Chapter 3 Open Neuroscience Initiative

What is the basic structure surrounding a neuron?

The neuron is surrounded by an aqueous cytoplasm and bounded by a cell membrane.

What is the estimated number of neurons in the adult human brain?

The adult human brain is estimated to contain close to 86 billion neurons.

What defines the membrane potential of a neuron?

The membrane potential is the difference in electrical charge between the inside and the outside of a cell, typically around -70 mV in a resting neuron.

How do neurons modify their membrane potential?

Neurons modify their membrane potential through the movement of ions like sodium and chloride across their membranes.

Why are neurons described as "forever" cells?

Neurons are often not replaced once they are developed; the same neurons last throughout an individual's life.

What is the role of dendritic spines?

Dendritic spines serve as input sites where neurons receive signals from other cells.

How do neurons exhibit plasticity?

Neurons change structurally and functionally, such as altering the structure of dendritic spines, to adapt to new information or environmental changes.

What is the role of the cell body or soma in a neuron?

The soma integrates all incoming signals and decides whether to pass on the signal based on cellular computations.

What is an axon's function in a neuron?

The axon transmits electrical signals away from the neuron's cell body to other neurons or muscles.

Describe the axon hillock.

The axon hillock is a specialized part of the cell where the axon joins the soma and is crucial for initiating action potentials.

Question

Answer

What are the primary input sites on a neuron?

The primary input sites on a neuron are the dendrites.

What is the significance of dendritic trees in neurons?

Dendritic trees increase the surface area for receiving signals from other neurons.

How do dendritic spines relate to learning and memory?

Dendritic spines change in response to learning and are thought to store long-term memories.

What is the function of the soma in signal integration?

The soma sums all excitatory and inhibitory inputs to decide whether to fire an action potential.

Describe the structural difference between dendrites and axons.

Dendrites are typically thicker and more branched than axons, which are longer and often thinner.

What is the main structural feature of axons that aids in signal transmission?

The presence of myelin sheaths along the axon speeds up the electrical transmission along the nerve fiber.

What is the role of the nodes of Ranvier in a myelinated axon?

The nodes of Ranvier are gaps in the myelin sheath that facilitate rapid signal conduction via saltatory conduction.

What occurs at the axon terminal?

The axon terminal is where neurotransmitters are released to communicate with other neurons or muscle cells.

How is material transported within an axon?

Material is transported within an axon via microtubules that serve as tracks for motor proteins in both anterograde and retrograde directions.

What is the primary function of myelin?

Myelin insulates axons to increase the speed and efficiency of electrical signal transmission.

Question

Answer

What are the primary functions of astrocytes in the CNS?

Astrocytes help maintain the blood-brain barrier and regulate neurotransmitter levels at synapses.

How do oligodendrocytes support neuronal function?

Oligodendrocytes provide myelin sheaths to CNS neurons, which speeds up electrical signal transmission.

What is the unique role of Schwann cells in the PNS?

Schwann cells myelinate axons in the PNS and also aid in the regeneration of damaged nerve fibers.

Describe the immune function of microglia in the CNS.

Microglia act as scavengers to remove debris, damaged cells, and pathogens, and they respond to CNS injuries.

What is the function of ependymal cells in the CNS?

Ependymal cells line the ventricles of the brain and the central canal of the spinal cord, producing cerebrospinal fluid.

How do astrocytes influence neuronal signaling at synapses?

Astrocytes absorb neurotransmitters like glutamate from synaptic spaces, modifying synaptic strength and neuronal excitability.

Why are oligodendrocytes essential for neural conduction speed?

By myelinating multiple axon segments, oligodendrocytes allow for faster action potential propagation compared to unmyelinated fibers.

In what way do Schwann cells contribute to nerve regeneration?

Schwann cells clear debris and secrete growth factors that guide regrowing axons to their target cells.

How do microglia respond to brain infections or injuries?

Microglia change shape and increase