Lecture Final: Chapter 19

Question 1

Define the following

• homology
• analogy
• homoplasy

Answer 1

HOMOLOGY: processes / mechanisms that are derived from a common ancestor but are in two different species
– Body shape in the seals / penguins / tuna is NOT a form of homology

ANALOGY: processes / mechanisms that are similar in species function-wise but are NOT derived from a common ancestor

• • Body shape IS a form of analogy
• • Ie. seals / penguins / tuna have streamlined bodies for swimming BUT different attachments within the body physiology → analogous; not homologous

HOMOPLASY: things just look alike
– Body shape is also HOMOPLASTIC → therefore cannot use body shapes of these organisms as a way to determine their relationship

Question 2

Body Plan of Typical Mammal – Problem, solution, extra tidbit

Answer 2

Problem: most cells are too distant from surface to enable diffusion to exchange materials with environment

Solution: have exchange surfaces with large surface areas and thin / permeable barriers + convective transport mechanism to get gases / nutrients / wastes to sites where diffusion can occur → basically another way to maintain homeostasis

• • Lungs SA = 180 m squared
• • Digestive tract SA = 300 m squared

Consider this: tube within a tube – any material inside the alimentary / digestive tract is still considered “outside” the body

Question 3

Types of Tissue (4)

Answer 3

composed of cells; make up organs (which make up organ systems)

1. Connective: derived from mesoderm; bulk of the body; acts as the padding holding you together –STRUCTURAL SUPPORT → incl adipose, bone, cartilage, blood
2. Epithelial: “epi” = top or outermost lining – PROTECTION, SECRETION, ABSORPTION
3. Muscle: allows for MOVEMENT bc irritable and contractible
4. Nervous: coordination center of the body bc irritable and conductive – COMMUNICATION, COORDINATION, CONTROL

Question 4

Epithelial Tissue

• naming
• functions (4)
• polarity (2 ; 2sub2)

Answer 4

Shape:

1. Squamous: flat → ie skin
2. Cuboidal: cube shaped → ie. lining of tubes in kidney
3. Columnar: rectangular; used for absorption and secretion → ie. intestine, respiratory tract

Number of layers:

1. Simple: single later; good for diffusion
2. Stratified: many layers; good for protection

avascular but innervated (lacking blood vessels but has nerves)

1. Barrier / Lining
2. Secretory (glandular)
   - - Exocrine: has a duct; reaches surface of lining
   - - Endocrine: no duct; released into interstitial fluid and affects cells with appropriate receptors that respond → ie. hormones
3. Absorptive
4. Sensory

Apical surface: faces the LUMEN; fringe resultant of villi (purpose: increase surface area in order to maximize absorption)

Basal: faces more inward towards the body → usually has a specific proteins

• • Basal lamina: forms a place for the cells to sit and can act like a filter / assistant for diffusion
• • Specific proteins: Na+/K+ ATPase pump found in the basal surface; helps to create an electro gradient needed for contraction by creating the inside of the cell negative

Question 5

Covering and Lining Membranes (3)

Answer 5

Continuous multicellular sheets composed of EPITHELIUM bound to an underlying layer of CONNECTIVE tissue

1. Cutaneous: dry membrane (exposed to air) consisting of keratin (protein), stratified squamous epithelium (epidermis); derived from ECTODERM → ie skin
2. Mucous: moist membranes that line all open body cavities (in contact with environment), consisting of either stratified squamous OR simple columnar; also derived from ECTODERM → ie lining of mouth
3. Serous: moist membranes that line all closed body cavities, consisting of simple squamous epithelium (specifically, mesothelium) resting on a thin layer of connective tissue; derived from MESODERM

Question 6

Proteins involved in the stitching together of the epithelium (4)

Answer 6

Tight junctions: near apical surface; SEAL THE CELL TOGETHER to prevent leakage and maintain polarity of the epithelium; act as a fence
– Membrane bound proteins wrap around BUT don’t need them where the sugar isn’t available, therefore will keep the polarity in place

Adherens junction: stabilize cells by having CADHERINS with bands of actin (cytoskeletal protein) → promotes cell to cell adhesion
– Cadherins: transmembrane proteins associated on the cytoplasmic face; spokes that act as a zipper

Desmosomes: again, spots of CADHERINS BUT will also have a protein plaque with intermediate filaments (made of protein keratin; orange fibers; also cytoskeleton protein) that provides flexion → desmosomes will be on opposite sides of the cell and will be connected by intermediate filaments, thus yielding strength to the cell

Gap junctions: Transmembrane connexons (six form a pore) from cell to cell that allow small, water soluble substances to move readily between cells and synchronize function for all cells as a unit (ie muscle contraction)

