Cellular Neuroscience Flashcards
Definition: Functional unit of the nervous system
Neurons
The input part of a neuron?
The dendrites
The output part of a neuron?
The axon
The part of the neuron that holds the nucleus, DNA, and life support?
The cell body
What does the axon exit on the cell body?
The axon hillock
Where presynaptic axon terminals and postsynaptic dendrites meet
The synapse
What are the finger-like projections dendrites sometimes have?
Dendritic spins
the highly plastic structure (during development) that acts as a highway for molecular motors inside neurons?
The cytoskeleton
Who invented and used the cell staining method.
Camillo Golgi invented it
S. Ramon Y Cajal used the technique
The two theories Cajal and Golgi had on neurons?
Reticulum theory (physically connected) - Golgi Cell Theory (individual cells communicating) - Cajal
The ratio of glia to neurons?
3:1
What is special about glial cells
they can divide throughout their entire lifetime
Name the three types of glial cells:
Astroglia
Oligodendroglia
Microglia
Describe some functions of astroglial cells:
Prevents leaking of chemical activity by insulating and isolating neurons from each other
- Blood-brain barrier
- A border that protects the brain from parasites from blood
- Surround blood vessels, and absorb nutrients to give to brain
- Can act as stem cells
Describe some functions of oligodendroglial cells:
- Produces myelin in the CNS
- Wraps neurons to speed up conduction
- Can also supply neurons with fuel (LACTATE) after forming myelin by absorbing nutrients from blood vessels and releasing it to the neurons.
- Can act as stem cells
Describe some functions of microglial cells:
- Immune cell, because CNS is immunologically privileged due to BBB, fewer immunological defenses than other body areas as normal immune cells are unable to move freely around NS
What type of glial cell is star-shaped?
astroglial cells
What is one theory of ALS relating to oligodendroglial cells?
The oligodendroglial cells malfunction and cannot provide enough nutrients to motor neurons with long axons. Results in loss of voluntary movement
How many synapses are astrocytes capable of interacting with at once?
Around 2 million
Where are the glial cells astrocytes located in the brain?
Located near ventricles in the subventricular zone, next to ventricular zone blood vessels
How many myelin wrappings can one oliogodendroglia cell provide?
30-50 myelin internodes
What is the difference between oliogodendrocytes and schwaan cells?
Schwaan cells can only provide one myelin wrapping per cell, however, oliogodendrocytes can provide 30-50 myeline internodes per cell
What type of matter are oliogodendrocutes usually found in? What state are they in in this matter?
White matter as oliogodendrocyte precursors, polydendrocytes
What do polydendrocytes produce?
mostly oliogodendrocytes, some astrocytes
What causes chromic inflammation diseases?
too much inflammation
the electrical difference between the outside and the inside compartments; the electrical potential generated across the membrane at electrochemical equilibrium
The equilibrium potential
he exact balance between the concentration gradient and the opposing electrical gradient
the electrochemical equilibrium
_________ discovered the large neurons squids have after opening one up at University College London
John Young
The Na+ channels are an example of a _______ feedback circuit that is ________
positive feedback circuit that is fast and self-limiting
The K+ channels are an example of a ____ feedback circuit that is ______
negative feedback circuit that is slow and gradual
A measurable rate of propagation
conduction velocity
2 ways to increase conduction velocity
1) Make the diameter of the axon bigger
2) Insulate the axon so the message doesn’t leak out, then leave gaps for the message to jump across,
What is found during the post-mortem of somebody that had MS?
The post-mortem exam reveals loss of myelin associated with the infiltration of inflammatory cells. Sometimes entire axons are missing
One of the problems that can arise from demyelinated and inflammation of axonal pathways
Generated when there are differences in the concentrations of specific ions
electrical potentials
Arise from ion changes due to the selectively permeable nerve cell membranes with ion channels, and the distribution of certain ions due to active transporter proteins
Electronic signals
_____________an exact balance between two opposing forces, ______ and _______, so there is no net ion flow
electrochemical equilibrium
exact balance between the concentration gradient and the opposing electrical gradient
_______ is where action potentials originate
the axon hillock
why do action potentials originate from the axon hillock?
the axon hillock has the highest concentrations of K+ and Na+ channels
The electrical difference between the outside and the inside compartments
the equilibrium potential
the electrical potential generated across the membrane at electrochemical equilibrium
the equilibrium potential
Why are the concentrations of K+ and Na+ on either side of the axonal membrane generally not affected during an action potential?
the % of Na+ and K+ ions that actually move across the membrane during an action potential is very small, but still creates big changes (axon potential) across teh membrane
Where are Na+ voltage-gated channels found on the axon?
On the nodes of Raviner
What is whole-cell recording? (patch clamp method)
the membrane patch within the pipette is disrupted by briefly applying strong suction, so the pipette becomes continuous with the cell cytoplasm.
What is Inside-out patch recording configuration? (patch clamp method)
A tight seal is formed between the membrane and the glass pipette and small pieces of the membrane can be pulled away from the cell without disrupting the seal the pipette has on the cell.Briefly exposing the tip of the pipette to the air allos the vesicle to open and yield a small patch of membrane with its intracellular surface exposed. This allows the change of medium to which the intracellular surface of the membrane is exposed. (helpful when studying the influences of intracellular molecules on ion channel function.
