Question

While both __________ muscle in the heart and (blank) muscle tissue in the blood vessels are capable of initiating contraction on their own, _____ muscle tissue must be stimulated by motor neurons in groups called motor units.

Answer 1

Cardiac muscle in the heart and smooth muscle in blood vessels can contract autonomously, but skeletal muscle requires motor neuron stimulation.

Step-by-step explanation:

While both cardiac muscle in the heart and smooth muscle tissue in the blood vessels are capable of initiating contraction on their own, skeletal muscle tissue must be stimulated by motor neurons in groups called motor units.]

Cardiac muscle tissue is unique as it possesses autorhythmicity, meaning it can initiate an electrical potential that spreads rapidly from cell to cell to trigger contraction. This coordinated contraction maintains blood circulation and pressure. Unlike cardiac muscle, skeletal muscle requires the stimulation of motor neurons, which release neurotransmitters like acetylcholine to prompt muscle fibers to contract.

This stimulation forms part of a motor unit. In contrast, smooth muscle found in blood vessels can also contract rhythmically without nervous stimulation due to the activity of internal pacemaker cells.