WEEK 4 LECTURE FINISHED Flashcards
What does the CNS consist of?
Brain
Spinal cord
What does the Peripheral nervous system consist of?
CN’s - 12 pairs
Spinal Nerves - 31 pairs
What are the 2 components of the functional nervous system?
Autonomic nervous system
Somatic nervous system
What does the autonomic nervous system control?
Smooth muscle
Glands
Organs/viscera
What is the function of the nervous system?
Enables the body to react to continuous changes in the internal and external environment
Controls and integrates the various activities of the body e.g. circulation and respiration
What are the main cells of nervous tissue?
2 main cells
- Neurons/nerve cells
- Neuroglia (glia cells), support cells
Nerve cells to neuroglia cells ratio
1:5
What is the structural and functional unit of the nervous system?
The neuron
What are the 3 functional classes of neurons?
Efferent (motor)
Afferent (sensory)
Interneurons
What are the parts of a neuron?
Cell body
Dendrites (carry impulses to the cell)
Axon (Carry nerve impulses away from the cell body)
What are afferent neurons? Describe a typical afferent neuron. Where is the cell body located?
A sensory receptor which generates AP’s in response to a type of stimulus
Cell body has no dendrites, located adjacent to spinal cord.
Long peripheral axon extending between receptor and cell body
Short central axon from cell body to spinal cord, synapses with neurons in spinal cord
What are efferent neurons? What do they do? Where is the cell body located?
• Carry information from the CNS
- ‘e’ = from
- ‘ferent’ = carry
- Transmits instructions from the CNS to effector organs (mm, glands)
- Cell body originates w/n the spinal cord
What are Interneurons? Where are they situated? How many of them do we have approx?
- 99% of all neurons
- Lie entirely w/n the CNS
- 100 billion interneurons
- Inter = between
- Lie between afferent and efferent neurons
What does glial mean?
Glue
What are the 4 main types of neuroglial cells within the CNS? Describe them
- Astrocytes (physically support, neural scar tissue, help transmit nutrients, degrade neurotransmitters)
- Oligodendrocytes (myelin in CNS)
- Microglia (phagocytic, defence)
- Ependymal (line cavities, contribute to CSF, neural stem cells - neurone and glial)
Where are schwann cells found and what do they do?
Peripheral nervous system. They make myelin.
What is myelin? What does it do? What is it made by? What is an interruption between 2 segments of myelin called?
Myelin is a protein and lipid substance which helps by greatly increasing the velocity of impulse conduction.
It gives a fibre a white creamy colour.
Made by oligodendrocytes in the CNS
Made by schwann cells in the peripheral nervous system
Interruption = node of ranvier
MS: What is it?
MS is a progressive disease where there is demyelination of nerve fibres in the brain and spinal cord
Synapses: what do they do? And how do they communicate between with each other?
Neurons communicate with each other at synapses, points of contact between neurons.
Neurons communicate via the release of chemical substances called neurotransmitters which may excite or inhibit the other neuron.
What is a collection of nerve cell bodies in the CNS known as?
Nucleus
What is a collection of axons in the CNS known as?
A tract
What is grey matter?
Nerve cell bodies
What is white matter?
Interconnecting fibre tract systems
How many horns are there in the spinal cord?
4
- Right anterior / ventral horn
- Left anterior/ ventral horn
- Right posterior / dorsal horn
- Left posterior / dorsal horn
What are the meninges? How many types are there?
3 types:
Pia mater (inner most) “tender”
Arachnoid mater “Spider form”
Dura mater “Hard”
What does CSF do? Where is it found?
Surrounds the brain and spinal cord and protects/cushions it.
Found between the pia mater and the arachnoid mater in the subarachnoid space
What are the principle roles of the CNS?
Integrate and coordinates incoming and outgoing neural signals
Carry out higher mental functions (eg thinking and learning)
What does the peripheral nervous system consist of?
Nerve fibres and cells bodies outside of the CNS
Cranial Nerves
Peripheral nerves
How many pairs of cranial nerves are there?
12
How many pairs of spinal nerves are there? Break down into the different areas of the spine e.g. cervical etc
31
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
Where do spinal nerves exit in relation to the vertebra?
Through the intervertebral foramina
Usually exit beneath the corresponding vertebra except in the neck, where the cervical ones pass out above the corresponding vertebra, which is why there is a C8 spinal nerve but no C8 vertebra.
What are the 2 types of peripheral nerves?
Sensory - impulses towards CNS
Motor - impulses away from CNS
What is the connective tissue around peripheral nerves?
» Endoneurium (surrounds the neurolemma cells and axons)
» Perineurium (encloses a bundle of peripheral nerve fibres, provides protection against foreign substances)
» Epineurium thick sheath of loose connective tissue, surrounds nerve bundles (outermost covering, includes fatty tissue, blood vessels and lymphatics)