Cells and Communication Flashcards
What are the 3 functions of the nervous system?
Sensation
Integration
Activation
What 2 things does the function of the nervous system depend on?
Anatomical relationship between neurons
- axon length
- receptive fields
- how many neurons
Interactions between neurons
- mode of communication
- chemical phenotype
- how many transmitters
- receptor density
What 5 things can cause dysfunction of the nervous system?
Damage by trauma or disease
Neurons lose ability to produce transmitters
Neurons over/under-produce transmitters
Neurons fail to recognise transmitters
Effector organs fails to respond
What 3 things can nervous system dysfunction manifest as?
Loss: sensation or function
Gain: appearance of a new feature
Change: alteration in behaviour/personality of perception
What are the 2 types of cells in the nervous system?
Neurons
Glia
What are the 2 types of neurons?
Principal cells
Interneurons
What are the 5 types of glia?
Astrocytes Ependymal cells Microglia Oligodendroglia Schwann cells
Which cell type is most likely to form tumours?
Glia
What are the 3 main groups of neurons?
Multipolar
Bipolar
(Pseudo) unipolar
What are the 4 common features of neurons?
Dendrites
Soma
Axon
Synaptic terminals
What is a dendrite?
The receptive field of the neurones, sensitive to neurotransmitter input
What is a soma?
The metabolic and integrating centre of the neurone
What is an axon?
Rapid one-way communication between cell body and terminals
What is a synaptic terminal?
Release transmitters and communicate with other cells in a pathway or circuit
Describe astrocytes
Star-shaped cells which form a bridge between the neuron and blood vessels
Describe ependymal cells
Simple, ciliated, cuboidal cells that form the lining of the ventricular system
Describe microglia
Small glial cells, activated by trauma.
WBC for CNS, act by phagocytosis
Describe oligodendroglia
Myelin producing cells, found in the CNS
Describe Schwann cells
Myelin producing cells, found in the PNS
What disorder of myelination affects the CNS?
Multiple Sclerosis
Oligodendroglia
What disorder of myelination affects the PNS?
Guilian Barre
Schwann cells
Why are nerve impulses quicker along myelinated axons?
Action potentials jump the gaps
What are the 2 types of synapses?
Chemical
Electrical
Describe chemical synapses
Fast transmission (slower cell-cell, but can cope with higher frequency of activity)
Vesicles releases from presynaptic terminal
Act on receptors in postsynaptic terminal
Major drug target
Describe electrical synapses
Slower transmission (faster cell-cell, but more effective at lower freqs)
Gap junctions
Small molecules and current
‘low-pass filter’
Synchrony
Up-and-coming drug target
What type of synapses have gap junctions?
Electrical synapses
Outline the 5 steps that occur at a neuromuscular junction
Action potentials trigger the exocytosis of acetylcholine (ACh) from the synaptic terminal
ACh crosses the cleft
Acts on (nicotinic) cholinergic receptors in the motor end plate
Initiates muscle contraction
Impulse carried through muscle via T-tubules and sarcoplasmic reticulum
What is myasthenia gravis?
Autoimmune disease affecting the NMJ. Circulating antibodies block Ach receptors, slowing muscle activity and reducing tone. Receptors don’t respond as well
How do you test for myasthenia gravis?
Nerve conduction tests
Electromyography
What is the major excitatory transmitter?
Glutamate
What is the major inhibitory transmitter?
GABA
Why is inhibition essential?
Otherwise a cell will fire at its own rate and not send a coded message to the next cell
What 3 types of cell inhibition are there?
Direct inhibition
Lateral inhibition
Disinhibition
Describe direct inhibition
Excitatory neurons have regular patterns of firing in absence of inhibition
Inhibition sculpts the firing into a coded pattern which can be read by the brain
Describe lateral inhibition
Activation of excitatory cells also activates associated inhibitory cells
Inhibition acts on neighbouring cells to reduce activity
Strengthens response of cell directly stimulated
Where is lateral inhibition usually seen?
Sensory pathways:
- vision
- touch
- olfaction
Describe disinhibition
Activation of inhibitory circuit leads to excitation
Pivotal role in Basal Ganglia circuitry – shapes motor function
What does synchrony do?
Change the strength of the signal and the network level
Measured via EEG
There are pacemaker cells
What is plasticity?
Up or down regulation of synaptic strength
What are the 4 types of plasticity?
LTP and LTD
Synaptic morphology
Metabolic changes
Subunit changes
Describe neurotransmitters (8)
Used by neurons for rapid cell-cell communication
Stored in vesicles in the presynaptic terminal
Released when the terminal is depolarised during an AP
Pass across the synaptic cleft
Activate receptors on the postsynaptic terminal
Binds to receptor
Excitatory propagates the signal onward
Inhibitory blocks onward propagation
Describe neuromodulators (4)
Found in vesicles (or not), co-localised with NT
Act on receptors or membranes to indirectly alter neuronal activity
Changing sensitivity or kinetics of NT receptor
Also act on glial cells
Which neurotransmitter is affected in Parkinson’s disease?
Dopamine
Which neurotransmitter is affected in Alzheimer’s disease?
ACh
Which neurotransmitter is affected in Alzheimer’s disease?
ACh
Which neurotransmitter is affected in Huntington’s disease?
GABA
What are the 2 types of receptors in the nervous system?
Ionotropic (linked to ion channels)
Metabotropic (GPCR)
Receptors are transmitter specific
What are the four main types of cutaneous receptors?
Mechanoceptors - tactile sensation e.g. touch, pressure
Thermoceptors - temperature
Nociceptors - painful/noxious stimuli
Proprioceptors - changes in head and body position
What mechanisms are involved in pathogenesis of neuronal and psychological disorders?
Altered neuronal activity
Altered synchrony
Cellular changes
Subcellular change
Genetic/Epigenetic changes
