Quiz 3 Flashcards
Concerning the autonomic nervous system: Activation of the adrenal medulla by the sympathetic nervous system is via nicotinic receptor stimulation.
TRUE
-The adrenal medulla can be thought of as a group of confused postganglionic sympathetic neurones that forgot to grow an axon. The synapse between the pre-ganglionic fibres and the cells of the adrenal medulla therefore fits the characteristic picture of all autonomic ganglionic transmission, ie acetylcholine acting via nicotinic receptors.
Concerning the neuromuscular junction: A single end-plate potential is unlikely to be large enough to reach threshold.
FALSE
-In a healthy neuromuscular junction the end-plate potential is always large enough to reach threshold and fire an action potential in the muscle. It is therefore said to have a high safety factor. This contrasts with most CNS synapses in which individual EPSPs are not big enough to reach threshold – this allows synaptic integration.
Concerning smooth muscle: Contractile filaments in smooth muscle are anchored by dense bodies in the cytoplasm.
TRUE
-You can think of these as being functionally similar to the Z-lines of skeletal muscle.
The citric acid cycle is sometimes called the ‘tricarboxylic acid cycle’ because some of the intermediates, including citrate, contain three carboxylate groups.
TRUE
-Notice that the ‘tricarboxylic acids’ of the cycle are ionised at the pH inside the cell, so one talks about citrate, isocitrate, etc rather than citric acid, isocitric acid and so on. Nevertheless, the cycle is not called the ‘tricarboxylate cycle’.
D-ribose and 2-deoxy D-ribose are 5-carbon sugars.
TRUE
-These pentoses are components of nucleic acids, and, in the case particularly of ribose, of many other molecules (like ATP, FAD and NAD).
Aldolase catalyses the reaction in which the 6-carbon molecule splits during glycolysis.
TRUE
-The hexose, at this stage of glycolysis is in the form of fructose 1, 6-bisphosphate, and it splits into glyceraldehyde 3-phosphate (3 carbons) and dihydroxyacetone phosphate (3 carbons).
Concerning imaging: X-rays travel in straight lines.
TRUE
- X-rays travel in straight lines and radiate outwards from a point source.
Concerning the autonomic nervous system: Parasympathetic preganglionic neurones are located in thoracic and lumbar segments of the spinal cord.
FALSE
- This is the location of sympathetic outflow. Parasympathetic outflow exits at cranial and sacral levels.
Concerning the neuromuscular junction: The duration of the depolarising phase of the action potential in skeletal muscle is approximately 250 msec.
FALSE
-The action potential in skeletal muscle is much shorter, lasting only 1-2 msec. The action potential in cardiac muscle may however last 250 msec, due to prolonged influx of calcium ions.
The articulating bones in fibrous joints are connected by fibrocartilage.
FALSE
-The articulating bones in fibrous joints are connected by dense connective tissue.
Macrophages are large leukocytes that form part of the innate immune system and: Undergo a maturation stage and develop into monocytes.
FALSE
-It is the other way around, monocytes are immature macrophages.
Liver, but not skeletal muscle contains glycogen phosphorylase.
FALSE
-Both liver and skeletal muscle necessarily contain glycogen phosphorylase, the main enzyme of glycogen catabolism. Liver, but not skeletal muscle, contains glucose 6-phosphatase, the enzyme that catalyses conversion of glucose 6-phosphate into free glucose.
The three kinase-catalysed reactions of glycolysis all generate ATP from ADP during glycolytic flow.
FALSE
-The first two, catalysed by hexokinase (or glucokinase in liver) and phosphofructokinase accomplish phosphorylation of glucose and fructose 6-phosphate respectively, and use ATP. They can be regarded as investing energy in the process of glycolysis, by preparing the sugar molecule for its later, ATP-providing splitting. The third kinase-catalysed reaction occurs at the end of the process. Here, pyruvate kinase catalyses the dephosphorylation of phosphoenolpyruvate (which essentially is just pyruvate phosphate) into pyruvate. This is one of the ATP-yielding steps of glycolysis. Notice that the enzyme is named for the reaction as it occurs in the opposite direction to that actually occurring during glycolysis. Kinases catalyse phosphorylation of something, with the phosphate coming from ATP. In theory, like all enzymes, pyruvate kinase can catalyse its reaction in either direction, but in actuality, in cells, net flow always occurs in the direction of phosphoenolpyruvate to pyruvate (and of ADP to ATP). Nevertheless, the enzyme is named as though it were catalysing the reaction in the opposite direction.
Concerning contrast media: Iodine-based contrast media are injected intra-venously and intra-arterially to outline vessels in vivo.
TRUE
- Iodinated contrast media is used for all intravenous and intra-arterial injections. Iodine has a high atomic number which absorbs the x-ray beam and therefore appears white similar to bones on radiographs.
Concerning the autonomic nervous system: Post ganglionic sympathetic nerves typically release acetylcholine.
FALSE
- Pre-ganglionic sympathetic nerves release acetylcholine, but most self-respecting post-ganglionic sympathetic nerves release norepinephrine. The ones supplying sweat glands stand out as being a very odd exception in that they do release acetylcholine. However, this really is the exception that proves the rule.
