Psychopathology2 Flashcards
The role of the peripheral nervous system
Sends information to the CNS from the outside world, and transmits messages to and from the CNS to muscles and glands in the body.
E.g. Hear something and deciding to run. PNS is hearing the noise.
The role of the somatic nervous system
Transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act.
E.g. Picking up the spoon.
The role of the autonomic nervous system
Transmits information to and from the internal bodily organs. It is ‘automatic’ as the system operates involuntarily. It has two main divisions: the sympathetic and the parasympathetic nervous systems.
E.g. Giant spoon chasing you, preparing to run away.
Role of Central nervous system
Consists of the brain and spinal chord and is the origin of all complex commands and decisions.
E.g. Decision to pick up a spoon.
The biological explanations of OCD
- (Neural) Abnormalities in the structure/functions of the brain.
- Maybe partly caused by genes
- OCD is assumed to be an illness that can be treated using medical methods.
NAGI
Key symptoms of OCD
Obsessions: persistent, intrusive thoughts that the person fins v unpleasant. Thoughts about things person finds revolting.
Compulsions: the repetitive, irresistible urge to perform a behaviour, the experience of loss of voluntary control over this intense urge and the tendency to perform repetitive acts in a habitual or stereotyped manner.
Neural abnormalities in the brain
OCD associated with abnormalities in brain circuits that are involved in detecting snd responding to potential danger. Circuits probably evolved to protect us from threats. But in OCD abnormal activity in these circuits may cause trigger obsessions.
Affected areas: Basal ganglia, orbito-frontal cortex
Basal ganglia
Group of brain structures at the base of the brain important in emotion and habit type behaviours.
Orbitofrontal cortex
Area is in the frontal lobes and it processes sensory information - sights and sounds - to identify threats.
The basal ganglia and orbitofrontal cortex loop
BG connects with OC in a loop.
There is over activity of a direct pathway that triggers concerns about danger, harm and hygiene and under activity of an indirect pathway which inhibits compulsive behaviours in response to such concerns.
Therefore, compulsive behaviours become repetitive.
Evidence for abnormalities in activity in the basal ganglia
Have been found in brain scanning studies - using MRI machines - of people with OCD.
However, not all people with OCD show these abnormalities.
Study for neural abnormalities causing OCD
POLAK ET AL 2012:
65 year old man had a heart attack at 42 and his brain was deprived of oxygen resulting in damage to his basal ganglia. He then suffered from compulsive whistling for 16 years. 5-8 hours a day and was worse when he was tired.
Behaviour reduced with a drug that increased levels of serotonin.
Deep brain stimulation
Reduces OCD symptoms by altering circuit between BG and OC through surgery.
Psychiatrist Damian Denys treated 50 patients with 60% improved OCD symptoms.
Evaluation of brain abnormalities as an explanation for OCD
+ Results of surgeries improving symptoms gives stronger evidence for this explanation.
- Cannot be certain of cause and effect from brain scanning studies. Could be abnormalities are a result of OCD and the didn’t cause it.
- Not everyone with OCD show abnormalities so another explanation needed.
Neurotransmitters
Neurotransmitters are chemicals in the brain that allow messages to be sent between brain cells across the synapses.
SEROTONIN
Evidence of abnormalities in neurotransmitters in the brain causing OCD
+ Mutations in a gene that is linked to serotonin activity have been found in sone gene mapping studies comparing patients with and without OCD.
+ Medications that increase serotonin levels are effective in reducing OCD symptoms in some patients. Considerable evidence for this too.
Evaluation of abnormalities in neurotransmitters in the brain causing OCD
- Unwise to just focus on role of serotonin in OCD. Brain uses a range of complex neurotransmitters which interact with eachother.
- May reduce symptoms but doesn’t mean OCD was caused by a lack of serotonin (headache treated with panadol, doesn’t mean it was caused by a lack of panadol).
- Baxter et al looked at patients treated with SSRI’s and behaviour therapy, both showed improvements. So as psychological treatment caused changes in brain activity - suggests brain abnormality may be a consequence mot cause of OCD.
Genes in OCD
OCD likely to be polygenic - up to 230 genes could be involved in OCD.
Genes interact with each other and environment so hard to know for sure whether or not certain genes will go on to develop OCD.
Evidence from twin studies for role of genes
NESTADT 2010:
Concordance rate in identical twins (MZ) 68% but in DZ only 31%.
MZ higher because they are more genetically similar so OCD must have a genetic explanation.
Evidence for gene mapping for OCD
Technology advanced so that we can now analyse genetic material itself. Scientists can look for specific areas of genetic code with consistently differ between people with and without OCD.
Evaluation from gene mapping
- No twin study got 100% for MZ twins so environment must play part in OCD.
