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72 Cards in this Set
- Front
- Back
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What are the three types (levels) of Action Potentials? |
Subthreshold Potential-Not enough to trigger AP Threshold Potential-Just enough stimulus to trigger AP Suprathreshold Potential-More than enough stimulus to AP |
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Describe the magnitude of electrochemical gradients of action potentials? |
They are exactly the same for all action potentials. |
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How does the nervous system code for intensity of stimuli with APs? |
A combination of frequency of APs and how
many sensory receptors are stimulated to code for intensity. |
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What is the period of time called during which the membrane is unresponsive to threshold level stimulus? |
Refractory Period |
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What causes the refractory period? |
During the first part of the refractory period the Na+channels are open During the second part of the refractory period the inactivation gates are closed and need to be reset (Membrane Potential of -70) |
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What is the relative refractory period? |
The period of time when the membrane can be stimulated to fire an AP but it requires a stronger stimulus (hyperpolarization). |
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Why cant AP be summated? |
Once the channels are open they can not be stimulated again until after they repolarize. |
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Does an AP travel faster through a myelinated or unmyelinated neuron? Why? |
Myelinated. In unmyelinated the Na+ travels down each patch of the membrane stimulated the next section. For Myelinated the Na+ only has to travel from one node (gap) in the Myelin to the next (faster) |
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What two factors affect the velocity of the conduction of an AP? |
R(resistance)=1/r4 radius to the 4th power |
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What is the effect of Decreased Na+ in the
ECF on an action potential? |
It will decrease the amplitude of the AP when the Na+ levels are decreased as less Na+ will flow into the cell. |
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What is the effect of Decreased K+ in the ECF on an action potential?
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Hypokalemia will create a greater gradient for K+ leaving the cell hyperpolarizing the Em (less excitable) Causes muscle weakness, paralysis, fatigue |
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What effect does Hyperkalemia have of threshold potential?
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Makes the cell more excitable by decreasing the resting Em. This also slows the repolarization process as less K+ will leave the cell during repolarization (smaller gradient) |
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What effect does hypocalcemia have on threshold potentials? |
Low Ca++ decreases the initial depolarization required to get the Na+ gates open causing an AP making the neuron more excitable without changing the resting Em.
Hypocalcemic Tetany and Carpopedal spasm |
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What effect does Hypercalcemia have of threshold potential? |
Raises the threshold potential making it less excitable. |
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What are the two types of synapses in the body? |
Electrical Synapses-Uses gap junctions to diffuse Na+ from one cell to the next continuing the AP Chemical Synapses-When an AP stimulates the presynaptic neuron it releases a chemical that diffuses across the Synaptic cleft to stimulate a receptor. |
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What are the three classifications of chemical synapses based on where the presynaptic neuron connects to the postsynaptic neuron? |
Axodendritic synapse- Pre-Axon to Post-Dendrite Axoaxonic synapse- Pre-Axon to Post-Axon Axosomatic synapse- Pre-Axon to Post-Cell body |
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For a chemical synapse what are three properties of the pre-synaptic axon terminal? |
Contains synaptic vesicles that contain neurotransmitters (each containing about the same number of neurotransmitters) Contains/synthesizes primarily just one neurotransmitter per pre-synaptic neuron There are also voltage regulated Ca++ channels |
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How does an AP trigger the release of neurotransmitters to the synaptic cleft in a chemical synapse? |
AP reaches membrane of axon terminal stimulating opening of voltage gated Ca++ channels. Ca++ triggers exocytosis of vesicles which releases neurotransmitter contained within # of vesicles released depends on amount of Ca++ |
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What are the three ways an action in the synaptic cleft is terminated? |
Removal of the neurotransmitter by: Enzyme destruction most common & fastest Reuptake into the cell and vesicles Diffusion away from site |
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What is the neurotransmitter for a cholinergic synapse? What is the enzyme that breaks down the neurotransmitter? |
Acetylcholine Acetylcholinesterase breaks it down into acetate and choline. |
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Is two way transmission of an AP possible for electrical and or chemical synapses? Why? |
Yes for electrical and no for chemical as there are no receptors for the neurotransmitters on the pre-synaptic membrane. |
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Which type of synapse has the fastest transmission or shortest synaptic delay? |
The electrical synapse has a faster transmission or shortest synaptic delay as it has fewer steps to complete the transmission. |
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What is an Excitatory Postsynaptic Potential (EPSP)? |
a local or graded potential that is transmitted from the point of origin to the axon hillock Short lived Conducted decrementally Opens a cation channel (Na+, K+) depolarizing |
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What is an Inhibitory Postsynaptic Potential (IPSP)? |
a local or graded potential that is transmitted from the point of origin to the axon hillock
Conducted decrementally Opens K+ or Cl- channels to cause hyperpolarization of the membrane |
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What determines whether a receptor is an EPSP or an IPSP? |
The type of channel that is opened by the neurotransmitter. Cation EPSP or (K+,Cl-) IPSP One neurotransmitter can stimulate an EPSP and an IPSP. |
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What is convergence at a postsynaptic neuron? |
One cell can be stimulated by 1000s of synaptic inputs Some EPSP and some IPSP Post synaptic neuron must integrate signals. |
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What is divergence of inputs? |
When one cell influences many other cells. |
