specialised tissues Flashcards
nerve: list cell types within the nervous system, recall their functions and explain processes of intercellular communication; recall the components of a neurone and explain how function is conveyed by generation of the resting membrane potential
nerve cell types
neurones, neuroglia (astrocytes, oligodendrocytes incl. Schwann, microglial, ependymal)
neurone: defining characteristics
excitable, non-dividing
neurone: projections
all have projections from cell body but only 1 axon
neurone: unipolar
rare, 1 single axonal projection from soma
neurone: pseudo-unipolar
1 axonal projection from soma which divides into 2
neurone: bipolar
2 projections from cell body (axon and dendrite)
neurone: multipolar
most common, 1 axon and multiple dendrites
multipolar neurone examples
pyramidal, Purkinje, Golgi
common neuronal features
soma containing nucleus, ribosomes and neurofilaments, axon, dendrites
axon
long process from soma at “axon hillock”; branch off into “collaterals”; usually covered in myelin; send signals away from soma
dendrites
highly branched; not myelinated; receive signals and deliver to soma
astrocytes
most abundant; able to proliferate; maintain blood-brain barrier; main role in water movement; structural and cell repair; immune cells; maintain homeostasis (neurotransmitter release and uptake)
oligodendrocytes
variable morphology and function; produce myelin (one cell myelinates many axons); in PNS called Schwann and one cell only myelinates one axon
microglial
CNS immune cell
ependymal
line fluid-filled ventricles and produce cerebrospinal fluid
CNS anatomy
cerebral cortex, brain stem, cerebellum, spinal cord
cerebral cortex
frontal, parietal, temporal and occipital (convoluted surface - gyri ridges and sulci valleys); most visible
brain stem
midbrain, pons and medulla (target/source of all cranial nerves)
cerebellum
motor coordination
spinal cord
down medulla; conduit for neural transmission
synapse: process
action potential arrives → Ca2+ influx → vesicles move and fuse to plasma membrane → neurotransmitter released by exocytosis → diffuse through cleft → bind to post-synapse receptors → action potential produced in next neurone → neurotransmitter dissociates → broken down in cleft by enzymes/recycled back into neurone by transporter proteins
what does neurotransmission rely on
membrane impermeability to ions
distribution of ions at resting membrane potential
Na+ Cl- and Ca2+ greater EC; K+ greater IC; membrane potential concentrated around membrane
neurone resting potential
-70mV; always compared to outside of cell; negative charge IC vs EC; -40mV (more excitable) to -90mv (less excitable); hyperpolarised to 0mv
define non-decremntal
size of action potential maintained throughout transmission
neurone resting potential: voltage-gated channels
Na+ and K+ channels are closed
action potential: process
membrane depolarised → Na+ channel opens → Na+ influx → depolarisation → K+ channel opens at slower rate → K+ eflux → repolarisation
how is the imbalance of ions restored after an action potential
Na+/K+ATPase pump: at rest, Na+ in vestibule → ATP phosphorylates → active transport of Na+ out → K+ in vestibule → return to rest as K+ in
saltatory conduction
action potential via cable transmission; jumps at nodes of Ranvier; speeds up transmission of action potential
nodes of Ranvier properties
small gaps of non-myelinated axon; high conc. of Na+ and K+ channels
