L1 - Nervous System

Question 1

What is the primary function of neurons?

Answer 1

Neurons transmit information both chemically and electrically, from the environment/periphery to the brain and from the brain to the periphery.

Question 2

What ability allows neurons to transmit information?

Answer 2

Neurons generate and conduct electrical impulses, making them excitable cells.

Question 3

How many neurons are estimated to be in the human brain?

Answer 3

Approximately 80 billion neurons are found in the human brain.

Question 4

What are the two main divisions of the nervous system?

Answer 4

The two main divisions of the nervous system are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Question 5

What does the Central Nervous System consist of?

Answer 5

The Central Nervous System consists of the brain and spinal cord.

Question 6

What are the two main components of the Peripheral Nervous System?

Answer 6

The Peripheral Nervous System consists of the autonomic nervous system and the somatic nervous system.

Question 7

What are the two divisions of the autonomic nervous system?

Answer 7

The autonomic nervous system is divided into the sympathetic and parasympathetic systems.

Question 8

What are the two types of pathways in the nervous system?

Answer 8

The two types of pathways in the nervous system are sensory (afferent) and motor (efferent).
Sensory (afferent) pathways carry information toward the CNS, while motor (efferent) pathways carry information away from the CNS.

Question 9

What is the main structural role of astrocytes?

Answer 9

Astrocytes provide structural support by interweaving with neurons and supplying a matrix in which neurons can sit.

Question 10

How do astrocytes support neurons energetically?

Answer 10

Astrocytes provide energy and nutrients to neurons

Question 11

What role do astrocytes play in blood flow?

Answer 11

Astrocytes help control blood flow in the brain.

Question 12

How do astrocytes contribute to neurotransmitter activity?

Answer 12

Astrocytes are involved in the release and reuptake of neurotransmitters in the synapse.

Question 13

What is the main function of microglia in the brain?

Answer 13

Microglia act as brain macrophages, defending the brain against infections.

Question 14

How do microglia defend the brain against infection?

Answer 14

Microglia eliminate bacteria through phagocytosis.

Question 15

What role do microglia play in clearing cellular debris?

Answer 15

Microglia clear debris, such as dead or damaged cells.

Question 16

What is synaptic pruning and how are microglia involved?

Answer 16

Synaptic pruning is the process by which microglia remove excess or unused synapses to optimize brain function.

Question 17

What is the function of oligodendrocytes in the central nervous system?

Answer 17

Oligodendrocytes extend processes that wrap around axons to form the myelin sheath.

Question 18

: What is the role of the myelin sheath?

Answer 18

The myelin sheath protects and supports the axon, and insulates it to improve signal transmission.

Question 19

What are the nodes of Ranvier, and how are they formed?

Answer 19

The nodes of Ranvier are gaps in the myelin sheath where ion channels are concentrated. They are formed by the spacing between oligodendrocytes’ myelin-wrapped axons.

Question 20

What is the primary function of ependymal cells in the central nervous system?

Answer 20

Ependymal cells are involved in the production and flow of cerebrospinal fluid (CSF).

Question 21

How do ependymal cells contribute to brain metabolism?

Answer 21

Ependymal cells assist in brain metabolism and help with waste clearance in the brain.

Question 22

What stem cell-like function do ependymal cells have?

Answer 22

Ependymal cells may have the potential to differentiate into other types of cells, such as astrocytes or oligodendrocytes, though this is still under investigation.

Question 23

What is synaptic transmission?

Answer 23

ynaptic transmission is the process by which neurons transmit chemical or electrical signals across a synapse to communicate with other neurons.

Question 24

How many neurons are estimated to be in the human brain?

Answer 24

here are approximately 80 billion neurons in the human brain.

Question 25

How many synapses are estimated to exist in the cortex alone?

Answer 25

The cortex contains around 0.15 quadrillion synapses.

Question 26

What is the main role of synaptic transmission in the nervous system?

