Chemical Control + Brain Behaviour Flashcards
Q Why does the blood brain barrier make it difficult to study the effect of the diffuse modulatory systems in the brain?
Most neurotransmitters in their active or mature form cannot pass the blood brain barrier (BBB). This alone makes it very difficult to study the effects of the NT of interest. This can be overcome in 2 ways:
- Use a precursor drug that is permeable to the BBB (eg Levodopa, that is converted to dopamine in the nerve terminal.
- Direct injection (cerebroventricular ) of the NT.
Both of these techniques do have multiple limitations that may include: 1. Does sufficient quantities of the precursor reach the neurons of interest or is it rapidly degraded in the periphery or CNS itself? 2. Toxicological limitations, eg side effects, liver toxicity, PNS toxicity etc. 3. Risks associated with injections across a biological membrane, especially via cerebroventricular admin. 4. Will the injected NT reach the neurons of interest or simply remain in the CSF? 5. Ethical concerns.
Some of the chemicals that are used by the brains diffuse modulatory systems are also used in the peripheral nervous systems. These chemicals often have a similar effect in the CNS however it is not necessary that the effect is the same. They are?
Noradrenaline and norepinephrine (Locus Coeruleus nuclei in the brain) • Serotonin - Serotonergic raphe nuclei in the brain: • Dompamine -Dopaminergic substantia nigra and ventral tegmental area: • Acetylcholine (Ach)
Epinephrine and Norepinephrine (Adrenal Gland)
- In the body it is secreted by the adrenal glands and is synthesised in the neurons of the adrenal medulla
- NE is the neurotransmitter in the peripheral ANS. It has a large influence on the storage and metabolisation of glucagon and fatty acids. • Low blood glucose triggers the release of adrenalin into the blood which mobilises glucagon (liver) and fatty acids (fat tissue) and increases the metabolic rate. • High blood glucose triggers the release of insulin that has the opposite effect leading to reduced metabolic rate and storage of glucose.
Q What is the role of NE in the CNS? In your answer compare the similarities to the action of NE in the body.
Most NE activation in the CNS is by new, unexpected, nonpainful sensory stimuli Regulation of attention, arousal, sleep/wake cycles, learning, memory, anxiety (mood) and pain Regulation of brain metabolism in the structures involved in the noradrenergic locus coeruleus (see diagram below) In the PNS, NE is released at the neuroeffector junction by post-ganglionic neurons of the sympathetic division of the ANS. Here it elicits, increases in HR and BP Pupillary dilation, cold, white skin, sweating etc. The locus coeruleus and raphe nuclei are part of the ascending reticular activating system, which awakens the forebrain.The raphe nuclei use serotonin as the neurotransmitter
Consider what happens to the firing of the raphe and serotonin levels when you fall asleep
Both will decrease. Similar to neurons of the locus correleus (LC), serotinergic raphe nuclei fire most rapidly during wakefulness, when an animal is aroused and active. Both these structures, the LC and raphe nuclei comprise the ascending reticular activating system. Serotonin plays a role in alertness and mood. It also plays a role in appetite regulation. People with high levels of serotonin may have a poor appetite. It is also important in the regulation of mood. Anti –depressant Prozac is one of a class of drugs called Specific Serotonin Re-uptake Inhibitors. They work by preventing the act of the neurons that reabsorb serotonin.
Q What is the role of dopamine?
Many and varied the main ones in the brain, are in behavior and cognition, motor activity, motivation and reward, inhibition of prolactin production (involved in lactation), sleep, mood, attention, and learning. Dopaminergic neurons (i.e., neurons whose primary neurotransmitter is dopamine) are present chiefly in the ventral tegmental area (VTA) of the midbrain, substantia nigra pars compacta, and arcuate nucleus of the hypothalamus Function: Together with noradrenergic system, comprise the ascending reticular activating system. Raphe system particularly involved in sleep/wake cycles. Activation: New, unexpected, nonpainful sensory stimul
Q What is acetylcholine’s role in the central nervous system and which two diffuse modulatory systems use it?
