Homeostasis

Question 1

What makes up the internal environment

Answer 1

extracellular such as fluids tissue fluid and blood

Question 2

what is homeostasis

Answer 2

the process of maintaining the internal environment in a constant optimal state
it is the ability of an individual to return to a set point/norm

Question 3

Explain the regulation of Carbon Dioxide levels in the internal environment
8 steps

Answer 3

1. CO2 levels in the blood increase above normal levels
2. Receptor cells in the carotid artery of the neck are stimulated
3. To send impulses to the medulla oblongata in the brain
4. The respiratory centre of the Medulla oblongata stimulates breathing muscles (i.e. intercostal muscles and diaphragm) and heart
5. Breathing muscles contract more actively resulting in increased rate and depth of breathing while the heart beats faster
6. More CO2 is taken to the lungs to be exhaled
7. CO2 levels in the blood return to normal
8. Stimulation of the receptor cells is inhibited

Question 4

Why does excess carbon dioxide pose a problem

Answer 4

a higher concentration of CO2 results in an increased amount of carbonic acid which lowers the pH levels of body fluids making it more acidic than the set point
enzymes cant function if there is a change in pH therefor excess CO2 must be eliminated.

Question 5

Explain the regulation of water balance in the internal environment (osmoregulation)when the blood has less water than normal.
eight step process

Answer 5

1. Blood has less water than normal
2. The hypothalamus is stimulated
3. and sends impulses to the pituitary gland to secrete more ADH
4. ADH travels in the blood to the kidneys
5. ADH increases the permeability of the collecting ducts and the distal convoluted tubules of the kidney
6. More water is re-absorbed and passed to the surrounding blood vessels
7. the water level in the blood returns to normal
8. the stimulus of the hypothalamus is stopped

Question 6

Explain the regulation of water balance in the internal environment (osmoregulation)when the blood has more water than normal.
eight step process

Answer 6

1. Blood has more water than normal
2. The hypothalamus is stimulated
3. and sends impulses to the pituitary gland to stop secreting ADH/secrete less ADH
4. No ADH/less ADH travels in the blood to the kidneys
5. The collecting ducts and the distal convoluted tubules of the kidney become less permeable to water
6. Less water is re-absorbed and passed to the surrounding blood vessels. More water is now lost
7. The water level in the blood returns to normal.
8. Stimulation of the hypothalamus is stopped.

Question 7

Explain the regulation of salt balance in the internal environment when salt levels in the blood have decreased
eight steps

Answer 7

1. Salt level in the blood decreases
2. Receptor cells in the afferent and efferent arterioles of the kidney detect the low salt level
3. The adrenal gland is stimulated
4. into secreting more aldosterone
5. Aldosterone increases the re-absorption of sodium ions from the renal tubules in the kidney into the surrounding blood vessels
6. The salt level in the blood vessels increases
7. and returns to normal
8. The adrenal gland stops secretion of aldosterone

Question 8

Explain the regulation of salt balance in the internal environment when salt levels in the blood have increased
eight steps

Answer 8

1. Salt level increases
2. Receptor cells in the afferent and efferent arterioles of the kidney detect the high salt level
3. The adrenal gland is simulated
4. To stop secreting aldosterone /secrete less
5. this decreases the re-absorption of sodium ions from the renal tubules in the kidney into the surrounding blood vessels
6. The salt level in the blood vessels decreases
7. and returns to normal
8. stimulation of the adrenal gland stops

Question 9

Explain regulation of thyroxin in the internal environment (blood)
five steps

Answer 9

Done by a negative feedback system
1. the pituitary gland detects a decreased level of thyroxin in the blood
2 so it secrets more TSH
3. The TSH stimulates the thyroid to secrete more thyroxin
4. returning its level to normal
5.The higher level of thyroxin inhibits further secretion of TSH from the pituitary.

