In the example of childbirth the uterus contracts.  This pus…

In the example of childbirth the uterus contracts.  This pushes the baby’s head against the cervix.  Nerve endings in the cervix send a message to the brain that this is happening.  The brain secretes oxytocin.  Oxytocin stimulates the uterus to contract again and the baby’s head pushes even harder against the cervix.  Oxytocin is an example of:

Depolarization means that the inside of the membrane is beco…

Depolarization means that the inside of the membrane is becoming more [positive] compared to resting membrane potential. When the membrane is stimulated, Na+ channels [open] and Na+ rushes [into] the cell.  This causes [depolarization].  When the charge inside the cell reaches +30 mvs, the Na+ channels [close] and the K+ channels [open].  K+ rushes [out] the cell.  Finally the Na+/K+ pump uses [ATP] to move Na+ back [outof] the cell and K+ back [intoa] the cell.