A working knowledge of the normal structure and function of the nervous system is key to understanding psychiatric disorders like Major Depressive Disorder (MDD). This slide deck includes the key components of neurosynaptic transmission, neurotransmitters and  hypotheses about the underlying causes of depression. A common genetic basis and environmental factors for MDD are briefly explored.

This slide deck has been developed in collaboration with the former Lundbeck International Neuroscience Foundation.

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Major Depressive Disorder - Neurobiology and Aetiology - slide 1
Neurobiology and Aetiology

To understand psychiatric disorders, it is important to have a working understanding of the normal structure and function of the nervous system.

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Introduction to neuroanatomy

Major Depressive Disorder - Neurobiology and Aetiology - slide 2
Introduction to neuroanatomy
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Major Depressive Disorder - Neurobiology and Aetiology - slide 3
Organisation of the nervous system
To understand psychiatric disorders, it is important to have a working understanding of the normal structure and function of the nervous system. The central nervous system (CNS; brain, spinal cord) and peripheral nervous system (PNS) are made up of neurones and glial cell…
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Major Depressive Disorder - Neurobiology and Aetiology - slide 4
Neurones
The neurone constitutes the functional unit of the nervous system; there are over 100 billion neurones in the brain.[Purves, Augustine, & Fitzpatrick et al., 2008; Martin 2003] Each neurone has the ability to interact with and influence many other cells, which creates a s…
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Major Depressive Disorder - Neurobiology and Aetiology - slide 5
Anatomical regions of the brain
The brain is divided into four anatomical regions: the diencephalon, brainstem, cerebrum, and cerebellum, as described on the slide.[Kandel, Schwartz & Jessell, 2000; Tortora & Derrickson, 2009] References: Kandel ER, Schwartz JH, Jessell TM (eds). Principles of Neural S…
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Major Depressive Disorder - Neurobiology and Aetiology - slide 6
Cerebrum
The cerebral cortex is the main functional unit of the cerebrum. The three main functional areas of the cerebral cortex are:[Tortora & Derrickson, 2009; Price & Wilson, 2003]
  • motor areas that control voluntary movement (primary, secondary, and association motor areas)
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Lobes of the brain
The brain can be thought of as comprising five ‘lobes’ – the four lobes of the cerebral cortex and a fifth lobe, the insula, deep within the brain, as shown on the slide.[Martin 2003; Tortora & Derrickson, 2009; Price & Wilson, 2003] The lobes of the cerebral cortex are n…
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Neurosynaptic transmission

Major Depressive Disorder - Neurobiology and Aetiology - slide 8
Neurosynaptic transmission
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Major Depressive Disorder - Neurobiology and Aetiology - slide 9
Neurotransmission
Information moves through the nervous system via two integrated forms of communication – electrical neurotransmission and chemical neurotransmission, as shown on the slide.[Kandel, Schwartz & Jessell, 2000] An action potential is generated at the origin of the axon follo…
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Major Depressive Disorder - Neurobiology and Aetiology - slide 10
The synapse
Neurones do not physically touch one another; two neurones are separated by a gap, known as a synaptic cleft.[Kandel, Schwartz & Jessell, 2000] Because neurones do not touch, and an action potential cannot ‘jump’ across a synaptic cleft, the signal must be converted to a …
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Major Depressive Disorder - Neurobiology and Aetiology - slide 11
Process of chemical neurotransmission
The idea that neurotransmission occurs at synapses and is mediated by chemicals was, at first, a contentious issue.[Purves, Augustine & Fitzpatrick et al., 2008] It was in the first half of the 1900s that experiments proved chemical neurotransmission occurred.[Purves, Aug…
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