Nervous Coordination Flashcards
What is a stimulus and examples?
A detectable change in the environment
Light , pressure, temperature, smell, touch
Simple reaction pathway order
Stimulus= receptor= sensory neuron= coordinator= relay neuron= Motor neurone =effector=response
Why do organisms need to respond to changes in the environment?
- Avoidance of harmful environment., competition, predators
- Stay within a favourable environment
- Growth towards or away from a stimulus
- Dispersal to find new mates
Describe taxes and state an advantage of this type of movement
Taxes= whole motile tile organism has a directional response to move away or towards from a named stimulus
Advantage = avoid competition, increased dispersal to find mates, stay within a favourable environment, avoid predators
Describe kinesis and state and advantage of this type of movement?
Kinesis =whole motile organism has a random movement to where the movement increases or decreases in response to a name stimulus
Advantage = does not move towards or away from my name stimulus or avoid predators competition and allows dispersal to find new mates. Stay within a favourable environment
Describe tropism
A directional response to part of an organism to a name stimulus
Advantages of reflex arc
Protected against damage to body tissue
Help escape from predator
Does not have to be learnt
Enable homeostatic control
Find food
What is positive tropism?
Growth towards a stimulus
What is negative tropism?
Growth away from a stimulus
Why would a plant grow towards from the light?
Increases chance of light falling on leaves therefore increases rate of photosynthesis
Why would plant roots grow away from light?
Root scroll into the soil more so more likely to absorb water and minerals
What is IAA?
It is a growth factor located throughout the plant that regulate growth in response to a directional stimulus
Describe how the distribution of IAA changes and affects the plant growth in the shoot?
- IAA is synthesised in the shoot tip.
- IAA diffuses into the growing region
- Light causes movement of IAA from the light side to the shaded side
- Higher concentration of IAA on the shaded side
- This causes directional growth as the greater cell elongation on the shaded side
- Shaded side grows faster and cause a shoot to bend towards the light, which is positive tropism
Describe and explain how the distribution of IAA and affects the plant growth in the roots?
- IAA is synthesised in the root tip.
- IAA diffusers into the growing region
- Light causes movement of IAA from the light side of the shaded side towards gravity
- Higher concentration of IAA on the shaded
- Cell elongation inhibited on the shaded side
- Results in directional growth away from the light towards gravity which is negative tropism
Structure of motor neuron
Terminal end branches
Were sell
Myelin sheath
Node of Ranvier
Cell body
Nucleus
Dendrites
Describe saltatory conduction
Schwann cells produce myelin that acts as a electrical insulator
This causes Saltaryvconduction which means hydrophilic sodium and potassium ions can’t diffuse over this part of the membrane so depolarisation occurs at the nodes of ranvier so impulses jump from node to node. And non-myelinated neurons depolarisation occurs along the whole length of the neuron therefore nerve impulses faster in my neuron
Describe four factors that speed up the transmission of a nerve impulse?
Myelinated axon so salutatory conduction
Large diameter so less resistance to flow of ions
Higher temperature so faster diffusion through channel proteins
More channel proteins so faster diffusion
Describe how a resting potential is established and maintained in an axon ?
- So resting potential is made 1. Higher concentration of potassium ions inside and higher concentration of sodium irons outside the axon membrane.
- Both sodium ion and potassium iron voltage gated channel shot
- Axon more permeable to potassium ions or some diffuse out through leak channels whereas membrane less per two sodium iron so little diffuse in.
- Sodium potassium pump actively transports three sodium ions out and two potassium ions in which restores the axon after a action potential
- so the resting potential is maintained at. -70mv across the axel membrane meaning the inside is more negative compared to the outside.
Describe depolarisation?
- The resting potential of a Axon membrane is disturbed and reaching -55mv due to all or nothing principle
- The stimulus causes membrane to become more permeable to sodium ions and causes sodium ion voltage gated channel proteins to open.
- There is a higher concentration of sodium ions outside the axon membrane and they rapidly diffuse into the cell by facilitated diffusion through their channel proteins.
- This causes the axon of membrane to become more positive .
- Potassium ion voltage gated channels are closed at this time
Describe repolarisation ?
- Sodium ions keep diffusing into through their channel which causes the internal potential difference to reach +40mv as the inside of the axon membrane is more positive than the outside
- This causes sodium ion voltage gated channels to shut and potassium voltages gated channels to old..
- There are more potassium ions on the inside of the membrane so more permeable to potassium ions so than the outside so ions diffuse out their potassium ion voltage gated channel down a concentration gradient
Describe hyper polarisation ?
- The potassium ion voltages gated channels remain open longer than needed making the inside more negative at -90mv
2.The sodium potassium pump restores the resting potential back to -70mv by actively transporting 3 sodium ions out and 2 potassium ions in. - This is known as the refractory period
What is the all or nothing principle ?
The membrane is stimulated so sodium ion voltage gated channel open. When enough sodium ions diffuse in the action Potential is above -55mv a action potential occurs along the neuron if not enough sodium ions diffuse in then threshold is not reached then no action potential
Why is the refractory period important?
The time taken to restore the resting potential so action potential can be formed
Why are synapses unidirectional?
- Vesicles containing neurotransmitters are only found in the pre synaptic neuron
- Receptors for neurotransmitters are only found in post synaptic neurone membrane
