Lecture: Neurophysiology Flashcards
What is the analogy to remember for the semipermeable membrane
A screen door
Diffusion causes ions to flow from areas of ____ to ____ concentration, along their concentration gradient.
High to low
the difference in the concentration of a substance between two areas.
Concentration gradient
Like charges (repel/attract)
Repel
Opposite charges (repel/attract)
Attract
What is the process if particles moving down their concentration gradient called?
Diffusion
the force that results from the repulsion or attraction of charged particles
Electrostatic pressure
What is the term for electrostatic pressure causing ions to flow towards oppositely charged areas
Electrical gradient
What makes neurons similar to batteries?
They store charge to use when needed
The inside of a neuron is more (negative/positive) than the outside
Negative
The outside of a neuron is more (negative/positive) than the inside
Positive
What structure is the key to how diffusion works in a neuron?
The cell membrane
What is the neuron cell membrane composed of?
a lipid bilayer and membrane proteins
Proteins spanning the membrane so ions can pass in and out
Ion channels
In which order did the methods of opening/closing gated channels evolve?
Mechanical action
Chemicals
Voltage changes
Why do membranes need ion channels?
The neuronal cell membrane repels water, and ions are surrounded in water, so they can only enter the cell through a channel
What are the three states ion channels can be in?
open
closed and unlocked
closed and locked
Are neuronal membranes permeable to large negatively charged proteins?
No
Where are the large negatively charged proteins inside the neuron created?
Inside the cell
What makes the inside of a neuron negative?
Large negatively charged proteins that cannot leave
Which ion is the only one able to enter and leave the cell freely?
K+
(Potassium)
What do K+ ions do when the neuron is at rest?
Move into the negative interior
Why do K+ ions move into the negative interior of the neuron when it is at rest?
Electrostatic pressure
When does K+ reach equilibrium for a neuron?
When ion movement out is balanced by ion movement in
What happens during depolarization of a neuron
The charge of the cell moves closer to zero, or closer to neutral
What is the voltage of the resting membrane potential?
-60 mV
What pushes K+ ions out vs in when the cell is at rest
Concentration gradient pushes the ions out once they build up
Electrostatic pressure from negative charged proteins inside keep pulling them in
True or false?
Neuron membranes are slightly permeable to sodium ions (Na+), so they slowly leak in.
True
What dies the Sodium Potassium pump do?
Pump Na+ out of the cell and K+ into the cell
What is the charge result of each time the Sodium Potassium pump functions?
3 Na+ are pumped out of the cell, resulting in a negative 3 charge, while 2 K+ are brough inside, resulting in a positive 2 charge
What is the purpose for the Sodium-potassium pump?
Maintain resting potentialq
What is the analogy to remember for the Sodium-Potassium pump?
Yacht fills up with water that has to be pumped out at the same rate
What percent of energy in the brain is used to run the sodium-potassium pump?
40%
Are there more Na+ ions inside or outside the neuron when at rest?
Outside
Are there more K+ ions inside or outside the neuron when at rest?
Inside
Are there more Cl- ions inside or outside the neuron when at rest?
Outside
Are there more Ca2+ ions inside or outside the neuron when at rest?
Outside
Are there more negative proteins inside or outside the neuron when at rest?
Inside
Why are there more Ca2+ ions outside the neuron than inside?
Although they are attracted to come in, the membrane is not permeable to Ca2+
Where does Tetrodotoxin come from?
Eating Fugu which contains pufferfish
What does Tetrodotoxin do?
Blocks voltage-gated sodium channels in the neuron membrane
What chemical blocks nerve action by binding to pores of voltage-gated sodium channels in the neuron membrane?
Tetrodotoxin
What is the result of Tetrodotoxin blocking nerve action?
Paralysis, leads to stop breathing and death without medical intervention
Where does the action potential start?
Axon Hillock
Where do graded potentials occur?
Dendrites
small changes in the electrical charge of a cell membrane caused by stimuli, occurring at the dendrites
Graded potentials
True or false?
Graded potentials always cause action potentials
False, only if they are strong enough
True or false?
If a graded potential is strong enough, it will trigger an action potential
True
What causes graded potentials?
Sensory input or neurotransmitters released at synapses coming into dendrites
What voltage triggers an action potential?
-40 mV
What is the analogy to remember for graded potentials spreading across the membrane?
Ripples in a pond diminishing as they spread out
If the membrane reaches ____ after graded potentials, it triggers an action potential
Threshold
What happens to the charge of the inside of the cell during an action potential?
It becomes briefly possible
True or false?
An action potential sweeps down the axon to its end
True
a change in membrane potential that occurs below the threshold needed to trigger an action potential
Subthreshold potentials
small electrical potential change that occurs in the membrane potential of a neuron after the main action potential has peaked and started to repolarize, often characterized by a brief period of hyperpolarization
Afterpotential
True or false?
Neurons fire at full amplitude or not at all.
True
What is the source of action potentials?
Na+ ions
What happens at the synapses?
