Week 5 Readings Flashcards
What are the 5 different sensory systems that neurons receive information from?
Vision, audition, olfaction, gustation and somatosensation
Who is considered the father of modern neuroscience for concluding that neurons are the structural and functional units of the nervous system?
Santiago Ramón y Cajal (1911).
What staining technique did Santiago Ramón y Cajal use to observe individual neurons?
The Golgi stain.
What is unique about the Golgi stain in terms of neuron visualization?
The Golgi stain fills the entire cell body and its processes but only stains about 1-2% of neurons.
his low percentage is actually a big advantage because if all the neurons were stained, they would overlap, making it hard to distinguish one neuron from another. By only staining a few neurons, the Golgi stain allows scientists to see the detailed structure of individual neurons clearly, without interference from surrounding cells.
What does a Nissl stain label?
Only the main part of the cell (i.e, the cell body)
What was Camillo Golgi’s stance on the structure of the nervous system, and how did it differ from Cajal’s view?
Golgi supported the theory that the nervous system was a continuous network (theory by Joseph von Gerlach), while Cajal argued that neurons were individual, distinguishable processing units.
How did Cajal’s use of the Golgi stain revolutionize our understanding of the nervous system?
It allowed him to observe the full anatomical structure of individual neurons for the first time, challenging the idea of a continuous nerve network.
What are the three main components of a neuron?
Dendrites, soma (cell body), and axon.
What is the primary function of dendrites in a neuron?
Dendrites receive information from thousands of other neurons and serve as the main source of input for the neuron.
What part of the neuron contains the nucleus and directs protein synthesis?
The soma (cell body).
What is the role of the nucleus in a neuron?
The nucleus contains genetic information, directs protein synthesis, and provides the neuron with energy and resources to function.
What is the function of the axon in a neuron?
The axon carries an important signal, called an action potential, from the neuron’s soma to another neuron. It acts as the main source of output for the neuron.
Where does communication between two neurons typically occur?
At the synapse, the point where the axon of one neuron comes into close contact with the dendrite of another neuron.
What is the function of the myelin sheath, and where is it found?
The myelin sheath is an insulating layer that covers the axon, allowing electrical signals to travel rapidly between neurons.
What signal does the axon carry to other neurons?
An action potential.
What happens to the axon as it approaches other neurons?
The axon splits many times to communicate or synapse with several other neurons.
What is located at the end of the axon, and what is its role?
The terminal button, which forms synapses with spines on the dendrites of other neurons.
What are the two components involved in a synapse?
The presynaptic terminal button (the neuron sending the signal) and the postsynaptic membrane (the neuron receiving the signal).
Besides dendritic spines, what other structures can form synapses with the terminal button of an axon?
Synapses can also form with the soma (cell body) or the axon of another neuron.
What are dendritic spines?
Protrusions on dendrites where synapses are formed with the terminal button of an axon.
What is the significance of the terminal button in neural communication?
The terminal button is where neurotransmitters are released to transmit signals to other neurons at the synapse.
What is the small space called that exists between the presynaptic terminal button and the postsynaptic dendritic spine? How wide is it
The synaptic gap or synaptic cleft.
Approximately 5 nanometers (nm).
What are synaptic vesicles, and where are they found?
Synaptic vesicles are found in the presynaptic terminal button and package groups of chemicals called neurotransmitters.
What is the role of neurotransmitters in synaptic transmission?
Neurotransmitters are released from the presynaptic terminal button, travel across the synaptic gap, and bind to receptor sites on the postsynaptic spine to activate ion channels.
How do sensory neurons, motor neurons, and interneurons work together?
Sensory neurons receive information, interneurons process that information and plan responses, and motor neurons execute those responses through movement.
Why are interneurons important in the nervous system?
Interneurons are crucial for processing sensory input and coordinating the appropriate responses between sensory and motor neurons.
What are the three main categories of neurons? Which are the most common?
Unipolar neurons, bipolar neurons, and multipolar neurons.
The most common are multipolar neurons
What is the structure of unipolar neurons, and what is their function?
Unipolar neurons have one neurite (axon) and no dendrites, making them ideal for relaying information forward, such as transmitting physiological information like body temperature to the brain.
What type of sensory perception do bipolar neurons facilitate?
Bipolar neurons are involved in sensory perception, such as the perception of light in the retina of the eye.
Describe the structure and function of bipolar neurons.
Bipolar neurons have one axon and one dendrite, which help acquire and transmit sensory information to various centers in the brain.
What distinguishes multipolar neurons from other types of neurons?
