Neurons
What are epinephrine and norepinephrine implicated in?
Mood disorders.
What are the three ways in which neurotransmission is terminated?
(1) Diffusion, (2) enzyme function, and (3) reuptake.
What are the four major activating systems in the brain?
(1) The cholinergic system, (2) the dopaminergic system, (3) noradrenergic system, and (4) the serotonergic system.
What constitutes as "very positively charged?"
+40mV.
Interneurons make up about _____% of the neurons in the body.
20
About how many neurons are in the body?
86 million
About how many glial cells are in the body?
87 million.
What occurs with K+ as depolarization occurs?
A K+ channel opens, allowing K+ to be driven out of the cell, along with effort from diffusion and electrostatic pressure.
What is microglia?
A cell that digests debris of dead neurons, carries nutritional support from blood vessels to neurons, and helps to regulate the ionic composition of the extracellular fluid.
Describe the cycle of communication within and between neurons.
A neurotransmitter and an action potential are sent from one neuron to the next. It is received by the dendrites, sent through the soma, escorted along the axon with the myelin, bounces from node to node, and then is sent through the terminal buttons. Any excess is either disposed over, or reuptaken.
What does the statement that communication within and between cells is an electrochemical process?
A neurotransmitter is a chemical, but an action potential is electrical. Both are sent through every neuron when communicating is being performed, so they are sending electrochemical messages.
How does a neurotransmitter bind and what does it bind to?
A neurotransmitter locks in a lock-and-key fashion on the postsynaptic dendrite spine.
What is GABA?
A neurotransmitter that has general inhibition and assists in relieving anxiety and improving mood.
What is epinephrine?
A neurotransmitter that is involved in alertness and arousal.
What is norepineprhine?
A neurotransmitter that is involved in alertness and arousal.
What is acetycholine?
A neurotransmitter that is involved in memory and learning.
What is serotonin?
A neurotransmitter that is involved in mood, hunger, sleep, and arousal.
What is dopamine?
A neurotransmitter that is involved in movement, learning, attention, and emotion.
What is an action potential?
A part of the process that occurs during the firing of a neuron.
What is glutamate?
A powerful excitatory neurotransmitter that is released by nerve cells in the brain.
What is one of the most prominent neurons? Which category does it fall under? Where does it get its name from?
A pyramidal neuron, which falls under the multipolar category. It gets its name from the triangular or pyramidal shape of its soma.
What is the synaptic gap?
A small space between the presynaptic terminal button and the postsynaptic dendritic spine.
What is the cholinergic system?
A system composed of acetylcholine.
What is the dopaminergic system?
A system composed of dopamine.
What is the noradrenergic system?
A system composed of norepinephrine.
What is the serotonergic system?
A system composed of serotonin.
What does refractory refer to?
A time in which a cell is incapable of repeating an action potential.
What happens when the cell becomes depolarized and reaches the threshold of excitation?
A voltage-dependent Na+ channel opens.
What is a neurite?
An axon.
What is ATP?
An energy-carrying molecule found in the cells of all living things.
What is gamma-aminobutyric acid (GABA)?
An inhibitory neurotransmitter that inhibits certain brain signals and decreases activity in your nervous system.
What is the nucleus?
An organelle that contains genetic information, directs protein synthesis, and supplies the energy and the resources needed to function.
What is the cell membrane?
An organelle that separates the cell from the surrounding extracellular fluid.
What are the 4 elements that transfer in and out of the cell membrane?
Anions (A-), potassium (K+), chloride (Cl-), sodium (Na+).
What do purkinje cells do?
Assist with controlling motor movement.
What do pyramidal cells do?
Assist with controlling motor movement.
Where do synapses form?
Between the presynaptic terminal button and the postsynaptic membrane.
How are EPSPs and IPSPs determined?
By the neurotransmitter.
What are astrocytes?
Cells that digest debris of dead neurons, carry nutritional support from blood vessels to neurons, and help to regulate the ionic composition of the extracellular fluid.
What are glia cells?
Cells that support neurons.
Neurotransmitters that open ____ channels cause an IPSP.
