Module 5.1.1 Homeostasis & Communication Flashcards
What is Homeostasis?
Regulation of the internal conditions of a cell/organism to maintain optimum conditions for function in response to internal/external changes
Why is homeostasis important?
the optimum conditions for enzymes & all cell functions are maintained
What are some external changes that could affect a plant?
soil acidity
temperature
humidity
light intensity
wind
predators
what does a cell excrete?
co2
water
urea
What does a cell need to take in?
glucose
oxygen
amino acids
water
Why is coordination needed?
few body systems work in isolation so to keep the organism alive different cells & tissues must communicate with each other e.g. RBC & muscles
What is the internal environment of an animal?
tissue fluid
How does homeostasis occur in the tissue fluid in animals?
the activity of the cell alters its environment so the build up of water acts as a stimulus to trigger the removal of these wastes (substrates are being used up & products are being produced)
What is a tissue?
a group of similar cells that are specialised to work together to carry out a specific function
What is an organ?
a group of similar tissues working together to perform a specific function
why do cells become differentiated?
to perform specific functions & form tissues & organs
Why is a good communication system required?
to ensure all the parts of the body work together effectively
What are the features of a good communication system?
covers the whole organism
enables cells to communicate with each other
specific communication
rapid & slow
short & long term
How does cell signalling help communication?
cell signalling is needed to produce a response so receptors will communicate with effectors & vice versa
Does cell signalling happen over short or long distances?
can occur between nearby cells (e.g. neurotransmitters) & distant cells (hormones)
What is the journey of a stimulus & response
Receptor cells detect a change in the environment and then either a hormone/nerve impulse will send it to be coordinated which will process information from receptors. Hormones/nerve impulses then again send this to the effector (muscle/gland) to produce a response to return to optimum conditions
What is the response like in the nervous system?
rapid & precise
What is the nature of the message in the nervous system?
a nerve impulse (electrical)
What is the action in the nervous system?
carried in nerves to a specific location (e.g. muscle)
What is the response like in the endocrine system?
slower but lasts longer
What is the nature of the message in the endocrine system?
a hormone (chemical)
What is the action in the endocrine system?
carried in the blood to all organs but only affects the target organ -> affects reproduction, development, metabolism, growth & behaviour
What is negative feedback?
A reversal of any change in the internal environment to return to an optimum steady state
What are some examples of negative feedback?
The control of body temperature, blood glucose levels & body water concentration
How does negative feedback work?
A change from the optimum happens which causes the sensory receptors to detect the change. The communication system coordinator informs the effector (muscle/gland) which then reacts to reverse the change. This results in a return to the optimum condition
What is positive feedback?
A process that increases any change that is detected by receptors but doesn’t lead to homeostasis as it doesn’t keep the internal environment constant.
What are some examples of positive feedback?
Blood clotting & dilation of the cervix
How does positive feedback work?
A change from the optimum occurs which causes the sensory receptors to detect the change. The communication system coordinator informs the effector (muscle/gland) which then reacts to increase the change
How do elephants stay cool?
The ears contain blood vessels that vasodilate which then they flap them so the heat travels out of them through radiation
What is an endotherm?
An organism that controls body temperature internally by homeostasis as well as altering behaviour
What are some examples of endotherms?
Bluefin tuna, great white sharks, birds & mammals
What are the advantages of being an endotherm?
A constant body temperature, activity is possible even when the organism is cool & the organism can inhabit cooler parts of the planet
What are the disadvantages of being an endotherm?
Lots of energy is used to maintain a constant body temperature so more food is needed to be consumed (metabolic rate is 5x higher than ectotherms, less energy is therefore used for growth
How is body temperature controlled?
It’s monitored by the hypothalamus in the thermoregulatory centre of the brain which contains thermoreceptors that are sensitive to the temperature of the blood. The skin contains temperature thermoreceptors & sends nervous impulses to the thermoregulatory centre
What are the different layers of the skin & what is in the skin?
Hair
Sebaceous glands
Temperature & pain receptors
The epidermis, dermis & subcutaneous tissue layers
Nerves
Arterioles
Muscle
Fat, collagen & fibroblasts
Sweat glands
Capillaries
What are the different receptors in the skin
Heat, pain, cold, light touch, strong pressure & hair movement
Describe the process of sweating & how does it cool people down?
Sweat glands release liquid sweat evaporates into a gas required by the heat energy taken from the skin. As the skin loses heat, the blood is cooled down below the surface
What is vasodilation and how does it occur?
Capillaries underneath the skin are filled with blood & dilate so the blood is shunted towards the surface & this increased blood flow to the surface of the skin increases the rate that heat is therefore radiated from the body.
Why do hairs lie flat on the surface of the skin & how does it occur?
Erector muscles at each hair relax when it is too hot so hairs lie down close to the surface of the skin. Air is not trapped so there is no insulating layer of air and the body cools
Why do animals pant?
Animals that have few sweat glans cool by increased panting which increases the evaporation of water. Consequently blood in the blood vessels surrounding the mouth & lungs is cooled down
What are the different behavioural adaptations of organisms when they are too hot?
They move into the shade, remain inactive, increase surface area & use water
Why do some organisms get wet when they are too hot?
Water has a higher specific heat capacity than air so it is more efficient at transferring heat so they get cooler faster
What happens when organisms get too cold?
A decrease in body temperature causes the thermoreceptors to detect the change. The hypothalamus sends the impulses to the effectors which responds to increase body temperature
What is shivering & how does it increase body temperature?
Involuntary convulsions of skeletal muscles which produces metabolic heat transferred to the blood passing through the blood vessels under the skin’s surface
How do hormones increase body temperature?
Adrenal & thyroid glands produce adrenaline & thyroxine which increases metabolic rate. The energy then released in respiration is transferred as heat to the blood passing through the tissues
How does hairs on the skin surface ‘standing up’ increase body temperature & how does it happen?
Erector muscles contract & cause hairs on the skin to ‘stand up’ (goosebumps). The hairs then trap a layer of air next to the skin which is then warmed by the body heat and becomes an insulating layer, reducing heat loss by radiation & convection
What is vasoconstriction and how does it increase body temperature?
The arterioles supplying blood to the capillaries underneath the skin constrict and cause them to bypass arterioles to dialate which reduces blood flow from the surface of the skin so less heat can be lost as a result.
What are the different behavioural adaptations of organisms when they are too cold?
They move into the sunlight, move about to generate heat in the muscles & in the extreme cold they may roll into a ball to decrease surface area
