Neuron Structure & Function + The Nervous System Flashcards
What is the function of sensory neurons?
receive and transmit information about an anima;’s environment or its internal physiological state
What is the function of interneurons?
receive and transmit information received by sensory neurons and transmits it to motor neurons
What is the function of motor neurons?
signal a muscle or gland to cause a response in the body
Where are stimuli received by the neuron?
dendrites
Where are synaptic stimuli summed?
axon hillock
____ potentials travel through the cell body
____ potentials travel through the axon
graded; action
What is membrane potential?
a difference in electrical charge across the cell membrane
Resting membrane potential is ____ mV
-70
Na+ moves ____ the cell through the ____ Na+ channel
into; voltage-gated
K+ moves ____ the cell through the ____ K+ channel
out; voltage-gated
The sodium-potasium pump pumps ____ Na+ ions ____ the cell and ____ K+ ions ____ the cell.
3 Na+ ions; out
2 K+ ions; into
True or False:
The sodium-potassium pump pumps a net positive charge of ions into the cell.
False
At resting potential:
Membrane potential is more negative/positive inside the cell than outside.
negative
At resting potential:
There is a greater/lower concentration of Na+ ions outside the cell than inside.
greater
At resting potential:
There is a greater/lower concentration of K+ ions inside the cell than outside.
greater
Threshold potential is ____ mV.
-55
What happens at threshold potential?
Na+ voltage-gated ion channels open and the action potential fires.
What is depolarization?
an increase in membrane potential from a negative resting potential
List the steps of an action potential.
- resting
- depolarization
- peak action potential
- repolarization
- hyperpolarization
At peak action potential:
Membrane potential is more negative/positive inside the cell than outside.
positive
At peak action potential:
There is a greater/lower concentration of Na+ ions outside the cell than inside.
lower
At peak action potential:
There is a greater/lower concentration of K+ ions inside the cell than outside.
higher
How are chemical gradients formed?
from concentration differences
How are electrical gradients formed?
from charge separation
What is the flow of chemical gradients?
high concentration –> low concentration
What is the flow of electrical gradients?
positive –> negative
What kind of ion channels are primarily present at the neuron’s dendrites? Why?
ligand-gated ion channels
neurotransmitters bind to these channels in the post-synaptic neuron
What are the two types of graded potentials?
excitatory postsynaptic potential (EPSP)
inhibitory postynaptic potential (IPSP)
What happens when a dendrite receives an EPSP?
cell depolarizes
more likely to initiate an action potential
What happens when a dendrite receives an IPSP?
cell hyperpolarizes
less likely to initiate an action potential
What are the conditions of an action potential occurring?
if the sum of EPSPs and IPSPs reach the threshold potential
How does no summation occur?
multiple EPSPs widely spaced in time do not set off an action potential
How does temporal summation occur?
multiple EPSPs arrive quickly at a single synapse
How does spatial summation occur?
single EPSPs arrive at the same time at different synapses
How does cancellation occur?
an EPSP and IPSP cancel each other out and no action potential occurs
How does action potential propagation occur?
depolarization spreads through the axon and triggers more voltage-gated sodium channels to open and more action potentials to occur
What is the role of myelin?
insulates the axon and increases the rate of action potentials
True or False:
Strong stimuli (more concentration) in the synapse cause neurons to fire more frequent action potentials.
True
True or False:
Synapses are fixed.
False
Synapses are not fixed, which allows for neuroplasticity and learning/memory.
Where are voltage-gated channels found in the neuron?
cellular membrane
Where are ligand-gated channels found in the neuron?
dendrites
What are the steps of synapse communication?
- stimulated by the action potential
- voltage-gated Ca2+ channels open
- vesicles at the axon terminals respond to Ca2+ by fusing with the pre-synaptic membrane
- vesicles perform exocytosis to release neurotransmitters into the synaptic cleft
- neurotransmitters bind to ligand-gated ion channels in the post-synaptic membrane
- neurotransmitters are re-absorbed into the pre-synaptic terminal and stored until the next action potential arrives
What are the two divisions of the nervous system?
central nervous system and peripheral nervous system
What are the components of the central nervous system?
brain and spinal cord
What are the components of the peripheral nervous system?
sensory and motor nerves
What are the two divisions of the peripheral nervous system?
somatic and autonomic
What is the somatic nervous system responsible for?
controlling voluntary activity
What is the autonomic nervous system responsible for?
controlling involuntary activity
What are the two divisions of the autonomic nervous system?
parasympathetic and sympathetic
What does the parasympathetic nervous system do?
rest and digest
What does the sympathetic nervous system do?
fight or flight
What are afferent neurons?
send information toward the CNS
What are efferent neurons?
send information away from the CNS
True or False:
Simple reflex circuits go through the CNS.
False
Simple reflex circuits bypass the brain.
How does the patellar reflex work?
- patellar tendon is struck
- stretch receptor in muscle responds by sending a signal along the sensory
- sensory neuron synapses with motor neuron in the spinal cord
- motor neuron sends signal to muscle, which contracts
- inhibitory interneuron inhibits contraction of the muscle
What is the purpose of the sodium-potassium pump?
to maintain resting membrane potential by pumping a net negative charge
(more cations are pumped out the cell than inside)
What happens if a myelinated and unmyelinated neuron arrive at different dendrites and deliver EPSPs?
No spatial summation would occur because the myelinated neuron would arrive at the dendrite before the unmyelinated neuron
What is the refractory period of the action potential?
The point at which hyperpolarization is occurring; no action potential could occur at this time while the K+ ions are still closing
What would happen if the Na+ and K+ voltage gated channels opened at the same time?
no action potential would occur
the movement of ions would “cancel” each other out
How does morphine affect the synapse over time?
- increases synaptic activity over time
- to maintain homeostasis, the body decreases the number of receptors in the post-synaptic membrane in order to decrease synaptic activity back to normal
What is an agonist?
a molecule (usually a drug) that mimics existing neurotransmitters
