unit 1 AOS 2

Question 1

what is homeostasis

Answer 1

A condition in which the internal environment of the body remains relatively constant despite changes in the external environment

Question 2

what arw the two systems that maintain homeostasis

Answer 2

the nervous system

the endocrine system

Question 3

Why is homeostasis important for sustaining life?

Answer 3

Homeostasis is important because it allows metabolic processes to continue to function. For example, enzymes within cells work best at an optimum temperature

Question 4

what is a stimulus

Answer 4

A change, either an increase or decrease, in the level of an internal variable

Question 5

what is a recpetor

Answer 5

the structure that detects the change and sends signals to the control center

Question 6

what is a control centre

Answer 6

the structure (central nervous system) that evaluates the change against the set point for that variable and sends signals to the effector about the correction needed

Question 7

what is an effector

Answer 7

the structure that adjusts its output to make the required correction

Question 8

what is a response

Answer 8

The corrective action taken agaisnt the stimulus

Question 9

what is a negative feedback loop

Answer 9

a process in which the body senses a change in a variable and activates mechanisms to reverse the change.
keeps the varible in a narrow range

Question 10

what is a postive feedback loop

Answer 10

Positive feedback leads the variable that has increased to increase further, or the variable that has decreased to decrease even more

a cycle of continuing change in which an original change is increasingly amplified

doesnot keep a variable within a narrow range

Question 11

compare negative feedback with postive feedback

Answer 11

negative feedback loop is where the response is opposite in direction to the original stimulus. if the stimulus is an increase in a variable, then the response is a decrease in the same variable.
For example, if the blood glucose level is too high, negative feedback results in it decreasing to normal.

on the other hand, Positive feedback acts to increase the magnitude of a stimulus, moving it further from a set point. for example postive feeback is used in the process of childbirth

Question 12

tempreture feedback undertakes what process

Answer 12

negative feedback process

Question 13

what is the bodys homeostatic tempreature

Answer 13

37.7 degree celsuis

Question 14

what montiors core body tempreture

Answer 14

the hypothalamus and thermoreceptors

Question 15

what is function of the hypothalamus

Answer 15

Acts like a thermostat - registers change in the core body temperature and receives information about changes from the thermoreceptors in the skin.

restores normal body temperature

Question 16

how can body heat be lost

Answer 16

Heat loss can occur by evaporation of excreted water including sweat, from the pores and from the airways and lungs.

through:
convection
conduction
radiation
evaporation

Question 17

what happens when body temp is too high (too hot)

Answer 17

1. activivates heat loss centre in hypothalamus
2. Blood vesicles dilate
3. Sweat glands are activated
4. Body temperature decreases - the hypothalamus heat loss centre shuts off

Question 18

what happens when body temp is too low (too cold)

Answer 18

1. Activates heat promoting centre in the hypothalamus
2. Blood vesicles constrict
3. Thyroid gland releases hormones to increase metabolic rate
4. Rapid contractions of skeletal muscles - causes reflex shivering, which expends energy to generate heat
5. Body temperature increases - the hypothalamus heat promoting centre shuts off

Question 19

what does thyrxoine (T4) do

Answer 19

speeds up metabolic activity in cells
the increase of metabolic activity also results in the production of heat

T4 production is controlled by negative feedback

Question 20

what do the thermoreceptors do

Answer 20

detect changes in body temperature and send messages to the hypothalamus.

Question 21

the importance of glucose

Answer 21

primary source of energy

The body concerts glucose into ATP during cellular respiration

Question 22

control of blood glucose

Answer 22

controlled by negative feedback

involves two hormones: insulin and glucagen

Question 23

what does insulin do

Answer 23

lowers blood glucose levels by…
promoting the uptake of glucose by cells, where it is converted to energy as ATP or stored as glycogen or fat in the liver (for later use)

Question 24

what does glucagon do

Answer 24

increases blood glucose levels by…
promoting the breakdown of glycogen to glucose in the liver. then glucose is released into the bloodstream

Question 25

what happens when blood glucose levels are too high

Answer 25

High blood glucose stimulates beta cells in the liver secrete insulin

Question 26

what happens when blood glucose levels are too low

Answer 26

Low blood glucose stimulates alpha cells in the liver to secrete glucagon Glucagon promotes the breakdown of glycogen to glucose in the liver Glucose is released into the blood