Multipolar neurons have one axon and many dendrites, allowing them to communicate sensory and motor information in the brain.
What is one example of a multipolar neuron, and what is notable about its structure?
A prominent example is the pyramidal neuron, which has a triangular or pyramidal shape of its soma.
How do multipolar neurons function in the body?
Multipolar neurons communicate sensory and motor information; for instance, their firing can cause muscle contractions.
What are glia cells, and how do they differ from neurons?
Glia cells are a second type of cell in the brain that provide support to neurons but do not participate in communication between cells like neurons do.
What is the function of oligodendroglia in the nervous system?
Oligodendroglia form the myelin sheaths that insulate axons, facilitating rapid signal transmission.
How do oligodendroglia create myelin sheaths?
Oligodendroglia wrap their dendritic processes around the axons of neurons many times to form the myelin sheath.
Can one oligodendroglial cell form myelin sheaths for multiple axons?
YES
What are microglia and astrocytes?
They are types of glia cells that digest debris from dead neurons, provide nutritional support from blood vessels to neurons, and help regulate the ionic composition of the extracellular fluid.
Why are glial cells considered vital for neuronal support?
Glial cells provide essential support functions for neurons, including nutrient transport, debris removal, and maintaining the ionic environment, but they do not engage in direct cell communication like neurons.
What is the composition of intracellular and extracellular fluid in neurons similar to? Name some of the keys ions present.
It is similar to salt water.
Sodium (Na+), potassium (K+), chloride (Cl–), and anions (A–).
What role do ions play in neuronal function?
Ions are essential for generating and transmitting electrical signals in neurons, influencing actions like action potentials and synaptic transmission.
What is electrostatic pressure?
Electrostatic pressure is the force on two ions with similar charge to repel each other and the force of two ions with opposite charge to attract to one another.
What is the equilibrium potential?
The equilibrium potential is the voltage at which the force of diffusion is equal and opposite to the force of electrostatic pressure, resulting in no net ion flow.
What is the resting membrane potential of a neuron, and what is its typical value?
It is the baseline electrical charge inside the cell compared to the outside, typically around -70 mV.
Why is the resting membrane potential negatively charged relative to extracellular fluid?
The resting membrane potential is negatively charged due to the collective drive of several ions that can permeate the cell’s membrane, influencing the electrical charge.
What does a negative resting membrane potential indicate about the distribution of ions inside and outside the neuron?
A negative resting membrane potential indicates that there is a higher concentration of positive ions (like Na+ and K+) outside the neuron compared to the inside.
What role do anions (A–) play in the resting membrane potential?
Anions are highly concentrated inside the cell and contribute to the negative charge of the resting membrane potential; however, they are impermeable to the cell membrane and do not move between compartments because there are no ion channels.
What is K+ like at rest?
How do diffusion and electrostatic pressure affect potassium ions (K+) in the neuron?
The cell membrane is very permeable to K+ at rest, but it remains at high concentration inside the cell.
Diffusion pushes K+ outside the cell due to high internal concentration, while electrostatic pressure pulls K+ inside because of the negative charge in the cell, resulting in opposing forces.
What is Cl- like at rest?
What happens to chloride ions (Cl–) regarding diffusion and electrostatic pressure in the neuron?
The cell membrane is very permeable to Cl- at rest, but it remains in high concentration outside the cell.
Diffusion pushes Cl– inside the cell due to high external concentration, while electrostatic pressure pushes Cl– outside because of the positive charge outside the cell, creating opposing forces.
What are the characteristics of sodium ions (Na+) in relation to the cell membrane at rest?
The cell membrane is not very permeable to Na+, but diffusion pushes Na+ inside due to high external concentration, and electrostatic pressure also attracts Na+ inside because it is attracted to the negative charge within the cell.
Na+ cannot permeate the cell membrane and remains in high concentration outside the cell.
Why do sodium ions (Na+) remain in high concentration outside the cell?
Although both diffusion and electrostatic pressure push Na+ inside, Na+ cannot permeate the cell membrane at rest. Small amounts of Na+ inside are removed by the sodium-potassium pump.
What is the function of the sodium-potassium pump in neurons?
The sodium-potassium pump uses ATP to remove 3 Na+ ions from the cell in exchange for bringing 2 K+ ions inside, maintaining ion concentration gradients.
Who were Hodgkin and Huxley, and what did they study?
Hodgkin and Huxley were scientists who studied the electrical properties of neurons, particularly using the giant axon of the squid, and developed a general model of electrochemical transduction.
They received the Nobel Prize in Medicine in 1963 for their research on neuron function and electrical signaling.
