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Flashcards in Electrical Communication_Cell-Cell Deck (59):

What are the two types of graded potentials?

1) Excitatory
2) Inhibitory


What does NMJ contain?

1) Nicotonic ACh Receptor
2) Many other neurotransmitter (GABA, Glutamate, Serotonin)
3) Purinoceptors (need ATP)


What is purinoceptors?

family of plasma membrane molecules that are found in almost all mammalian tissues
originally introduced to illustrate specific classes of membrane receptors that mediate relaxation of gut smooth muscle as a response to the release of ATP (P2 receptors) or adenosine (P1 receptors)


What can graded potential activate?

Activate local voltage gated ion channels
- (Action potential)
- do not typically involve voltage-gated sodium and potassium channels.


Why is graded potential important?

Important in regulating voltage gated channels in other tissues (e.g. voltage gated calcium channels)


What is a graded potential?

- Changes in membrane potential that vary in size, as opposed to being all-or-none.
- They arise from the summation of the individual actions of ligand-gated ion channel proteins, and decrease over time and space.


Where do graded potential occur?

They occur at the postsynaptic dendrite as a result of presynaptic neuron firing and release of neurotransmitter, or may occur in skeletal, smooth, or cardiac muscle in response to nerve input


What is the magnitude of a graded potential determined by?

The magnitude of a graded potential is determined by the strength of the stimulus.


What is the magnitude of a graded potential determined by?

The magnitude of a graded potential is determined by the strength of the stimulus.


What is excitatory postsynaptic potential?

Graded potentials that make the membrane potential less negative or more positive, thus making the postsynaptic cell more likely to have an action potential,


What is EPSP caused by?

EPSPs are caused by the influx of Na+ or Ca2+ from the extracellular space into the neuron or muscle cell.


What is the amplitude of the EPSP directly proportional to?

The amplitude of the EPSP is directly proportional to the number of synaptic vesicles that were released.


What is the amplitude of the EPSP directly proportional to?

The amplitude of the EPSP is directly proportional to the number of synaptic vesicles that were released. The same goes for the amplitude of IPSP


What is the process of triggering the EPSP?

1) When the presynaptic neuron has an action potential, Ca2+ enters the axon terminal via voltage-dependent calcium channels and causes exocytosis of synaptic vesicles, causing neurotransmitter to be released.
2) The transmitter diffuses across the synaptic cleft and activates ligand-gated ion channels that mediate the EPSP.
3) If the EPSP is not large enough to trigger an action potential, the membrane subsequently repolarizes to its resting membrane potential.


What are Inhibitory Post Synaptic Potential (IPSP)?

Graded potentials that make the membrane potential more negative, and make the postsynaptic cell less likely to have an action potential. Hyperpolarization of membranes is caused by influx of Cl− or efflux of K+.


What are the two types of graded potential?



What is the typical resting membrane potential?

usually around –70mV.


What are excitable cell?

Ability to generate and transmit an electrical signal (Action Potential)


What are excitable tissues?

Regions of the body that contribute to transmission of electrical signals


What are the different types of excitable tissues?

1) Sensory Receptors
2) Neuron Cell Bodes (could be found in the Ganglion or in the CNS)
3) Axon
4) Muscles


What are the sensory receptors present in the finger tips?

1) Tactile (meissner's) corpuscle - light touch
2) Tactile (Merkle's) corpuscles - touch
3) Free nerve endings - pain
4) Lameliated (Pacinian) corpuscle - vibration and deep pressure [furthest away from skin surface]
5) Ruffini corpuscle - warmth [2nd furthest away from skin surface]
[1, 2, 3 are all approx. around the same distance away from the skin surface]


What is present in a lot of the membrane of sensory receptors?

A lot of it is loaded with a mechanic gated ion channel


What is activity of a sensory unit altered by?

By peripheral events and then communicates information into the CNS.


Why is there tactile response to the hand?

The receptive field is small therefore therefore it's extremely sensitive and it can distinguish between different responses


What does the afferent neuron axon contain?

1) Central process
2) Neuron cell body
3) Peripheral process


When an object touches the skin, how does the impulse travel to reach the CNS?

Skin -> Respective field -> peripheral terminals with receptors -> Peripheral process -> Neuron cell body -> Central process -> Central terminals -> Central nervous system


What is Channelrhodopsins?

Light gated ion channels
Non specific cation channels (Na+, H+, K+, Ca2+)


What does Channelrhodopsins contain?

Covalently linked light-isomerisable chromophore (Retinal - when the all trans-complex absorbs a photon, it changes shape to a cis-complex and opens the channel)


What is the fiberoptic experiment?

