Overview
The nervous system receives sensory information, processes it, and coordinates the body’s responses.
It controls movement, sensation, thinking, memory, emotions, and involuntary functions such as breathing, heart rate, and digestion.
The two main anatomical divisions are:
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Nerves and ganglia outside the CNS that carry information between the CNS and the body.
The nervous system works closely with the Sensory Organs to detect and interpret changes in the environment.
Major Structures
Central Nervous System (CNS)
- Brain: Main control center responsible for processing information and coordinating body functions.
- Cerebrum: Conscious thought, memory, language, sensory interpretation, and voluntary movement.
- Cerebellum: Coordination, balance, posture, and motor learning.
- Brainstem: Connects the brain with the spinal cord and helps regulate essential functions.
- Midbrain: Movement control and visual and auditory reflexes.
- Pons: Breathing regulation, sleep, and communication between brain regions.
- Medulla Oblongata: Breathing, heart rate, blood pressure, and protective reflexes.
- Diencephalon: Region containing structures including the thalamus and hypothalamus.
- Thalamus: Relays most sensory information to the cerebral cortex.
- Hypothalamus: Regulates temperature, hunger, thirst, sleep, and endocrine activity.
- Spinal Cord: Transmits signals between the brain and body and coordinates many reflexes.
- Meninges: Three protective membranes surrounding the brain and spinal cord.
- Cerebrospinal Fluid (CSF): Cushions the CNS and helps maintain its environment.
Peripheral Nervous System (PNS)
- Cranial Nerves: Twelve pairs of nerves associated with the brain and brainstem that support functions such as facial sensation, vision, eye movement, hearing, and swallowing.
- Spinal Nerves: Thirty-one pairs of nerves connecting the spinal cord to the body.
- Sensory (Afferent) Nerves: Carry information from receptors toward the CNS.
- Motor (Efferent) Nerves: Carry commands from the CNS toward muscles and glands.
Functional Divisions
- Somatic Nervous System: Supports conscious sensation and voluntary skeletal muscle movement.
- Autonomic Nervous System (ANS): Regulates involuntary functions such as heart rate, digestion, and blood vessel diameter.
- Sympathetic: Supports the fight-or-flight response.
- Parasympathetic: Supports rest-and-digest functions.
- Enteric Nervous System: Network of neurons within the gastrointestinal tract that helps regulate digestion.
Nervous Tissue
- Neurons: Cells specialized for transmitting electrical and chemical signals.
- Dendrites: Receive incoming information.
- Cell Body: Contains the nucleus and supports the neuron.
- Axon: Conducts nerve impulses away from the cell body.
- Myelin Sheath: Insulates many axons and increases signal conduction speed.
- Synapses: Junctions where neurons communicate with other cells.
- Neurotransmitters: Chemical messengers used for communication at many synapses.
- Glial Cells: Cells that support, protect, nourish, and insulate neurons.
Key Processes
- Sensory Reception: Specialized receptors detect stimuli such as light, sound, touch, temperature, and pain.
- Sensory Processing: The CNS interprets information received from sensory receptors.
- Motor Control: Nerve signals activate muscles to produce movement.
- Reflexes: Rapid, often automatic responses to stimuli; some involve the spinal cord without requiring initial conscious processing.
- Nerve Impulse Transmission: Electrical signals called action potentials travel along neurons.
- Synaptic Transmission: Signals pass between cells through neurotransmitters or electrical connections.
- Autonomic Regulation: Controls many involuntary activities.
- Homeostasis: Helps maintain stable internal conditions.
- Learning and Memory: Neural networks acquire, retain, and retrieve information.
- Neuroplasticity: Neural connections can change through experience, learning, and recovery.
Effects of Aging
- Slower Reaction Times: Responses to stimuli may take longer.
- Changes in Sensation: Some people experience reduced sensitivity to touch, vibration, or temperature.
- Changes in Balance: Altered sensory processing and motor control may affect stability.
- Sleep Changes: Sleep patterns and circadian rhythms may change.
- Changes in Memory Processing: Some forms of recall and information processing may become slower.
- Reduced Autonomic Responsiveness: Blood pressure regulation during position changes may become less effective.
Clinical Implications
- Increased risk of falls when balance, coordination, or reaction time is impaired.
- More time may be needed for communication and movement.
- Sensory impairments may affect safety and independence.
- Changes in position may increase dizziness in some residents.
- Acute illness can increase vulnerability to delirium.
