Reflex Arcs - Anatomy & Physiology

• The reflex arc is the basic functional unit of the nervous system and consists of 2 linked components: the sensory input and the output response.

Detection via sensory receptors e.g:	Response via effectors e.g:
Skin receptors	Skeletal Muscle
Muscle Spindles	Smooth Muscle
Retina	.
Organ of Corti	.
Olfactory Mucosa	.

• Animals are divided into body segments, according to the segmental nature of the spinal cord.
  • Reflex arcs may involve a single segment, or mutliple segments up and down the body.
  • However, reflex arcs do not require brain input in order to function.
• The brain can act to modulate reflex; for example, some reflex pathways may be inhibited by the brain.
  • The brain obtains its afferent information via the ascending sensory tracts of the spinal cord.
  • The descending tracts originate from the brain to allow responses to be modulated.
  • These tracts constitute the white matter of the spinal cord.