1. More K+ ions inside the cell and more Na+ out of the cell.
2. (Using ATP), Na+/K+ oumos can AT both ions accross the membrane.
3. 3Na+ out of cell for every 2K+ into cell.
4. Membrane is more permeable to K+ so many diffuse out of cell (leaky)
5. Maintains voltage of -60mV
The Refractory Period
1. Chance for cell to recover and restore the ion balance using the Na+/K+ pump.
2. Difficult for another AP to occor without cell recovery.
3. Ensures that APs are being trasmitted in 1 single direction.
The Mylinated Sheath
1. Mylinated sheath = fattym insulative material
2. Specilised cells = Schwaan cells
3. Sheath prevents the diffision of ions, so transmission of ions consists by "jumping" from 1 node of Ranvier to another = SALTATORY CONDUCTION
4. Local current is also elongated to ensure ions "jump"
5. Reduces distance travelled by ions therefore APs = faster
1. AP arrives at synaptic knob of the pre-synpatic neurone.
2. Triggers the Ca2+ v.g.c to open causing Ca2+ to diffuse in.
3. Influx of Ca2+ causes vesicles of ACETYCHOLINE to duse with the presynaptic membane.
4. Via exocytosis, ACETYLCHOLINE is released into the synaptic cleft, which diffuses down the concentration gradient and into the post-synpatic membane.
5. ACETYLCHOLINE binds to its receptors on the Na+ channels causing channels to open and letting the Na+ to diffuse in.
6. Influz of Na+ triggers the AP as normal.
1. Acetylcholine is broken down with ACETYLCHONESTERASE
2. products are recycled
3. If not, effective endless nerve impulses -> paralysis or eventually death due to ASPYXIATION
Roles of the Synapse
1. Convergence: signals from different parts of the central part, can trigger the same response.
2. Divergance: Allows a signal to be transmitted from 1 neurone to several areas simultanseously.
3. Allows movememt of signal in one direction
4. Low level signals can be amplified with summation
5. ACCLIMITISATION: neurones run out of vesicles and become fatigued preventing overstimulation
BIGGER SIGNALS DEPEND ON THE INTENSITY OF STIMULUS AND THE FREQUENCY OF AP TRANSMISSIONS.
1. every receptor of Adrenaline has an enzyme ADENYL CYCLASE
2. Adrenaline = 1st messenger; from blood binds to the crecptor on target tissue, activating ADENYL CYCLASE
3. ADENYL CYCLASE: converts ATP-> cAMP
4. cAMP= 2nd messenger and actvates a cascade of enzyme controlled reactions.