Answer:
Testing positive for HIV means a high chance of death and a good chance of lower reproduction rates. But some people are immune to HIV, which makes them more evolutionarily fit, likely to live longer, likely to reproduce more, which would increase the frequency of the immune allele in the population. Over time, this increase in frequency of the gene that causes immunity could spread across the human race and cause it to evolve.
I don’t not understand this question
Answer:
First the proprioceptors found in the tissues will capture tissue damage and the presence of a continuity solution in the skin, then these receptors will activate the afferent pathway, which is the pathway of pain, which is sensory.
This stimulus that ascends to the central nervous system activates the "flight" mechanism in the face of pain (it is also known as the withdrawal mechanism).
It is in this way that a stimulation is sent to the alpha motor neuron in the form of an action potential as an efferent pathway to the skeletal muscles of the foot and the damaged leg, so that an automatic and involuntary muscle contraction is generated in a matter of millisemas of second after the damage, so the foot is removed from the damage area.
Explanation:
The withdrawal mechanism is a reflex that the human acquires before pain, that is why it is the muscular contraction is automatic and fast once the pain occurs.
So as a summary: 1 - the proprioceptors of the damaged tissue are activated 2- the signal of tissue damage rises as afferent to the CNS 3- the CNS responds by activating a signal that will be sent by interneuronal connections to the alpha motor neuron 4- the signal arrives as potential of action to the alpha motor neuron that innervates the muscles of the surrounding area to which it is damaged 5 - the muscles contract, generating the withdrawal of the limb.
