Nervous System lecture 6.2 Flashcards
What are the two types of summation?
spatial and temporal
define continuous conduction
a step-by-step depolarization and repolarization of each adjacent segment of the plasma membrane.
Only travels a short distance and occurs in unmyelinated axons and muscle fibers
Does it take a single or multiple ESPS to create a nerve impulse?
multiple
what are the two types of propagation
continuous and saltatory
define the refractory period, absolute refractory period, and relative refractory period.
refractory period: a period after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus
absolute refractory period: even a very strong stimulus cannot initiate a second action potential
relative refractory period: a period during which a second action potential can be initiated but only by a larger than normal stimulus
define saltatory conduction
action potential propagation that occurs along myelinated axons jumping from node of Ranvier to node due to the high numbers of voltage-gated channels at that location.
A neurotransmitter that causes hyperpolarization is considered what
inhibitory, specifically an inhibitory postsynaptic potential (IPSP)
describe angiotension II
may regulate blood pressure and stimulates thirst
what are the two main advantages of electrical synapses?
faster communication and synchronization ( can synchronize the activity of a group of neurons of muscle fibers)
Na+/K+–ATPase is considered to be an electrogenic pump because
a) it contributes to the negativity of the resting membrane potential.
b) the sodium ions are negatively charged.
c) it exhibits low permeability.
d) it hydrolyzes ADP into ATP.
e) destroys the resting membrane potential.
A
how are neurotransmitters removed
diffusion, enzymatic degradation, and reuptake by cells
function of the junction of axon hillock and initial segment of the axon
trigger zone for many neurons integrates EPSP’s and IPSPs
what is the function of a neural cell body
receives stimuli and produces EPSPs and IPSPs through activation of ligand-gated ion channels
describe endorphins
inhibit pain, may have role in memory and learning, sexual activity, control of body temperature, and mental illness
How can sensory systems detect stimuli of differing intensities?
the frequency of action potentials, how often they are generated at the trigger zone.
the number of sensory neurons recruited by the stimulus
define regenerate
the capability to replicate or repair
function of axon terminals and synaptic end bulbs
inflow of Ca2+ caused by depolarization phase of impulse causes exocytosis of neurotransmitter from synaptic vesicles
What are the four types of neural circuits
divergence, convergence, reverberating circuit, and parallel after-discharge circuit
define metabotropic receptors
a type of neurotransmitter receptor that contains a neurotransmitter binding site but does not have an ion channel. Needs g proteins or secondary messangers to open the ion channel.
define a chemical synapse
in response to an impulse, the presynaptic neuron releases a neurotransmitter that diffuses through the fluid in the synaptic cleft and binds to receptors in the plasma membrane of the postsynaptic neuron. This process turns an electrical signal into a chemical signal and the postsynaptic neuron turns it back into an electrical signal in the form of a postsynaptic potential which is a graded potential
define temporal summation
Temporal summation occurs when one presynaptic neuron releases neurotransmitters many times over a period of time. The total amount of neurotransmitters released may exceed the threshold value of the postsynaptic neuron. The higher the frequency of the action potential the more quickly the threshold may be exceeded.
Why is there little to no repair in the CNS?
inhibitory influences from oligodendrocytes, absence of growth-stimulating cues present in fetal development, and the rapid formation of scar tissue
what is generator potential
a graded potential developed in a receptor zone (dendrites) of a neuron as a response to a stimulus
Graded potentials occur in response to the opening of what type of channel?
mechanically-gated or ligand-gated
define a postsynaptic cell/neuron
the cell that receives the signal
the neuron that carries the impulse away from a synapse or an effector cell that responds to the impulse at the synapse
how are axons classified?
amount of myelination
diameters
propagation speeds
What is summation?
the process by which graded potentials add together. if two depolarizing graded potentials summate, the net result is a larger depolarizing graded potential
Define spatial summation
Spatial summation occurs when multiple presynaptic neurons together release enough neurotransmitters to exceed the threshold of the postsynaptic neuron. For example, neuron A and neuron B may individually release insufficient neurotransmitters but when these quantities are combined, the threshold may be exceeded and an action potential is generated.
what are the two types of neurotransmitter receptors
iono-tropic receptors
metabo-tropic receptor
describe cholecystokinin (CCK)
may regulate eating through a “stop eating” signal. Regulates pancreatic enzymes secretion and contraction of smooth muscle in GI tract
Define B fibers
myelinated, intermediate diameter, longer absolute refractory period. Conduct sensory nerve impulses from the viscera to the brain and spinal cord. Also, constitute all of the axons of the autonomic motor neurons that extend from the brain to the spinal cord to the ANS relay stations called the autonomic ganglia
function of axon
propogates nerves impulses to axon terminals
describe enkephalins
inhibits pain impulses, may have a role in memory and learning, control in body temperature, sexual activity, and mental illness
name the 6 inihibatory neurotransmitterss
acetylcholine, GABA, epinephrine, NE, dopamine, and serotonin
What are the steps in PNS repair
chromatolysis, wallerian degeneration, and formation of a regeneration tube
What are the functions of dendrites?
receive stimuli through the activation of ligand-gated or mechanically-gated ion channels and produce generator or receptor protentials
what is an action potential?
a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state.
