Transmission and Integration of Neuronal Signal Flashcards
What are neurons?
Neurons are the excitable cells in the brain.
What are the functions of neurons?
- Receive and respond to inputs from other neurons or the periphery
- Integrate signals and “decide” whether to transmit or not.
- Rapidly conduct electrical signals long distances along their axons.
- Activate other brain cells either electrically or by releasing chemical transmitters.
What is a morphological sign that neurons are specialized for communication?
Their extensive branching
What it the role of the soma (cell body)?
- Collecting information
- Deciding if it should act on it (if it reaches the threshold then the spike will propagate down the axon.
What is the role of the dendrites? What are found there?
- They are where electric inputs are
- Where synapses form
- They have a high content of ribosomes and have specific cytoskeletal proteins.
- They are the primary target for synaptic input.
What happens at the axon terminal (synapse)?
The action potential ends here and propagates the signal further.
Name the parts of the neuron
What are neurons distinguished by?
- Their specialization for long-distance electrical signalling.
- Intracellular communication via synapses.
How do neurons conduct information? What can this be measured as?
Neurons conduct information by the movement of ions across the membrane in response to the opening of ion channels (Na, K, Ca).
This can be measured as electrical impulses. Where the ions = the charge and the charge movement = current.
What are the inputs and outputs of information conduction of a neuron?
Input = induced graded changes in membrane voltage.
converted to
Output = all-or-none action potentials (spikes)
What is an action potential?
A self-generating wave of electrical activity (either fire or not fire).
What is resting potential?
Neuronal resting potential is the voltage difference between the inside and outside of a neuron not receiving inputs (resting). Usually, the cytoplasm rest at about -65 to -80 mV relative to the extracellular space in a mature neuron.
What is the threshold for firing an action potential?
The threshold for firing an action potential (AP) is usually around -40mV. If EPSPs sum up to bring the membrane potential to the threshold, the cell will fire.
Excitatory Postsynaptic Potential
Excitatory Postsynaptic Potential (EPSP): a small excitatory event that makes the membrane depolarize, typically by about 10mV.
Excitatory causes cell to depolarize, become more positive.
Inhibitory Postsynaptic Potential
Inhibitory Postsynaptic Potential (IPSP): a small inhibitory event that males it harder for the membrane to reach the threshold for an action potential.
Inhibitory causes cell to become more negative.
Hyperpolarization
When the membrane potential becomes more negative.
When hyperpolarization occurs, the membrane potential changes in proportion to the magnitude of the current. This does not require any unique property of the neurons and is called passive electrical response.
Depolarization
The membrane potential becomes more positive.
How many different neurons are involved in the knee jerk response? Name them
There are 4 neurons involved in the knee jerk response.
Sensory neuron, interneuron and 2 motor neurons.
How many synapses are involved in the knee jerk reflex?
3 synapses
What are the steps in the knee jerk response?
Extensor muscle = quad, Flexor muscle = hamstring
When you tap a hammer to your knee, your leg will kick out. In order for your leg to kick out, the quad muscle has to flex (aka get shorter) and the hamstring muscle has to do nothing (not object).
- The sensory neuron (DRG neuron) detects the tap and sends the signal down the axon, in the form of action potentials, to the spinal cord.
- In the spinal cord, it synapses onto two cells. One of them is the motor neuron that innervates your quad muscle (the one that has to flex) and the other one will innervate an inhibitory interneuron.
- In both these cases, the sensory neuron will release glutamate to excite both the cells. It will cause the motor neuron to be excited and flex the quad muscle. It will also cause the interneuron to be excited and release GABA or glycine (inhibitory neurotransmitters) onto the motor neuron that innervates the hamstring muscle. Therefore, it causes a large IPSP in the motor neuron that innervates the hamstring muscle causing it to not fire.
- The neurotransmitter that is released in the neuromuscular junction is acetylcholine (hamstring muscle)- excitatory.
How do the synaptic EPSPs and IPSPs translate into changes in action potential firing rates?
- EPSPs can summate in space or in time to depolarize the neuron to the threshold to fire an action potential.
- IPSPs can impede the cell from reaching threshold for firing an action potential.
Excitatory neurons release…
Inhibitory neurons release…
Excitatory neurons release excitatory neurotransmitters.
Inhibitory neurons release inhibitory neurotransmitters.
Inputs from the environment are most oftern…
Excitatory
Most neurons integrate ____________ onto their somatodendritic compartments into an all or nothing ________ code to ___________.
- graded inputs
- temporal
- transmit information