Khanacademy MCAT Unit 8: Foundation 3: Organ systems - Neural cells

Which two catogeries of neural cells are there ?

Neural cells and Glia (glial cells)

Cell name coming from a Greek word for nerve

Neural cells

Cell name coming from a Greek word for glue

Glial cells

Brain and spinal cord are the …

central nervous system

Nerves coming out of brain and spinal cord are the …

peripheral nervous system

Nerves are made up of … and …

neurons and glial cells

Neural cells are derived from …

neural stem cells or neural crest cells

Neural crest cells and neural stem cells arise in the part of the embryo called the …

ectoderm

Neurons and glia in the CNS are derived from

neural stem cells

Neurons and glia in the PNS are derived from

neural crest cells

What is the main part of the cell called (both in neurons and glia)

The soma or the cell body with the nucleus

What are the processes (thin, long extensions) coming out of the neural cells ?

Axons

What is the function of neurons ?

to process and transmit information

What is the function of glia ?

to support the neurons with processing and transmitting information

How many neurons are there ?

Billions

What are the most common glia ? (5)

Astrocytes

Microglia

Ependymal cells

Oligodendrocytes

Schwann cells

What are some less common glial cells ? (3)

Satelite cells

Olyfactory cells

Sheathing cells

What is the cell body of a neuron ?

Soma

What are the short and long processes (neurites) of a cell ?

Short = dendrites

Short or long = axon with axon terminals

What’s the first part of the axon called ?

The axon inital segment or trigger zone

What is the sheath that large axons are wrapped in ?

Myelin sheath

What are the little gaps called between the segments of myelin on an axon ?

Nodes of Ranvier

Where to the axon terminals come close to ? (4)

Target cells (can be other neurons, muscle cells, gland cells or capillaries = haarvaten)

What is the place called where an axon terminal comes close to a target cell ?

A synapse

What is the main difference in potency between a Neural Stem Cell (NSC) and a Neuroblast? (potency = what a cell is capable of becoming)

Neural Stem Cell (NSC) are multipotent: They can differentiate into neurons or glial cells (astrocytes & oligodendrocytes).

Neuroblasts are unipotent/committed: They can only differentiate into neurons.

How does the development of a neuron go ?

**** Neural crest or stem cell to neural blast to neuron with growth cone

What is the defining structural feature of a unipolar neuron?

It has only one single process (axon) extending from the cell body (soma).

When are unipolar neurons present in humans ?

During development (embryo)

What is a bipolar neuron ?

A soma, a dendrite and an axon

What is a multipolar neuron ?

It has a soman, multiple dendrites and an axon

Which type of neuron is the most common in humans ?

Mutlipolar neurons

What is a pseudo-unipolar neuron ?

Soma with one short process that divides into two long processes.

Which are the two processes called in a pseudo-unipolar neuron ?

The pheripheral axon, bringing information in from the periphery and the central axon bringing information into the central nervous system.

Where is the most common place to find pseudounipolar neurons in the human body?

In the Dorsal Root Ganglia (DRG) of the spinal cord (and some cranial nerve ganglia).

What is a cyton ?

It is a soma or a cell body. Cyton is more specific to the neuron. Cyton is also called perikaryon.

What is the resting membrane potential ?

Without input, most neurons have a stable electrical charge difference across their cell membrane, where it's more negative inside the cell membrane and more positive outside the cell membrane.

Neurons receive excitatory or inhibitory input from other cells or from physical stimuli (like odorant molecules in the nose) throught where does this information come from ?

Input information usually comes in through the dendrites. (Although less often, it'll come in through the soma or the axon.)

… are changes to the membrane potential away from the resting potential (which are small in size and brief in duration, and which travel fairly short distances).

Graded potentials

To what is the size and the duration of a graded potential proportional ?

to the size and the duration of the input

Where does summation, or an adding together of all the excitatory and inhibitory graded potentials at any moment in time occur ?

At the trigger zone, the axon initial segment

The summation of graded potentials is how neurons process their information. When will information be fired down the axon ?

If the membrane potential at the trigger zone crosses a value called the threshold potential.

How is the information fired down an axon ? Which change to the membrane potential ?

An action potential

How are action potentials different than graded potentials ?

Action potentials are different than graded potentials because they're usually the same size and duration for any particular neuron, as opposed to the graded potentials, whose size and duration depends on the size and the duration of the inputs.

How does information cross from an axon to a trarget cell ?

By releasing molecules called neurotransmitters that bind to receptors on the target cell

What part of a cell receives the electrical action potential traveling down the axon and converts it into a chemical signal by releasing those neurotransmitters.

The axon terminal

What are the three parts of a synapse ?

1) The Presynaptic Element (the axon terminal)

2) The Synaptic Cleft (a tiny, fluid-filled physical gap between the two cells (usually about 20 nanometers wide).

3) The Postsynaptic Element (The membrane of the receiving cell (usually a dendrite or cell body of the next neuron, or a muscle cell) which contains the receptors that catch the neurotransmitters.)