- MZ and DZ in similar conditions but MZ perhaps more similar that DZ because same gender and look same so they have a more similar environment.
- Currently mechanisms that genes make someone more vulnerable to OCD not fully understood. So further research is needed.
- So complex unlikely to be able to find a treatment for it.
SSRI
Specific serotonin reuptake inhibitors
Examples of SSRI’s
Prozac
Specific serotonin reuptake inhibitors
Typical dose: 20 mg a day
3-4 months
GP or psychiatrist prescribes
Side effects: irritability, headaches, sleep disturbances
SOOMRO ET AL 2008
17 studies
3000 patients, comparing SSRI’s to placebo
Conclusion: SSRI’s better than placebo, moderately effective in reducing OCD symptoms - 70%.
KORAN ET AL 2000
Aim: asses whether adding olanzapine to prozac would be more effective.
Method: 10 patients who didnt respond to prozac. OCD symptoms assessed by Yale-Briwn Obsessive Compulsive Scale. Mean score 29/40
Patients continue to take prozac but have olanzapine too - dose increasing to 10mg.
Results: one patient dropped out, mean score dropped to 24, reduction in symptoms varied one 68% over 6 months, but others less.
Conclusions: some benefits, but some put on weight.
V small sample study, did not have placebo control.
Appropriateness of SSRIs as a treatment for OCD
- Reduction in OCD symptoms, allows person to return to school/work. So good for economy as no longer have to pay sick leave and company more efficient.
- Cost effective, tablets taken easily. Not taking time off for sessions, and cheaper than therapist.
- Side effects, people don’t want, reduce effectiveness as can’t rely on drugs alone.
- Relapses more likely.
- Prozac not suitable for children as can trigger self harm/suicidal thoughts.
Nervous Systems
Central (brain and spinal chord) - Peripheral - Somatic (messages from senses) and Autonomic (Sympathetic - speeds up/ready for action- and Parasympathetic -slows down).
Excitatory potentials
Make more likely for neuron to fire.
E.g. Adrenaline
Inhibitory potentials
Make less likely for a neuron to fire.
E.g. Serotonin
Node of ranvier
Boost electrical impulse.
Axon
Long thread part of nerve cell that send electrical imoulses to other cells.
Dendrites
Short branch of nerve cell along which impulses received from other cells at synapses are transmitted to cell body.
Neurotransmitter
Chemical messengers in nerve cells.
Receptors
Areas on pre-synaptic membrane that neurotransmitters connect to.
Sensory neurons carry information…
To the brain.
Outline process of synaptic transmission
1: electrical impulse sent
2: neurotransmitters released
3: axon terminal
4: converts to chemical to go across the synapse
5: synapse
6: receptor detects impulse
Fight or flight bodily changes
Mouth dry - reduced digestion which happens in mouth with enzymes
Fast breathing - to get oxygen to muscles to prepare for run.
Neurons
Sensory (pns) to relay (cns) to motor (pns)
Sensory neuron
Tell rest of brain about external and internal environment by processing information taken from one of the five senses.
Relay neuron
Carry messages from one part of the cns to another.
Connect motor and sensory neurons.
Motor neurons
Carry signals from cns which helps both organs, including glands and muscle function.
Pituitary gland
Some hormones released are key for regulating endocrine system.
Master gland.
Oxytocin
Adrenal gland
Key for fight or flight response as releases adrenaline.
Testes gland
Release testosterone
Ovaries gland
Facilitate release of oestrogen and progesterone.
Fight or flight
Generated from autonomic nervous system (sympathetic). Reflex - helps individual manage physically under threat. Helps react quicker than normal.
Fight or flight process
Hypothalamus recognises threat. Message to adrenal gland. Triggers release of adrenaline to the endocrine system and noradrenaline in the brain. Prompts physical changes: inc HR, faster breathing, inc muscle tension, pupil dilation, sweat, dec functioning of digestive system and immune system.
Glands
PATTO Pituitary Adrenal Thyroid - thyroxine Testes Ovaries
Deep brain stimulation
The system involves surgically implanting tiny electrodes into the brain which are then connected via a subcutaneous wire to a neurostimulator implanted under the skin near the clavicle.
Neurostimulator: pace-maker like device with a battery and circuitry to generate electrical signals that are delivered by the DBS leads to the targeted structures deep in the brain.
DBS lead: thin, insulated, coiled wire ending with an electrode.
The settings of the neurostimulator can be changed via a hand held device.
There is also an extension put in the brain that is an insulated wire that connects the lead to the neurostimulator.
Role of endocrine system
To secrete hormones which are required to regulate main bodily functions.
To provide a chemical system of communication via the blood stream.
