Neuro
NEUR 201: Introduction to Neuroscience
Exam 1 Study Guide
Chapter 2: Cells of the Nervous System
Big Questions (from ppts):
● What kinds of cells reside in the nervous system?
Neurons are the cells that reside in the nervous system
● What is the Neuron Doctrine vs. the Reticular theory? What evidence gave support to the Neuron Doctrine?
The Neuron Doctrine said that the brain was made up of discrete cells that had specialized functions
The Reticular theory said that there were no discrete cells. Golgi staining was a good source of evidence supporting the Neuron Doctrine.
● What are the key structural features of neurons and glial cells? (Compare and contrast to microbes, and to other cells in the body)
● How does the anatomy of neurons support their function of communication?
Having specialized parts (like dendrites) that help to receive signals from other neurons or a cell body to process the information or an axon to transmit electrical impulses.
● What are some different ways to classify neurons?
Number of neurites
Shape
Dendritic spine (presence/absence)
Connections (sensory, motor, inter)
Biochemical properties
More Specific Questions:
How did staining techniques contribute to our understanding of the brain?
It helped us to see a neuron specifically and develop an understanding of the fact that there are discrete cells of the brain
What is Golgi Staining?
Golgi staining is a technique used to dye or give color, in this case, it stains a small percentage of neurons but stains the entirety of one neuron
Who is Cajal, and why was he important?
He was a skilled artist and histologist and he was the one to use Golgi staining to study the brain to make drawings of it
What is the Neuron Doctrine, and how did it vary from the prevailing theory at the time (reticular theory)?
Discrete cells that make up the brain vs continuous neural net
Be able to describe the function and importance of the various parts of the cell, including:
● Nucleus - Double membraned organelle containing DNA
● Rough Endoplasmic Reticulum - The site of protein synthesis and contains ribosomes
● Ribosomes - Responsible for translating mRNA into strings of amino acids (proteins)
● Smooth Endoplasmic Reticulum - Involved in protein folding, regulates calcium concentrations
● Golgi Apparatus - Modifies and packages proteins for distribution to different parts of the cell
● Mitochondria - Powerhouse of the cell, creates ATP (energy) needed to carry out these tasks
Name (and be able to identify) the different parts of a neuron and describe the function of each part. Better yet, be able to draw a neuron and label its parts!
What is the cytoskeleton of the cell? What is it made out of? The cytoskeleton is an internal scaffold and helps to give the membrane its shape, kind of like a backbone
Describe axoplasmic transport. How is Kinesin involved? Material is enclosed in vesicles and carried by Kinesin (it walks it down the microtubules).
Describe the many ways that we can classify neurons.
What are myelin sheaths? What is their function? They are cells that cover and insulate axons, increasing the signal's speed.
Name the two types of glial cells that make up myelin sheaths. What is the difference between these two types of cells (where are they found in the nervous system)?
Oligodendrocytes - they are in the brain and spinal cords
Schwann Cells - myelin in peripheral nerves
What is the general function of astrocytes? Regulates the chemical environment and removes certain neurotransmitters from the synaptic cleft.
What is the general function of microglia? Contains and cleans up sites of injury
Chapter 3: Ions and the resting potential in neurons
“Big Questions” (from ppt)
● Biggest Q: What is the resting membrane potential (RMP), and how do neurons generate it?
The RMP is the voltage difference across a cell’s membrane when the cell is not actively sending signals. It can be generated by an unequal distribution of ions inside and outside the cell.
● What is a membrane potential? The membrane potential is the electrical difference between the inside and outside of the neuron
● What ions are key to neuronal function?
Sodium (Na⁺)
Potassium (K⁺)
Chloride (Cl⁻)
Calcium (Ca²⁺)
● Which part(s) of the cell membrane allows for the passage of ions (and how do they work)? Ion Channels provide a selective pathway for ions to move across the cell membrane. Ion pumps also help with transport too
● What contributes to the movement of ions across the membrane?
Diffusion - movement from a region of higher concentration to regions of lower concentration until equilibrium is achieved.
Electrostatic pressure - Ions are attracted to opposite charges and are repelled by like charges
● When is an ion at electrochemical equilibrium, and how can this be determined? When the concentration gradient is equal and opposite to the electrical force. The Nerst equation can be used to determine this.
● How do equilibrium potentials help us predict the direction of net ion flow? The driving force (Vm - Eion) determines the net movement of an ion:
If Vm is more negative than Eion → Positive ions move in.
If Vm is more positive than Eion → Positive ions move out.
More Specific Questions
What is the resting membrane potential (RMP) of a cell? (Not the specific voltage. Just what is it?) Steady membrane voltage of a neuron when it is at rest
What does it mean for a cell to be polarized? By extension what does it mean for the cell to be depolarized or hyperpolarized? Being polarized is the resting state of a neuron where the inside is more negative than the outside.
Depolarized: Decrease in membrane polarization, the neuron becomes less negative
Hyperpolarization: Increase in membrane polarization, Potential becomes more negative than the resting state
What are ions? What is the name that we use to denote that an ion has a positive charge? What is the name that we use to denote that an ion has a negative charge? Which ions are very important to know in this class (and what are their symbols and charges)?