Different light of different wavelength can control different parts of the motor part of the brain. They regulate different ion channel and activates the neuron


How does electrical signal arise?

1) Graded potentials in sensory receptor of afferent neuron - receptor potentials
2) Graded potentials in cell body of efferent - IPSP and EPSP (ACh activated ion channel)


What is non-excitable electrical communication?

Local communication within the cell due to changes in membrane potential
- Secretion
- Cell proliferation
- Cellular differentiation


What is non-excitable electrical communication important in?

1) In normal physiology
2) Crucial for mitochondrial function
3) In tissue responses to injury - Vascular remodelling


What is a classic example of non-excitable electrical communication?

Glucose induced insulin secretion


What does MMP do?

1) Essential for respiration
2) Also implicated in control of apoptosis


What are the two types of diabetes?

Type I - Insulin dependent
Type II - Adult onset


What is the cause of Type II Diabetes?

- Often associated with poor diet
- Decreased sensitivity for insulin
- Decreased insulin secretion
- More susceptible to inflammation - stress the pancreas


Why is MMP essential for respiration?

increase in mitochondrial respiration that was associated with free radicals formation, and which was found to be necessary to prevent the collapse of the mitochondrial membrane potential (Deltapsim) and apoptotic cell death.


What is MMP?

Mitochondrial membrane potential


What happens when there is an increase in plasma glucose?

1) Pancreatic islet beta cells: Increase insulin secretion
2) Increase plasma insulin
3) Adipocytes and Muscle: Increase in glucose uptake
3) Liver: Cessation of glucose output; net glucose uptake
4) Restoration of plasma glucose to normal


Why is the pancreas important?

Need pancreas to respond to glucose level


What are the major classes of potassium channel?

- Voltage gated
- Calcium regulated
- ATP - regulated (Inward rectifiers)


When does calcium regulated potassium channel open?

open in response to the presence of calcium ions or other signalling molecules.
- helps with depolarisation process


What happens in the ATP regulated potassium channel?

passes current (positive charge) more easily in the inward direction (into the cell).


What are voltage gated potassium channel?

are voltage-gated ion channels that open or close in response to changes in the transmembrane voltage.


Where is the ATP regulated potassium channel found?



What is used to workout equilibrium potential?



What is the equilibrium potential of Na+?



What is the equilibrium potential of K+?



What are pancreatic beta cell?

type of cell found in the pancreatic islets of the pancreas. The primary function of a beta cell is to store and release insulin


What is embedded in the membrane of beta cells?

Voltage-gated calcium channels and ATP-sensitive potassium ion channels are embedded in the cell surface membrane of beta cells.


What is the approximate resting membrane potential?

Approx. -70mV


What happens to the pancreatic beta cell at rest?

These ATP-sensitive potassium ion channels are normally open and the calcium ion channels are normally closed. Potassium ions diffuse out of the cell, down their concentration gradient, making the inside of the cell more negative with respect to the outside (as potassium ions carry a positive charge). At rest, this creates a potential difference across the cell surface membrane of -70mV and the membrane is polarised.


What happens to the pancreatic beta cell when blood sugar rises?

Increase in ATP in cell
ATP binds to the ATP sensitive K+ channel
K+ channel closes
Intracellular K+ accumulates
MP depolarises


What happens after potassium ions can no longer diffuse out of the cell?

As a result, the potential difference across the membrane becomes more positive (as potassium ions accumulate inside the cell). - Membrane depolarisation - graded potential
This change in potential difference opens the voltage-gated calcium channels, which allows calcium ions from outside the cell to diffuse in down their concentration gradient.
When the calcium ions enter the cell, they cause vesicles containing insulin to move to, and fuse with, the cell surface membrane, releasing insulin by exocytosis.


What is the treatment of type 2 diabetes?

1) Increase insulin secretion
2) Block potassium channels
3) Sulphonylureas
a) Glibenclamide (a.k.a. Gliburide) - both drugs under the classification of Sulphonylureas
4) Increase insulin sensitivity
a) PPARgamma agonist (Thiazolidinedione)
i) Rosiglitazone, pioglitazone - both drugs


What does Sulphonylureas do?

affect pancreas in insulin secretion


What does Thiaolidinedione do?

affect tissue response to insluin


How does electrical communication happen?

- Depolarisation/hyperopolarisation of cell membrane
- Change in membrane potential (Graded potential)


What does electrical communication have a crucial influence on?

1) Cell function (e.g. insulin secretion)
2) Essentail trigger of AP for rapid long distance signalling