Session 1: Body Organization, Tissues & Homeostasis

Workshop 1 Overview

• Homeostasis

• Body organisation

• Tissues

• Integumentary system

Physiology

• Physiology focuses on the functions of the body

  • Considers the operation of specific organ systems

    • Renal physiology (kidney function)

    • Neurophysiology (nervous system function)

    • Cardiovascular physiology (heart and blood vessels function)

  • Also requires a knowledge of basic physical and chemical principles (e.g., electrical currents, pressure, and movement)

• Anatomy: the study of structure

  • Anatomy and physiology are inseparable

  • Function always reflects structure

  • What a structure can do depends on its specific form

The 7 Core Concepts of Physiology

• STRUCTURE & FUNCTION

  • Structure and function are intrinsically related at all levels of the organism.

• PHYSIOLOGICAL ADAPTATION

  • Organisms adjust and adapt to acute and chronic changes in the internal and external environments across the lifespan.

• HOMEOSTASIS

  • The internal environment of the organism is actively regulated by the responses of cells, tissues, and organs through feedback systems.

• CELL MEMBRANE

  • Cellular membranes determine which substances enter or leave the cell or its compartments.

  • They are essential for cell signalling, transport, and function.

• CELL-TO-CELL COMMUNICATION

  • The function of the organism requires that cells pass information to one another to coordinate their activities.

• MOVEMENT OF SUBSTANCES

  • The movement of substances (ions or molecules) is a fundamental process that occurs at all levels of organisation in the organism.

• INTEGRATION

  • Cells, tissues, organs, and organ systems interact to create and sustain life.

Homeostasis

• Homeo: like, similar

• Stasis: standing still or in a state of equilibrium

• Maintenance of a relatively stable internal environment despite continuous changes in the external environment

  • (internal environment = inside body)

  • (external environment = outside body)

• Homeostasis ensures that cells live in constant conditions.

• Involves continuous monitoring and regulation of many variables (e.g. Glucose, O2 & CO2, water, Na+, K+, Ca2+, fats, temperature, pressure )

• Imbalances are corrected by the Nervous and endocrine systems via nerve impulses and hormones

Feedback Loop Components

(reseptor/afferent pathway/control center/efferent pathway/effector)

• Stimulus: Produces change in variable.

• Receptor: Detects change.

• Input: Information sent along afferent pathway to control center.

• Control Center: analyzes input from the receptor, and coordinates an appropriate response

• Output: Information sent along efferent pathway to effector.

• Effector: whatever responds to stimuli

  Response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level.

Negative Feedback

• The response reduces or shuts off the original stimulus

• Example: Temperature regulation

Temperature Regulation (example)

• Stimulus: Body temperature rises

• Receptors: Temperature-sensitive cells in skin and brain

• Afferent pathway: Information sent along the afferent pathway to control center

• Control Center: Thermoregulatory center in brain

• Efferent pathway: Information sent along the efferent pathway to effectors

• Effectors: Sweat glands

• Response: Sweat glands activated, evaporation of sweat; Body temperature falls; stimulus ends

• Stimulus: Body temperature falls

• Receptors: Temperature-sensitive cells in skin and brain

• Afferent pathway: Information sent along the afferent pathway to control center

• Control Center: Thermoregulatory center in brain

• Efferent pathway: Information sent along the efferent pathway to effectors

• Effectors: Skeletal muscles

• Response: Shivering begins; Body temperature rises; stimulus ends

Positive Feedback

• The response enhances or exaggerates the original stimulus

• May exhibit a cascade or amplifying effect

• Usually controls infrequent events:

  • Platelet plug formation and blood clotting

Negative Feedback: Glucose Regulation Example

• Too much sugar (stimuli) → pancreas releases insulin (receptor)→ cells take up sugar & liver stores it (effector)→ blood sugar lowers

• Low blood glucose (stimuli) → glucagon secretion (reseptor) → liver breaks down glycogen (effector) → glucose released into bloodstream

  

Clinical Case: Homeostasis

• Susan, a 23-year-old student, went on a trip to a health spa with friends.

• Susan sat in a sauna at a temperature of 77°C for ten minutes.

• During this time, homeostatic mechanisms led to her body temperature remaining relatively constant.