Important: Dementia, sudden confusion, new paralysis, and major neurological deficits are not normal consequences of aging.
See Effects of Aging - Systems & Clinical Implications and Sensory Organs.
Common Diseases & Disorders
| Condition | Description | Common Causes / Risk Factors | CNA Considerations |
|---|---|---|---|
| Stroke (CVA) | Brain injury caused by blocked blood flow (ischemic) or bleeding (hemorrhagic) | Hypertension, atrial fibrillation, diabetes, smoking, atherosclerosis | Recognize sudden facial drooping, weakness, speech or vision changes; activate emergency response |
| Transient Ischemic Attack (TIA) | Temporary neurological dysfunction from interrupted blood flow without acute infarction; important warning sign for stroke | Similar risk factors to ischemic stroke | Treat stroke-like symptoms as an emergency, even if they resolve |
| Alzheimer’s Disease | Progressive brain disease affecting memory, thinking, and independence; common cause of dementia | Age, genetics, family history, cardiovascular risk factors | Use clear communication, familiar routines, and individualized assistance |
| Parkinson’s Disease | Progressive disorder involving loss of dopamine-producing neurons, often affecting movement | Age, genetics, certain environmental exposures | Observe tremor, rigidity, slowed movement, balance changes, and swallowing problems |
| Epilepsy / Seizure Disorders | Conditions involving a lasting tendency toward recurrent seizures | Genetics, brain injuries, stroke, infections, structural brain abnormalities | Protect from injury, time events, summon help, and never restrain or place objects in the mouth |
| Peripheral Neuropathy | Damage to peripheral nerves causing numbness, tingling, pain, or weakness | Diabetes, vitamin deficiencies, alcohol-related damage, medications | Observe sensory loss, mobility changes, and injury risk |
| Multiple Sclerosis (MS) | Immune-mediated damage to the CNS, including myelin | Genetic and environmental factors; precise cause unknown | Observe weakness, fatigue, balance changes, and functional decline |
| Meningitis | Inflammation of membranes surrounding the brain and spinal cord | Bacterial, viral, or other infections | Report fever, severe headache, neck stiffness, or altered mental status urgently; follow precautions |
| Delirium | Acute disturbance in attention and awareness that often fluctuates | Infection, dehydration, medications, surgery, metabolic disturbances | Report sudden changes in attention, behavior, or consciousness promptly |
| Dementia | Syndrome of persistent acquired cognitive decline interfering with daily function | Alzheimer’s disease, vascular disease, Lewy body disease, and others | Support independence, communication, routine, and safety |
| Spinal Cord Injury (SCI) | Damage to the spinal cord that may impair movement, sensation, and autonomic functions below the injury | Falls, vehicle collisions, trauma, violence, sports injuries | For suspected acute injury, summon emergency help and avoid unnecessary movement; follow established mobility precautions |
| Traumatic Brain Injury (TBI) | Brain injury caused by external force; may be penetrating or nonpenetrating | Falls, collisions, blows to the head, penetrating injuries | Report head injuries and changes in consciousness, behavior, speech, or movement; follow emergency procedures |
Important Distinctions
- Dementia vs. Alzheimer’s disease: Dementia is a syndrome; Alzheimer’s is one possible cause.
- Delirium vs. dementia: Delirium develops acutely and often fluctuates; dementia usually progresses more gradually.
- Stroke vs. TIA: Stroke causes brain infarction or hemorrhage; TIA causes transient ischemic symptoms without acute infarction. Both require emergency evaluation.
- SCI vs. TBI: Spinal cord injury primarily affects spinal nerve pathways; traumatic brain injury affects the brain. Trauma can cause both.
- Seizures: Not all seizures involve convulsions; some involve staring, altered awareness, or unusual movements.
Important: CNAs observe, support, and report rather than independently diagnosing neurological disorders.
When to Report
- New confusion, disorientation, or unexpected behavior.
- New weakness, numbness, tingling, or loss of sensation.
- Changes in walking, balance, or coordination.
- New tremors, unusual movements, or seizure activity.
- Changes in speech, vision, or swallowing.
- Severe or unusual headaches.
- Changes in level of consciousness.
- Sudden decline in normal function.
Emergency signs: Sudden facial drooping, one-sided weakness, speech difficulty, sudden severe neurological symptoms, unresponsiveness, or a prolonged seizure require immediate emergency response.
Study Notes
Clinical Connections
- Dementia Care: Cognitive changes may affect memory, communication, and independence.
