Human Body Systems: Circulatory, Excretory, and Nervous
Circulatory System
The circulatory system involves a continuous loop:
Left auricle → bicuspid valve → left ventricle → aorta artery → vena cava → right auricle → tricuspid valve → right ventricle → pulmonary artery → lungs (alveoli) → pulmonary vein → left auricle.
Blood
Types of Blood Cells
- RBC (Red Blood Cells): No nucleus, contains hemoglobin.
- WBC (White Blood Cells):
- Phagocytes: Engulf bacteria and viruses (phagocytosis).
- Lymphocytes: Produce antibodies.
- Platelets: No nucleus.
Functions of Blood
- Transports oxygen from lungs to body (RBC).
- Transports CO2 from body to lungs.
- Transports nutrients from the digestive system to the body.
- Transports waste products to kidneys, bladder, etc.
- Maintains body temperature.
- Fights infection (WBC).
- Clots wounds (Platelets).
Movements of the Heart
Systole: Contraction; Diastole: Relaxation.
Types of Muscles
- Striated Muscle: Voluntary, strong contraction (e.g., biceps).
- Smooth Muscle: Involuntary, weak contraction (e.g., stomach).
- Cardiac Muscle: Involuntary, strong contraction (e.g., heart).
Excretion and Osmoregulation
Excretion: Removal of waste products of metabolism.
Osmoregulation: Regulation of the water content of the blood.
Importance of Constant Temperature
- Enzymes work best at their optimum temperature.
- Cell membranes become more fragile as temperature rises.
- Diffusion rates increase with higher temperatures and decrease with lower temperatures.
- Liquids, such as blood, become more viscous as the temperature falls.
Heat Transfer Processes
- Convection: Transfer of heat to and from the body via air currents. Can be increased by fanning.
- Radiation: Transfer of heat in the form of rays, usually infra-red.
- Conduction: Transfer of heat by direct contact with another object.
Heat Gains: Respiration, conduction, convection, radiation.
Heat Losses: Evaporation, excretion, conduction, convection, radiation.
If heat gains exceed heat losses, body temperature will rise: hyperthermia.
If heat losses exceed heat gains, body temperature will fall: hypothermia.
Structure of the Skin
Epidermis, hair, hair erector muscle, nerve ending, sebaceous gland, subcutaneous tissue, capillary beds, sensory neuron, dermis, sweat gland, malpighian layer.
Kidneys
Functions of Kidneys
- Detoxify blood.
- Increase calcium absorption.
- Stimulate RBC production.
- Regulate blood pressure and electrolyte balance.
Potential Problems
- Kidney failure (diabetes, high blood pressure).
- Kidney stones (many causes, including genetic disorder; too much calcium absorbed).
Treatment
Dialysis replaces the work your kidneys do. There are two types: hemodialysis and peritoneal dialysis.
Endocrine and Nervous Systems
Comparison
Nervous System: Very rapid, electrical impulses, usually completed within seconds, often confined to one area of the body, reflexes such as blinking.
Endocrine System: Can be slow, chemical messenger, may take years before completed, usually noticed in many organs, growth or reproductive system.
Nervous System
Stimuli (exterior or interior) → receptor (external: skin, eye, ear; internal: blood vessels, pain receptor) → sensorial nerve → brain → motor nerve → effectors → muscle, other neuron, glands.
Central Nervous System
Encephalon (Brain)
Protection:
Skull (cranium)
3 membranes (meninges: pia mater, dura mater, arachnoid)
Cerebrospinal fluid
Parts: Brain, cerebellum, spinal bulb, hypothalamus, hypophysis, thalamus, limbic system.
Spinal Cord
Protection:
Backbone (33 vertebrae)
Peripheral Nervous System
Sensorial and motor nerves
12 cranial nerves (originate from the brain)
31 spinal nerves (originate from the spinal cord)
Cells of the Nervous System
Neuron
Specialized in transmitting the nervous impulse (electrical current).
Neurons are not physically touching.
Santiago Ramón y Cajal (1906) developed stain techniques for neurons.
Glia Cells
Function is to feed and protect the neurons.
Neuron Structure
Cell body, dendrites, axon, nodes of Ranvier, fatty sheath made of myelin, end plate.