Exam Prep For
Biological Systems
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** Expert-Verified Explanation
** Questions with Verified Answer
** New Edition | 2026-2027 Updated
,myelin sheath part of neuron that insulates, decreasing surface area to be depolarized and
increasing speed of condution
synaptic knobs part of neuron that receives impulse and releases neurotransmitters
Nodes of Ranvier part of neuron between myelin sheaths that concentrate the ion channels
resting membrane potential polarized to -70mV, where the interior of cell is negatively charged
maintained by two things:
1. Na+/K+ pumps- pump 3 Na+ out, 2 K+ in
2. K+ leak channels- allows K+ to leak out
action potential a neural impulse, a brief electrical charge that travels down an axon
depolarization (action potential) voltage-gated Na+ channels- when membrane potential changes, they open to
allow Na+ to flow into cell
they only open at threshold potential of -50 mV
bringing the cell to about +35 mV
repolarization (action potential) voltage-gated Na+ channels inactivate after opening
voltage-gated K+ channels open slowly in response to depolarization, allowing
K+ to flow out of cell
this brings cell to -90 mV, which slowly returns to -70mV
,saltatory conduction Schwann cells and oligodendrocytes wrap axons with myelin, leaving spaces
for nodes of Ranvier
forces action potential to jump from node to node, speeding up conduction
refractory period absolute refractory period- Na+ channels are inactivated when cells are too
positive, K+ channels open, near Na+ equilibrium potential
relative refractory period- Na+ channels switch from inactivated to closed
(deinactivated) when cells are too negative, K+ channels close as well, near K+
equilibrium potential
electrical synapse gap junction between two cells, bidirectional flow of impulse, rare but
important in cardiac muscle cells
chemical synapse steps:
1. depolarization opens voltage-gated Ca2+ channels
2. Ca2+ influx causes exocytosis of neurotransmitters in secretory vesicles
3. neurotransmitters open ligand-gated Na+ channels on motor endplate
4. Na+ influx triggers action potential
neuromuscular junction- acetylcholine is neurotransmitter
other NTs are GABA, serotonin, dopamine, norepinephrine
1. receptor determines affect, not NT
2. neurons make only one type of NT, can respond to many
signal summation action potential is an "all or nothing" nothing, with the only regulated step
being whether the action potential will fire
excitatory postsynaptic potential- depolarize the next neuron, increases
chance of action potential firing
inhibitory postsynaptic potential- polarize the next neuron, decreases chance
of action potential firing
spatial summation- effect from multiple presynaptic cells is enough EPSP to fire
off postsynaptic cell
temporal summation- signal presynaptic cell, if EPSP are fast enough to fire off
postsynaptic cell
tetanus- too many signals building up
astrocytes guide neuron development, regulate neurotransmitters
microglia immune system of CNS
, ependymal cells produce and circulate cerebrospinal fluid
afferent/efferent/interneurons afferent neurons- sensory neurons, to CNS
efferent neurons- motor/effector neurons, from CNS
interneurons- connects afferent and efferent neurons
reflexes monosympatic reflex arc- sensory neuron directly connects to motor neuron in
the spinal cord
reciprocal inhibition- to contract and reflex muscle pairs
supraspinal circuit- involves input from the brain or brainstem to process a
stimuli, unlike most reflex arcs
brain subdivisions hindbrain- medulla, pons, cerebellum
midbrain- RAS
forebrain- diencephalon, telencephalon (cerebral cortex)
medulla oblongata controls heartbeat and breathing
pons coordinating movement and balance
cerebellum coordinating and smoothing out movement
reticular activating system arousal and wakefulness
thalamus relay point for all sensory information
Biological Systems
** 100% Guaranteed Pass
** Expert-Verified Explanation
** Questions with Verified Answer
** New Edition | 2026-2027 Updated
,myelin sheath part of neuron that insulates, decreasing surface area to be depolarized and
increasing speed of condution
synaptic knobs part of neuron that receives impulse and releases neurotransmitters
Nodes of Ranvier part of neuron between myelin sheaths that concentrate the ion channels
resting membrane potential polarized to -70mV, where the interior of cell is negatively charged
maintained by two things:
1. Na+/K+ pumps- pump 3 Na+ out, 2 K+ in
2. K+ leak channels- allows K+ to leak out
action potential a neural impulse, a brief electrical charge that travels down an axon
depolarization (action potential) voltage-gated Na+ channels- when membrane potential changes, they open to
allow Na+ to flow into cell
they only open at threshold potential of -50 mV
bringing the cell to about +35 mV
repolarization (action potential) voltage-gated Na+ channels inactivate after opening
voltage-gated K+ channels open slowly in response to depolarization, allowing
K+ to flow out of cell
this brings cell to -90 mV, which slowly returns to -70mV
,saltatory conduction Schwann cells and oligodendrocytes wrap axons with myelin, leaving spaces
for nodes of Ranvier
forces action potential to jump from node to node, speeding up conduction
refractory period absolute refractory period- Na+ channels are inactivated when cells are too
positive, K+ channels open, near Na+ equilibrium potential
relative refractory period- Na+ channels switch from inactivated to closed
(deinactivated) when cells are too negative, K+ channels close as well, near K+
equilibrium potential
electrical synapse gap junction between two cells, bidirectional flow of impulse, rare but
important in cardiac muscle cells
chemical synapse steps:
1. depolarization opens voltage-gated Ca2+ channels
2. Ca2+ influx causes exocytosis of neurotransmitters in secretory vesicles
3. neurotransmitters open ligand-gated Na+ channels on motor endplate
4. Na+ influx triggers action potential
neuromuscular junction- acetylcholine is neurotransmitter
other NTs are GABA, serotonin, dopamine, norepinephrine
1. receptor determines affect, not NT
2. neurons make only one type of NT, can respond to many
signal summation action potential is an "all or nothing" nothing, with the only regulated step
being whether the action potential will fire
excitatory postsynaptic potential- depolarize the next neuron, increases
chance of action potential firing
inhibitory postsynaptic potential- polarize the next neuron, decreases chance
of action potential firing
spatial summation- effect from multiple presynaptic cells is enough EPSP to fire
off postsynaptic cell
temporal summation- signal presynaptic cell, if EPSP are fast enough to fire off
postsynaptic cell
tetanus- too many signals building up
astrocytes guide neuron development, regulate neurotransmitters
microglia immune system of CNS
, ependymal cells produce and circulate cerebrospinal fluid
afferent/efferent/interneurons afferent neurons- sensory neurons, to CNS
efferent neurons- motor/effector neurons, from CNS
interneurons- connects afferent and efferent neurons
reflexes monosympatic reflex arc- sensory neuron directly connects to motor neuron in
the spinal cord
reciprocal inhibition- to contract and reflex muscle pairs
supraspinal circuit- involves input from the brain or brainstem to process a
stimuli, unlike most reflex arcs
brain subdivisions hindbrain- medulla, pons, cerebellum
midbrain- RAS
forebrain- diencephalon, telencephalon (cerebral cortex)
medulla oblongata controls heartbeat and breathing
pons coordinating movement and balance
cerebellum coordinating and smoothing out movement
reticular activating system arousal and wakefulness
thalamus relay point for all sensory information
