Lec 2: Neurophysiology Part 1: Cells and Connections Flashcards
What is a nerve cell (neuron)?
Fundamental component of the nervous system
In general, what is a glial cell?
support system for neurons
What functions do glial cells do for neurons?
- Set neurons and connections to stay in place
- Removes, Repairs, & migrates damaged neurons
- Middle-man between blood and brain, therefore…
- Help energize neurons to provide nutrients and oxygen from blood to brain
- Forms Myelin around axons/neurons
What are the (3) Types of Neurons?
Motor Neurons “Efferent Neurons”
Sensory Neurons “Afferent Neurons”
Interneurons
How do Motor Neurons “Efferent Neurons” function?
Motor Neurons receive input by other neurons, but send output to muscles.
Between the two types of Motor Neurons, which one sends output directly from the Central Nervous System to muscles to create movement?
Alpha Motor Neuron
Between the two types of Motor Neurons, what do Gamma Motor Neurons do?
Test and activate sensory receptors, muscle spindles, in the muscle to tell the nervous system how the muscle is behaving
How do Sensory Neurons “Afferent Neurons” function?
Receive info my sensory receptors, then send output to other neurons involving direction of flow from periphery back to the brain
What are Interneurons, and how do they function?
Neuron that receives input from another neuron, forming connection with other neurons.
Function: Process information in the brain to create action
Where does a neuron receive its input? Output?
Input = Dendrites Output = Axon Terminal
Describe the process of how a neuron functions?
1) Dendrites receive impulses from other neurons and flows to the soma (cell body)
2) Soma gains action potential
3. ) Potential travels through the axon to other neurons by exiting through the Axon Terminal
What is the Soma?
Neuron Cell Body between dendrites and axon
What happens in the Soma? What is the significance of the “Summation Principle”?
In the soma, a variety of impulses are collected /summed from multiple dendrites
.
What is the “All or None Principle”?
Depending on the neuron’s threshold, if the summation of impulses do not surpass and are not generated. It will not fire action potential through the axon.
Surpasses threshold? Action potential will fire through the axon.
What is EPSP (Excitatory post-synaptic Potential))?
When impulse is coming into a dendrite, the neuron that is receiving the input will decrease,taking time to reach cell membrane potential.
Why do Post Synaptic Potentials last for 15 milliseconds?
Opportunity for action potential to gather in the soma and cross threshold completely.
This will allow time for the soma to gather more impulses to reach potential consistently. If a 2nd input comes quick enough to the waiting 1st input, a better chance to cross threshold and fire will result.
Summation = combination ( or balance) of ____ + ____
EPSP + IPSP ( Inhibitory Post-Synaptic Potential)
combination ( or balance) of (decrease + increase)
What are (2) types of Summation?
Temporal & Spatial Summation
What is Temporal Summation?
If the 1st input is quickly accompanied by a faster 2nd input within the 15 milliseconds, a larger action potential will occur and likely pass the threshold faster
What is Spatial Summation?
When multiple synapse sites are directly effecting the dendrites, sending inputs all at once into the soma. This will allow potential to cross the threshold very very quickly.
What is an axon?
wire-like cord after the soma that transmits the impulse
What is myelin and what is its purpose?
layer surrounding the axon and providing electrical insulation so the impulse will not escape during its trip through the axon
What are Nodes of Ranvier? Why?
gaps in the myelin sheath
This exposes neurons to extracellular fluid. The flow of ions moving through the gaps generates the push of neurons
What is Saltatory Conduction?
action potential jumping from node to node, than a continuous wave
what can demyelination caused by diseases result in?
Decrease in neuron speed, therefore also less travel distance
No insulation can allow leak of signals & no generating
What is an Axon Terminal?
the ending of a neuron
What is synapse (Syaptic Cleft)?
(gap) connection between axon of one cell and dendrite of another cell
What is a neurotransmitter?
molecules released by pre-synaptic neuron, binding to dendrites on post-synaptic cell
What is an Obligatory synapse? Example
When a pre-synaptic action potential will ALWAYS cause a post -synaptic system
Example: “muscle twitch”
What is a Non-Obligatory synapse? Example
A single actionP potential is not enough to cause a post-synaptic potential
Example: It will take more potential to cross threshold to fire
What is the difference between chemical potential vs. electrical potential?
Chemical involves the attachment to post-synaptic receptors
Electrical involves the direct flow of neurons to the post-synaptic cell by an open channel without the middle gap
What kind of neurotransmitter is Acetylcholine? How is it used?
Not an amino acid
used by motor neurons in spinal to activate muscles directly
What is Catecholamines? How is it used?
Derived by Tyrosine amino acid
Includes: Dopamine, Norepinephrine, and Epinephrine
What is Serotonin derived from?
Derived from tryptophan amino acid
What is the purpose of the cell membrane?
separate internal and external environment of the cell by lipid layers, allowing specific ions. flow in and out by protein channels.
How can an electric current happen in a cell membrane?
Ions that possess charges, move in and out of the cell creating an electric current
What involves making a potential either more positive
(or less negative)? At rest?
Negative ions moving out of the cell
Positive ions moving into cell
Both
At rest; channels are close and do not allow ion passages
What contributes to ion movement?
diffusion & voltage gradients
What is the Diffusion?
Ions moving from high concentration to low concentration
What is Voltage Gradient?
Movement of ions will be dependent on charge
due to electric field
Example: Positive ions in the outside will not flow inside based on charge, while inside charge is positive
In terms of equilibrium potential, what happens if the concentration is zero? Concentration outside greater than inside? Concentration outside less inside?
At zero, potential is at rest Concentration outside greater than inside: Potential =Higher Concentration outside less than inside: Potential = Less
What is the potential of a resting membrane if ions are moving in and out equally?
-70 millivolts
In membrane stimulation, if I applied an electrical impulse to a neuron cell membrane, how strong and how far will the stimulation go?
Stimulation will be a large charge in potential locally, but fade away as it moves away from the location
What type of polarization if a cell contains more negative inside? positive?
Negative = Hyperpolarization
Positive=Depolarization
Sodium and Potassium channels open under certain voltages, what are they?
Sodium “depolarizes” at -70mV to -45 mV
Potassium opens when action potential reaches around +40mV
Following action potential, what is the Absolute Refractory period?
Brief period immediately after action potential, preventing a second action potential during this period
What is the Relative Refractory period?
Brief period immediately after Absolute Refractory period, allowing generation of a second action potential
Post-Synaptic cells can resist action potential from all inputs, which is called Post-Synaptic Inhibition. How does this happen?
Resting potential of neuron is negative, therefore further away from the action potential threshold.
Greater input from the pre-synaptic cell will be needed to reach the threshold
Renshaw Cells act in recurrent inhibition, feeding back the same motor neuron that was givin’ and inhibiting the action potential. Why does this happen?
Negative feedback allows us to regulate and control our motor activity
What is Pre-Synaptic Inhibition?
Poste-synaptic cell can resist input from all or particular pre-synaptic cells
What are (2) examples of Post-Synaptic Inhibitors?
Renshaw Cells & 1a-motorneurons
1a-interneurons use Reciprocal Inhibition to show post-synaptic inhibition. What is Reciprocal Inhibition?
Inhibiting the action of the antagonist muscle, while activating an agonist muscle
