Neurons - Structure

What does neural tissue mostly consist of?

• Neuroglia

• Neurons (nerve cells)

What are the two main cell types in neural tissue?

• Neuroglia

• Neurons (nerve cells)

What is the role of neuroglia?

• Support neuron development and function

• Nourish neurons

• Protect neurons

• Insulate neurons

• Provide structural support

How many types of neuroglial cells are there?

• Six

Which neuroglial cells belong to the PNS?

• Satellite cells

• Schwann cells

Which neuroglial cells belong to the CNS?

• Ependymal cells

• Astrocytes

• Oligodendrocytes

• Microglia

What is the main function of neurons?

• Perform communication by generating electrical signals (graded potentials and action potentials)

What do neurons conduct?

• Sensory and motor information from one part of the body to another

What do neurons require for survival?

• Oxygen

• Glucose

Can neurons divide and replace themselves if destroyed?

• No

What are the four structural components of a neuron?

• Dendrites

• Cell body

• Axon

• Axon terminals

What are dendrites?

• Short processes

• Main receptive/input region of a neuron

What do dendrites do?

• Act as sensory receptors

• Detect stimuli

• Receive information from other neurons

• Convert information into graded potentials toward the cell body

What does the cell body contain?

• Nucleus

• Organelles such as ribosomes

What does the cell body do?

• Receives information

• Converts information into graded potentials

• Integrates graded potentials

• Conveys information to the initial segment of the axon

What is the axon?

• A single process connected to the cell body at the axon hillock

What is the function of the axon?

• Conducting region

• Generates and conducts action potentials from initial segment to axon terminals

What produces myelin?

• Schwann cells

• Oligodendrocytes

What does myelin do?

• Increases speed of signal conduction

What separates segments of myelin?

• Nodes of Ranvier (internodes)

What is the speed difference between myelinated and unmyelinated axons?

• Unmyelinated ~2 m/s

• Myelinated up to ~150 m/s

What happens when the immune system destroys CNS myelin?

• Multiple sclerosis

What are the effects of multiple sclerosis?

• Slowed conduction

• Eventual complete stop

• Loss of sensation

• Muscle paralysis

What do axon terminals form?

• Synapses with another cell (neuron, muscle, or gland)

What is the role of axon terminals?

• Secretory region of the neuron

What do axon terminals contain?

• Synaptic vesicles storing neurotransmitters

What do neurotransmitters do?

• Carry information from one neuron to another or to a muscle or gland

What do dendrites do?

• Receive information

• Convey graded potentials toward the cell body

What does the cell body do?

• Receives information

• Integrates information

• Sends information to the axon

What does the axon do?

• Conducts information as an action potential to the axon terminals

What does the myelin sheath do?

• Increases speed of signal conduction

What are nodes of Ranvier?

• Gaps between myelin segments

What do axon terminals do?

• Release neurotransmitters to transmit information to another neuron, muscle or gland

How are neuron cell bodies organised in the CNS?

• Nuclei (nucleus)

How are neuron cell bodies organised in the PNS?

• Ganglia (ganglion)

What are bundles of neuron axons called in the CNS?

• Tracts

What are bundles of neuron axons called in the PNS?

• Nerves