Survival and responses - 3.6.1.1
Simple reflexes
- A simple reflex is a rapid, involuntary response to a stimulus. - The pathway of communication goes through the spinal cord but not through the conscious part of the brain, so the response happens automatically. - This is because you don't have to spend time deciding how to respond, information travels really fast from receptors to effectors. - Simple reflexes are protective, they help organisms to avoid damage to the body because the response happens so quickly.
Tropisms
- Flowering plants like animals increase their chances of survival by responding to changes in the environment. - Plants sense the direction of light and grow towards it to maximise absorption for photosynthesis. - A tropism is the response of a plant to a directional stimulus, plants do this by regulating their growth. - A positive tropism is growth towards the stimulus where as a negitive tropism is away from the stimulus.
Gravitropism (geotropism)
- Gravitropism is the growth of a plant in response to gravity. - Shoots are negatively gravitropic as they grow upwards. - Roots are positively gravitropic and grow downwards.
24) What parts of the plant produce growth factors?
- Growing regions/Shoot/Tip
12) Suggest why it is beneficial for an organism to be able to detect and respond to pain.
- Helps protect the organism be responding to situations and environments which could cause the body pain.
28) Explain how the distribution of IAA affects growth of shoots in response to light.
- IAA concentration increases on the shaded side of a shoot. - This means that the cells on the shaded side of shoot grow faster than those exposed to light. - This causes the shoot to bend to bend towards the light.
Example of phototropism
- IAA moves to the more shaded part of the shoots and roots os there is uneven growth. - IAA concentration increases on the shaded side, cells elongate and the shoot bends towards the light.(Shoot) - IAA concentration increases on the shaded side and growth is inhibited so the roots bend away from the light.(ROOT)
Example of gravitropism
- IAA moves to the underside of shoots and roots so there is uneven growth. - IAA concentration increases on the lower side, cells elongate so the shoot grows upwards.(SHOOT) - IAA concentration increases on the lower side, growth is inhibited so the roots grow downwards.(ROOT)
16) Give two types of cell that act as effectors
- Muscle cells - Cells found in glands
11) Congenital insensitivity to pain is the condition where the body does not feel physical pain. The condition is a result of non-functioning nociceptors, the ability for sufferers to feel a light touch is usually normal. Suggest why people with this condition are able to feel light touch even though they can not feel pain.
- Particular receptors are specific to a particular stimulus. - This means that its possible that while their pain receptors aren't function (so pain isn't felt) their touch receptors are functioning. - Allowing light touches to be felt
18) Describe the pathway of nervous communication from stimulus to to response in voluntary responses.
- Receptor cells detect a stimulus - Sensory neurones transmit electrical impulses from the Receptors to the CNS. - CNS proccesses the infomation and sends impulses along motor neurones to the effector which responds.
Receptors
- Receptors detect stimuli, they can be cells, or proteins on the cell surface membrane. - They are specific to one type of blood stimulus.
25) How do auxins effect plant growth?
- Stimulate growth by cell elongation
17) What is the role of the receptor?
- To detect stimulus
13) Describe the role of the sensory neurone
- Transmit electrical impulses from receptors to the CNS.
Phototropism
- Is the growth of a plant in response to light - Shoots are positively phototropic and grow towards the light. - Roots are negatively phototropic and grow away from the light.
Indoleacetic acid (IAA)
- Is an important auxin that is produced in the tips and shoots of flowering plants. - Its moved around the plant to control tropisms, moved by diffusion and active transport over short distances and via the phloem over long distances. - This results in different parts of the plant having different concentrations of IAA. - This uneven distribution means that there is uneven growth throughout the plant.
Investigating simple animal responses
- A choice chamber with different components in which you create different environmental conditions is used. - It can be used to investigate how animals such as woodlice or maggots respond to light intensity or humidity.
2) E.Coli bacteria have been observed to move towards the highest concentration of oxygen in their surroundings, suggest why E.coli move in this way.
- An environment with higher oxygen is a more favourable environment for them to be in.
