Question

The initial action by which cocaine increases heart rate is by a. blocking the degradation of norepinephrine b. increasing the release of norepinephrine c. stimulating autonomic ganglia d. stimulating \(\alpha_{1}\) adrenergic receptors e. preventing the reuptake of norepinephrine

Short answer

Answer: Cocaine initially increases heart rate by preventing the reuptake of norepinephrine.

Step-by-step solution

Analyze the options

To find the correct answer, let's briefly understand what each option states: a. blocking the degradation of norepinephrine: This option suggests that cocaine doesn't allow the breakdown of norepinephrine, implying its levels remain high. b. increasing the release of norepinephrine: This option implies that cocaine stimulates more norepinephrine to be released. c. stimulating autonomic ganglia: This option suggests that cocaine increases heart rate by affecting the autonomic ganglia, the cell bodies of neurons that control the autonomic nervous system. d. stimulating \(\alpha_{1}\) adrenergic receptors: This option proposes that cocaine directly interacts with the \(\alpha_{1}\) adrenergic receptors on the heart cells. e. preventing the reuptake of norepinephrine: This option indicates that cocaine stops the reabsorption of norepinephrine back into the neuron, implying that it remains in the synaptic cleft for an extended period.

Use knowledge of cocaine's physiological effects

Cocaine is known to block the reuptake of neurotransmitters such as dopamine, serotonin, and norepinephrine by binding to their transporters, thus leaving them in the synaptic cleft for a longer period, increasing their concentration and effect on their receptors. This action primarily leads to the increase in heart rate.

Select the correct answer

Based on our knowledge of cocaine's main physiological effects on neurotransmitters and its resulting impact on heart rate, the correct answer is: e. preventing the reuptake of norepinephrine

Key concepts

Neurotransmitter Mechanisms

Neurotransmitters are the chemical messengers of the brain, responsible for transmitting signals between neurons. A crucial aspect of their functionality is the process of reuptake, where neurotransmitters, after being released into the synaptic cleft and binding to their respective receptors, are reabsorbed by the neuron that released them. This reuptake mechanism is vital for signal termination and to maintain homeostasis in the nervous system.

Norepinephrine, a key neurotransmitter related to alertness and the 'fight or flight' response, has its own reuptake process which, when inhibited, leads to prolonged signaling effects. Cocaine, for instance, achieves its stimulatory effects primarily by hindering the reuptake of norepinephrine and other neurotransmitters such as dopamine and serotonin, which causes an increase in their concentrations outside of the neuron and therefore, sustained activation of their corresponding receptors.

Physiological Effects of Cocaine

Cocaine is a powerful stimulant drug that has significant effects on the human body. Upon ingestion, it immediately begins to alter neurotransmitter mechanisms as previously explained. The increased concentration of norepinephrine directly affects the sympathetic branch of the autonomic nervous system, which is responsible for the 'fight or flight' response.

As norepinephrine levels rise due to inhibited reuptake, this leads to heightened heart rate and blood pressure. This effect is beneficial in a naturally occurring 'fight or flight' scenario, as it prepares the body for rapid action. However, in the context of drug use, such as with cocaine, it can cause harmful cardiac effects. Furthermore, enhanced dopamine levels cause the euphoria commonly associated with cocaine usage, while increased serotonin levels affect mood, possibly causing agitation or anxiety.

Autonomic Nervous System

The autonomic nervous system (ANS) controls the body's involuntary functions, such as heart rate, digestion, and respiratory rate. It consists of two main branches: the sympathetic nervous system and the parasympathetic nervous system.

The sympathetic system activates the body's 'fight or flight' response, preparing for action by increasing heart rate, expanding air passages in the lungs, and redirecting blood flow towards essential organs. On the other hand, the parasympathetic system is often thought of as the 'rest and digest' system, slowing the heart rate and promoting digestion and nutrient absorption. Cocaine's stimulatory effects on the sympathetic nervous system can therefore disrupt the delicate balance maintained by the ANS, leading to potentially severe physical consequences.