BIO 155 Midterm 1

Lectures #1-15

Homeostasis

The ability to maintain a stable internal environment

Components of Homeostatic Regulation

1. Sensor

2. Integrator

3. Effector

Allostasis

The body’s ability to adapt different set points to meet different requirements (Feed forward, anticipate a future physiological need)

Physiological Allostasis

Internal Integrators change their set point to adapt to different condition

Feedback Loops

Occur when change detected by a sensor triggers an effector response that changes the environment

Negative Feedback Loop

Return controlled variable BACK to its set point

Postive Feedback Loops

Enhance or amplify changes by moving the regulated variable AWAY from its set point

The ‘Why’s’ of Biology

1. Why - Mechanism

2. Why - Adaptive Function

Mechanism

What is the underlying process(es) that cause it to occur?

Adaptive Function

What is the benefit to the organism? (Evolutionary selection)

Structure Determines Function

The physical shape, makeup, and arrangement of a structure determines what/how it preforms

Trade-Off

Feature of a structure may reflect trade-offs between competing functions

Significance of Water

1. Solvent

2. Reactant

3. Lubricant

4. Surface Tension

5. High Heat Capacity

Significance of Carbon

Component of EVERY biological macromolecule (along with Hydrogen)

Classes of Biological Molecules

1. Carbohydrates → Sugars

2. Amino Acids → Proteins

3. Lipids → Fats

4. Nucleotides → Nucleic Acids

The Cell Cycle

1. Interphase (Cellular Functions)

2. Mitosis (Cell Division)

Tumor

Abnormal cellular overgrowth/division caused by disrupted regulation of the cell cycle

Cancer

Cellular overgrowth spread beyond the borders of the cell origin. Invades underlying tissue, spreads through blood vessels and other regions of the body (Metastasis)

Intracellular Fluid (ICF)

The Cytosol of a cell.

• Lots K+

• Little Na+

• Very little Cl-

• Many large anions

• Extremely small amount of Ca+

Extracellular Fluid (ECF)

• Lots of Na+

• Little K+

• Lots of Cl-

• No large anions

• Small amount of Ca+ (Greater than ICF)

Passive Transport

Molecules moving in accordance to the concentration gradient

• Free Diffusion

• Facilitated Diffusion

Free Diffusion

Molecules moving through freely in accordance to concentration gradient (High → Low)

Facilitated Diffusion

Molecules moving through membrane proteins in accordance to concentration gradient (High → Low)

Active Transport

Uses energy to move molecules AGAINST the concentration gradient

• Primary Active Transport

• Secondary Active Transport

• Vesicular Active Transport

Primary Active Transport

Pump protein uses ATP to move molecule/ion (ex: Na+/K+ pump)

Secondary Active Transport

Uses the gradient created by one molecule, to move another molecule

Vesicular Active Transport

Moves large molecule(s) in vesicles by endocytosis or exocytosis

Osmosis

Movement of water molecules across a selectively-permeable membrane causing changes in volume

• Isotonic (Stable)

• Hypotonic (Lots of water)

• Hypertonice (Little water)

Transmembrane Potential

Electrical potential of ICF and ECF. ICF is more negative than ECf

Cellular Differentiation

The production of different cell types through the expression of different combination of proteins

Types of Tissue

1. Epithelial

2. Connective

3. Muscle

4. Nervous

Functions of Epithelial Tissue

• Provide physical protection

• Control permeability

• Provide sensation

• Produce specialized secretions

Epithelium

Sheet of epithelial cells connected to a basement membrane

Basic Feature of Epithelial Cells

Polarization → Have an apical surface and basolateral surface

Tight Junctions

Intercellular protein complex that attach and seal epithelial cells together

• ‘Leaky’ tight junctions (Allow paracellular transport of water and molecules)

• ‘Tight’ tight junctions (Do not allow any movement)

Simple Epithelia

One layer

• Squamous

• Cuboidal

• Columnar

Stratified Epithelia

Mulitple Layers

Pseudo-Stratified Epithelia

ONE layer than appears to be multiple

Definition of Connective Tissue

Extracellular protein fibres suspended in a matrix (ground substance

Types of Connective Tissue

1. Connective Tissue Proper

2. Fluid Connective Tissue

3. Supporting Connective Tissue

Types of Connective Tissue Proper

1. Loose

2. Dense

Types of Loose Connective Tissue Proper

1. Areolar Tissue

2. Adipose Tissue

3. Reticular Tissue

Areolar Tissue

Type of loose connective tissue proper. Found underneath epithelial, around nerves, blood vessels and organs, and fills spaces around tissues

Adipose TIssue

Type of loose connective tissue proper, composed of fat storing cells found in the hypodermis

Reticular Tissue

Type of loose connective tissue proper, found in lymph nodes, bone marrow etc

Types of Dense Connective Tissue Proper

1. Dense regular

2. Dense irregular

3. Elastic

Dense Regular Connective Tissue

Type of dense connective tissue proper, made of tightly packed and orderly aligned collagen fibres. Found in tendons, ligaments, and aponeuroses

Dense Irregular Connective Tissue

Type of dense connective tissue proper, random mesh/web arrangement of collagen fibres, found in the reticular dermis, periosteum of bone, perichondrium of cartilage etc

