Tissue damage activates nociceptors or pain receptors in the skin. A signal is sent to the peripheral nerve to the spinal cord where neurotransmitters or chemical messengers are released. It activates other nerves to pass signal to the brain. The signals are relayed to the somatosensory cortex for sensation, frontal cortex for thinking and limbic system for emotional response.
Cell maintain homeostasis through diffusion in isotonic solution. Isotonic means that the concentrations are the same on either side of the membrane, maintaining homeostasis.
Nicotine on direct application in humans causes irritation and burning sensation in the mouth and throat, increased salivation, nausea, abdominal pain, vomiting and diarrhea. Predominant immediate effects consist of increase in pulse rate and blood pressure. Nicotine also causes an increase in plasma free fatty acids, hyperglycemia, and an increase in the level of catecholamines in the blood. There is reduced coronary blood flow but an increased skeletal muscle blood flow. The increased rate of respiration causes hypothermia, a hypercoagulable state, decreases skin temperature, and increases the blood viscosity.
For amphetamine the immediate effects are quicker reaction times, feelings of energy/wakefulness, excitement, increased attentiveness and concentration, feelings of euphoria. Side effects of amphetamines can include heart palpitations, dry mouth, headache, hostility, nausea, cognitive impairment, severe anxiety, lack of appetite, teeth grinding, dizziness, increased heart rate, heart palpitations, rapid breathing rate, hypertension (high blood pressure), increased body temperature, erectile dysfunction, irregular heartbeat.
Cocaine causes a short-lived, intense high that is immediately followed by the opposite intense depression, edginess and a craving for more of the drug the side effects are Loss of appetite increased heart rate, blood pressure, body temperature, contracted blood vessels increased rate of breathing, dilated pupils, disturbed sleep patterns, nausea, hyperstimulation, bizarre, erratic, sometimes violent behavior hallucinations, hyperexcitability, irritability, tactile hallucination that creates the illusion of bugs burrowing under the skin, intense euphoria, anxiety and paranoia, depression, intense drug craving, panic and psychosis, convulsions, seizures and sudden death from high doses (even one time)
