Central Nervous System: Structure, Function, and Homeostasis

Module 12.1 Overview of the Central Nervous System

Central Nervous System (CNS): Structure and Function

The central nervous system (CNS) consists of the brain and spinal cord. It is responsible for integrating sensory information, controlling movement, maintaining homeostasis, and higher mental functions such as cognition and emotion.

• Motor functions: Initiate muscle contractions or gland secretions. The CNS sends signals to the peripheral nervous system (PNS) to execute these actions.

• Sensory functions: Detect and process sensations from inside and outside the body.

• Integrative functions: Involve decision-making and higher-order processing unique to the CNS.

Basic Structure of the Brain and Spinal Cord

• The brain is continuous with the spinal cord and is protected by the cranial cavity.

• Four major divisions of the brain:

  1. Cerebrum: Largest part, divided into left and right hemispheres. Functions: Higher mental functions (learning, memory, personality, cognition, language, consciousness), and voluntary movement.

  2. Diencephalon: Deep beneath the cerebrum. Functions: Processing, integrating, and relaying information; homeostasis; regulation of movement; biological rhythms.

  3. Cerebellum: Posterior and inferior to cerebrum. Functions: Planning and coordination of movement.

  4. Brainstem: Connects brain to spinal cord. Functions: Basic involuntary homeostatic functions, control of certain reflexes, monitoring movement, integrating and relaying information.

• White matter: Bundles of myelinated axons (tracts) for rapid communication.

• Gray matter: Clusters of neuron cell bodies, dendrites, and unmyelinated axons.

Module 12.2 The Brain

Gross Anatomy and Lobes of the Cerebrum

The cerebrum is responsible for higher mental functions. Its surface contains gyri (ridges), sulci (grooves), and fissures (deep grooves).

• Lobes of the cerebrum:

  • Frontal lobes: Anterior; contains the precentral gyrus (primary motor cortex). Functions: Planning, executing movement, complex mental functions (behavior, conscience, personality).

  • Parietal lobes: Posterior to frontal; contains the postcentral gyrus (primary somatosensory cortex). Functions: Processing/integrating sensory information, attention.

  • Temporal lobes: Lateral surfaces. Functions: Hearing, language, memory, emotions.

  • Occipital lobes: Posterior; separated by parieto-occipital sulcus. Functions: Vision.

Cerebral Cortex: Functional Areas

• Neocortex: Most of the cerebral cortex; involved in higher-order functions.

• Primary motor cortex: Located in precentral gyrus. Function: Plan and execute movement.

• Primary sensory cortices: Receive/process sensory input (e.g., somatosensory, visual, auditory, gustatory, olfactory, vestibular).

• Association areas: Integrate information, perform complex functions.

  • Unimodal association areas: Process one type of sensory input.

  • Multimodal association areas: Integrate information from multiple senses.

Key Functional Regions

• Broca's area: Frontal lobe; production of speech.

• Wernicke's area: Temporal/parietal lobe; understanding language.

• Prefrontal cortex: Most of frontal lobe; planning, behavior, personality, learning, memory.

• Basal nuclei: Deep within cerebral hemispheres; involved in movement.

• Limbic system: Includes hippocampus, amygdala; involved in memory, learning, emotion, behavior.

Diencephalon

• Thalamus: Main entry to cerebral cortex; relays sensory input.

• Hypothalamus: Regulates autonomic nervous system, sleep-wake cycle, thirst, hunger, body temperature; links to pituitary gland.

• Epithalamus: Contains pineal gland; secretes melatonin (sleep-wake cycle).

• Subthalamus: Controls movement with basal nuclei.

Cerebellum

• Posterior/inferior to cerebrum; coordinates movement, maintains balance and posture.

Brainstem

• Vital for survival; controls basic homeostatic functions (breathing, heart rate).

• Subdivisions: Midbrain, pons, medulla oblongata.

• Reticular formation: Network involved in sleep, pain, consciousness, muscle tone.

Module 12.3 Homeostasis: Role of the CNS

Homeostasis and the CNS

Homeostasis is the maintenance of a stable internal environment. The CNS, especially the hypothalamus and reticular formation, is essential for regulating homeostatic mechanisms.

• Autonomic nervous system (ANS): Controls involuntary functions (heart rate, blood pressure, digestion).

• Endocrine system: Works with the CNS to regulate homeostasis via hormones.

Vital Functions

• Regulated by the autonomic nervous system and reticular formation.

• Examples: Heart rate, blood pressure, breathing, digestion.

Key Terms and Definitions

• Gyri: Ridges on the surface of the brain.

• Sulci: Grooves between gyri.

• Fissures: Deep grooves in the brain.

• Tracts: Bundles of myelinated axons in the CNS.

• Gray matter: Neuron cell bodies, dendrites, unmyelinated axons.

• White matter: Myelinated axons.

Summary Table: Major Divisions and Functions of the Brain

Division	Main Functions
Cerebrum	Higher mental functions, voluntary movement, sensory processing
Diencephalon	Relay sensory info, homeostasis, hormone regulation
Cerebellum	Coordination of movement, balance, posture
Brainstem	Basic life functions, reflexes, relay between brain and spinal cord

Additional info:

• Some details, such as the specific locations of certain cortical areas, were inferred based on standard anatomical knowledge.

• All equations and formulas are not directly relevant to this content, as the focus is on anatomical structures and physiological functions.