Answer 26

Synaptic transmission allows the passing of signals between neurons, facilitating communication within the central and peripheral nervous systems.

Question 27

What is the first step in synaptic transmission?

Answer 27

Neurotransmitter (NT) synthesis – The neurotransmitter is synthesized in the presynaptic neuron.

Question 28

What happens after neurotransmitter synthesis?

Answer 28

Uptake into a vesicle – The neurotransmitter is taken up into synaptic vesicles for storage.

Question 29

How does depolarization occur in synaptic transmission?

Answer 29

Depolarization via opening of voltage-gated Na+ channels – This causes an influx of Na+ ions, leading to depolarization.

Question 30

What occurs after depolarization in synaptic transmission?

Answer 30

Influx of Ca2+ via voltage-gated Ca2+ channels – Calcium ions enter the presynaptic terminal.

Question 31

What happens when calcium ions enter the presynaptic terminal?

Answer 31

Release of neurotransmitter via exocytosis – The neurotransmitter is released from synaptic vesicles into the synaptic cleft.

Question 32

What happens after the release of neurotransmitters?

Answer 32

Presynaptic receptor activation – The released neurotransmitter may activate presynaptic receptors to regulate further neurotransmitter release

Question 33

What happens after neurotransmitter release?

Answer 33

Postsynaptic receptor activation – The neurotransmitter binds to receptors on the postsynaptic neuron, leading to a response.

Question 34

How is neurotransmitter activity terminated?

Answer 34

Reuptake of neurotransmitter via transporters – Neurotransmitters are taken back into the presynaptic neuron for recycling.

Question 35

What is the final step in the process?

Answer 35

Neurotransmitter metabolism – The neurotransmitter is broken down or metabolized to stop its action.

Question 36

What is the voltage-gated sodium (VGNa+) channel?

Answer 36

VGNa+ channels are specialized ion channels that allow the passage of sodium ions (Na+) across the cell membrane in response to changes in membrane potential.

Question 37

What state is the VGNa+ channel in at a resting membrane potential?

Answer 37

At a resting membrane potential of -70 mV, the VGNa+ channel is in a closed state, preventing the flow of sodium ions.

Question 38

What triggers the opening of VGNa+ channels?

Answer 38

The VGNa+ channels open when the membrane potential becomes more positive (depolarized) to around -50 mV, allowing sodium ions (Na+) to enter the cell.

Question 39

What happens when the VGNa+ channel opens?

Answer 39

When the VGNa+ channel opens, sodium ions (Na+) rapidly flow into the cell, causing further depolarization, which is an essential part of the action potential.

Question 40

What happens after VGNa+ channels open and sodium enters the cell?

Answer 40

The influx of sodium ions leads to the rapid depolarization of the cell membrane, which propagates the action potential along the neuron.

Question 41

How are VGNa+ channels closed after depolarization?

Answer 41

After depolarization, the VGNa+ channel enters an inactive state, where it cannot reopen immediately. This is followed by a recovery period during which the channel returns to its closed state and is ready to open again in response to a new depolarization.

Question 42

What are voltage-gated calcium (VGCa2+) channels?

Answer 42

VGCa2+ channels are ion channels that open in response to changes in membrane potential, allowing calcium ions (Ca2+) to flow into the cell.

Question 43

What is the role of calcium ions (Ca2+) in the cell?

Answer 43

Calcium ions (Ca2+) act as a critical intracellular messenger and are involved in various cellular processes, including changes in membrane potential and vesicle fusion during synaptic transmission.

Question 44

How does calcium influence neurotransmitter release?

Answer 44

The influx of Ca2+ through VGCa2+ channels during depolarization triggers the fusion of synaptic vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synapse.

Question 45

What is the calcium concentration before and after depolarization?

Answer 45

Before depolarization, the intracellular calcium concentration is less than 0.1 μM. After depolarization, it rises to 1-100 μM, allowing for cellular signaling and vesicle fusion.

