MDS PREP
What is the primary effect of acetylcholine on the cardiac muscles?
1) Decreased heart rate
2) Increased heart rate
3) No effect on heart rate
4) Increased force of contraction
Answer: 1) Decreased heart rateExplanation: In the heart, acetylcholine acts on muscarinic receptors, which are present on the sinoatrial (SA) and atrioventricular (AV) nodes. This leads to a decrease in heart rate by slowing the sinoatrial (SA) node's automaticity and increasing the time it takes for an electrical impulse to pass through the AV node.
Which of the following statements about the neuronal circuit of the cerebellum is true?
1) Climbing fibers originate from the cerebral cortex and terminate on purkinje cells.
2) Mossy fibers establish excitatory synapses with interneurons in the molecular layer.
3) Stellate and basket cells are stimulated by inhibitory inputs from purkinje cells.
4) Golgi cells are inhibited by mossy fiber inputs.
E. All of the above.
Mossy fibers originate from various sources in the brain and spinal cord and terminate on granule cells in the granular layer of the cerebellum. The axons of granule cells, called parallel fibers, stimulate the purkinje cells and also synapse with interneurons such as stellate and basket cells in the molecular layer and Golgi cells in the granular layer. Climbing fibers originate from the inferior olivary nuclei and synapse directly on purkinje cells. The statement that stellate and basket cells are stimulated by inhibitory inputs from purkinje cells is incorrect; they are stimulated by parallel fibers and inhibit purkinje cells. Golgi cells are also stimulated by mossy fibers and help in the regulation of the overall output of the cerebellum.
What is the primary role of sleep spindles during sleep?
1 ) To facilitate memory consolidation
2) To maintain muscle tone
3) To regulate body temperature
4) To initiate REM sleep
Sleep spindles are associated with the transition from stage 1 to stage 2 NREM sleep and are thought to play a role in memory consolidation and the integration of new information.
MCQ: The epithelial cells of the villi in the small intestine are responsible for:
1) Secreting gastric acid
2) Synthesizing bile
3) Final stage of digestion and nutrient absorption
4) All of the above
The epithelial cells of the villi in the small intestine are responsible for the final stage of digestion and nutrient absorption, playing a crucial role in the digestive process.
Which of the following is the correct statement regarding mammalian nerve fibers?
1) A-alpha fibers have the lowest conduction velocity and are responsible for pain and temperature sensation.
2) A-beta fibers have the highest conduction velocity and are responsible for motor supply to skeletal muscles.
3) A-gamma fibers are heavily myelinated and have the fastest conduction velocity.
4) C fibers have a large diameter and are responsible for fine motor control.
Answer: 2) A-beta fibers have the second highest conduction velocity after A-alpha fibers and are responsible for touch, kinesthetic sense, and pressure sensation, not motor supply to skeletal muscles. A-alpha fibers have the highest conduction velocity and are indeed responsible for motor supply to skeletal muscles.
What is the effect of stimulating the cholinergic system in the male reproductive system?
1) Decreased testosterone secretion
2) Decreased penile erection
3) Increased testosterone secretion
4) Increased penile erection
Stimulation of the cholinergic system can lead to increased penile erection due to the vasodilation of blood vessels in the penis, allowing for greater blood flow and engorgement of the corpora cavernosa.
Elevation of aldosterone, in blood results in
1 Low 'Na' and low 'K' in urine
2 High 'Na' and high 'K' in urine
3 High 'Na' and low 'K' in urine
4 Low 'Na' and high 'K' in urine
Physiology
Answer: 2
Elevation of aldosterone, in blood results in High 'Na' and high 'K' in urine resulting in acidic urine and body alkalosis
Which hormone is primarily responsible for increasing the force and frequency of uterine contractions during parturition?
1) Oxytocin
2) Estrogen
3) Progesterone
4) Prolactin
E. Cortisol
Oxytocin is synthesized in the paraventricular nucleus of the hypothalamus and acts on the uterus to increase the force and frequency of contractions during childbirth. It is released during labor and stimulated by the stretching of the cervix and vagina as the baby descends. Estrogens increase the sensitivity of the uterus to oxytocin, while progesterone decreases it. Prolactin is involved in milk production and let-down reflex. Cortisol is a stress hormone that prepares the body for parturition but does not directly increase uterine contractions.