Biological Explanation Of OCD

Question 1

What areas of the brain are believe to be involved in OCD?

Answer 1

• Orbitofrontal cortex (OFC) - involved in decision making and worrying about social and other behaviour.
• The thalamus - cleaning, checking and other safety behaviours

Question 2

Neural explanations include

Answer 2

Brain structure
Brain chemistry

Question 3

What parts of the brain are overactive in OCD?

Answer 3

The OFC and the thalamus are believe to be overactive.

Question 4

What would an overactive thalamus result in?

Answer 4

An overactive thalamus would result in an increased motivation to clean or check for safety. If the thalamus was overactive the OFC would also become overactive as a result.

Question 5

What would an overactive OFC result in?

Answer 5

Increased anxiety and increased planning to avoid anxiety.

Question 6

The worry circuit

Answer 6

The OFC and Thalamus’ overactive with each other becomes a worry circuit

Question 7

The worry circuit: abnormal

Answer 7

1.) Identifies worries (Orbitofrontal cortex)
2.) If damaged it fails to filter out minor worry signals (Caudate Nucleus)
3.) Transfers major and minor worry signals from CN to OFC, the circuit becomes overactive (Thalamus)
4.) Individual obsesses over minor worries and act in a way that is disproportionate to the worry - compulsions (Orbitofrontal cortex)

Question 8

What are neurotransmitters?

Answer 8

Brain chemicals that enable communication between different parts of the brain

Question 9

How are brain chemicals transited?

Answer 9

These are transmitted as electrical impulses using neurons, through a process called synaptic transmission.

Question 10

How does information get passed?

Answer 10

Information gets passed between neurons at the synapse.

Question 11

What is the synaptic cleft?

Answer 11

The gap between 2 neurons is called a synaptic cleft.

Question 12

What direction do neurotransmitters travel?

Answer 12

Axon-dendrite, you always send from the end of an axon and receive from a dendrimer as axons have vesicles and dendrites only have receptors.

Question 13

What neuron sends the neurotransmitter?

Answer 13

The pre-synaptic neuron which is before the synapse.

Question 14

What neuron received the neurotransmitter?

Answer 14

The post-synaptic neuron.

Question 15

Pre-synaptic neuron

Answer 15

Has vesicles in the axon terminal - ‘pockets’ which transport neurotransmitters

Question 16

Where do the neurotransmitters go to get transported and released in synaptic transmission?

Answer 16

These will go to the pre-synaptic membrane and release the neurotransmitter into the synaptic cleft.

Question 17

What will the neurotransmitter bind to?

Answer 17

The receptors which are on the post-synaptic membrane which causes a response

Question 18

Seratonin - effect

Answer 18

Inhibitory effect: they reduce the activity levels in the post-synaptic neuron

Question 19

Dopamine - effect

Answer 19

An excitatory effect: they increase the activity levels in the post-synaptic neuron

Question 20

Seratonin - mood neurotransmitter
Use

Answer 20

Contributes to well-being and happiness.
Helps sleep cycle and digestive system regulation
Affected by exercise and light exposure

Question 21

Dopamine - Pleasure neurotransmitter
Use

Answer 21

Feelings of pleasure, and also addiction, movement and motivation. People repeat behaviours that leas to dopamine release.

Question 22

What does too much dopamine lead to for those with OCD?

Answer 22

When too much dopamine is transmitted it leads to increased levels of activity and leads to compulsive behaviour.
Main transmitter in this part of the brain and it causes over activity in the affected brain structures.

Question 23

Seratonin - for those with OCD

Answer 23

Not enough serotonin is release in the same parts, therefore the dopamine excess is not controlled and anxiety is increased.
Thought that it affects the function of both the OFC and Caudate Nucleus.

Question 24

Genetic component to OCD

Answer 24

Proposed there is a genetic component to OCCD which predisposes some individuals to the illness

Question 25

Genetic explanations

Answer 25

It has been proposed that there is a genetic component to OCD which predisposes some to the illness.

Question 26

Why is OCD polygenic?

Answer 26

This is because more than 1 specific gene has been identified in the onset of OCD

Question 27

Taylor (2013)

Answer 27

Carried out a meta-analysis, finding as many as 230 different genes implicated in developing OCD called candidate genes

Question 28

How can we investigate genetic explanations?

Answer 28

Twin studies with monozygotic twins or dizygotic twins

Question 29

Nestadt (2010)

Answer 29

Reviewed previous twin studies:

MZ OCD concordance = 68%
DZ OCD concordance = 31%

Question 30

What is concordance rate?

Answer 30

The extent to which both twins share the same characteristic

Question 31

What is the COMT Gene?

Answer 31

• Helps to reduce the action of dopamine
• The variation in the COMT gene decreases the amount of COMT available
• Means dopamine is not controlled and there is too much dopamine which associates with OCD

Question 32

What is the SERT gene?

Answer 32

Affects the transport of serotonin
Creates lower levels of Seratonin therefore
Low levels of serotonin which have been implicated with OCD

Question 33

Diathesis-stress model

Answer 33

Suggests that people gain a vulnerability towards OCD through genes but also an environmental stressor is also required. This could be a stressful event, for example a bereavement.