Which physiological effect would you expect from an increase in parasympathetic nervous system activity on the heart?

A. Hinge joint: Hinge joints allow movement primarily in one plane, such as flexion and extension, like the elbow or knee, limiting rotation and side-to-side motion.

B. Saddle joint: Saddle joints permit movement in two planes, such as flexion-extension and abduction-adduction, but do not allow full rotational movement.

C. Ball and socket joint: Ball and socket joints, like the shoulder and hip, have a spherical head fitting into a cup-like cavity, allowing multiaxial movement including flexion, extension, abduction, adduction, and rotation.

D. Pivot joint: Pivot joints allow rotational movement around a single axis, such as the atlantoaxial joint, but do not permit flexion or abduction.

A. Transmit electrical impulses: Transmission of electrical impulses along neurons is the function of the neurons themselves, not Schwann cells. Schwann cells support this process but do not directly carry impulses.

B. Form myelin sheaths around axons: Schwann cells do form the myelin sheath in the peripheral nervous system, which insulates axons and speeds up signal conduction. However, in the context of nerve repair, their guiding role is more critical.

C. Generate neurotransmitters: Neurotransmitters are produced by neurons at synaptic terminals to facilitate communication between cells. Schwann cells do not synthesize neurotransmitters.

D. Guide the regeneration of nerve fibers: During nerve injury, Schwann cells play a key role in repair by forming bands of Büngner that guide regrowing axons toward their target tissues. They also secrete growth factors that support axonal regeneration, making them essential for nerve fiber repair.