Question 46

What is the function of Ca2+ during exocytosis?

Answer 46

Calcium binds to proteins involved in exocytosis, facilitating the fusion of synaptic vesicles with the cell membrane and enabling the release of neurotransmitters into the synapse.

Question 47

What triggers the opening of VGCa2+ channels?

Answer 47

VGCa2+ channels open in response to membrane depolarization, allowing calcium ions to enter the cell and initiate downstream signaling events.

Question 48

What is the importance of calcium influx during synaptic transmission?

Answer 48

Calcium influx is essential for vesicle fusion and neurotransmitter release, which are fundamental processes for synaptic signaling and communication between neurons.

Question 49

What are ligand-gated ion channels (LGICs)?

Answer 49

Ligand-gated ion channels (LGICs) are a type of ionotropic receptor that open in response to the binding of a ligand (such as a neurotransmitter), allowing ions to flow through the membrane.

Question 50

What is the structure of ligand-gated ion channels (LGICs)?

Answer 50

LGICs are ion channels that form a pore in the cell membrane, allowing the passage of ions between the extracellular and intracellular spaces. The specific structure can vary among different types of LGICs.

Question 51

: How do LGICs function?

Answer 51

When a ligand binds to the LGIC, it induces a conformational change that opens the ion channel, allowing ions to move down their concentration gradients across the membrane.

Question 52

What is the role of LGICs in postsynaptic receptor activation?

Answer 52

LGICs are involved in postsynaptic receptor activation, where neurotransmitters bind to the receptor, opening the ion channel and enabling ions to flow into or out of the postsynaptic cell, altering its membrane potential.

Question 53

What happens to ions when they pass through LGICs?

Answer 53

Ions move through LGICs down their concentration gradients, contributing to changes in the electrical potential across the membrane and participating in processes like synaptic signaling.

Question 54

What are ligand-gated ion channels (LGICs) also known as?

Answer 54

Ligand-gated ion channels are commonly known as ionotropic receptors.

Question 55

What is the structure of ligand-gated ion channels (LGICs)?

Answer 55

LGICs are ion channels that connect the extracellular environment with the intracellular space, allowing the movement of ions across the membrane. Their structure can vary depending on the type of LGIC.

Question 56

What occurs during postsynaptic receptor activation via LGICs?

Answer 56

When a neurotransmitter binds to a postsynaptic receptor (LGIC), the ion channel opens, allowing specific ions to flow into or out of the postsynaptic cell.

Question 57

How does ion influx or efflux from LGICs affect the cell?

Answer 57

The influx or efflux of ions through LGICs activates intracellular signaling pathways and alters the excitability of the cell, influencing its electrical properties and the transmission of signals.

Question 58

Which ions typically flow through ligand-gated ion channels (LGICs)?

Answer 58

Common ions that flow through LGICs include calcium (Ca²⁺), sodium (Na⁺), chloride (Cl⁻), and potassium (K⁺), which play roles in regulating cell excitability and signaling.

Question 59

How fast is the activation of postsynaptic receptors via LGICs?

Answer 59

The activation of postsynaptic receptors via LGICs occurs within milliseconds, allowing for rapid signaling in the nervous system.

Question 60

How does the activation of LGICs contribute to depolarization?

Answer 60

When LGICs open, ions like sodium (Na⁺) flow into the cell, making the inside of the cell more positive compared to the outside, leading to depolarization.

Question 61

What is depolarization in terms of cellular potential?

Answer 61

Depolarization refers to a reduction in the membrane potential, making the inside of the cell more positive relative to the outside.

Question 62

How does sodium (Na⁺) contribute to depolarization?

Answer 62

When sodium (Na⁺) ions enter the cell through LGICs, it causes the membrane potential to become more positive, which is a key step in initiating an action potential.

Question 63

What is the role of voltage-gated sodium channels (VGNa⁺) in depolarization?