Similar to noradrenergic and serotinergic, it is implicated in general brain excitability during arousal, and sleep-wake cycles. Also has a role in memory formation and learning. Basal forebrain complex, the cholinergic neurons lie scattered among several related nuclei at the core to the telencephalon and basal ganglia. Pontomesencephalotegmental cholinergic complex. These are AChutilizing cells in the pons and midbrain tegmentum, that excite sensory relay nuclei in the thalamus.
1.The sensory nerve of the right hand is a) An efferent axon and ipsilateral to the right ear b) An efferent axon and contralateral to the right ear c) An afferent axon and ipsilateral to the right ear d) An afferent axon contralateral to the right ear e) Part of the central nervous system
c) An afferent axon and ipsilateral to the right ear
- The Noradrenergic diffuse modulatory neurons have their cell bodies in the : a) locus coeruleus b) substantia nigra c) raphe nuclei d) medulla e) cerebellum
) locus coeruleus
- Lysergic acid diethylamide (LSD) is extremely potent psycho-active drug. It works as: a) a potent agonist at the serotonergic receptors on the presynaptic terminals of the raphe neurons causing reduced firing of the raphe neurons and reduced serotonin. b) an antagonist on the serotonergic diffuse modality system causing increased firing of the raphe neurons. c) increases the bodies serotonin levels and thus causes a dream like state d) reduces the bodies serotonin levels and reduces the firing of the raphe neurons. e) a and d are both correct.
e) a and d are both correct.
- The anterior lobe of the pituitary contains: a) magnocellular neurosecretory cells b) Parvocellular neurosecretory cells c) no neurons d) releases cortisol directly into the blood stream e) releases oxytocin into the blood stream
c) no neurons
. The dopaminergic diffuse modulatory neurons have their cell bodies in the: a) locus coeruleus b) substantia nigra c) raphe nuclei d) medulla e) cerebell
b) substantia nigra
- Serotonin and its’ diffuse modality system are: a) part of the ascending reticular activating system b) arouses and awakens the forebrain c) fires during wakefulness d) lie in nine clusters e) all options are correct
e) all options are correct
Where do the axons of the parasympathetic division originate from?
(Cranial and sacral sections of the spinal cord).
What are the 3 components of the nervous system that operate in expanded space & time?
‘expanded space & time’ = fancy way of saying that there are mechanisms in which brain can make changes in the body by broadcasting messages to larger extent than just single synapse (cell to cell communication). We recognise this form of broadcast in 3 forms::
- Hypothalamus talking to body by sending hormones in blood to produce required action for homeostasis
- Hypothalamus talking to autonomic nervous system in order to control internal organs, blood vessels and glands.
- Diffuse modulatory systems of the brain (believed to regulate arousal and mood) = whole bunch of cells in the CNS which have axons that can trigger responses that are sustained due to presence of metabotropic (cascade = long) postsynaptic receptors.
How does the hypothalamus communicate with the pituitary gland?
The hypothalamus has cells in the periventricular area which talks to the pituitary gland
What 2 responses occur in order for stable fluid balance and normal blood volume in the body when there is a drop in BP?
Communication between the hypothalamus and kidney helps our blood volume and pressure stay normal. 2 responses happen when blood volume/ BP drops :
What is the difference between the sympathetic and parasympathetic ANS (responses and location of preganglionic neurons) ?
What is the main preganglionic neurotransmitter of the ANS and it’s effect?
ACH (for both PNS &SNS) is main neurotransmitter. It can elicit different effects by binding on different receptors: nicotinic/muscarinic/ metabotropic (G coupled
What is the role of postganglionic neurotransmitters?
- Postganglionic neurons = stimulate ANS motor activity (gland secretion, contraction/relaxing of sphincters) via different neurotransmitters:
How can you predict effects of drugs ?
BY looking at whether they interact with cholinergic or noradrenergic systems
What are the 4 diffuse modulatory systems?
- NA (Locus coeruleus)
- 5HT (raphe nuclei)
- DA (Substantia Nigra + Ventral Tegmental Area)
- Cholinergic (Basal Forebrain + Brain stem parts)
Drugs and DMS
- Battlefield trauma victims who have lost large volumes of blood often express a craving to drink water. Why?
When your blood volume drops 2 events happen:
