Study Guide: Central Nervous System and Brain Anatomy

Central Nervous System and Brain Anatomy

Cerebrum Structure and Function

The cerebrum is the largest part of the brain, responsible for higher brain functions such as thought, action, and sensory processing.

• Cerebral Cortex: The outer layer of the cerebrum, composed primarily of gray matter (neuron cell bodies).

• White Matter: Located beneath the cortex, consisting of myelinated axons that connect different brain regions.

• Central Sulcus: A prominent groove that separates the frontal and parietal lobes.

• Lateralization: Refers to the division of certain functions between the left and right hemispheres of the brain.

Example: The left hemisphere is typically specialized for logic, math, and language, while the right hemisphere is more involved in spatial and creative tasks.

Ventricular System

The brain contains interconnected cavities called ventricles, which produce and circulate cerebrospinal fluid (CSF).

• Lateral Ventricles: Paired structures separated by the septum pellucidum.

• Third Ventricle: Connected to each lateral ventricle via the interventricular foramen.

• Cerebral Aqueduct: Connects the third and fourth ventricles.

• Choroid Plexus: Specialized tissue within the ventricles that produces CSF.

• CSF Volume: The adult brain contains about 150 mL of CSF at any one time.

Major Brain Regions and Their Functions

• Cerebellum: Coordinates skeletal muscle movements and balance; involved in motor control and some cognitive functions.

• Brainstem: Includes the midbrain, pons, and medulla oblongata; controls vital functions such as heart rate, breathing, and reflexes.

• Thalamus: Acts as a relay station for sensory information.

• Hypothalamus: Regulates homeostatic functions such as hunger, thirst, sleep-wake cycles, and body temperature.

• Pineal Gland: Secretes melatonin, which regulates circadian rhythms.

Cerebral Lobes and Functional Areas

• Frontal Lobe: Contains the primary motor cortex (precentral gyrus), responsible for voluntary movement; also includes Broca's area (speech production).

• Parietal Lobe: Contains the primary somatosensory cortex (postcentral gyrus), which processes sensory input from the body.

• Temporal Lobe: Contains the primary auditory cortex and Wernicke's area (language comprehension).

• Occipital Lobe: Contains the primary visual cortex.

Commissural, Association, and Projection Fibers

These fibers connect different regions of the brain:

• Commissural Fibers: Connect corresponding regions of the two hemispheres (e.g., corpus callosum).

• Association Fibers: Connect different parts of the same hemisphere.

• Projection Fibers: Connect the cerebrum with lower brain regions and the spinal cord.

Meninges and CSF Circulation

The brain and spinal cord are protected by three connective tissue membranes called meninges:

• Dura Mater: Tough, outermost layer.

• Arachnoid Mater: Middle, web-like layer.

• Pia Mater: Thin, innermost layer adhering to the brain surface.

CSF circulates through the ventricles, central canal, and subarachnoid space, providing cushioning and nutrient transport.

Cranial Nerves

There are 12 pairs of cranial nerves, each with specific sensory and/or motor functions.

• Optic Nerve (II): Responsible for vision.

• Vagus Nerve (X): Unique because it controls many autonomic functions and innervates organs beyond the head and neck.

Functional Brain Areas

• Broca's Area: Speech production.

• Wernicke's Area: Language comprehension.

• Primary Motor Cortex: Voluntary movement control.

• Primary Somatosensory Cortex: Receives sensory input from the body.

• Vestibular Cortex: Awareness of balance and head position.

• Autonomic Cortex: Receives signals mainly from the hypothalamus, regulating involuntary functions.

Table: Major Brain Regions and Their Functions

Region	Main Function(s)
Cerebrum	Higher cognitive functions, voluntary movement, sensory processing
Cerebellum	Coordination of movement, balance
Brainstem	Autonomic functions, reflexes
Thalamus	Sensory relay station
Hypothalamus	Homeostasis, endocrine regulation
Pineal Gland	Melatonin secretion, circadian rhythms

Additional info:

• The basal nuclei (basal ganglia) are involved in the regulation of voluntary motor movements and procedural learning.

• The reticular formation is a network within the brainstem that regulates alertness and sleep-wake transitions.

• The meninges protect the central nervous system and help circulate CSF.