Nervous System - Nervous Cells, Synapses, Neurotransmitters Flashcards
main cells of the nervous system (2)
- neuron (nerve cell)
2. glial cell (neuroglia)
neuron (nerve cell) vs glial cel (neuroglia)
- nervous cell vs supporting cell
- conductive cell vs non-conductive cell
- structural/ functional unit vs major part of nervous system
where does information converge on the neuron
soma
“all or none”
action potential will either fire or not :0
soma
cell body
dendrites
processes that gather sensory information
axon
- process that conveys excitation to other neurones or effector cells
- often branch at end, causing a divergence of output
axon hillock
region where action potential is generated
Nodes of Ranvier
facilitate the rapid conduction of nerve impulses
myelin sheath
protect and insulate axons and enhance transmission of electrical impulses
structural criteria of neurons
look at photos!
functional criteria of neurons
- afferent (sensory)
- association (interneurons)
- efferent (motor)
afferent structure and function
- dendrites and cell body within the PNS, axons extend into CNS
- transmit impulses from peripheral sense receptors to CNS
association structure and function
- located entirely within CNS
- sensory-motor integration
efferent structure and function
- dendrites and cell body within CNS, axons extend to PNS
- transmit impulses from CNS to effectors in periphery
glial cells (neuroglia)
- don’t conduct nerve impulses
- support, nourish, and protect neurons
- outnumber nerve cells (10x)
- capable of mitosis (cell division)
glial derived from what?!
Greek word “glia” (“glue”)
glial cells in CNS (4)
- ependymal
- oligodendroglial
- astrocyte
- microglia
ependymal cells
- line surface of ventricles and produce/circulate CSF
oligodendroglial cells
- form myelin sheath in the CNS
- usually each cell forms sheath of several axons
astrocytes
- bind blood vessels to nerves
- help form the blood-brain barrier: take up ions and neurotransmitters
microglia
- originate in the blood
- enter the brain and become phagocytic in response to inflammation
blood-csf barrier
- “barrier that separates blood from CSF and CSF from brain tissue”
- choroid plexuses produce CSF
- choroid plexuses consist of ependymal cells
- CSF contains less protein and different ion concentrations than plasma (almost cell free)
function of myelin? how is it produced?
- insulates the axon and increases action potential conduction velocity
- formed by Schwann cells
where are Schwann cells located
PNS!
motor neurons disease
Amyotrophic Lateral Sclerosis
disease associated with atrophy of basal ganglia (caudate and putamen)
Huntington’s Disease
disease associated with axon demyelination in brain and spinal cord
Multiple Sclerosis
disease associated with atrophy of frontal and temporal cortex
Alzheimer’s Disease
disease associated with decreased number of dopaminergic neurons in basal ganglia
Parkinson’s Disease
main functions of neuron (2)
- excitability
2. conductivity
excitability
- respond to a stimulus
- produce an electrical signal (action potential)
conductivity
- provide a fast way for an impulse to travel from one point to another
- conduct an electrical signal (action potential)
action potential
- pulse-like change in membrane potential
- moves along surface of excitable cells
- fastest way to convey a signal in the body
generation of an action potential
see graph image
absolute refractory period
impossible to send another action potential
relative refractory period
hard to send action potential
synapses
- communication between two cells
- apposing the axonal end feet of one cell to the membrane of another cell
pre-synaptic cell
cell sending message
post-synaptic cell
cell receiving the message
types of synapses
- chemical synapses
2. electrical synapses
chemical synapse vs electrical synapse
- gap between pre-synaptic and post-synaptic membranes vs appear to be fused
- transmission is unidirectional vs bidirectional
chemical synapse components
- presynaptic knob: contains neurotransmitter vesicles
- synaptic cleft: gap between cells
- postsynaptic knob: contains receptors
mechanism of neurotransmission
- action potential enters the presynaptic terminal, depolarization opens voltage gated Ca2+ channels, entry of Ca2+ causes synaptic vesicles to fuse with the presynaptic terminal
- Ca2+ binds to synaptotagmin causing opening of fusion pore, chemical neurotransmitter is rebased into the synoptic cleft
- neurotransmitters bind to postsynaptic receptors, signal is initiated in the postsynaptic cell
mechanism for shut off of neurotransmission
- destruction of the NT by degradative enzymes
- diffusion of the NT away from the post-synaptic receptors
- re-uptake of the NT either by the presynaptic terminal or by other cells
mechanism of vesicle recycling
- kiss and run
2. full-collapse fusion
classification of neurotransmitters (4)
- amino acids
- monoamines
- neuropeptides
- choline esters
amino acids
gamma-aminobutyric acid (GABA), glutamate, glycine
monoamines
dopamine, norepinephrine, epinephrine, histamine, serotonin
neuropeptides
opioids (endorphins), hypothalamic peptides
chlorine esters
acetylcholine (Ach)
membrane receptors
- ionotropic
2. metabotropic
ionotropic receptors
- ligand-gated ion channels
- open/close gated ion-channels
- short latency and rapid responses
metabotropic receptors
- G-protein-coupled receptors
- indirectly linked with ion channels
- act on G protein coupled receptors
- second messenger involvement (cAMP, IP3)
- longer latency and slow response
acetylcholine receptors
- nicotinic receptors: ionotropic
- muscarinic receptors: metabotropic
- neurotransmitter: acetylcholine
adrenergic receptors
- alpha (a1, a2) receptors: metabotropic
- beta (B1, B2) receptors: metabotropic
- neurotransmitter: norepinephrine/ epinephrine