Effectors
- Are the cells that bring about a response stimulus, to produce and effect. - Effectors include muscle cells and cells found in glands such as the pancreas. - Receptors communicate with effectors via the nervous system or hormonal system.
21) Why do simple responses help organisms to avoid damage to their body.
- Because they provide a rapid response
How a choice chamber is set up
- Construct the choice chamber as shown in the diagram
27) How does IAA move around the plant
- Diffusion and active transport over short differences - Phloem over long distances
4) What is a tactic response
- Directional movement in response to a stimulus
Taxis (Tactic Response)
- Directional movement in response to a stimulus. - The direction of the stimulus affects the response. - Eg woodlice can show a tactic response to light, they move away from a light source which helps them survive as it keeps them in damp conditions reducing water loss. - If an organisms moves towards the stimulus its a positive taxis, and if it moves away from the stimulus its a negative taxis.(negative to light)
Nervous Communication example
- Eg you see a friend waving and you want to wave back - Stimulus, You see a friend waving - Receptors, light(photoreceptors)in your eyes detect the wave and electrical impulse is carried by sensory neurone to the CNS. - CNS, processes the information and send electrical impulses along a motor neurone. - Effectors, muscle cells are stimulated by the motor neurone. - Response, muscles contract to make your arm wave.
29) Explain how the distribution of IAA affects the growth of roots in response to gravity.
- IAA concentration increases on the underside of roots. - This means that the cells on the underside of the roots don't grow as quickly as those on the upper side. - This pattern of growth causes the root to grow downwards in the same direction of gravity.
26) What is indoleacetic acid and where is it produced.
- Is a auxin - Produced in the tips of the shoots and roots in flowering plants.
Kinesis (kinetic Response)
- Non directional, random movement in response to a stimulus. - Intensity of the stimulus affects the response - e.g. Woodlice show a kinetic response to a humidity, they move faster and turn more in drier conditions helping them to find damp conditions preventing water loss.
5) What is a Kinetic response
- Non-directional random movement in response to stimulus.
Responding to the environment
- Organisms increase their chance of survival by responding to changes in their external environment. - Animals and plants respond in different ways - Animals can move away from harmful environments whilst plants can change they way they grow to find more favourable conditions. - Organisms can also respond to changes in their internal environment to make sure the conditions are optimal for their metabolism.
22) What name is given to the growth of a plant in response to light.
- Phototropism
Auxins
- Plants respond to directional stimuli using specific growth factors. - These are hormone like chemicals that speed up for slow down growth. - Plant growth factors are produced in the growing regions of the plant.(shoot and root tips) and move to where they are needed in the other parts of the plant. - Growth factors called auxins are produced in the tips of shoots and diffuse backwards to stimulate the cells just behind the tip to elongate( walls become lose and stretchy) so the cell gets longer. - If the tip of a shoot is removed no auxin will be available and the shoots stop growing. - Auxins stimulate growth in shoots but too high concentrations will inhibit growth roots.
7) Name the stimulus and effector of the knee jerking reflex.
- Stimulus = Light tap / Touch - Effector Quadriceps muscles
Reflex arc in response to heat
- Stimulus, you touch a hot surface - Receptors - Thermoreceptors in your skin detect the heat stimulus. A sensory neurone carries the impulse to the CNS. - CNS, a relay neurone in your spinal cord carries the impulse to a motor neurone. - Effector, The motor neurone carries the impulse to muscle cells in your biceps. - Response, your biceps muscles contract to pull your hand away from the heat source and stop your hand being damaged. HOWEVER, if there is a relay neurone involved in the simple reflex arc then it is possible to override the reflex, eg the brain could tell your hand to withstand the heat.
1) E.Coli bacteria have been observed to move towards the highest concentration of oxygen in their surroundings, what type of simple response is this ?
- Tactic
8) The knee jerking reflex is unusual because the sensory neurone synapses directly onto the motor neurone in the spinal cord. Describe how this differs from a simple reflex, such as hand withdrawing from heat.
