What is the difference between the function of autonomic transmitters and receptors? In what way or how do they regulate effector cells that are dually innervated?

Thanks!

Autonomic transmitters and receptors play crucial roles in regulating the activity of effector cells in the autonomic nervous system. To understand their difference and how they regulate dually innervated effector cells, let's break it down:

1. Autonomic Transmitters:
Autonomic transmitters, also known as neurotransmitters, are chemical substances that transmit signals between nerve cells (neurons) in the autonomic nervous system. There are two main types of autonomic transmitters:

a. Sympathetic Transmitters: In the sympathetic division of the autonomic nervous system, the main neurotransmitter released by the presynaptic (pre-ganglionic) neuron is norepinephrine (noradrenaline). This neurotransmitter is responsible for activating the sympathetic response, which prepares the body for stressful situations, often referred to as the "fight-or-flight" response.

b. Parasympathetic Transmitters: In the parasympathetic division of the autonomic nervous system, the main neurotransmitter released by the presynaptic neuron is acetylcholine. This neurotransmitter is responsible for the rest-and-digest response, promoting relaxation and restoration.

2. Autonomic Receptors:
Autonomic receptors are proteins located on the surface of the target cells that receive the signals transmitted by autonomic transmitters. There are two primary types of autonomic receptors:

a. Adrenergic Receptors: Adrenergic receptors are receptors specific to norepinephrine. They are classified into two main subtypes: alpha-adrenergic receptors and beta-adrenergic receptors. Alpha receptors have subclasses, such as alpha-1 and alpha-2, whereas beta receptors have subclasses, such as beta-1, beta-2, and beta-3. These receptors mediate the effects of norepinephrine released by sympathetic nerve terminals.

b. Cholinergic Receptors: Cholinergic receptors are receptors specific to acetylcholine. They are divided into two main subtypes: nicotinic receptors and muscarinic receptors. Nicotinic receptors are found on post-ganglionic neurons in both the sympathetic and parasympathetic divisions, as well as on skeletal muscle cells. Muscarinic receptors are found on the target cells of the post-ganglionic parasympathetic neurons.

Now, let's understand how autonomic transmitters and receptors regulate effector cells that are dually innervated:

When an effector cell is dually innervated, it means that it receives input from both sympathetic and parasympathetic neurons. The balance between these two inputs determines the overall response of the effector cell.

For example, in the case of the heart, which is dually innervated, the sympathetic division of the autonomic nervous system releases norepinephrine, which binds to beta-adrenergic receptors on cardiac muscle cells. This increases heart rate and contractility, facilitating the "fight-or-flight" response.

In contrast, the parasympathetic division releases acetylcholine, which binds to muscarinic receptors on cardiac muscle cells. This decreases heart rate and contractility, promoting relaxation and restoration.

Overall, the autonomic transmitters and receptors work together to balance and regulate the activity of dually innervated effector cells, adapting the body's response to different situations and maintaining homeostasis.