Exam 4 | Nervous system pt. 1 Flashcards
What’s the neuron?
The neuron is the primary cell type found in the central nervous system.
What do all neurons exhibit?
Electrical properties meaning that they are capable of propagating electrical signals
What’s the cell body?
Sometimes called the soma; it houses the nucleus and other membrane-bound organelles
What are dendrites?
They’re spiny projections that receive signals from neighboring neurons and cells
What’s an axon?
An axon is a long projection that extends away from the cell body in order to relay electrical signals; it’s relayed in 1 direction
What are synaptic terminals?
This is where neurotransmitters are released into an empty space called the synapse
Describe unipolar neurons.
They have no dendrites and a single axon; these neurons aren’t too common in the CNS and can be found in the olfactory bulb
Describe bipolar neurons.
These nurons have 2 separate axons going in opposite directions; almost exclusively sensory neurons like the retina
Describe pseudounipolar neurons.
Similar to unipolar neurons in that they only have a single projection (axon), however, this projection extends in either direction, similar to the morphology of bipolar neurons; lacks a myelin sheath; found in dorsal horns of spinal cord where pseudounipolar somatosensory neurons are located
Describe multipolar neurons.
They exhibit all the traditional neuronal cell structures like dendrites, a cell body, an axon and synaptic terminals; the largest in the entire CNS being the pyramidal cells, which get their name from their pyramid-shaped cell body.
What’s an interneuron?
Found exclusively in the spinal cord; these neurons often exist at the “intersection” between two sensory neurons, two motor neurons, or one sensory and one motor neuron, in order to help regulate reflexes and other behavioral responses. In addition, these interneurons are almost exclusively inhibitory in their signaling
What’s Ohm’s law?
Ohm’s law allows us to understanding how electrical current flows through a neuron (and specifically, how this current propagates down the axon of the neuron).
What’s voltage?
It’s an uneven distribution of electrons (charge differences between the extra- and intra- cellular side of the neuron); this creates an electromotive force
What is current (I)?
This is the movement of electrons; the movement of cations in the neuron that generates an electrical current; moves in 1 direction
What’s resistance?
There’s 2 types:
1) membrane resistance is the difference across neuron cell membrane, and myelination lowers membrane resistance the more myelin an axon has
2) longitudinal resistance is the resistance within the axon, the diameter of the axon correlates to the resistance; the wider the axon, the less longitudinal resistance there is
What’s membrane potential?
It is the charge difference across a cell’s membrane.
What’s chemical gradient?
It refers to the difference in concentration (quantity) of an ion on either side of the membrane
What’s the action potential?
It is a unidirectional communication mechanism that allows neurons to send electrical (and chemical) signals from one cell to the next
What are some features of action potentials?
- any cell capable of producing electrical activity can fire an action potential
- the action potential must proceed in one direction
- while most action potentials are considered to be all or nothing, some action potentials are an exception to this, and are referee to as graded potentials
In order for a neuron to actually gire an action potential, what must happen?
The threshold potential (-55 mV) must be exceeded
When a neuron is not firing an action potential, what stage is it in?
It maintains a resting potential (-70 mV)
What are the 3 phases of action potential called?
Depolarization, repolarization, and Hyperpolarization
What happens in the depolarization phase?
The threshold potential is reached & sodium voltage-gated channels begin to open
What happens in the repolarization phase?
Once sodium ions reach equilibrium, voltage-gated sodium channels close and potassium ions begin to flow out of the cell
What happens in the hyperpolarization phase?
There’s a brief period when more potassium ions leave the cell while voltage-gated channels begin to slowly close
What pump is used during the hyperpolarization phase?
The sodium-potassium pump
What’s the role of the sodium-potassium pump?
It plays a critical role in restoring the resting potential of the neuron; the pump forces 3 sodium ions out the ell and pushes 2 potassium ions into the cell
What’s myelin?
It is a lipid-rich sheath that wraps around the insulates of the axon of neurons; most neurons are myelated to some degree
What does increased myelination do and how?
It allows for a faster rate of action potential because it creases segmens of the axon in which there are no ion channels; this results in saltatory conduction which allows the action potential to “skip” the myelinated sections of the axon.
Where are ion channels present in the axon?
In gaps between myelin sheaths called the nodes of ranvier