Answer 63

Voltage-gated sodium channels (VGNa⁺) open in response to membrane depolarization, allowing more Na⁺ to enter the cell and further propagate the depolarization, leading to the generation of an action potential.

Question 64

What is the connection between neurotransmission and postsynaptic receptor activation

Answer 64

Neurotransmission involves the release of neurotransmitters that activate postsynaptic receptors, such as LGICs, causing ion influx (e.g., Na⁺) that leads to changes in membrane potential and potentially triggers an action potential.

Question 65

What is hyperpolarization in terms of cellular potential?

Answer 65

Hyperpolarization refers to an increase in the membrane potential, making the inside of the cell more negative compared to the outside.

Question 66

How does the activation of LGICs contribute to hyperpolarization?

Answer 66

When certain LGICs open (e.g., chloride channels), ions like chloride (Cl⁻) enter the cell or potassium (K⁺) exits, making the inside of the cell more negative, leading to hyperpolarization.

Question 67

: How does hyperpolarization prevent an action potential

Answer 67

Hyperpolarization moves the membrane potential further from the threshold required to trigger an action potential, effectively preventing the depolarization needed for an action potential to occur.

Question 68

Why is there no activation of voltage-gated sodium channels (VGNa⁺) during hyperpolarization?

Answer 68

During hyperpolarization, the membrane potential is too negative to reach the threshold required for the VGNa⁺ channels to open, thus no action potential is generated.

Question 69

What effect does hyperpolarization have on cell excitability?

Answer 69

Hyperpolarization decreases cell excitability, making it less likely for the cell to fire an action potential.

Question 70

What happens to cell excitability during depolarization?

Answer 70

During depolarization, the inside of the cell becomes more positive compared to the outside, making the cell more excitable and more likely to generate an action potential.

Question 71

What happens to cell excitability during hyperpolarization?

Answer 71

During hyperpolarization, the inside of the cell becomes more negative compared to the outside, making the cell less excitable and less likely to generate an action potential.

Question 72

How does ion movement contribute to depolarization?

Answer 72

Depolarization occurs when ions like sodium (Na⁺) and calcium (Ca²⁺) flow into the cell, making the inside more positive compared to the outside.

Question 73

How does ion movement contribute to hyperpolarization?

Answer 73

Hyperpolarization occurs when ions like chloride (Cl⁻) enter the cell or potassium (K⁺) exits the cell, making the inside more negative compared to the outside.

Question 74

How does the flow of calcium (Ca²⁺) influence the cell membrane potential?

Answer 74

Calcium (Ca²⁺) influx contributes to depolarization by making the inside of the cell more positive, thus increasing excitability.

Question 75

How does the flow of chloride (Cl⁻) or potassium (K⁺) influence the cell membrane potential?

Answer 75

Chloride (Cl⁻) influx or potassium (K⁺) efflux results in hyperpolarization by making the inside of the cell more negative, thereby reducing excitability.

Question 76

What is an agonist?

Answer 76

An agonist is a drug or an endogenous ligand (e.g., neurotransmitter) that binds to a receptor and induces a physiological effect.

Question 77

What is an antagonist?

Answer 77

An antagonist is a drug that binds to a receptor but does not induce a physiological effect; it prevents the agonist or endogenous ligand from producing an effect.

Question 78

What are the steps in synaptic transmission?

Answer 78

Neurotransmitter (NT) synthesis Uptake into a vesicle Depolarization via opening of voltage-dependent Na+ channels Influx of Ca2+ via voltage-gated Ca2+ channels Release of NT via exocytosis Activation of presynaptic receptors Activation of postsynaptic receptors Reuptake of NT via transporters NT metabolism

Question 79

What is synaptic transmission?

Answer 79

Synaptic transmission is the process by which a neuron communicates with another neuron or target cell. It involves the release of neurotransmitters from a presynaptic neuron, the activation of receptors on the postsynaptic neuron, and the initiation of cellular responses.