Neurons & Glial Cells –

Neuron

Functional cell of the nervous system that transmits electrical and chemical signals; found in both CNS and PNS.

Glial Cells

Supporting cells that protect, nourish, and assist neurons; do not transmit electrical signals.

Types of Glial Cells in CNS

Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells.

Types of Glial Cells in PNS

Schwann cells and Satellite cells.

Astrocyte

CNS glial cell; supports neurons, forms the blood–brain barrier, provides nutrients, and maintains chemical balance.

Oligodendrocyte

CNS glial cell; forms myelin sheaths around multiple axons, increasing the speed of nerve impulses.

Microglia

CNS glial cell; acts as immune defense, removes waste and dead cells by phagocytosis.

Ependymal Cell

CNS glial cell; lines brain ventricles and spinal cord canal, produces and circulates cerebrospinal fluid (CSF).

Schwann Cell

PNS glial cell; forms myelin around a single axon segment and helps repair damaged peripheral nerves.

Satellite Cell

PNS glial cell; surrounds neuron cell bodies in ganglia, regulates nutrients, and maintains the chemical environment.

Myelin Sheath

Protective fatty covering formed by oligodendrocytes (CNS) or Schwann cells (PNS); speeds up signal transmission.

Which glial cells form myelin in the CNS?

Oligodendrocytes.

Which glial cells form myelin in the PNS?

Schwann cells.

Which glial cells help repair damaged nerves?

Schwann cells (in the PNS).

Which glial cell acts like an immune cell in the CNS?

Microglia.

Which glial cells line the brain ventricles and produce CSF?

Ependymal cells.

Which glial cells maintain the blood–brain barrier?

Astrocytes.

Which glial cells surround neuron cell bodies in ganglia?

Satellite cells (in the PNS).

CNS includes which structures?

Brain and spinal cord.

PNS includes which structures?

Nerves outside the brain and spinal cord.

Structural Types of Neurons

Multipolar, Bipolar, and Unipolar.

Multipolar Neuron

Most common neuron type; has one axon and many dendrites; found in brain and spinal cord; motor neurons are multipolar.

Bipolar Neuron

Has one axon and one dendrite; found in special sense organs such as the retina of the eye and olfactory area.

Unipolar Neuron

Has one process that splits into two branches; found in sensory neurons of the PNS (touch, pain, temperature).

Functional Types of Neurons

Sensory (afferent), Motor (efferent), and Interneurons.

Sensory (Afferent) Neurons

Carry impulses from sensory receptors to the CNS.

Motor (Efferent) Neurons

Carry impulses from the CNS to muscles or glands.

Interneurons

Connect sensory and motor neurons within the CNS; responsible for processing and integration.

Three Functional Regions of a Neuron

Receptive region, Conductive region, and Secretory region.

Receptive Region

Includes dendrites and cell body; receives incoming signals and converts them into electrical impulses.

Conductive Region

Includes the axon; conducts action potentials away from the cell body toward axon terminals.

Secretory Region

Includes axon terminals (synaptic knobs); releases neurotransmitters to communicate with the next neuron, muscle, or gland.

What is the correct signal pathway in a neuron?

Receptive region → Conductive region → Secretory region.