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| Question | Answer |
| Complete the sentences: The nervous system is made up of a complex network of cells called __________. All neurones have a ______ _______ with a nucleus (plus cytoplasm and all other organelles you usually find in a cell). | The nervous system is made up of a complex network of cells called NEURONES. All neurones have a CELL BODY with a nucleus (plus cytoplasm and all other organelles you usually find in a cell) |
| Complete the sentences: The cell body has extensions that connect to other neurones - __________ and _________carry nerve impulses towards the cell body, and _______ carry nerve impulses away from the cell body | The cell body has extensions that connect to other neurones - DENDRITES and DENDRONS carry nerve impulses towards the cell body, and AXONS carry nerve impulses away from the cell body |
| What are the 3 main types of neurones? | Sensory Motor Relay |
| Describe the structure of sensory neurones |
Sensory neurones have short dendrites and one long dendron to carry nerve impulses from receptor cells to the cell body, and one short axon that carries nerve impulses from the cell body to the CNS
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| Describe the structure of motor neurones |
Motor neurones have many short dendrites that carry nerve impulses from the CNS to the cell body, and one long axon that carries nerve impulses from the cell body to effector muscles
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| Describe the structure of relay neurones |
Relay neurones have many short dendrites that carry nerve impulses from sensory neurones to the cell body, and many short axons that carry nerve impulses from the cell body to motor neurones
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| Outline the neural pathway from the stimulus to the response | 1. A stimulus is detected by receptor cells and a nerve impulse is sent along a sensory neurone 2. When a nerve impulse reaches the end of a neurone, chemicals called neurotransmitters take the information across the synapse to the next neurone, which then sends a nerve impulse 3. The CNS processes the information, decides what to do about it and sends impulses along motor neurones to an effector |
| Complete the sentence: Sensory receptors act as ____________ (they convert the energy of stimuli into __________ impulses - nerve impulses) | Sensory receptors act as TRANSDUCERS (they convert the energy of stimuli into ELECTRICAL impulses - nerve impulses) |
| What happens when sensory receptors are in their resting state? | In its resting state, there's a potential difference across the membrane Resting potential is generated by ion pumps and ion channels |
| What is resting potential? |
The potential difference when a cell is at rest
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| What is generator potential? | The change in potential difference due to a stimulus |
| What happens to the sensory neurone when a stimulus is detected? | When a stimulus is detected, the cell membrane is excited and becomes more permeable - more ions move in and out of the cell, altering the potential difference |
| TRUE OR FALSE: A bigger stimulus excites the membrane more |
TRUE
A bigger stimulus means a bigger movement of ions and a bigger change in potential difference (a bigger generator potential is produced)
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| What is an action potential? | Electrical impulses (nerve impulses) |
| What happens to a sensory neurone if a generator potential is big enough? | If a generator potential is big enough, it'll trigger an action potential (nerve impulse) along a neurone |
| TRUE OR FALSE: If the stimulus is too weak, an action potential could still be produced | FALSE An action potential is ONLY triggered if the generator potential reaches a certain level called the threshold level. If the stimulus is too weak, the generator potential won't reach the threshold, so there's no action potential |
| What are Pacinian corpuscles? |
Pacinian corpuscles are mechanoreceptors found in the skin
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| Describe the structure of Pacinian corpuscles | Pacinian corpuscles contain the end of a sensory neurone (sensory nerve ending), wrapped in lots of layers of connective tissue called lamellae |
| How do Pacinian corpuscles work as mechanoreceptors? | When a Pacinian corpuscle is stimulated, the lamellae are deformed and press on the sensory nerve ending. This causes deformation of stretch-mediated Na⁺ channels in the sensory neurone's cell membrane. The Na⁺ channels open and Na⁺ diffuse into the cell, creating a generator potential. If the generator potential reaches a threshold, it triggers an action potential |
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