Case 7

Question 1

Outline the steps of the direct pathway

Answer 1

1) The stiratum is excited via D1 type receptors
2) The striatum usually sends inhibitory signals to GPi and SNpr, when stimulated it is more inhibitory
3) Usually the impulses from the GPi and SNpr are inhibitory, so when they are inhibited more their inhibitory signals to the thalamus stop.
3) The thalamus then increases its signals (which are excitatory) to the motor cortex, causeing an increased movement.

Question 2

Outline the steps in the indirect pathway

Answer 2

1) Striatum excited by D2 receptors, increases impulses to GPe (more inhibitory)
2) GPe usually inhibits subthalamic nucleus, but this inhibition is stopped by the striatums impulses.
3) Subthalamic nucleussends more (excitatory) impulses to the GPi
4) The GPi sends inhibitory signals to the thalamus, which prevents the excitatory signals from the thalamus exciting the motor cortex, so there is less movement.

Question 3

The spiny neurons of the corpus striatum project into the SNpc, which in turn sends widespread dopaminergic signals back to the spiny neurons. What does this cause?

Answer 3

Excitatory inputs mediated by D1 dopaminergic receptors and Inhibitory inputs mediated by type D2 dopaminergic receptors.

Question 4

Disorders in which circuit lead to Parkinsons diseas?

Answer 4

Nigrostriatal circuit

Question 5

What are the three functional subdivisions of the cerebellum?

Answer 5

Vestibulocerebellum, Spinocerebellum and cerebrocerebellum.

Question 6

What is the spinocerebellum primarily concerned with?

Answer 6

Lateral part movements of distal muscles, such as the relatively gross movements of the limbs in walking. The vermis, is concerned with proxial muscles and regulates eye moevements.

Question 7

What does the cerebrocerebellum control?

Answer 7

Motor skills associated with speech, hand-eye coordination, independent limb movements.

Question 8

Where does the vestibulocerebellum recieve inputs from and what does it control?

Answer 8

Inputs from the vestibulat nuclei in the brainstem, muscle spindles, joint afferents in neck. Maintains the stability of the head.

Question 9

What is a cerebellar peduncle?

Answer 9

A nerve tract that allows coommunication between the cerebellum and other parts of the CNS.

Question 10

What are the 4 deep cerebellar nuclei?

Answer 10

Fastigial nucleus, interposed nucleus, dentate nucleus and the vestibular nuclei.

Question 11

What toxins can cause Parkinsons?

Answer 11

Magnesium oxide, MPTP

Question 12

What do the motor symptoms of Parkinsons result from

Answer 12

Death of dopamine generating cells in the substania nigra.

Question 13

What other neurotransmitter is affected by the decrease in dopamine?

Answer 13

Acetylcholine

Question 14

What are lewy bodies?

Answer 14

Abnormal deposits of protein, they can accumulate in several regions of the brain (esp substania nigra pars compacta). Hallmark of parkinsons.

Question 15

What does PET stand for?

Answer 15

Positron emission tomography

Question 16

What is a PET scan?

Answer 16

Nuclear imaging technique producing a 3d image of the body.

Question 17

How does PET scans work?

Answer 17

A radiactive medicne is produced and tagged to a natural chemical (water, glucose), which becomes a radiotracer. This is inserted into a human and the energy emitted detected and a 3D image is produced.

Question 18

Give 2 examples of radiotracers

Answer 18

1) 18F-fluorodopa - radionuclide intorduced into dopamine

2) 18F-fluorodeoxyglucose - radionuclide introduced into glucose.

Question 19

What is a SPECT?

Answer 19

Single proton emission computed tomography. Uses a gama camra to acquire multiple 2d images from different angles which the computer then converts to 3d. You can then show thin slices along any chosen axis of the body.

Question 20

What are the pros and cons of SPECT ove PEt scans?

Answer 20

SPECT is cheaper, easier to perform, as radioisotope is more accessible and has a longer half-life. SPECT has lower resolution.