What is an action potential?
An action potential is a large, transient electrical current conducted down the axon when the membrane potential becomes more positive than the resting membrane potential.
What does the term “all-or-nothing response” mean in relation to an action potential?
An all-or-nothing response means that the action potential either occurs completely or not at all
What must happen for an action potential to be triggered?
The membrane potential must reach a specific value called the threshold of excitation, typically around -50 mV, for an action potential to occur.
What is depolarization in the context of an action potential?
Depolarization is the change in membrane potential in a more positive direction from the resting state, leading to the initiation of an action potential.
How did Hodgkin and Huxley discover the concept of action potentials?
While studying the giant axon of the squid, they observed that applying an electrical stimulus triggered a large, transient electrical current, which they identified as an action potential.
What are excitatory postsynaptic potentials (EPSPs)?
EPSPs are depolarizing currents that make the membrane potential more positive, bringing it closer to the threshold of excitation, increasing the likelihood of an action potential.
What are inhibitory postsynaptic potentials (IPSPs)?
IPSPs are hyperpolarizing currents that make the membrane potential more negative, moving it further away from the threshold of excitation, decreasing the likelihood of an action potential.
How do EPSPs and IPSPs affect the membrane potential?
EPSPs cause depolarization, making the membrane potential more positive, while IPSPs cause hyperpolarization, making it more negative.
How does a neuron decide whether to fire an action potential?
A neuron integrates hundreds of inputs, and if the combined effects of EPSPs and IPSPs bring the membrane potential to the threshold of excitation, an action potential is triggered.
How do EPSPs and IPSPs interact at a synapse?
PSPs and IPSPs summate or add together in time and space. The combined effect depends on the strength of each individual postsynaptic potential.
What happens when two small EPSPs occur at the same time and place?
When two small EPSPs occur simultaneously at the same synapse, they add together to create a larger EPSP.
What happens when an EPSP and an IPSP occur at the same time and place?
If an EPSP and an IPSP occur simultaneously at the same synapse, they cancel each other out.
How do EPSPs and IPSPs differ from action potentials?
Unlike the all-or-nothing action potential, EPSPs and IPSPs are graded potentials, meaning their strength can vary depending on the input.
What is the typical voltage change during an action potential compared to EPSPs and IPSPs?
The voltage change during an action potential is approximately 100 mV, while EPSPs and IPSPs cause voltage changes ranging from 0.1 to 40 mV.
How is the strength of EPSPs and IPSPs measured?
The strength of EPSPs and IPSPs is measured by how much the membrane potential diverges from the resting membrane potential.
Why are EPSPs and IPSPs called graded potentials?
EPSPs and IPSPs are called graded potentials because their strength varies depending on the magnitude of the input, unlike the all-or-nothing nature of action potentials.
What happens when the summation of EPSPs is strong enough to reach the threshold of excitation?
When the summation of EPSPs depolarizes the membrane potential to the threshold of excitation, it initiates an action potential.
What happens to the action potential once it is initiated?
The action potential travels down the axon, away from the soma, until it reaches the terminal button at the end of the axon.
From there, it releases neurotransmitters into the synaptic cleft.
Neurotransmitters bind to ionotropic receptors on the postsynaptic dendritic spines, causing ion channels to open and allowing ions to enter or exit the cell.
What determines whether an EPSP or IPSP occurs in the postsynaptic cell?
The type of neurotransmitter released and the permeability of the ion channel it activates will determine whether an EPSP (excitatory) or IPSP (inhibitory) occurs in the postsynaptic cell.
How do EPSPs and IPSPs in the postsynaptic cell influence the next action potential?
EPSPs and IPSPs in the postsynaptic cell summate, and if the overall depolarization reaches the threshold of excitation, the entire process begins again in the next cell.
How do ionotropic receptors work?
Ionotropic receptors are ion channels that open when a specific neurotransmitter binds to them, allowing ions to enter or exit the cell, influencing whether an EPSP or IPSP occurs.
Which ions are involved in generating the action potential?
Sodium (Na+) and potassium (K+) are the primary ions involved in generating the action potential.
What happens when a neuron reaches the threshold of excitation?
Voltage-dependent Na+ channels open, allowing Na+ to rush into the cell, causing depolarization.
Why does Na+ rush into the cell when voltage-dependent Na+ channels open?
Both diffusion and electrostatic pressure push Na+ inside the cell, which causes the cell to become more positively charged (depolarized).
What is the peak membrane potential during the depolarization phase of the action potential?
The inside of the cell becomes very positively charged, reaching approximately +40 mV.
