Nervous System Anatomy and Function

Nervous System Anatomy and Function

• The nervous system is the body's control center, coordinating activities by transmitting signals.
• It's divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS consists of the brain and spinal cord.
• The PNS connects the CNS to the rest of the body.
• The PNS further divides into the somatic nervous system, controlling voluntary movements, and the autonomic nervous system, regulating involuntary actions.

The Neuron

• The basic unit of the nervous system is the neuron.
• Neurons consist of a cell body, dendrites, and an axon.
• Dendrites receive signals and transmit them to the cell body.
• Axons carry signals away from the cell body.
• Myelin, a fatty substance, covers some axons, speeding signal transmission.
• Myelinated axons form white matter, while unmyelinated axons make up gray matter.
• Neurons are categorized as sensory neurons, carrying signals to the CNS, and motor neurons, transmitting signals from the CNS.
• Synapses are junctions where neurons connect, transmitting signals using neurotransmitters.

Nervous System Components

• Nerves are bundles of neuron fibers found in the PNS.
• Ganglia are collections of neuron cell bodies along nerve pathways.
• Some nerves carry only sensory or motor signals, but most are mixed nerves with both types.
• The brain is responsible for higher-level functions like memory and reasoning (cerebrum), sensory relay and hormone control (diencephalon), vital functions (brainstem), and coordination and balance (cerebellum).
• The spinal cord extends from the brainstem to the lower back, connecting to 31 pairs of nerves for sensory and motor control.

Terminology

• Afferent: Carries impulses towards the CNS (sensory neurons).
• Efferent: Carries impulses away from the CNS (motor neurons).
• Autonomic Nervous System: Regulates involuntary activities.
• Central Nervous System: Consists of the brain and spinal cord.
• Cerebrospinal Fluid: Watery fluid circulating within the brain and spinal cord for protection.
• Synapse: Junction between two neurons or between a neuron and a muscle or gland.
• Reflex: Automatic rapid response to a stimulus.
• Neurotransmitter: Chemical transmitting signals across a synapse (e.g., norepinephrine).

Common Root Terms

• neur/o, neur/i: Relates to nervous system, nervous tissue, or nerve.
• gli/o: Refers to neuroglia, which support and protect neurons.
• gangli/o, ganglion/o: Pertains to ganglia, collections of neuron cell bodies.
• mening/o, meninge/o: Refers to the meninges, membranes surrounding the brain and spinal cord.
• myel/o: Relates to the spinal cord (or bone marrow).
• encephal/o: Refers to the brain.
• narc/o: Relates to stupor or unconsciousness.
• -phobia: Refers to persistent, irrational fear.

Related Terms

• Amyloid: Starch-like substance found in the brain in Alzheimer's disease.
• Coma: Deep unconsciousness.
• Concussion: Injury causing brain injury, often with temporary loss of consciousness.
• Convulsion: Violent, involuntary muscle contractions.
• Dementia: Progressive loss of intellectual function.
• Encephalitis: Brain inflammation.
• Epilepsy: Chronic disorder with sudden, abnormal bursts of brain electrical activity causing seizures.
• Parkinsonism/Parkinson's Disease: Disorder characterized by slow movements, tremors, rigidity, and a mask-like facial expression.
• Paralysis: Loss of function, movement, or reflex.
• Alzheimer Disease: Dementia form caused by cerebral cortex atrophy.
• Tremor: Shaking or involuntary movement.
• Anxiety: Feeling of fear, worry, uneasiness, or dread.
• Schizophrenia: Severe mental disorder with psychosis, delusions, hallucinations, and withdrawn or bizarre behavior.
• Depression: Mental state with profound sadness, emptiness, hopelessness, and lack of interest.

Diagnostic Tools

• Electroencephalography (EEG): Records and interprets electrical activity in the brain.
• Cerebral Angiography: Radiographic study of brain blood vessels, using contrast medium.

Case Study Example

• A 52-year-old male presenting with sudden right-sided weakness, slurred speech, and difficulty understanding language, with a CT scan revealing a blockage in a brain blood vessel, is most likely experiencing a stroke.
• The central nervous system is primarily affected in this case.

Test your knowledge on the anatomy and function of the nervous system, including the central and peripheral divisions. Explore the structure of neurons, their types, and their roles in signal transmission. Challenge yourself with questions about how the nervous system coordinates body activities.