BIOS 255 Proficiency Test
negative feedback
a process in which the body senses a change and activates mechanisms that negate or reverse
it
-opposes signal stimulus
-most common feedback loop
-examples: thermoregulation, blood sugar regulation, blood pressure regulation
-components: stimulus~sensor~control~effector
negative feedback of blood pressure
blood pressure decreases-baroreceptors respond-they send signals to cardiac center-heartbeat
accelerates-blood pressure back to normal
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negative feedback of thermoregulation
body temp rises-brain is stimulated to send signal to sweat glands-sweating starts
positive feedback loop
self-amplifying cycles in which an initial change leads to a greater change
-enhances original stimulus
-examples: giving birth, blood clotting, lactation
giving birth positive feedback loop
head of baby pushes down on cervix and causes contraction-nerve impulses on cervix sent to
the brain-brain stimulates for oxytocin release-oxytocin creates more contractions
, epithelial tissue
Sheets of tightly packed cells that line organs and body cavities
-usually exposed to the environment or to and internal space in body.
-have no blood vessels
-usually lie on a vessel rich layer of connective tissue
-highly regenerative
Glycosaminoglycans
negatively charged, they attract sodium and potassium ions which cause them to absorb and
retain water
-play an important role in regulating the water and electrolyte balance of tissues
3 types of protein fibers in connective tissue
-collagen fibers: strong and stretch resistant
-elastic fibers: flexible and resilient
-reticular fibers: form and interwoven framework
function of keratin in epidermis
linked by desmosomes that gives skin durability
merocrine glands
sweat glands that function in evaporative cooling; widely distributed over the body surface; open
by ducts onto the skin surface
apocrine glands
Sweat glands in the pubic and underarm areas that secrete thicker sweat, that produce odor
when come in contact with bacteria on the skin
sebaceous glands
secrete sebum (oil) into the hair follicles where the hair shafts pass through the dermis
steps of endochondral ossification
1. Development of cartilage model
2. Growth of cartilage model
3. Development of primary ossification center
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