BIOLOGY MODULE 5 (papers 1 & 3) incomplete - add plant hormone PAGs and kidney stuff after mocks Flashcards
communication and homeostasis, excretion, animal responses, photosynthesis, respiration, plant hormones and responses
how does responding to their environment help an organism survive?
- e.g. avoiding harmful environments
- respond to changes in their internal environment to make sure conditions are optimal for metabolism
- any change in internal or external environment is a stimulus
- important for plants and animals
how do receptors detect a stimuli to produce a response?
- receptors only detect one particular stimulus
- some receptor cells connect to the nervous system, some are proteins on cell surface membrane and some are found in cell membranes of some pancreatic cells
what are effectors?
cells that bring about a response to a stimulus to produce an effect (include muscle cells and glands)
how does communication occur between adjacent and distant cells?
- to produce a response receptors must communicate and this happens via cell signalling
- cell signalling can occur between adjacent or distant cells e.g. NS cells communicate via neurotransmitters being detected
- cell surface receptors allow cells to recognise chemicals involved in cell signalling
what is homeostasis?
- maintenance of a constant internal environment
- involves control systems that keep internal environment roughly constant
- vital for cells to function normally and stop them being damaged
- maintaining core temp stops enzymes being denatured
- maintaining right conc of glucose in blood means theres always enough for respiration
what is your internal environment?
blood and tissue fluid that surrounds your cells
how do homoestatic systems detect a change and respond by negative feedback?
- involve receptors, a communication system and effectors
- receptors detect when a level is too high/low and info is communicated to effectors
- effectors respond to counteract change - brings level back to normal
- negative feedback restores level to normal
- negative feedback keeps things around normal level
why does negative feedback only work within certain limits?
if the change is too big then effectors may not be able to counteract it
how do positive feedback mechanisms amplify a change from the normal level?
- effectors respond to further increase the level away from normal level
- positive feedback is useful to rapidly activate something
- not involved in homeostasis as it doesnt keep internal environment constant
what does the nervous system send information as?
nerve impulses
what is the nervous system and how does it send information as nerve impulses?
- complex network of neurones
- stimulus is detected by receptor cells and a nerve impulse is sent along a sensory neurone
-when nerve impulse reaches end of neurone, neurotransmitters take info to next neurone which send a nerve impulse - CNS processed information and sends it along neurones to an effector
what are sensory neurones?
transmit nerve impulses from receptors to CNS
what are motor neurones?
transmit nerve impulses from CNS to effectors
what are relay neurones?
transmit nerve impulses between sensory and motor neurones and transmit action potentials through the CNS
what is the process of a nerve impulse travelling?
stimulus - receptors - CNS - effectors - response
what do sensory receptors do?
- convert energy of a stimulus into electrical energy
- so sensory receptors act as transducers (something that converts one form of energy into another)
how do receptor cells communicate information via the nervous system?
- when NS receptor is in resting state, there’s a difference in charge between inside and outside the cell generated by ion pumps and channels
- this means there is a voltage (potential difference) across the membrane
- when a stimulus is detected the cell membrane becomes excited and more permeable, allowing more ions to move in and out the cell - altering potential difference
- bigger stimulus excites membrane more, causing larger movement of ions and bigger generator potential
what is resting potential?
voltage/potential difference across a membrane when a cell is when a cell is at rest
what is generator potential?
the change in potential difference due to a stimulus
how is an action potential triggered?
if a generator potential is big enough and reaches a threshold level
what is the structure of a sensory neurone?
- short dendrites
- one long dendron to carry nerve impulses from receptor cells to cell body
- one short axon that carried impulses from cell body to CNS
what is the structure of a motor neurone?
- many short dendrites that carry nerve impulses from CNS to cell body
- one long axon that carries nerve impulses from cell body to effector cells
what is the structure of a relay neurone?
- has many short dendrites that carry nerve impulses from sensory neurones to cell body
- one axon that carried nerve impulses from cell body to motor neurones
what is an example of a sensory receptor converting stimulus energy into nerve impulses?
- pascinian corpuscles contain the end of a sensory neurone (sensory nerve ending)
- sensory nerve ending is wrapped in lamellae
- when pascinian corpuscle is stimulated, lamellae are deformed and press on sensory nerve ending
- this causes deformation of stretch-mediated sodium channels in sensory neurones cell membrane
- sodium channels open and sodium ions diffuse into cell creating generator potential