Human Physiology: CNS Protection and Function

Central Nervous System Protection

• The meninges are protective layers around the brain and spinal cord (CNS)
• Pia mater: inner layer, thin, tightly bound to CNS, contains blood vessels supplying brain tissue and CSF
• Arachnoid mater: middle layer, web-like, suspends the brain, acts as a shock absorber
• Subarachnoid space: filled with cerebrospinal fluid (CSF), cushions the brain and spine
• Subdural space: thin layer of serous fluid above the arachnoid mater
• Dura mater: tough outer layer, contains drainage system for blood to leave the brain
• Bone (vertebrae and cranium) provide further protection

Surfactant Function

• Surfactant lines the alveoli in the lungs
• Produced by alveolar type 2 cells
• Composed of lipids and proteins
• Crucial for efficient gas exchange and maintaining alveoli structure
• Acts as lubricant to reduce surface tension at the air/liquid interface, preventing alveoli collapse during ventilation

Cellular Respiration

• Series of chemical reactions breaking down glucose to produce ATP (energy currency)
• Majority of the reactions occur in the mitochondria
• Four stages:
  • Glycolysis (in cytoplasm): breaks down glucose to 2 pyruvate molecules
  • Preparatory Reaction (in mitochondria): converts pyruvate to Acetyl CoA
  • Citric Acid Cycle (in mitochondria): oxidizes carbons from glucose molecule
  • Electron Transport Chain (in mitochondria): produces most ATP, releases and captures energy
• ATP (adenosine triphosphate) is formed and releases a phosphate to become ADP. ADP finds and binds another phosphate to become ATP again
• One glucose molecule can produce up to 38 ATP (aerobic respiration)
• Aerobic respiration requires oxygen, more efficient
• Anaerobic respiration does not require oxygen, less efficient

Blood Flow Through the Heart

• Enters via superior/inferior vena cava
• Flows to right atrium
• Through tricuspid valve
• To right ventricle
• Through pulmonary valve (semilunar)
• To pulmonary trunk/pulmonary arteries to lungs
• Oxygenated blood returns via pulmonary veins
• To left atrium
• Through bicuspid valve (mitral)
• To left ventricle
• Through aortic valve (semilunar)
• Enters aortic arch, systemic circuit

Kidney Function and Disease

• Kidneys filter waste, balance fluids, and reabsorb vitamins/amino acids/glucose
• Synthesize hormones for red blood cell production
• Regulate blood pressure (BP)
• Kidney disorders:
  • Kidney stones: mineral crystallization
  • Urinary tract infection (UTI): bacterial infection
  • Chronic kidney disease (CKD): high BP damages blood vessels
  • Diabetic nephropathy: high glucose damages kidney function

Muscle Tissue Types

• Skeletal: voluntary, attaches to bones for body movement, long and fiber-like
• Cardiac: involuntary, heart walls, striated, single nucleus per cell, interlocked for efficient contraction, automaticity
• Smooth: involuntary, organ walls, blood vessels, respiratory tract, aids in transport, vasodilation/vasoconstriction, regulates airflow

Homeostasis

• Stable internal environment maintained by internal systems
• Homeostatic regulation: receptor, control center (medulla oblongata), and effector (cell/organ)
• Receptor senses change and sends info to control center
• Control center directs effector
• Effector counteracts or reinforces the stimulus (negative or positive feedback)
• Examples: thermoregulation (negative), blood clotting/childbirth (positive)

Gas Exchange

• Breathing initiates gas exchange
• Inhalation: diaphragm and intercostal muscles contract, expanding chest cavity and creating negative pressure, air enters
• Air is filtered, moistened, warmed in upper airway and enters lower airway (trachea, bronchi, bronchioles, alveoli)
• Gas exchange occurs in alveoli (thin walls surrounded by capillaries)
• External respiration: oxygen diffuses from alveoli to blood, carbon dioxide from blood to alveoli
• Oxygenated blood travels throughout body
• Internal respiration: oxygen offloaded to tissues, carbon dioxide re-enters blood

Blood Pressure Regulation

• Three main factors: peripheral resistance (blood vessel diameter), cardiac output (heart rate x stroke volume), fluid volume
• Baroreceptors monitor blood vessel pressure
• Homeostasis: brain signals heart/blood vessels to adjust blood pressure
• High BP: parasympathetic response (lower HR, vasodilation)
• Low BP: sympathetic response (increased HR, vasoconstriction)

Kidney Fluid and Blood Pressure Maintenance

• Kidneys regulate sodium and water balance, maintaining extracellular fluid volume (ECFV)
• Increased sodium/water intake increases ECFV, therefore, blood volume
• Low BP: kidneys retain fluid
• High BP: kidneys remove fluid, decreasing blood volume

Sympathetic vs. Parasympathetic Nervous System

• Sympathetic: "fight or flight," releases epinephrine/norepinephrine,
  • increases HR, BP, RR, sweating, dry mouth, dilates airways/pupils, blood flow throughout body, decreases digestion, urine production
• Parasympathetic: "rest and digest," releases acetylcholine, restores homeostasis, brings body back to normal, increases digestion, reduces HR, BP, RR, constricts airways/pupils, stimulates saliva

This quiz covers essential topics in human physiology, focusing on the protective layers of the central nervous system, the role of surfactant in the lungs, and the process of cellular respiration. Test your knowledge on the structure, function, and importance of these systems in maintaining human health.