lect 12 pt 4

What is signal propagation, also called signal transduction?

It is the process of transmitting a signal through a neuron or to another cell.

What is membrane depolarization also known as?

An action potential, firing, or a nerve impulse.

What does an electrical signal cause along a neuron?

A wave of membrane changes that propagates along the axon.

What happens when the electrical signal reaches the axon terminals?

It activates the vesicles to deliver neurotransmitters into the synaptic gap

In what order does a nerve impulse alternate between electrical and chemical signals?

Electrical → chemical → electrical → chemical.

What are the two main types of nervous tissue cells reviewed in the lecture?

1. Neurons, which transfer information,

2. and support cells, which help maintain nervous tissue.

How many types of support cells are found in the CNS and PNS?

• The CNS has four types of support cells,

• while the PNS has two types.

What are astrocytes?

CNS support cells with small perivascular feet that extend around capillaries.

What does the term perivascular mean?

Peri- means around, and vascular refers to blood vessels, so perivascular means around a blood vessel.

What are the two major functions of astrocytes

• They help maintain the blood-brain barrier and

• maintain the chemical environment of neurons.

What is the blood-brain barrier?

A protective barrier that restricts which substances in the blood can enter brain tissue.

How do astrocytes contribute to the blood-brain barrier?

Their perivascular feet surround capillaries, helping regulate the movement of substances from the blood into brain tissue.

How do brain capillaries contribute to the blood-brain barrier?

They have tight walls, limiting the diffusion of substances out of the blood and into surrounding tissue.

Why is the blood-brain barrier important?

It provides protection by restricting certain substances from entering brain tissue; the instructor notes that many drugs cannot cross it.

How do astrocytes help nourish neurons and remove waste?

Astrocytes transfer nutrients from capillaries to neurons and carry waste products from neurons back toward capillaries.

What are microglia?

Mobile, phagocytic CNS support cells that clean up debris and defend against pathogens.

What does phagocytic mean in the context of microglia?

Microglia engulf and destroy debris or harmful substances.

Why are microglia described as mobile?

They move through nervous tissue rather than remaining fixed in one location.

What are the two main protective functions of microglia?

1. They remove damaged cellular debris

2. and defend nervous tissue against pathogens.

What are ependymal cells?

Ciliated epithelial cells that line the ventricles of the brain and the central canal of the spinal cord.

What are the functions of ependymal cells?

They secrete and circulate cerebrospinal fluid (CSF) within the CNS.

How do the cilia of ependymal cells help circulate cerebrospinal fluid?

Their cilia beat in coordinated waves, helping move cerebrospinal fluid around CNS tissues.

What are oligodendrocytes?

CNS support cells that form myelin sheaths around CNS neurons' axons.

How many neurons can one oligodendrocyte myelinate?

One oligodendrocyte can myelinate portions of multiple neurons.

How do oligodendrocytes form myelin sheaths?

Their cellular extensions reach out to axons and wrap around them repeatedly to form myelin.

What are the two types of support cells in the PNS?

Satellite cells and Schwann cells, also called neurolemmocytes.

What are satellite cells function,

they help protect the cells and regulate their nutrient environment.

What is a ganglion,

A ganglion is a cluster of neuronal cell bodies in the PNS,

How do satellite cells support neurons in ganglia?

They help maintain the neurons' chemical environment, provide nutrients, and remove waste.

what is another name for Schwann cells,

Schwann cells are also called neurolemmocytes

where are satellite cells found?

surround neuronal cell bodies in PNS ganglia,

what happens when vesicles deliver neurotransmitters into the synaptic gap

produces a chemical signal to the next cell or effector organ.