They are able to convert one form of energy to another. E.g. light sensitive cells in the retina convert light energy to electrical energy
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What are Pacinian Corpuscles
Pressure sensor that detects changes in pressure on the skin. Series of rings of connective tissue around a nerve ending, so pressure deforms rings pushing against nerve ending
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Why does Myelination increase rate of action potential remission
Forms Node of Ranvier so action potential transmitted by saltatory conduction. Depolarisation only occurs at nodes. Sodium ions experience less interaction with external ions which would decrease rate of transmission
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What are the different types of neurone?
Motor neurones carry action potential from CNS to an effector. Sensory neurones that carry action potential from a sensory receptor to the CNS. Relay Neurones connect sensory and motor neurones.
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Describe a Neurone at rest
3 sodium ions are actively pumped out of the cell for every 2 potassium ions pumped in. K channels are leaky and the K ions diffuse out. Gated sodium ion channels remain shut. Potential difference across membrane is -70mv
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Describe the process of depolarisation
Na channels open and some sodium ions diffuse in, membrane depoalruises and reaches threshole vale of -50mv. Positive feedback causes nearby voltage-gated sodium ion channels open and many Na flood in. Potential difference reaches +40mv.
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Describe the process of repolarisation
Sodium ion channels close and Potassium channels open. K ions diffuse out bringing potential difference back to negative. The potential difference overshoots to -90mv - hyper-polarisation. The original potential difference is then restored
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What is the refractory period
Time after action potential where ions are in the wrong place so its impossible to reach another action potential. Ensures action potential are transmitted in one direction
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Describe how impulses are transmitted along a neurone
During an action potential sodium ions flood into neurone down a concnetration gradient and diffuse sideways to an area of lower concentration, called local current. The diffusion causes a slight depolarisation which opens sodium ion channels
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What is the 'all-or-nothing' rule
All action potentials are the same intensity: each one produces a depolarisation of +40mv. Instead a higher frequency of action potentials means a more intense stimulus
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What are the properties of the pre-synaptic bulb
Contains many mitochondria, has a large amount of SER which packages acetylcholine into vesicles, large amount of vesicles and a large number of voltage-gates calcium ion channels
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Describe how acetylcholine is released from a pre-synaptic bulb
Action potential reaches synaptic bulb, voltage gated calcium ion channels open, calcium ions diffuse into teh synaptic bulb, Ca ions cause synaptic vesicles to fuse with pre-synaptic membrane. Acetylcholine is released by exocytosis
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How does ACh cause an action potential in post synaptic bulb
ACh binds to receptor sites on sodium ion channels in Post-synaptic membrane. Sodium ion channels open, diffuse in and excitatory post-synaptic potential (EPSP) created. If sufficient EPSPs combine, threshold potential can be reached
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What is the role of acetylcholinesterase
Hydrolyses ACh to acetic acid and choline. Stops transmission of signals, so that synapse does not continue to produce action potentials in post-synaptic neurone. Molecules then recycled, recombined to ACh using ATP from Mitochondria
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What is summation?
The combination of many Excitatory Post-Synaptic Potentials to reach the threshold potential and subsequently generate an action potential
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What are the two types of summation?
Temporal, result of several action potentials in the same pre-synaptic neurone. Spatial, result of action potentials arriving from several different pre-synaptic neurones.
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What are IPSPs
Inhibitory Post-synaptic potentials, oppose the act of summation. Several EPSPs could be prevented from producing an action potential by one IPSP
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How does Habituation affect communication
Synapse mau run out of vesicles containing neurotransmitter, nervous sytem no longer responds to stimulus. It helps to avoid over-stimulation of an effector which could cause damage
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Describe how synapses control commnication along nervous system
Low-level action potentials amplified by summation, filter out low level signals, ensure potentials sent in one direction, spatial summation can show several different stimuli are warning us of danger, strengthening of specific pathways is thought
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Other cards in this set
Card 2
Front
What are Pacinian Corpuscles
Back
Pressure sensor that detects changes in pressure on the skin. Series of rings of connective tissue around a nerve ending, so pressure deforms rings pushing against nerve ending
Card 3
Front
Why does Myelination increase rate of action potential remission
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