Week 5: T2 (2) Slow & Complex: metabotropic & neuroendocrine inputs Flashcards
How do neurons self-regulate? or What are the intracellular mechanism of regulation?
Common mechanisms with other cells: 1. Self regulation 2. External/environment input Neuron specific mechanism: 1. Metabotropic communication 2. Neuroendocrine communication
What are neuron-specific mechanism of regulation, and how do they effect the cell?
Metabotropic & neuroendocrine.
altering complex intracellular chemical pathways, can effect the differential expression of cellular proteins through signalling to DNA
Compare metabotropic & ionotropic inputs.
Similarities: bind to neuron receptors.
Differences:
Activation: activating ion pumps vs. secondary messengers
Trigger: Triggering changes in ion concentration (may cause depolarization) vs. triggering changes in cellular chemistry (may cause changes in gene expression).
Number: ubiquitous 100 billion vs. specific and relatively few, about 1/4 each.
What are the four metabotropic neurotransmitter, how many are there?
Dopamine Serotonin Noradrenaline Acetylcholine Each about 1/4 of a million.
Describe the four dopamine pathways?
Mesolimbic: originates in the brain stem to the midbrain (nucleus accumbens).
Mesocortical: from brain stem to PFC.
Nigrostriatal from the substantia nigra (brain stem to midbrain.
Tuberoinfundibular originates int he hypothalaums – to brain stem.
Where does dopamine originate from?
Two areas in the brain stem:
1. VTA (ventral tegmental area)
2. Substantia Nigra
And Hypothalamus
What is the origin and terminus of the mesolimbic pathway?
origin: VTA
Terminus: midbrain (striatum/nucleus accumbens
What is the origin and terminus of the Mesocortical pathway?
Origin: Ventral tegmental area (VTA)
Terminus: Prefrontal cortex
What is the origin and terminus of the Nigrostriatal pathway?
Origin: Substantia Nigra (Brain Stem)
Terminus: Midbrain
What is the origin and terminus of the Tuberoinfundibular pathway?
Origin: Hypothalamus
Terminus: Brain stem
What is the limbic system?
The limbic system is driving raw emotions, anger, fear, happiness,.emotional processes.
A deep part of the brain, subcortical, under the cortex. Hard to point out if we cut open the brain. It is phylogenetically. Sits in the ‘deep’ subcortical part of the brain
What does phylogenetically mean?
Ancients part of the brain such as the limbic system, i.e., has been in our brain in a very long time on an evolutionary timescale.
What parts constitute the brainstem?
The hindbrain and midbrain.
Where are the thalamus and hypothalamus located?
The diencephalon, which is the part of the forebrain that is not the lobes, or cerebellum, or brainstem.
What are the functions the cerebellum?
Part of the hindbrain, (with the midbrain makes the brain stem). Motor & balance. Increasingly recognised as important in learning. It’s adjacent to the brain stem. Does not received metabotropic input.
What is the nucleus accumbens
Part of the limbic system. Part of the mesolimbic dopaminergic pathway (terminus)
What is the ventral tegmental area?
Part of the brain stem. Part of the mesolimbic dopaminergic pathway (origin)
What does the mesolimbic dopaminergic pathways regulate?
Two parts of the limbic system: reward & salience.
Reward: Neurons with dopamine input keep the reward processing work well.
Salience: evaluate stimuli around us very rapidly and come to a decision about it (threaten or not)
How dysfunction of the mesolimbic system reflect in psychosis?
In psychosis dysfunction of the mesolimbic system does not effect the reward processing part. Rather, overactivity of the system, i.e., too much dopamine, cause deregulation of cells. people become less effective at weighing up situations appropriately, prone to paranoid interpretation; people misinterpret the world around them. Drugs of abuse such as amphetamines also activate the system. . Drugs stimulate the reward processing, but long term, it can begin dysregulate the salience part and cause psychosis.
What is the prefrontal cortex?
From evolutionary perspective, the final part of the human evolution that distinguishes us from all other animals, what makes us human, thought, feeling. Relies on dopamine input.
What role does dopamine play in the mesocortical system?
Helps frontal lobe functions, i.e., as cognition, motivation, social engagement
How dysfunction of the mesocortical system reflect in psychosis?
Make the PFC hypoactive, reduced stimulation of the PFC causes negative symptoms of psychosis, such as: social withdrawal and cognitive impairment.
