Introduction to Human Physiology

Introduction to Human Physiology

• Sara Yahea and Deyaa Wael present the lecture
• Paper explanations are available exclusively from the Medical Imaging Society, phone number 0795357006
• To follow the visual explanation, scan the code above

Course Overview

• The videos include recaps and past years' questions
• Recaps include:
  • Doctor's slides and explanation
  • Personal notes
  • Textbook
  • Expected questions

Physiology Defined

• Physiology studies how organs and systems function within living organisms
• Physiology studies how these systems interact to maintain internal bodily balance (homeostasis)

Body Functions

• Organs work continuously and simultaneously
• An example of organ synchronization involves eye light conversion into electrical signals
• The heart pumps blood, and the kidneys handle water and waste
• Digestion, respiration, and brain functions all contribute to bodily harmony

Energy Requirements

• Organs constantly work, thus the body needs energy even at rest – about two calories per minute

Physiology vs. Anatomy

• Physiology studies organ functions and how systems operate
• Anatomy studies the structure and location of organs to understand their physiology

Structure-Function Relationship

• Knowing an organ's structure is essential to understanding its function
• Physiological mechanisms operate through structural design
• Organ structure facilitates its function via design

Examples of Structure-Function

• The heart pumps blood via contracting/relaxing muscle walls and contains chambers for blood
• The rib cage (sternum, ribs, and vertebral column) protects vital organs and major vessels
• Intercostal muscles aid breathing by expanding/contracting the chest

Levels of Organization

• Atomic level (oxygen, hydrogen, carbon, nitrogen...)
• Molecules (water, HCl, carbohydrates, fats, proteins, DNA)
• Non-living structures
• Cells are the first living structure in the body
• Tissues: Multiple cells performing the same function
• Organs: Multiple tissues in one area
• Systems: Multiple organs create a system (e.g., cardiovascular)
• Structural cardiovascular system: Heart + blood vessel
• Functional/Physiological circulatory system: Heart + blood vessel, circulates blood
• Human body: Multiple systems

The Cell

• The cell is the smallest structural and functional unit
• Unicellular organisms (e.g., amoeba) are single-celled, performing all life functions
• Multicellular organisms have multiple cells
• Sponges are multicellular organisms with basic cells
• Humans are multicellular organisms with different, specialized cells

Tissues Defined

• A tissue is a group of cells with a specific function

Types of Tissues

• Epithelial: Covers surfaces and lines cavities, digestive system, forms glands
• Connective: Supports and connects tissues/organs
• Muscle: Responsible for movement
• Nervous: Transmits signals

Epithelial Tissue Forms

• Sheets: Found in skin and digestive system lining, important for absorption and transport
• Glands: Secrete substances (e.g., pancreas enzymes, sweat glands)

Connective Tissue

• Connects two parts/structures together
• Composed of few cells and abundant extracellular material
• Supports/anchors body parts

Types of Connective Tissue

• Loose Connective: Under the skin
• Adipose: Stores fat
• Blood: Connects structures via circulation

More Connective Tissue Types

• Fibrous Connective: Forms ligaments (connections between bones)
• Cartilage: Provides support and flexibility
• Bone: Provides structure and support

Muscle Tissue Types

• Cardiac: Found in the heart
• Skeletal: Attached to bones
• Smooth: Found in hollow organs

Nervous Tissue

• Generates and transmits electrical signals for communication

Organs

• An organ, like the stomach, consists of the four tissue types
• Epithelial tissue lines the inside surface of the stomach
• Smooth muscle comprises the stomach wall
• Nerve tissue controls muscle contraction
• Connective tissue binds these tissues together

Body Systems

• The body has 11 systems, which are groups of related organs

Internal and External Environments

• Must have systems to facilitate between internal and external environments

Systems Responsible for Communication

• Respiratory
• Digestive (an open tube from mouth to anus)
• Urinary

Environment Note

• These systems can be infected via direct contact with the external environment

More Environment Note

• Cells in the internal environment don't directly receive oxygen/nutrients from the outside
• Oxygen/nutrients need transport through a watery medium inside the internal environment

Body Water

• The adult body consists of 60% water
• 2/3 of this water is intracellular fluid (inside cells)
• 1/3 is extracellular fluid (outside cells)

Water Breakdown

• Interstitial fluid (surrounding cells)
• Plasma (fluid component of blood)
• Transcellular fluid (fluid in certain body parts)

