Communication And Homeostasis Flashcards
What is a stimulus?
An environmental change
What is a response?
The way in which the organism changes its behaviour or physiology
Give an example of a slow environmental change?
Arctic fox- thicker white coat in winter
Thinner grey brown coat in summer
Example of quick environmental change?
Appearance of a predator
What is the environment of our cells?
Tissue fluid
What happens when cells undergo metabolic activities?
They use up substrate and create new products- that may be unwanted or toxic
Give an example of a waste product and it’s affect on the body?
Carbon dioxide
If it builds up in the tissue fluid, it’ll alter the ph of the tissue fluid and disrupt action of enzymes.
What is the response of the reduced ph of the blood?
Greater breathing activity to expel the carbon dioxide
Factors of a good communication system?
Cover whole body Enable cell signalling Enable specific communication Enable rapid communication Enable both short and long term responses
What are the two major systems of communication that work by cell signalling?
Neuronal system
Hormonal system
Features of neuronal system?
Interconnected network of neurones that signal across synapses.
Can conduct a signal quickly and enable rapid responses
Features of hormonal system?
Uses blood to transport signals
Transported through the body but only recognised by specific target cells.
Enables longer term responses
Definition of homeostasis?
Maintaining a constant internal environment despite changes in external and internal factors.
Definition of effector?
A cell, tissue or organ that brings about a response.
Eg- liver or muscle cells
Aspects maintained by homeostasis?
Body temperature Blood glucose concentration Blood salt concentration Blood water potential Blood pressure Carbon dioxide concentration
Order of response pathway
Stimulus Receptor Communication pathway Effector Response
Definition of sensory receptors?
Cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials.
What is the input?
Message or signal sent from the receptor to the coordination centre.
What is the output?
Message sent from coordination centre to the effector
Definition of negative feedback?
The mechanism that reverses a change, bringing the system back to optimum.
Flow diagram of negative feedback:
Optimum condition Change away from optimum Receptor detects change Communication system informs effector Effector reacts to reverse change Return to optimum
Example of negative feedback?
Internal temperature increases above optimum
What part of the brain detects temperature change?
Thermoregulatory centre in hypothalamus
Definition of positive feedback?
The mechanism that increases a change taking the system further away from optimum.
Example of positive feedback?
The release of oxytocin during contractions to increase dilation of the cervix further.
Definition of endotherm?
An organism that uses heat from metabolic reactions to maintain body temperature
Definition of ectotherms?
An organism that relies on external sources of heat to maintain body temperature.
How ectotherms try to absorb more heat?
Move into sunny area
Lie on warm surface
Expose larger surface area to sun
How do ectotherms cool down?
Move out of sun
Move underground
Reduce surface area exposed to sun
How to snakes absorb heat?
Basks in sun- absorbs heat directly from sun
How do locusts absorb heat?
Sit side on to the sun exposing a large surface area.
How do locusts absorb less heat?
Cline to top of plant to avoid soil surface as it is hot and radiates heat.
How do locusts cool down?
Increases breathing rate and depth of breathing to evaporate water from the tracheal system
How does a lizard control temperature?
Hides in a burrow during hottest and coldest times. Underground burrows tend to have a stable temperature
How does a horned lizard control its temperature?
Can expand its rib-cage to expose the surface area exposed to the sun so more heat can be absorbed
Advantages of ectotherms?
Less food is used in respiration- more can be converted to growth
They need to find food is smaller and they can survive longer without food.
Disadvantages of ectotherms?
Less active in cool temperatures
At risk from predators when it’s cold and cannot take advantage of food.
What is the hypothalamus?
Part of the brain that coordinates homeostatic responses
What are exergonic reactions?
Reactions that release energy in the form of heat
Responses when too hot?
Sweat glands secrete Hairs lie flat Vasodilation of arterioles and pre capillary sphincters. Panting Less respiration takes place Fewer skeletal muscle contractions
How does sweating cool you down?
Sweat glands secrete fluid onto skins surface. As the fluid evaporates it uses heat from the blood as the latent heat of vaporisation.
What is excretion?
The removal of metabolic waste from the body
What is metabolic waste?
A substance that is produced in excess by the metabolic processes in the cells; may become toxic
Why can’t metabolic waste products be allowed to build up?
So they do not inhibit enzyme activity or become toxic
What are the main excretory products?
CO2 from respiration
Nitrogen-containing compounds such as urea
Other compounds such as bile pigments found in faeces
What is egestion?
The elimination of faeces from the body
What are the excretory organs?
Lungs
Liver
Kidneys
Skin
Functions of the liver? (7)
Control of blood glucose levels, amino acid levels, Lipid levels
Synthesis of bile, plasma proteins, cholesterol
Synthesis of red blood cells in the fetus
Storage of vitamins A,D,B12, iron, glycogen
Detoxification of alcohol and drugs
Breakdown of hormones
Destruction of red blood cells
External structures of the kidney?
Cortex
Medulla
Pelvis
Describe the nephrons?
Tiny tubules in the bulk of each kidney
Starts in the cortex as a cup-shaped structure- bowmans capsule
Forms a loop down into the medulla
Joins a collecting duct
