Homeostasis

Question 1

What is homeostasis

Answer 1

Homeostasis is the bodies way of regulating internal factors to keep them constant

Question 2

what is negative feedback

Answer 2

When the body counteracts any internal changes so that it stays at its optimum conditions

Question 3

What is needed for negative feedback

Answer 3

-Sensory receptors (detect
changes in internal
conditions)

-Effectors (provide response)

Question 4

what is positive feedback

Answer 4

opposite of negative feedback (increases change so that the conditions are further from the optimum)

Question 5

What is an ectotherm?

Answer 5

An ectotherm is an organism which regulates its body temperature with the help of external
source

Question 6

What are endotherms?

Answer 6

organisms that control internal temperatures through respiration and are independent of external temperature

Question 7

What are some responses to restore optimum temp

Answer 7

Shivering – contractions of skeletal muscles stimulated by nerve impulses sent out
by the hypothalamus, lead to increase in temperature as heat is released
* Sweat glands – sweat production to decrease body temperature via evaporation
* Hairs on skin – lie flat to minimise insulation and increase heat loss, raised to provide
insulation and reduce heat loss
* Arterioles – dilate to increase heat loss as blood flows closer to skin, constrict to
reduce blood flow and therefore minimise heat loss

Question 8

What are receptors?

Answer 8

receptors detect stimuli

are specific-only detect certain stimulus

some are cells and some are protein

Question 9

What are effectors

Answer 9

cells that bring about a response to a stimulus

Question 10

What is cell signalling

Answer 10

way of communication between cells

can occur between adjacent cells

or distant cells

Question 11

What are the mechanisms that reduce body temp

Answer 11

Sweating

Hairs lie flat

Vasodilation

Question 12

What are the mechanisms that increase body temp

Answer 12

shivering

Much less sweat

Hairs stand up

vasoconstriction

hormones

Question 13

How does sweating reduce body temp

Answer 13

water ins sweat evaporates from surface of skin and takes heat from body. As a result the skin is cooled

Question 14

How does hair lying flat reduce body temp

Answer 14

less air is trapped

skin is less insulated

heat can be lost easily

Question 15

How does vasodilation reduce body temp

Answer 15

arterioles near skin dilate

More blood flows through the capillaries in the surface layer of dermis

more heat loss from skin by radiation

temp is lowered

Question 16

How does shivering increase body temp

Answer 16

Muscles contract in spasms

more heat is produced from increased respiration

Question 17

How does sweating less increase body temp

Answer 17

Less sweat is secreted from sweat glands when its cold

reducing the amount of water evaporated

therefore reducing heat loss

Question 18

How do hairs standing up increase body temp

Answer 18

erector pili muscles contract when it is cold

makes hairs stand up

this creates insulating layer

that traps more air so reduces heat loss

Question 19

How does vasoconstriction increase body temp

Answer 19

Arterioles constrict

less blood flows through capillaries

less heat loss

Question 20

What happens when body temp increases from the optimum (37)

Answer 20

Thermoreceptors detect temp change

hypothalamus sends signals to effectors

-sweating
-hairs lie flat
-vasodilation
-etc.

More heat lot and less heat produced by body

Question 21

How does a beta cell release insulin

Answer 21

When blood glucose conc is high

glucose enters Beta cells via facilitated diffusion

rate of respiration increases making more ATP

causes potassium ion channels to close

potassium builds up inside the cell

plasma membrane of beta cell is depolarised

ca channels open

vesicles fuse with beta cell memrbane t release insulin