Responding To Internal And External Environments Flashcards
What is kinesis?
Yr2 Topic 8: Chemical Control
The random behaviour pattern where an animal responds to a change in stimulus by increasing or decreasing activity.
Define taxes
Yr2 Topic 8: Chemical Control
The movement of an organism either towards or away from a directional stimulus. Can be positive (moving towards the stimulus) or negative (moving away from the stimulus).
Explain why woodlice which don’t clump together have a greater percentage loss in mean mass compared to woodlice which do clump together? (3)
Yr2 Topic 9: Nervous System
- (More mass loss) linked to losing more water
- Gills (more) exposed to air/ covered (less) by other woodlice so greater surface area (exposed)
- (Not clumped) so lower humidity (around each woodlouse) so greater evaporation/ diffusion (of water)
What is the function of the nervous system?
Yr2 Topic 9: Nervous System
- detection of stimuli by receptors
- transmission of nerve impulses by neuroes
- response by effectors
What is a neurone?
Yr2 Topic 9: Nervous System
They are specialised cels that carry electrical impulses from one part of the body to another.
What are the different types of neurone?
Yr2 Topic 9: Nervous System
- Sensory
- Inter or bipolar (or intermediate or relay)
- Motor
What is the reflex arc order?
Yr2 Topic 9: Nervous System
Receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
What is the function of the dendrite?
Yr2 Topic 9: Nervous System
Receives information from other neurones or the environment
What is the function of the axon?
Yr2 Topic 9: Nervous System
carries electrical impulses
What is the function of an axon terminal?
Yr2 Topic 9: Nervous System
he site of neurotransmitter release
What is the function of the myelin sheath?
Yr2 Topic 9: Nervous System
Allows for quick & effective transition of nerve cells
What is the function of the node of ranvier?
Yr2 Topic 9: Nervous System
Allow for generation of fast electrical impulses
What is the function of the Schwann cells
Yr2 Topic 9: Nervous System
They produce myelin
What is a synapse?
Yr2 Topic 9: Nervous System
The gaps between neurones
How do synapses work?
Yr2 Topic 9: Nervous System
- Calcium ions open after moving into the synaptic knob via facilitated diffusion
- Neurotransmitters are released as the influx of calcium activates enzymes and the vesicles fuse with the presynaptic membrane
- Sodium channels open after neurotransmitters are released into the synaptic cleft and diffuse across to the post synaptic membrane, binding with sodium ions and depolarisation occurs
- New action potential
- Acetylcholinesterase breaks up acetylcholine into acetyl and choline which are reabsorbed by the presynaptic neurone
- Acetylcholine is remade
How does the pacinian corpuscle work?
Yr2 Topic 10: Receptors
Pressure on the skin changes the shape of the corpuscle and layers re distorted
The layers contain stretch mediated sodium ion channels which are pressure sensitive.
The change in shape causes the sodium channels to open, increasing the permeability to sodium ions, which diffuse in.
The charge changes across the membrane and decreases polarity, more positive ions on inside leads to depolarisation.
This produces a generator potential and reaches above the threshold of an action potential, which leads to nerve impulses passing along the neurone
What are receptors?
Yr2 Topic 10: Receptors
They are cells which can detect a specific stimulus and convert some sort of energy into a generator potential
What are the different types of receptors?
Yr2 Topic 10: Receptors
Pressure, temperature and chemical
What type of receptor is a pacinian corpuscle?
Yr2 Topic 10: Receptors
Pressure receptor
Describe ow a Pacinian corpuscle produces a generator potential when stimulated? (3)
Yr2 Topic 10: Receptors
- (Increased pressure) deforms/ changes stretch mediated sodium channel
- (Sodium channels open and) sodium ions flow in
- Depolarisation (leading to generator potential)
Explain how resting potential is maintained in the sensory neurone when no pressure is applied? (2)
Yr2 Topic 10: Receptors
- Membrane more permeable to potassium ions and less permeable to sodium ions.
- Sodium ions actively transported/ pumped out and potassium ions in.
The membrane potential at the end of the neurone was the same whether medium or heavy pressure was applied to the finger tip. Explain why. (2)
Yr2 Topic 10: Receptors
- Threshold is reached
- (Threshold or above) causes maximal response/ all or nothing principle
Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower response to stimuli.
Yr2 Topic 9: Nervous System
- Less/no saltory conduction/action potential/impulse unable to ‘jump’ from node to node.
- More depolarisation over length/area of membranes
Define homeostatis.
Yr2 Topic 12: Homeostasis
The maintenance of a constant internal environment.
It ensures that the internal cells of the body are in an environment that meets their needs and allows them to function normally despite internal or external changes.
