5.1 - Communication And Homeostatis Flashcards
How do animals increase their chances of survival ?
- They respond to changes in their external environment, e.g by avoiding harmful environments such as places being on hot or cold.
- They also respond to changes in their internal environment to make sure conditions are always optimal for their metabolism.
What is meant by ‘ Stimulus’ ?
- A change in the internal or external environment.
What do receptors do ?
- They detect stimuli
- They are specific - detect a particular - light or pressure
Name examples of receptors
- Photo receptors - detect cells that are connected to NS
- ## Proteins on cell surface membranes , glucose receptors are proteins found in plasma membrane and some on pancreatic cells
What is a effector ?
- They can bring about a response to a stimulus to produce an effect.
- examples include muscles and glands
How can communication occur ?
- They occur between adjacent and distant cells
- This happens via cell signalling
-E.g - Adjacent nervous system communicate by secreting chemicals called neurotransmitters send signals to adjacent cells. - Distant cells- gland send hormones which travel in blood to distant cells
What is Homeostasis ?
Homeostasis is the Maintenance of a Constant Internal Environment
1) Changes in your external environment can affect your internal environment
- the blood and tissue fluid that surrounds your cells.
2) Homeostasis involves control systems that keep your internal environment roughly constant
3) Keeping your internal environment constant is vital for cells to function normally and to stop them being damaged.
4) It’s particularly important to maintain the right core body temperature. This is because temperature affects enzyme activity, and enzymes control the rate of metabolic reactions:
5) It’s also important to maintain the right concentration of glucose in the blood, so there’s always enough available for respiration.
What is negative feedback ?
- counteracting the change
- receptors detect when a level is too high or too low , and the information is communicated via NS hormonal system to effectors.
- Negative feedback brings it back to normal
- It works within certain limits if change is too big it wont be able to counteract it
What is positive feedback ?
- when the mechanism amplifies the change from the normal level.
- effectors further increase the level away from the normal level.
- example - baby dania - The release of oxytocin from the posterior pituitary gland during labor is an example of positive feedback mechanism. Oxytocin stimulates the muscle contractions that push the baby through the birth canal.
What are Ectotherms?
- For example, reptiles and fish
- They can’t control their body temperature internally they control their temperature by changing their behaviour for example reptiles gain heat by basking in the sun
- The internal temperature depends on the external temperature
-The activity level depends on the external temperature – they’re more active at higher temperature temperatures and less active at lower temperatures
-They have a variable metabolic rate and they generate very little heat themselves.
What are Endotherms ?
- Endotherms- for example, mammals and birds
- That internal temperature is less affected by the external temperature.
- The activity level is largely independent of the external temperature. They can be active at any temperature.
- They have a constantly high metabolic rate and they generate a lot of heat from metabolic reactions.
What are the ways mammals reduce their body temperature?
- sweating – more sweat is secreted from sweat glands when the bodies too hot the water and sweat evaporate from the surface of the skin and takes heat from the body. The skin gets cooled down.
-Hair lies flat – mammals have a layer of hair that provides insulation by trapping air when it’s hot erect ply muscles relax the hairline flat so less air is trapped with the skin is less insulated and he can be lost easily. - Vasodilation when it’s hot arterials near the surface of the skin dilate, meaning more blood flows through the capillaries in the surface meaning more heat is lost from the skin by radiation and the temperature is lowered.
What are the ways mammals increase body temperature?
- Shivering- when it’s called muscles contracting spasms this makes the body shiver and more heat is produced from increased respiration
- Much less sweat – less sweat is created from the sweat gland when it’s cold reducing the amount of heat loss
- Hair stand up – erected ply muscles contract when it’s cold which makes the hair stand up this traps more air and so prevents heat loss.
- vasoconstriction- when it’s cold arterials near the surface of the skin constrict so less blood flows through the capillaries to reduce heat loss
- Hormones – the body releases adrenaline and thyroxine these increased metabolism more heat is produced.
What controls the body temperature in mammals?
— hypothalamus
Explain how the hypothalamus controls body temperature in mammals
- The hypothalamus receives information about temperature from thermal receptors
-Thermoreceptors in the hypothalamus detect internal temperature (blood) - Thermoreceptors in the skin – peripheral temperature receptors detect external temperature
-Thermoreceptors send impulses along sensory neurons to the hypothalamus which sends impulses along motor neurons to effectors. - The effectors respond to restore the body temperature back to normal.
