Human Physiology
Introduction
The study of Physiology in humans is the pillar of the study of functioning and homeostasis in the human body. It looks into the interaction of organ systems in order to maintain life through coordinated processes. This systematic presentation is a summary of the major systems to study in detail.
Introduction to Physiology
Physiology is a branch of the natural sciences that studies normal processes of living (cellular, tissue and organ). It is a combination of anatomy and mechanisms such as circulation, respiration, and neural signaling. Homeostasis is a balancing mechanism that promotes internal stability through the feedback process, e.g. temperature regulation by means of sweating or shivering.
Circulatory System
- It is a muscular pump, called the heart, that pumps the blood through arteries, veins, and capillaries. Sinoatrial node controls cardiac cycle that consists of systole (contraction) and diastole (relaxation). Oxygen, nutrients, hormones and wastes are transported through the blood; plasma used is 55% of the blood volume; red blood cells contain the hemoglobin needed to bind oxygen.
- Blood Composition
- Red blood cells (erythrocytes): Biconcave discs for gas exchange.
- White blood cells (leukocytes): Fight infections via phagocytosis.
- Platelets: Essential for clotting cascade initiated by thrombin.
- Lymphatic system returns interstitial fluid, aiding immunity.
Respiratory System
- Gas exchange: CO 2 is exchanged through the lungs and O2 is inhaled. The contraction of the diaphragm leaves thoracic cavity expansive which forms negative pressure to kill air. Alveoli are encircled by capillaries that facilitate diffusion, and surfactant helps them not to collapse.
- Breathing Mechanics
- Inspiration: Intercostal actively involved.
- Expiration: Repose in rest, active exercise.
- The rate of breathing is regulated through chemoreceptors that measure the pO2 and pCO2 concentrations.
Digestive System
Food is processed by mouth, stomach, small intestine and large intestine. Amylase in the saliva begins the process of breaking down starch; proteins are broken down by gastric HCl and pepsin. Nutrients are absorbed through the small intestine through the use of villus; enzymes such as lipase are secreted through pancreas to break down fats.
Nutrient Absorption
Food is propelled by peristalsis; bile is emulsified by liver. Secretions are under the control of hormones such as gastrin and secretins. Colon microbiome ferments fiber, to form vitamins.
Excretory System
- The kidneys strain 180 liters of blood per day and this urine is created. A glomerulus has nephrons that are used in ultrafiltration and tubules used in reabsorption. ADH causes urine concentration; aldosterone causes the conservation of NA+.
- Urine Formation
- Glomerular filtration: Water, ions, wastes pass.
- Tubular reabsorption: Glucose, amino acids reclaimed.
- Secretion: H+, K+ added for pH balance.
Nervous System
- Neurons pass the impulses through action potentials; synapses secrete neurotransmitters such as acetylcholine. Processes info in central nervous system (brain, spinal cord) and peripheral (somatic or voluntary) and autonomic (involuntary).
- Brain Divisions
- Cerebrum: Higher functions like memory, reasoning.
- Cerebellum: Coordination, balance.
- Brainstem: Vital centers for heart rate, breathing.
Endocrine System
- Hormones are regulated by being released in blood by glands. Thyroid (metabolism through T3/T4), adrenals (cortisol stress), pancreas (insulin/glucagon glucose), are under the control of pituitary master gland.
- Key Hormones
- Hypothalamus: Releases CRH, TRH.
- Gonads: Estrogen, testosterone for reproduction.
- Feedback inhibits overproduction, e.g., high blood sugar triggers insulin.
Reproductive System
- Male: sperm is produced in testes, testosterone. Female: Cyles Ovaries secrete ova, progesterone/estrogen. Menstrual cycle (28days) consists of follicular phase, ovulation cue, luteal phase.
Muscular and Skeletal Systems
- Muscles of the skeletal system contract by the actin-myosin sliding; cross-bridges are powered by ATP. The bones are structural and the joints are movable. Imbalance in Ca2+ leads to osteoporosis.
- Integration will guarantee survival: e.g., exercise increases circulation and respiration. System interdependence is emphasized by such disorders as diabetes (insulin deficiency).
.png)
