Nervous Tissue Flashcards
What does nervous tissue do?
Carries information throughout the body via electrical impulses
What is the function of the nervous system?
Provide rapid and precise communication between different parts of the body via the action of neurones
What are the 2 divisions of the nervous system?
- Central nervous system
- Peripheral nervous system
What are the 2 divisions of the CNS?
- Brain
- Spinal cord
What are the 2 divisions of the PNS?
- Cranial nerves
- Spinal nerves
What are cranial nerves?
- 12 pairs of nerves that extend from the brain stem
What are spinal nerves?
- 31 pairs of nerves - one from each side of the spinal column that radiate outwards to all other body parts
What are the 2 main groups of cells in the nervous system?
- Neurones
- Glial cells
What are neurones?
- Nerve cells
- Functional unit of NS that sends signals around the body
What are glial cells?
- Support cells
- Protect, provide nutrients and immune functions to the neurones
What is the basic structure of a neurone?
- Dendrites
- Large cell body
- Single axon
- Terminal boutons
What are dendrites?
- Highly branched processes extending from cell body
- Form synapses with adjacent neurones
- Respond to external stimuli
- Convey incoming information to cell body
What is a neurones cell body?
- Contains usual cellular organelles
- Large nucleus
- Nissl bodies
- numerous mitochondria
- No centrioles
What does the large nucleus in a neuron cell body do?
- reflects the intense metabolic activity of neurones
What do Nissl bodies do?
They contain ribosomes and so are the site of protein synthesis
Why are there numerous mitochondria in a neurones cell body?
- They spend a huge amount of energy to maintain ionic gradients across membranes
What are neurons unable to do as they have no centrioles?
Unable to divide so limited/no capacity to repair themselves after damage
What do axons do?
- Rapidly propagate signals from cell body towards axon terminals
- Specialised to conduct action potentials
- PNS - myelinated or non-myelinated
- CNS - myelinated
What are the CNS neuroglia?
- Ependymal cells
- Astrocytes
- Microglia
- Oligodendrocytes
What are the PNS neuroglia?
- Satellite cells
- Schwann cells
What epithelium do ependymal cells consist of?
- Simple ciliated cuboidal
What do ependymal cells do?
- Lines fluid-filled cavities in brain and spinal canal
- At luminal surface of the cells they have cilia and microvilli so they help to move spinal fluid around and regulate the composition of spinal fluid
What do ependymal cells not have?
A basement membrane
What do astrocytes do?
- Form the blood-brain barrier
- Regulate the chemical environment
What is the structure of astrocytes?
- Named for their star shape
- Large, numerous glial cells
What is the blood brain barrier?
A semi-permeable membrane separating the blood from the cerebrospinal fluid, and constituting a barrier to the passage of cells, particles and large molecules
What is the function off microglia?
- Phagocytic capacity
- Remove invading microbes and dead cells from CNS
What are oligodendrocytes?
- Predominant neuroglia of white matter
What are the functions of oligodendrocytes?
- Forms myelin sheaths around all CNS axons
- Provide structural and metabolic support
What is the function of Schwann cells?
- Form myelin sheaths around PNS axons
- Provide structural and metabolic support
- Non-myelinated axons are enveloped in cytoplasm of Schwann cells
- Myelinated axons are gradually wrapped by the Schwann cell membrane to create a myelin sheath
What are satellite cells and what is their function?
- Flattened cells that cover the surface of neuronal cell bodies
- Provide structural and functional support
