37 - Neurons Flashcards
Neuron
Generate an electrical signal that travels through the axon and releases neuron transmitters to signal other cells
Two Types of Extensions
Dendrites- receive signals from other neurons or the environment.
Axon – sends signals to neurons and muscles.
-Synapse – the end of the axon – where neural transmitters are released to signal between cells
Types of Neurons
Sensory
Interneuron
Motor Neuron
Sensory
Dendrites in sensory organ
Axon transmits signals to the CNS (central nervous system)
Interneuron
Transmit signals between other neurons in the CNS (central nervous system)
Motor Neuron
Signal to produce movement
Dendrites/cell bodies in the CNS
Axons extend to muscles
Resting Membrane Potential (RMP)
Based on an electrochemical gradient across the membrane n-70mV
NA+ Ions higher outside
K+ higher inside
Maintain sodium ion pump
NA+ and K+M channels allow diffusion
K+ doesn’t diffuse often because the outside cell is more positive
Gated Ion channel types
(slide 11)
Open and Close based on a stimulus.
Voltage-Gated – Open and Close based on the charge difference based on the charge difference between the inside and outside of the cell
Ligand Gated – Some kind of molecule (ligand) binds to the channel to open it.
Changes in RMP
Small Changes - Happen all the time. No reaction
Big Changes - Less often but cause action potential (depolarization RMP becomes more positive)
(Slide 12)
Stages of action potential
(Slide 13)
- Resting phase: Both channels closed (K+ & N+ Passive)
- Depoliraztion of the threshold - Voltage=gated channel NA+ opens
- Rising Phase of Action potential - NA+ ion move into the cell - once enough enter leads to a (+) membrane potential / negative (-) outside compared to inside
- Falling phase - Membrane potential OPENS voltage-gated K+ channels and CLOSE voltage-gated NA+ channels
- Undershoot phase - RMP is -> K+ channels close
- Sodium-potassium (NA+/K+) pump gets to work to restore the RMP (NA outside and K inside)
Location of action potential
(Slide 14)
Occurs in Axon of Cell
A wave of potential down Axon
Positive / Negative Charge Flow
In what direction does action potential move down the axon
-Always moves from all body to the axon terminus
-Voltage-gated channels have a refractory period – cannot re-open immediately after closing
How quickly does an action potential move / Schwann cell
(Slide 15)
-it moves very quickly
-in vertebrates, myelin sheath = cellular insulation no extracellular irons have access to the cell membranes
-invertebrates – increased axon diameter increases speed
-Regions without myelin sheath – node of Ranvier or Node
-Myelin sheath – made out of Schwann cell (type of glia)
-Move from one region to the next based on the diffusion of NA+ ions -> increases the membrane potential, to the thresholds -> action potential
Process of Axon terminal releasing NTS
At the axon terminus, release neurotransmitters (NTs) to signal to the next cell.
When an action potential arrives at the anon terminus – it triggers opening voltage-gated CA2+ channels (only at the terminus) (higher outside than inside)
Depolarization opens the voltage-gated CA channels, allowing Ca2+ ions to flow into the cell.
(happens because step 2) Neurotransmitters fuse w/the plasma membrane to release neurotransmitters into the synaptic cleft
Neurotransmitters bind to ligand-gated channels in the next cell (post-synaptic)
The ligand-gated channel opens and lets NA+ (in) and K+ (out), leading to different responses.
Change in membrane potential
Ligand-Gated Channels can be ____ and ______
Inhibitors or Exctritoy
