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45 Cards in this Set
- Front
- Back
What is a stimulus? |
A detectable change in the internal or external environment of an organism that produces a response |
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What is good about the ability to respond to stimuli? |
Increases chances for survival - e.g. detecting extremes of temperature. Those that survive have a greater chance of raising offspring and passing on alleles - selection pressure favouring organisms with favourable responses (moving away from an unpleasant stimulus!) |
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Which organs detect stimuli? |
Receptors |
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What is the role of recepotrs? |
Transforming energy of a stimulus into another form of energy that can be processed by the organism |
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What is an effector? |
Something that carries out the response |
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What are the two ways of transporting information around the body? |
Hormonal and nervous system |
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Stimulus -->...--> response |
Stimulus --> Receptor --> Coordinator --> Effector --> Response |
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What is a taxes? |
A response whose direction is determined by the direction of the stimulus. An organism responds by either moving towards a favourable stimulus (positive taxes) or away from an unfavourable one (negative taxes). |
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What is a kinesis? |
A response whereby the more unpleasant the stimulus is, the more rapidly the organism moves and the more rapidly it changes direction (so that it gets out of danger) |
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What is a tropism? |
A growth movement of a plant in response to a directional stimulus (e.g. moving towards the light). |
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What are the two major divisions of the nervous system? |
CNS (brain and spinal cord) and PNS (nerves that originate from either the brain or spinal cord) |
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What is the PNS divided into? (The two neurones in it) |
Sensory and motor neurones |
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Where do sensory neurones carry information from and to? |
From receptors towards the CNS |
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Where do motor neurones carry information? |
Away from the CNS to EFFECTORS |
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What is the motor nervous system divided into? |
The voluntary nervous system and autonomic nervous system (Carries nerve impulses to glands, smooth and cardiac muscle) |
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What is the spinal cord? |
A column of nervous tissue that runs along the back and lies inside the vertebral column for protection |
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The pathway of neurones involved in a reflex is known as a... |
...reflex arc |
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How many neurones do reflexes involve, and what are they? |
Three - Sensory, intermediate and motor |
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Describe the process of a reflex arc (7) |
Stimulus, receptor, sensory neurone, intermediate neurone, motor neurone, effector, response |
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Why are reflex arcs important? |
Involuntary - do not require brain and thus it is not overloaded with situations where the response is always the same |
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What are the two sections of the autonomic NS? |
Sympathetic NS and parasympathetic NS (they are antagonistic) |
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What does the sympathetic NS do? |
Stimulates effectors |
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What does the parasympathetic NS do? |
Inhibits effectors - slows odwn activity |
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Where is heart rate controlled? |
Medulla Oblongata - two different sections |
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Decrease in pH --> |
Increase in HR |
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Increase in pressure --> |
Decrease in HR |
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Where are chemoreceptors and baroreceptors located? |
In the aortic arch and caroted arteries. |
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When blood pressure is higher than normal... |
...baroreceptors transmit nervous impulses to MO area that decreases HR. The centre sends impulses via parasympathetic NS to SAN to decrease HR (and vise versa) |
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Pacinian corpuscles respond to changes in what type of pressure? |
Mechanical pressure |
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What are two specific features of sensory receptors? |
They respond to a single type of stimulus |
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What is a generator potential? |
All receptors convert the energy of a stimulus into a nervous impulse. This nervous impulse is known as a generator potential. |
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What is the purpose of pacinian corpuscles occurring in joints, ligaments and tendons? |
They enable the organism to know which joints are changing direction |
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How does a pacinian corpuscle transduce the mechanical energy of a stimulus into a generator potential? |
The plasma contains stretch-mediated sodium channels. Their permeability to sodium changes when they change shape (e.g. by stretching) |
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Where are light receptors found? |
The retina (inner most layer of the eye) |
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Which cells see in black and white? |
Rod cells |
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Which type of cells are more numerous in the eye? |
Rod cells (120m/eye) |
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How many sensory neurones: rod cells? |
1:3 (RETINAL CONVERGENCE) |
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Rod cells can respond to light of a very low/high intensity |
low - A certain threshold value has to be exceeded before a generator potential is created in the BIPOLAR CELLS - retinal convergence increases the likelihood the threshold value will be exceeded |
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What is needed to create a generator potential in rod cells? |
The pigment in the cells (rhodopsin) needs to be broken down - low intensity light can do this |
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What is the disadvantage of rod cells? |
They have low visual acuity as 3 rod cells only cause one nerve impulse |
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How many different types of cone cells are there? How are they different? |
3 - respond to different wavelengths of light |
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How many cone cells are there in each human eye? |
6m/eye |
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What is the name of the pigment in cone cells and how is it different? |
Iodopsin - requires a higher intensity for its breakdown |
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Light is focused by the lens on a part of the retina opposite the pupil, this is called... |
The fovea |
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What is special about the distribution of cells on the fovea? |
Many more cone cells are found there - on the periphery of the eye only rod cells are found |