5.3 & 5.4 Homeostatic Mechanisms in Humans Flashcards
What is conduction? Give an example:
The transfer of heat energy from a hotter object to a cooler object with which it is in contact.
Eg. Touching ice
What is convection?
The transfer of heat by means of warmed air or water rising and being replaced by cooler air or water.
What is radiation?
The transfer of heat from a hot object to the atmosphere by means of infra-red waves.
What is evaporation?
When a liquid becomes a gas as a result of heat.
List the 2 sources of body heat?
- Ectotherms
- Endotherms
What do ectotherms rely on? Give an example:
Rely on the external environment for heat.
Eg. Smoke
What do endotherms produce? Give an example:
Produce heat through their metabolism.
Eg. Humans, other mammals
What is vasoconstriction?
The constriction of blood vessels in the skin which reduces heat loss from the skin as the amount of blood moving close to the exposed surface is reduced.
What is piloerection (goosebumps)?
The contraction of blood vessels and small muscles that pull the hairs on the skin upright, trapping a layer of air. In animals with thick fur, this reduces heat loss from the body.
What are 4 things we can do to stay warm?
- Seek shelter
- Decrease our surface area by curling up
- Putting on more clothes
- Moving around
What is shivering thermogenesis?
An involuntary movement of the muscles which generates large amounts of heat, stimulated by adrenaline.
What is non-shivering thermogenesis?
Increased cellular activity in brown fat which is a tissue specialised for heat production.
What is the Thyrotropin-releasing hormone?
Is secreted by the hypothalamus and acts on the anterior pituitary to secrete the Thyroid stimulating hormone.
What is the Thyrotropin-stimulating hormone?
Acts on the thyroid gland to release T3 and T4 hormones which increase cellular respiration
Describe the process of sweating:
- Sweat is produced by sweat glands
- Body heat is used to evaporate sweat from the skin
- Changing state from liquid gas uses heat energy and thus cools the surface of the skin
What is the vasodilation of blood vessels?
When the blood vessels move closer to the surface of the skin to increase heat loss.
What are 3 ways you can cool down when it’s hot?
- Slowing the rate of cellular respiration in internal organs by decreasing activity
- Finding shade
- Increasing your surface area by standing with your arms and legs outstretched
Describe how exposure to wind cools the body:
The wind pushes heat away from the skin
What is glucose stored as in the liver?
Glycogen
What happens when blood glucose levels fall? Give an example of when this could happen:
The body breaks down glycogen into glucose for cellular respiration.
Eg. When a person hasn’t eaten in a while
What happens when blood glucose levels rise? Give an example of when this could happen:
The body stores glucose as glycogen.
Eg. After eating food
What happens when blood glucose levels deviate from the acceptable range?
Cells in the pancreas respond by releasing hormones; Either insulin (which stores glucose), or glycogen (which releases it).
What is osmoregulation?
The maintenance of water balance to control salt concentrations.
What happens when we drink a lot of water?
There will be too much water in the blood, the kidneys will then produce a lot of very dilute urine to get rid of the extra.
What happens when the body is short of water?
The kidneys will produce only a very small amount of concentrated urine.
What are osmoreceptors?
Are located in the hypothalamus and are sensitive to blood solute concentrations.
What are baroreceptors?
Located in the atria of the heart where they detect changes in blood pressure.
What is the negative feedback mechanism in the regulation of water?
Controls the amount of Anit-Diuretic Hormone (ADH) is produced.
List 3 factors which inhibit ADH release:
- High water concentration in the blood
- Low salt concentration in the blood
- Alcohol
List 2 results of low ADH:
- Decreases water reabsorption
- Urine output increase
List 2 results of high ADH:
- Increases water reabsorption
- Urine output decrease
What are the groups of diseases of the endocrine system?
- Hypersecretion (oversupply of hormones)
- Hyposecretion (undersupply of hormones)
- Cancers of endocrine glands
