Nervous System Flashcards
synapse
Space between two cells (can be between two nerve cells, a cell and a gland cell, etc.)
neuromuscular junction
example of a synapse
synapse between motor neuron and skeletal muscle cell
process of neuromuscular junction
An action potential in the motor neuron causes voltage-gated Ca2+
channels open and Ca2+ enters the axon terminal.
Ø Calcium causes vesicles to fuse with the presynaptic membrane and
release acetylcholine (Ach) into the synaptic cleft, the space
between the presynaptic and postsynaptic membranes.
Ø The postsynaptic membrane of the muscle cell is the motor end
plate. Ach binding to receptors causes depolarization of the muscle.
neuromuscular junction is an
excitatory
synapse.
when are other synapses inhibitory?
if postsynaptic response is hyperpolarization
Make the cell even more negative (move K+ out of cell)
summation is
both spatial and temporal
spatial: input at different synaptic sites
temporal: input at the same site, over time
what occurs at the axon hillock
Neurons have many synapses that must sum excitatory and inhibitory input
Axon hillock decides whether or not to fire action potential
§ Depends on the potential at the axon hillock as a result of all synapses.
excitatory synapse
Depends on both spatial and temporal
• Must reach a certain threshold for an action potential to be fired to
postsynaptic membrane.
Main neurotransmitters in the CNS
ACh, Glutamate, Gly, adenosine, and GABA, monoamines, peptides
Glutamate
an excitatory amino acid mostly in CNS
receptors are:
• NMDA (inotropic: Na+)
• AMPA (inotropic: Ca2+)- repeated stimulation can cause longterm
potentiation (memory)
Glycine, adenosine, and GABA
inhibitory (amino acids and nucleosides)
Drugs that affect Action potentials
Drugs treat the nervous system by modulating
synaptic interactions.
agonists
antagonists
agonists
mimic or potentiate the effect of a
neurotransmitter.
morphine is an agonist at the endorphin receptor, therefore blocks pain
antagonists
block the actions of a
neurotransmitter.
caffeine is an antagonist and binds at the adenosine receptor on nerve cells
initiates brain activity
caffeine ties up the receptor and hyperpolarizes the membrane
both are purines
sensory cells
s transduce physical and chemical
stimuli into neuronal signals using different
channels and/or receptors:
chemically-gated channels
depend on
molecules that bind or alter channel protein
(chemoreceptors, photoreceptors)
mechanically gated channels
respond to
force applied to membrane (mechanoreceptors,
thermoreceptors, electrosensors)
difference between iontropic and metabotropic sensory receptors
no secondary messengers involved with iontropic sensory receptors
Autonomic Nervous System
— the
output (efferent) of the CNS that controls
involuntary functions.
has two divisions that work in opposition: sympathetic and parasympathetic that are distinguished by anatomy, neurotransmitters, and action potentials
Sympathetic
increase a function
cholinergic (preganglionic) and noradrenergic neurons (postglanglionic) go to the glands
Ganglia that are part of central nervous system that are attached to the
spine–>sympathetic nervous system responses
parasympathetic
decrease a function cholinergic neurons (preganglionic) and cholinergic neurons (postganglionic)
Postganglionic neurons very close to the gland that it innervates
autonomic commands
heart rate, sweating, salivation
neural afferents
sends info to CNS
human eye
sensory stem for light
