Lecture 4 (anatomy, cells, resting potential) Flashcards
What are the 3 main parts of the neuron?
- Soma
- Axon
- Terminal
What are the parts of the soma and its function?
- dendrites (receive electrochemical signals)
- spines (^^)
- receptors (on the ends of D&S)
What are the parts of the axon and its function?
- axon hillock
- myelin
- nodes of ranvier
Electrochemical signals move across the axon into the terminal
What are the parts of the terminal and its function?
- Vesicles
- NTs
The ec signal reaches the terminal, then moves through the membrane to the synapse to bind to the next neuron
3 types of glial cells?
- astroglial cells
- oligodendroglial cells
- microglial cells
Astroglial cells –> job? how?
Job: form and maintain the blood brain barrier
How: surrounds blood vessels in the brain, plugs/patches holes
Why is the blood brain barrier important?
Prevents bad things (bacteria, etc.) from getting into the brain. They stay in the blood vessels to get filtered out by the kidneys/liver
Oligodendroglial cells –> job? how?
Job: form and maintain the myelin layer/sheath around the axons of neurons
How: they wrap around, coating the axon
Why is myelin important?
- insulating layer
- Facilitates quicker transmission/communication between neurons
- allows electrical impulses to transmit quickly
- it is interrupted at the nodes of ranvier
Microglial cells –> job? how?
Job: ‘immune system’ or ‘cleaners’ of the brain
eliminate foreign substances OUTSIDE of
neurons (floating in the brain)
How: they form macrophages
Phagocytosis: a cell ingests or engulfs other cells, particles, or bacteria to dispose of them
Why are microglial / macrophages important?
Central role in protecting against infection in the brain
3 states of a neuron:
- Resting
- Excited
- Inhibited
Define propagation:
the movement of signals between neurons
Define resting potential
Electrical charge of the cell when it’s doing nothing
What is the charge? Characteristics of RP?
-70mV
- unequal distribution of ions inside and outside
- inside is MORE NEGATIVE than outside
Ions higher in concentration INSIDE the neuron? (resting)
High concentration of K+
also lots of proteins (A-)**
**proteins cannot move through channels, they’re too big
Ions higher in concentration OUTSIDE the neuron? (resting)
High concentration of:
Na+
Cl-
3 forces responsible for ion distribution?
- concentration gradient
- electrical gradient (electrostatic pressure)
- Na+ / K+ pump
Concentration gradient?
Want the same # of ions inside and outside
Electrical gradient?
Want equal electrical charge inside and outside
Refers to opposite charges attracting each other
Concentration gradient for K+ ?
- some K+ channels are open during resting potentials
- b/c there’s a high concentration of K+ inside, K+ moves OUT
- neuron loses + charges!!
–> becomes more negative
Electrical gradient for K+ ?
- when K+ leaves the cell (due to concent. grad.), cell becomes even more negative
- electrical gradient wants to balance in and out
- elect. grad. pulls K+ back IN
Na+ / K+ pump?
- Na+ leaks in due to elect. grad. wanting more positive charge
- can’t have too much Na+ because the cell needs to be at -70mV to function at RP
- Na+ / K+ pump replaces Na+ for K+
3Na+ OUT –> 2 K+ IN
** it just needs to pump out something positive, its irrelevant why its Na+
** the pump has channels that allow movement for both Na+ and K+ –> most channels only allow movement for 1 ion
What would happen if a toxin blocked the Na+ / K+ pump?
The cell would become too positive, it wouldn’t stay at -70mV, it wouldn’t be able to function at resting potential
Given that there is a higher concentration of Ca++ outside the neuron than inside (at resting potential), how do the chemical and electrical gradients affect it?
- the chemical gradient would pull the Ca++ inside the neuron to have the same number of ions in/out
- this would make the neuron more positive
- the electrical gradient would pull the Ca++ back outside to keep the charge of the neuron at -70mV
