Animal Physiology Exam- Resp. + Digest

Respiration

Process- mitochondria consume oxygen, produce CO2

Respiratory System

Facilitates transport and exchange of CO2 and oxygen to and from exchange areas

External respiration

Gas exchange; movement of oxygen into the cell, movement of CO2 out of the cell

• can have 4 steps: ventilation of surface, diffusion, gas transport, perfusion

Internal Respiration

Metabolic process of cellular respiration within cells; us O2 to make energy

Oxygen transport pathway

O2 cascade: Moves oxygen from environment to mitochondria; and CO2 in opposite direction

Ficks 1st law

A solute will move from high to low concentration across concentration gradient

Ficks 2nd law

The amount of substance diffuses across a surface is proportional to area of that surface, inversely proportional to distance across it diffuses

Ventilation

External respiration- active movement of respiratory medium, bulk flow

Perfusion

External respiration- gas uptake

Gills

• originate as evaginations (outpocket)

• external or in resp. cavity

• uni-directional (some backflow)

• Blood countercurrent to water

• Complex large surface-area

Lungs

• originate as invaginations, form internal cavity

• surrounded by pleural sac

Spiracular Breathing

(Resp. on land) - control air flow to trachea, water loss, keeps out dust

• insects have unique tracheal system w/ air-filled tubes. tracheal ends v thin so short diffusion distance

Bird ventilation

• rigid inexpansible lungs

• Air sacs expand/contract w thoracic cavity

• requires 2 cycles of inhale/exhale

• Air crosscurrent to blood (perpendicular), most efficient

Conducting Zone

• Upper airway, respiratory tract

• No gas exchange btw air and blood

• Protected by cartilage and smooth muscle

Respiratory Zone

• Bronchiole, alveoli

• Site of gas exchange

• Not protected, makes gas exchange more efficient

Daltons Law

Total pressure is sum of all partial pressures of gaseous mixture

• Atmospheric pressure 760atm = partial pressure of nitrogen, O2, Water, CO2, etc.

Boyles Law

Gases move from high to low pressure

• Pressure of gas is inversely proportional to the volume of its container

Henrys Law

Concentration of gas in a liquid is proportional to solubility and partial pressure of gas

• ie. partial pressure of O2 or CO2 is proportional to concentration in blood

Pleura Sac

2 sheets with fluid between them, surrounds lungs

Pressure is sub-atmospheric at rest so it pulls when chest wall expands

Inhalation

Active; external intercostal muscle contraction, pull ribs up and out; diaphragm contracts down. Increases chest cavity capacity.

^ thoracic vol , ^ lung vol , negative pressure, air flow in

Passive Exhalation

Elastic recoil of thoracic cavity and lungs

thoracic/lung vol \/ , positive pressure, air flow out

Active Exhalation

During intense breathing or exercise; ribs contract in and down, abs contract push diaphragm up

thoracic/lung vol \/ , positive pressure, air flow out

Tidal ventilation

Air moves in/out through same path

ie. NOT unidirectional

Counter-current exchange

Oxygen-poor capillaries are closest to alveolus

Epithelial cells

Type 1 cells in alveolar membrane

• make contact with air

Surfactant Cells

Type 2 cells in alveolar membrane

• For lung compliance, reduce surface tension

Hemoglobin

Transports O2 in blood. Tetrameric respiration pigment of 4 O2-binding sub-unit

Sub units have 4 heme rings, one globin chain (bind O2)

1Hb = 4 globins (2 alpha, 2. beta chains) + 4 hemes CO2, H+, and phosphates

Oxygen Equilibrium

Relationship between percentage of oxygenated respiration pigment in blood at different partial pressures

• ie. as part pressure increases, more Hb mols will bind to O2 until 100% saturation

P50

Oxygen affinity of respiratory pigment; oxygen partial pressure where pigment is 50% saturated

Myoglobin

(muscle tissue)

monomeric, hyperbolic curve because each mol binds to one O2 mol

pH

Factor impacting Hb-O2 Affinity

Inc. P CO2 shifts curve right

Dec. pH shifts curve right

Bohr Shift

Temperature

Factor impacting Hb-O2 Affinity

Inc. temp improves O2 unloading on tissues

(active muscles ^ blood temp, shift curve right)

Central Chemoreceptors

Sensory neurons that regulate breathing- in ventrolateral surface of medulla, responds to PCO2 and pH changes of cerebral spinal fluid

Peripheral Chemoreceptors

Sensory organs in carotid and aortic arteries, sense changes in PO2, PCO2, pH

Energy

Ability to do work by joules and calories

Transferred in biological processes or transformed, NOT created or destroyed

Kinetic

Type of energy

Energy of movement; cell and tissue level as well

Potential

Type of energy

Energy to be used up, trapped in systems or bonds. Released when bonds are broken

Cell Metabolism

All chemical reactions inside cells

Metabolic pathway

Series of chemical reactions yielding a final product

Anabolic or catabolic

Anabolic

Path that requires energy

Eg. Photosynthesis

Catabolic

Breakdown path requiring no energy; releases energy

Eg. Cell respiration

Digestion

Food/nutrient sensing

Food capture

Mechanical disruption

Chemical processing and assimilation

Phagocytosis

Sponge digestion strategy

Water in channels by flagellated choanocytes. Digestion intracellularly in endocytic vacuoles of choanocytes

Digestion

Complex Digestion - Assimilation

Chemical breakdown of larger nutrients to smaller molecules

Absorption

Complex Digestion - Assimilation

Transport of small molecules from GI tract to blood

Secretion

Complex Digestion - Assimilation

Transport of substances to lumen of GI tract to aid digestion and absorption

Motility

Complex Digestion - Assimilation

Movement of GI content along tract (peristalsis) using smooth muscle

Carnivore

Diet Challenge: Protein and fat digestion

Herbivore

Diet Challenge: Cellulose Digestion

Omnivore

Diet Challenge: Mixed macromolecules

Stomach

Funct: store food, mech breakdown, disrupt chem bonds (vie low pH), produce intrinsic factor to absorb B12

Distend 50x by rugae fold

Gastric Pit

Secreted “juice” into lumen from glands via pituitary. Mixes to from chyme

• Chief cells, parietal cells, enteroendocrine cells, mucous neck cells

Chief Cells

Gastric Pit- secretes pepsinogen

Parietal Cell

Gastric Pit- secrete H+

Enteroendocrine cells

Gastric Pit- (G cells) secret gastrin

Mucous Neck Cells

Gastric Pit- Secretes mucus

Cephalic Phase

Increases production of gastric juices; minutes long

• Prod acid and enzymes by mucosa, begins when see/smell/think food

• Directed by CNS (PsNS), preps stomach to receive food; vagus nerve and post-ganglionic PS fibres innervate

Gastric Phase

Acids and enzymes process ingested mat, build on stim from cephalic, 3-4 hours

• Local: distend gastric wall stims parietal cells and acid secretion

• Hormonal: Neural and peptide + AA stim secretion of gastrin, stims mixing

• Neural: stretch +chemoreceptors trigger short reflex, causes mixing waves

Intestinal Phase

Chyme enters small intestine so stomach doesn’t stretch, ctrl rate of emptying to ensure digestion and absorption

Hormonal: Arrival of chyme, low pH stims secretin

Neural: Chyme leaves, reflex inhibits gastrin, contraction slows chyme and stims pyloric sphincter

GIP

Duodenum peptide- Inhibits gastric secretions ~ 5 hours

Secretin

Duodenum hormone- Stims water and bicarbonate to increase chyme pH and bile release/ production ~4 hours

CCK

Duodenum hormone- Stims expulsion of bile from gallbladder, pancreatic enzyme secretion, reduce appetite

