Nervous System

Nervous system

The system in the body responsible for sensing environmental changes and communicating with other neurons.

Neurons

Cells in the nervous system that transmit electrochemical signals and are responsible for sensing environmental changes.

Glial cells

Support cells in the nervous system that nourish and insulate neurons and remove waste products.

Cell body

Also known as the soma, it contains the nucleus and organelles of a neuron.

Dendrites

Transmit signals received from other neurons to the cell body.

Axon

Arises from the axon hillock in the cell body and initiates action potentials. It also forms synaptic connections with other neurons and contains neurotransmitters for signal transmission.

Neurotransmitters

Endogenous chemicals that allow neurons to communicate with each other throughout the body.

Astrocytes

Glial cells that provide physical and nutritional support to neurons in the central nervous system.

Ependymal Cells

Thin lining of the ventricular system of the brain and spinal cord that produces cerebrospinal fluid.

Schwann Cells (PNS)

Glial cells that insulate axons with myelin sheath and facilitate rapid transmission of action potentials in the peripheral nervous system.

Oligodendrocytes (CNS)

Glial cells responsible for insulating axons in the central nervous system by producing myelin sheath.

Myelination

Process of insulating axons with myelin, which increases the rate of action potential transmission.

Gray Matter

Area in the nervous system that contains neural cell bodies, axon terminals, dendrites, and nerve synapses.

White Matter

Bundles of axons coated with myelin that conduct nerve signals up and down the spinal cord.

Traumatic Brain Injury

Insult to the brain caused by an external physical force, resulting in altered brain function.

Open Head Injury

Skull penetration and breach of meninges, often leading to aneurysms and weakened vasculature.

Closed Head Injury

Occurs without a skull fracture, causing the brain's soft tissue to be forced into contact with the skull.

Moderate to Severe TBI

Symptoms include headaches, migraines, dizziness, seizures, chronic pain, and disruption of sleep and emotional disorders.

Mild TBI or Concussion

Loss of consciousness may be short or absent, followed by symptoms such as dizziness, difficulty with memory, headaches, and fatigue.

Peripheral Nervous System (PNS)

Nerves that branch out from the brain and spinal cord, forming the communication network between the CNS and the rest of the body.

Sensory or Afferent Fibers

Nerve fibers that bring information from the periphery to the CNS.

Motor or Efferent Fibers

Nerve fibers that subdivide into the somatic and autonomic nervous systems, controlling voluntary and involuntary movements.

Myelinated Peripheral Nerve Fibers

Axons wrapped with myelin sheath, extending from Schwann cells.

Endoneurium

Intravascular connective tissue that surrounds individual Schwann cells and provides nutritive and protective functions.

Connective Tissue

Makes up a significant portion of peripheral nerves and can affect nerve function if injured.

Compression

Stress placed on nerves due to joint motion, causing elongation or tension.

Nerve Injury Categories

Neurapraxia (local conduction block), Axonotmesis (loss of axonal continuity), Neurotmesis (loss of continuity by severance or scar).

Wallerian Degeneration

Process of axonal and myelin disintegration followed by Schwann cell proliferation and axonal sprouting after nerve injury.

Gillian-Barre Syndrome

Rapid onset muscle weakness caused by immune system damage to the peripheral nervous system.

Poliomyelitis

Infectious disease caused by the polio virus, leading to muscle weakness, paralysis, and post-polio syndrome.

Diabetic Neuropathy

Gradual loss of nerve fiber integrity due to diabetes, leading to sensory loss, foot ulcers, and neuropathic pain.

Carpal Tunnel Syndrome

A condition where the carpal tunnel narrows or the synovium surrounding the flexor tendons swells, putting pressure on the median nerve and reducing its blood supply, leading to numbness, tingling, pain, and weakness in the hand.

Risk Factors for Carpal Tunnel Syndrome

Factors that increase the chances of developing carpal tunnel syndrome, including being a woman, aging (especially after 40), obesity, diabetes, alcohol addiction, fibromyalgia, hypothyroidism, hormonal changes during pregnancy, and extra body fluid retention.

Causes of Carpal Tunnel Syndrome

Various causes of carpal tunnel syndrome, including anatomical factors, inflammation, rheumatoid arthritis, infections, tumors, cysts, previous wrist fractures or dislocations, and repetitive motions performed at home or work.

Aging Neuropathy

The thickening of perineurium and epineurium, fibrosis of the endoneurium, reduced numbers of nerve fibers, atherosclerosis of blood vessels to nerves, and loss of nerve fibers due to reduced blood supply, which contribute to peripheral neuropathy in older people.

Vascular Pathology

The prevalence of peripheral neuropathy in older people is often attributed to vascular pathology, where atherosclerosis and occlusion of blood vessels to nerves result in the loss of nerve fibers.

Factors Contributing to Aging Neuropathy

Factors such as loss of motor and sensory cell bodies, chronic compression of peripheral nerves, repetitive traumas, comorbidities (e.g., atherosclerosis, nutritional deficiencies), and a combination of these factors contribute to the development of aging neuropathy.