Structure and ultrastructure of nervous tissue Wk2

Question 1

What is the axon responsible for?

Answer 1

Transmitting electrical impulses to other neurones or cell types via the axon terminal

Question 2

What are cell bodies generally?

Answer 2

• Cell bodies are generally featureless and bald in presentation whilst in others there are variable levels of processes known as dendrites

Question 3

What are primary sensory neurones?

Answer 3

• Neurones without dendrites that detect and convert sensory signals in the environment into electrical messages that are conducued to neurones of the CNS for processing.
• Cell bodies are located in collections or round clumps, which appear as swellings, classically known as ganglia (dorsal root ganglia on spinal nerves of the PNS)
• Cell bodies of neurones with common functions tend to collect together forming what is known as a nucleus (pl nucleus appearing as grey matter) if these are within the CNS

Question 4

What are neurones with dendritic processes on their cell body?

Answer 4

• Have all cell bodies in the CNS
• Involved in all the signalling activities of the CNS: the majority of signals coming from other cells are often received via dendrites that in turn passively transmit them to the cell body

Question 5

Where does the ‘axon proper’ start?

Answer 5

• Initial or initiation segment where action potentials are initiated
• Has specialised anatomy that is not seen elsewhere along length of axon

Question 6

How are bundles in axons different in CNS than PNS?

Answer 6

• CNS axons are known as axonal fibre tracts and some as named and known as fasciculi
• PNS axons are simply known as nerves and are divisible according to whether they carry signals to or from the brain or spinal cord

Question 7

Glia:neurone ratio

Answer 7

Glia originally used to outnumber neurones, but new research indicates 1:1

Question 8

What are anatomical functions of glial cells?

Answer 8

• Surround neurones and hold them in place
• Supply nutrients and oxygen to neurons
• Insulate one neuron from another
• Destroy pathogens and remove dead neurones

Question 9

Main types of glial cells

Answer 9

• Ependymal cells: secrete and energise circulation of cerebrospinal fluid which is contained within meninges and surrounds CNS
• Astrocytes: Have numerous projections which link neurones with their blood supply
• Microglial cells: specialised macrophages which phagocytose pathogens
• Oligodendrocytes (Schwann cells in PNS) insulate neurones by forming myelin that insulates myelinated axons