Case 8

Question 1

What is Dopamine?

Answer 1

hormone and neurotranmistter involved in motivation, reward and reinforcment. It is formed by removing a carboxyl group from L-DOPA by DOPA decarboxylase.

Question 2

How is Dopamine action terminated?

Answer 2

In the synaptic cleft by reuptake of dopamine into nerve terminales and surrounding glial cells by sodium ion-dependent dopamine transporter.

Question 3

What receptor type does dopamine work on?

Answer 3

G-protein coupled receptor

Question 4

What are the two groups of dopamine receptors?

Answer 4

D1-type (D1 and D5 receptors) D2-type receptors (D2-D4).

Question 5

How do D1 receptors function?

Answer 5

Receptors are coupled to the G protein GSalpha, this activates adenylyl cyclase, increasing extracellular cAMP.

Question 6

How do D2 receptors function?

Answer 6

Coupled with the G protien GI alpha, which inhibits cAMP formation by inhibiting adenyly cyclase.

Question 7

Where does the nigrostriatal pathway go from and to?

Answer 7

From the substantia nigra pars compacta (SNc) to the striatum.

Question 8

What is the function of the striatum?

Answer 8

Dorsal striatum is involved in involuntary motor control and associative striatum is involved in learning, habituation, memory, attention, motivation, emotion and volition.

Question 9

What is the order of the nigrostriatal pathway?

Answer 9

Medium spiny neurons of the corpus stiatum project into the SNc, which sends dopaminergic signals back to the spiny neurones. These pass through the direct or indirect pathway and have an antagonistic effect on the basal ganglia. This decreases the inhibitory outflow causing an increase in the excitability of upper motor neurones.

Question 10

What is the direct pathway of the nigrostriatal pathway?

Answer 10

Excitory inputs from D1 type dopaminergic receptors on spiny cells that project into the internal globus pallidus.

Question 11

What is the indirect pathway of the nigrostriatal pathway?

Answer 11

Inhibitory inputs mediated by D2 type dopaminergic receptors on the spiny cells that project into the external globus pallidus.

Question 12

What is the mesolimbic pathway?

Answer 12

Goes from ventral tegmental area to limbic regions (including the nucleus accumbens in the ventral striatum, amygdala, hippocampus and the medial prefrontal cortex). These regions are associated with reward, motivation affect and memory and so play a major role in addiction.

Question 13

What is the mesocortical pathway?

Answer 13

Goes from the Ventral Tegemental Area to the frontal cortex, this pathway is involved in cognative function, motivation and emotional response.

Question 14

What is the tuberoinfundibular pathway?

Answer 14

Goes from the tuberal region to median eminence, dopamine acts to inhibit prolactin release from pituitary.

Question 15

What are the three funtional pathways of the stiatum?

Answer 15

Sensorimotor - dopamine input from SNc, conatins D1 and D2 receptors. Associative - strong input from dorsolateral prefrontal cortex (DLPFC) and dopamine input from SNc, D1, D2 and D3 receptors. Limbic - Reward, dopamine input from VTA Contains D1, D2 and D3 receptors.

Question 16

What is the prevalence of schizophrenia?

Answer 16

1% worldwide.

Question 17

What is the epidemiology

Answer 17

slightly more common in women, more common in lower socioeconomic classes, Africa-Caribbean.

Question 18

What are some alterations in brain structure thought to be implicit in schizophrenia?

Answer 18

enlarged cerebral ventricles, thinning of the cortex, decreased size of anterior hippocampus.

Question 19

What factors can play a role in the development of schizophrenia?

Answer 19

Genetic, Environmental (stress or being born in winter months), Neurodevelpmental vulnerability, substance abuse (heavy cannabis use double risk, frquent use during teens can increase risk by 6 times).

Question 20

What are the three catagories for symptoms of schizophrenia?

Answer 20

Positive, negative and cognative

Question 21

What are positive symptoms?

Answer 21

Delusions, hallucinations and thought disorders.

Question 22

What are negative symptoms?

Answer 22

Flat or blunter affect and emotion, alogia, inability to experience pleasure, lack of desire to form relationships, lack of motivation.

Question 23

What are cognitive impairments?

Answer 23

Reduced attemtion, processing speed, working memory, abstract thinking, problem solving

Question 24

What is the course of schizophrenia?

Answer 24

Wide variation. Usually follows a relapsing and remitting course. Patients may suffer one episode and return to normal or several episodes during which the illness never fully abates.

Question 25

What is the dopamine hypothesis?

Answer 25

Psychotic episodes are triggered by activation of dopamine receptors. Increased activity in the mesolimbic pathway may cause positive symptoms, decrease of activity in the mesocortical pathway can cause negative symptoms.

Question 26

What two observation support the dopamine hypothesis?

Answer 26

Effect of amphetamines in healthy people and neuroleptic drugs are potent blockers of D2 receptors.

Question 27

What is the revised version of the dopamine hypothesis?

Answer 27

Not due to the mesolimbic pathway but due to increased dopamine presynaptic function in the nigrostriatal pathway. There is a small elevation of D2/D3 receptors.

Question 28

What are the ionotropic glutamate receptors?

Answer 28

Ligand - gated ion channels divided into 3 main types NMDA, AMPA and the kainate type.

Question 29

What ions is the AMPA receptor mainly associated with?

Answer 29

Na+ and K+

Question 30

Describe the NMDA receptor in more detail?

Answer 30

Significantly associated with Ca2+ as well as Na and K ions. Under resting membrane potential conditions these receptors are blocked by Mg+ so it is only after the neural membrane depolarises and glutamate binds that the ion channels open. Glycine is also required as a co-agonist.

Question 31

What is the glutamate hypothesis?

Answer 31

Diminished activation of NMDA receptors in the brain.

Question 32

What are the 5 classifications of schizophrenia?

Answer 32

Paranoid, disorganized, catatonic, undifferentiated and residual.

Question 33

How is schizophrenia diagnosed?

Answer 33

Assesment of history, symptoms and signs and information gained from collateral sources.

Question 34

What is the treatment for schizophrenia?

Answer 34

Antipsychotics, rehabilitation, psychotherapy, family therapy, CBT.

Question 35

What are the two classes of antipsychotics?

Answer 35

Conventional and 2nd generation

Question 36

What is a common problem in schizophrenia?

Answer 36

Patients only partially complying

Question 37

What is the mental health act of 1983?

Answer 37

An act covering the reception, care and treatment of mentally disordered patients, the managment of their property and other related matters. In particular it allows people to be detained in hospital or police custody against their wishes.

Question 38

What is section 2 of the mental health act?

Answer 38

A patient can be detained for 28 days if: 1) they are suffering from mental disorder which warrants detention for assessment 2) They ought to be detained in the intrests of thier own or other peoples safety. It requiresthe written recommendations of two registered medical practitioners.

Question 39

What is section 3 of the mental health act?

Answer 39

An application for treatment if: 1)they are suffering a mental illness to the degree it makes it appropriate they recieve treatment 2) It is necessary for the health and safety of the patient or others that they receive treatment that cannot be given unless they are detained under section. 3)The appropriate medical treatment is available. it requires two medical practitioners to give recommendation and can last up to 6 months.