Describe the pathway of the nigrostriatal dopaminergic pathway.
From mid brain, specifically, Substantia Nigra to the basal ganglia. Antipsychotic medication can effect this pathway and cause a range of movement problems.
What is the basal ganglia involved with?
Initiation of movements. Degenerates in Parkinson’s disease.
Describe the tuberoinfundibular pathway.
Part of the hormonal axis, the hypothalamic Pituitary Axis (HPA). Antypschotic medication can adversely affect the pathway and cause side effects, hormonal problems.
What is the amygdalae involved with?
Fearful memory.
From evolutionary viewpoint assists survival; help avoid negative, aversive, experiences. We have two. It is related to the hippocampi structure. Thought is linked with a stimulus. Unwanted thought keeps recurring
What are the characteristics of the Hippocampal system?
3 neuronal layers? (ancient)
Involved in memory formation
Connects with various regions of the brain
Circuit of papez, long-term poentiation necessary for encoding, storage, and retrieval of memory.
What is the hypothalamus controlling?
In the forebrain. Size of an almond
regulates/controls basic behaviors, appetite, motivation, reproduction, sleep. In order to work appropriately it needs serotonin and noradernaline. Govern physiologic functions such as temperature regulation, thirst, hunger, sleep, mood, sex drive, and the release of other hormones within the body. Monitors water concentration, hormone concentrations and body temperature. It is associated with feelings of rage, aggression, hunger and thirst.
Thalamus
Olive shaped structure about one inch in length. It serves as a relay station for impulses traveling to and from the spinal cord, brain stem, cerebellum and cerebrum. It has an important function in directing sensory input to the appropriate place in the cerebral cortex. Sensory input from the body, the eyes, ears and other senses (except for smell) pass through the thalamus.
How does dysfunction of the serotonin and noradrenaline pathways affect mental health?
It is associated with depression.
What type of neurotransmitters are involved in metabortropic pathways?
Dopamine
Serotonin
noradrenaline
Acetylcholine
What are the critical functions of Acetylcholine?
- Regulate attention (prefrontal cortex); control the prefrontal cortex and help with attention
- memory (hippocampi; midbrain); help control the hippocampi and therein help with memory.
Describe acetylcholine pathways role in attention.
Attention: from the Nucleus Basilis of Maynert to the PFC, thalamus, amygdalae.
a. It binds to firing neurons in the prefrontal cortex and make them fire in synchrony. improves communication efficiency in the brain.
b. It connects with the thalamus and sensory input to the brain and stops some information getting to the prefrontal cortex.
c. It stops recurrent collaterals; stops cross-talk among neurons producing larger highways of communication.
d. synchronize mesocortical dopaminergic pathways, making them more efficient
Describe acetylcholine pathways role in momeory.
Memory: from the medial septal nucleus to the hippocampi.
a. ACh regulates hippocampal function by oscillating the hippocampi at 5-12Hz. • These vibrations appear crucial to memory formation, but it’s only partially understood.
Acetylcholine doesn’t make us learn, per se, but, it allows learning memories to do their job
Compare serotonin and noradrenaline pathways with dopamine pathways.
Dopamine pathways go to 4 different areas. Dysfunction affects reward/salience, cognition/motivation/social/expression, movement and hormonal.
Serotonin and noradrenaline are co-innervate; innervate similar regions. They also affect each other.
They project to the spinal cord, amygdala, hypothalamus, thalamus, PFC, basal forebrain & striatum. Dysfunction affects depression.
What symptoms occur when serotonin and noradrenaline sysfunction?
Depression. Serotonin and noradrenaline help innervate and regulate regions involved in processes that dysfunction in depression.
People may have difficulty with sleep, appetite, libido, making decisions, fear processing, and mood.
What are major pathways of acetylcholine?
- From the nucleus Basilis of Maynert to the PFC, thalamus and amygdalae.
- from the medial septal nucleus to the hippocampi.
What does acetylcholine regulates?
Attention: it reduces noise i.e., PFC signal-to -noise ration allowing for more focused attention.
Memory: enhances dopamine functioning. which in the mesocortical helps with cognition. Acetylcholine synchronizes the activity. + oscillate the hippocampi.
What anticholinergic means?
Some medication have anticholinergic effect; they inhibit acetylcholine from doing its function. Ex: antidepressants have therapeutic effects by enhancing serotonin and noradrenaline but the side effect are problems with memory, concentration, and attention.
