HOMEOSTASIS IN HUMANS Flashcards
body fluids
the fluid that body cells consist of and are surrounded by; forms the internal environment of the body
factors to be constant for cells to function optimally
- glucose
- salt
- water
- oxygen/c02
- temperature
organs that help to maintain a constant int env
liver, kidneys, skin, lungs, pancreas
homeostasis
maintenance of a constant internal environment in the body
negative feedback mechanism
when a deviation from the normal is detected, which results in a reaction that counteracts the change and returns it to normal
how negative feedback system works
- change occurs in normal levels
- receptors detect and transmit info via hormones or nerve impulses to the effectors
- effectors respond and correct the deviation
- normal is detected and corrective action is switched off
control of CO2
- chemoreceptors send impulses to resp and cardio centres in the brain as soon as co2 conc changes
- resp centre sends impulses to diaphragm and intercostal musc to acc contract/relax
- breathing rate and depth inc, more CO2 exhaled
- cardio centre send impulses to heart musc to inc heart rate + blood flow
- co2 transported faster to lung for exhalation = normal
control of water
- change in normal
- osmoreceptors in hypothalamus detect
- thirst centre stimulated / ADH secreted into blood = transport to kidneys
- walls of tubules become permeable
- more water reabsorbed
- water content rises
- normal
control of salt
- sodium conc is low = more aldosterone is secreted and more sodium ions are reabsorbed from the convoluted tubes into the blood in surrounding capillaries
- sodium conc in blood inc, less excreted in urine
- normal
thermoregulation
regulation of body temp in an organism
ectothermic animals eg
fish, amphibians, reptiles
ectothermic animals
- body temperatures vary according to environmental temp
- reptiles use color (dark) and body orientation to regulate body temp
endothermic animals
birds, mammals
- constant body temp, irrespective of env temp
- heat produced inside the body via resp
why humans need to be 37
optimum temp for enzyme action, too high = denature, too low = inactive
heat production in human body
- resp is main source
- heat can be absorbed from environment by consuming warm food/fluid/exposing body to sun
adrenalin + thyroxin in heat prod
increased secretion of the two results in inc metabolic rate. resp increases bc of this and more heat is released
heat loss in human body
radiation
convection
conduction
evaporation
radiation
loss of heat from warm body to cold env via rays + waves
convection
distribution of heat in fluids or gas
conduction
transfer of heat energy from warm to cold objects that are in contact w each other
evaporation
when a fluid absorbs heat energy to convert to a gas
two layers of skin
dermis
epidermis
epidermis three lyers
cornified, granular, malpighian
cornified layer
- outermost layer, dead flattened cells
- contain keratin
- continuously replaced by the underlying tissue
keratin functions
protects skin from water, light and infection
granular layer
directly under cornified layer and consists of living cells w granules in the cytoplasm
malpighian layer
lower layer, consists of living cells that continuously divide to replace cells in upper layers
- contains melanin
- receives oxygen + nutrients from the dermis
melanin
protects skin from UV rays from sun + gives skin color
epidermis function
protects underlying tissues
dermis
thicker layer than the epidermis and consists of areolar connective tissue
dermis contains…
blood + lymph vessels, nerves, sensory organs, hair follicles, tiny erector musc, glands
beneath the areolar connective tissue
a layer of adipose (fatty) tissue that connects skin to underlying body parts; serves an insulator
blood vessels in d
- transports nutrients in the blood to cells and waste products to sweat glands for excretion
- helps w body temp reg
lymph vessels in d
drain excess tissue fluid
nerves in d
- sensory fibres - conduct impulses from sense organs in skin to CNS
- motor fibres - conduct impulses from thalamus to blood vessels in the skin
sensory organs
various corpuscles which detect heat, cold pressure, touch and pain
hair follicles
- an extension of epidermis, all over body except palms and soles
- hair grows from follicle
sebum
fatty substance, secreted by sebaceous glands, which helps to prevent dehydration of skin and hair
erector muscle
connects base of hair follicle to the epidermis (contracts when it is cold, causes hair to stand up)
glands
sebaceous, wax, mammary, sweat
wax glands
occur in ext auditory canals of ear and secrete cerumen which prevents insects from entering the auditory canals
mammary glands
secrete milk after birth for babies
sweat glands
long coiled ducts in the dermis which extend to sweat pores = excretes harmful waste products in a water medium + play a role in regulation of body temp by cooling the body
heat regulation centre
in hypothalamus is resp for maintaining body temp
stimulated by nerve impulses from receptors in skin which detect changes in temp + by changes in temp of blood that flows through it
regulation of body temp on a cold day
- drop in temp is detected by Krause and converted into impulses that stimulate HRC
- thalamus sends impulses to the involuntary musc layer in the skins blood vessels
- circular musc contracts and blood vessels narrow in vasoconstriction
- blood is redirected to vessels in deeper skin layers and less blood flows to skin surface = less heat lost
- less blood flows to the sweat glands / reduced sweat secretion
