CENTRAL NERVOUS SYSTEM (CNS)
The central nervous system is the portion of the nervous system enclosed within the skull and vertebral canal, composed of the brain and spinal cord, responsible for thought, perception, movement, and regulation of vital functions.
CNS = Brain + Spinal Cord → Control, coordinate, and regulate all body activities.
Parts of CNS:
| Part | Subdivision | Main Functions |
|---|---|---|
| Brain | Cerebrum | Largest part, controls voluntary actions, intelligence, memory, emotions, language, sensory perception, decision making. |
| Cerebellum | Coordinates muscle activity, maintains balance and posture. | |
| Diencephalon (Thalamus & Hypothalamus) | Thalamus: relay center for sensory info; Hypothalamus: regulates body temperature, hunger, thirst, endocrine control. | |
| Brainstem (Midbrain, Pons, Medulla Oblongata) | Controls involuntary functions like heartbeat, breathing, swallowing, reflexes. | |
| Spinal Cord | — | Conducts signals between brain and body, controls reflex actions, control body. |
Protection of CNS:
| Protective Structure (Other Term) | Description / Role |
|---|---|
| Bony Protection (Skull & Vertebral Column) | The skull protects the brain, while the vertebral column encloses and shields the spinal cord from injury. |
| Meninges (Protective Membranes) | Three connective tissue layers: Dura mater (tough outer), Arachnoid mater (middle, web-like), Pia mater (delicate inner, adheres to brain/spinal cord). |
| Cerebrospinal Fluid (CSF) | Cushions brain & spinal cord, provides nutrients, removes waste, acts as a shock absorber. |
| Blood-Brain Barrier (BBB) | Selective permeability barrier that protects the brain from harmful substances in the blood while allowing essential nutrients. |
| Neuroglial Support | Specialized cells (astrocytes, microglia, oligodendrocytes) provide structural and immune support, further protecting CNS tissues. |
Function of CNS:
| Function | Description | Example |
|---|---|---|
| Sensory Function | Receives and interprets signals from sensory organs and body receptors | Feeling heat, seeing light, hearing sound |
| Motor Function | Controls voluntary and involuntary movements | Walking (voluntary), heartbeat (involuntary) |
| Integrative Function | Processes and analyzes incoming sensory information to make decisions | Deciding to remove hand from hot surface |
| Higher Mental Functions | Manages thinking, reasoning, memory, learning, language, emotions | Solving a problem, recalling a name, speaking |
| Homeostasis & Coordination | Maintains internal balance and coordinates muscle activity | Regulating body temperature, balance while walking |
| Reflex Actions | Provides quick, automatic responses through the spinal cord | Knee-jerk reflex, withdrawing from pain |
Disorders of CNS
1. Stroke:-
- Ischemic Stroke-Blood clot or blockage in an artery supplying the brain.
- Hemorrhagic Stroke- Ruptured blood vessel around the brain.
- Transient Ischemic Attack (TIA) (“mini-stroke”)- Temporary blockage of blood flow
3. Parkinson’s disease:- Degeneration of dopamine-producing neurons in the brain (basal ganglia)
4. Multiple sclerosis:- Autoimmune attack on myelin sheath of neurons
5. Meningitis:- Inflammation of meninges (caused by bacterial, viral, or fungal infection).
5. Meningitis:- Inflammation of meninges (caused by bacterial, viral, or fungal infection).
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