Question 10

what disorders are caused by an imbalance in levels of

thyroxin and blood glucose(2)

Answer 10

thyroxin- Goitre

blood glucose- diabetes mellitus

Question 11

What is thermoregulation

Answer 11

the maintenance of a constant body temperature by balancing heat production (thermogenesis) with heat loss (thermolysis)

Question 12

What does maintaining an optimum body temperature enable

Answer 12

1. body optimum temperature is 37 C for functioning of enzymes. Enzymes denature at 42+C
2. enables endotherms to be active in both hot and cold temperatures

Question 13

What are endotherms

Answer 13

(all mammals, birds and humans)

they obtain their heat from cellular respiration inside their body

Question 14

How is heat lost from the body and elaborate on all 4 ways

Answer 14

1. Radiation
   transfer heat from warm body to cooler environment

2.Conduction
transfer heat from hotter to cooler object

3.Convection
replacing of warm rising air by cooler air

4.Evaporation
loss of heat by using body heat to change sweat into water vapor

Question 15

name the layers of the skin(3)

Answer 15

epidermis, dermis and subcutaneouse fat layer

Question 16

name all the sensory receptors and where they are found (2)

Answer 16

Ruffini corpuscle and Krause corpuscle

found in upper dermis

Question 17

what are the sweat glands surrounded by

Answer 17

capillaries

Question 18

How is the skin adapted to regulate body temperature

Answer 18

1. sweating
2. vasoconstriction
3. vasodilation

Question 19

how has the skin adapted to regulate body temperature

Answer 19

1. the skin has thermo-receptors which are sensitive to environmental changes i.e. Ruffini detects increase and Krause detects a decrease
2. skin is richly supplied with blood vessels that can increase/decrease the blood flow to the skin by vasoconstriction and vasodilation
3. The skin has seat glands that can regulate the amount of sweat secreted

Question 20

Which layer is not part of the skin but is important in heat retention

Answer 20

The subcutaneous layer of fat

because fat is a poor conductor of heat, this layer insulates the body against heat loss.

Question 21

what role does they hypothalamus play in thermoregulation, specifically when its cold

Answer 21

the hypothalamus is the temperature regulating centre of the body as it constantly monitors the temperature of the blood flowing through it

• In cold temperatures the environmental/body temperature will drop below 37C
• They hypothalamus will get stimulated by
  1. decrease in blood pressure
  2. impulses from Krause corpuscles in skin registering the cold climate
  3. The hypothalamus responds by taking control measures to prevent heat loss.

Question 22

what control measures are taken by the hypothalamus when there are cold temperatures
(where are impulses sent and what happens)

Answer 22

sends impulses to the
1. dermal arterioles resulting in the contraction of circular muscles to limit the flow off blood to the capillary loops (Vasoconstriction)
blood diverted into shunt vessels in deeper subcutaneous layers instead of being carried to surface in order to prevent heat loss

2.sweat glands receive less blood due to vasoconstriction which decreases sweat secretion therefor preventing heat lost through evaporation

Question 23

Explain hypothermia

Answer 23

a drop in body temperature below 35C as a result of prolonged uncontrolled exposure to cold which impairs brain activity + could lead to a coma/cardiac arrest and or death

Question 24

Explain the role of the hypothalamus specifically in controlling of temperature when it is hot

Answer 24

Heat-loss centre in hypothalamus stimulated by

1. increased blood temperature
2. impulses from Ruffini corpuscles in skin (heat sensitive receptors)
3. Hypothalamus takes control measure to promote loss of heat

Question 25

what control measures are taken by the hypothalamus when there are hot temperatures

Answer 25

Impulses are sent to the
1. dermal arterioles. Motor impulses are inhibited which allows the circular muscles of the dermal arterioles to relax. This allows large volumes of blood to flow to capillary loops in skin (vasodilation)
heat in the blood can now be lost through the epidermis via radiation but also conduction and convection.

2. sweat glands receive more blood, due to vasodilation, causing increased sweating. Sweat evaporation cools the body. Humid conditions slows evaporation that is why heat loss through evaporation is better in drier climates.

Question 26

what factors affect the rate of evaporation

Answer 26

1. environmental temperature, higher=quicker evaporation
2. air movement, more wind= more space for water vapour which speeds up evaporation
3. humidity of surrounding air, lower humid=more rapid the evaporation and subsequent cooling is

Question 27

What is hyperthermia

Answer 27

overheating of the body due to the homeostatic, thermoregulatory system not functioning properly
advanced state: heat stroke