CNS Transmission Flashcards by Srishti D

What are the sensory inputs?

External stimuli
- Sound
- Sight
- Smell
- Touch
- Taste
Internal stimuli
- Pressure
- O2/CO2
- Temperature
- pH

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What is an action potential?

Electrical signal along nerve

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What is a neurotransmitter?

Chemical signal at nerve ending

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What is the role of Ca at the pre-synaptic terminal?

Influx of Ca
Synaptic vesicles release neurotransmitter into synapse
Receptors detect and bind neurotransmitter

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What is the main pre-ganglionic autonomic neurotransmitter and receptor?

Acetylcholine

Nicotinic receptors

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What is the main sympathetic neurotransmitter and receptor?

Noradrenaline

a- and b-adrenoceptors

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What is the main parasympathetic neurotransmitter and receptor?

Acetylcholine

Muscarinic receptors

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What is the main somatic neurotransmitter and receptor?

Acetylcholine

Nicotinic receptors

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What are the requirements for chemical neurotransmission?

Synthesis/storage
- Vesicular content
Release
- Na and K ion channels
- Ca influx
Inactivation
- Uptake
- Metabolism
Receptors
- Pre-junctional
- Post-junctional

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How is noradrenaline inactivated at the synapse?

Neuronal uptake - predominant removal
Extraneuronal uptake
Metabolism - very small contribution

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What is the pre-junctional receptor for noradrenaline?

a2 receptor

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Can drugs with peripheral actions also have effects on the CNS?

Yes, and dramatic ones, too

But only if they cross the BBB

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Describe the uptake of noradrenaline at the synapse

Neuronal
- High affinity
- 90-95%
Extraneuronal
- Low affinity

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What does cocaine do at the synapse?

Block neuronal uptake of NA

Increased response when nerves activated

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Does cocaine have dose-response effects?

Yes
South American Indians chewed leaf
- Slow absorption
- Low concentration
- Relief from
   - Fatigue
   - Hunger
   - Altitude sickness
- Pleasant subtle sense of well being
- Psychological dependence
Western society snorts, smokes, injects
- Fast absorption
- High concentration
- Intense euphoria
- Craving for more drug
- Psychological and physical dependence
- Psychotic symptoms, depression, anxiety, fatigue
- Peripheral effects: hypertension, tachycardia, coronary vasospasm, dysrhythmia, convulsions

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What does amphetamine do at the synapse?

Displace noradrenaline from storage vesicles
- NA released even during low activity
Competes for uptake receptors

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What are the functions associated with noradrenaline?

Stimulant
Mood
Appetite
Cardiovascular

What are the catecholamines?

Noradrenaline
Dopamine
Adrenaline

What type of chemical is serotonin?

Amine

What are the amino acid neurotransmitters?

GABA
Glutamate
Glycine
Aspartate

What are the peptide neurotransmitters?

Opioids
NPY
CCK

What is a gaseous neurotransmitter?

Nitric oxide

Which neurotransmitter, unlike others, is made on demand?

Nitric oxid

What is the distribution of neurotransmitters?

Some widespread

Others highly localised

Describe catecholamine synthesis

EC: Tyrosine IC: Tyrosine hydroxylase > L-DOPA > doa decarboxylase > dopamine Vesicle: Dopamine-b-hydroxylase > NA > phenyl-ethanolamine-N-methyl transferase > adrenaline

In which cells is adrenaline synthesised?

Adrenal chromaffin cells

Which nerves synthesises dopamine only?

Dopaminergic nerves

Where are some areas of the brain to which noradrenergic pathways project?

Cerebellum Caudal raphe nuclei Thalamus

Where are some areas of the brain to which dopaminergic pathways project?

Striatum | Pre-frontal cortex

What are some of the pathways in which dopamine is involved?

``` Movement - Parkinson's: depletion of dopamine in basal ganglia Behaviour: - Schizophrenia: changes in dopamine rich areas like: - Frontal cortex - Basal ganglia - Temporal lobe Dependence: - Dopamine actions in nucleus accumbens and ventral tegmental area Pituitary function - Prolactin secretion Vomiting - Chemoreceptor trigger zone outside BBB - Less important ```

What neurotransmitter uptake does cocaine block?

Noradrenaline Dopamine Serotonin

What is cocaine's dopaminergic action linked to?

Dependence

What type of channel does cocaine also block?

Na channels | Happens at much higher concentrations

Can a synapse be excitatory AND inhibitory?

No, can only be one or the other

Can a neurotransmitter be excitatory AND inhibitory?

Yes, depending on which receptor is present

What type of receptor is a nicotinic receptor?

Ligand-gated ion channel Excitatory Na influx driven depolarisation

What type of receptor is a GABA A receptor?

Ligand-gated ion channel Inhibitory Cl influx driven hyperpolarisation

What are post-synaptic receptors responsible for?

Action potential generation/modulation

What are pre-synpatic receptors responsible for?

Transmitter release

What are neurotrophic factors secreted by glial cells involved in?

Development | Survival

What is the role of glia in neurodegenerative diseases?

Loss of neuroprotective factors | Toxic insult

What complicates the rational approach to identifying transmitter levels in disease

More than one transmitter usually involved One transmitter involved in many pathways Secondary/adaptive responses Effect of transmitter levels on - Synthesis - Receptor expression - Transporter expression