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Can one EPSP trigger an AP? |
No, it takes multiple EPSPs with summation to trigger an AP. |
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What is facilitation of a neuron? |
When a membrane is partially depolarized, but not yet enough to depolarize and stimulate an AP. |
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What are two types of summation? |
Spatial summation-2 or more EPSPs in near simultaneous stimulation at different sites that add together. Temporal summation-2 or more EPSPs close in time from same synapse added together If spatial summation of EPSP and IPSP occur they compete with each other. |
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How can a signal be modulated at a synapse? (types of modulation) |
Attenuated (reduced) Enhanced (Increased) |
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What are ways a signal can be modulated? |
Via Neuromodulators that might influence reuptake, metabolism, synthesis, and release of NT Via Natural pre-wired mechanisms such as GABA Via drug, toxin, or poison effects |
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What are the two classes of senses? |
General Senses- touch, pressure, vibration, Proprioception, temperature, & pain Special Senses- Vision, Hearing, Balance, Smell, and Taste |
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What forms can information about the world be transmitted in? |
Electromagnetic Mechanical Thermal Chemical |
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What is the function of sensory receptors? |
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What is the Doctrine of Nerve Energies? |
For every type of sensation there is a special type of sensory receptor whose activation always gives rise to that sensation. |
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What is an Adequate Stimulus? |
Each type or sensory receptor has its own unique adequate stimulus. (Rods and Cones is light energy) |
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What is Modality? |
The quality or type of sensation produced. (some are conscious while some are not) |
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How are general and special senses neuron endings different? |
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What are the two types of sensory Receptors classification? |
By type of receptors: Mechanoreceptors, photoreceptors, Thermoreceptors, or Nociceptors Or by Source of Stimulus: Exteroceptors, Enteroceptors, and Proprioceptors |
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What is a receptor potential? |
a type of graded/local potential where: the amplitude is proportional to the intensity of the stimulus they travel decrementally toward the axon |
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What is adaptation? |
a reduction in response (the # of action potentials) to a constant stimulus; helps prevent sensory overload. |
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What are the two types of adaption? |
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What region of the brain does an afferent sign need to reach? |
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What is the path (types or orders of neurons) of a sensory stimulus as it travels to the brain? |
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What is the pathway of afferent signals in the brain? |
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What is Decussation? |
the crossing over of a sensory signal from one side of the body to the other side of the brain. |
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What is the Sensory Homunculus? |
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What is a labeled line? |
a specific neuropathway through which somatosensory information travels to get to the region of the cortex where it is mapped out. |
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How is the area of the cortex devoted to a body part determined? |
The area is determined by the number of sensory receptors in the area not the size of the body part. |
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What is a receptive field? |
a specific physical area that when stimulation will activate a specific sensory neuron. The larger the field is the less precise the brain is able to determine where the stimulus is. |
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What is convergence of sensory neurons? |
When more than one 1st order neuron combines together onto a 2nd order neuron. This also makes the stimulus more difficult to pinpoint |
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Which nerves do general sense afferents from
the face, mouth, and head use to reach the
somatosensory cortex? |
The cranial nerves (12 pairs). |
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Which nerves do somatosensory signals from the body use to reach the somatosensory cortex? |
The mixed spinal nerves (31 pairs). Each pair supplies a specific region, but there is overlap between nerve pairs. |
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What is a dermatome? |
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How are afferent neurons classified? (Type, relative diameter, Relative conductance velocity, and myelination) |
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What are the functions of the Afferent 1st Order Neurons classified by group? |
Group 1- doesn't reach consciousness Group 2- Feedback about fine touch/fine pressure, proprioceptive info, Myelinated, Medium axon diameter Group 3- Feedback about crude touch/pressure, not as precise; small diameter Group4-Slowest velocity= Temp, Pain |
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How do spinal nerves attach to the spinal cord? |
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What does the ventral and dorsal root contain? |
Dorsal Root- axons of only sensory & 1st order afferent neurons Each dorsal root contains a dorsal root ganglion (cell bodies) Ventral Root- axons of efferent motor neurons |
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Where do spinal nerves enter the vertebral canal? |
Through intervertebral foramina. |
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What is the structure and function of the spinal cord? |
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What is contained in the gray matter of the spine? |
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What is contained in the white matter of the spine? |
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What is in the ascending and descending tracts of the spinal cord? |
Ascending-composed of axons of 1st and 2nd order afferent neurons carrying sensory information up the spinal cord Descending- Composed of axons of upper motor neurons that carry signals from various parts of the brain down the spinal cord |
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What are the two types of Decussation? |
Ipsilateral- on the same side of the reference point Contralateral- on the opposite side of the reference point |
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