Final answer:
Beta-1 adrenergic receptors increase heart rate and force of cardiac contraction, while Beta-2 receptors lead to smooth muscle relaxation and vasodilation. Alpha-1 receptors cause smooth muscle contraction, resulting in vasoconstriction and decreased salivation, and Alpha-2 receptors are involved in decreasing gastrointestinal motility.
Step-by-step explanation:
The question you've asked pertains to the pharmacological effects of different adrenergic receptors. When adrenaline or noradrenaline acts as receptor ligands on these receptors, they elicit various physiological actions:
- Beta-1 (B-1) adrenergic receptors increase the heart rate and force of cardiac contraction.
- Beta-2 (B-2) receptors are primarily involved in smooth muscle relaxation, such as in the bronchi, leading to bronchodilation and vasodilation in certain vascular beds.
- Alpha-1 (a1) adrenergic receptors lead to smooth muscle contraction, resulting in vasoconstriction and other effects such as decreased salivation and bronchoconstriction, although the latter is less significant compared to the relaxing effects of beta-2 receptors.
- Alpha-2 (a2) receptors inhibit insulin release and decrease cAMP activity, leading to smooth muscle contraction and decreased motility, particularly in the gastrointestinal tract.
Given these receptor effects, the correct response to the student's question are: a) Increased heart rate is associated with Beta-1 adrenergic receptor activation, and b) Smooth muscle contraction is linked to Alpha-1 adrenergic receptor activation. Hence the responses match each receptor with its respective physiologic action.