exam 1 IMPORTANT Flashcards
How can the PNS be divided physiologically?
afferent nervous system & efferent nervous system
What is the afferent nervous system?
carries impulses/stimuli INTO brain & spinal cord; sensory division
What is the efferent nervous system?
carries impulses/stimuli OUT OF brain & spinal cord to muscles & glands called effectors; motor division
What is the ANS divided into?
sympathetic & parasympathetic divisions
What are neurons?
cells that can generate, receive, send, & transmit some type of impulse
What are the different shapes of neurons?
multipolar, bipolar, & unipolar (pseudounipolar)
What does multipolar mean?
many dendrites & 1 axon; found everywhere including the brain
What does bipolar mean?
1 dendrite & 1 axon; in sense organs like the retina of the eye
What does unipolar (pseudounipolar) mean?
1 extension from the cell body that branches into dendrite & axon; in cranial nerves such as nerves for sense of smell
How are neurons classified by function?
afferent, efferent, & association
What do afferent, efferent, & association mean?
sensory, motor, & the link to sensory and motor
How are neurons classified by myelination?
white matter & gray matter
What is white matter?
myelinated neurons; myelin coats the axons
What is gray matter?
non-myelinated neurons
What are dendrites?
usually short, thick, branched cytoplasmic extensions from the cell body; they receive the impulse
What is the axon?
usually 1 long extension that arises from a little bump called an axon hillock
The distal end of the axon branches into what?
axon terminals that end in button-like synaptic end bulbs
What do the synaptic end bulbs contain?
many synaptic vesicles that store & release neurotransmitter onto the next cell
What is the goal of impulse physiology?
to release the neurotransmitter molecules when the neuron is stimulated
What is the first step of impulse physiology?
the dendrite ends receive the impulse
What does the impulse create in the cytoplasm once it is received?
the impulse causes waves/ripples to go through the ICF
What happens if the waves are strong enough to reach the axon hillock?
voltage gated membrane channels will open
What is a threshold stimulus?
a stimulus that is strong enough to elicit opening of these channels
What is a resting neuron?
a neuron in the body that is not active
What 2 areas have a voltage difference between them (in a resting neuron)?
the ICF & ECF
What is the resting membrane potential?
the voltage between the ICF & ECF when at rest; -70mV
What does the -70mV value mean?
there is a difference in voltage of 70mV AND the ICF has a negative charge
What can be found in the ECF & ICF of a resting neuron?
there are many sodium ions in the ECF & many potassium ions in the ICF
What happens when the threshold stimulus is applied?
voltage gated channels open; there are 2 types
What are the 2 types of voltage gated channels?
voltage gated sodium channel & voltage gated potassium channel
What is the voltage gated sodium channel?
it looks like a door that pops open; it opens rapidly allowing Na+ to enter the cytoplasm
Why does the Na+ enter the cell?
the concentration gradient & the pull from the negative ICF
What happens as the Na+ rush in to the cell?
depolarization; the mV increases; it goes -70, -50, 0, 30
What is the voltage gated potassium channel?
looks like twisties; opens slowly, becoming open at about 30mV; allows potassium to exit the cell
Why does K+ exit the ICF?
the concentration gradient & the pull from the now slightly negative charge of the ECF
What happens as the K+ goes out?
the mV decreases; it goes from 30, 0, -50, -70
What happens as the wave of impulse/depolarization reaches the synaptic end bulbs?
Ca++ channels open & Ca++ enters the synaptic end bulbs from the ECF
What triggers migration & exocytosis of synaptic vesicles?
calcium ions (Ca++)
What is the synapse?
a small space that neurotransmitter molecules diffuse across
Where do neurotransmitter molecules go from the synapse?
the “next cell” which can be called the post-synaptic cell
What does the Na+/K+ Pump do?
moves 3 Na+ out of cell for every 2 K+ that enter the cell
Does the Na+/K+ Pump require ATP (energy)?
yes
What is the refractory period?
absolute: the time in which the neuron cannot send an impulse; relative: can fire but requires more stimulation
Why does the refractory period occur?
because no impulse can travel though the neuron until the action of the Na+/K+ Pump is complete
Where does continuous conduction of the impulse occur?
in neurons that lack myelin; this process causes all voltage gated channels to open
Where does salvatory conduction of the impulse occur?
in neurons that are covered in myelin; myelin wraps the axon in discontinuous pieces with unmyelinated nodes in between
What are the unmyelinated gaps called?
nodes of ranvier; during depolarization, ONLY the channels in these nodes operate
Which kind of conduction of the impulse is faster?
salvatory conduction
Under what circumstances would Chlorine ions (Cl-) enter the neuron?
to inhibit release of neurotransmitter & response by the post-synaptic cell
What happens to the membrane voltage when Cl- enters the cell?
it decreases because of the negative ion; this makes the axon even more polarized