Question 27

what is the process called for regulating water balance

Answer 27

osmoregulation

Question 28

what does the antidiuretic hormone (ADH) do

Answer 28

promotes the reabsorption of water from the kidney and regulates urine volume

Question 29

what does osmoregulation do

Answer 29

sensors in the body that detect changes in water balance away from homeostatic levels. Stimulates the release of the ADH - Osmoreceptors are in the hypothalamus - they monitor blood osmolarity, if its too high or too low it will send messages to the pituitary gland (part of the brain), which will regulate the amount of ADH released

Question 30

what happens when Solute concentration increases above normal range (low water)

Answer 30

Hypothalamus detects increased osmolarity Hypothalamus creates feelings of thirst Hypothalamus sends a message to the posterior gland to release more ADH

Question 31

what happens when Solute concentration falls below normal range (high water)

Answer 31

Hypothalamus detects low osmolarity Pituitary gland release of ADH stops. Less water is reabsorbed from the kidney higher urine output

Question 32

regulation of water balance in plants

Answer 32

Plants rely on water balance for photosynthesis (plants make their own food) and survival Plants respond to a shortage of water by closing their stomata to stop water loss through transpiration

Question 33

what is transpiration in plants

Answer 33

evaporative water loss through plant leaves that results in the movement of water through the plant

Question 34

how is water important for plants

Answer 34

An input for photosynthesis (vital for their survival) A means for cooling plants by evaporation of water from leaves during transpiration

Question 35

how is water loss regulated in plants

Answer 35

Plants have regulatory mechanisms and structural adaptions which maintain water balance

Question 36

what is Regulatory mechanisms

Answer 36

active responses by plants that are because of changes in water balance

Question 37

what is structural adaptions

Answer 37

heritable physical traits (their leaves) that have evolved in plant populations and equip plants to survive and reproduce under their particular environmental conditions

Question 38

controlling wtaer up take in plants

Answer 38

Roots are the plants organs that are specialised for locating and absorbing water Roots supply the water on the input side of the water balance equation in plants when guard cells lose turgor, stomata close, preventing water loss.

Question 39

controlling water loss in plants

Answer 39

- Leaves are the source of water loss from plants Water loss occurs when guard cells are turgid, causing the stomata to open The major loss of water in plants occurs when water vapor is lost by transpiration from the leaf stomata.

Question 40

what is the stomata

Answer 40

pores in leaves * Plants can actively regulate water loss by the opening and closing of their stomata.

Question 41

conditions favouring stomata open

Answer 41

high levels of water and sunlighgt When conditions favor having stomata open, ions move into the guard cells. Water then follows these ions by osmosis into the guard cells. This results in the stomata opening.

Question 42

conditions favouring stomata close

Answer 42

When water levels are low to prevent loss through transpiration. Water and ions move out of the guard cells, causing the guard cells to become flaccid. This results in the stomata closing.

Question 43

what is type 1 diabetes mellitus

Answer 43

a condition in which blood glucose is high, because the body's cells cannot take up glucose in the normal way

Question 44

why do people with diabetes have high blood glucose

Answer 44

In type 1 diabetes, the body's immune system is damaged therefore the pancreas cannot make insulin, leading into high levels of blood glucose in type 1 diabetes, the insulin producing beta cell of the pancreas are destroyed by the immune system, and the pancreas cannot make insulin Patients must have insulin injections to stabilise blood glucose levels

Question 45

what is Hyperthyroidism

Answer 45

in hyperthyroidism, excessive production of thyroid hormones drives up the basal metabolic rate, affecting many functions Hyperthyroidism leads on to graves disease

Question 46

what are some symptoms of Hyperthyroidism

Answer 46

→ Nervousness → Weight loss → Increased heart rate → Brittle hair → Elevated body temperature

Question 47

what is graves disease

Answer 47

Thyroid increases in size

Question 48

Where in the body would you find the receptors detecting an increase in blood glucose levels?

Answer 48

The pancreas OR the beta cells of the pancreas