Types of Supporting Connective Tissue

1. Cartilage

2. Bone

Types of Cartilage

1. Hyaline

2. Elastic

3. Fibrocartilage

Differences in Loose vs Dense Connective Tissue Proper

Loose - Lower density of extracellular fibres, more cellular diversity

Dense - Higher density of extracellular fibres, less cellular diversity

Cell Types of Loose Connective Tissue Proper

Fibroblasts, fibrocytes, mesenchymal cells

Fibroblasts

Secrete the proteins of extracellular matrix of loose connective tissue proper

Fibrocytes

Maintain the proteins of the extracellular matrix of loose connective tissue proper

Mesenchymal Cells

Stem cells that can divide and replace damaged fibroblasts

Proteins of Extracellular FIbres of Connective Tissue Proper

• Elastin

• Collagen

Elastin

Elastic properties, stretch and recoil

Collagen

High tensile strength, no stretch

Tissue Membrane

Cover inner and outer body surface. Consists of a layer of epithelial tissue with an underlying layer(s) of connective tissue

Fasciae

Layers of connective tissue surrounding the organs, are NOT attached to a layer of epithelia

Epithelial Tissue Repair

Rapid proliferation

Connective TIssue Repair

Increased rates of secretion

Clotting

Coagulation of blood cells to seal off blood vessel in response to connective tissue damage

Scar

Dense web of collagen fibres secreted at the site of connective tissue damage

Integument

Protects the body from the external environment. Consists of the cutaneous membrane and accessory structures

Parts of the Cutaneous Membrane

1. Epidermis

2. Dermis

3. Accessory Structures

Functions of the Integument

1. Barrier

2. Thermal Homeostasis

3. Sense organ

4. VItamin D and Ca2+ Homeostasis

Types of Skin

1. Thick Skin

2. Thin Skin

Thick Skin

Does not have any hair and has a thicker epidermis and thinner dermis. Has an extra layer in epidermis called the stratum lucidum

Thin Skin

Contains hair, has a thinner epidermis and thicker dermis

Layers of the Epidermis

Made of stratified squamous epithelium

1. Stratum Corneum

2. Stratum Granulosum

3. Stratum Spinosum

4. Stratum Basale

Layer of Epidermis Where Organelles are Lost?

Stratum Granulosum and above have no nucleus or organelles

Keratinized

Process where epidermal cells become filled with keratin. Begins when Basal cells differentiate into Keratinocytes in the Stratum Spinosum layer

Melanin

Absorbs UV photons to prevent cell/DNA damage

Melanocytes

Produce melanin pigment and passes it onto Keratinocytes. They are found within the Stratum Basale

Layers of the Dermis

Made of connective tissue

1. Stratum Papillare

2. Stratum Reticulare

Stratum Papillare

Made of loose connective proper (Areolar tissue)

Stratum Reticulare

Made of dense irregular, elastic connective tissue (Collagen+Elastin)

Stages of Integument Repair

1. Inflammatory - Triggered by mast cells, bleeding occurs

2. Migratory - Rapid cell division and migration to replace missing cells, scab forms

3. Proliferation

4. Scarring

Epidermis vs Dermis Repair

Epidermis - Proliferation of cells

Dermis - More Proliferation, recruitment, differentiation, formation of granulation tissue

Granulation Tissue

Formed during the proliferation phase of dermis repair. Mixture of blood vessels, mesenchymal cells, and fibroblasts

Scar Tissue

Cause by very high rates of proliferation and secretion from fibroblasts forming thick layers of unorganized collagen

Callus

Thickening of Stratum Corneum caused by strongly cross-linked keratinocytes

Accessory Neurons

Sensory neurons, glands, hair

Sensory Neurons of the Integument

1. Somatosensory (Touch) Neurons

2. Nociceptive (Pain) Neurons

Glands in the Integument

1. Sebaceous Glands - Secrete sebum

2. Sweat Glands - Secrete sweat. Apocrine glands found in axillary+pubic regions, and eccrine everywhere else.

Skin Role in Thermohomeostasis

Thermoreceptors (Sensor) in the skin sense temperature change, send signal to the brain (Control Centre) which sends a command, sweat glands (Receptors) in the skin respond

Evaporative Cooling

Liquid to gas transformation to reduce heat

Radiant Cooling

Cooling Down: Blood flows to top of skin to release heat (Reason why people get red when they’re warm)

Retaining Heat: Blood remains further down to prevent heat loss

Calcium Homeostasis by Integument

Synthesization of vitamin D allows the production of Calcitriol which allows for absorption of calcium via the gut

Vitamin D and Melanin Trade-Off

Higher levels of melanin means more protection for UV rays, but blocks some vitamin D from absorbing. Lower levels of melanin means more damage from UV, but more vitamin absorption

Effects of Aging on the Epidermis

1. Drier

2. Fewer melanocytes

3. Thinning

4. Decreased perspiration

Effects of Aging on the Dermis

1. Thinning

2. Diminished Immune Response

3. Slower Repair

4. Reduced blood supply

5. Loss of elastin

Hair and Skin

Highly keratinized accessory structures of the integument. Made up of dead cells, serve a protective purpose.

Cartilage

Supportive connective tissues located on joint surfaces, in the ears, nose, and vertebral discs

Ligaments

Dense regular connective tissue, anchors bone to bone, matrix of collagen and some elastin

Tendons

Dense regular connective tissue, anchor bones to muscle, matrix of collagen and no elastin

Cartilage and Bone Relation

• Both supportive connective tissue

• Dense, solid matrix

• Cartilage avascular and bone is vascular & innervated

Cartilage Matrix

• Chondroitin Sulfate

• Proteoglycans

Lacunae

Small cavities within the ECM of cartilage where chondrocytes live