W9L2 - Noradrenaline Flashcards
Noradrenaline Synthesis
Tyrosine > Dopa > Dopamine > Noradrenaline (Same as Dopamine)
What does Tyrosine Hydroxylase do
Synthesize tyrosine into DOPA
What does Amino Acid decarboxylase do
Synthesize DOPA into Dopamine
What does Dopamine β-hydroxylase do
Synthesize and break down Dopamine enzyme
Noradrenaline Breakdown
1 additional synthesis:
- Noradrenaline > Adrenaline
- Noradrenaline > Inactive metabolite
- Monoamine oxidase (MAO)
Noradrenaline > Inactive metabolite
Monoamine oxidase (MAO)
What does the norepinephrine do
- Sympathetic nervous system (flight/fight)
- Arousal/vigilance
- Exploitation vs Exploraton
- Reward/Addiction (as in dopamine)
- Memory
- Anxiety
What is the part of releasing norepinephrine
Locus Coeruleucs (LC)
Properties of Lcous Coeruleus (LC)
Very small area of brain with very few neurons (about 30,00)
One thing noradrenalien is MOST known for
Arousal. More NA = more arousal
During REM sleep, is NA released?
Silent = Little NA
Following a noxious/super positive event, is NA released?
Highest rates rapidly follow a transient noxious or extremely positive stimulus/event (lots of NA released)
4Fs in NA
Fight, Flight, Freeze or Fornicate
What is state of hyperarousal of NA adapted for:
Evolutionary aspect is NA important for individual or sexual fitness
What can high level of LC/NA lead to
- Stress
- Sustained LC/NA due to environmental factor
- Anxiety
- Uncontrollable irrational worry for 6 months
- Panic Attacks
- Brief intense episodes reflecting LC/NA Spikes triggered by
- Apparently random thoughts
- Internal thoughts
- Learned Associations (PTSD)
- Brief intense episodes reflecting LC/NA Spikes triggered by
What is the shape of stress. Explain
Inverted U shape. Optimal performance requires a balance.
At moderate levels of LC/NA activity, what does NA do
Consolidate decisions
- Tradeoff between
- exploiting known sources of reward
- exploring the environment for alternative sources of reward (food, water, sex etc).
What is exploitation vs exploration. What kind of behaviour is best?
Can do one thing at once
- Indecision(Exploring): Constantly changing decisions
- Inflexible (Exploiting): Repetitive behaviour
- is bad because we need balance
How does brain decide 2 behaviour
- Burst of NA release “tips the balance” in favor of winner
- increases strength of activating signal
- inhibition of other signals
When do LC neurons fire. What happens after?
- When behavioural response selected & exectued (burst)
- Neurons are inhibit after to allow selected behaviour to be ‘exploited’
What affects the strength of burst of LC neurons
More Importance, Salience, or Arousing alternatives the bigger the LC burst and NA released
LC Neurons during high arousal
- Larger neuronal response
- More NA + Longer inhibition
- In high arousal, chosen focus of attention dominates longer
LC Neurons during low arousal
- Smaller neuronal response
- Less NA + Shorter inhibition. Neurons start firing more to add variability to decision
- In low arousal, increased NA promotes a switch to a new decision, promoting “exploration” of alternative behaviors
How does LC release affect performance. What is the optimal performance. Compare low and high
- Low LC activity and NA release
- Tired, poor performance
- Inattentive non-alert
- Tired, poor performance
- High LC activity and NA release
- Restless, stressed, poor performance
- Distractible
- Restless, stressed, poor performance
- Optimal performance requires moderate activity with large intermittent bursts.