Electrical signals are converted to chemical signals, send from the axon terminals of the presynaptic neuron to the dendric spines of the postsynaptic neuron
What are the two types of ion channels?
Leakage channels
gated channels
What is the period in a neuron where no more action potentials can be produced?
Absolute refractory phase (AR)
What is the period in a neuron where only strong stimulation can produce an action potential?
Relative refractory phase (RR)
Is the absolute refractory phase long or short?
Short
What does the inactivation gate on Na+ channels do during the absolute refractory phase?
It locks
During which phase of the action potential is the absolute refractory phase?
When Na+ ions finish flowing in
During which phase of the action potential is the relative refractory phase?
As K+ ions are leaving the cell
What happens when the inactivation gate gets stuck in the Na+ channel?
It can no longer produce action potentials
True or false?
Without nodes of Ranvier the cell would be useless.
True
What is located in the nodes of Ranvier?
Na+ ion channels
In what direction do the nodes of Ranvier unlock in a neuron?
Left to right (along the axon towards terminals)
Would conduction be faster along an unmyelinated axon or a myelinated one?
Myelinated
Would conduction cost more energy along an unmyelinated axon or a myelinated one?
unmyelinated
True or false?
The electrical signal during an action potential is converted to a chemical one, then back to an electrical one at every synapse.
True
The action potential travels down the axon to the ____ ____
Axon terminal
Does the action potential slow down or remain at full speed as it reaches the terminal?
Slow down
How does the axon terminal slow down when it reaches the axon terminal?
There are no more voltage-gated sodium ion channels
What is the single goal of the action potential in a neuron?
To cause enough depolarization to trigger calcium channels to open
Why do calcium ions rush in when their gated channels open?
because they are positively charged and to balance their concentration gradient
What does calcium signal once it enters the cell?
It signals synaptic vesicles to migrate and fuse with the membrane
What happens when synaptic vesicles fuse to the neuron membrane?
neurotransmitters are released into the synaptic cleft
What are the two possible outcomes of neurotransmitters binding to postsynaptic receptors?
EPSP or IPSP
What does EPSP stand for?
Excitatory postsynaptic potential
What does IPSP stand for?
Inhibitory postsynaptic potential
Excitatory postsynaptic potentials (EPSP) lead to small local depolarizations/hyperpolarizations
depolarizations
Inhibitory postsynaptic potentials (IPSP) lead to small local depolarizations/hyperpolarizations
hyperpolarizations
What does depolarization mean?
Pushes cell closer to the threshold, less polarized
What does hyperpolarization mean?
Pushes cell away from threshold, more polarized
What does an excitatory postsynaptic potential result from?
Sodium ions entering the cell
What is the result on the cell charge of sodium ions entering?
It becomes more positive
What does inhibitory postsynaptic potential result from?
Chloride ions entering the cell
What is the result on the cell charge of chloride ions entering?
It becomes more negative
Which neurotransmitter opens chloride channels?
Serotonin
Is chloride pulled into the cell due to the electrical gradient?
no, it is negative like the inside of the cell
Is chloride pulled into the cell due to the concentration gradient?
Yes
True or false?
Chloride is pulled into the cell due to the electrical and concentration gradient.
False, only concentration because both the ion and the inside of the cell are negative
Where are EPSPs and IPSPs integrated?
Axon hillock
True or false?
The cell fires when the total charge from all the inputs if EPSPs and IPSPs averages to -40mV
True
True or false?
There could be thousands of channels integrated by the axon hillock
True
True or False?
Dendrites vote and the axon hillock decides whether or not the cell should fire.
True
Neurotransmitters may go back and bind to ____ ____.
Presynaptic autoreceptors
What is the role of autoreceptors on the presynaptic neuron?
It can tell the rate at which the neuron is firing
True or false?
Autoreceptors may slow the rate of the presynaptic neuron firing neurotransmitters.
True
Once a neurotransmitter binds to the presynaptic autoreceptor it is ____
Inactivated
What are the two ways to inactivate neurotransmitters from the synapse?
- Degradation (destroy them)
- Reuptake
What happens to the neurotransmitter after it binds to receptors in the postysynaptic neuron and opens ion gates?
It is released back to the synapse.
When treating depression, do you want to speed up or slow down the rate of firing neurotransmitters?
Speed up
True or false?
SSRI’s block the reuptake of serotonin, allowing for the neurotransmitter to bind more times
True
What eventually happens to a neurotransmitter if it is not taken back up or destoryed?
It floats away from the synapse
What facilitates neurotransmitter degredation?
Enzymes that break down/inactivate the neurotransmitters
What degradation enzyme is stopped with raid (Spray to kill bugs)
Acetylcholinesterase (AChE)
What does AChE stand for?
Acetylcholinesterase
What does Ach stand for?
Acetylcholine
What is acetylcholine?
Neurotransmitter
What is acetylcholinesterase?
Enzyme that inactivates acetylcholine
Can acetylcholine be reutaken?
