HOMEOSTASIS IN HUMANS

Question 1

body fluids

Answer 1

the fluid that body cells consist of and are surrounded by; forms the internal environment of the body

Question 2

factors to be constant for cells to function optimally

Answer 2

• glucose
• salt
• water
• oxygen/c02
• temperature

Question 3

organs that help to maintain a constant int env

Answer 3

liver, kidneys, skin, lungs, pancreas

Question 4

homeostasis

Answer 4

maintenance of a constant internal environment in the body

Question 5

negative feedback mechanism

Answer 5

when a deviation from the normal is detected, which results in a reaction that counteracts the change and returns it to normal

Question 6

how negative feedback system works

Answer 6

• 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

Question 7

control of CO2

Answer 7

• 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

Question 8

control of water

Answer 8

• 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

Question 9

control of salt

Answer 9

• 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

Question 10

thermoregulation

Answer 10

regulation of body temp in an organism

Question 11

ectothermic animals eg

Answer 11

fish, amphibians, reptiles

Question 12

ectothermic animals

Answer 12

• body temperatures vary according to environmental temp

- reptiles use color (dark) and body orientation to regulate body temp

Question 13

endothermic animals

Answer 13

birds, mammals

• constant body temp, irrespective of env temp
• heat produced inside the body via resp

Question 14

why humans need to be 37

Answer 14

optimum temp for enzyme action, too high = denature, too low = inactive

Question 15

heat production in human body

Answer 15

• resp is main source

- heat can be absorbed from environment by consuming warm food/fluid/exposing body to sun

Question 16

adrenalin + thyroxin in heat prod

Answer 16

increased secretion of the two results in inc metabolic rate. resp increases bc of this and more heat is released

Question 17

heat loss in human body

Answer 17

radiation
convection
conduction
evaporation

Question 18

radiation

Answer 18

loss of heat from warm body to cold env via rays + waves

Question 19

convection

Answer 19

distribution of heat in fluids or gas

Question 20

conduction

Answer 20

transfer of heat energy from warm to cold objects that are in contact w each other

Question 21

evaporation

Answer 21

when a fluid absorbs heat energy to convert to a gas

Question 22

two layers of skin

Answer 22

dermis

epidermis

Question 23

epidermis three lyers

Answer 23

cornified, granular, malpighian

Question 24

cornified layer

Answer 24

• outermost layer, dead flattened cells
• contain keratin
• continuously replaced by the underlying tissue

Question 25

keratin functions

Answer 25

protects skin from water, light and infection

Question 26

granular layer

Answer 26

directly under cornified layer and consists of living cells w granules in the cytoplasm

Question 27

malpighian layer

Answer 27

lower layer, consists of living cells that continuously divide to replace cells in upper layers - contains melanin - receives oxygen + nutrients from the dermis

Question 28

melanin

Answer 28

protects skin from UV rays from sun + gives skin color

Question 29

epidermis function

Answer 29

protects underlying tissues

Question 30

dermis

Answer 30

thicker layer than the epidermis and consists of areolar connective tissue

Question 31

dermis contains...

Answer 31

blood + lymph vessels, nerves, sensory organs, hair follicles, tiny erector musc, glands

Question 32

beneath the areolar connective tissue

Answer 32

a layer of adipose (fatty) tissue that connects skin to underlying body parts; serves an insulator

Question 33

blood vessels in d

Answer 33

- transports nutrients in the blood to cells and waste products to sweat glands for excretion - helps w body temp reg

Question 34

lymph vessels in d

Answer 34

drain excess tissue fluid

Question 35

nerves in d

Answer 35

- sensory fibres - conduct impulses from sense organs in skin to CNS - motor fibres - conduct impulses from thalamus to blood vessels in the skin

Question 36

sensory organs

Answer 36

various corpuscles which detect heat, cold pressure, touch and pain

Question 37

hair follicles

Answer 37

- an extension of epidermis, all over body except palms and soles - hair grows from follicle

Question 38

sebum

Answer 38

fatty substance, secreted by sebaceous glands, which helps to prevent dehydration of skin and hair

Question 39

erector muscle

Answer 39

connects base of hair follicle to the epidermis (contracts when it is cold, causes hair to stand up)

Question 40

glands

Answer 40

sebaceous, wax, mammary, sweat

Question 41

wax glands

Answer 41

occur in ext auditory canals of ear and secrete cerumen which prevents insects from entering the auditory canals

Question 42

mammary glands

Answer 42

secrete milk after birth for babies

Question 43

sweat glands

Answer 43

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

Question 44

heat regulation centre

Answer 44

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

Question 45

regulation of body temp on a cold day

Answer 45

- 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