- The knee jerking reflex doesn't involve a relay neurone in the spinal cord, usually 3 neurones involved in a simple reflex arc/
10) Many nociceptors (pain receptors) are located in the skin. Describe the pathway of nervous communication that would take place in a healthy person if they pricked their finger with a pin.
- The nociceptors detects the stimulus and impulses are passed to the sensory neurone. - This passes the electrical impulses to a relay neurone in the spinal cord/CNS which carries the impulses to a motor neurone. - The motor neurone carries the impulses to an effector.
20) Reflexes are involuntary response to stimuli, why?
- The pathway of communication goes through the spinal cord but not the concious part of the brain, so the response is automatic.
The reflex arc
- The pathway of neurones linking receptors to effectors in a simple reflex is called a reflex arc. - These neurones are involved a sensory neurone, a relay neurone and a motor neurone.
9) The knee jerking reflex is unusual because the sensory neurone synapses directly onto the motor neurone in the spinal cord. Suggest what effect tapping the patella tendon might have on someone with a spinal injury.
- The quadriceps may not contract and there may be no response. - This is because if the spinal cord is damaged then the sensory neurone may not be able to transmit nervous impulses to the motor neurone and so the motor neurone can not transmit impulses to the leg muscles.
19) Explain why nervous communication leads to a localised and short response.
- The response is localised because the neurotransmitters are secreted directly into the cells. - The response is short lived because the neurotransmitters are removed quickly once they have done their job.
6) The knee jerking reflex involves lightly tapping on a persons patella causing the quadriceps to contract, suggest away this response would differ if it was not a reflex.
- The response would be slower - The response would be voluntary
23) Plantshoots are negatively gravitropic, what does this mean.
- They grow in the opposite direction to the force of gravity.
3) Why is it important for organisms to respond to stimuli?
- To increase their chance of survival
How to carry out the experiment?
- To investigate the effect of light intensity on woodlouse movement cover one-half of the lid with black paper. - This will make one side of the chamber dark. - Put damp filter paper down on each side to make humidity constant throughout the chamber. - Place ten woodlice on the mesh in the centre of the chamber and position the lid on the mesh so its lined up with the base below. - After 10 minutes off the lid and record the number of woodlice on each side of the chamber.(minimise the time the lid is off to prevent disruption of conditions created) - Repeat the experiment after moving the woodlice back to the centre. - Most woodlice should end up in the darkness as it is a tactic response to light. - To investigate humidity place some damp filter paper on one side and some drying agent such as silica gel on the other side. Don't cover the lid and leave for 10 minutes for the environmental conditions to stabilise before carrying out the experiment.
15) Describe the role of the relay neurone
- Transmits electrical impulses between sensory neurones and motor neurones.
14) Describe the role of the motor neurone
- Transmits electrical impulses from CNS to effectors.
Nervous Communication
- Voluntary response - A stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neuron. - When an electrical impulse reaches the end of a neurone chemicals called neurotransmitters take the information across the gap (synapse) to the next neurone where another electrical impulse is generated. - The CNS processes the information and sends impulses along motor neurones to an effector. Stimulus>Receptors> Sensory N>CNS>Motor N>Effector>Response
The nervous response
- When an electrical impulse reaches the end of s neurone chemical messengers called neurotransmitters are secreted directly into the cells so the nervous response is localised. - Neurotransmitters are quickly removed once they have done their job so the response is short lived. - Electrical impulses are really fast so the response is usually rapid, this allows animals to react quickly to stimuli.
Simple responses
-Eg Woodlice have simple responses to keep them in a favourable environment, with their response either being tactic or kinetic.
The nervous system - Neurones (Nerve cells)
The nervous system is made up of a complex network of cells called neurons, there are 3 types. - Sensory neurons, these transmit electrical impulses from receptors to the CNS(brain and spinal cord) - Motor neurons which transmit electrical impulses from the CNS to the effector muscles. - Relay neurons which transmit the electrical impulses between sensory neurons and motor neurons.
