Human Body Systems Summary
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Nervous System Overview
Collects, processes, and responds to internal and external information through electrical impulses.
Major divisions: Central Nervous System (CNS: brain and spinal cord) and Peripheral Nervous System (PNS: nerves outside CNS).
Neuron types:
Sensory neurons: carry impulses to CNS.
Motor neurons: carry impulses from CNS to muscles/glands.
Interneurons: process information within CNS.
Neuron Function
Resting potential: -70 mV charge.
Action potential: sudden charge reversal when stimulus reaches threshold.
Impulse travels faster in myelinated axons.
Peripheral Nervous System
Two divisions: Sensory (receives information) and Motor (sends commands).
Somatic Nervous System: voluntary movements.
Autonomic Nervous System: involuntary control (sympathetic: fight or flight; parasympathetic: rest and digest).
Skeletal System
Functions: Supports, protects organs, assists in movement, stores minerals, and forms blood cells.
Two parts: Axial skeleton (skull, vertebral column) and Appendicular skeleton (limbs).
Joints categorized by movement flexibility: immovable, slightly movable, and freely movable.
Muscular System
Three types of muscle: Skeletal (voluntary, striated), Smooth (involuntary, non-striated), Cardiac (involuntary, striated).
Muscle contractions occur via cross-bridge cycling between actin and myosin (sliding filament model).
Integumentary System
Comprises skin, hair, nails, and glands.
Functions: Protects against infection, regulates temperature, senses environmental changes, produces vitamin D.
Skin layers: Epidermis (outer, protective) and Dermis (contains blood vessels, nerves).
Endocrine System
Regulates metabolism, mood, and growth through hormones released into the bloodstream.
Hormone types: Steroid (act directly on genes) and Nonsteroid (trigger secondary messengers).
Major glands: Hypothalamus, pituitary, thyroid, adrenal, pancreas, ovaries, testes.
Homeostasis and Feedback Mechanisms
Maintained through negative feedback loops (e.g., water balance, blood glucose regulation via insulin and glucagon).
Reproductive System
Male: Testes produce sperm; regulated by hormones (LH, FSH).
Female: Ovaries produce eggs; menstrual cycle involves hormonal regulation.
Fertilization leads to embryo development; key stages include gastrulation and neurulation, forming future bodily structures.
Fetal Development
Placenta formed to nourish fetus; necessary for exchanging nutrients and wastes.
Developmental trimesters: cell differentiation, organ formation, and maturation occur progressively until birth.