Central Nervous System Quiz

The control center of the body, composed of the brain and spinal cord, responsible for processing information and coordinating actions.

The network of nerves connecting the CNS to the rest of the body, relaying sensory information and carrying motor commands.

The part of the PNS that controls involuntary functions like heart rate, digestion, and breathing.

The area of the brain responsible for processing sensory information from the body.

The area of the brain responsible for initiating and controlling voluntary muscle movements.

Ganglion cells are neurons in the retina that receive input from bipolar cells. There are two main types: ON-center and OFF-center ganglion cells.

ON-center ganglion cells fire more action potentials when light is shone on the center of their receptive field, while OFF-center ganglion cells fire more action potentials when light is shone on the periphery of their receptive field.

A receptive field is the area in which stimulation leads to a response from a particular sensory neuron. For example, the receptive field of a ganglion cell in the retina is the area of the retina that it receives input from.

Bipolar cells are neurons in the retina that receive input from photoreceptor cells and transmit signals to ganglion cells. They express two types of receptors: excitatory and inhibitory, which help determine the response of the ganglion cell.

Midget ganglion cells are relatively small and have a small receptive field, responsible for fine visual detail, especially in the fovea. Parasol are larger, have larger receptive fields, and contribute to the perception of motion and overall pattern recognition in the visual field.

Several cranial nerves are responsible for controlling eye movements, sensing vision, and providing sensory information from the face and eye. These include: Optic nerve (CN II), Oculomotor nerve (CN III), Trochlear nerve (CN IV), Trigeminal nerve (CN V), Abducens nerve (CN VI), and Facial nerve (CN VII).

The optic nerve carries visual information from the retina to the brain.

The oculomotor nerve controls the movement of most of the eye muscles, including those that raise the eyelid.

A reflex that controls pupil size in response to light changes.

• Direct light reflex: Pupil constriction in the eye exposed to light.
• Consensual light reflex: Pupil constriction in the opposite eye.

Pupil constriction, which occurs when the iris muscle contracts, reducing the size of the pupil.

Pupil dilation, which occurs when the iris muscle relaxes, allowing the pupil to widen.

The sensory pathway that transmits light information from the retina to the midbrain. This pathway involves the retina, optic nerve, optic chiasma, optic tract, and pretectal nucleus.

The motor pathway that carries signals from the midbrain to the iris muscle, controlling pupil constriction. This pathway involves the pretectal nucleus, visceral E-W nucleus (CN III), and oculomotor nerve.

The third cranial nerve, responsible for controlling most eye movements, pupillary constriction, and lens accommodation. It is a motor nerve that innervates four extraocular muscles: superior rectus, inferior rectus, medial rectus, and inferior oblique.

The Oculomotor nerve (CNIII) innervates the following:

• Superior rectus muscle (elevates the eye)
• Inferior rectus muscle (depresses the eye)
• Medial rectus muscle (adducts the eye)
• Inferior oblique muscle (elevates the eye and turns it out)

The oculomotor nerve (CNIII) control the sphincter pupillae muscle, which is responsible for constricting the pupil in response to light.

The oculomotor nerve (CNIII) also controls the ciliary muscle, which is responsible for changing the shape of the lens for near vision accommodation - focusing on close objects.

The fourth cranial nerve, responsible for innervating the superior oblique muscle, which is an extraocular muscle of the eye. It primarily controls downward and outward movement of the eye.

The sixth cranial nerve responsible for innervating the lateral rectus muscle, which is an extraocular muscle of the eye. It primarily controls the abduction (moving the eye away from the nose) of the eye.

These three cranial nerves (III, IV, and VI) are responsible for controlling eye movements. CNIII (Oculomotor) controls most eye movements, as well as pupillary constriction and lens accommodation. CNIV (Trochlear) controls downward and outward movement of the eye. CNVI (Abducens) controls the abduction (moving the eye away from the nose) of the eye.

The oculomotor nerve (CNIII) plays a role in the Autonomic Nervous System (ANS) through its parasympathetic pathways. It controls the pupil constriction (sphincter pupillae) and lens accommodation (ciliary muscle) functions.

A small muscle located near the eyebrow that pulls it downwards and inwards, creating a frown. It's also involved in protecting the eyes from strong sunlight.

A condition causing facial muscle paralysis on one side, often due to the Herpes Simplex I virus. It leads to drooping eyelids, a sagging mouth, and inability to completely close the eye.

The nasociliary nerve, a branch of the ophthalmic division of the Trigeminal nerve, provides sensory innervation to the cornea.

Ciliary nerves, both long and short, connect the ciliary ganglion to the eye. They carry fibers from the Oculomotor nerve, providing parasympathetic innervation for iris and ciliary muscle.

The ophthalmic division of the trigeminal nerve (V1) supplies sensory innervation to the cornea, forehead, and upper part of the face.

The trigeminal nerve carries sensory information from the face and scalp, including the cornea, ciliary body, iris, lacrimal gland, conjunctiva, nasal cavity, eyelids, eyebrow, forehead, and nose. It also supplies sympathetic fibers for pupil dilation.

The ophthalmic division of the trigeminal nerve has three branches: the lacrimal nerve, the frontal nerve, and the nasociliary nerve.

The nasociliary nerve, a branch of the ophthalmic division, provides sensory innervation to the superior bulbar conjunctiva and the superior fornix. The lacrimal branch of the ophthalmic division innervates the lateral side of the inferior palpebral conjunctiva and the inferior fornix. Finally, the infraorbital nerve of the maxillary division innervates the medial side of the inferior palpebral conjunctiva and the inferior fornix.

The orbicularis oculi muscle is responsible for closing the eyelids. It's the only muscle that can perform this action.

Loss of orbicularis oculi function makes it impossible to close the eye, leaving it vulnerable to damage and infection. This necessitates using eye drops to keep the eye moist and prevent dryness, and in extreme cases, even removal of the eye may be required.

Besides controlling facial expressions, the facial nerve provides motor innervation to the orbicularis oculi muscle, which is essential for closing the eyelids. It also carries parasympathetic fibers to the lacrimal gland, controlling the production of tears.