Neurons and Glial cells

Each neuron contains

• cell body (soma)

• dendrites

• 1 axon with axon terminals

Cell body

Carries out the living processes of neurons, contains important organelles that help do this:

• nucleus - contain DNA

• Mitochondria - powerhouse of the cell

• ER & GA - produce & release neurotransmitters

Axon

• contains axon hillock - where nerve impulse is generated, not covered in myelin

• can be covered in myelin - insulates and protects fibres, speeds up rate transmission of nerve impulses

• can branch and have own processes

• axon terminal - region where transmitter are stored and released, forms synaptic contacts with other cells

Axon transport

• carries important material between cell body & axon terminals -

• Axon contains microtubules:

  allows transport of substances in both directions:

  • anterograde transport = cell body to terminals, e.g. transmitter

  • retrograde transport = terminals to cell body, e.g. worn-out mitochondria, membrane components

Dendrites

• function: receive signals and bring info to the cell body

• are covered by thousands of tiny dendritic spines - each creating a synapse with axon terminals of other neurons

• play an important role in learning

Synapse

= connections between neurons

• typical neuron of the cortex creates thousands of synapses with other neurons

  • Dendrites & cell body are covered with synapses

  • Axons usually have synapses only at the axon terminal

New connections between neurons = structural foundation for learning

Cortical neurons

• Pyramidal cells

• Purkinje cells

• Granule cells

Pyramidal cells

• long axon

• found in neocortex

Purkinje cells

• similar to pyramidal in shape, but many more dendritic spines

• found in cerebellar cortex

Granule cells

• star-shaped, short axons = make local contacts with other cells

• in sensory cortices

Neuroglia Functions

• create structural support for the brain

• serve to support & protect neurons

• DO NOT carry nerve impulses

Main Types of Glial cells

• astrocytes

• microglia

• oligodendrocytes & Schwann cells

• ependymal cells

Astrocytes

• have their ‘end-feet’ on neurons & blood capillaries

• ‘end-feet’ wrap around capillaries, creating a protective cover = Blood-Brain barrier

• transport nutrients to neurons

Oligodendrocytes

• provide the myelin to neurons in the CNS

• wrap tightly around axons to from the myelin sheath

• speed up the signal/nerve impulse (AP) that travels down the axon

Schwann cells

• cover the axons in the PNS & form the myelin sheath

• make contact with only one axon & provide only a single segment of myelin

Microglia

Phagocytes; clean up the CNS

• can detect damaged/injured or unhealthy neurons and waste products/dead material

• travel towards these and digest them

• eat foreign invaders (bacteria & viruses)

• immune cells of the brain

Ependymal cells

• cover the ventricles in our brain & the central canal of the spinal cord

  • protective barrier between brain & cerebrospinal fluid (CSF)

• cover the choroid plexus of each ventricle

  • Choroid plexus acts as a blood–CSF barrier