What is the nervous system made from ?
made of specialised cells called neurons . They send electrical and chemical signs through brain and body .
What are the parts of a neuron
- Soma : houses the nucleus
- Dedrites : receive signals from other neurons
- Axon : conducts messages away from the soma
What is the nerve and glacial cell
- A nerve is an enclosed bundle of axons
- Glacial cells support and nourish neurons
- Myelin is a fatty layer which surrounds many axons .
What is the gray matter and the white matter ?
Soma and dendrites form grey matter
Axons form white matter
What sensory neurons receive ?
signals from sense organs
What motor neurone send ?
it send signals to muscle cells
What interneurons connect
connect neurons to other neurons
Describe resting potential
- Outside has more Na+ and Cl- ions
- Inside has more K+ and protein anions
- Sodium -potassium pump transports K+ into the cell and the Na+ out of the cell.
- The resting potential is about -70 millivolts (mV)
Describe action potential
- Electrical stimulation can cause sodium channels to open
- Na+ ions flow into the cell
- The voltage shifts form -70mV to + 40 mV in about 1 millisecond
Describe resting potential restarted
- Sodium channels close
- Potassium channels open
- K+ ions flow out of the cell
- The K + channels close and the sodium - potassium pump restores the resting potential .
what are the key points about action potentials
- Action potential are all or none
- must threshold to trigger an action potential
- graded potential can combine to trigger an action potential
Explain action potential process
nearby Na+ channels open , the signal flows along the axon .
While K+ ions flows out , membrane is not excitable
SO
flow is unidirectional
and the firing rate limited to 200-300 per second
What is myelination
- Myelin insulates axons
- The signals jump from node to node , this allows faster transmission
- Loss of myelin can cause health problems
What is a synaptic transmission ( define 5 steps )
Neurotransmitters are chemicals which carry signals across synaptic cleft
Five steps
1. synthesis
2.storage
3.release
Explain the process of binding neurotransmitters
Each neurotransmitter binds to specific receptors
Excitatory neurotransmitters cause Na channels to open
Inhibitory neurotransmitters cause K= to flake out or Cl- to flow in
Explain the process of deactivation
the neurotransmitter is broken down in synaptic cleft
The re-uptake happens in the pre-synaptic cell
explain the process of contraction with acetylcholine
- Binding trigger flow of of sodium ions into muscle cells
explain the process of paralysis with acetylcholine
Botulinum toxin blocks synaptic release
What is the process convulsions with acetylcholine ?
Black window venom triggers massive release .
In which part of the body is ach important ?
for memory and it underproduced in Alzheimer disease
