Resting Membrane Conditions What is the resting state of a neuron When the nerve cell is not conducting an impulse it is in resting state This makes the membrane of the axon permeable of K ID: 785157
Download The PPT/PDF document "Nerve Impulses Chloe Henry, Delina Tsega..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Nerve Impulses
Chloe Henry, Delina Tsegay
Slide2Resting Membrane Conditions
What is the resting state of a neuron?
When the nerve cell is
not conducting an impulse it is in resting state. This makes the membrane of the axon permeable of K+ and impermeable of Na+Permeable: to allow things to pass through itImpermeable: not allowing things to pass through it The plasma inside the axon contains high amount of K+ ions and outside the axon contains high amount of Na+ This makes the exchange pump able to exchange 3 Na+ with 2 K+ .
Slide3Resting Membrane Conditions
Con’t…
Soon after the outside of the membrane is positively charged and the inside is negatively charged.
The neuron is now in a polarised stateThis electrical potential difference is called the resting potential.
Slide4Resting Membrane Conditions
Slide5Generation of Nerve Impulse
So how does the nerve impulse start anyway?
First the neuron is in resting state, then we apply a stimulus (for example touching something hot) on the polarised membrane.
This makes the membrane’s site permeable to Na+ This enables the Na+ ions to move inside the cell.Causing the outside of the membrane to be negatively charged and the inside positive Now the neuron is in the depolarized state.
Slide6Generation of a Nerve Impulse
What kind of protein channels are in the neuron?
Ion channels in the membrane are
selective, only allowing certain things to pass through. Only allowing ions of appropriate size and charge to pass throughSo only Na+ can go through sodium pumps and K+ through potassium pumps. These channels are not continuously open but are gated, which allows them to open and close quickly.Like when depolarization occurs.
Slide7Generation of Nerve Impulse
Slide8Generation of Nerve Impulse
Video:
https://www.youtube.com/watch?v=jcZLtH-Uv8M
Slide9Conduction of a Nerve Impulse
How does the energy go throughout the neuron?
When a neuron sends info. Down the axon away from the cell body this is the
action potential.This electrical current is created by a depolarization currentAfter depolarization Na+ channels are closed and K+ channels openWhen permeability is back to its original state K+ channels close.This all happens in a millisecond!Repolarization is when the neuron changes back into its negative state.
Slide10Conduction of a Nerve Impulse
Slide11Conduction of a Nerve Impulse
What is the all or none principle?
When depolarization hits
threshold (when the impulse reaches the action potential) you cannot stop the current.For any sized neuron the action potential is fired at the same intensity.It either sends the signal completely or not at all.
Slide12Conduction of a Nerve Impulse
What are the purposes of the myelin sheath?
Myelin is a plasma membrane around the nerve axon, this insulates the electrical current.
Outgrowth of a glial cell⅔ of all axons are not myelinated, which these axons only go 2 mph.While myelinated axons go 7 times more faster
Slide13Conduction of a Nerve Impulse
Video:
https://www.youtube.com/watch?v=ifD1YG07fB8
Slide14From One Neuron to Another
How does the current go from cell to cell?
When the action potentials electrical current reaches the end of the axon the axon releases neurotransmitters that go across the synapse unto the next cell.
An axon is the long part of the neuron that conduct impulses.It is like an electrical cable, the larger it is the more currency.Neurotransmitters are chemical messengers that enable neurotransmission.
Slide15From One Neuron to Another
So, how do neurotransmitters work?
They are found at the end of axon endings. They are a chemical that stimulates impulses unto the neurons or muscle fibers.
Some of these neurotransmitters are acetylcholine (ACH), dopamine, serotonin and endorphin.All these NTs have different effects on the body and brain.
Slide16From One Neuron to Another
What are the different kinds of synapses?
Chemical Synapses:
Neuromuscular Junction: Between a motor neuron and muscle cell, most commonly used and allows neurons to form interconnected neural circuits.Electrical Synapses:These are rare, it only occurs when the membranes of two communicating neurons come extremely close at the synapses and linked to a gap junction.Gap Junction: contain aligned channels in the postsynaptic membrane.
Slide17From One Neuron to Another
Slide18From One Neuron to Another
Video:
https://www.youtube.com/watch?v=f-88OtK_iUk
Slide19Sources
https://faculty.washington.edu/chudler/ap.html
https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/the-membrane-potential
http://byjus.com/biology/neurons-nerve-impulses/ https://www.ncbi.nlm.nih.gov/books/NBK26910/https://www.ck12.org/book/CK-12-Life-Science-Concepts-For-Middle-School/section/11.41/