Neuroanatomy II Flashcards
(26 cards)
Dendrites are…
receiving area of a neuron
What happens at the axon hillock?
Action potentials received from dendrites are gathered and decided if there is going to be a response
Function of glia
Supports neuron
Sensory neuron adaptation
Have several dendrites but not too many in order to localise where stimulus is coming from
Motor neuron adaptation
Receive signals from many different dendrites telling it what its exact response will be and communicates this to a finite region
What do interneurons do?
- Receive and send out information
- Process information
Membrane potential
The voltage difference across the plasma membrane
Resting potential
Membrane potential of a neuron not sending signals
- Formed due to different ion concentrations intracellular and extracellular
- -70mV
Potassium concentration
Intra - 140
Extra - 5
Sodium concentration
Intra - 15
Extra -150
Chloride
Intra - 10
Extra - 120
Large anions e.g. Proteins
Intra - 100
How is resting potential maintained
- Na+/K+ pumps (ATPase)
- For every 3 Na + out, 2 K+ into cell
- Creates electrical gradient as well as chemical gradient
What happens at resting potential
K+ channels are open
- Net outflow due to chemical gradient (high to low conc. K+)
- Not all K+ flows out due to electric gradient ( positive charge of K+ attracted to negative charge inside the cell
Nernst equation
Eion = 62mV (log [inside]/[outside])
What does nernst equation tell you
There are more K+ channels than Na+ channels
How does an action potential occur?
- ) stimulus causes change in membrane potential
- ) Once threshold value (-55mV) is reached, voltage-gated Na+ channels open causing an influx
- ) Depolarisation occurs as all voltage-gated Na+ channels are open
- ) At +40mV Na+ channels deactivate. Voltage-gated K+ channels open causing an efflux
- ) Hyperpolarisation occurs
- ) There is an undershoot as membrane potential gpes below resting potential as K+ channels stay open for longer
What is the refractory period?
A second action potential cannot be initiated
Adaptations of an axon
- Greater the diameter, the faster the AP
- Myelinated neurons have a faster AP
Myelinated neurons
- Insulated by myelin sheath which is formed by oligodendrocytes in CNS and schwann cells in PNS
- Voltage-gated Na+ channels are located at nodes of Ranvier
- Action potentials jump from one node to the next
SALTATORY CONDUCTION
Synapses in the brain
- Chemical synapses
EPSP
Excitatory post synaptic potentials cause depolarisation and bring about an AP
IPSP
Inhibitory postsynaptic potentials cause hyperpolarisation
Temporal summation
Two EPSPs produced in rapid succession at the same synapse
