Homeostasis

Question 1

Define the term homeostasis

Answer 1

Homeostasis is the maintenance of a stable internal environment in a controlled condition.

Question 2

Describe the components of a feedback system.

Answer 2

A feedback loop is a system used to control the level of a variable in which there is:
- An identifiable receptor (sensor)
- A control centre (integrator or comparator),
- Effectors, and methods of communication.

Question 3

What is a positive feedback system?

Answer 3

A feedback loop that reinforces a changed variable in a controlled environment.

Question 4

What is a negative feedback system?

Answer 4

Negative feedback is the action taken by the body to return something to a normal/optimum level following a deviation from the optimum level.

Question 5

Give an example of a positive feedback system.

Answer 5

When an infant suckles on the breasts of the mother, a chemical called prolactin gets released, which increases milk production. More suckling leads to more prolactin release, which promotes more milk production. When the child is no longer hungry and stops breastfeeding, prolactin stops getting released and as a result, milk production also stops.

Question 6

What are the 4 principal routes of heat loss from the body to the environment?

Answer 6

Radiation

Conduction

Convection

Evaporation

Question 7

Explain radiation in heat loss.

Answer 7

Heat travelling through air.

Question 8

Explain Conduction in heat loss.

Answer 8

Exchanging heat through touch.

Question 9

Explain Convection in heat loss.

Answer 9

The upward movement of heat.

Question 10

Explain Evaporation in heat loss.

Answer 10

Evaporation is the process of losing heat by converting water to gas (evaporation of sweat).

Question 11

2.1 Compare and contrast different methods of measuring body temperature (oral, axillary, tympanic and rectal)

Answer 11

Rectal= 36.6°C to 38°C
Ear = 35.8°C to 38°C
Oral = 35.5°C to 37.5°C
Axillary = 34.7°C to 37.3°C

Question 12

2.2 State the normal body temperature range, distinguishing between peripheral and core temperatures and identifying the cyclic variations in normal temperature.

Answer 12

In a cold environment, thermoregulators send signals to the hypothalamus, which, during effector changes, will send the heat to the core, whereas less heat will go to the peripheral.

Cyclic variations of a healthy body vary by about 0.5 °C.

Question 13

Discuss the ways the body can gain heat.

Answer 13

Shivering (Radiation)

Vasoconstriction (Radiation and Conduction)

Behavioural such as heating and clothes (Radiation and Conduction)

Question 14

Discuss the ways the body can lose heat.

Answer 14

Perspiration. (Evaporation)

Vasodilation. (Radiation and Conduction)

Behavioural, such as opening a window or sitting in front of a fan (Convection)

Question 15

Discuss the role of the hypothalamus in the regulation of temperature.

Answer 15

Internal body regulator (control centre) that regulates the normal (37c) temperature of the body.

Question 16

Describe the negative feedback system of the temperature parameter when it is low.

Answer 16

1. Body temperature is low.
2. Thermoreceptors in the hypothalamus stimulate heat-producing mechanisms.

3a. Superficial arteries are constricted, reducing heat loss to the air. Blood flow to the digestive system decreases.
3b. Shivering increases aerobic respiration in the muscles in releasing heat.
3c. Thyroid stimulates cells to increase metabolic heat production.

4. Body temperature increases.

Question 17

Describe the negative feedback system of the temperature parameter when it is high.

Answer 17

1. Body temperature is high
2. Thermoreceptors in the hypothalamus stimulate heat-releasing mechanisms.

3a. Superficial arteries are dilated, causing flushing and increasing heat loss to the air. Blood flow is not diverted away from the digestive system.
3b. Sweat initiated in the skin.
3c. Thyroid stimulates cells to decrease metabolic heat production.

4. Body temperature decreases.

Question 18

Describe the negative feedback system of the blood pressure parameter when it is low.

Answer 18

Baroreceptors will detect the low blood pressure, sending nerve impulses to the medulla oblongata (brain), which will send nerve impulses to the heart to increase its rate and the blood vessels to constrict, then returning to homeostasis.

Question 19

Describe the negative feedback system of the blood pressure parameter when it is high.

Answer 19

Baroreceptors will detect the high blood pressure, sending nerve impulses to the medulla oblongata (brain), which will send nerve impulses to the heart to decrease its rate and the blood vessels to dilate, then returning to homeostasis.

Question 20

Describe the negative feedback system of the parameter of fluid balance with fluids with ADH

Answer 20

Osmoreceptors > hypothalamus

Question 21

Describe the negative feedback system of the parameter of fluid balance with fluids with Aldosterone.

Answer 21

Osmoreceptors detects sending signals to the adrenal cortex

Question 22

Describe the negative feedback system of the parameter of blood glucose concentration.

Answer 22

Question 23

Describe the oral method of measuring body temperature.

Answer 23

A glass thermometer placed under the tongue + the lips closed around the probe
- wait 3-5 mins before taking the probe out

Question 24

Describe the axillary method of measuring body temperature

Answer 24

• place the tip of thermometer in centre of the armpit
• tuck patient’s arm closely against their body
• leave thermometer for 1 min

Question 25

Describe the tympanic method of measuring body temperature.

Answer 25

- insert the probe into the auditory canal - thermometer probe scans + after a few seconds records the amount of infrared energy emitted by the tympanic membrane

Question 26

Describe the rectal method of measuring body temperature.

Answer 26

- lubricated blunt-tipped glass thermometer inserted 4-5 cm into the anal canal at 20-degree angle from horizontal - hold for 3 mins - used for children + patients who cannot / will not cooperate fully

Question 27

What is the normal range of body temperature? (peripheral + core)

Answer 27

Core = 37 degree celcius Peripheral = 1-6 degrees lower than core temp

Question 28

Identify the cyclic variations in normal temperature.

Answer 28

- circadian temperature rhythm - the lowest body temp occurs at around 4am - the highest body temp occurs at around 6pm

Question 29

Discuss the importance of regulating basal metabolic rate (BMR) in the control of temperature.

Answer 29

- the rate at which heat is produced = metabolic rate (measurement = BMR) - it helps to regulate body temperature when the environmental temp changes - e.g when the environment temp increases, the metabolic rate in the body decreases

Question 30

The adrenal medulla responds only to what?

Answer 30

The adrenal medulla responds only to neural stimuli and not adrenocorticotrophic hormone (ACTH)