Study Guide: Nervous System, Special Senses, and Related Structures

The Brain: Major Structures

Brain Regions and Functions

The brain is divided into several regions, each with specialized functions.

• Cerebrum: Largest part; responsible for higher brain functions such as thought, memory, and voluntary movement.

• Cerebellum: Coordinates voluntary movements and balance.

• Diencephalon: Contains the thalamus and hypothalamus; relays sensory information and regulates autonomic functions.

• Brain Stem: Includes the midbrain, pons, and medulla oblongata; controls basic life functions like breathing and heart rate.

Example: The medulla oblongata regulates vital functions such as heart rate and respiration.

The Brain Stem

Components and Roles

• Midbrain: Processes visual and auditory information; controls eye movement.

• Pons: Relays signals between the cerebrum and cerebellum; involved in sleep and respiration.

• Medulla Oblongata: Controls autonomic functions such as heart rate, blood pressure, and digestion.

Example: Damage to the brain stem can affect breathing and consciousness.

Sagittal Section of the Head

Key Structures

A sagittal section divides the head into left and right halves, revealing internal structures.

• Cerebrum and Cerebellum: Visible in midline section.

• Corpus Callosum: Connects the two cerebral hemispheres.

• Ventricles: Cavities containing cerebrospinal fluid (CSF).

• Pituitary Gland: Endocrine gland at the base of the brain.

• Nasal Cavity, Oral Cavity, Pharynx: Structures of the respiratory and digestive tracts.

Example: The sagittal view is used to study the relationship between the brain and cranial nerves.

Ventricular System of the Brain

Ventricle Model Structures

• Lateral Ventricles: Paired cavities in each cerebral hemisphere.

• Third Ventricle: Located in the diencephalon.

• Cerebral Aqueduct: Connects the third and fourth ventricles.

• Fourth Ventricle: Located between the brainstem and cerebellum.

• Cerebrospinal Fluid (CSF): Circulates through the ventricles, cushioning the brain and removing waste.

Example: Blockage of the cerebral aqueduct can lead to hydrocephalus (accumulation of CSF).

Spinal Cord Anatomy

Spinal Cord Model 'A' and 'B'

• Gray Matter: Central region containing neuron cell bodies; shaped like a butterfly.

• White Matter: Outer region containing myelinated axons.

• Dorsal Root: Contains sensory neuron fibers entering the spinal cord.

• Ventral Root: Contains motor neuron fibers exiting the spinal cord.

• Central Canal: Runs through the center, containing CSF.

Example: Reflex arcs involve sensory input through the dorsal root and motor output through the ventral root.

Skin Receptors

Types and Functions

• Meissner's Corpuscles: Detect light touch.

• Pacinian Corpuscles: Detect deep pressure and vibration.

• Merkel Cells: Detect steady pressure and texture.

• Free Nerve Endings: Detect pain and temperature.

Example: Meissner's corpuscles are concentrated in fingertips for fine touch discrimination.

The Eye: Muscles and Glands

Eye Muscles and Lacrimal Gland

• Extraocular Muscles: Control eye movement (superior, inferior, medial, lateral rectus; superior and inferior oblique).

• Lacrimal Gland: Produces tears to lubricate and protect the eye.

Example: The lateral rectus muscle abducts the eye (moves it outward).

Eye Anatomy

Structures of the Eye Panel

• Cornea: Transparent front layer; refracts light.

• Iris: Colored part; controls pupil size.

• Pupil: Opening that regulates light entry.

• Lens: Focuses light onto the retina.

• Retina: Contains photoreceptors (rods and cones) for vision.

• Optic Nerve: Transmits visual information to the brain.

Example: The lens changes shape (accommodation) to focus on near or distant objects.

Ear Anatomy

Structures of the Ear Model

• Outer Ear: Auricle (pinna) and external auditory canal; collects sound waves.

• Middle Ear: Tympanic membrane (eardrum) and ossicles (malleus, incus, stapes); transmits vibrations.

• Inner Ear: Cochlea (hearing), vestibule, and semicircular canals (balance).

• Eustachian Tube: Equalizes pressure between middle ear and throat.

Example: The cochlea converts sound vibrations into nerve impulses sent to the brain.

Additional info: Academic context and definitions have been added to expand on the identification objectives listed in the original study guide, ensuring the notes are self-contained and suitable for exam preparation.