Neurons/Resting Membrane Potential Flashcards
What are neurons?
- Key functional cell in the nervous system
- Cell that is able to generate and propagate an electrical signal
- Distinct shape unlike any other cells
Dendrites
- Receive info (Input)
- Short, branch repeatedly
- Dendritic spines - Similar organelles to the stoma
What part of the neuron is responsible for making (peptide/protein) neurotransmitters?
Cell body (soma)
Cell body (soma) (5)
- Site of normal cellular structures and functions
- Integration on inputs to determine whether info will be sent out (processing)
- Where protein synthesis occurs: includes neurotransmitters
- Contains nucleus
- Organelles: mitochondria, golgi apparatus, endoplasmic reticulum (rough and smooth)
Axon (7)
- Transmission
- Propagates signal/action potential
- Can have up to 100 messages/sec
- All or nothing signals (Either travels all the way down the axon or doesn’t)
- Generally 1/neuron
- May or may not be myelinated
- Contain mitochondria and smooth ER
Axon Pre-synaptic terminals (telodendrion) (4)
- Output
- Branches off the end of the axon
- Contain vesicles of neurotransmitters (made in stoma)
- Axoplasmic transport - Site of neurotransmitter release
Nervous System vs. Endocrine System
- Both control systems
- Nervous system is FAST (message travels quickly) and ADDRESSED (targeted to receptor cell where axon terminal is)
- Nervous System: telephone call
- Endocrine System: radio signaling
Glial Cells (support)
- Component of NS
- NO electrical activity
- Help with neuron function
- Outnumber neurons 10:1
4 Types of Glial Cells
- Astrocyte
- Microglial
- Oligodendricytes
- Schwann cells
Astrocyte
- Help regulate METABOLISM in the neuron (supplies nutrients)
- Go between, between neuron and blood stream
Microglial
-Help with IMMUNE FUNCTION to protect the neurons from damage
Oligodendricytes and Schwann Cells
Both form the myelin sheath (white matter) but Oligo = CNS
Schwann = PNS
Myelin Sheath
- Acts as an insulator to speed things up
- Cells high in fat that WRAP around the axon (Without wrapping, it will NOT act as an insulator)
Resting Membrane Potential
Difference in charge across axon membrane = -65mV
-Normal charge distribution across the membrane
Na+ Membrane Equilibrium Potential
= +58 mV
When Na+ channels open, Na+ flows into the cell until there is a slight positive charge (+58 mV) across the membrane
K+ Membrane Equilibrium Potential
= -80 mV
When K+ channels open, K+ flows out of the cell until there is an even greater negative charge (-80 mV) across the membrane
What part of the neuron is responsible for releasing neurotransmitters?
Axon (Pre-synaptic) Terminal
Which of the following glial cells forms the myelin sheath in the peripheral nervous
system?
Schwann Cells
What is the resting membrane potential of a neuron?
-65mV
. At resting membrane potential, the neuron is more permeable to which ion?
K+
Membrane Equilibrium Potential tells us…
What the membrane potential (charge difference across the membrane) would be if that ion was able to diffuse across the membrane until it reached electrochemical equilibrium (electrical gradient balanced out by concentration gradient)
3 Factors that maintain resting membrane potential:
- Ions must pass through membrane channels or be actively transported
- Different membrane channels are permeable to different ions
- Selective permeability
- Membrane channels may open and close
- Not all channels are necessarily open/closed at the same time
- Different ions can move through the membrane at different times
Maintaining ion concentration differences at rest
Maintained by the Na+/K+-ATPase pump
- 3 Na+ out, 2 K+ in - Neither K+ or Na+ is in electrochemical equilibrium
-SETS UP Charge Difference to CREATE the [ ] gradient
Na+ and K+ can leak through membranes. How fast?
- Na+ leaks in slowly= low membrane permeability
- K+ leaks out slowly = small electrochemical gradient
Cl- can be maintained at relative passive equilibrium
- Due to non-permeating ions
- Donnan equilibrium: chloride is at equilibrium with quite a large concentration gradient because of the highly negative intracellular charge due to the protein (which is a non-permeating ion)
Permeability affects membrane potential:
-Membrane is more permeable to K+ than Na+
Therefore, Vm (resting membrane potential) approximates EK (K+ equilibrium potential)
Depolarized
When membrane potential is MORE (+) than resting potential
-Anything less than -65mV
Hyperpolarized
When membrane potential is MORE (-) than resting potential
-Anything greater than -65mV
50 – 70% of ATP produced in the brain from glucose is used for:
Na+/K+-ATPase pump function
-Must be produced aerobically (O2)
