Nervous System Overview

Medical Terminology: Nervous System Word Roots

• neur/o, neuri/o: Nerve (e.g., Neuritis - inflammation of a nerve)
• encephal/o: Brain (e.g., Encephalitis - brain inflammation)
• myel/o: Spinal cord/bone marrow (e.g., Myelogram - spinal cord imaging)
• cephal/o: Head (e.g., Cephalalgia - headache)
• cerebr/o: Cerebrum (e.g., Cerebral cortex - outer brain surface)
• mening/o, meningi/o: Meninges (e.g., Meningitis - infection of meninges)
• dur/o: Dura mater (e.g., Epidural - outside the dura mater)
• gli/o: Glue (e.g., Glioblastoma - glial cell tumor)
• poli/o: Gray matter (e.g., Poliomyelitis - inflammation of gray spinal cord matter)
• radicul/o: Nerve root (e.g., Radiculopathy - nerve root pain/irritation)
• psych/o: Mind (e.g., Psychology - study of the mind)
• esthesi/o: Feeling/sensation (e.g., Anesthesia - loss of feeling)

Nervous System Structure

• Central Nervous System (CNS)

  • Located within skull and vertebral column
  • Components: Brain (cerebrum, diencephalon, brainstem, cerebellum), spinal cord
  • Protection: Bones, meninges, cerebrospinal fluid, blood-brain barrier
  • Functions: Sensory processing, motor responses, integration of memory/thought/emotion, reflex control

• Peripheral Nervous System (PNS)

  • Located outside CNS, connects CNS to the body
  • Components: Cranial nerves (12 pairs), spinal nerves (31 pairs), ganglia, sensory receptors
  • Functions: Carry sensory info to CNS, motor commands from CNS

PNS Functional Divisions

• Sensory (Afferent) Division: From receptors to CNS
• Motor (Efferent) Division: From CNS to effectors (muscles/glands)
  • Somatic Nervous System (SNS): Voluntary, controls skeletal muscles
  • Autonomic Nervous System (ANS): Involuntary, controls smooth muscle, cardiac muscle, glands
    • Sympathetic Division: "Fight or Flight"
    • Parasympathetic Division: "Rest and Digest"

Autonomic Nervous System (ANS)

• Controls automatic functions like heartbeat, breathing, digestion
• Sympathetic: Increases HR, dilates pupils, slows digestion
• Parasympathetic: Decreases HR, constricts pupils, speeds digestion

CNS + PNS Interaction

• Sensory input detected by PNS
• CNS processes information
• CNS directs PNS response

Neurons and Neuroglia

Neuron Anatomy

• Dendrites: Receive signals
• Cell Body (Soma): Contains nucleus
• Axon: Carries signal away
• Axon Terminals: Release neurotransmitters
• Myelin Sheath: Speeds transmission

Neuron Types

• Multipolar: Motor neurons, found in CNS
• Bipolar: Sensory, found in retina, nose, inner ear
• Unipolar: Sensory, found in skin, sensory organs

Neuroglia (Glial Cells)

• Support neurons
• CNS Glial Cells: Astrocytes, oligodendrocytes, ependymal cells, microglia
• PNS Glial Cells: Schwann cells, satellite cells

Meninges and Cerebrospinal Fluid (CSF)

Meninges

• Dura Mater: Outermost, thick/protective
• Arachnoid Mater: Middle layer, forms subarachnoid space
• Pia Mater: Innermost, carries blood vessels

Cerebrospinal Fluid (CSF)

• Cushions brain/spinal cord, removes waste, regulates chemical environment

Brain Anatomy and Function

Major Brain Regions

• Cerebrum: Largest, controls movement, memory, sensory interpretation
• Diencephalon: Thalamus and hypothalamus
• Brainstem: Connects brain to spinal cord, controls vital functions
• Cerebellum: Coordination, balance

Limbic System

• Controls memory and emotions
• Key structures: Hippocampus, amygdala, thalamus, olfactory bulb

Spinal Cord Anatomy

Spinal Cord Tracts

• Gray Matter: Processes information
• White Matter: Transmits signals

Cauda Equina

• Bundle of spinal nerves at lower end
• Clinical relevance: Cauda equina syndrome

Cranial Nerves

Cranial Nerve Functions

• I (Olfactory): Smell
• II (Optic): Vision
• III (Oculomotor): Eye movement
• IV (Trochlear): Eye movement
• V (Trigeminal): Facial sensation, chewing
• VI (Abducens): Eye movement
• VII (Facial): Facial expression, taste
• VIII (Vestibulocochlear): Hearing, balance
• IX (Glossopharyngeal): Taste, swallowing
• X (Vagus): Parasympathetic to organs
• XI (Accessory): Shoulder/head movement
• XII (Hypoglossal): Tongue movement

Synaptic Transmission and Reflex Arcs

Action Potentials

• All-or-nothing signals sent down axon

Reflex Arcs

• Pathway of automatic response: Receptor → Sensory neuron → Interneuron → Motor neuron → Effector

Disorders of the Nervous System

Common Disorders

• Alzheimer’s Disease: Abnormal protein buildup in brain
• Parkinson’s Disease: Death of dopamine-producing neurons
• Multiple Sclerosis: Immune attack on myelin sheath
• Stroke (CVA): Blood supply to brain interrupted
• Seizures/Epilepsy: Abnormal electrical activity in the brain

Medications

• Alzheimer's: Donepezil, Memantine
• Parkinson's: Levodopa, Dopamine agonists
• Multiple Sclerosis: Interferon beta, Glatiramer acetate
• Stroke: tPA for ischemic, surgery for hemorrhagic
• Seizures: Phenytoin, Valproic acid, Carbamazepine

Senses and Sensory Receptors

General vs Special Senses

• General Senses: Touch, pressure, temperature, pain
• Special Senses: Vision, hearing, taste, smell, balance

Sensory Receptors

• Thermoreceptors: Temperature
• Mechanoreceptors: Pressure, touch
• Nociceptors: Pain
• Photoreceptors: Light
• Chemoreceptors: Chemical levels

Vision and Hearing

Eye Anatomy

• Structures: Cornea, lens, retina

Ear Anatomy

• Structures: Outer, middle, inner ear

Equilibrium

• Static Equilibrium: Head position detection
• Dynamic Equilibrium: Rotational motion detection

Endocrine System Overview

Hormone Types

• Steroid Hormones: Lipid-soluble, affect gene expression
• Protein Hormones: Water-soluble, use second messengers

Major Endocrine Glands

• Hypothalamus: Controls pituitary
• Pituitary Gland: Secretes growth hormone, TSH, ACTH, etc.
• Thyroid Gland: Releases T3/T4, calcitonin
• Pancreas: Insulin, glucagon
• Adrenal Glands: Aldosterone, cortisol, epinephrine

Disorders

• Diabetes: Type 1 and 2, gestational
• Cushing’s Syndrome: Excess cortisol
• Addison’s Disease: Insufficient cortisol/aldosterone
• Thyroid Disorders: Hypo/hyperthyroidism

Study Tips

• Use mnemonics such as "FLAT PEG" for anterior pituitary hormones
• Remember key phrases like "Insulin = In (glucose into cells)" and "Steroids Slip Inside."