The Nervous System
- Created by: Labake
- Created on: 10-11-14 14:40
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- The Nervous System
- The Resting Potential
- Initially, the inside of the neurone is negatively charged (-65mV)
- At rest, the voltage gated channels are closed.
- The sodium-potassium pump actively transports 3Na+ out of the axon for every 2K+ that are pumped into the axon
- This sets up a concentration gradient and causes Na+ to diffuse into the axon and K+ to diffuse out of the axon by their respective channels
- K+ diffuses 50x faster than Na+ because there are 50x more K+ channels
- The outside of the axon is now positive with respect to the inside
- The membrane is said to be polarised
- The Resting Potential
- Initially, the inside of the neurone is negatively charged (-65mV)
- At rest, the voltage gated channels are closed.
- The sodium-potassium pump actively transports 3Na+ out of the axon for every 2K+ that are pumped into the axon
- This sets up a concentration gradient and causes Na+ to diffuse into the axon and K+ to diffuse out of the axon by their respective channels
- K+ diffuses 50x faster than Na+ because there are 50x more K+ channels
- The outside of the axon is now positive with respect to the inside
- The membrane is said to be polarised
- The membrane is said to be polarised
- The outside of the axon is now positive with respect to the inside
- K+ diffuses 50x faster than Na+ because there are 50x more K+ channels
- This sets up a concentration gradient and causes Na+ to diffuse into the axon and K+ to diffuse out of the axon by their respective channels
- The sodium-potassium pump actively transports 3Na+ out of the axon for every 2K+ that are pumped into the axon
- At rest, the voltage gated channels are closed.
- Initially, the inside of the neurone is negatively charged (-65mV)
- The Resting Potential
- The membrane is said to be polarised
- The outside of the axon is now positive with respect to the inside
- K+ diffuses 50x faster than Na+ because there are 50x more K+ channels
- This sets up a concentration gradient and causes Na+ to diffuse into the axon and K+ to diffuse out of the axon by their respective channels
- The sodium-potassium pump actively transports 3Na+ out of the axon for every 2K+ that are pumped into the axon
- At rest, the voltage gated channels are closed.
- Initially, the inside of the neurone is negatively charged (-65mV)
- Action Potential
- The depolarisation of the cell membrane- inside more positive than outside- potential diff. of +40mV
- Transmitted along the axon/ dendron plasma membrane
- Resting neurone= negatively charged- Active neurone= positively charged
- Neurones' charge increases to +40mV= Action potential
- A stimulus causes the Na+ channels to open and an Na+ diffusion into the neurone
- If the stimulus is strong enough, a threshold is reached and the Na+ voltage gated channel opens= Na+ diffusion into neurone
- The inside of the neurone becomes more positive
- Known as Depolarisation
- Action Potential
- The depolarisation of the cell membrane- inside more positive than outside- potential diff. of +40mV
- Transmitted along the axon/ dendron plasma membrane
- Resting neurone= negatively charged- Active neurone= positively charged
- Neurones' charge increases to +40mV= Action potential
- A stimulus causes the Na+ channels to open and an Na+ diffusion into the neurone
- If the stimulus is strong enough, a threshold is reached and the Na+ voltage gated channel opens= Na+ diffusion into neurone
- The inside of the neurone becomes more positive
- Known as Depolarisation
- Known as Depolarisation
- Voltage gated channels allow passage of ions and respond to changes in potential difference across the membrane
- Threshold potential across membrane is -50mV, if this is not achieved the depolarisation doesn't occur
- The inside of the neurone becomes more positive
- If the stimulus is strong enough, a threshold is reached and the Na+ voltage gated channel opens= Na+ diffusion into neurone
- A stimulus causes the Na+ channels to open and an Na+ diffusion into the neurone
- Neurones' charge increases to +40mV= Action potential
- The depolarisation of the cell membrane- inside more positive than outside- potential diff. of +40mV
- Action Potential
- Known as Depolarisation
- Voltage gated channels allow passage of ions and respond to changes in potential difference across the membrane
- Threshold potential across membrane is -50mV, if this is not achieved the depolarisation doesn't occur
- The inside of the neurone becomes more positive
- If the stimulus is strong enough, a threshold is reached and the Na+ voltage gated channel opens= Na+ diffusion into neurone
- A stimulus causes the Na+ channels to open and an Na+ diffusion into the neurone
- Neurones' charge increases to +40mV= Action potential
- The depolarisation of the cell membrane- inside more positive than outside- potential diff. of +40mV
- Repolarisation
- Na+ channels close and K+ channels open
