NBSS (neuroscience) Cellular Structure of the Nervous System Flashcards
how can neurons be described?
polarised (morphologically and functionally)
what are neurons made up of?
axon terminal, dendrites, soma
what does polarised mean?
information carried via electrical charges as sodium ions are pushed out of cell and potassium ions in
what is the resting potential?
-70mv
how much of the brains energy is consumed to maintain resting potential?
60%
over how many mm does the dendritic signal decay?
1-2mm
where is voltage gated sodium channel activated at
-50mV
what 4 things describes how information is carried in axon hillock?
unidirectional
all-or-nothing principle
non-decaying
carried at same amplitude
what type of neurones have two firing modes?
thalamocortical
what is an electrical synapse?
formed by gap junctions where current carried by ion transfer directly through channels - ‘coupled’
minimal delay
bidirectional
what is a chemical synapse?
Physical gap between two junctions, presynaptic neurotransmitters diffuse across to postsynaptic receptors
unidirectional
delay of 0.3-0.5mSec
what are 3 neurotransmitter types?
- biogenic amines
- amino acids
- peptides
what are examples of biogenic amines neurotransmitters?
- acetylcholine
- noradrenaline
- adrenaline
- dopamine
- serotonin
what are examples of amino acid neutransmitters?
- glutamate
- aspartate
- g-aminobutyric acid
- glycine INHIBITIORS VIA HYPERPOLARISATION
what are example of peptide neurotransmitters?
- somatostatin
- endorphins
- dynorphins
- bradykinin
- enkephalins
- substance P
what are other examples of neurotransmitters?
- ATP
- nitric oxide
what does axosomatic mean
cell body
what does axodendritic mean
dendrite
what is axoaxonic
single axon terminal
where are motor neurones found
motor neurons are in ventral
(anterior) “horn”
motor neurons control what? and what are they described as being
motor control our muscles and are
efferent
sensory cells project into what?
Sensory cells project into dorsal (posterior) ”horn” from ganglia
how are sensroy neurons described as
afferent
how many layers of cortex are there?
5
which layer has the largest cell bodies?
5
how do motor axons exit the CNS?
efferently - moves away from
how do peripheral sensory neurons exit the CNS?
afferently - moves towards
pre ganglionic neurones control what?
post-ganglionic
neurons
what do autonomic ganglion do?
efferently transmit sensory signals in both the parasympathetic and sympathetic nervous system controlling acitivty of smooth muscle contractions and secretions
what speeds up neurone communication?
myelination
how does myelination speed up communication?
myelin layers wrapped around axons acting as layer of insulation for action potential transmission across nodes of ranvier with voltage gated sodium ion channels = saltatory conduction
what does damage to myelination do? what is this called?
conduction speed slows down or is prevented
demyelinating disease: multiple sclerosis, extreme = paralysis
what are white matter filled with?
myelinated axons
what are grey matter filled with?
cell bodies, dendrites, axons
what is the difference in grey and white matter in brain and spinal cord?
- brain: grey matter external, white matter internal
- spinal cord: white matter external, grey matter internal
what are the 5 glial cell types
oligodendrocytes (CNS)
Schwann cells (PNS)
microglia
astrocytes
radial glia
whats the function of:
oligodendrocytes (CNS)
Schwann cells (PNS)
Deposit myelin
what are microglia described as being
phagocytic
what is the function of astrocytes
- homeostatic function: blood vessel/brain interface linking metabolism to function
- refine signalling: remove excess K+ at mylein gaps, remove synaptic neurotransmitter and insulate synapse
what is the function of radial glia
they are long and thin, stretching from brain surface to inner luminal surface - structural support of adult nervous system and development of NS
where are cells born?
inner ventricular suface
where do CNS cell types migrate to?
overlying mantle
where are motor neurons formed?
ventral
where are sensory neurons formed?
dorsal
what is the nerual tube formed by?
dorsal closure
what does cell type made depend on?
where in the neural tube they are positioned: dorsoventral position gives types
what is the origin of peripheral nervous system (PNS) neurons?
nerual crest populates PNS
what is an example of a neuronal defect
Neurulation defects range from spinabifida to a complete loss of head (anencephaly)