Question 7

Connective Tissue

• defined
• three components (3sub3)

Connective Tissue Types Part 1

• • LOOSE CONNECTIVE (5)
• • FIBROUS CONNECTIVE (2)

Answer 7

Defined as widely dispersed throughout the extracellular medium; exist in a medium that they secrete; mostly derived from MESODERM (specifically, mesenchymal cells) → act as a padding

Three components:

1. Cells: fibroblasts → blast = embryonic cell → osteoblast makes bones
   - - Versus CYTE: more mature cell → osteocytes: exists within the bones
2. Excretion of ECM: made of ground substance (gel like → can be fluid like loose connective or hard like bone)
3. Fibers: embedded in the ground substance
   - - Collagen: tensile strength
   - - Elastin: recoil ability
   - - Reticular: form a mesh support matrix

LOOSE CONNECTIVE TISSUE: aka areolar

• • Most common type in the body
• • Holds massive amount of interstitial fluid (acting as a reservoir for nutrients)
• • contains lots of fibers, immune cells (eg. mass cells that respond to infection via inflammation), fibroblasts
• • Binds epithelia to underlying surfaces
• • Vascularized and innervated

FIBROUS CON TISSUE:

• • Highly organized COLLAGEN fibers typical of tendons and ligament
• • Poorly vascularized, therefore if damaged will take longer to heal

Question 8

Connective Tissue Types Part 2

• • CARTILAGE
• • BONE
• • ADIPOSE
• • BLOOD

Answer 8

CARTILAGE:

• • Collagen again embedded in RUBBERY matrix (chondroitin sulfate that is secreted by chondrocytes)
• • Strong and flexible due to tensile strength but poorly vascularized therefore will heal slowly as well

BONE: essentially mineralized cartilage formed by osteoblasts

• • collagen fibers resist tension and HYDROXYAPATITE CRYSTAL OF Ca2Po4 which resist compression and are insoluble at low pH
• • Vascularized and innervated!!

ADIPOSE:

• • Storage of excess nutrients; can act as a cushion / insulation for organs
• • Minimal ECM
• • Highly vascularized

BLOOD:

• • Generated in red marrow of bone → derive from mesoderm
• • Has ECM called PLASMA

Question 9

Ground substance (2)

Answer 9

basically the foundation for the extracellular matrix, which are secreted by the fibroblasts

Proteoglycan: consist of CORE PROTEINS linked to GAG (glycosaminoglycans; polysaccharides that absorb water and become gel like → the more absorbed, the more gel-like, the more it can resist compression)

GAGs are repeating disacch that are highly negatively charge and attract water

• • versus Polysacch chains are too stiff to fold + are rly hydrophilic
• • Negatively charged GAGs will attract Na+ ions that lead to OSMOTIC SWELLING, creating turgor pressure for shape and cushioning

Question 10

Muscle Tissue (4)

Answer 10

Derived from mesoderm; use Ca2+ to trigger contractions; can have more than one nucleus

Striations: represent the orderly arrangement of actin and myosin in sarcomeres (functional units of skeletal muscles)

Skeletal: striated and voluntary; multinucleated; cells are electrically isolated from each other → Ca2+ ions bind to troponin to allow myosin and actin binding

Smooth: non striated and involuntary; uninucleate (one nucleus per cell); cells electrically coupled together via gap junctions → Ca2+ ions bind to calmodulin to allow for myosin and actin binding

Cardiac: striated and involuntary; at most 2 nuclei per cell; cells are also electrically coupled via gap junctions → Ca2+ ions also bind to troponin to allow myosin and actin binding

Question 11

Nervous Tissue

• types of cells involved (2)
• types of glial cells (4 ; 1sub2)

Answer 11

Derived from ectoderm; irritable and conductive because of connected cells
CELLS THAT ARE WIRED TOGETHER, FIRE TOGETHER

TWO CELL TYPES:

1. Neurons: cells that communicate via electrical signals; organize the grids and circuits that work for the higher order of perceptions; used to respond to the world
2. Glial: “glue” – the support cells for the neurons (which work 24/7); much more plentiful

TYPES OF GLIAL CELLS:

1. NEUROGLIAL: provides insulation via myelin sheath;
   - - Schwann Cells: found in PNS; helps to accelerate nerve signal as it travels across axon due to the Nodes of Ranvier (saltatory conduction)
   - - Oligodendrocytes: found in CNS
2. MICROGLIA: clean up cellular debris via phagocytosis
3. ASTROCYTES: maintain blood brain barrier; support and repair neurons
4. EPENDYMAL: form epithelial lining of fluid filled containers in the brain; also form lining of spinal column (inside of which is the cerebral spinal fluid, which they help in manufacturing)

