communication and homeostasis Flashcards
(28 cards)
what is the need for communication systems?
-to respond to changes in organsim’s internal and external environment
-to coordinate the activities of their different organs
-to function properly and efficiently, and ensure their internal conditions are kept relatively constant
-physiological control systems maintain the internal environment within restricted limits through homeostasis
-Homeostasis ensures the maintenance of optimal conditions for enzyme action and cell function
examples of physiological factors that are controlled by homeostasis in mammals?
-Core body temperature
-Metabolic waste (eg. carbon dioxide and urea)
-Blood pH
-Concentration of glucose in the blood
-Water potential of the blood
-Concentration of respiratory gases (carbon dioxide and oxygen) in the blood
what do homeostatic mechanisms in mammals require?
what are the two communication systems that do this?
-information to be transferred between different parts of the body
•The nervous system
-info sent as nerve impulses
-coordinate sensory receptors, decision making centres and effectors
-a nerve is a bundle of neurones
•The endocrine system
-hormones are chemicals which transmit information from one part of the organism to another and bring about a change
-they alter the activity of one or more specific target organs
-hormones are used to control functions that do not need instant responses
what are the 3 key internal body conditions that need to be controlled?
-temperature (thermoregulation)
-pH
-blood glucose concentration
what happens if the pH is too high?
-enzymes are denatured at extremes of pH
-Hydrogen and ionic bonds hold the tertiary structure of the protein together
-Below and above the optimum pH of an enzyme, solutions with an excess of H+ ions (acidic solutions) and OH– ions (alkaline solutions) can cause these bonds to break
-This alters the shape of the active site, which means enzyme-substrate complexes form less easily
-Eventually, enzyme-substrate complexes can no longer form at all
-At this point, complete denaturation of the enzyme has occurred
what happens if there is a change in blood glucose concentration?
-The amount of glucose present in the blood affects the water potential of the blood and the availability of respiratory substrate for cells
-The normal glucose concentration for human blood is roughly 90mg per 100cm3
-A sufficient amount of circulating glucose is essential for cellular respiration
-Brain cells can become rapidly damaged or die if they do not receive a sufficient supply of glucose
-if the blood glucose concentration is too high then it will have an effect on the water potential of the blood
how is homeostasis carried out in plants?
-eg. mesophyll cells in leaves require a constant supply of carbon dioxide for photosynthesis
-guard cells control the diffusion of gases in and out of leaves
-this means stomata control the entry of carbon dioxide into leaves
what is negative feedback?
what does a negative feedback control loop involve?
-maintain homeostatic balance
-A receptor = to detect a stimulus that is involved with a condition / physiological factor
-A coordination system (nervous system and endocrine system) = to transfer information between different parts of the body
-An effector (muscles and glands) = to carry out a response
what is the outcome of a negative feedback loop?
-The stimulus is continuously monitored
-If there is an increase in the stimulus, the body responds to make the stimulus decrease
-If there is a decrease in the stimulus, the body responds to make the stimulus increase
what happens in positive feedback loops?
so what is positive feedback?
-the original stimulus produces a response that causes the factor to deviate even more from the normal range
-the enhancement of the effect of the original stimulus
what is cell signalling?
why is it important?
-cells communicate with each other
-it allows multicellular organisms to control and coordinate their bodies and to respond to their environments
what are the stages of cell signalling?
-A stimulus is received by a receptor cell
-The stimulus is converted to a signal
that can be passed on = transduction
-The signal is transmitted to a target cell (effector) that can detect it (via receptors in its cell membrane)
-An appropriate response is made
in animals, how can cell signalling be categorised?
into two types:
•Paracrine signalling = signalling between cells that are close together
Endocrine signalling = signalling between cells that are far apart = which involves the hormones being transported in the circulatory system
what is thermoregulation?
-thermoregulation is the control of internal body temperature
how do endotherms detect external temperatures?
-physiological mechanisms
-via peripheral receptors =thermoreceptors found in the skin and mucous membranes
-Receptors detect heat and cold
-Impulses are sent from the receptors to the hypothalamus
-The hypothalamus contains receptors that monitor the temperature of the blood flowing through it
-Information from the receptors is processed by the hypothalamus = which then initiates homeostatic responses when temperature gets too high or too low
endotherm responses to high body temp-
vasodilation?
-muscles in the walls of arterioles relax
-causing dilation and allowing more blood to flow into skin capillaries
-Heat is lost to the environment by radiation
endotherm responses to high body temp-
sweating?
BUT?
-Sweat is secreted by sweat glands in the skin
-This cools the skin by evaporation
-Heat energy from the body is used to convert liquid water into water vapour
-Sweating is less effective as a cooling mechanism in humid environments = there is a reduced water vapour concentration gradient between the skin and the air
endotherm responses to high body temp-
flattening of hairs?
-The hair erector muscles in the skin relax
-causing hairs to lie flat
-This stops them from forming an insulating layer of air
-allows air to circulate over skin, removing heat lost by radiation
endotherm responses to low body temp-
vasoconstriction?
-muscles in arteriole walls contract
-causing the arterioles near the skin to constrict and allowing less blood to flow through skin capillaries
-the blood is diverted through shunt vessels, which are deeper in the skin and therefore do not lose heat to the environment
-Heat loss by radiation at the skin surface is reduced
endotherm responses to low body temp-
increased metabolic rate?
-Most of the metabolic reactions in the body are exothermic and this provides warmth to the body
-In cold environments the hormone thyroxine increases the basal metabolic rate (BMR), increasing heat production in the body
-Thyroxine is released by the thyroid gland
endotherm responses to low body temp-
shivering?
-Muscles contract and relax repeatedly in quick succession
-The metabolic reactions required to power this muscle contraction releases heat energy to warm the blood and raise the core body temperature
endoderm responses to low body temp-
erection of hairs?
-The hair erector muscles in the skin contract
-causing hairs to stand on end
-This traps an insulating layer of air over the skin’s surface
-reducing heat loss by radiation
what are ectotherms?
-Ectotherms do not have the ability to respond to temperature changes via internal temperature regulation mechanisms
-so they use behavioural mechanisms
what do ectotherms do to warm up?
-seek out the sun or warmer surfaces and ‘bask’ in these locations as they warm until their body temperature has been increased sufficiently
-huddle together to retain heat that may have been gained from the sun earlier in the day
