Flashcards in Action Potential Deck (19):
Action Potential is a nerve impulse which travels along a neuron.
What does the cell membrane contain ?
They contain thousands of molecules known as channels.
What do the channels allow ?
They allow sodium and potassium ions to pass through
Potassium ions channels close more slowly than sodium channels.
Excess potassium ions diffuse out of the neuron
Potential difference becomes more negative than the resting potential difference - 70 mv .
Hyperpolarization are more negative than -60 mv and -70 mv .Unable to conduct a nerve impulse set to fall in the refractive period .
Describe the changes in membrane permeability at point 1 which is the resting potential going into depolarization
The sodium channels open
Axon cells become more permeable to sodium ions
Sodium ions exist the across membrane
Diffusion of sodium ions into nerve cells
More positive ions outside the neuron this comes after resting potential .
Na + gates open
Na+ diffuses into the cell carrying a positive charge
Na+ gates close
The membrane becomes depolarised causing thresholds.
This is where an action potential is triggered
If the stimulus is large enough it will reach a threshold rest of the sodium gated channels open allowing rapid diffusion and sodium ions into the axon and charged .
Occurs after depolarisation
Closure of the sodium gates
K+ gates open
K + diffuses out of the cell taking positive charge with it .
Na+ channels close
Inside the axons is more negative and positive outside.
Short period where the sodium potassium pump continues to return sodium to outside and potassium ions inside .
At the end and beginning where at the end the equilibrium is restored .
Neurone is not transmitting a action potential and is at rest .
At rest the sodium ion channels in the membrane are closed and the sodium potassium pump is used to transport the sodium and potassium across the membrane creating a potential difference -60mv
Speed of action potential in human
The speed of nerve impulse travels in human is 1 to 3m/s in unmyelinated fibres and 3 to 120 m/s in myelinated fibres
What does the speed of the travel depend on ?
Axon diameter :The larger the axon the faster the conduction .
Myelinated of neuron: The nerve impulse travels faster if the neuron is myelinated
Number of synapses involved : The fewer synapses there are to cross the faster the communication
How is a action potential generated ?
Stimulated by a receptor cell or another neurone an action potential is generated .
Is a electrical potential which results from the process of ions moving across the neurone cell membrane when the correct channels are open in response to a stimulus causing the inside of the neurone to be + than outside _
Happens only in myelinated nerves and it creates the increased the of the action potential.
It can depolarise is at the nodes of Ranvier where there is no myelin . This means that the nerve impulses can travel faster than without myelin and the impulses jumps from one node to the next .
What is the process for Salutory conduction ?
Process of signal jumping .
When the action potential reaches a node of Ranvier sodium ions diffuse into the axon membrane
Displace a potassium ions down the axon because they are positively charged and the charges repel .
Causes the movement of the potassium to node further down the axon makes the next node more positive and depalsies it until the threshold Is reached .
Impulses quickly jumps from node to node making the action potential quicker .
only a small part of the axon is being used so less atp is needed and fewer ions are being exchanged .
Occurs when a stimulus is detected the cell membrane is excited and becomes more permeable allowing ions to move in and out of the cell .
Changes in potential difference due to stimulus .
Big- Excites the membrane more causing a bigger movement of ions and a bigger change in potential difference
Describe the structure of myelinated neurone
Fatty white substances that surrounds the axon of some nerve cells forming an electrically insulating layer
In which has a function to protect and insulate these axons and enhance their transmission of electrical impulses .
Why can the neurone get excite straight away after the action potential ?
It is because some voltage gained potassium channels remain open leading potassium out of the cell leading to the voltage in falling .This is known as hyperpolsiation