Nerves and Reflexes

Vocabulary flashcards covering the organization of the nervous system, classifications of the twelve cranial nerves, and the components of a reflex arc.

Central Nervous System (CNS)

The main part of the nervous system comprised of the brain and the spinal cord.

Peripheral Nervous System (PNS)

Consists of all neural tissue outside the CNS, such as peripheral nerves.

Cranial nerves

Twelve pairs of nerves numbered using Roman numerals ($I$ – $XII$) from front to back, almost all of which work locally in the head and neck region.

Vagus nerve (X)

The cranial nerve that leaves the head-neck region and passes down to the thoracic and abdominal cavities.

Exclusively sensory cranial nerves

Cranial nerves that only carry sensory information, including the Olfactory nerve fibers ($I$), Optic nerve ($II$), and Vestibulocochlear nerve ($VIII$).

Exclusively motor cranial nerves

Cranial nerves that only carry motor signals, including the Oculomotor nerve ($III$), Trochlear nerve ($IV$), Abducens nerve ($VI$), Accessory nerve ($XI$), and Hypoglossal nerve ($XII$).

Mixed cranial nerves

Cranial nerves that have both sensory and motor functions, including the Trigeminal nerve ($V$), Facial nerve ($VII$), Glossopharyngeal nerve ($IX$), and Vagus nerve ($X$).

Reflex

An automatic and often inborn response to a stimulus involving a nerve impulse passing from a receptor to the spinal cord and then to an effector without reaching the level of consciousness.

Receptor

The first component of a reflex that receives the initial stimulus.

Afferent (sensory) nerve

The nerve that carries the impulse inward from a receptor to the spinal cord during a reflex.

Reflex centre (Integration centre)

The area where the sensory impulse is processed to create a response, typically within the spinal cord.

Efferent (motor) nerve

The nerve that passes an impulse outward from the spinal cord to an effector organ.

Effector organ

The muscle or gland that receives the motor impulse and carries out the reflex action.