Nervous System Flashcards
Nerve impulse
Neurons communicate with one another by action potentials, also called nerve impulses
Involves a specific sequence of events in the cell membrane
Changes in the membrane potential caused by opening and closing of protein channels in respond to stimulus (causes a change in ion concentration)
Rapid change in polarity across axon membrane
Resting membrane potential
Not having a nerve impulse
Cell membrane polarized because of voltage different cause by electrogenc pump (sodium potassium pulls out 3 Na and takes in 2 K)
inside of neuron is negatively charged, more K inside, more Na outside
All or none law
Either neuron has action potential or not, there is no middle ground.
To have action Pontiac, stimulus must be large enough to reach threshold, if not then there is no action potential
Difference between strength in feelings comes from number of neurons activated
Depolarization
Stimulus causes change in ion concentration which will change membrane potential
after chemical signal (neurotransmitter) of electrical signal, gated sodium Chanel to open, because of gradient (na concentration higher outside) and charge of cell (inside cell negative), sodium will rush in
If enough sodium gets in to reach threshold, voltage gated channels open and that’s depolarization, causes rapid change of concentration of sodium
Positive ions entering, getting more positives
Repolorizaton
At about +30, sodium channels close ne potassium channels open, so potassium leaves cell
Driven by gradient (more K inside) and charge (k positive, outside of cell less positive) K rushes out
Positive ions leaving, getting more negative
H goes on until it restores resting membrane potential, then closes and cycle continues
Cycle neuron
Resting neuron
Action potential:
Stimulus
Sodium channels open
Sodium enters neuron
Potassium channels open
Potassium leaves neuron
Charge restoration
Nerve aimpulse travels by repeated depolarization and depolarization along its length
How does an impulse travel along a nerve cell
Travels by repeated depolarization and repolarization along its length
Proceeds in one direction(from dendrite to tip of axon) because for a very short period after an action potential, the membrane is more difficult to stimulate, so there is a resting period called the refractory period
Brain glucose
Synthesis of glucose even if unnurished body is so sodium potassium pumps have atp
Synapse
Neurons do not touch each other of the effectors (glands, muscles)
Space between them is a synapse
Chemical or electrical transition at a synapse
Junctions
Electrical synapse
Found in the heart
Are here where things have to be very synchronized
Rare, fast
through gap junctions, transfer of ionic current occurs
Chemical synapse
From pre synaptic to post synaptic
Axon to dendrite
When arrives at the end bulb, voltage gated Ça+ chanels open (calcium enters) which activates enzyme that causes synaptic vesicles that by exocytosis release neurotransmitters the synaptic clefs which will attach to receptor sites and allow the flow of Na ions into neuron. If enough neurotransmitters are released, threshold will be reached
Central to peripheral nervous sytème
Central: Always just between neurons, second cell is a neuron
Peripheral: can be sent to neuron or effector cell
if second cell is a muscle, synapse is referred to as a neuromuscular junction
Excitatory synapse vs inhibitory
Excitatory: net effect of neurotramitter is to deporlarize, bringing membrane nearer to threshold, done by opening channels for sodium and calcium ions
Inhibitatory: net effect is to hyperpolarize, to move further away from threshold Typically Cl or K channels
absolute vs relative refractory period
absolute: during depolarisation and repolarisation, impossible to have another response
relative: after repolarization, can have another response if it is higher than threshold potention (when it membrane potential dips lower than resting membrane potential