Cl- or K+.
What does an agonist do?
Creates a certain action, essentially mimicking the way a receptor or activator works.
What does voltage-dependent refer to?
Depending on the voltage.
What are excitatory postsynaptic potentials (EPSPs)?
Depolarizing currents that causes the membrane potential to become more positive and closer to the threshold of excitation.
How do diffusion and electrostatic pressure contribute to the resting membrane potential and the action potential?
Diffusion and electrostatic pressure essentially try to balance out the charge of the membrane inside and out. Because of this process, it helps return the cell to resting membrane potential after depolarization, allowing for a new action potential.
How does diffusion work on anions (A-)?
Diffusion does not work on anions (A-).
How does diffusion work on chloride (Cl-)?
Diffusion pushes Cl- inside the cell because of the concentration outside.
How does diffusion work on potassium (K+)?
Diffusion pushes K+ outside of the cell because it is in high concentration inside the cell.
How does diffusion work on sodium (Na+)?
Diffusion pushes Na+ inside the cell because all the sodium is outside of the cell.
How are EPSPs and IPSPs different from action potentials?
EPSPs and IPSPs are smaller and graded potentials, varying in strength.
What are ions?
Electrically charged atoms.
How does electrostatic pressure work on anions (A-)?
Electrostatic pressure does not work on anions (A-).
How does electrostatic pressure work on chloride (Cl-)?
Electrostatic pressure pushes Cl- outside the cell because the negative charge of Cl- is attracted to the positive charge outside the cell.
How does electrostatic pressure work on potassium (K+)?
Electrostatic pressure pushes K+ inside the cell because the positive charge of K+ is attracted to the negative charge inside the cell.
How does electrostatic pressure work on sodium (Na+)?
Electrostatic pressure pushes Na+ inside the cell due to the attraction of the negative charge in the cell.
What are the 5 types of glial cells?
Ependymal, oligodendroglia, schwann, astrocyte, and microglia.
Does EPSP relate more to excitation or inhibition?
Excitation.
Is glutamate more associated with inhibition or excitation?
Excitation.
Does an agonist excite or inhibit the neuron?
Excite.
What are ionotropic receptors?
Membrane-bound receptor proteins that respond to ligand binding by opening an ion channel and allowing ions to flow into the cell, either increasing or decreasing the likelihood that an action potential will fire.
What do microglia cells do?
Function as the brain's immune system.
What is an example of a neurotransmitter that causes IPSP?
Gamma-Aminobutyric Acid (GABA).
What is an example of a neurotransmitter that causes an EPSP?
Glutamate.
What type of tissue did Santiago Ramón y Cajal use? Why?
He used Golgi stained tissue because it only stains approximately 1%-2% of neurons, allowing the observer to distinguish one cell from another. This allowed Cajal to examine the full anatomical structure of individual neurons for the first time.
What are inhibitory postsynaptic potentials (ISPSs)?
Hyperpolarizing currents that causes the membrane potential to become more negative and further away from the threshold of excitation.
Does an antagonist excite or inhibit the neuron?
Inhibit.
Does IPSP relate more to excitation or inhibition?
Inhibition.
Is GABA more associated with inhibition or excitation?
Inhibition.
What is the purpose of having K+ channels open?
It allows the cell to return back to resting membrane potential by expelling cations from the very positive cell.
Who was opposed to Santiago Ramón y Cajal's theory? What was that theory?
Joseph von Gerlach, who stated that the nervous system was composed of a continuous network of nerves.
What do ependymal cells do?
Line the ventricles and produce cerebrospinal fluid in the brain.
What do oligodendroglia cells do?
Myelinate the CNS axons.
What do Schwann cells do?
Myelinate the PNS axons.
Neurotransmitters that open ____ channels cause an EPSP.
Na+.
Do IPSPs make the membrane potential more negative or positive?
Negative.
What does hyperpolarizing refer to?
Negative.
What are anions?
Negatively charged ions.
Do glial cells participate in communication the same way neurons do?
No.
What does an antagonist do?
Opposes a certain action, not allowing a receptor or activator to work.
