Primary FRCA Course Neurophysiology Exam Prep Questions Flashcards
The membrane potential of a nerve fibre:
Is directly proportional to the diameter of the fibre
False. It is conduction velocity that is directly proportional to the diameter of the fibre.
The membrane potential of a nerve fibre:
Is measured conventionally as negative on the inside
True.
The membrane potential of a nerve fibre:
Represents an imbalance of charge across the two sides of a semi-permeable membrane
True. In a nerve cell the concentration of potassium ions is much greater intracellularly than extracellularly (brought about by the sodium-potassium ATPase pump).
The membrane potential of a nerve fibre:
Reverses its polarity during an action potential
True.
The membrane potential of a nerve fibre:
Can be calculated from the Nernst equation
False. The Goldman constant-field equation is required to calculate the value of the overall membrane potential as it takes into account sodium, chloride and potassium. Nernst equation can be applied to calculate the membrane potential for this individual ion.
Compared with plasma, CSF contains:
Less sodium
True. Sodium concentrations are higher in the plasma.
Compared with plasma, CSF contains:
Lower osmolality
False. Both have an osmolality of around 290 mOsmol/l.
Compared with plasma, CSF contains:
More hydrogen ions
True. CSF has a pH of 7.32.
Compared with plasma, CSF contains:
A higher PCO2
True. 6.6kPa vs 5.3 kPa in plasma.
Compared with plasma, CSF contains:
More urea
False. Urea concentrations are higher in the plasma.
Concerning cerebral blood flow:
Blood flow in the grey matter may be twice that in the whites matter
True.
Concerning cerebral blood flow:
Is inversely proportional to PaCO2
False. It is directly proportional to PCO2 between the range of approx 2.5 and 10.5 kPa.
Concerning cerebral blood flow:
Is predominantly provided by the external carotid artery
False. The vast majority of cerebral blood flow is provided by the internal carotid arteries with a relatively small fraction being carried by the vertebral arteries.
Concerning cerebral blood flow:
Is reduced with acidosis
False. A reduced pH causes cerebral vasodilataion.
Concerning cerebral blood flow:
It is equal to 10% of cardiac output
False. Cerebral blood flow accounts for approximately 15-20% of cardiac output.
The knee jerk reflex:
Is due to stimulation of receptors in the patellar tendon
False. It is due to stretching of muscle spindles in the quadriceps muscle, caused by a tap on the patellar tendon.
The knee jerk reflex:
Has a reflex arc which involves a single interneurone
False. It has a single synapse.
The knee jerk reflex:
The afferent pathway is via A delta fibres
False. It is via A gamma fibres. The efferent pathway is the A delta motor neuron.
The knee jerk reflex:
Hypereflexia of the patellar is known as Westphal’s sign
False. Westphal’s sign is the absence or decrease of this reflex.
The knee jerk reflex:
Is abolished immediately after transection of the spinal cord at T6
True. Transection of the cord is followed by a variable degree of spinal shock where all reflexes are depressed or absent. Recovery of reflexes may take up to 6 weeks.
These modalities correspond to their correct pathways:
Temperature and pain via the ipsilateral spinothalamic tracts
False. Temperature and pain sensations travel in the contralateral spinothalamic tracts.
These modalities correspond to their correct pathways:
Fibres subserving fine touch form the gracile and cuneate nuclei
True. Fine touch is transmitted in the posterior white column in the medial and lateral fasiculi, which each connect to their respective cuneate and gracile nuclei.
These modalities correspond to their correct pathways:
Proprioception via the dorsal columns
True. The dorsal columns transmit fine touch and proprioception.
These modalities correspond to their correct pathways:
Spinocerebellar tracts relay information from muscles
True. Spinocerebellar tracts relay information from muscles and joints to the cerebellum.
When the nerve cell membrane is depolarised:
Sodium permeability falls slowly, producing an action potential.
False. There is a sudden, sharp rise in sodium conductance.
These modalities correspond to their correct pathways:
Pain and the spinotectal tract
True. The spinotectal tract transmits pain, temperature and touch sensation to the midbrain.
When the nerve cell membrane is depolarised:
Sodium permeability is raised until the resting membrane potential is restored.
False. The rise in sodium permeability is transient, with the resting membrane potential being restored by an increase in potassium conductance.
When the nerve cell membrane is depolarised:
Increased calcium permeability produces a plateau phase.
False. This is seen in cardiac muscle, not nerve cells.
When the nerve cell membrane is depolarised:
The change in sodium permeability is directly responsible for impulse transmission
True.
When the nerve cell membrane is depolarised:
Sodium efflux is self limiting
True. Three factors limit depolarisation speed, first the temporary opening of the sodium channels, secondly with increasing intracellular electropositivity the initial sodium gradient reduces, and finally there is an increase in potassium conductance.
The nerve action potential:
Transmission is “saltatory” between the nodes of Ranvier
True.
The nerve action potential:
Is conducted slower in myelinated fibres
False. Myelinated fibres transmit the action potential 50 times faster than unmyelinated fibres.
The nerve action potential:
Is propogated exponentially
False. The action potential is propagated in a linear fashion in unmyelinated fibres.
The nerve action potential:
Is approximately 35 mV above the resting potential
False. During the action potential the membrane potential changes from -70 to +35 mV, a 105 mV difference.
The nerve action potential:
Is initiated by sodium influx
True. It is initiated by sodium influx.
In complete cord transection:
Arterial blood pressure becomes labile
True. Due to autonomic hyperactivity.
In complete cord transection:
Autonomic hypereflexia occurs within the first few days
False. Elfh does not give an actual time frame, but some google sources suggested 1 month to 1 year, and wikipedia says normally within the first year.
In complete cord transection:
Tendon reflexes are the first to recover
False. The first reflexes to return are flexor reflexes to touch and anogenital reflexes.
In complete cord transection:
Recovery of reflexes occurs at around 6 months
False. Recovery of reflexes occurs at around 2 weeks, though can be delayed for up to 6 weeks.
In complete cord transection:
There is total loss in sensation from dermatomes below the level of injury
True.