Module 6 - Stimuli, both internal and external, are detected and lead to a response Flashcards
What is a stimulus?
Any change to an internal or external environment. A stimulus will signal a receptor
What are receptors?
They can be cells or proteins that are on the cell-surface membrane that detect different stimuli
What are effectors?
They are cells that bring about a response to a stimulus to produce an effect.
What are the 3 main types of neurones? What do each of them do?
Sensory neurones - transmit electrical impulses from receptors to the CNS
Motor neurones - transmit electrical impulses from the CNS to effectors.
Relay neurones - transmit electrical impulses between sensory and motor neurones.
Describe the relationship between each of these neurones….
When a stimulus is detected, receptor cells send an electrical impulse along a sensory neurone. When the electrical impulse reaches the end of the neurone, neurotransmitters are produced which take information to the next neurone which then sends an electrical impulse to the CNS. CNS processes info and sends a long motor and relay neurones
What are the 2 systems within the nervous system called?
The central nervous system and the peripheral nervous syetem
What is the difference between the somatic nervous system and the autonomic nervous system?
The somatic nervous system controls conscious activities whereas the autonomic system control unconscious actvities
What are the 2 systems contained within the autonomic nervous system and what do they do?
The sympathetic system which gets the body ready for flight or fight and the parasympathetic system which calms the body down.
What is a reflex and why is it important?
A reflex is where the body responds to a stimulus without making a conscious decision to respond. This is good to prevent animals being hurt and so they protect the body.
What is one example of a reflex arc?
When the body comes into contact with heat, the sensory neurones in the skin known as the thermoreceptor sends an electrical impulse through the sensory neurone. This then sends a electrical impulse to the relay neurone in the spinal cord and then through the motor neurone in the biceps muscle which is the effector, allowing the muscle to pull away from the hot surface
What is meant by the nervous response being localised?
When an electrical impulse reaches the end of the neurone, neurotransmitters are secreted directly onto target cells which means the nervous system is localised
What does it mean that the nervous response is short-lived?
Neurotransmitters are quickly removed once they have done the job meaning it is short-lived
How do flowering plants respond to changes in an environment?
- detect light movement to maximise absorption for photosynthesis
- Move depending on gravity
What is a tropism?
A response to a plant of a directional stimulus
Describe a positive and negative tropism?
A positive tropism is growth towards the stimulus and a negative tropism is growth towards the stimulus
What are 2 examples of tropism?
- phototropism is the growth of a plant in response to light and gravitropism is the growth of a plant in response to gravity
What are growth factors and where are they produced?
They stimulate growth of a plant by cell elongation and are produced in growth regions of the plant and then move to were they are needed in a plant.
E.G of a growth factor is an auxin
How does IAA work?
IAA moves via diffusion or active transport over short distances and then moves through the phloem over long distances which creates uneven distribution of the auxin IAA creating uneven growth.
Explain why the student removed the shoot tip from each seedling?
The shoot tip of the seedlings is where IAA is produced and so it affects the shoot length elongation
Suggest why the student added glucose solution to each petri dish
- This allows the plant to respire so that it can produced ATP which provides energy for growth
What is the distribution of IAA in a plant?
Phototropism = IAA may be concentrated in the shaded regions of the plant to stimulate cell elongation so that the shaded areas reach sunlight
Gravitropism = Increased concentration on the lower side which increases cell elongation moving it upwards
What are tactic responses (taxes)?
This is when an organism moves towards or away from a directional stimulus
What are kinetic responses (kinesis)
Movement is affected by a non-directional stimulus
How can choice chambers be used to investigate animal responses - light?
- A petri dish is divided in half and has a lid placed on top
- Place damp filter paper on both sides and then cover one half of the lid with black paper including the sides
- Place a thin piece of mesh over the petri dish and then place woodlice over this mesh
- After 10 minutes, record the number of lice on each side of the chamber
Investigating humidity using choice chambers?
Add damp filter paper to one side of the dish and then a desiccating drying agent to the other side.
What is meant by a potential difference?
When a receptor is at rest, then there is a charge between the outside and the inside of the cell
What is meant by resting potential?
The potential difference when a cell is in its resting state
What is a generator potential and what creates it?
A generator potential is a change in the potential difference. When there is a stimulus, the permeability of the membrane changes allowing more ions to move into the cell
What is an action potential and how is it created?
When a generator potential reaches its threshold, this creates an electrical impulse
What is the Pacinian Corpuscle and what does it detect?
The Pacinian Corpuscle is a mechanoreceptor that detects a mechanical stimuli such as pressure and vibrations
What is the connective tissue surrounding the nerve ending knows as
Lamellae
What happens when the Pacinian Corpuscle is stimulated?
The lamellae becomes deformed and their is pressure against the sensory nerve ending causing it to stretch. This deforms the stretch-mediated sodium ion channels and causing them to open. This allows sodium ions to diffuse into the cell creating a generator potential. A threshold will be reached creating an action potential
What is the fovea in the eye?
This is an area where there are many photoreceptors
Where is the blind spot in the eye?
Where the optic nerve leaves the eye
How is an action potential reached in the eye?
Light hits the eye and photoreceptors in the retina absorb the light in the photo pigments. Light bleaches the pigment causing a chemical change which changes the permeability of the membrane. A generator potential is generated and reaches its threshold creating an action potential
Where are rod and cone cells found?
Rods are found in the peripheral parts of the retina and cones are packed together in the fovea
What type of vision do the different photoreceptors give?
Rods (black and white) - monochromatic vision
Cones (colour) - trichromatic
What are the 3 different types of light that cone cells detect?
Green-sensitive, red-sensitive and blue-sensitive
The heart is myogenic. What does this mean?
It can contract and relax without receiving signals from nerves
What is the use of the SAN in the controlling of the heart?
The SAN (sinoatrial node) starts in the right atrium. It acts like a pacemaker and sends out regular waves of electrical
What protects electrical waves from being passed on to the atria and ventricles
Non -conductiong collagen tissue
Explain the role of the AVN, Bundle of His and purkyne tissue
Electrical waves are passed on from the SAN to the AVN. The Bundle of His carries electrical impulses from the ventricles to the apex of the heart. The bundle of His splits into thinner muscle fibre which carries electrical waves to the muscular walls of the right and left ventricles causing them to contract simultaneously.
What are the roles of baroreceptors and chemoreceptors and where are they found?
Baroreceptors - detect pressure changes and are found in the aorta and carotid arteries
Chemoreceptors - detect chemical changes and are found in the aorta, carotid arteries and Medulla
The effect of a low blood pressure on the heart rate
Baroreceptors detect a low blood pressure which sends impulses to the Medulla and then impulses are sent to the sympathetic neurones. This secretes noradrenaline which binds to receptors on the SAN. Increases heart rate
The effect of a high blood pressure on the heart rate
Baroreceptors detect a high blood pressure which sends impulses to the Medulla and then impulses are sent to the parasympathetic neurones. This secretes acetylcholine which binds to receptors on the SAN. Decreases heart rate
High 02, Low CO2 and high pH on the heart rate
Chemoreceptors detect a chemical change which sends impulses to the Medulla. Impulses are sent along the parasympathetic system which secrets acetylcholine which binds to SAN. Decreases heart rate
Low O2, High CO2, Low pH on the heart rate
Chemoreceptors detect a chemical change which sends impulses to the Medulla. Impulses are sent along the sympathetic system which secretes noradrenaline which binds to SAN. Increases heart rate
What are the photopigments in rod cells and cone cells called?
Rod cells - Rhodopsin
Cone cells - Iodopsin
