human bio validation - body temp, water balance, breathing

Question 1

define thermoregulation

Answer 1

Maintaining the balance between heat production and heat loss

Constancy of body temperature is important for chemical reactions in cells to occur, as they are heat-sensitive

37˚ is optimum for cellular reactions

Heat produced at metabolic activity helps maintain this higher level

Question 2

what is convection

Answer 2

Flow of air or currents can transfer heat

Question 3

what is conduction

Answer 3

Transfer of heat from one object to another through physical contact

Question 4

what is radiation

Answer 4

Transfer of heat from one object to another without physical contact

Question 5

what is evaporation

Answer 5

The conversion of a liquid to a gas

Question 6

what are thermoreceptors

Answer 6

temperature receptors

Central thermoreceptors: located in hypothalamus – detect body temperature

Peripheral thermoreceptors: located in the skin and some mucous membranes – detect outside temperatures
- Cold receptors: stimulated by environmental
temperatures lower than normal
 Heat receptors: detect temperatures higher than normal

All are connected to the hypothalamus

Nerve impulses sent out by the hypothalamus help increase of decrease heat loss

Question 7

explain the role of skin in thermoregulation

Answer 7

The diameter of arterioles to the skin is controlled by autonomic nerves, which can act to increase or decrease flow of blood to the surface

This thereby increases or decreases rate of heat loss (through radiation)

When large amounts of body heat must be lost and skin blood vessels are already at maximum dilation, sweating must occur

The production and transport of sweat to eh skin surface is stimulated by sympathetic nerves

Evaporation of sweat from the skin has a cooling effect: heat is removed from the skin when liquid sweat changes into vapour

Cooling of the skin results in cooling of the blood flowing through the skin

Question 8

list some physiological responses of the body to prevent body temperature from falling

Answer 8

vasoconstriction of arterioles in the skin

shivering

piloerection

stimulation of adrenal medulla

increased production of thyroxine

Question 9

explain how vasoconstriction of arterioles in the skin prevents heat loss

Answer 9

Impulses from he hypothalamus stimulate sympathetic nerves that cause blood vessels in the skin to constrict

blood is directed to internal organs to prevent heat loss from them

The skin becomes cooler because there is less warm blood flowing through it

Less heat will then be lost from body surface

Question 10

explain how shivering prevents heat loss

Answer 10

A fall in body temp will cause the hypothalamus to send stimuli to the parts of the brain that increase skeletal muscle tone

These tremors are known as shivering and can increase body heat and production

Question 11

explain how piloerection prevents heat loss

Answer 11

the contraction of piloerector muscles under the skin causes hair to stand on end, trapping an insulating layer of air

this help prevent radiation heat loss

this is relatively ineffective in humans due to lack of body hair

Question 12

explain how stimulation of the adrenal medulla prevents heat loss

Answer 12

adrenal medulla i stimulates by sympathetic nerves

medulla secretes adrenaline and noradrenaline into the blood

hormones bring about an increase in cellular metabolism that leads to an increase in heat production

Question 13

explain how the increased production of thyroxine prevents heat loss

Answer 13

increased production of thyroxine decreases metabolic rate

this response is slower but long lasting

the small change in metabolic rate that occurs between summer and winter is a result of this

Question 14

list some psychological/behavioural responses to preventing heat loss

Answer 14

putting on an extra jumper

sheltering from a cold wind

turning on a heater

reducing surface area of body

Question 15

list and explain some physiological responses to prevent body temperature from rising

Answer 15

vasodilation of arterioles in the skin
- increases blood flow through the skin
- skin becomes reddish in colour, surface temperature
rises and there is a greater heat loss through radiation
and convection

sweating
  -  above environmental temperatures of 28˚ sweating is 
     needed to increase heat loss
  -  occurs through evaporation
     only effective in dry environments

decreased production of thyroxine (decreasing metabolic rate)

Question 16

list some behavioural/psychological responses to prevent body temperature from rising

Answer 16

turning on a fan/air conditioner

removing external clothing

reducing physical activity

increase body surface area

Question 17

what is heatstroke

Answer 17

when body temperature rises and the regulatory mechanisms cease. This can be fatal is brain cells are affected

Question 18

what is heat exhaustion

Answer 18

occurs as a result of extreme sweating and vasodilation to heat loss

The loss of water in sweating reduces the volume of blood plasma and vasodilation reduces resistance to blood flow

Blood pressure decreases and heart output of blood decreases.

the person may collapse even if they have normal body temperature

Question 19

what is hypothermia

Answer 19

occurs if a person’s core temperature falls below 33˚, the metabolic rate is so low that heat production is unable to replace heat loss and body temperature continues to fall

Question 20

how is water loss controlled by the kidneys

Answer 20

1. A decreased amount of water in the blood results in decreased concentration of the blood plasma to decrease. This means that the osmotic pressure of the blood is raised
2. Osmoreceptors in the hypothalamus detect the increases osmotic pressure of the blood
3. The hypothalamus stimulates the posterior globe of the pituitary gland to release ADH into the bloodstream
4. ADH is carries all over the body by the blood but it affects its target organs which are the nephron tubules. The permeability to water of the distal convoluted tubules and collecting ducts is increased
5. More water is reabsorbed into the blood plasma from the tubules and ducts
6. The reabsorption of water increases the water concentration in the plasma so that the osmotic pressure of the blood is decreased
7. The response has decreased osmotic pressure of the blood. This has eliminated/reduced the original stimulus that was increasing osmotic pressure of the plasma. Negative feedback has occurred.

Question 21

how does the body restore water intake

Answer 21

1. osmotic pressure is increased
2. Osmoreceptors in a thirst centre in the hypothalamus detect high osmotic concentration in blood – other stimuli such as dry mouth are involved
3. Stimulation of thirst centre makes person feel thirsty
4. Conscious feeling of thirst stimulates a person to drink
5. Fluid consumed is absorbed into plasma from alimentary canal
6. As fluid circulates through body it enables intercellular and intracellular fluid to return to proper osmotic concentrations
7. After drinking, thirst is no longer stimulated and desire to take in water ceases. This is a negative feedback loop.

Question 22

explain how antidiuretic hormone (ADH) controls water loss

Answer 22

ADH is produced by the hypothalamus and released from the posterior lobe of the pituitary

ADH increases the permeability of the walls of the distal convoluted tubule and collecting duct

This reduced the volume of water in the filtrate and increase the concentration of the materials remaining

Conversely, when the concentration of ADH in the plasma is low, the tubules are not very permeable to water, and little water is reabsorbed into the plasma of the blood

Question 23

explain how water is lost from the body

Answer 23

Water loss is continually lost from the body in sweat, urine, faeces and exhaled breath

During strenuous activity water loss can be high

As water is lost from blood, plasma becomes concentrated  lower water content therefore higher osmotic pressure

Water moves from intercellular fluid into plasma by osmosis

Now intercellular fluid is concentrated and water diffuses out of the cells, so cells shrink from dehydration