Question 12

Homeothermy
+ Regulators vs Conformers
+ Homeotherms vs Poikilotherms

Answer 12

HOMEOTHERMY IS REALLY EXPENSIVE!! But permits the fast nervous system that maintains ideal environment for cell processes (The warmer the system, the faster it works)
– Ie. snakes are cold blooded / move slower in cold → will react faster in warmth

Regulator: regulates internal temperature → typically will have an elevated temperature

Conformers: conforms to the temperature of the environment

Homeotherms: maintain a stable internal temperature (thermoregulate biologically and behaviorally)
– Regulated via internal mechanisms → endothermic

Poikilotherms: aka cold blooded; fluctuates to the temperature of the environment BUT CAN REGULATE by choosing location (thermoregulate behaviorally) – aka ectothermic (dependent on external heat sources)

Question 13

Thermogenesis by Endotherms

• Brown fat
• pathway

Answer 13

Consider the muscle activity of SHIVERING, which is present in humans except in NEONATES
– instead have BROWN FAT present in NEONATES (5% of total body weight in human infants) to counter heat loss that would other occur due to their high SA:V ratio

Non shivering thermogenesis occurs via ENDOCRINE SIGNALLING of brown fat to produce HEAT instead of ATP:

1. Endocrine signal NOREPINEPHRINE leads to activation of uncoupling proton 1 in inner membrane of the mitochondrion
2. Uncoupling protein 1: aka thermogenic protein THERMOGENIN; when activated, mitochondrion will create heat from the lipids of brown adipose tissue cells instead

Question 14

Physiological maintenance of body heat (5)

- make heat, want to keep it

Answer 14

1. Insulation – ie fat, hair
2. Vasoconstriction: can regulate the peripheral arterioles to keep warm blood in the CORE OF THE BODY → sacrifice extremities in order to save core organs
3. Countercurrent heat exchanger: heat block that requires juxtaposition (right next door) of warm arteries NEXT TO COLD VEINS
   - - Heat will diffuse from the arteries into the veins versus the environment
4. Countercurrent MULTIPLIERS generate gradients in nephrons in kidneys
5. Vascular networks known as RETE MIRABILE (miracle net)
   - - Passive exchanger since it only MAINTAINS the gradient
   - - Prevents heat loss only ; does not generate heat (that’s another process)

Question 15

Feedback mechanisms (2)
\+ types of change (3)
\+ Hiking everest as a tibetan example

Types of physiological change (2)

Answer 15

Negative feedback: maintain set point, contribute to homeostasis

Positive: moving towards a new set point → eg. clotting, labor ⇒ specifically, innate and adaptive immune responses
– ie. Immune system: GO HARD OR GO HOME → kill the sickness before it kills you

1. Acute Response: short term changes; reversible
2. Chronic: longer term changes due to acclimation; reversible
3. Evolutionary: changes in allele frequencies over generations; acquiring of a beneficial allele; irreversible

Ie. tibetans have acclimated to climbing everest bc they live at those altitudes all their lives (evolutionary) – as opposed to westerners who can climb up then rest to acclimate then climb again in order to acclimate (chronic)

• • acclimation basically increases number of RBC and efficiency of O2 usage BUT too many RBC can coagulate and cause a heart attacks
• • Tibetans fight this by having low RBC but larger lung size and higher rates of breathing

1. Developmental: programmed changes in physiology as indiv changes from conception to adult – ie puberty
2. Changes controlled by periodic clock: Repeating patterns of changes in individuals physiology under control of internal clock; can be daily or seasonal – ie circadian cycle

Question 16

Bioenergetics of an Animal (4)

Answer 16

Nutrient molecules in body cells can be used to create ATP (product) or HEAT (waste)
Every transformation of energy generates heat!!

Heat generated w every transformation of energy → 2nd law of thermodynamics

BMR = basal metabolic rate; minimum metabolic rate of a FASTING endotherm at rest in its thermoneutral zone

• • Declines as you age → numbers on manual
• • Males have higher BMR in kCal/day than female bc of skeletal muscle mass

SMR = standardized metabolic rate; USED FOR NON HOMEOTHERMS; metabolic rate of a non stressed, fasting ectotherm at rest at a particular temperature

Question 17

Surface area to volume ratio

– especially with smaller animals

Answer 17

Smaller animals have a larger SA:V – dissipate heat faster vs larger animals

Therefore, Smaller animals need to accelerate BMR to maintain the constant body temperature
– Therefore, will have higher heart rates; shorter life spans bc small heart is working harder

Heat loss proportional to SA, heat generation proportional to V