Stem cells<span> are a class of undifferentiated </span>cells<span> that are able to differentiate into specialized </span>cell<span> types. Commonly, </span>stem cells<span> come from two main sources: Embryos formed during the blastocyst phase of embryological development (embryonic </span>stem cells<span>) and. Adult tissue (adult </span>stem cells<span>).
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A. the two new cells created when cells divide
Answer:
The correct answer is B. Tapping the patellar tendon will usually result in a spinal reflex.
Explanation:
The patellar reflex is the involuntary contraction of the quadriceps femoris muscle by flexion of the patellar tendon. It is a reflex of spinal or stretching type. It was discovered, studied and first reported in 1875 by William Erb.
By striking the patellar tendon, the leg is extended as alpha motor neurons direct a nerve impulse to the quadriceps femoris muscle. The femoral nerve, responsible for such reflex, extends throughout the thigh and its synapses are found in the lumbar spinal nerve 2 to 4 of the spinal cord. Therefore, this movement is involuntary and responds to a need for automatic regulation of body muscles.
Answer:
Sensory Adaption
Explanation:
Stimuli, both external and internal, are sensed with the help of sensory receptors. These sensory receptors sense the change in internal or external conditions called stimuli and send the information to the central nervous system. The sensory information is processed and interpreted in the central nervous system which in turn makes a person aware of the sensed stimuli.
However, the constant presence of the same stimulus does not trigger the firing of the action potential as it occurred during the first few encounters. This is called sensory adaption. For example, chirping of birds is apparent when a person enters the countryside but becomes less apparent after a few days due to sensory adaption of ears.