Question

Looking for a SHORT, CLEAR, AND SIMPLE answer:

1. Compare and contrast signaling by neurons, which secret neurotransmitters at synapses, with signaling carried out by endocrine cells, which secrete hormones into the blood.
   1. Discuss the relative advantages of the two mechanisms

Answer 1

Ans.

1).

• Neuronal and hormonal, both type of signaling are long ranging.
• Action potentials can be send to very long axons by neurons whereas blood transport the hormones throughout body.
• Because of the secretion of large amount of neurotransmitters from neurons at synapse, there concentrations are very high at recptors.
• This promotes binding of neurotransmitters to their receptors at low affinity for short period.
• However, because of their transportation in circulation, hormones get dilute and only a minute amount of hormones reach to their target cells.
• This promotes the binding of hormones with their receptors with high affinity for a longer period.
• Neuronal signaling is a conservative type of signaling whereas hormonal signaling is broad in nature.
• Examples of neurotransmitters are ACh and adrenaline.
• Examples of hormones include growth hormone, thyroid hormones and paratharmone.

2).

• Neuronal signaling is an example of electrical signaling whereas hormonal signaling examplifies chemical signaling.
• Neuronal signaling involves interaction of a neuron with some particular cells whereas hormones may interact with much more cells then the neurons depending upon presence of receptors.
• Although neuronal signaling is a fast response but it is short term in nature and is limited by the speed of action potential propagation.
• In contrast, rate limiting factor for hormonal signaling is blood flow and diffusion of hormones to their recptors.
• Hormonal signaling is a slower reponse but it's effects are longer lasting then neuronal signaling.