5441049
Description
Flashcards by hannawin98, updated more than 1 year ago
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Created by hannawin98
almost 8 years ago
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| Question | Answer |
| What is a receptor? | A cell or protein on the cell surface membrane that detects a stimuli |
| What is an effector? | Cells that bring about a response to a stimuli e.g muscle cells |
| What are the three main types of neurone? | 1. Sensory Neurone 2.Motor Neurone 3.Relay Neurone |
| Describe the Nervous communication system | 1. A stimulus is detected by receptor cells 2. A nerve impulse is sent along a sensory neurone to the Central Nervous System 3.The CNS processes the information and sends an impulse along a motor neurone to an effector |
| What is a transducer? | Something that converts one form of energy into another e.g sensory receptors |
| What is the resting potential? | When a cell isn't being stimulated, there's a difference in charge between the outside of a sensory cell and the inside due to the movement of 3 Na+ ions out of the cell for every 2 K+ ions pumped into the cell. |
| Outline how an action potential is generated and describe depolarisation | 1. A stimulus is detected 2. This excites the membrane causing Na+ ion channels to open 3. Sodium ions diffuse into the neurone down its electrochemical gradient 4. If the potential difference reaches the threshold potential voltage gated Na+ ion channels open and more sodium ions diffuse into the neurone 5. This causes the potential to rise to around +30mV this is called depolarisation |
| Describe repolarisation | 1. At +30mV Na+ ion channels close and K+ ion channels open 2. K+ ions diffuse out of the neurone which decreases the potential difference of the neurone, so the neurone becomes repolarised |
| What is Hyperpolarisation | This is when K+ ions are slow to close and so the potential difference drops lower than the resting potential of the neurone as too many K+ ions diffuse out of the neurone |
| What is the refractory period? | A period of time after an action potential where the neurone can't be excited again as the Na+ ion channels cannot open. This acts as a time delay between two action potentials |
| Why are refractory periods necessary? | 1. They prevent action potentials overlapping but pass as discrete (separate) impulses 2. Makes sure action potentials are unidirectional |
| What is the all-or-nothing nature of action potentials? | This describes the fact that if the threshold potential is reached, the action potential fires with the same change in voltage, no matter how big the stimulus is. However if it isn't reached no action potential will fire. |
| What three factors increase the speed of conduction of action potentials? | 1. Myelination 2. Axon Diameter 3. Temperature |
| What are the Nodes of Ranvier? | The space between the myelin sheath which is bare neurone. |
| What is saltatory conduction and how does it speed conduction? | Saltatory conduction describes the "jumping" effect that myelinated neurones have. This is where depolarisation can only occur in the Nodes of Ranvier and so the neurones cytoplasm conducts enough electrical charge to depolarise the next Node, so the impulse jumpes from Node to Node |
| How does Axon diameter(1) and temperature(2) speed conduction? | 1. Bigger axon diameters have less resistance of ions in the neurone's cytoplasm so depolarisation reaches other parts of the neurone quicker 2. Ions diffuse faster at higher temperatures, however above 40 degrees proteins denature |
| What is a synapse? | The junction between a neurone and another neurone or a neurone and an effector cell. |
| What is the synaptic cleft? | The gap between the two cells |
| What is a cholinergic synapse? | A synapse that uses the neurotransmitter acetylcholine (ACh) |
| What happens when an action potential arrives at the presynaptic knob? | 1. Stimulates voltage gated calcium ion channels to open 2. Calcium ions diffuse into the synaptic knob 3. This causes synaptic vesicles to fuse with the presynaptic membrane and release acetylcholine by exocytosis |
| What happens across the synaptic cleft once ACh is released? | 1. Acetylcholine diffuses across the synaptic cleft and binds to specific cholinergic receptors on the postsynaptic membrane This causes Sodium ion channels to open which causes depolarisation of the postsynaptic membrane and an action potential is generated |
| How is the synapse restored? | 1. Calcium ions are actively transported back out of the presynaptic neurone 2. Acetylcholine is broken down by acetylcholinesterase 3. The products are reabsorbed by the presynaptic neurone and used to make more acetylcholine. |
| Roles of Synapses | 1. Divergence and convergence 2. Summation 3. Unidirectional transmission |
| What is divergence? | When one neurone connects to many neurones by one synapse so information can be dispersed to different parts of the body |
| What is convergence? | When many neurones connect to one neurone via a synapse so that information can be amplified |
| What is summation? | If a stimulus is too weak to cause an action potential, synapses add together the effect of neurotransmitters released from many neruones. There are two types: Spatial summation and temporal summation |
| What is spatial summation? | Two or more presynaptic neurones release neurotransmittors at the same time onto the same postsynaptic neurone. These neurotransmitters can be added together to reach the threshold potential. |
| What is temporal summation? | Two or more nerve impulses arrive in quick succession, making an action potential more likely because more neurotransmitter is released into the synaptic cleft. |
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