Neurones Flashcards
what are neurones?>
cells that receive & transmit electrochemical signals
neurone structure (5)
- soma
- dendrities
- axon
- myelin sheath
- terminal buttons
neuron structure- soma> (function & structure)
function= where most metabolic processes in neuron occur
structure= contain cell nucleus (& thus most genetic material)
neurone structure- dendrities» (function )
- RECEIVES info
- where most connections are made between n & n transmitting info to
neurone structure- Axon»_space; (function)
where neural impulses are transmitted down
neuron structure: myelin sheath (function & strcuture) (4)
function= insulates axon, for quicker transmission & lack of info leakage
Structure=
- incrimental & contains gaps
- NOR for salatory conduction
- not all axons myelinated
Neurons structure- Terminal buttons (structure/function)
connect to dendrities/ cell body of receiving neuron (from past neuron)
Overall: neuron structure & function (3)
- specialised cells for reception, conduction & transmission of EC signals
- many shapes & sizes
- supported by glial cells
How neurons work (summary) (5)
1- electric potential in axon hillock (start of a), becomes more +ive, triggering AP (electrical impulse)
2- AP travels down axon> terminal buttons
3- Buttons release NT which travels across synapse> receptors on dendrities of receiving neuron
4- NT causes either excitatory (more +) or inhibitory (more -) potential in receving neuron
5- if sum of potentials is large enough another AP is generated
what does resting potential=
- outside cell has HIGHER conc of Na+ & LOWER conc of K+
- outside POSITIVELY CHARGED compared to inside
How does the Na+-K+ pump maintain resting potential>
- Transports 3Na+ out of neuron for every 2K+ in
The action potential (5)
1- stimulus
- when stimulated, Na+ channels open
- membrane becomes more permeable to Na+
- Na+ flood > neurone down EC gradient
2- Depolarisation
- PD reaches threshold (much more +) & AP formed (as more Na+ channels open so more Na+ diffuse > neurone until no more can (+30mv)
3- Repolarisation
- Na+ channels close while K+ channels open
- K+ diffuse out of axon
4- hyperpolarisation
- K+ channels are slow to close
- PD becomes slightly more - than RP
5- Return to RP
- After refractory period, K+ channels close & membrane returns to RP
What happens after depolarisation at one place in the axon?
- triggers opening of adjacent Na+ channels, causing AP to spread down axon
- if axon has myelin sheath, depolarisation jumps between nodes (SC)
- this speeds up transmission
synapse=
connection between neurons
Release of NT=
- Arrival of AP at terminal causes D, opening voltage-activated Ca2+ Channels
- Ca2+ diffuse> pre-SN causing vesciles to fuse with terminal membrane & release contents (NTs) into cleft
- NT diffuses across synapse & bind to receptors on post-s-m (iontropic receptors)