Outside-out recording configuration
The pipette is retracted while it is in the whole-cell configuration, and a membrane patch is produced with its extracellular surface exposed. This method is optimal for studying how channel activity is influenced by extracellular chemical signals such as neurotransmitters.
Microscopic currents:
Microscopic currents: Currents flowing through single channels
Macroscopic currents:
currents flowing through a large number of channels distributed over a larger region of surface membrane
define “subunits” of ion channels
Helical membrane-spanning protein subunits that each cross the plasma membrane twice
how many subunits for a K+ channel
4 subunits
how many pore loops form a channel pore in a K+ ion channel?
4 pore loops form a pore
How does the K+ ion channel selectively take in K+ ions
: The narrowest part of the pore (near the outside
the mouth of the channel) is so constructed that
only a non-hydrated K+ ion can fit through the
Bottleneck. Called the selectivity filter (Larger
cations are too large and smaller cations
cannot enter as the pore “walls” are too far
apart to stabilize the small ion)
what is the purpose of the water-filled cavity in the K+ ion channel
This cavity takes K+ ions from the cytoplasm
What is the purpose of the 4 binding sites in the K+ channel
The potential presence of 4 K+ ions in the selectivity filter binding sites causes electrostatic repulsion between the ions and speeds up their travel. This makes ion flow through the channel so fast
What are the structural differences between K+ ion channels and voltage-gated K+ channels?
Has additional structures on cytoplasmic side
Regulatory β subunit linked to channel by T1 domain
Four additional transmembrane structures that form the voltage sensors
When the membrane becomes depolarized, what happens to the voltage sensors on a K+ voltage-gated channel?
They are pushes outwards as inside fo the cell isn’t as negative and isn’t pulling the sensors toward the inside anymore
When the membrane becomes hyperpolarized, what happens to the voltage sensors on a K+ voltage-gated channel?
They are pulled inwards, as the negative charge inside the neuron attracts the positively charged sensors more as the negativity grows
Are receptors more or less selective than voltage-gated channels (usually)?
less selective
what membrane proteins are sensitive to chemical signals arising within cytoplasm of neurons?
Ligand-gated channels with ligand binding domains on intracellular surfaces
What do Ligand-gated channels with ligand binding domains on intracellular surfaces do?
They turn chemical signals into electrical info
What do Ligand-gated channels with ligand binding domains on intracellular surfaces interact with? specifically?
Interact with second messengers such as:
- Ca 2+
- The cyclic nucleotides cAMP or cGMP
- Protons
membrane proteins that contribute to sensations of pain and body temperature
thermosensitive protein channels
Other than strictly cold and heat, what are thermosensitive channels responsive to?
Unique mechanism based on temperature-dependent displacement of membrane lipids
Heat and spice channel and chemical?
Ex: TRP channel
Responds to temperatures above 40 degree C, but also to capsaicin
(makes chili peppers spicy)
channels that are critical components of stretch receptors and neuromuscular stretch reflexes
mechanosensitive channels
a specialized form of what channel enables hearing by allowing auditory hair cells to respond to sound waves
mechanosensitive channels
Possess a central pore but have extracellular blade structures that act like levers to open the channel when they are mechanically stimulated
mechanosensitive channels
what general channel type restores ions displace during the current flow (that occurs as a result of both neural signaling and the continual leakage if ions that occurs even at rest)
active transport channels
what do active channels store energy as?
ion concentration gradients
The two general active transport channel types?
ATPase Pumps
Ion Exchangers
Why do active transport channels require energy?
Must consume energy as they transport ions against their electrochemical gradients
What do ATPase channels get their energy from?
Get their energy from the hydrolysis of ATP
What is the active Na+/ K+ channel made of?
A large protein containing two subunits:
- a - b
What is the subunit a of the Na+/K+ active channel do?
responsible ion translocation and spans the membrane 10 times
What is the subunit b of the Na+/K+ active channel do?
spans the membrane once, predominantly extracellular
Na+ pump accounts for up to ____ of the brain’s total energy consumption
2/3
Further studies showed Na+ and K+ were not pumped at the same rate: ________________________
→ 2K+ enter for every 3Na+ removed
describe the fueling of the Na+/K+ pump by ATP. What that energy promotes?
Fueled by binding of ATP and transfer of the phosphate group from ATP to the pump
ATP binding promotes binding of intracellular Na+ and the release of K+, while pump phosphorylation leads to extracellular release of Na+ and binding of K+
In between the two states of ion translocation are states that prevent leakage of ions in the reverse direction, with subsequent hydrolysis of ATP leading to the dissociation of ADP. This switches the pump between taking in intracellular K+ and removing intracellular Na+
what do ion exchangers use as their energy store? How many ions can they carry at once? What directions do they go in?
Uses the electrochemical gradients of other ions as an energy source
Carry one or more ions up their electrochemical gradient while, at the same time, taking another ion down its gradient
What do antiporters (ion exchanger) do?
Antiporters: exchange intracellular and extracellular ions
What do co-transporters (ion exchanger) do?
Co-transporters: Carries multiple ions in the same direction
What are the two kinds of ion exchangers?
antiporters and co-transporters