Ions are charged particles (they have an electrical charge)
Cations: Positively charged ions (Na+, K+, Ca2+)
Anions: Negatively charged ions (Cl-)
Describe the composition and features of the cell membrane.
The cell membrane is made up of a phospholipid bilayer with hydrophilic heads and hydrophobic tails. Ions cannot pass freely (they are not lipid soluble) and requires ion channels to move across the membrane
Describe how ions can pass through the cell membrane.
Ion channels - Allows passive movement of ions
Ion pumps use ATP to actively transport ions
What does it mean when we say that an ion channel is “selective”?
This means that there are channels that allow only specific ions to pass e.g Na+ channels only allow Na+ to pass through.
What does it mean when we say that an ion channel is “gated”? What are some examples of gating stimuli?
Gated channels must be triggered to be opened.
Voltage-gated channels open in response to voltage changes
Ligand-gated channels open when a chemical binds and
Mechanically gated channels open due to physical forces
What does it mean that the cell membrane is selectively permeable?
Some ions are able to pass through if they have the correct permeability and some may not be able to pass through
Describe how diffusion contributes to the flow of ions across a selectively permeable membrane.
Ions move from high to low concentrations due to random motions
Describe how electrostatic pressure contributes to the flow of ions across a selectively permeable membrane. Opposite charged attract while similar charged repels
What is the equilibrium potential? Does this potential change as a consequence of the ratio of a specific ion on the inside vs the outside of the cell? The Nerst equation calculates the Eq potential
What is the Nernst equation and what variables are needed to use it?
Temperature = T, Charge of Ion = Z, Gas constant = R and Faraday constant = F
Eion = RT/ZF ln [Ion]0/[ion]1
Describe the ionic driving force and how that dictates the direction of flow of an ion. The ionic driving force is the difference between the membrane potential and Eion (DF = Vm - Eion). If the Vm is more negative than Eion then the positive ions move in
When the cell is at its resting membrane potential (~ -65 mV), which direction is the driving force (in or out of the neuron) for the net movement of sodium? What about potassium, calcium, and chloride? Why?
● Can you come up with additional thought experiments that compare different membrane potentials to ionic equilibrium potentials, and then predict the direction of flow of the ions?
Driving Force at RMP (~ -65 mV)
• Na⁺: Moves into the neuron.
• K⁺: Moves out of the neuron.
• Ca²⁺: Moves into the neuron.
• Cl⁻: Moves in or stays stable.
What is the sodium-potassium pump? Why is it so important?
Helps to maintain high (Na+) out and high (K+) in
Helps reset ion distributions after an Action Potential
Contributes a small amount (a few mV) to RMP
How does the sodium-potassium pump work? How is it important in maintaining the resting potential?
Pumps 3 Na⁺ out and 2 K⁺ in using ATP.
• Maintains ion gradients crucial for action potentials.
How are astrocytes involved in regulating extracellular K+? What would happen if they didn’t do this (if K+ was too high or too low outside of the cell)?
They prevent an excessive extracellular K+ buildup
If K+ is too high, neurons may become too excitable
Chapter 4: The Action Potential
Big Questions (from ppt): To Be Updated
● What is depolarization vs. hyperpolarization?
Dep: Membrane potential becomes more pos
Hyper: Membrane potential becomes more negative
● How are current, conductance, and driving force related, and how can they help us understand ion flow across the membrane?
Current (Iion): Actual movement of ions.
o Conductance (gion): How easily ions move.
o Driving Force (Vm - Eion): Determines the direction of flow.
● What is an action potential? When does a neuron “decide” to fire an action potential?
If depolarization reaches the threshold (~ -50 mV) at the axon hillock, an action potential is triggered.
● What are the different phases of the action potential? What is happening to cause each phase (current, conductance, driving force)?
Rising Phase: Na⁺ channels open, Na⁺ influx.
o Peak: Na⁺ channels inactivate.
o Falling Phase: K⁺ channels open, K⁺ efflux.
o Undershoot: Excess K⁺ leaves.
o Return to RMP: Na⁺/K⁺ pump restores balance.
● How does the action potential move along the axon? What can speed this up?
Myelin Sheath: Speeds up conduction.
o Axon Diameter: Larger axons conduct faster
More Specific Questions
Describe conductance.
Describe current.
Consider the following formula that we can use to calculate current: Iion = gion (Vm- Eion)
● How are conductance and current related?
● As the membrane potential nears the equilibrium potential, what happens to the current?
● When membrane potential is equal to the equilibrium potential, what happens to the current?
● If there is no conductance, what happens to the current?
What is the action potential? A rapid all or nothing electrical signal
When the membrane potential at the axon hillock reaches the threshold of excitation, what happens in the cell to initiate the action potential?
Label and describe the steps that make up the action potential. Be sure to understand very clearly why the change in voltage is happening during each step (in terms of conductance, current, and driving force). Use the figure below as a guide.
What is the absolute refractory period, and what causes it?
What is the relative refractory period, and what causes it?
What does it mean that action potentials are “all or none”?
Imagine a situation where ENa+ was much higher than it normally is (say, +100 mV versus +62 mV). What effect would that have on the action potential? Why? (Hint: think about the driving force).
What are the Nodes of Ranvier? What happens at these locations?
They are the gaps in myelin where Action potentials regenerate
Describe saltatory conduction.
Action Potentials hump from node to node for faster conduction