Human Biology Study Notes

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Biology exam
Endocrine system:
Hormones: chemical messengers that coordinate the body’s activates. Substances secreted by cells that act to regulate the activity of other cells in the body. They are part of the endocrine system and they are slow acting but have a longer affect than neurotransmitters. Functions:

* regulate growth, development, behavior, and reproduction. * Maintain homeostasis
* Regulate metabolism and water and mineral balance
* Respond to external stimuli
* Exocrine glands: secrete substances ( water/enzymes/ mucus) through tube like ducts. * The ducts transport the substances to specific locations inside and outside the body. Ex. Liver, sweat glands, mucus glands, salivary glands, other digestive glands

The endocrine system consists of:

* Endocrine glands: ductless organs that secret and make hormones either in the bloodstream or into extra cellular fluid

* Another hormones source: specialized cells in: brain, stomach, liver, small intestines, heart, and others. __

Target cells: specific cells to which a hormone travels to produce a specific effect. ^ have receptors: proteins that bind specific signal molecules that cause the cell to respond. (Found in: cell membrane/ cytoplasm/ nucleus of the cell)

How they work?
1. Each receptor binds to a specific hormone.
2. a hormone binds to a receptor
3. the binding triggers events that lead to changes within the cell. __
second messenger is a molecule that initiates changes inside a cell in response to the binding of a specific substance to a receptor on the outside of a cell.

Urinary system:
Functions:
1. Maintains homeostasis by regulating the content of water and other substances in blood. 2. Removes waste.
Excretion: the process of removing metabolic waste.
Main waste products the need to be eliminated:
* Carbon dioxide(from cellular respiration) removed by lungs * Nitrogenous compounds (from the breakdown of proteins) removed by kidneys Ex. Urea: nitrogenous compound made by the liver.
Formation of urea:
1. Ammonia (nitrogenous waste) very toxic. Cell harming. Is in blood. 2. Blood is filtered from ammonia in the liver
3. Liver converts ammonia into urea
4. Urea enters blood stream then finds its way to kidneys 5. Urea is removed by kidneys
Organs in this system:
1. Kidneys:

Shape: bean shaped the size of a fist
Location: one behind the liver, one behind the stomach
Function: regulate the chemical composition of the blood
Structure:
- renal cortex (outermost portion of the kidney) 1/3 of kidney mass - renal medulla (inner 2/3s of the kidney) consists of structures that carry urine, which empties into: -renal pelvis (funnel shaped structure in the center of the kidney) __

Blood flow:
* Blood enters from: renal artery (transports waste and nutrients) These nutrients are used by the kidney cells to carry out their life process. Ex. Of a process: removal of waste.
* Blood leaves from: renal vein: transports the filtered blood back to the heart. __

NEPHRONS: the functional part of the kidneys
Shape: tiny tubes
Location: the kidneys
Function: making urine
Urine: amber colored liquid, its substances removed by the kidneys from the blood (water, toxins, urea, salt, and minerals: those remain in distal convoluted tubules) All urine from all DCT goes to collecting duct. Osmosis occurs, 99% of water returns to blood. Structure of nephron:

* Bowman’s capsule: at an end of a nephron, cup shaped capsule surrounding a tight ball of capillaries that retains cells and large molecules in the blood and passes wastes dissolved in water through the nephron. * -------------------------------------------------

Glomerulus: a fine network of capillaries within the Bowman capsule. The capillaries come from arterioles.

THREE MAIN PROCESSES IN NEPHRONS:
1. Filtration: Materials from the blood are forced out...
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