The external ear structure is called the Pinna.
The Pinna helps to channel sound waves into the ear.
Many animals have the ability to move their pinna towards the direction of sound.
I have attached an image of a dog's ear to show you the external structure called the Pinna.
I hope this helps! I'm happy to answer any other questions you might have :)
[Image sourced from: https://www.msdvetmanual.com/dog-owners/ear-disorders-of-dogs/ear-structure-and-function-in-dogs]
Answer:
4 reasons here:
Explanation:
1) Adventure; boredom causes them to look for excitement, even if it's detrimental to their health.
2) Peer pressure;research shows that risk-taking among teens doubles when peers are around.
3) media;easy to guess, shows a lot of risky behaviour in glamorous or admirable ways.
4) Poor self-esteem; bullying can lead to poor self-esteem and higher chance of the victim becoming depressed and taking substance to cope with the depression, also leads to err, self-death
Answer: ionotropic; metabotropic
Explanation:
A receptor can directly open the channel and exerts an ionotropic effect. The ionotropic effect takes place by the help of ionotropic receptors. These receptors are membrane bound receptor proteins which responds by the bonding of the ligand.
Due to ligand binding the channel opens and allows the movement of ions into the cells which helps in either increasing or decreasing the action potential.
The receptors can also bind to the ligand and produce metabotropic effect which means by the second messenger.