Introduction to Human Physiology

• Studies the physical and chemical mechanisms responsible for the origin, development, and progression of life.

Fields of Physiology

• Viral
• Plant
• Invertebrate
• Vertebrate
• Mammalian

Human Physiology

• Aims to explain the specific characteristics and mechanisms of the human body that make it a living being.
• Complex control systems make being alive possible.
• Hunger, fear, and cold sensations drive survival behaviors like seeking food, refuge, and warmth.
• Other forces lead humans to seek fellowship and reproduce..

Cells as Living Units

• The basic unit of the body is the cell.
• Organs comprise numerous cells held via intercellular structures.
• Each cell type specializes in performing specific functions.
• Red blood cells transport oxygen.
• Cells may differ, but share basic characteristics.
• For example oxygen reacts with carbs, fat, and protein to release energy for cell function.
• Reproduction through cell division allows for cell replenishment.
• Cells of a particular type are destroyed but regenerated until supply is replenished.

Extracellular Fluid

• 60% of the human body is fluid.
• It consists mainly of water and ions.
• Intracellular fluid resides inside cells, while extracellular fluid exists outside.
• The extracellular fluid is in constant motion.
• It transports through the circulating blood.
• It mixes via diffusion through capillary walls into tissue fluids
• It is called the internal environment of the body.
• The body is “milieu interieur”
• Cells need extracellular fluid.
• The fluid contains ions and nutrients to sustain cell life.
• Cells can live, grow, and function with oxygen, glucose, ions, amino acids, and fatty substances.

Extracellular vs Intracellular Fluids

• Extracellular fluids contain large amounts of sodium, chloride, and bicarbonate ions.
• They also contain nutrients like glucose, oxygen, fatty acids, and amino acids, as well as carbon dioxide and cellular waste.
• Intracellular fluids contain large amounts of potassium, magnesium, and phosphate ions.
• Special mechanisms transport ions through cell membranes.
• This maintains ion concetration differences between extracellular and intracellular fluids.

Homeostasis

• Maintenance of nearly constant conditions in the internal environment.
• Organs and tissues work to maintain constant conditions.
• Lungs provide oxygen, and kidneys maintain constant ion concentration.
• The GI tract provides nutrients.

Blood Circulatory System

• Blood circulates through the body at 2 stages.
• Blood moves through blood vessels.
• Fluid moves between capillaries and intercellular space.
• All blood traverses the circulatory circuit about once per minute at rest, and up to six times per minute during intense activity.
• As blood passes through capillaries, continual exchange occurs between plasma and interstitial fluid.
• Capillary walls are permeable to most plasma molecules, except large plasma proteins.
• Fluid diffuses back and forth via kinetic motion of molecules in both interstitial fluid and plasma.

Respiratory System

• The blood picks up oxygen in the alveoli.
• This process of gas exchange allows the acquisition of oxygen needed by cells.

Gastrointestinal Tract

• The body’s dissolved nutrients are in carbohydrates, fatty acids, and amino acids.
• Nutrients from food are absorbed into the blood’s extracellular fluid.

Liver and Metabolic Functions

• The Liver changes a substance's chemical composition making them usable.
• Fat cells, gastrointestinal mucosa, kidney, and endocrine glands help store these used substances or until they are needed.

Musculoskeletal System

• The body can move with the help of musculoskeletal systems to obtain required food.
• This system provides motility for protection against adverse surroundings instantly.

Metabolic Waste Removal

• Carbon dioxide is removed by the lungs and released from the blood into the lung alveoli.
• Carbon dioxide is the most abundant product of metabolism.
• The kidney removes most substances besides carbon dioxide from plasma including products of cellular metabolism.
• Urea, uric acid, excess of ions and water might accumulate in the extracellular fluid.

Nervous System

• The nervous system regulates body function.
• Its three major parts are sensory input, central nervous system, and motor output.
• Sensory input: Detects the state of the body or that of the surroundings apprising it of an object touching the skin at any point
• Central Nervous System: Composed of Brain and spinal cord. The brain receives external signals and processes them
• Motor Output: Signals transmitted through the motor output portion of the nervous system to carry out one's desires

Hormonal System

• Regulation also occurs though a hormonal System.
• The body has eight major endocrine glands.
• They secrete chemical substance called “Hormones” which regulate cellular function.
• Hormones are transported in the extracellular fluid to all part of the body.
• This also leads to metabolic function.

Control Systems of the Body

• The human body contains thousands of control systems.
• The genetic control system operates in all cells controlling intracellular function and extracellular function. Many control systems operate within organs to control function.
• Other systems operate throughout the entire body to control the interrelations between organs.
• Oxygen regulation mainly depends on the chemical characteristic of hemoglobin.
• Carbon dioxide has a different regulation style.
• Baroreceptors are rapidly acting control mechanism located in the Bifurcation region of the neck's carotid arteries and the aorta's arch.
• An increased arterial pressure stretches arterial wall will trigger a baroreceptor to send a signal to medulla brain, the message inhibits the vasomotor center decreasing arterial pressure.

Normal Ranges

• Oxygen 40 mm HG
• Carbon Dioxide 40 mm HG
• Sodium ion 142 mmol/L
• Potassium ion 4.2 mmol/L
• Calcium ion 1.2 mmol/L
• Chloride ion 108 mmol/L
• Bicarbonate ion 28 mmol/L
• Glucose 85 mg/dL
• Body Temp 98.4 (*F)
• Acid-Base 7.4 PH

Negative Feedback

• Controls the nature of most control systems.
• The negative feedback leads to pulmonary concentration.
• Carbon dioxide initiates events that decrease concentration towards normal.
• Negative feedback consists of changes that return excessive or deficient stimuli to the stimulus back to equal.

Positive Feedback

• Can sometimes cause vicious cycles or cycles of death.
• Is does no;t lead to stability leading to death.
• Bleeding suddenly can lead to lack of efficient pumping of vessels.
• Results can be weakness or death.
• Positive Feedback can lead to more stimuli.

Adaptive Control

• Some movements occur quickly.
• Not enough time to travel from the body all the way back to the brain.
• The brain uses principle “feed forward “ to cause movement.
• Adaptive control uses the brain to send sensory nerve signals from moving correct wrong movement.
• All the parts help appraise that movement is done correctly.
• If movement still needs correction, the movement for necessary to have correction.
• Adaptive control in delayed negative feedback.

Explore the fundamental principles of human physiology, focusing on the physical and chemical mechanisms that govern life processes. This includes an overview of cells as living units, their specialized functions, and how they contribute to the overall functioning of the human body. Understand the complex control systems that enable survival and reproduction.