Neurons and Neuroglia: Structural and Functional Classifications in the Nervous System

What are the 3 structural classifications of neurons?

Multipolar, Bipolar, and Unipolar neurons

Structural classifications are based on what?

The number of processes extending from the soma (cell body)

What is a multipolar neuron?

A neuron with one long axon and multiple dendrites

Which type of neuron is most common?

Multipolar neuron

What is a bipolar neuron?

A neuron with one branching axon and one dendrite

Are bipolar neurons common or rare?

Very rare

Where are bipolar neurons usually found?

Special sense organs (such as the eye)

What is a unipolar neuron?

A neuron with only one process (an axon)

Where are unipolar neurons mainly found?

Peripheral Nervous System (PNS)

Functional classifications are based on what?

The direction a message travels in relation to the CNS

What is another name for sensory neurons?

Afferent neurons

What do sensory neurons do?

Carry impulses from sensory receptors to the CNS

Sensory neurons are usually what structural type?

Unipolar

What is another name for motor neurons?

Efferent neurons

What do motor neurons do?

Carry impulses from the CNS to muscles or glands

Motor neurons are usually what structural type?

Multipolar

What is another name for interneurons?

Association neurons

What do interneurons do?

Transmit impulses within the CNS

What percentage of neurons are interneurons?

Over 99%

Interneurons are usually what structural type?

Multipolar

What are neurons?

Main cells of the nervous system that send impulses (messages)

Approximately how many neurons does the body have?

Billions

What are neuroglial cells (glia)?

Support cells that fill spaces between neurons

What does glia mean?

Glue

Are neuroglial cells larger or smaller than neurons?

Smaller

What neuroglial cells are found in the CNS?

Astrocytes, Microglia, Ependymal cells, Oligodendrocytes

What neuroglial cells are found in the PNS?

Schwann cells and Satellite cells

Which neuroglial cells are the largest and most numerous?

Astrocytes

What do astrocytes do?

Anchor neurons to blood capillaries and provide oxygen and nutrients

What do microglial cells do?

Sense and approach injured neurons

What else do microglial cells do?

Phagocytose bacteria and debris

What do ependymal cells do?

Use cilia to circulate cerebrospinal fluid around the brain and spinal cord

What do oligodendrocytes do?

Form the myelin sheath in the CNS

What do Schwann cells do?

Form the myelin sheath in the PNS

What do satellite cells do?

Surround neuron cell bodies

What else do satellite cells do?

Regulate oxygen, CO2, and nutrient levels

What are the three main functions of the nervous system?

Sensory input, integration, and motor output

What is sensory input?

Sensory receptors gather information and send it to the brain

What is integration?

The brain processes and interprets sensory information

What is motor output?

Messages are sent from the brain to muscles or glands to produce a response

What are the two major divisions of the nervous system?

CNS and PNS

What does CNS stand for?

Central Nervous System

What structures make up the CNS?

Brain and spinal cord

What is the CNS considered?

Integration and control center

What does PNS stand for?

Peripheral Nervous System

What structures make up the PNS?

Nerves extending from the brain and spinal cord

What are spinal nerves?

Nerves going to and from the spinal cord

What are cranial nerves?

Nerves going to and from the brain

Another name for the sensory division?

Afferent division

What does Afferent mean?

Arrives at the brain

What does the sensory division do?

Delivers messages from the senses to the brain

Sensory division = input or output?

Input

Another name for the motor division?

Efferent division

What does Efferent mean?

Exits the brain

What does the motor division do?

Sends messages from the brain to muscles and glands

Motor division = input or output?

Output

What does the somatic nervous system control?

Skeletal muscles

Is the somatic nervous system voluntary or involuntary?

Voluntary

What does the autonomic nervous system control?

Smooth muscle, cardiac muscle, and glands

Is the autonomic nervous system voluntary or involuntary?

Involuntary

What are the two divisions of the autonomic nervous system?

Sympathetic and Parasympathetic

What is the sympathetic division known for?

Fight-or-flight response

What does the sympathetic division do?

Activates body systems

What is the parasympathetic division known for?

Rest and digest

What does the parasympathetic division do?

Calms body systems down

What is another name for the cell body?

Soma

What does the cell body contain?

Organelles

What does the cell body produce?

Proteins and molecules needed for nerve impulses

What do dendrites do?

Receive impulses from previous neurons

Describe dendrites.

Short and highly branched

What does the axon do?

Carries impulses away from the soma toward the next neuron

What are axon terminals?

Fine projections at the end of an axon that pass impulses to the next neuron

What are synaptic end bulbs?

Structures that store neurotransmitters

What is the axon hillock?

Where the axon joins the cell body

What is the myelin sheath?

A lipid layer that insulates the axon

What is the function of myelin?

Speeds transmission of action potentials

What do Schwann cells produce?

Myelin sheath in the PNS

What are Nodes of Ranvier?

Gaps in the myelin sheath

Why are Nodes of Ranvier important?

Nerve impulses skip between them, increasing speed

What do axons do?

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