PNB 2XB3 Midterm 1 Review Flashcards
What is the width of the synaptic cleft?
20-40nm
What is the diameter of the cell body?
10μm
What is the CNS?
The CNS is the central nervous system. All parts of the nervous system within bone: spinal cord, brainstem, thalamus, cortex, etc.
What is the PNS?
The PNS is the peripheral nervous system. All parts not within bone: peripheral nerves.
What is CSF?
CFS is the cerebrospinal fluid. The aqueous saline solution that surround the brain and neurons.
What is AHP?
AHP is after hyperpolarization. AHP is the undershoot that occurs after the rising phase and falling phase in an action potential.
What is an EPSP?
An EPSP is an excitatory postsynaptic potential. An EPSP is the moving of the post-synaptic cell toward threshold.
What is an IPSP?
An IPSP is an inhibitory postsynaptic potential. An IPSP moves the post-synaptic cell away from threshold.
What is an efferent neuron?
An efferent nerve carries impulses away from the cortex.
What is an afferent neuron?
An afferent nerve carries impulses toward the cortex.
How can the driving force equation be used to determine the direction of an ion’s flow across the membrane?
Vm-Ex tells you how far away the neuron is from the equilibrium potential for that ion, this determines how muuch flows
What is the definition of negative current?
Negative current describes the movement of positive ions into the cell, or the movement of negative ions out of the cell.
In both circumstances, the interior of the cell becomes more positive.
What is the definition of positive current?
Positive current is the movement of negative ions into the cell, or the movement of positive ions out of the cell.
In both circumstances, the cell interior becomes more negative.
What causes the absolute refractory period?
The absolute refractory period is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.
In neurons, it is caused by the closure and inactivation of the Na+ channels that originally opened to depolarize the membrane. These channels remain inactivated until the membrane repolarizes, after which they regain their ability to open in response to stimulus.
What causes the AHP?
During AHP the cell becomes more negative due to the opening of voltage gated potassium channels. K+ rushes out of the cell.
Why do we say an action potential is all-or-nothing?
An action potential is all-or-nothing because in order for an action potential to fire, the cell must reach threshold (-55mV)
Why do we say an action potential is regenerative?
The potential change induced by the opening of voltage gated channels decrements as you record further and further away from the Na+ channel. However, this graded depolarization triggers the opening of neighboring Na+ voltage-dependent channels, which results in more Na+ entering the cell, and, in effect, regenerating the action potential.
What is saltatory conduction?
Jumping movement of the action potential from node to node down an axon
Why do we say an action potential is unidirectional?
Under normal conditions, action potentials only move in one direction along the axon. The refractory wake prevents the action potential from moving backwards.
How do local anaesthetic work?
Local anaesthetics are injected topically (where you want them to act)
Example: Lidocaine is an open voltage gated potassium channel blocker. It prevents Na+ from entering the cell, thus action potentials cannot occur. Creates a numbing effect.
How does myelin work to speed up an action potential?
Myelin reduces membrane capacitance because it creates greater separation between positive and negative ions interior and exterior to the cell.
Myelin increases membrane resistance because it covers leaky channels along the membrane.
Does myelin increase or decrease membrane capacitance?
Myelin decreases membrane capacitance
Does myelin increase or decrease membrane resistance?
Myelin increases membrane resistance
Oligodendrocyte vs. Schwann cell
Oligodendrocytes are the glial cells of the CNS and Schwann cells are the glial cells of the PNS.
A single oligodendrocyte can wrap around several axons.
Schwann cells only wrap around a single axon.
What is the difference between multiple sclerosis and Guillain Barre syndrome?
MS and Guillain Barre are both autoimmune disorders of demyelination.
MS causes the demyelination of myelin cells in the CNS and is a progressive neurological disorder.
Guillain Barre causes demyelination of myelin cells in the PNS and is not progressive.
Describe the events that trigger the release of neurotransmitter
When the action potential reaches the axon terminal, it becomes depolarized. This results in the opening of voltage-gated Ca++ channels along the axon terminal membrane. Ca++ moves into the cell along its concentration gradient and entering calcium binds to a calcium sensor on the vesicle called synaptotagmin. SNARE complexes then form to pull membranes together. Ca++-bound synaptotagmin catalyzes membrane fusion. releasing neurotransmitter into the cleft.
What famous experiment did Otto Loewi perform, and what did it show?
Otto Loewi came up with an experiment to prove chemical transmission in a heartbeat.
He showed that there was a gap between neurons.
What experimental evidence supports the conclusion that synaptic transmission is quantal in nature?
Depolarization occurs in integer multiples of a certain quantity. This demonstrates that chemicals are not randomly spilling, they are released in specific integer quantities.
What causes the quantal nature of synaptic transmission?
Not every action potential will release the same number of synaptic vesicles
What is the value of the resting potential of a typical neuron?
-65mV
What is the value of the action potential threshold?
-55mV
Which of these ions has a higher inside concentration than outside concentration: Na+, K+, Ca++, Cl-
Na+: Higher concentration outside
K+: Higher concentration inside
Ca++: Higher concentration outside
Cl-: Higher concentration outside
Describe the sensory deficits that occur in Brown Sequard syndrome. Why do those specific deficits occur?
Brown-Sequard causes damage to half of the spinal cord, either the left-half or the right-half. All the axons coming from below the body are cut, theferfore you will have ipsilateral loss of touch and contralateral loss of pain and temperature.