroinflammation?
inflammation that occurs in the central nervous system (CNS) as a response to injury, infection, or disease.
What does neuroinflammation involve (which cells and what effects can it have on the CNS)?
microglia and astrocytes release inflammatory mediators,
recruitment of immune cells to the affected area
Neuroinflammation can have both protective and detrimental effects on the CNS.
Which diseases are caused by natural toxins that affect synaptic function?
Tetanus/lockjaw and botulism
What can the study of natural toxins teach us about synaptic function?
provide insights into the mechanisms of synaptic transmission and help understand diseases related to synaptic dysfunction.
What is meant by inflammatory mediators?
substances released during neuroinflammation that contribute to the immune response in the CNS.
What is the role of calcium in neurotransmitter release?
Neurotransmitter release is Ca2+-dependent, meaning calcium ions trigger the release of neurotransmitter vesicles.
What does the vesicle hypothesis propose about neurotransmitter release?
neurotransmitter release occurs in discrete packets called quanta or vesicles.
Give some examples of inflammatory mediators. (What can they influence?)
cytokines, chemokines, prostaglandins, and reactive oxygen species.
can influence neuronal function, modulate immune responses, and promote tissue repair or damage.
What is the blood-brain barrier (BBB)?
specialized barrier formed by tight junctions between endothelial cells in brain capillaries.
What can happen to the blood-brain barrier during neuroinflammation?
the integrity can be compromised, allowing immune cells and inflammatory mediators to enter the brain more easily.
BBB dysfunction = associated with pathogenesis of several neurological disorders.
What is the role of the blood-brain barrier?
regulates the exchange of substances between the bloodstream and the brain,
formed by endothelial cells, tight junctions, and specialized transport systems.
How is neurotransmitter release quantal?
it occurs in specific and measurable amounts, corresponding to the release of individual synaptic vesicles.
Outline the relationship between drug delivery and blood-brain barrier.
poses a challenge for delivering drugs to the brain.
tight junctions and efflux transporters limit the passage of many therapeutic agents.
What happens to synaptic vesicles after neurotransmitter release?
Synaptic vesicles are recycled after neurotransmitter release.
How are synaptic vesicles recycled?
Synaptic vesicles undergo endocytosis, where they are retrieved from the plasma membrane and reform inside the neuron.
Why is recycling of synaptic vesicles important?
allows for sustained neurotransmitter release and the replenishment of vesicles for future neuronal signaling.
Outline what can happen as a result of the break down of the blood-brain barrier.
it allows the infiltration of immune cells, inflammatory mediators, and potentially harmful substances into the brain, contributing to further tissue damage and neurological complications.
What is meant by excitable cells?
cells that can generate or propagate action potentials or electrical impulses
Outline the existence of excitable cells in organisms.
commonly associated with neurons and muscle cells,
also exist in plants, bacteria, and single-celled eukaryotes.
Give examples of excitable cells in plants.
guard cells in stomata, which regulate gas exchange,
Venus flytrap, which uses electrical signals to trigger its snapping mechanism.
What snare proteins are important in the release of vesicles
Synaptobrevin -present on the vesicles
SNAP25 -present on nerve terminal membrane
Syntaxin - present on nerve terminal membrane
Synaptotagmin- calcium sensing vesicle protein
what is an evoked release
involves the action potential activating the calcium channels, many vesicles are releasing their neurotransmitters at once, causing a large response . If dealing with muscle, this is called a full end plate potential
what is spontaneous release
release of the neurotransmitters that occurs when there is no action potential and thus no calcium entry
the response is much smaller and a smaller size of change in the membrane potential in the postsynaptic neuron, this is a miniature end plate potential
Give examples of excitable cells in bacteria.
Paramecium:
- Front end has mechanoreceptors linked to Ca2+ channels. (Activation causes ciliary to beat in reverse direction from stimulus - aka swim backwards)
- Back end has mechanoreceptors linked to K+ channels. (Activation leads to faster rate of swimming forwards)
does vesicular release require an action potential
no, spontaneous vesicular release does not require calcium entry or an AP
how is quantal content calculated
end plate potential (evoked release) / the size of 1 quantum current
Outline the evolutionary origins of ion channels.
Potassium channels are probably the earliest members of the family, then calcium channels followed by sodium channels.
Outline the structure of and how cilia move in paramecium.
They move in a wave/whip like co-ordinated fashion.
formed from a 9+2 arrangement (9 pairs outside, 2 in middle) of microtubules termed the axoneme which is stabilised by protein cross-links via the motor protein dynein.
Outline what effect a single gene mutation can have in paramecium
Deficits in locomotor responses.
What is the pawn mutation of paramecium?
Cannot reverse direction - show little or no calcium current (cannot generate action potentials)
What is the dancer variation of paramecium?
Shows an enhanced calcium current - They reverse direction in response to much weaker stimuli than normal cells.
What is the pantophobiac variation of paramecium?
Have reduced voltage gated potassium channel current and show prolonged depolarisation - this means that they swim backwards for much longer than the wild-type.
In laymans terms, they have a lower threshold in order to swim backwards thus swim backwards for longer
What are some evolutionary reasons for rapid movement to be present in plants?
Protection from damage (predation)
Prey capture (venus fly trap)
Spreading pollen and seeds
What does the presence of the ability to produce rapid movement in plants suggest about plants?
There is some kind of sensory system
Fast signal transmission system is present.
There is some kind of mechanism to produce movement.
What is the mimosa pudica? Outline why it is special.
The ‘sensitive plant’ - It is capable of rapid and co-ordinated movement of its leaves (will curl up in response to touch).
What action does the mimosa pudica produce in response touch?
It’s leaves will fold up to expose its thorny stems to predators
What is the mechanism behind mimosa pudicas response to touch?
It is called ‘excitation-turgor loss coupling’
Which is movement brought about a chloride ion-based action potential which leads to cell shrinkage.