Internal Environment

• Internal environment is the body's inside, which excludes the fluid inside cells
• Extracellular fluid surrounds the cells
• This includes plasma in the blood vs interstitial fluid between cells
• Extracellular fluid (ECF) constitutes the internal environment

Homeostasis

• Maintains optimal internal environment for working cells
• Maintaining a relatively stable internal environment within the body
• Homeo= the same, stasis= stay
• It needs to keeps the relatively stable values fluctuating within normal ranges
• Examples temperature, blood volume, blood PH, etc
• Dynamic steady state: the internal environment remains stable, but isn't static where values flux within ranges

Body Systems and Homeostasis

• Circulatory: Transports materials (nutrients, gases)
• Digestive: Breaks food into nutrients
• Respiratory: Delivers oxygen and removes carbon dioxide
• Urinary: Removes waste from plasma
• Skeletal: Offers support/protection
• Muscular: Moves bones
• Integumentary: Is a protective barrier
• Immune: Defends against invaders
• Nervous: Rapidly controls/coordinates
• Endocrine: Regulates activities of duration
• Reproductive: Perpetuation of species

Homeostasis Contribution

• All systems help maintain homeostasis, except the reproductive
• The reproductive system's primary function is reproduction, not homeostasis

Internal Environment Maintenance

• It is important to maintain the internal environment within normal limits
• Such as PH level, Glucose level and body temperature, etc
• Examples: sodium, potassium, calcium...

Fluid Compartments Exam

• Fluid Compartments
  • 60% of body weight
• Extracellular fluid (ECF)
  • 1/3 body weight
  • 20% body weight
• Intracellular fluid (ICF)
  • 2/3 body weight
  • 40% body weight

Other Fluids

• Plasma (25% of ECF, 5% BW)
• Interstitial fluid (75% of ECF, 15% BW)
• Transcellular fluid

Transcellular Fluid Types

• Cerebrospinal Fluid (CSF): Surrounds the brain/spinal cord
• Intraocular Fluid: Inside the eye
• Pleural Fluid: Surrounds the lungs
• Peritoneal Fluid: Located around abdominal organs
• Pericardial Fluid: Surrounds the heart
• Synovial Fluid: Found in joints
• Digestive Secretions: Fluids in digestion

Homeostasis Disruption and Response

• Disturbance is detected by a control center that follows disruption
• Control center processes the change, an proper response is implemented to restore balance

Types of Homeostasis Control

• Intrinsic (within the organ)
• Extrinsic (from outside the organ)

Intrinsic Control

• The organ regulates without external influence
• Example: Skeletal muscles increase blood supply by vessel dilation for more oxygen during exercise

Extrinsic Control

• Two systems regulate body functions from outside the organ
• Endocrine: Uses hormones
• Nervous: Uses electrical signals

Homeostatic Control Systems

• Feed-forward
• Feedback
• Response is initiated before any change is detected
• Responds after detecting change

Feedback Control

• Responds after detecting a change, with two types
  • Negative: Reduces or minimizes change
  • Positive: Enhances initial change

Important Notes

• Negative feedback loop maintains homeostasis, positive feedback disturbs homeostasis

Examples of Negative Feedback

Exposure to cold decreases body temperature > brain detects and signals muscles > shivering (repetitive
muscle contraction) generates heat and reduces heat loss by limiting body’s surface, maintaining blood
temperature.

In hot weather, increased body temperature is detected > brain stimulates sweating and also dilates superficial blood vessels, allowing blood to release excess heat and cool the body.

Even More Feed Back

Glucose Consumption > eating chocolate increases blood sugar, pancreas releases insulin facilitating its uptake into cells, restoring glucose levels, then insulin release process is discontinued.

Positive Feedback Defined

• In positive feedback, the response amplifies the initial change in the same direction
• It continues until a significant change occurs
• It typically disturbs homeostasis
• Commonly seen in specific situations like childbirth

Examples of Positive Feedback

Childbirth Press: Fetus against uterine walls, which stimulate oxytocin which in turn, enhance contractions increase pressure and stretching until baby is birthed. Oxytocin can be synthesized to induce labor in hospitals if needed.

• Positive Feedback in Blood Clotting: Following an injury, platelets attract chemicals. This cycle repeats, accumulating enough platelets which form a blood clot allowing for healing.