- K+ begins to diffuse out of the membrane and the inside of the neurone becomes more negative
- The Na+/K+ pump restores the resting potential
- Repolarisation
- Na+ channels close and K+ channels open
- K+ begins to diffuse out of the membrane and the inside of the neurone becomes more negative
- The Na+/K+ pump restores the resting potential
- The Na+/K+ pump restores the resting potential
- K+ begins to diffuse out of the membrane and the inside of the neurone becomes more negative
- Na+ channels close and K+ channels open
- Repolarisation
- The Na+/K+ pump restores the resting potential
- K+ begins to diffuse out of the membrane and the inside of the neurone becomes more negative
- Na+ channels close and K+ channels open
- Hyperpolarisation
- The potential diff. dips below -60mV for a short time as the K+ channels close
- The resting potential of -40mV is then restored
- Hyperpolarisation
- The potential diff. dips below -60mV for a short time as the K+ channels close
- The resting potential of -40mV is then restored
- The resting potential of -40mV is then restored
- The potential diff. dips below -60mV for a short time as the K+ channels close
- Hyperpolarisation
- The resting potential of -40mV is then restored
- The potential diff. dips below -60mV for a short time as the K+ channels close
- Local Currents
- Action potentials are self-perpetuating- continues down neurone
- Na+ ions diffuses onto neurone when the Na+ channels open
- A localised increase in conc. of Na+ ions inside neurone= Action Potential
- Na+ diffuses down its concentration gradient along the length of the neurone= local current
- As Na+ diffuse, voltage gates channels open and allow Na+ influx
- Na+ influx sets up action potential
- Local Currents
- Action potentials are self-perpetuating- continues down neurone
- Na+ ions diffuses onto neurone when the Na+ channels open
- A localised increase in conc. of Na+ ions inside neurone= Action Potential
- Na+ diffuses down its concentration gradient along the length of the neurone= local current
- As Na+ diffuse, voltage gates channels open and allow Na+ influx
- Na+ influx sets up action potential
- Na+ influx sets up action potential
- As Na+ diffuse, voltage gates channels open and allow Na+ influx
- Na+ diffuses down its concentration gradient along the length of the neurone= local current
- A localised increase in conc. of Na+ ions inside neurone= Action Potential
- Na+ ions diffuses onto neurone when the Na+ channels open
- Action potentials are self-perpetuating- continues down neurone
- Local Currents
- Na+ influx sets up action potential
- As Na+ diffuse, voltage gates channels open and allow Na+ influx
- Na+ diffuses down its concentration gradient along the length of the neurone= local current
- A localised increase in conc. of Na+ ions inside neurone= Action Potential
- Na+ ions diffuses onto neurone when the Na+ channels open
- Action potentials are self-perpetuating- continues down neurone
- Saltatory Conduction in Myelinated Neurones
- For quicker conduction of action potentials
- Myelin Sheath is Schwann cells- electrically insulating
- Action potential can only be set up at nodes of Ranvier
- Action Potential skips over large sections of neurone= faster conduction 120m s-1
- Saltatory Conduction in Myelinated Neurones
- For quicker conduction of action potentials
- Myelin Sheath is Schwann cells- electrically insulating
- Action potential can only be set up at nodes of Ranvier
- Action Potential skips over large sections of neurone= faster conduction 120m s-1
- Action Potential skips over large sections of neurone= faster conduction 120m s-1
- Action potential can only be set up at nodes of Ranvier
- Myelin Sheath is Schwann cells- electrically insulating
- For quicker conduction of action potentials
- Saltatory Conduction in Myelinated Neurones
- Action Potential skips over large sections of neurone= faster conduction 120m s-1
- Action potential can only be set up at nodes of Ranvier
- Myelin Sheath is Schwann cells- electrically insulating
- For quicker conduction of action potentials
- Features of a neurone
- Long- can carry action potential over long distance
- Gated ion channels on cell surface membrane
- Na+/K+ ion pumps using ATP
- Fatty myelin sheath (schwann cells) insulate neurone from electrical activity
- Nodes of Ranvier= gaps for saltatory conduction
- Motor neurones= cell body in CNS and long axon to carry action potential to effector
- Sensory Neurones have long dendron (receptor to cell body) and short axon (to CNS)
- Dendrites for connecting to other neurones
- Nerve Junctions
- SYNAPSE- junction between two or more neurones
- One neurone can communicate with another
- Synaptic cleft= 20nm wide
- Presynaptic neurone releases neurotransmitter (cholinergic = acetylcholine)
- Synaptic cleft= 20nm wide
- One neurone can communicate with another
- SYNAPSE- junction between two or more neurones
- The Resting Potential
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