5.1.1 Communication and Homeostasis Flashcards
What is homeostasis?
-maintenance of a constant internal environment in response to changes in external/internal environment
-involves control systems that keep internal environment roughly constant
How do animals respond to the environment?
- respond to changes in their external environment i.e by avoiding harmful environments
-respond to changes in their internal environment to make sure conditions are optimal for metabolic reactions
Changes to internal environment
-internal body temp
-blood glucose levels
-water levels
-pH
Changes to external environment
-external temp
-humidity
-light(plants)
-harmful stimuli i.e sudden sounds/pain
Why is homeostasis important?
-vital for cells to function normally and stop them being damaged
-allows them to avoid harmful environment / ensure that conditions are optimum for metabolism
Why are receptors and effectors needed?
-restore dynamic equilibrium in response to conditions
-receptors trigger and co-ordinate the correct responses
-info from sensory receptors is transmitted to the brain + impulses are sent along motor neurons to effectors(muscles/glands) that react to bring about change in response to stimulus
Why do multicellular organisms need communication systems?
-organs, cells and tissues have different functions, are found in different parts of the body and may have different roles to one another
-need to communicate
Short paracrine cell signalling
-occurs between cells that are close together i.e neurotransmitters between nerves or muscle cells
Long distance endocrine signalling
-involves signalling over long distances
-signalling molecules are transported in the circulatory system
What is a hormone?
-a chemical messenger, secreted by glands and found in the endocrine system
similarities between the endocrine + nervous system
-both have coordination centres(brain, spinal cord)
-both send signals in the body
-both have receptors to detect stimuli
-both have effectors(muscles/glands) to carry out response
Differences between nervous + endocrine system
-chemical messengers vs nerve impulses
-hormones are longer lasting vs nerves are shorter lasting
-nerves work faster than hormones
What do cell surface receptors do?
-allow cells to recognise the chemicals involved in cell signalling
What is negative feedback?
-control mechanism that elicits response to help restore changed value to norm
-receptors detect when a level is too high/low-}info communicated via nervous/hormonal system –} effectors respond to counteract the change
What happens if the change from normal is too big?
-effectors may not be able to counteract it, i.e a huge drop in body temp caused by prolonged exposure to cold
What is positive feedback?
-amplifies the change away from normal
-not involved in homeostasis because internal environment isn’t constant
-rapidly activates processes in the body i.e platelets forming blood clots
Why is it important to maintain core body temp?
- temp affects enzyme activity and enzymes control the rate of metabolic reactions
How does high body temp have an effect?
-rise in temperature makes the enzyme’s molecules vibrate more
-if temp goes above a certain level, vibration breaks some H bonds in the tertiary structure
-active site changes shape and enzyme + substrate no longer fit together
-enzyme denatures
How does low body temp have an effect?
-enzyme activity / RoR
-enzyme-substrate complexes cannot form
Why does body temp fluctuate throughout the day?
-it is dependent on the external environment
-respiration is an exothermic reaction, so the temp it works at changes
How are temp changes in the body detected?
-the peripheral temp receptors are in the skin + detect changes in the skin surface temp
-temp receptors in the hypothalamus detect temp of blood in the body
What is an ectotherm?
-an animal that cannot control their body temp internally via homeostasis
-instead change their behaviour i.e migration
Sources for ectotherms to regulate temp
-radiation= absorbing thermal energy
-evaporation
-convection= thermal energy transferred with air/liquids
-conduction= transfer of thermal energy through solid surfaces
What are endotherms?
-can control their body temperature internally via homeostasis i.e mammals and birds
Difference in metabolic rate between ectotherms and endotherms
-ectotherms don’t have a constant body temp so their metabolic rate varies
–} more active at higher temps and vice versa
-endotherms can keep internal temp constant so they have a constantly high metabolic rate–} largely independent of external temp
Mechanisms to reduce body temp: vasodilation
-atertioles near the surface of the skin dilate when temp rises
-vessels that provide a direct connection between the arterioles + the venules constrict
-this forces blood through the capillaries in the surface layers of the skin
-more heat is lost from the skin in radiation +temp is lowered
Mechanisms to reduce body temp:
Sweating
-more sweat secreted from sweat glands as core temp increases
-water in sweat evaporates from the surface of the skin + takes heat from the body + cooling the skin
Mechanisms to reduce body temp:
Hairs lie flat
-as temp increases, the erector pilli muscles in the skin relax, causing hairs to lie flat
-avoids trapping an insulating layer of air–} skin is less insulated and heat can be lost more easily
Mechanisms to increase body temp:
vasoconstriction
-arterioles near me surface of the skin constrict–} less blood flows through the capillary networks close to the surface of the skin
-very little radiation takes place–} the warm blood is kept well below the surface to reduce heat loss
Mechanisms to reduce body temp:
Decreased sweating
-less sweat is secreted from sweat glands when it’s cold–} reducing the amount of heat loss
-less evaporation of water from the skin’s surface