- Neurological Observations: Changes in alertness, speech, movement, or sensation may indicate neurological illness.
- Fall Risk: Impaired balance, coordination, or sensation can increase fall risk.
- Recognizing Patient Distress: Sudden neurological symptoms may indicate an emergency.
- Vital Signs: Neurological illness may affect or accompany changes in vital signs.
- Therapeutic Communication: Adapt communication for cognitive, language, or sensory difficulties.
- Safe Patient Transfers: Weakness and impaired coordination affect mobility safety.
Questions
- What distinguishes the CNS from the PNS?
- What are the functions of the cerebrum, cerebellum, and brainstem?
- How do sensory and motor nerves differ?
- What distinguishes sympathetic and parasympathetic activity?
- What roles do neurons, myelin, and neurotransmitters play?
- What is the difference between delirium and dementia?
- How does Alzheimer’s disease relate to dementia?
- What distinguishes stroke from TIA?
- How should a CNA respond to suspected spinal cord injury?
- What neurological changes require emergency response?
Sources
- CNA Module 13 — Anatomy, Physiology & Aging
- MedlinePlus — Brain and Nerves
- National Institute on Aging — Brain Health
- CDC — Stroke Signs and Symptoms
- National Institute of Neurological Disorders and Stroke
Flashcards
What are the two major divisions of the nervous system?01-foundations / anatomy-physiology / nervous
Answer
Central nervous system (CNS) and peripheral nervous system (PNS).
What structures make up the CNS?01-foundations / anatomy-physiology / nervous
Answer
Brain and spinal cord.
What is the primary function of the cerebrum?01-foundations / anatomy-physiology / nervous
Answer
Conscious thought, memory, sensory interpretation, and voluntary movement.
What is the primary function of the cerebellum?01-foundations / anatomy-physiology / nervous
Answer
Coordination, balance, posture, and motor learning.
What essential functions does the brainstem regulate?01-foundations / anatomy-physiology / nervous
Answer
Breathing, heart rate, consciousness, and other involuntary functions.
What is the difference between sensory and motor nerves?02-mechanisms / anatomy-physiology / nervous
Answer
Sensory nerves carry signals toward the CNS; motor nerves carry commands away.
How do sympathetic and parasympathetic activity differ?02-mechanisms / anatomy-physiology / nervous
Answer
Sympathetic supports fight-or-flight; parasympathetic supports rest-and-digest.
What is the function of the myelin sheath?01-foundations / anatomy-physiology / nervous
Answer
Insulates axons and speeds nerve impulse transmission.
What are neurotransmitters?01-foundations / anatomy-physiology / nervous
Answer
Chemical messengers that transmit signals between cells.
What is a reflex?01-foundations / anatomy-physiology / nervous
Answer
A rapid, often automatic response to a stimulus.
How does aging commonly affect the nervous system?02-mechanisms / anatomy-physiology / nervous
Answer
Reaction times may slow, and some sensory and balance functions may decline.
How does delirium differ from dementia?02-mechanisms / anatomy-physiology / nervous
Answer
Delirium develops acutely and often fluctuates; dementia usually develops gradually.
How does Alzheimer's disease relate to dementia?02-mechanisms / anatomy-physiology / nervous
Answer
Alzheimer's disease is the most common cause of dementia.
What is the difference between stroke and TIA?02-mechanisms / anatomy-physiology / nervous
Answer
Stroke causes brain infarction or hemorrhage; TIA causes transient ischemic symptoms without acute infarction.
What does FAST stand for in stroke recognition?01-foundations / anatomy-physiology / nervous
Answer
Face drooping, Arm weakness, Speech difficulty, Time to call emergency services.
What is Parkinson's disease associated with?02-mechanisms / anatomy-physiology / nervous
Answer
Loss of dopamine-producing neurons and movement difficulties.
What is peripheral neuropathy?01-foundations / anatomy-physiology / nervous
Answer
Damage to peripheral nerves causing sensory changes, pain, or weakness.
What should a CNA do during a seizure?03-application / anatomy-physiology / nervous
Answer
Protect from injury, time the event, summon help, and never restrain or place objects in the mouth.
What is the difference between a spinal cord injury and a traumatic brain injury?02-mechanisms / anatomy-physiology / nervous
Answer
SCI damages spinal nerve pathways; TBI damages the brain.
What should a CNA do if an acute spinal injury is suspected?03-application / anatomy-physiology / nervous
Answer
Summon emergency help and avoid unnecessary movement unless required for immediate safety.