After your wedding, you sit down to write out your thank you letters. As you pick up your pen, walk me through the events that must happen for the signal to reach the brain and a response to return to the hand to make it move and write out the letter.

Explanation:

In the given question, writing a letter is a voluntary approach and involves the muscles of the hands and fingers which are controlled by the somatosensory neuron pathway. The somatosensory pathway involves the sensory neurons (transmit the signal to the brain), the motor neurons (transmit signals to muscles) and the brain.

The writing begins with the neurons in the brain which can think like in the cerebrum.

1. Sending a signal to the hands via the motor neurons to pick a pen.

2. After touching the pen, the sensorimotor part of the brain gets activated which analyses the words.

3. The touch signals will be sent to the brain where the sensorimotor part integrates the signal, analyse it and then sends the signal via motor neurons to the effector's muscle.

4. The muscle of fingers moves and the person can write the letter.

5. As the person writes the letter, the sensorimotor part analyses the words through the eyes and proof read the information.

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.