Nervous System Flashcards
types of CNS synapses
axo-dendritic (most common): nerve A axon to nerve B dendrite
axo-somatic: nerve A axon to nerve B soma (cell body)
axo-axonic: nerve A axon to nerve B axon
dendro-dendritic: nerve A dendrite to nerve B dendrite
sensory neurons
-specialized cells or nerve endings located throughout the body
-detect and process sensory information
-afferent
order of information movement in CNS
- spinal cord
- pons and mesencephalon
- cerebellum
- thalamus
- cerebral cortex
the motor system controls…
-skeletal and smooth muscle
-secretion of active chemicals by exocrine & endocrine glands
integrative functioning
channelling and processing of information
communication role of synapses
amplify or dampen signals
integrate inputs from multiple neurons
shape the overall output of the postsynaptic neuron
functions of the spinal cord
-conduit for information
-spinal reflex arcs
-sensory integration
-proprioception
-basic locomotion
functions of the subcortical brain
-regulate fundamental physiological processes
-emotional responses
-motor control
-maintain overall homeostasis & survival
areas of the subcortical brain
medulla
pons
mesencephalon
hypothalamus
thalamus
cerebellum
basal ganglia
functions of the cortical brain
-wide range of cognitive functions
-sensory processing
-motor control
-memory
-language
-higher order thinking
-complex mental abilities and conscious
actions on nerve impulses
-blocked in transmission
-changed to repetitive impulses
-integrated with impulses from other neurons
chemical synapse
-no direct physical connection between pre and post-synaptic neurons
-neurotransmitters act on the post-synaptic neuron
-transmitter vesicles and mitochondria are key
-one-way conduction from pre to post-synaptic
excitatory NTs
glutamate
histamine
inhibitory NTs
GABA
serotonin
modulatory NTs
acetylcholine
dopamine
norepinephrine
electrical synapse
direct physical contact (gap junction) between the pre and post-synaptic neurons
action at synapse
-depolarization from action potential
-voltage-gated Ca++ channels open
-Ca++ enters the pre-synaptic neuron
-synaptic vesicles fuse
-NT is released
cation
positively charged ion
-usually Na+, sometimes K+ or Ca++
anion
negatively charged ion
-mainly Cl-
ionotropic receptors
activated receptors that are ion channels
metabotropic receptors
G-protein and/or second messenger involved
second messenger
inside the postsynaptic neuronal cell causing a prolonged effect or excitation or inhibition
excitation
increase Na+ conduction through channels
decrease K+ conduction through channels
inhibition
increase Cl- ions into the neuron
increase K+ ions out of the neuron
chemicals that function as synaptic transmitters
-small molecule, rapidly acting transmitters: Ach, NE, Epi, Dopa, GABA, ATP, NO, CO
-neuropeptides (slow acting & more potent): luteinizing hormone, growth hormone, oxytocin, substance P, insulin, glucagon, vasopressin
important small molecule transmitters
Ach: secreted by neurons in many areas, mostly excitatory, inhibits vagus nerve
NE: secreted by neurons w/cell bodies in the brain stem and hypothalamus, increases wakefulness
Dopa: secreted by neurons originated in substantial nigra, usually inhibitory
Glycine: secreted mainly in spinal cord, inhibitory
GABA: primary inhibitory NT in CNS
Glutamate: likely always causes excitation
Serotonin: inhibitor of pain pathways in the cord, controls mood
presynaptic inhibition
inhibitory neuron provides synaptic input to the axon of another neuron ( less likely to fire an AP)
synaptic transmission fatigue
a synapse becomes less effective at transmitting signals over time (mainly exhaustive stores of transmitters)
alkalosis & synaptic transmission
-greatly increases neuronal excitability
-can lead to cerebral epileptic seizures
acidosis & synaptic transmission
-greatly depresses neuronal activity
-causes a comatose state
-ex: DKA or uremic acidosis
hypoxia & synaptic transmission
-can cause complete in-excitability of some neurons
-3-7 seconds patient becomes unconscious
drugs & synaptic transmission
increase excitability: caffeine, theophylline, theobromine
increase TP: many anesthetics
synaptic delay
brief time lapse between the arrival of an AP and the initiations of postsynaptic response
