What in the neurone receive inputs from other neurones and convey graded electrical signals passively to the soma?
dendrites
What is the synthetic and metabolic centre of the neurone?
soma (perikaryon)
What is the site of initiation of the ‘all or none’ action potential?
Axon hillock and initial segment
What contains the nucleus, ribosomes, mitochondria and endoplasmic reticulum (ER; rough ER is Nissl substance), and integrates incoming signals that are conducted passively to the axon hillock?
Soma (perikaryon)
What is the point of chemical (usually) communication between neurones (or other cells)?
synapse
What conducts output signals as action potentials to other neurones (or other cells), and mediates transport of materials between the soma and presynaptic terminal (anterograde direction) and vice versa (retrograde direction)?
Axon
What may exploit retrograde transport to infect neurones (often with devastating effect)?
several viruses, eg polio, herpes and rabies
Neurones can be defined by shape (how many processes (neutrites) come off of the main body (soma). What is a Peripheral autonomic
neurone shape?
unipolar
What is a Dorsal Root Ganglion (DRG) neurone shape?
Pseudounipolar (one neurite, that bifurcates)
What is the shape of a Retinal bipolar neurone?`
bipolar (two neurites)
What is the shape of a Lower motor neurone (LMN)
(motoneurone)?
multipolar
What allowed the visualisation of individual neurones?
Golgi’s staining method
What type of neurone may come from ventral horn of spinal cord to skeletal muscle?
motor
What neurone type may come from skin to dorsal horn of spinal cord?
sensory
What neurone type may come from between neurones in CNS?
Local Interneurone
Which neurone type has a Short axon: Golgi type II?
Local Interneurone
Which neurone type has a Long axon: Golgi type I?
Projection Neurone
What neurone type may come from dorsal horn of spinal cord to brain structures?
projection neurone
Action potentials allow signals to travel long distances without decaying. Why is passive (non action potential signals) transmission leaky/ineffective for long distances?
The nerve cell membrane is ‘leaky’ (i.e. not a perfect insulator): passive signals do not spread far from their site of origin due to current loss across the membrane
What happens to the membrane potential change in a passive neuronal process with distance?
decays exponentially with distance. λ= length constant
The distance over which current spreads depends upon what?
membrane resistance (rm) and the axial resistance of the axoplasm (ri) (increasing the ratio rm/ri increases λ)
If the length constant (λ) is longer, is the local current spread greater or smaller?
greater
How can Rm be increased?
by adding an insulating material
How can Ri be increased?
possible by increasing axon diameter
What insulating materials can be added to increase Rm?
in PNS: myelin provided by Schwann cells
in CNS: oligodendrocytes
Is conduction faster in myelinated or non myelinated cells?
MYELINATED
True or false: one oligodendrocyte surrounds many axons
true
What is “Saltatory Conduction in Myelinated Axons”
The action potential ‘jumps’ from one node of Ranvier to the next
Demyelinating disorder in PNS?
multiple sclerosis
Demyelinating disorder in CNS?
Guillian-Barre Syndrome
Most common type of synapse?
Axodendritic
What are the major amino acid neurotransmitters in the CNS?
Glutamate, GABA and glycine
Synapses can be classified functionally as being what two things?
excititory or inhibitory
In the CNS, what is the EXCITATORY transmitter most frequently?
glutamate
In the CNS, what is the INHIBITORY transmitter most frequently?
GABA or glycine
What does glutamate activate, generating what kind of response?
postsynaptic, cation selective, ionotropic, glutamate receptors
This generating a local, graded, excitatory (depolarizing) response: the excitatory postsynaptic potential (e.p.s.p.)
What does GABA, or glycine, activate, generating what kind of response?
postsynaptic, anion selective, ionotropic, GABAA, or glycine, receptors generating a local, graded, inhibitory (hyperpolarizing) response: the inhibitory postsynaptic potential (i.p.s.p.)
What separates pre and post synaptic membranes?
synaptic cleft
What stores the neurotransmitter in the synapse?
vesicles
Physiologically, spatial and temporal summation - are these isolated or complementary processes?
complementary
Name the amine neurotransmitters.
ACh, Dopamine, Histamine, Noradrenaline, Serotonin
Name the peptide neurotransmitters.
CCK, Somatostatin, Substance P, TRH, VIP, Neuropeptide Y, Enk, Dynorphin
Amino acids and amines are released from where?
synaptic vesicles
Peptides are released from where?
secretory vesicles
What are LGICs and what can activate them?
Glutamate, GABA, glycine, acetylcholine, and 5-HT can activate ionotropic ligand-gated ion channels (LGICs). These mediate fast neurotransmission
Which neurotransmitters can also activate metabotropic G protein-coupled receptors, which mediate relatively slow neurotransmission?
all except glycine
In which cells do Glycine and glutamate occur?
all (not just neurones)
Which neurotransmitters must be specifically synthesized by the neurones that release them, requiring specific enzymes?
GABA and amines
How are Enzymes are synthesized in the cell body and are transported to the presynaptic terminal?
by axoplasmic transport along microtubules
Where do enzymes mediate synthesis within the cytoplasm of neurotransmitter from precursor substances?
at the terminal
What synthesises the precursor peptide?
ribosomes associated with the rough endoplasmic reticulum (ER)
Where does Cleavage of precursor peptide occur?
Golgi apparatus
What bud off from the Golgi apparatus?
secretory granules
How are secretory granules are transported to the presynaptic terminal?
by fast axoplasmic transport via microtubules