Responding To The Environment Flashcards
What are effectors?
Effectors are cells which bring about a response to a stimulus, e.g. Muscle cells and cells found in glands.
What are the 3 types of neurones?
Sensory neurones, motor neurones, relay neurones.
What is a sensory neurones?
The sensory neurones transmits electrical impulses from receptors to the central nervous system.
What is a motor neurone?
The motor neurone transmits electrical impulses from the central nervous system to effectors.
What is a relay neurone?
The relay neurone transmits electrical impulses between sensory neurones and motor neurones
What response does your nervous system make when you detect a stimulus?
The stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neurone. When the electrical impulse reaches the end of a neurone, chemicals called neurotransmitters take the information to the next neurone. The CNS processes the information and sends impulses along motor neurones to an effector.
What is a gland?
A gland is a group of cells that are specialised to secrete a useful substance, such as a hormone. E.g. The pancreas.
What are hormones?
Hormones are chemical messengers, e.g. Insulin.
How does the hormonal system send information?
When a gland is stimulated, it secretes hormones. Hormones diffuse into the blood, where they are taken around the body by the circulatory system. They diffuse out of the blood and bind to specific receptors for that hormone. The hormones trigger a response in the target cells.
How can glands be stimulated?
Glands are stimulated by a change in concentration of a substance, e.g. A hormone, and they can also be stimulated by electrical impulses.
What are the properties of the hormonal communication system?
Hormones travel in the blood to reach their target organs, so hormone communication is slower than electrical communication. Hormones aren’t broken down as quickly as neurotransmitters so the effects of hormones last for longer. Hormones are transported all over the body, so the response may be widespread.
What a the properties of the nervous communication system?
When an electrical impulse reaches the end of a neurone, neurotransmitters are secreted onto cells so the nervous response is localised. Neurotransmitters are quickly removed once they are secreted so the response is short lived. Electrical impulses are rapid, so the response is rapid.
Why do organisms respond to changes in their environment?
Animals respond to changes in their external environment by avoiding harmful places which are too hot or too cold. They respond to changes in their internal environment by making sure that the conditions are always optimal for their metabolism.
How do receptor cells communicate information via the nervous system?
When a receptor is not being stimulated, there is a difference in charge between the inside and outside of the cell - so there is a potential difference across the membrane. When a stimulus is detected, the cell membrane becomes more permeable, so more ions move in and out of the cell- altering the potential difference. The bigger the stimulus, the more ions move in and out of the cell. More ions creates a larger generator potential. If the generator potential is large enough it triggers an action potential.
What is a generator potential?
The generator potential is the change in potential difference across the receptor membrane.
How is a bigger generator potential produced?
When there is a bigger stimulus the membrane is excited more, causing a bigger movement of ions and a bigger change in potential difference.
How does an action potential get produced?
If a generator potential is big enough it triggers an action potential - an electrical impulse along a neurone. The action potential is only triggered if the generator potential reaches a certain level called the threshold level.
What is the threshold level?
The threshold level is the level which the potential difference has to change by to create and action potential.
What is a pacinian corpuscle?
Pacinian corpuscles are mechanoreceptors, which detect mechanical stimuli, e.g. Pressure and vibrations. They are found in your skin.
What is the structure of a pacinian corpuscle?
A pacinian corpuscle contains the end of a sensory neurone which is wrapped in layers of conductive tissue called lamellae.
What happens when a pacinian corpuscle is stimulated?
When a pacinian corpuscle is stimulated the lamellae are deformed and press on the sensory nerve ending. This causes deformation of stretch mediated sodium channels in the cell membrane of the sensory neurone. The sodium ion channels open and sodium ions diffuse into the cell, creating a generator potential. If the generator potential reaches the threshold level an action potential is triggered.
How do photoreceptors in your eye detect light?
Light enters your eye through the pupil. Your pupil is made smaller or larger to control the amount of light entering your eye, by the muscles of your iris. Light rays are focused by the lens onto the retina. The retina contains photo receptor cells.
What is the fovea?
An area of the retina where there are lots of photoreceptors.
Why is the blind spot not sensitive to light?
The blind spot is not sensitive to light because there aren’t any photoreceptors there.
How do photoreceptors convert light to an electrical impulse?
Light enters your eye and is absorbed by light sensitive pigments. Light bleaches the pigments and causes a chemical change which alters the membrane permeability to sodium. This creates a generator potential and if it reaches the threshold a nerve impulse is sent across a bipolar neurone which takes the impulse to the brain.
What are the two types of photoreceptors?
Rod cells and cone cells.
Why are rod cells very sensitive to light?
Rod cells are very sensitive to light because many rod cells join one neurone, so many weak generator potentials combine to reach the threshold and trigger an action potential.
Where are the rod cells?
Rod cells are found in the peripheral parts of the retina.
Where are cone cells found?
Come cells are packed together in the fovea.
Why are cone cells only sensitive to bright light?
Cone cells are less sensitive to rod cells because one cone cell joins one neurone do it takes more light to reach the threshold and trigger an action potential.
Why do rod cells have low visual acuity?
Rods cells have low visual acuity because many rod cells join the same neurone. Therefore, light from 2 objects close together can’t be told apart.
Why do cone cells have high visual acuity?
Cone cells have high visual acuity because cones are close together and one cone joins one neurone. Therefore when light from 2 points hits 2 cone cells 2 action potentials are made so you can distinguish the 2 points which are close together.
What is the resting potential?
The resting potential is the voltage across the membrane when it is at rest.
What does the sodium potassium pump do?
The sodium potassium pump actively transports 3 sodium ions out the neurone for every 2 potassium cells moved in.
What does the potassium ion channel do?
Potassium ion channels allow facilitated diffusion of potassium ions out of the neurone.