No
What happens when acetylcholinesterase is destroyed in bugs?
It continues to bind, causing twitching until the bug eventually dies of suffocation
Where do electrical synapses exist?
In the heart
Which type of synapse requires no chemical intermediator (chemical messengers or neurotransmitters)
Electrical synapse
What do electrical synapse allow?
Ions flow directly through large channels into adjacent neurons
Is there a time delay in electrical synapses?
no
What are the 3 benefits of electrical synapses?
- Faster
- Allows neurons to synchronize
- saves energy
Why was Golgi technically right after all?
Electrical synapses exist
Are there electrical synapse in the brain?
No
Why would electrical synapse not work in the brain?
It acts as one single neuron, and the brain needs more than that to execute all of its functions?
Why do electrical synapse work in the heart?
It has one function
How might electrical synapse occur in regions of the brain?
trauma or damage
Did chemical or electrical synapse evolve first?
Electrical because they are easier
What does ligand mean?
Molecule/chemical
What is the analogy for ligands?
Lock and key
True or False?
Ligands fit receptors to activate or block them
True
Where do ligands come from?
Either made in the body or ingested chemicals
Endogenous ligands
Neurotransmitters and hormones
Exogenous ligands
Drugs and toxins from outside the body
True or False?
Acetylcholine is a ligand
True
What is the main job of acetylcholine receptors?
Main job is activating muscle cells
What disease results in the failure of acetylcholine receptors?
Alzheimer’s
True or false?
The number of receptors in a neuron remain constant?
False
What causes the number of receptors in a neuron to vary? (3 ways)
- Development
- learning
- drug use
True or false?
The nervous system is designed to change due to learning and memory.
True
Up-regulation
an increase in the number of receptors on a neuron
Sensitization
an increase in the number of receptors on a neuron
What is a synonym for up-regulation?
Sensitization
What common drug causes up-regulation/ sensitization
Nicotine
Down-regulation
a decrease in the number of receptors on a neuron
Tolerance
a decrease in the number of receptors on a neuron
What is a synonym for down-regulation?
Tolerance
What common drugs cause down-regulation?
benzodiazepines and valium
what is the result of down-regulation/tolerance
you have to take more of the drug to have the same effect
True or false?
Down-regulation/tolerance is always permanent
False
usually temporary but can be permanent
What device records brain activity?
Electroencephalogram (EEG)
What does EEG stand for?
Electroencephalogram
What type of seizure involves both stiffening and twitching or jerking phases of muscle activity?
Tonic-clonic seizures
What is the term for stiffening in regard to seizures?
Tonic
What is the term for twitching/jerking in regard to seizures?
Clonic
What is the analogy to remember for tonic-clonic seizures?
running at full speeds, then beginning to run out of breath so alternating between running, walking
Why are EEGs recording brain activity during seizures useful?
They can determine which region of the brain is causing it and whether or not it can be removed
What is the name of the process used to determine which region of the brain is causing seizures and whether or not it can be removed
Seizure surgery evaluation
What are tonic-clonic seizures followed by?
Confusion and sleep
True or false?
The whole body convulses during tonic-clonic seizures
True
What type of seizure consists of an individual stopping for a short second, unaware but no jerking or convulsing?
Absence
Can individuals stand during absence seizures?
Yes
What happens after absence seizures?
person usually returns to what they were doing before the seizure and is able to think clearly.
What do brain waves show for tonic-clonic seizures
abnormal activity throughout the brain
What type of seizure is characterized by generalized convulsions?
Tonic-clonic seizures
What do brain waves show for absence seizures?
generalized rhythmic activity for any a few seconds
How often do absence seizures typically occur?
Hundreds of times a day
How long to absence seizures typically last?
a few secondsD
During which type of seizure do individuals have no unusual muscle activity but instead stop and stare?
Absence
What is the analogy to remember for absence seizures?
Light switch
Why do absence seizures not cause convulsions?
The brain activity and firing rate is still controlled
True or false?
Focal seizures with impaired awareness are most common in young people?
True
True or false?
Focal seizures with impaired awareness affect the part of the brain associated with awareness?
True
Which type of seizure is categorized by an individual being unable to speak/respond, drooling, unare, tired
Focal seizure with impaired awareness
Do focal seizures with impaired awareness have a slow or fast recovery?
Slow
Do focal seizures with impaired awareness affect only one part of the brain (left or right) or both?
One
What are the two types of focal seizures?
With and without awareness
Do focal seizures involve the entire brain?
No
What type of seizure may result in an individual jerking to one side?
Focal
Do focal seizures start in one area of the brain?
No
What type of seizure is categorized by subtle muscle jerks?
Myoclonic seizures
What is the bad news of myoclonic seizures in babies?
98% chance of severe retardation even if treated
What type of seizure causes a pattern of the same pose every couple of seconds apart?
Myoclonic
What do the brain waves of myoclonic seizures show?
Brief contraction of muscles at the same time on both sides of the body
