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1. What are some cell types that are replaced on a regular basis? Why do we care?
- Skin cells (q 14-60 days)
- RBC (q 90-120 days)
- Digestive (q 3 days)
- Muscle cells (q few years)
- Liver (PRN)
- Brain (Never)
requires energy and building blocks to make new cells
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How do hormones from the pancreas regulate blood sugar?
High blood guar: produces insulin which stimulates cells to take up glucose. Liver and muscle cells store it as glcogen
Low blood sugar: produces glucagon which stimulates glycogen breakdown. Glucose released into bloodstream.
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I won’t ask you a lot of details on most of the body systems, but you should understand the main functions of organs/systems discussed in class. You should know the digestive system pretty well- what happens where, what organs release enzymes and what do they do?
Digestive system
Tract: long' flexible tube extending from the mouth to the anus of a length of 26 feet. Digestive organs secrete digestive juices and enzymes. Overall goal is to digest food and absorb nutrients and excrete wastes.
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Body Fluids / CV system blood
Blood travels in arteries, veins and capillaries.
- Picks up oxygen in lungs, picks up nutrients (except fats) from the digestive system.
- All nutrients must first pass the liver.
The kidneys filter wastes and toxins from the blood.
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Body Fluids / CV system lymph
- Separate vessels (lymphatic system)
- Picks up fats from the digestive system and deliver to bloodstream
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Body Fluids / CV system extracellular fluid
- Derived from the blood in capillaries
- Some re-enters cappilaries
The rest froms lymph which enters lyphatic vessels and is ultimately returned to the bloodstream.
Lymph nodes filter the lymph and remove harmful substances/ pathogens.
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Body Fluids / CV system intracellular fluid
Inside cells
Derived from extracellular fluid
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Hormones
Released into bloodstream from endocrine glands.
Bind to receptors on target cells and initiate a response
Glands monitor conditions and produce hormones to regulate them.
Fasting, eating, and exercise all affect hormone levels.
Hormones regulate hunger and appetite and controls digestive organs' activity
Loss of appetite in sick people is related to hormones.
Stress response (acute): suppresses hunger and digestion/absoprtion of nutrients
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The nervous system
Hypothalamus monitors availability of nutrients and water.
Digestive tract signals nutrient levels and hunger to hypothalamus via nerves and hormones
When message from hypothalamus reaches cortex, we feel hunger but can consciously override this need from some time.
Neurons susceptible to nutrient deprivation. Require glucose as their energy source.
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Immune System
First line of defense: skin and lining of body cavities - highly sensitive to vitamin and other nutrient def.
Immune defense: WBC
phagocytes: (nonspecific) engulf and digest invaders "first responders"
lymphocytes: specific response mass production in times of need which requires nutrients/energy
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Immune System T Lymphocytes
(Killer T cells Cytotoxic)
Need pahgocytes and helper t cells to recognize an antigenkill all invaders with that antigen.
Especially good at killing infected/damaged cells
- Helper T Cells
- Help Cytotoxic T cells and B cells to recognize antigens.
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Immune System B Lymphocytes
Make antibodies that stick to invaders
Kill them directly or mark them for phagocyte destruction
Can't attack invaders that have entered a cell
*ALL lymphocytes remember the antigen for next time.
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Immune System Inflammation
- Results from injury irritation or infection.
- Redness, heat swelling, pain.
Chronic diseases are accompanied by chronic inflammation (heart, diabetes, arthritis)
Dietary factos can promote or inhibit inflammation
Being overweight/obese promotes a state of mild chornic inflammation.
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Digestion Mechanical
- Mechanical:
- Physically breaking down food.
- Mouth: chewing
- Stomach: further breakdown into smaller particles. Peristalsis waves of muscle movement that propel food through the digestive tract.
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Digest Chemical
- Breaking down food into molecules that can be absorbed.
- Mouth: enzymes in saliva break down starch
- Stomach: enzymes and acid break down proteins
- Small intestine: receives digestive fluids from liver and pancrease
- Liver: bile emulsifies fats
- Pancrease: enzymes finish food breakdown and bicarbonate neautralizes stomach acid
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Digestion absorption
- Primarily in the small intestine
- Folds, villi, and microvilli: each villus has its own capillaries and lymph vessel.
Most nutrients go into capillaries to liver.
Fats and fat-soluble- vitamins go into lymph vessels to blood stream.
Malnutrition can shrink surface of small intestine by 90%.
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Digestive System Wastes Intestines / colon
Large intestine/colon absrobs water and a few minerals; bacteria digest some of the fiber.
Resulting feces are storied in the rectum and excreted
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Digestive System Wastes Liver
Liver pulls waste out of bloodstream adds to biles, sends to digestive tract to be excreted.
Sends them to kidneys for dispole in urine.
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Digestive System Wastes Kidneys
- Filter all our blood.
- Wastes are concentrated in urine and sent to bladder. Sodium excretion/retention by the kidneys affects blood pressure.
Regulate fluid volume. Require an abundant supply of water and a well functioning CV system.
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Digestive System Storage
Liver stores excess glucose as glycogen. (readily accessible but quickly depleted.
Muscles do the same but only for themselves.
Fat is sent out from the liver; all cells take what they want. Fat cells in adipose tissue store it long-term (days, weeks, months)
Vitamins often stored in liver or fat cells.
Bones have reserves of calcium and other minerals.
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