Biology Unit 5 Flashcards - Response to stimuli

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What is 'Taxis?'
The movement of organisms either positively or negatively towards or away from a stimulus
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What is 'Kinesis?'
This is a more unpleasant stimulus that causes more rapid movements of organisms and makes them change direction more
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What is 'Tropism?'
The growth movement in plants
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What is the plant growth hormones?
Auxin
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Name the 3 stimuli that a plant can grow towards or away from
Geotropism - Gravity, Phototropism - Light, Hydrotropism - Water
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What type of movement is a stem growing towards a light source?
Positive phototropism of the stem and negative geotropism (moving away from gravitational pull)
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Names the sequence of events from a stimuli to a response
Stimulus - receptor - coordinator - effector - response
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Name the 2 divisions of the nervous system
Central nervous system and Peripharal nervous system
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What makes up the CNS?
Spinal cord and brain
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What makes up the PNS?
A pair of nerves that originate from the brain and spinal cord
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What is the PNS divided into?
Sensory neurones - carry nerve impulses from receptor towards the CNS and Motor neurones - which carry nerve impulses away from the CNS to effectors
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What is the motor neurone system subdivided into?
Volutary nervous system - Carries nerve impulses to body muscles and is under voluntary control and the Autonomic nervous system - which carries nerve impulses to glands, smooth and cardiac muscles and is not under voluntary control
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What is the spinal cord?
Column of nervous tissue that runs along the back and lies inside the vertebral column for portection.
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Name 3 features of the spinal cord
Either - spinal nerve, contains sensory neurones, intermediate neurone, motor neurone.
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What is a involuntary response to a sensory stimulus called?
A reflex
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What is a reflex arc?
The pathway of neurones involved in a reflex
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Name step 1 of spinal reflex events of moving your hand away from a candle
Stimulus - Heat from hot object (candle)
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Name step 2 of sinal relfex events
Receptor - Temperature receptors in the skin detect heat and create a nerve impulse in a sensory neurone
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Name step 3 of spinal reflex events
Sensory neurone - Passes the nerve impulse to the spinal cord
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Name step 4 of spinal reflex events
Intermediate neurone - Links the sensory neurone to the motor neurone in the spinal cord
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Name step 5 of spinal reflex events
Motor neurone - Carries the nerve impulse from the spinal cord to a muscle in the upper arm
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Name step 6 of spinal reflex events
Effector - muscle in the upper arm, stimulated to contract
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Name step 7 of spinal reflex events
Response - Pulling the hand away from the hot object (candle)
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What 2 divisions does the autonomic nervous system control?
Sympathetic nervous system & Parasympathetic nervous system
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What is the function of the SNS?
Stimulates effectors when we exercise or experience powerful emotions, so speeds up activity to prepare us (fight or flight response.)
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What is the function of the PSNS?
Inhibits effectors so slows down any activity. Controls activity under normal resting conditions to conserve energy.
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What word is used to describe the difference between the SNS & PSNS?
The are antagonistic meaning they oppose each other eg; if one system contracts a muscle, the other relaxes it.
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What is the typical resting heart rate of a human adult?
70 bpm
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What area controls the changes of heart rate?
Medulla Oblongata
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What are the 2 centres of the medulla oblongata?
A centre that increases heart rate - linked to the sinoatrial node by the SNS & a centre that decreases heart rate which is linked to the sinoatrial node by the PSNS
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What determines which of these centres (increase of decrease of heart rate) is stimulated?
Chemical changes in the blood and / or pressure changes in the blood
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Where are chemeoreceptors found?
In the wall of the carotid arteries that serve the brain
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What are chemeoreceptors sensitive to?
Changes in the pH of the blood from changes in carbon dioxide concentration which is an acids and therefore lowers the pH
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How do chemeoreceptors respond to a stimulus? (card 1)
They and the aorta detect the decrease in pH and increase the frequency of nervous impulses to the centre in the medulla oblongata that increase the heart rate
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How do chemeoreceptors respond to a stimulus? (Card 2)
This centre increases the frequency of nerve impulses via the SNS to the sinatrial node which increases heart rate, the increased blood flow causes more Co2 to be removed by the lungs
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How do chemeoreceptors respond to a stimulus? (Card 3)
As a concequence of pH returning to normal, the chemeoreceptors reduce the frequency of nerve impulses to the medulla oblongata which also reduces the frequency of impulses to the sinoatrial node, which decreases heart rate to normal.
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What are pressure receptors?
Occur within the walls of the carotid arteries and the aorta
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What do the pressure receptors do when blood pressure is higher than normal?
They transmit a nervous impulse to the centre of the medulla oblongata that decreases heart rate, this centre sends an impulse via the PSNS to the sinoartrial node of the heart which decreases the heart rate
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What do pressure receptors do when the blood pressure is lower than normal?
They transmit a nervous impulse to the centre of the medulla oblongata that increases the heart rate, the centre sends an impulse via the SNS to the sinoartrial node which increases the heart rate
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What does the Pacinian corpuscle respond to?
A change in the mechanical pressure
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Name 2 features of the pancinian corpuscle
It's specific to a single type of stimulus (mechanical pressure) & it produces a generator potential by acting as a transducer
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Where are the pancinian corpuscle most abundant?
They occur deep in the skin, fingers and sole of the feet, also occur in joints and ligaments
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What do the pancinian corpuscle have in their plasma membrane?
A special type of sodium channel; stretch-mediated sodium channel
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Where are the light receptors of the eye found?
On the innermost layer; the retina
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What 2 types are the millions of light receptors?
Rod cells and Cone cells
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What is a main feature of a Rod cell?
It cannot distinguish the different wavelengths of light so can only produce images in black and white
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What light intensity can Rod cells respond to?
Very low light intensity
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What are the benefits of many rod cells attaching to a single bipolar cell?
There is a much greater chance that the threshold value will be exceeded and an action potential will occur
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How many types of cone cells are there?
3 types - each responding to a different wavelength of light
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What light intensity do cone cells respond to and why?
High light intensity due to them only being connected to one bipolar cell each so cannot help each other cross the threshold value
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Other cards in this set

Card 2

Front

What is 'Kinesis?'

Back

This is a more unpleasant stimulus that causes more rapid movements of organisms and makes them change direction more

Card 3

Front

What is 'Tropism?'

Back

Preview of the front of card 3

Card 4

Front

What is the plant growth hormones?

Back

Preview of the front of card 4

Card 5

Front

Name the 3 stimuli that a plant can grow towards or away from

Back

Preview of the front of card 5
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