How the Nervous System Connects to the Body: Muscles, Glands, Organs, and Senses

The nervous system is the body's communication network, linking the central command (brain, spinal cord) to every effector and sensor.

1. Muscles (Somatic Motor)

Alpha motor neurons → neuromuscular junctions → skeletal muscle contraction. Enables voluntary movement and reflexes.

2. Glands (Autonomic Motor)

• Sympathetic: Adrenal medulla (epinephrine), sweat glands, salivary glands (thick saliva).
• Parasympathetic: Lacrimal, salivary (watery), digestive glands (acid, enzymes), pancreatic bicarbonate.

3. Sensory Receptors (Afferent)

• Mechanoreceptors (touch, pressure, proprioception).
• Thermoreceptors (hot/cold).
• Nociceptors (pain).
• Photoreceptors (vision), hair cells (hearing/balance), chemoreceptors (taste/smell).

4. Internal Organs (Visceral Motor + Sensory)

Autonomic nerves (vagus, splanchnics) regulate heart rate, BP, bronchial tone, GI motility, secretion, bladder detrusor, sexual response. Visceral afferents signal distension, ischemia, chemical changes.

5. Central Processing

• Spinal cord: Reflex arcs, ascending/descending tracts.
• Brainstem: Vital centers (respiratory, cardiac, arousal), cranial nerves.
• Cerebellum: Coordination, motor learning.
• Thalamus: Sensory relay (except olfaction).
• Cerebral cortex: Perception, planning, cognition, emotion.

This integrated network maintains homeostasis and enables adaptive behavior.