Which of the following is not a component of the basal ganglia?
A. The term basal ganglia traditionally applied to fi ve large, subcortical nuclear masses on each side of the brain: the caudate nucleus, putamen, and globus pallidus, subthalamic nucleus, and substantia nigra. The globus pallidus is further divided into an external and an internal segment, and the substantia nigra is divided into a pars compacta and a pars reticulata. The caudate nucleus and the putamen are frequently called the striatum; the putamen and the globus pallidus are sometimes called the lenticular nucleus. The nucleus accumbens is the region where the putamen and the caudate merge anteriorly. What structures comprise the basal ganglia has been a debate over the years. More recently, an additional term, ‘ventral striatum’ has been introduced to describe those parts of the striatum (caudate and putamen) closest to limbic structures and that are involved in cognitive and behavioural functions. The ventral striatum includes the nucleus accumbens, which plays a major role in motivational and reward-related behaviour. Amygdala is closely related to the basal ganglia due to its functional and structural proximity. The amygdala complex develops from the same tissue mass as the caudate nucleus.
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Nystagmus is a recognized feature of all of the following except:
C. Horner’s syndrome is caused by sympathetic dysfunction at the craniocervical output. Clinical features include ipsilateral mild (usually <2 mm) ptosis, anisocoria (unequal pupils) due to ipsilateral miosis, enophthalmos, loss of ciliospinal refl ex, and ipsilateral facial anhidrosis (mnemonic ‘PAMELA’). Nystagmus is generally not seen. Nystagmus is a rhythmical oscillation of the eyes, occurring pathologically in a wide variety of diseases. Abnormalities of the eyes or optic nerves, especially when the onset is in childhood, may present with nystagmus (pendular or jerk nystagmus). Jerk nystagmus is characterized by a slow drift off the target, followed by a fast corrective saccade. Jerk nystagmus can be downbeat, upbeat, or horizontal (left or right) with the names being given according to the direction of the fast phase. Gaze-evoked nystagmus is the most common form of jerk nystagmus, where the subject is asked to look to the corner of the eye. Exaggerated gaze-evoked nystagmus can be seen in: drug intake/toxicity (sedatives, anticonvulsants, alcohol); muscle paresis; myasthenia gravis; demyelinating disease; and cerebellopontine angle, brainstem, and cerebellar lesions. Downbeat nystagmus usually occurs from lesions near the craniocervical junction, while upbeat nystagmus is associated with damage to the pontine tegmentum, from stroke, demyelination, or tumour. Vestibular system dysfunction also leads to nystagmus. This occurs in discrete attacks, usually associated with sudden movements of the head and is accompanied by symptoms of nausea, tinnitus, hearing loss, and vertigo.
Which of the following is a feature of normal aging?
A. Aging results in declines in a variety of cognitive domains, but some abilities appear to be relatively preserved. The relatively unaffected faculties include general intellectual knowledge, vocabulary and comprehension, attention processes, language abilities related to phonologic, lexical, and syntactic knowledge, motor skills that are learned early in life and repeatedly used, and immediate and implicit memory, including some aspects of short-term memory. Significant age-associated decline is seen in processing speed, ability to reason and solve problems, fluid intelligence, dividing attention between two tasks, executive function domains (mental flexibility, abstraction, and concept formation), visuospatial skills (drawing, construction, and maze learning), language skills involving semantic knowledge needed for naming and verbal fluency, motor skills that require speed, and ability to learn and retain new information for long-term access.
Which of the following lesions is commonly associated with gelastic (laughing) seizures?
A. Gelastic seizures are characterized by shallow laughter occurring in fits. The laughter usually lasts less than 1 minute and is then followed by signs of complex partial or focal seizures, such as eye and head movement, automatisms such as lip-smacking, and altered awareness. In many cases, these associated features may be absent, resulting in delayed diagnosis. The most common areas of the brain associated with gelastic seizures are the hypothalamus, the temporal lobes, and the frontal lobes. A combination of gelastic seizures and precocious puberty is often noted and can be attributed to hamartoma of the hypothalamus.
Which of the following is a ligand-gated ion channel?
C. The cholinergic nicotinic receptor forms the prototypical model for ionotropic receptors. It is a heteromeric pentameric protein, and each subunit is a transmembrane protein with four transmembrane domains (in total 20 transmembrane domains compared to seven in the case of metabotropic receptors). Binding of a neurotransmitter to the extracellular domain of the ionic receptor results in the brief opening of a transmembrane ionic pore. This leads to an influx of certain ions, which produces a brief modification of the resting membrane potential. This results in a postsynaptic action potential. Muscarinic acetyl choline receptors are not ionotropic; they are G-protein coupled and act via second messengers. GABAA not GABAB is an ion channel receptor. Norepinephrine receptors are largely G-protein coupled; they are not ion channels.
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