Biology Checkpoint 2 - Neurons
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What is a neuron?
A nerve cell that can be found in nervous tissue, the fundamental function of a neuron is to receive, integrate, conduct, and transmit electrical signals, or nerve impulses
What are the three different neuron types?
Sensory, motor, interneurons
What are sensory neurons?
Sensory neurons are part of the PNS, and they carry nerve impulses from tissues and organs to the spinal chord and brain
What are motor neurons?
Motor neurons are part of the PNS, and they carry nerve impulses from the brain and spinal chord to muscles and glands
What are interneurons?
Interneurons are part of the CNS, and they carry nerve impulses back and forth between sensory and motor neurons
What are the different parts of a neuron?
Dendrites, soma, axon, axon terminals, myelin sheaths, synapses
What are dendrites?
Dendrites are branching structures that extend from the cell body, and they receive signals from other neurons or sensory receptors
What is the soma/cell body?
The soma contains the nucleus and other vital organelles. Info received from dendrites is put together, and the decision to send a nerve impulse “message” is made
What is the axon?
The axon is a single, long extension of the cell body
What does the axon do?
The axon transmits info (electrical impulses or action potentials) from the cell body to the next destination
What are the axon terminals?
Axon terminals (located at the end of the axon) are where the neuron communicates with other cells by releasing neurotransmitters into the synaptic cleft
What is a myelin sheath?
The myelin (a lipid) sheath covers the axon and acts as a layer of insulation. Gaps in the myelin sheath, called the nodes of ranvier, let nerve impulses skip along the axon quickly
How are electrical signals made?
Electrical signals result from a difference in electrical charge across the cell membrane of a neuron
How does a difference in the electrical charge across a cell membrane form?
The difference in electrical charge is the result of positive ions (excess protons) and negative ions (excess electrons)
What are the 5 key proteins in the axon of a neuron?
Sodium leak channel, potassium leak channel, voltage-gated sodium leak channel, voltage-gated potassium channel, and the sodium potassium pump
What is the resting potential of a neuron?
The resting potential of a neuron is when a neuron is not actively transmitting signals
What is happening to the ions in the cell membrane during the resting potential?
During the resting state, the sodium-potassium (Na+-K+) pump maintains a difference in charge through active transport
In what way does the pump circulate Na+ and K+ ions?
The pump uses ATP to pump 3Na+ out, and 2K+ in to the cell.
What does the difference in the amount of sodium and potassium pumped result in?
More positive charge leaves the cell, and the inside of the neuron is negatively charged while the outside is positive in comparison. This difference in electrical charge is the resting potential.
What is the standard amount of millivolts in a neuron during the resting state?
around -70mV
What is the action potential?
The action potential is a sudden reversal of electrical charge across the membrane of a resting neuron.
What are the sequential phases of an action potential?
Reaching threshold, depolarization, re-polarization, and the refractory period
What are Ion channels?
Ion channels move ions down their electrochemical gradients using passive transport only. Ions pass in single file through the selectivity filter, and the speed of the throughput gets faster as the amount of ions increases.
What are voltage-gated Ion channels?
Ion channels that open and close due to chemical or electrical stimuli.