Body Organisation

• Chemical level: Atoms combine to form molecules.

• Cellular level: Cells are made up of molecules.

• Tissue level: Tissues consist of similar types of cells.

• Organ level: Organs are made up of different types of tissues.

• Organ system level: Organ systems consist of different organs that work together closely.

• Organismal level: The human organism is made up of many organ systems.

Body System

• A body system is a collection of organs that performs related functions e.g. Digestive system

• Organs interact to accomplish a common activity essential for survival

• Eleven systems:

  • Circulatory (cardiovascular)

  • Digestive

  • Respiratory

  • Urinary

  • Skeletal

  • Muscular

  • Integumentary (outer cover)

  • Immune

  • Nervous

  • Endocrine

  • Reproductive

Organ Systems and Their Components

• Circulatory system: heart, blood vessels, blood

• Digestive system: mouth, pharynx, esophagus, stomach, small intestine, large intestine, salivary glands, exocrine pancreas, liver, gallbladder

• Respiratory system: nose, pharynx, larynx, trachea, bronchi, lungs

• Urinary system: kidneys, ureters, urinary bladder, urethra

• Skeletal system: bones, cartilage, joints

• Muscular system: skeletal muscles

• Integumentary system: skin, hair, nails

• Immune system: lymph nodes, thymus, bone marrow, tonsils, adenoids, spleen, appendix, and white blood cells, gut-associated lymphoid tissue, skin-associated lymphoid tissue

• Nervous system: brain, spinal cord, peripheral nerves, and special sense organs

• Endocrine system: all hormone-secreting tissues, including hypothalamus, pituitary, thyroid, adrenals, endocrine pancreas, gonads, kidneys, pineal, thymus, parathyroids, intestine, heart, skin, adipose tissue

• Reproductive system:

  • Male: testes, penis, prostate gland, seminal vesicles, bulbourethral glands, associated ducts

  • Female: ovaries, oviducts, uterus, vagina, breasts

Location of Organs: Body Cavities

• Dorsal cavity: protects the nervous system

  • Two subdivisions:

    • Cranial cavity (encases brain)

    • Vertebral cavity (encases spinal cord)

• Ventral cavity: houses the internal organs

  • Two subdivisions, separated by diaphragm

    • Thoracic cavity

    • Abdominopelvic cavity

Body Systems - Working together

• Once you consider how each body system works in isolation we must consider how they work together

Tissues

Organ

• Body structure that integrates different tissues and carries out a specific function

• Example: Stomach

  • Epithelial tissue: protection, secretion, absorption

  • Connective tissue: structural support

  • Muscle tissue: movement

  • Nervous tissue: communication, coordination, control

Epithelium

• Covers exposed surfaces (e.g. skin) & lines internal passageways (e.g. GIT)

• Protects the body’s internal environment

• Regulates the exchange of materials between the internal & external environment

• Consists of 1 or more layers of tightly connected epithelial cells

• Basement membrane = boundary between epithelial tissue & connective tissue

• Avascular but innervated-contains no blood vessels but supplied by nerve fibres

• High rate of regeneration- rapidly replaces lost cells by cell division

Epithelium Classification

• Epithelial tissue can be classified in two ways

  • Functionally – Exchange, transportation, protection, secretory

  • Structurally – by the shape of the cells and the number of layers of cells

• Each tissue requires specific epithelial tissue to allow it to function

Summary- Epithelia: Simple

Connective Tissue

• Four classes

  • Connective tissue proper

  • Cartilage

  • Bone tissue

  • Blood

• Consists of cells within an extracellular matrix (ECM)

• ECM consists of protein fibres (collagen, elastin, reticular) and specialized molecules (eg proteoglycans) that provides structural and biochemical support to the surrounding cells.

• There are many types of connective tissue with quite varied structures and functions:

  • Many connective tissues bind other tissue types & organs together eg connective tissue proper

  • Provides support & protection eg bone, cartilage

  • Specialist tissues/functions include adipose tissue: insulation, fat/fuel storage and blood: transports substances around the body

Organ system level
1. Chamical level

2. celular level

3. tissue level

4. organ level

5. organ system level

6. organism level
   

Dual organ systems

Major tissue types

Major skin layers