NS 1 - Organisation and basic function Flashcards
3 functional characteristics of the CNS
Spinal cord level
Subcortical level or lower brain
Cortical level or higher brain
What are the functions of the neuronal circuits performed by the SC? (4)
- Walking movements.
- Reflexes to withdraw away from pain source.
- Reflexes that support the body against gravity
- Reflexes that control local blood vessels, GIT wall movements
and urinary excretion.
What is the overall function of the lower brain/ subcortical level?
Subconscious control of body function
Feeding reflexes (salivation and licking the lips) in response to the taste of food - are
controlled by areas in which structures? (5)
medulla, pons, mesencephalon, amygdala, and
hypothalamus.
Emotional responses are controlled by which level of the brain?
Subcortical level/lower brain
What structures make up the subcortical level of the brain? (7)
medulla, pons, mesencephalon, hypothalamus, thalamus,
cerebellum, and basal ganglia.
Where is arterial pressure and respiration controlled?
In the pons
Equilibrium is a combined function of what?
of the cerebellum and the reticular substance of
the medulla, pons, and mesencephalon.
What are the functions of the higher brain/cortical level?
Essential for thought processes and cannot function independently.
* Cerebral cortex store memory
How many neurons are in the CNS?
▪ CNS contain ~ 80 to 100 billion neurons.
Name the major structural features of the neurons
Dendrites, cell body (soma), and axon
What is the cytoplasm in n exon called?
Axoplasm
What structural proteins are in the axoplasm?
Axoplasm contains dense bundles of microtubules and
neurofilaments.
What is the function of the axon transport system?
Axon transport system moves organelles and
macromolecules between the cell body and the axon
terminals.
Differentiate between anterograde/orthograde and retrograde
Axonal transport from the cell body toward the terminals is
called anterograde or orthograde.
▪ Axonal transport from the terminals toward the cell body is
called retrograde.
What is the clinical significance of anterograde and retrograde transport?
Axonal transport is important in the pathogenesis of
some human neurologic diseases.
Explain the rabies virus - site of replication and its use of axonal transport
▪ Rabies virus replicates in muscle tissue at the site of a
bite by a rabid animal and is then transported in a
retrograde direction to the cell bodies of neurons
innervating the muscle.
________________is also transported in a retrograde direction in nerve cells whose axons
terminate at the site of infection.
Bacterium Clostridium tetani
Virus in mucocutaneous nerve endings uses _________________ transport to reach ____________________ and becomes latent
retrograde
dorsal root ganglion
A reactivated virus travels from where to where? Using what transport?
Reactivated virus within the dorsal root
ganglion to become infectious followed by
passage of virus down (anterograde) the axon
to mucocutaneous site.
List the 3 types of glial cells
Astrocytes
* Oligodendrocytes (Schwann cells)
* Microglial cells.
What are the functions of glial cells? (4)
Glial cells control the CNS environment within which neurons function.
Shuttle nutritive molecules from blood vessels to neurons.
- Removal of waste products
- Maintaining the electrochemical surroundings of neurons.
Function of the oligodendrocytes
Function of oligodendrocytes is myelination
What is myelin sheath and what is its function?
Myelin sheath is an electrochemical insulator around
axons in the white matter.
▪ Myelin sheath around an axon greatly increases the
speed of conduction of action potentials along the
axon.
What happens in demyelinating diseases?
Degeneration of oligodendrocytes and their myelin segments
Myelin sheath is an electrochemically insulator around
axons in the white matter.
Loss of myelin results in slower action potential propagation along demyelinated
axons.
Degeneration of the distal axon is called_____________
denervation
Degeneration of the distal axon (denervation) and myelin sheath results in____________________
atrophy of denervated
myofibers (muscle fibres)
What does demyelination result in?
Demyelinating results in random segmental
degeneration of individual myelin internodes
What is a synapse?
▪A Synapse is the junction point at which an electrical response in one
cell is transmitted to another cell.
▪Synapses determine electrical impulse spread through the
nervous system
List the 3 types of synapses
Axodendritic
Axoaxonal
Axosomatic
Define presynaptic facilitation
Neuron exerting powerful excitatory effect on synaptic contact with the axon terminal
Define presynaptic inhibition
Neuron exerting powerful inhibitory effect on synaptic contact with the axon terminal
Repeated use of a synapse can lead to?
Increase in the quantity of transmitter released (long term potentiation(LTP) - synaptic plasticity
Decrease in transmitter release (Long term depression (LTD))
What is the importance of LTP and LTD
Learning and memory storage
What are IPSP and EPSP
EPSP- excitatory post-synaptic potential
IPSP - inhibitory post-synaptic potential
They are graded potentials that only influence the local membrane and then rapidly decay.
Explain resting state of neuron in synaptic integration
Motor nerve cell shown with synaptic boutons of excitatory and inhibitory nerve fibers ending close to it
Explain partial depolarisation
Impulse from 1 excitatory fiber has caused partial (below threshold) depolarisation of a motor neuron
Explain temporal excitatory summation
A series of impulses in one excitatory fiber together produce a suprathreshold depolarisation that triggers an action potential.
Explain spatial excitatory summation
Impulses in 2 excitatory fibers cause 2 synaptic depolarizations that together reach the firing threshold, triggering an action potential
