Types of Nerves
Olfactory Nerve (I)
Sensory Nerve
Responsible for the sense of smell. Transmits sensory information from the nasal cavity to the brain.
Optic Nerve (II)
Sensory Nerve
Transmits visual information from the retina to the brain. Essential for vision.
Oculomotor Nerve (III)
Motor Nerve
Controls most eye movements, pupil constriction, and eyelid elevation.
Trochlear Nerve (IV)
Motor Nerve
Controls the superior oblique muscle of the eye, enabling downward and inward eye movement.
Trigeminal Nerve (V)
Mixed Nerve
Provides sensation to the face and controls muscles used for chewing.
Abducens Nerve (VI)
Motor Nerve
Controls the lateral rectus muscle, enabling outward eye movement.
Facial Nerve (VII)
Mixed Nerve
Controls facial expressions, taste sensation from anterior tongue, and lacrimal/salivary glands.
Vestibulocochlear (VIII)
Sensory Nerve
Responsible for hearing (cochlear nerve) and balance (vestibular nerve).
Glossopharyngeal (IX)
Mixed Nerve
Controls swallowing, taste from posterior tongue, and monitors blood pressure.
Vagus Nerve (X)
Mixed Nerve
The longest cranial nerve with both sensory and motor functions. Affects heart, lungs, and digestive tract.
Accessory Nerve (XI)
Motor Nerve
Controls the sternocleidomastoid and trapezius muscles for head and shoulder movements.
Hypoglossal Nerve (XII)
Motor Nerve
Controls tongue movements for speech, swallowing, and chewing.
Cervical Nerves (C1-C8)
Mixed Nerves
Eight pairs of nerves emerging from the cervical vertebrae. Control neck, shoulders, arms, and diaphragm.
Thoracic Nerves (T1-T12)
Mixed Nerves
Twelve pairs of nerves that control chest, abdominal muscles, and back sensation.
Lumbar Nerves (L1-L5)
Mixed Nerves
Five pairs of nerves that control hip and leg muscles, and sensation in the lower body.
Sacral Nerves (S1-S5)
Mixed Nerves
Five pairs of nerves that control bladder, bowel, sexual function, and leg/foot muscles.
Sciatic Nerve
Mixed Nerve
Largest and longest nerve in the human body. Runs from lower back through hips and down each leg.
Phrenic Nerve
Mixed Nerve
Controls the diaphragm muscle, essential for breathing.
Median Nerve
Mixed Nerve
Runs from the brachial plexus into the forearm and hand. Provides motor and sensory functions to parts of the hand.
Ulnar Nerve
Mixed Nerve
Runs from the brachial plexus to the hand. Controls fine movements of the fingers and provides sensation.
Radial Nerve
Mixed Nerve
Provides motor function to the triceps and extensors of the wrist and fingers. Also provides sensory information.
Femoral Nerve
Mixed Nerve
Innervates muscles of the thigh and leg, and provides sensation to the anterior thigh and medial leg.
Tibial Nerve
Mixed Nerve
Innervates muscles of the calf and foot, and provides sensation to the sole of the foot.
Sympathetic Nerves
Autonomic Nerve
Part of the autonomic nervous system responsible for "fight or flight" responses.
Parasympathetic Nerves
Autonomic Nerve
Part of the autonomic nervous system responsible for "rest and digest" functions.
Loading nerve details...
Nerve Detail
Overview
Select a nerve to view detailed information.
Function
Function details will appear here.
Pathway
Pathway information will appear here.
Clinical Significance
Clinical information will appear here.
Common Disorders
Disorder information will appear here.
Examination
Examination techniques will appear here.
Did You Know?
The human nervous system consists of approximately 86 billion neurons and a similar number of glial cells. If all the neurons in a single human brain were lined up, they would stretch over 600 miles. The sciatic nerve is the longest and widest single nerve in the human body, running from the lower back to the toes.
Nerve Functions
Sensory Functions
Nerves transmit sensory information from receptors to the central nervous system, allowing us to perceive touch, pain, temperature, pressure, and proprioception.
Motor Functions
Motor nerves carry signals from the brain and spinal cord to muscles and glands, controlling voluntary and involuntary movements and secretions.
Autonomic Functions
Autonomic nerves regulate involuntary body functions including heart rate, digestion, respiratory rate, pupillary response, and sexual arousal.
Integrative Functions
Nerves process and integrate sensory information to coordinate appropriate motor responses, enabling complex behaviors and reflexes.
Reflex Functions
Reflex arcs allow for rapid, automatic responses to stimuli without conscious thought, providing protective mechanisms for the body.
Cognitive Functions
Nerves in the central nervous system support higher cognitive functions including memory, learning, reasoning, and emotional processing.
Comparison of Nerve Types
| Nerve Type | Function | Examples | Speed of Conduction |
|---|---|---|---|
| Sensory Nerves | Carry information from receptors to CNS | Optic, Olfactory, Auditory | Varies (5-120 m/s) |
| Motor Nerves | Carry commands from CNS to muscles/glands | Oculomotor, Hypoglossal | Fast (up to 120 m/s) |
| Mixed Nerves | Both sensory and motor functions | Trigeminal, Vagus, Spinal nerves | Varies by fiber type |
| Autonomic Nerves | Control involuntary functions | Sympathetic, Parasympathetic | Slow (0.5-2 m/s) |
Nervous System Diagram
Visual representation of the major nerves in the human body
Neurological Disorders
Neuropathy
Damage or dysfunction of one or more nerves, typically causing numbness, tingling, muscle weakness, and pain in the affected area.
Common causes: Diabetes, alcoholism, autoimmune diseases, infections.
Multiple Sclerosis
An autoimmune disease where the immune system attacks the protective sheath (myelin) that covers nerve fibers, causing communication problems between the brain and the rest of the body.
Symptoms: Fatigue, numbness, walking difficulties, vision problems.
Carpal Tunnel Syndrome
Compression of the median nerve as it travels through the wrist, causing numbness, tingling, and weakness in the hand and arm.
Treatment: Wrist splinting, NSAIDs, corticosteroid injections, surgery.
Bell's Palsy
Sudden weakness or paralysis of facial muscles due to inflammation or damage to the facial nerve (cranial nerve VII).
Recovery: Most people recover fully within 6 months with or without treatment.
Guillain-Barré Syndrome
A rare disorder where the body's immune system attacks the peripheral nerves, leading to muscle weakness and paralysis.
Treatment: Plasma exchange, immunoglobulin therapy, rehabilitation.
Trigeminal Neuralgia
A chronic pain condition affecting the trigeminal nerve (cranial nerve V), causing extreme, sporadic, sudden burning or shock-like facial pain.
Treatment: Anticonvulsant medications, surgery in severe cases.
Nervous System Development Timeline
Week 3 of Embryonic Development
Neural plate forms from ectoderm, which then folds to form the neural tube.
Week 4
Neural tube closes. Brain vesicles form (forebrain, midbrain, hindbrain).
Weeks 5-8
Major brain regions develop. Cranial nerves begin to form. Spinal nerves extend into limb buds.
Month 3
Rapid neuron production (neurogenesis). Synapses begin to form.
Months 4-6
Myelination begins. Sensory and motor pathways develop.
Birth to 2 Years
Rapid brain growth and synaptic pruning. Motor skills develop.