The question is incomplete. The complete question is as follows;
Examine and characterize the two motor pathways in the stretch patellar reflex.
A) Alpha motor neurons send efferent messages to the quadriceps, while parallel efferent messages to the hamstrings are reduced.
B) Alpha motor neurons send efferent messages to excite the quadriceps and the hamstrings are reduced.
C) Alpha motor neurons activate the quadriceps. Once the quadriceps have contracted, alpha motor neurons inhibit the hamstrings.
D) Interneurons excite alpha motor neurons, which in turn excite the muscle.
Answer:
Alpha motor neurons send efferent messages to the quadriceps, while parallel efferent messages to the hamstrings are reduced.
Explanation:
Neuron is the structural and functional unit of the nervous system. The neurons can be classified as sensory neuron, motor neuron and interneuron based on their function.
The knee reflex is known as patellar reflex that involves in the movement of knees and stretching of patellar tendon. The efferent message is send by alpha motor neuron that are located in the anterior horn of the spinal cord. This send to quadriceps that results in the muscle contraction. In this process, the hamstrings messages are reduced that plays an important role in patellar reflex.
Thus, the correct answer is option (A).
Answer;
-Genetic heterogeneity and epistasis.
Explanation;
-Marfan syndrome is a genetic disorder that affects the body's connective tissue that holds all the body's cells, organs and tissue together.
-Genetic heterogeneity is defined as mutations at two or more genetic loci that produce the same or similar phenotypes. Genetic heterogeneity may be either; allelic heterogeneity, which occurs when a similar phenotype is produced by different alleles within the same gene; or locus heterogeneity, which occurs when a similar phenotype is produced by mutations at different loci.
-A gene is said to be epistatic when its presence suppresses the effect of a gene at another locus. Epistatic genes are sometimes called inhibiting genes because of their effect on other genes which are described as hypostatic.
-From these descriptions the marfan syndrome demonstrates both genetic heterogeneity and epistasis.
That would be D.
The highest temperatures are near the equator and the lowest ones at the poles. So the lower the degree of latitude the higher the temperature.
Speciation is the process by which new species form. It occurs when groups in a species become reproductively isolated and diverge. In allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation.