Monday, Sept 17th 2012
Why do you eat?
- Comfort, to survive, bored, stress, socially,
Hunger: physiological NEED for food (your body needs it)
Appetite: psychological WANT for food (your brain wants it); ex. That cake looks good, I want it; everyone was having
cake; I was sad so I ate cake.
How does our body tell us we are hungry?
Nerve signals: your stomach and intestines send nerve signals to the hypothalamus of the brain; “we’re empty,eat”
Blood sugar levels drop: insulin and glucagon levels in the blood change (these are hormones); this is a signal for your
hypothalamus; “time to eat”; there are lots of other hormones that send messages.
Basics of Digestive System
1) Digestion: breaking food into tiny pieces; takes a whole sandwich and breaks it into microscopic particles and
puts it into your cells.
2) Absorption: moving the tiny pieces from your intestine into the cells and blood stream.
3) Elimination: getting rid of waste.
- Very important pat in chemical digestion
- Made of protein
- Biological catalysts; facilitate chemical reactions in living things
- You know it is an enzyme when it has a suffix of –ASE.
Cephalic Phase: makes you salivate; gets your digestive track starting.
Mechanical Digestion: your teeth break up the food
Chemical Digestion: enzymes in your saliva start breaking up the food; salivary amylase breaks up starch, lingual lipase
breaks up fat.
Making a bolus: a moist ball of food.
Swallowing: a delicate process; part conscious, part unconscious; epiglottis is open, esophagus is closed.
Peristalsis: waves of muscle contractions that move food; inner circular muscles; outer length wise muscles; p starts in
esophagus and continues through your GI tract; food moves into stomach via lower intestine.
churns: mechanical digestion; 3 thick muscle layers churn and break up food; food turns to chime.
Burns: chemical digestion; hydrochloric acid (HCl) denatures protein (unravels); pH of gastric juice is 2.0 (1 is most
acidic); pepsin (an enzyme) breaks down protein
Mucus lines your whole GI tract;
Pancreas: produces and adds biocarbonte to neutralize the acid and enzymes. Small Intestine:
Duodenum: chemical digestion and some absorption
Jejunum: digestion continues but LOTS of absoroption
Ileum: the last of the absorption
Getting nutrients into cells:
Large intestine: water absorption (small intestine doesn’t really absorb water); contains friendly bacteria (digests what
you cant such as fibre); produce gas and vitamin K; produce fats that it uses; rectum: holds feces until its eliminated.
BORBORIGMUS: medical terminality for stomach growling; movement of gases in the intestines; doesn’t necessarily
mean your hungry.
Facilitative diffusion requires membrane protein
WHEN DIGESTION GOES WRONG
Gastro esophageal reflux disease (GERD); Chyme (very acidic) from the stomach in the esophagus; could be because
lower esophageal sphincter may be damaged or not working hard enough; hydrochloric acid in the stomach begins to
1) Physical damage – bulimia, or injury. (Dysfunctional sphincter)