Nervous System - Neurons and Nerves Flashcards
What is the nervous system divided into
- Central nervous system.
- Peripheral nervous system.
What does the central nervous system consist of?
- Brain.
- Spinal cord (spinal medulla).
What does the peripheral nervous system consist of?
- Cranial nerves.
- Spinal nerves.
- Associated ganglia.
What does both central and peripheral nervous system have?
Two parts:
1. Somatic.
2. Autonomic.
What is somatic concerned with?
Innervation of skeletal muscle (along efferent pathways) and the transmission of sensory information (along afferent pathways).
What is the autonomic nervous system concerned with?
Control of cardiac muscle, smooth muscle, glands (involving afferent and efferent pathways.
What is the functional and structural unit of the nervous system called?
Nerve cell or neutron.
What does a neutron consist of?
- Cell body - contains nucleus.
- Nerve fibres - processes (i.e. axon/dendrite).
What is an axon?
Single cytoplasmic process. Long.
How does the axon conduct nerve impulses?
Away from the cell body, it can also give off collaterals.
What are dendrites?
Multiple cytoplasmic processes. Short.
What do dendrites do?
Expand the surface area of the cell body for the reception of stimuli.
What are synapses?
Sites on the cell body or its processes where chemical transmitters can enable nerve impulses to be handed on from one neuron to another.
What are neuroendocrine cells?
Classical neurotransmitters that have endocrine functions as well and can be found in other areas to the nervous system.
What is a diffuse neuroendocrine system?
- Neuroendocrine cells.
- Neuromediators.
- APUD cells (amine precursor uptake and decarboxylation).
What do cell bodies with similar tendencies do?
Group themselves together, forming nuclei within the CNS and ganglia outside it.
What are tracts?
Processes run together in bundles in the central nervous system.
What are nerves?
Processes that run together outside the brain and spinal cord.
What are neuroglia cells?
Other cells in the nervous system that have other functions but do not function and have the excitability oor conductivity possessed by neurone.
What are the types of neuroglia cells?
- Astrocytes.
- Oligodendrocytes.
- Microglial cells.
Where do atrocities and oligodendrocytes develop from?
Ectoderm from the neural tube.
What does the microglial cell do?
Phagocytic cell of the nervous system.
Where do microglial cells develop from?
Mesoderm.
Where do satellite cells of ganglia in the CNS develop from?
Ectoderm of the neural tube.
Where do Schwann cells of the PNS develop from?
Ectoderm of the neural tube.
What can nerve fibres be?
- Myelinated.
- Unmyelinated.
Where is myelin formed in the CNS?
Oligodendrocytes.
Where is myelin formed in the PNS?
Schwann cells - neurolemmocytes.
What are nodes of ranvier?
Gaps in the myelin sheath
What does white matter of the nervous system consist of?
Nerve fibres.
What does grey matter of the nervous system consist of?
Cell bodies.
How many spinal nerves are there?
31.
What are the spinal nerves?
- Cervical - 8.
- Thoracic - 12.
- Lumbar - 5.
- Sacral - 5.
- Coccygeal - 1.
What are the groups of nerve fibres?
- Group A - up to 20micro meters in diameter.
- Group B - up to 3 micro meters in diameter.
- Group C - up to 2 micro meters in diameter.
What are the subtypes of group A nerve fibres?
- Alpha - 12-20 micro meters - moto and proprioception (Ia and Ib).
- Beta - 5-12 micro meters - touch, pressure, proprioception (II).
- Gamma - 5-12 micro meters - fusimotor to muscle spindles (II).
- Delta - 1-15 micro meters - touch, pain and temperature (III).
Describe group b nerve fibres?
- Up to 3 micrometers in diameter.
- Myelinated.
- Pre-ganglionic autonomic.
Describe group c nerve fibres?
- Up to 2 micrometers in diameter.
- unmyelinated.
- Post-ganglionic autonomic, touch and pain.
Where is each spinal nerve formed?
Union of anterior (ventral) and posterior (dorsal) root. These emerge from the side of the spinal cord.
Where does the union of anterior and posterior root occur?
Within the intervertebral foramen of the appropriate nerve, it occurs immediately distal to the swelling on the posterior root - indicates site of posterior root ganglion (also within the foramen).
What does the anterior root contain?
Efferent motor fibres for skeletal muscle. Also contains small number of unmyelinated affrenet pain fibres (started in posterior root and go into anterior root).
What does the posterior root contain?
Afferent sensory fibres, the cell bodies are in the posterior root ganglion. No synapses in these ganglia.
What does the spinal nerve divide into?
- Anterior ramus.
- Posterior ramus.
What does the anterior ramus form?
The great nerve plexuses;
1. Cervical.
2. Brachial.
3. Lumbar.
4. Sacral.
What binds the individual fibres (spinal nerve) together to form one nerve?
Connective tissue.
What surrounds the bundle of nerve fibres?
Perineurium - condensation of connective tissue. Except the small nerve vessels.
What is the epineurium?
Looser tissue that binds the fascicles into a single nerve.
What is the endometrium?
Fine fibrils that surround every single nerve fibre.
What is the proportion of nerve to connective tissue?
In bigger nerve vessels the connective tissue is more than the nerve itself, whereas in smaller nerve fibres the amount of neural tissue is greater than CT.
What is the arterial supply of peripheral nerve trunks in limbs?
Branches from local arteries.
What nerves does the inferior gluteal artery supply?
Sciatic nerve.
What nerve does the common interosseous arteries supply?
Median nerve.
