Neuroscience Lecture Notes

Neuro Lecture Notes

• Nervous tissue is composed of two cell types: neurons and neuroglial cells
• Neurons are the fundamental unit of the nervous system, exhibiting excitability and conducting impulses
• Afferent neurons are sensory neurons that transmit information to the central nervous system (CNS)
• Efferent neurons are motor neurons that transmit information away from the CNS
• Gray matter is primarily made up of neuronal cell bodies
• Neuroglial cells form the scaffolding, provide protection, support, and glycogen storage
• Astrocytes form the blood-brain barrier (BBB)
• Oligodendrocytes and Schwann cells produce myelin, increasing nerve impulse velocity

Metabolic Requirements of Nervous Tissue

• The brain receives 15-20% of the total resting cardiac output (CO) and consumes 20% of its oxygen
• The brain has no way to store oxygen, making it vulnerable to hypoxia
• Clinical signs of hypoxia include altered mental status (AMS), confusion, restlessness, and loss of consciousness
• Cell death begins within 4-6 minutes of oxygen deprivation

Gate Control Theory of Pain

• Pain perception is modulated by a gate mechanism in the spinal cord
• Ascending and descending pathways influence pain signals
• Cognitive and emotional factors also modify the perception and intensity of pain
• Large-diameter A-beta fibers (non-nociceptive input like touch) are faster and activate interneurons in the dorsal horn to minimize pain sensation
• Rubbing, massage, vibration, and transcutaneous electrical nerve stimulation (TENS) are believed to close the gate.

Neuropathic Pain, Neuralgias, and Phantom Limb Pain

• Neuropathic pain is a broad category of nerve-related pain caused by direct nerve damage
• Neuralgia is a type of nerve-related pain characterized by brief, severe attacks of pain
• Phantom limb pain results from a discrepancy between the brain's body map and sensory input
• The brain continues to send signals to the location of the missing limb, resulting in the experience of pain

Skeletal Muscle Disorders

• Muscular dystrophy are genetic conditions that lead to progressive deterioration of skeletal muscle fibers
• Duchenne muscular dystrophy (DMD) is the most common type, characterized by progressive muscle weakness, necrosis, atrophy, and fat and connective tissue replacement.
• Clinical manifestations include elevated muscle size & weakness.

Disorders of the Neuromuscular Junction (NMJ)

• Myasthenia gravis is an autoimmune disease that targets acetylcholine receptors at the NMJ leading to impaired signal transmission
• Clinical manifestations include droopy eyelids, double vision, difficulty with chewing and swallowing, fatigue, and progressive muscle weakness

Peripheral Nerve Disorders

• Guillain-Barre syndrome is an acute autoimmune attack on the myelin sheath, resulting in lower motor neuron disorder.
• Clinical manifestations include ascending, symmetric flaccid paralysis, paresthesia, and numbness.

Disorders of the Basal Ganglia

• Parkinson's disease is a degenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra.
• Clinical manifestations include tremors at rest, rigidity, bradykinesia, postural instability, and difficulty initiating movements.

Stroke

• Ischemic stroke is caused by a blockage in a blood vessel, preventing oxygen delivery to brain tissues.
• Hemorrhagic stroke is caused by a ruptured blood vessel within the brain, leading to blood leakage.
• Clinical presentations include confusion, headache, slurred speech, loss of movement, etc.

Subarachnoid Hemorrhage and Cerebral Aneurysm

• Subarachnoid hemorrhage is a rupture of a cerebral aneurysm
• Risk factors for both conditions include trauma and/or genetic predisposition
• Clinical presentation features a violent headache and rapid loss of consciousness, potentially leading to death

Seizures

• Seizures are abnormal, excessive electrical activity in the brain
• Generalized seizures affect the entire brain, whereas focal or partial seizures are localized
• Clinical presentation varies depending on the type of seizure.

Burn Injuries

• Thermal burns are caused by heat, chemical burns by corrosive agents, and electrical burns by electricity
• The severity of burns is categorized by depth – superficial, partial thickness and full thickness
• Complications of burn injuries include local inflammatory response and systemic effects.

Cardiovascular Complications of Burn Injuries

• Hypovolemia, shock, changes in blood pressure, heart rate, and cardiac output, are common consequences of significant burn injuries
• Systemic inflammation, and infection are associated with severe disruptions to circulatory, immune, and metabolic functions.
• Acute, severe burns increase metabolic requirements requiring high-calorie and protein nutrition support

Musculoskeletal Injuries

• Fractures are breaks in bone continuity, caused by direct blows, impacts, or extreme forces
• Dislocations occur when a bone is moved out of its proper position at a joint
• Strains are partial or complete tears in ligaments, connecting tendons, and muscles
• Clinical manifestations include pain, swelling, bruising, impaired movement, and deformity.

Venous Thromboembolism (VTE) & Fat Embolism Secondary to Trauma

• Compartment syndrome occurs when swelling in a closed muscle compartment builds up excessive pressure that compromises blood flow.
• VTEs are blood clots forming in the deep veins; risk factors for VTEs include immobilization venous stasis and hypercoagulability.
• Fat embolism syndrome develops when fat globules or fat droplets enter the bloodstream and obstruct small blood vessels, disrupting oxygen delivery.

Osteomalacia

• Osteomalacia is a softening of the bones caused by inadequate mineralization.
• Causes include vitamin D deficiency, calcium deficiency, or certain medications
• Clinical manifestations include bone pain, muscle weakness, and fractures.

Diabetes Mellitus

• Two primary types of diabetes are Type I (insulin-dependent) and Type II (non-insulin-dependent).
• Type I is an autoimmune disease where the immune system attacks the insulin-producing cells in the pancreas.
• Type II is characterized by insulin resistance, where the body's cells do not respond properly to insulin.

Acute Complications of Diabetes Mellitus

• Hypoglycemia is a decreased level of blood glucose
• Acute complications result from an inability to maintain metabolic equilibrium.

Chronic Complications of Diabetes Mellitus

• Chronic complications of diabetes are long-term consequences resulting from damage to blood vessels and nerves.
• Chronic complications can include retinopathy, nephropathy, and neuropathy

Renal and Genitourinary Disorders

• Urolithiasis or kidney stones involve the crystallization of minerals and salts in the urine, causing obstruction.
• Urinary tract infections (UTIs) are infections of the urinary system. Common risk factors include sexual activity, anatomical factors, catheters, etc.
• Glomerulonephritis is an inflammation of the glomeruli in the kidneys. Risk factors may include streptococcal bacterial infections

Acute Kidney Injury (AKI)

• AKI is a sudden decrease in kidney function, characterized by diminished glomerular filtration rate.
• AKI can be caused by a variety of factors, including reduced blood flow to the kidneys, kidney damage and obstruction distal to the kidneys

Chronic Kidney Disease (CKD)

• CKD is a progressive decline in kidney function lasting three months or longer, characterized by a diminished glomerular filtration rate.
• CKD can result from a number of long-term health conditions or a single episode of severe trauma or illness
• Clinical presentation often involves a gradual worsening of symptoms.

Explore the basics of nervous tissue and its components in this quiz. Understand the roles of neurons, neuroglial cells, and the metabolic requirements crucial for brain function. Test your knowledge on how the brain functions and the consequences of hypoxia.