Lecture 1 - introduction to CNS Flashcards
(27 cards)
Describe the 3 broad categories of brain function.
Input - It is the process of handling data transmitted to the CNS from sense organs.
Processing - It is the integration of new data with existing information and addition of emotional components
Output - It is the consequential output following cognitive function. It can be voluntary or homeostatic.
What is the function of the cerebral cortex?
It contains 90% of total neuron in the brain. It is responsible for abstract thought, judgement, memory, interpretation and integration of sensory input.
What is the function of the limbic system?
It is responsible for the application of emotion to mental/cognitive functioning. Dysfunction of limbic system manifests itself as emotional disturbance.
What is the function of the basal ganglia?
It is responsible for coordinating voluntary motor activity between cerebellum and cortex. The basal ganglia is separated in corpus striatum, globus pallidum and substantia nigra.
Disorders manifest itself as tremor and spasticity.
What is the function of the thalamus and hypothalamus?
The thalamus acts as a pre processor for sensory information.
The hypothalamus influences ANS function, it controls centres controlling satiety, sleep, thermoregulation, sexual appetite etc.
What does the brainstem do?
The brainstem consist of the visual, auditory and motor centres. The reticular formation monitors and influences input and output of the CNS.
What is the difference between neurology and psychiatry?
Neurology is defined as disorders of movement, intellect and sensation whereas psychiatry is defined as the disorders of the mood, though, behaviour and perception.
example for psychiatry disorders are depression, anxiety, mania, schizophrenia.
examples of neurology disorders are epilepsy, brain tumour, migraine.
Describe a neuron’s structure.
Neurons are the principal signaling unit in the nervous system. Neurons have dendrites (basal and apical), cellbody which hold the nucleus, the axon (initial segment, myelin sheath and node of Ranvier) and nerve terminals (presynaptic terminal)
There are different types of neurons which can be morphological, chemical or physiological.
Morphological differences can be shapes, spines, myelinated or unmyelinated.
Chemical differences is due to using different neurotransmitter systems such as glutamate, GABA, amine (dopamine, 5-HT or noradrenaline), acetylcholine and neuropeptides.
Physiological differences are where they can use neurotransmitter receptor or ion channels.
What are the functions of astrocytes?
They physically support the neurons. Ionic homestasis, neurotransmitter uptake, signalling to neurones, responding to CNS injury(formation of glial scar), support the formation of the blood brain barrier.
What is the function of oligodendrocytes?
They are the myelinating cells of the central nervous systems. Each oligodendrocytes myelinate several axons.
What is the function of microglia?
A microglia is like a macrophage which reside in the CNS. It responds to inflammation and injury of the CNS. It can also engulf foreign bodies.
How do the blood brain barrier regulates the access to the brain?
The cerebral endothelial cells form tight junctions which seal access to the brain and it is inaccessible for polar molecules unless actively transported.
The adherens junction stabilise cell-cell interactions.
Intracellular and extracellular enzymes (monoamine oxidase, alkaline phosphatase, peptidase, nucleotidase and cytochrome P450) provide metabolic activity.
Large molecules such as antibodies, proteins and peptides are transferred to the CNS by receptor mediated transcytosis.
What is the nature of the neuronal signal?
The neuronal signal is electrical in nature which is caused by ions moving across the cell membrane of a neuron.
What is the voltage of the cell membrane and why?
The cell membrane potential is -70mV and this is because all ions are present on both side of the membrane but at different concentrations.
How do ion channels affect the movement of ions?
Ion channels are selective for specific ions and they allow movement of ions down their concentration gradient or electrical gradient.
Ion channels can be open or closed. If it is closed it can be opened using ligands (ligand gated channel) or by change in membrane voltage (voltage gated channel)
How is the electrochemical gradient maintained?
Ion pumps consume ATP to pump 3 Na+ out of the neuron and 2 K+ into the neuron.
How is Cl- pump into or out the cell?
Cl- is regulated by ligand gated channels such as GABA or glycine receptor type
What is grading of responses?
Dendrites receives signals from other neurons which opens the ion channels to produce graded responses. The grading of the responses depends on the volume of neurotransmitter and receptor. The reponses can be inhibitory or excitatory.
What determines an inhibitory response?
An influx of Cl- making the inside of the cell more negative (hyperpolarisation)
What determines an excitatory response?
An influx of Na+ or Ca2+ making the inside of the cell more positive (depolarisation)
Define temporal summation.
It is when 2 or more post-synaptic potential coincide in time.
Define spatial summation.
When there are thousands of input where there is excitatory or inhibitory, it gives rise to a spatial summation.
What happens after an action potential has been fired?
The action potential propagate from the dendrites to the axon where the pre-synapses are located. Then the presynapses will trigger the release of a neurotransmitter into the synaptic cleft where it can act on pre or post synaptically located receptors.
Where are small neurotransmitters synthesised and stored?
They are synthesised in the cytoplasm of the bouton and transported to the presynaptic membrane where it is stored in a vesicle. Examples of small NT are amino acids(glutamate, GABA), monoamine(glycine, noradrenaline, serotonin, dopamine), soluble gases(nitric oxide) and acetylcholine
