Option D.5 – Stimulants
D.5.1 – List the physiological effects of stimulants
Stimulants reduce fatigue and make the user more alert by stimulating the central nervous system. They prevent drowsiness and can improve concentration.
- Increase heart rate, blood pressure and breathing rate
- Dilate pupils of eyes
- Arteries constrict
- May cause palpitations or tremors
- Sweating
- Reduced appetite
- In extreme cases, they cause restlessness, fits, delusions and hallucinations
D.5.2 – Compare amphetamines and epinephrine (adrenaline)
Adrenaline is a hormone that is secreted by the adrenal gland during times of stress to allow for a ‘fight or flight’ response. Amphetamines create a similar effect on the body byreleasing noradrenaline and are known as sympathomimetic drugs. They are structurally similar molecules, in that they are both derived from phenylethylamine. Amphetamines are used to treat conditions such as ADHD or narcolepsy.
D.5.3 – Discuss the short- and long-term effects of nicotine consumption.
Pure nicotine is as toxic as cyanide, having an LD50 of only 0.5-1.0 mg/kg for an adult. It is found in the tobacco plant, which is used to make cigarettes and cigars. Smoking is very harmful to the body and is a contributing factor to many deaths worldwide. It is lipid-soluble and can cross the blood-brain barrier.
The first contact with nicotine causes the person to feel nauseous and vomit, and sometimes leads to diarrhoea and glandular secretions. However, if smoked persistently, tolerance quickly develops. As a stimulant, nicotine causes an increased heart rate, blood pressure and is a vasoconstrictor (it causes the arteries to narrow), making it more difficult for the heart to pump blood.
Short-Term Effects
The use of nicotine increases alertness, concentration, heart rate and blood pressure. It also lessens anxiety, boredom and tension and reduces urine output. Nicotine can also relieve fatigue. The arteries constrict, which puts stress on the heart.
Long-Term Effects
If nicotine is used over extended periods of time, the risk of heart disease, coronary thrombosis, bronchitis, emphysema and peptic ulcers all increase. It also causes high blood pressure and increased levels of fatty acids in the blood, leading to stroke and atherosclerosis. Since it is an addictive substance, the user will become dependent, which is costly to the individual and places financial strain on their families. In fact, nicotine is more addictive than other common drugs such as alcohol and barbiturates. In the lungs, the smoke will condense to form tar, which is a carcinogenic substance. Also, cigarette smoke contains other toxic chemicals which have been linked with mouth, throat and lung cancer. Finally, the CO in the smoke inhibits the capacity of haemoglobin to carry O2.
D.5.4 – Describe the effects of caffeine and compare its structure with that of nicotine
Caffeine acts as a respiratory stimulant and is a weak diuretic, so it partially increases urine output and can lead to dehydration. Many caffeinated drinks are widely consumed, such as coffee and tea, as well as energy drinks. It is also helpful for the uptake of analgesics.
When consumed in low to moderate doses, caffeine stimulates the central nervous system to increase alertness, metabolic rate, energy, motivation and concentration. Many people will use caffeine to sustain intellectual effort during periods of tiredness. It constricts cerebral blood vessels, so quitting the daily habit of consuming caffeine can lead to headaches.
In large quantities, caffeine leads to anxiety, irritability and sleeplessness. It can also affect physical coordination.
Caffeine has not been found to be physically addictive, but many people still become psychologically addicted to it.
Both caffeine and nicotine contain a tertiary amine group and rings.