Discussion 12 Flashcards
What is the initial segment of a neuron?
The initial segment overlaps with the axon hillock and is rich in voltage-sensitive channels.
What occurs at the initial segment of a neuron?
EPSPs and IPSPs are integrated, and if the threshold is reached, an action potential will be generated.
What happens if the threshold is reached at the initial segment?
An action potential will be generated and propagate down the axon.
What is back propagation in neurons?
It is the reverse movement of an action potential into the dendritic field.
Where can voltage-gated channels be found in some neurons?
Some neurons may have voltage-gated channels on dendrites.
What role do dendritic channels play in learning and memory?
They may underlie some of the plastic changes in learning and memory.
What is the action potential?
An action potential is generated if a depolarizing graded potential is strong enough.
How long does an action potential last?
An action potential lasts approximately 1 millisecond.
What happens during the initial phase of an action potential?
Na+ channels open first, allowing sodium to rush in, making the inside of the cell more positive (depolarized).
What occurs after Na+ channels open during an action potential?
K+ channels must open next, allowing potassium to exit, making the cell more negative (repolarized).
What is the threshold potential?
It is the voltage on a neural membrane at which an action potential is triggered, approximately -50 mV.
What are voltage-sensitive ion channels?
They are gated protein channels that open or close at specific membrane voltages.
How do sodium and potassium channels behave at resting potential?
Both are closed at the membrane’s resting potential.
Which channels are more sensitive, sodium or potassium?
Sodium channels are more sensitive than potassium channels and open sooner.
What is the sequence of actions during an action potential?
Both sodium and potassium channels open at about -50 mV, allowing ions to flow across the membrane.
What happens to sodium channels at +30 mV?
One of the gates of sodium channels closes, stopping Na+ influx.
How do potassium channels behave during an action potential?
K+ channels open slower than Na+ channels and remain open longer, leading to hyperpolarization.
What is the absolute refractory period?
It is the state of an axon during repolarization when a new action potential cannot be elicited.
What is the relative refractory period?
It is the state of an axon in the late phase of an action potential requiring increased current to produce another action potential.
What do refractory periods do?
They prevent an action potential from returning to the origin and ensure propagation in the appropriate direction.
What is a nerve impulse?
It is the propagation of an action potential along an axon without degradation.
What is myelination?
It is produced by oligodendroglia in the CNS and Schwann cells in the PNS, acting as insulation to speed up neural impulses.
What are nodes of Ranvier?
They are tiny gaps in the myelin covering axons that speed up action potentials by allowing them to jump from node to node.
What is saltatory conduction?
It is the propagation of an action potential at successive nodes of Ranvier, resulting in a faster signal.
How does sensory information travel?
Sensory receptors connected to ion channels transmit information to the brain for processing.
What is the end plate in muscle contraction?
It is the receptor/ion complex activated by acetylcholine released from a motor neuron.
What is myasthenia gravis?
It is an autoimmune disease where the body attacks the end plate receptor on muscles, reducing sensitivity to Na+ and K+.
What is the role of acetylcholine?
It inhibits heart rate and activates skeletal muscles.
What are neurotransmitters?
They are chemicals released by a neuron onto a target with either excitatory or inhibitory effects.
Autoimmune disease
the loss of immune systems ability to discriminate between foreign substances and the body
End plate
the receptor/ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron
Stretch sensitive receptors
ion channels on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse
