Neurochemical Explanation UD Flashcards
Neurochemical Bio Explanation UD
Some disruption of synaptic transmission is the cause of mental disorder.
Neurochemical - Monoamine depletion Hypothesis
Joseph Schildkraut (1965) argued that depression is caused by abnormally low levels of the monoamine neurotransmitters. These regulate limbic system, the brains emotional areas.
Neurochemical - Permissive Hypothesis
The balance of serotonin and noradrenaline that causes depression.
The level of serotonin normally controls the level of noradrenaline. But an abnormally low level of serotonin permits noradrenaline to decrease as well, causing depression.
Neurochemical - Monoamine Support
evidence that antidepressants increase the availability of serotonin and noradrenaline. This leads to fewer post-synaptic receptors being produced because of the greater stimulation happening, although this takes several weeks.
Neurochemical - Monoamine Competing
Reductionist.
Over time drugs were developed that had antidepressant properties but didn’t increase the availability of monoamine neurotransmitters, suggesting depression is bigger than just monoamine depletion.
It can’t explain the common experience of therapeutic delay. There is a delay of 4-6 weeks before they see improvement with the medication, this means it is hard to explain when levels of serotonin and noradrenaline increase immediately and are at normal levels after around a week.
Neurochemical - Receptor Sensitivity Hypothesis
depression is caused by changes in the sensitivity of postsynaptic receptors.
Neurons compensate for the reduction in neurotransmitter stimulation by increasing the sensitivity of receptors and producing more of them.
Depression causes serotonin and noradrenaline postsynaptic receptors to become more sensitive to reduced stimulation.
Receptor Sensivity Hypothesis Upregulation
Upregulation is the normal response of receptors to a depletion of neurotransmitters.
Neurochemical - RSH Weakness
the treatment is biological but the cause is psychological. It was noted that postsynaptic receptors were downregulated by antidepressants that increase serotonin, meaning depression could have a biochemical cause. Although an antidepressant drug could work by correcting a biological process disturbed by a psychological factor.
Neurochemical - BDNF Hypothesis
This is a chemical that feeds the neurons the nutrients they need to survive, grow and function.
Plays a role in neuronal plasticity (ability to form new synapses).
People that have depression have low levels of BDNF in hippocampus and prefrontal cortex.
The lower the BDNF levels, the more severe the symptoms.
BDNF and Stress
BDNF is used to link depression to stress, during stress BDNF in genes is off leaving neurons that need it vulnerable to atrophy or apoptosis.
Neurochemical - What did Sen et al 2008 find BDNF
a negative correlation between blood serum levels of BDNF and the severity of depressive symptoms, supporting this hypothesis.
