Nerve Impulses Flashcards
Neurones
Draw the structure
What carries an impulse to the cell body and what carries it away?
Where are nissl granules found and what do they seem to be?
What do Schwann cells do?
Why are a series of Schwann cells called a myelin sheath?
What do terminal processes do?
Axon to a dendron away Cell body and a concentration of RER Insulate axon from surrounding fluid Because they contain a lot of the lipid myelin Secrete the cells transmitter
Resting potential What is it usually around? What is it? What is it measured with? When does it remain constant? How is it set up and maintained? How do the ions travel?
-70mV
The potential difference between the inside and outside of the axon
Electrodes
When cell is inactive
The different concentration of ions across the axon and how permeable the membrane is to them
Active transport
Describe how repolarisation occurs?
Na in and K out by the NaKATP pump
Opposed by the passive diffusion down conc gradient
Based on permeability to ions
More permeable to k than Na
More k out than Na in
Net loss greater than gain –> polarisation
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Properties of an action potential
Size of stimulus
What has to be reached or gone above to stimulate an AP?
How is depolarisation measured?
What is a local potential,what does it increase with and is it propagated?
What is a threshold and what is it different for?
What is the all or nothing response?
Threshold
By stimulating the neurone and different times with different sized stimuli
Small change, size of stimulus and no
Level that must be reached or gone above to cause AP, different neurones
Once AP caused depolarisation stays the same regardless of the size of the stimulus
Properties of an AP
What are AP propagated by?
What are the series of events that lead to AP?
Does size of the AP change during propagation?
Why does it always travel away?
Nerve impulse
Neurone is depolarised and AP develops in memb
Memb is positively charged
Positive ions attracted to negative adjacent areas
Na chans open and leak causing adjacent areas to become positively charged (depolarised)
AP develops
Original area is repolarised
AP moves to adjacent area
No
Because of the refractory period
Properties of AP
Speed of propagation
What is it determined by?
What 3 things come into this?
How does myelination affect?
How does temperature affect?Structure of the neurone
Diameter or neurone,myelination,temperature
Impulse jumps from node to node,saltatory conduction
Gets energy from respiration, uses enzymes, temp speeds up enzyme activity to a point
Properties of AP
Refractory period
What is this?
What is absolute refractory?
What is relative refractory?A short period after AP when a stimulus will not cause a response
When no stimulus will cause a response
When only a stimulus greater than the original will cause a response
Properties of AP
Frequency of response to stimulus
What does frequency of response allow to be distinguished?
Between stimuli of different magnitudes above the threshold
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
Action potential
What causes an AP?
What is the definition of this?
How does it do this?
What are the sequence of events when an action potential occurs?
Stimulus
A change in the surroundings of the neurolemma
Altering the permeability to Na
Stimulus causes Na chans to open slightly
Na diffuses in potential in memb rises
About -50mV open wide, Na rushes in (depolarisation +45mV)
Na chans close K chans open
K diffuses out loss is great
Potential of memb lower than resting potential
K gate closes
Na/K/ATP K in Na out
Resting potential restored