Where do graded potentials mainly occur?
the dendrites and cell body of a neuron
What is the ratio for the Na/K ATPase pump?
For every 2 K brought into the cell, three Na are expelled
What are the two different types of synapses?
electrical and chemical
define ionotropic receptors and the type of channel it is
a neurotransmitter receptor that contains a neurotransmitter binding site and ion channel all contained in the same membrane protein. It is a type of ligand-gated channel
define plasticity
the capability to change based on experience
what are the two types of graded potentials neurotransmitters can create?
inhibitory or excitatory
Where do action potentials in the neuron start and end
the trigger zone of the axon to the axon terminals
What is a graded potential?
A small deviation from the membrane potential that makes the membrane either more polarized (hyperpolarized) or less polarized (depolarized).
hypothalmic releasing and inhibiting hormones
regulate release of hormones by the anterior pituitary
What is the typical resting membrane potential?
-70mV. The inside of the cell is negative
Name the 10 excitatory small molecule neurotransmitters
acetylcholine, glutamate, aspartate, epinephrine, NE, dopamine, serotonin, ATP, nitric oxide, and CO
A neurotransmitter that causes depolarization is considered what?
excitatory, specifically called excitatory postsynaptic potential (EPSP)
What are the three steps of the generation of an action potential?
- voltage-gated Na channels open which allows Na to rush into the cell and cause depolarization
- voltage-gated K channels open allowing K to flow out which causes repolarization
- K channels remain open, which causes hyperpolarization
Define A fibers
myelinated, largest diameter, long absolute refractory period
associated with touch, pressure, the position of joints, and some thermal, pain sensations, and the axons of motor neurons that conduct impulses to skeletal muscles
define electrical synapses
action potentials conduct directly between the plasma membranes of adjacent neurons through gap junctions. This is common in visceral smooth muscle, cardiac muscle, developing embryo, and brain
What causes resting membrane potential?
A small buildup of negative ions in the cytosol along the inside of the membrane and an equal build up of positive ions in the extracellular fluid along the outer surface of the membrane.
describe neuropeptide Y
stimulates food intake, may play a role in stress response
What are to defining features of chemical synapses?
relay signals more slowly than electrical synapses and are only able to transfer information one way.
What are the three major factors that cause the resting membrane potential?
- unequal distribution of ions in the ECF and cytosol
- inability of most anions to leave the cell
- electrogenic nature of Na/K ATPase.
What are the three places synapses can occur?
axodendritic- axon to dendrite
axosomatic- axon to cell body
axoaxonic- axon to axon
what is receptor potential?
a graded potential developed by a receptor cell as a response to a stimuli
describe hyperpolarization, depolarization, and repolarization
hyperpolarization: the membrane potential becomes more negative
depolarization: the membrane potential becomes more positive
repolarization: the membrane potential returns back to it’s resting state of -70mV
describe dynophins
may be related to controlling pain and registering emotions
What are a suprathreshold stimulus and a subthreshold stimulus?
suprathreshold: a stimulus that is strong enough to depolarize the membrane above the threshold
subthreshold: a stimulus that causes a weak polarization that does not bring the membrane potential over the threshold
What is a synapse?
a region where communication occurs between two neurons or a neuron and a muscle/gland
what is the general threshold for an action potential to take place?
-55 mV
what are the two main phases of an action potential?
depolarizing and repolarizing
describe substance P
enhances perception of pain
Why are they called graded potentials?
they vary in amplitude (size) depending on the strength of the stimulus.
define C fibers
unmyelinated, smallest diameter, longest absolute refractory period. Autonomic muscle fibers that extend from the autonomic ganglia to stimulate the heart, smooth muscle, and glands.
pain, touch, pressure, heat, and cold from the skin and pain impulses from the viscera
what determines the size of a graded potential?
how many ligand gated or mechanically gated channels have opened/closed and for how long each remains open
What is the all or nothing principle?
action potentials either happen or they dont
define presynaptic neuron
the nerve cell that carries a nerve impulse toward a synapse
Three factors that affect the speed of propagation of an action potential
- the amount of myelination
- axon diameter, larger = faster
- temperature, heat=faster
what are the two classes of neurotransmitters
small molecule neurotransmitters
neuropeptides