VIP

Duodenum hormone- Stims bloodflow (ie. vasodilation), inhibits acid production by stomach

Bile

Secreted digestive chems and liver waste products in intestine

Produced in liver, stored in gallbladder

Phospholipids (Uptake lipids), Bile Salts (emulsify fats)

Pancreas

Secretes…

Amylase- break down glycogen and starch

Protease- break down protein, activates in intestine

Lipase- break down triglycerides

Amylase

Breaks down glycogen and starch

Released from pancreas

Protease

Breaks down protein, released inactive but activates in intestine

Released from pancreas

Lipase

Breaks down triglycerides

Released from pancreas

Small intestine

Large surface area, performs most of digestion and absorption of nutrients, water, vitamins, ions

Duodenum, jejunum, illeum

Duodenum

Secretes pancreatic juice, contains digestive enzymes and bicarbonate

Secreted bile, contains bile salt and bicarb to increase pH to alkaline

GIP, secretin, CCK, CIP

Peristalsis

Smooth muscle moves bolus along length of digestive tract

Enterocytes

Part of mucosal cell

Absorptive cells w microvilli

Goblet cell

Part of mucosal cell

Secrete mucous

Enteroendocrine Cell

Part of mucosal cell

Secrete hormones

Paneth Cell

Part of mucosal cell

Secrete antimicrobial mols, immune function

Protein

Functions to…

Support muscle mass + healthy aging

Increase satiety, help w weight management

Maintain metabolic health

Lipids

Complicates digestion due to hydrophobicity

Bile emulsifies them into micelle droplets

Broken into fatty acids and monoglycerides

Diffuse across cell membrane into enterocyte- transport depends on physical properties

Carbohydrates

Polysaccharides and disaccharides broken into monosaccharides, absorbed by enterocytes

Catabolic breakdown

Amylase from mouth/pancreas; maltase, sucrase, lactase from small intestine

Glucagon

Secreted by alpha cells

Stimulate glucose release in blood in response to low blood glucose

Insulin

Secreted by beta cells

Promote glucose uptake from blood in response to high blood glucose

(constant high glucose can cause resistance to this)

Suppresses appetite

Normal

Glucose spike after every meal

• Controlled insulin release, return to baseline within ~2 hours

• Carbs → glucose in small intestine

Large or frequent

Glucose spikes

• Caused by rapidly absorbed carbs; large insulin response

• Challenge stable blood sugar

Repeated

Glucose spikes

• Cause reduce response of cells to insulin, so pancreas makes more to compensate

• High risk for T2 and metabolic syndrome

Leptin

Long term appetite suppressant

Produced by adipose, suppresses appetite

• When fat is low, this is low, and appetite is high

PYY

Short term appetite suppressant

Secreted by small intestine after meals

Ghrelin

Short term appetite stimulant

Secreted by stomach, signals hunger

• increases w/ weight loss, making dieting difficult

GLP 1

Hormonal peptide release form L cells in small intestine

Regulate blood sugar levels by stimulating the release of insulin, suppressing glucagon secretion

Semaglutides

GLP-1 agonists

Manage blood sugar levels for T2, causes weight loss

Resistant to degradation (long-lasting), extends AA half life and adds fatty acid change tp be more stable

Large Intestine

Absorbs water and inorganic ions

Stores indigestible mat/bac until feces is expelled, NOT absorbing nutrients

Begins at end of ilium, ends at anus

SCFA

Produces by fermentation of fibre in large intestine: acetate, propionate, butyrate

• immune function

• appetite/satiety by PYY and GLP-1

• gut-brain communication, produces serotonin, dopamine

• Modulate/manage stress response (HPA axis)

Keto

Diet- low carb, hight

Goal: shift fuel source

reduce glucose spikes and insulin

Ketone production, change appetite regulation

Int. fasting

Diet- breaks between eating

Goal: shift between metabolic states

reduce insulin, glycogen depletion, uses fat and ketone as alternative energy

Effects appetite regulation