Quiz 3 28/11/18

Question 1

concerning the neuromuscular junction: The motor end-plate is the end of the motorneurone.

Answer 1

FALSE

-The motor end-plate is the specialised surface of the skeletal muscle cell onto which the motor neurone synapses.

Question 2

Concerning the neuromuscular junction: The endplate potential is generated by voltage-gated channels.

Answer 2

FALSE
-The end-plate potential (like all postsynaptic potentials) is generated by ligand-gated channels. Voltage-gated channels are only activated once the end-plate potential reaches threshold and evokes a new action potential in the muscle membrane.

Question 3

Concerning skeletal muscle: When an agonist muscle is active, its antagonist is reciprocally inhibited.

Answer 3

TRUE
-Many skeletal muscles work in pairs with opposing effects, eg flexors and extensors. Contracting both of these at the same time would not get you very far. Instead, when an agonist muscle is activated, the motor neurones supplying the antagonist muscle are usually inhibited.

Question 4

Concerning blood: The normal haematocrit range in a male is 37-47%.

Answer 4

FALSE

-This is the normal range for a female. The normal range in a male is 40-52%.

Question 5

The pyruvate dehydrogenase-catalysed reaction only occurs under anaerobic conditions.

Answer 5

FALSE
-The pyruvate dehydrogenase-catalysed reaction (in which pyruvate is converted into acetyl CoA) only occurs under aerobic conditions. If you answered the question wrongly, you may have been confusing the reaction with that catalysed by lactate dehydrogenase (in which lactate-pyruvate inter-conversion occurs): flow through that reaction, from pyruvate to lactate, only occurs under anaerobic conditions.

Question 6

Glycogen in a cell is osmotically inactive.

Answer 6

TRUE
-The osmotic inactivity of glycogen (which exists in a gel-like state in the cell, rather than being truly in solution) seems to be one of the reasons why glucose is stored in polymeric form. If the equivalent quantity of free glucose were stored, there would be a tendency for water to move into the cell by osmosis (and for glucose to move out).

Question 7

Ethanol consumption is unwise under conditions in which gluconeogenesis is important in the body, because its metabolism competes with gluconeogenesis for access to NADH.

Answer 7

FALSE
-Gluconeogenesis and ethanol consumption don’t mix, but this is because ethanol catabolism and gluconeogenesis both require NAD+, not NADH.

Question 8

Concerning safety in imaging: Power Doppler can lead to cavitation and destruction of tissues.

Answer 8

TRUE
-Ultrasound uses sound waves to image tissues. In normal circumstances the tissue is not adversely affected, however, when Doppler imaging is used and much more power is required and this can lead to microbubbles being created in the tissues (cavitation) which can destroy tissue.

Question 9

Concerning reflexes: Gamma motoneurones are an essential component of the stretch reflex.

Answer 9

FALSE
-Gamma motoneurones are not directly involved. Their control is via descending pathways from the brain and their function is to maintain spindle sensitivity during muscle contraction.