MDS PREP
What type of receptors are found in the heart that are stimulated by the parasympathetic nervous system?
1) Adrenergic receptors
2) Muscarinic receptors
3) Nicotinic receptors
4) GABAergic receptors
The parasympathetic nervous system acts on muscarinic receptors (specifically M2 receptors) in the heart to decrease the heart rate and atrial contractility, thereby contributing to a resting state and energy conservation.
An unstable membrane potential that will spontaneously depolarize is a property of which type of muscle?
1. Cardiac only
2. Cardiac and smooth
3. Skeletal and smooth
4. Skeletal and cardiac
Physiology
Answer: 1
The type of muscle that exhibits an unstable membrane potential that will
spontaneously depolarize is cardiac muscle.
Cardiac muscle cells, which are responsible for the contraction of the heart,
have an intrinsic ability to contract rhythmically without the need for external
stimulation. This is due to their unique property of automaticity, which is
mediated by the presence of the sinoatrial (SA) node and the subsequent
propagation of electrical impulses throughout the heart via the conduction
system. The SA node, often referred to as the "natural pacemaker" of the heart,
generates action potentials spontaneously and sets the heart rate.
The cardiac action potential involves a series of ionic currents across the cell
membrane that result in the depolarization and repolarization of the membrane.
During the resting phase, the membrane potential is maintained at a negative
value (around -90 mV) primarily due to the efflux of potassium ions (K+). When
the SA node initiates an action potential, voltage-gated sodium (Na+) channels
open, allowing an influx of sodium ions that leads to depolarization. Following
this, calcium (Ca2+) and more sodium ions enter the cell through voltage-gated
calcium (CaV) and sodium (Nav) channels, while potassium ions efflux through
various types of potassium (K+) channels, contributing to the plateau phase and
repolarization of the membrane.
The spontaneous depolarization of cardiac muscle cells is essential for the
coordinated contraction of the heart, which is critical for maintaining blood
circulation in the body. This property is not typically found in skeletal
muscles, which require an external signal from motor neurons to contract, nor in
smooth muscles, which are controlled by the autonomic nervous system and
hormones.
What type of aphasia results from a lesion in Broca’s area?
1) Sensory aphasia
2) Motor aphasia
3) Global aphasia
4) Conduction aphasia
E. Wernicke’s aphasia
A lesion in Broca's area leads to motor aphasia, also known as Broca's aphasia or expressive aphasia. This type of aphasia is characterized by difficulty in producing speech, particularly with grammatical errors and reduced vocabulary. Understanding of language is usually preserved, but the ability to form coherent sentences is impaired.
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 contain various digestive enzymes and microvilli that increase the surface area for nutrient absorption. These cells are crucial for the final stages of digesting carbohydrates and proteins, as well as for the absorption of nutrients.
What is the effect of vitamin E deficiency on cell membranes?
1) Increased fluidity
2) Decreased fluidity
3) No change in fluidity
4) Unknown
Physiology
Answer: 2
Vitamin E is an important antioxidant that protects unsaturated fats in cell membranes from oxidation. Without vitamin E, these fats can become oxidized, leading to decreased fluidity and altered function of membranes.
What is the significance of the transport maximum for substances like glucose and phosphate?
1) It indicates the maximum amount that can be filtered by the glomerulus
2) It represents the maximum amount that can be actively reabsorbed by the tubules
3) It is the point at which the substance begins to be excreted in the urine
4) It is the point at which the substance becomes toxic to the body
The transport maximum for substances like glucose and phosphate represents the maximum amount that can be actively reabsorbed by the tubules before reaching saturation and being excreted in urine.
MCQ: The pancreas has which of the following cell types?
1) Alpha cells
2) Beta cells
3) Delta cells
4) All of the above
The pancreas has all of the following cell types: alpha cells (which produce glucagon), beta cells (which produce insulin), and delta cells (which produce somatostatin).
What is the primary function of bile acids in the intestine?
1) Emulsification of dietary fat
2) Neutralization of intestinal pH
3) Digestion of proteins
4) Absorption of water and electrolytes
Physiology
Answer: 1
Bile acids, through the formation of micelles, aid in the emulsification of fat, facilitating its digestion and absorption.