Nervous system Flashcards
What is communication and a example
- connections between cells
- hormones: centrally secreted, act locally
- second messengers: signal transduction within cells
ex: plasmodesmata, gap junctions
All of these move by…
What is faster?
All move by slow diffusion
Electricity is way faster
How do we communicate with electric signals?
- Communication via electrical signals through nerve cells = neurons
Parts of the neuron
Cell body: has nucleus. Integrates incoming electrical signals
Dendrites: convert chemical signals to electrical signals. Sends towards the cell body
Axon: Conducts electrical signals out the cell body
Both axon and dendrite can do what and form what?
Both axon and dendrite branch out can form networks: electrical signal travel very fast
Networks are for
Network for information flow
Synapses are?
Connections between neurons (axon - dendrite) are called synapses
Explain electrical signal and chemical signals in the neuron?
Electrical signal is interrupted at the synapse: Chemical signals moves between axon terminal and dendrite
Starts a new electrical signal in the next neuron
Membrane potential of neurons is what kind of potential?
What are the charges on the outside and inside of the cell
Electrical potential across the membrane
Outside of cell: more positive charges
Inside of cell: more negative charges
What establishes the electrochemical gradient
NA+/K+ ATPase establishes electrochemical gradient
Explain process for resting potential
K+ leak channel allows K + only to flow along concentration gradient: Membrane potential increases → at equilibrium “Resting potential”
What channel closes? And what happens if it opens? What happens if you close it again
Na+ channel is closed
What happens if it opens? fewer positive charges outside and more positive charges in the inside. Overall voltage increases
Original polarity of the membrane disappears: The membrane is depolarized
If we close the channel again? Everything goes back to normal. The membrane will be repolarized
How the sodium-potassium pump works 8 steps
- Unbound protein
- Sodium binding
- Shape change
- Release
- Unbound protein
- Potassium binding
- Shape Change
- Release
Action potential: What are the three phases:
- Depolarization phase
- Repolarization phase
- Hyperpolarization phase
What causes the opening of the Na+ channel?
- Change in membrane potential
Na+ channel is a voltage gated ion channel
Steps for Na+ entering
Steps:
- Na+ enters axon, attracts negative and repelling positive charges
- Charge spreads: depolarizes
- Downstream voltage-gated channel opens in response to depolarization
The action potential spreads as as wave of what?
Why it doesn’t go backwards
Action potential spreads as a wave of depolarization
Why is it not going backwards: Hyperpolarization leads to a short refractory period
Speed of the action potential…
- speed by which action potential propagates depends on the diameter of the axon
- the large the axon, the faster charges will move
Invertebrates have what?
Examples?
- Invertebrates have large axons
- squids, locust, earthworm
What do vertebrates need?
- Vertebrates need smaller axons
- achieve fast propagation by adding insulation
Axons are surrounded by what?
What does it not have… and this provides what?
- axons are surrounded by sheets of myelin: Schwann cell
- No active ion channels, provides electrical insulation
What are nodes of ranvier?
area in between each Schwann cell
Explain myelination (3 steps to it)
- Myelination prevents ions from leaking out
- Action potentials are regenerated at the next node of Ranvier
- Signals continue to jump down the axon
Axons can be what
At the terminal they connect to…
What is that connection called
Axons can be very long or short
at the terminal, they connect to a dendrite of the next neuron
that connection is called a synapse