What does depolarizing refer to?
Positive.
What are cations?
Positively charged ions.
What are spines?
Protrusions on the dendrite of neurons that form synapses with terminal buttons on the presynaptic axon.
Who concluded that discrete individual neurons are the structural and functional units of the nervous system?
Santiago Ramón y Cajal.
What do astrocyte cells do?
Support neurons by maintaining chemical balances.
What happens once the cell reaches +40mV?
The Na+ channels close and become refractory.
What happens when an Na+ channel opens on the cell?
The cell becomes very positively charged.
What structures of a neuron are the main input and output of that neuron?
The dendrites are the main input of the neurotransmitters and they are released at the terminal button.
What is fiddusion?
The force on molecules to move from areas of high concentration to areas of low concentration.
What is electrostatic pressure?
The force on two ions with similar charge to repel each other and the force of two ions with the opposite charge to attract one another.
What are nodes of Ranvier?
The gaps in myelin sheath.
What does reuptake refer to?
When the remaining neurotransmitter is reabsorbed into the neuron, allowing it to be used later.
How does myelin allow the action potential to transmit faster?
The myelin insulates the axon, not allowing any fluid to exist between the myelin and cell membrane. Due to this, no ions flow between the intracellular and extracellular fluid, saving the cell from having to expand the energy necessary to rectify or regain the resting membrane potential. Although under the myelin the action potential degrades some, it is still large enough in potential to trigger a new action potential at the next node of Ranvier. In a sense, it jumps from node to node.
How does myelin increase speed and efficiency of the action potential?
The myelin insulates the axon, not allowing any fluid to exist between the myelin and cell membrane. Due to this, no ions flow between the intracellular and extracellular fluid, saving the cell from having to expand the energy necessary to rectify or regain the resting membrane potential. Although under the myelin the action potential degrades some, it is still large enough in potential to trigger a new action potential at the next node of Ranvier. In a sense, it jumps from node to node.
What is the postsynaptic membrane?
The neuron receiving the signal.
What is the terminal button?
The part of the end of the axon that forms synapses with postsynaptic dendrite, axon, or soma.
What is equilibrium potential?
The point at which the force of diffusion is equal and opposite of the force of electrostatic pressure. It is the voltage at which no ions flow.
What does saltatory conduction refer to?
The propagation of action potentials along myelinated axons from one node of Ranvier to the next node.
What happens if you have two small EPSPs at the same synapse?
The result will be a large EPSP.
Where is the nucleus located in a neuron?
The soma.
What is the synaptic cleft?
The synaptic gap.
What is the resting membrane potential?
The voltage inside the cell relative to the voltage outside of the cell while the cell is at rest. It is approximately -70mV.
What are motor neurons?
These are neurons that allow us to initiate movement and behavior, ultimately allowing us to interact with the world around us.
What are sensory neurons?
These are neurons that help us receive information about the world around us.
What are interneurons?
These are neurons that process the sensory input from our environment into meaningful representations, plan the appropriate behavioral response, and connect to the motor neurons to execute these behavioral plans.
What are oligodendroglia?
These glia cells form myelin sheaths.
What are bipolar neurons?
These neurons are involved in sensory perception, such as perception of light in the retina of the eye. They have one axon and one dendrite which help acquire and pass sensory information to various centers in the brain.
What are unipolar neurons?
These neurons are structured in a way that is ideal for relaying information forward, so they have one neurite (axon) and no dendrites. They are involved in transmission of physiological information from the body's periphery such as communicating body temperature through the spinal cord up to the brain.
What are multipolar neurons?
These neurons are the most common and they communicate sensory and motor information in the brain. These neurons have one axon and many dendrites which allows them to communicate with other neurons.
Can EPSPs and IPSPs cancel each other out?
Yes.
What is the threshold of excitation?
This specific membrane potential that the neuron must reach to initiate an action potential. This potential is called the threshold of excitation, which is typically around -50mV.
How was the purpose of the axon discovered?
Using a squid's axon.
What does diffusion refer to in neurotransmission?
When the neurotransmitter disperses and "goes off on its own."