Action Potential

What is an action potential?

A fundamental electrical signal essential for neuronal communication.

What are the two types of neurotransmitters that affect postsynaptic terminals?

Excitatory and inhibitory neurotransmitters.

What does depolarization of the postsynaptic membrane indicate?

An excitatory input that may lead to an action potential.

What is the process by which a postsynaptic neuron integrates multiple synaptic inputs?

Summation of the excitatory and inhibitory signals.

What is the threshold potential necessary to trigger an action potential?

Depolarization to around -55 to -40 millivolts.

What happens if a neuron fails to reach the threshold potential?

It will remain in its resting state with no action potential fired.

What is the axonal hillock?

The initial segment of the axon where the decision about action potential generation is made.

What role do sodium (Na+) ions play during an action potential?

They flood into the neuron to cause depolarization.

What occurs during the repolarization phase of an action potential?

Potassium (K+) channels open, allowing K+ to exit the cell.

What can result from an over-correction during repolarization?

Hyperpolarization, where membrane potential dips below resting potential.

How does the conduction of action potentials differ in myelinated vs. unmyelinated axons?

Myelinated axons conduct faster through saltatory conduction; unmyelinated axons conduct slower due to sequential channel opening.

What is saltatory conduction?

The process where action potentials jump from one Node of Ranvier to another in myelinated axons.

What is the Central Nervous System (CNS) composed of?

The brain and spinal cord.

What are the protective layers encasing the CNS called?

The meninges.

What are the three layers of the meninges?

Dura mater, arachnoid mater, and pia mater.

What is the function of cerebrospinal fluid (CSF)?

To provide buoyancy, act as a shock absorber, and facilitate nutrient transport.

How is the spinal cord organized?

Into segments corresponding to different body regions.

What is the role of the spinal cord in the nervous system?

To conduct signals between the brain and the rest of the body.

What does the cerebrum control?

Higher cognitive functions.

What is the primary function of the cerebellum?

Coordination of motor activity and balance.

What essential functions does the brainstem control?

Breathing and heart rate.

What is the role of the ascending pathways in the spinal cord?

To transmit sensory signals to the brain.

What is the role of the descending pathways in the spinal cord?

To transmit motor commands from the brain to the body.

Why is the integrity of the CNS important?

It enables complex behaviors, reflex responses, and cognitive activities.

What is the relationship between different regions of the CNS?

Their synchronized interplay maintains homeostasis and responds to environmental changes.

What does integration of synaptic inputs ensure?

That only significant signals lead to action potentials.

What is hyperpolarization?

A state where the membrane potential is below its resting potential.

What type of input does an excitatory neurotransmitter provide?

Facilitates depolarization.

What type of input does an inhibitory neurotransmitter provide?

Prompts hyperpolarization.

What happens when the total excitatory inputs outweigh inhibitory inputs?

The neuron is likely to generate an action potential.

What is the resting potential of a typical neuron?

Approximately -70 millivolts.

What channels open during depolarization of a neuron?

Voltage-gated sodium channels.

What occurs after the peak of an action potential?

Repolarization begins.

What prevents ion leakage in myelinated axons?

Myelin sheaths act as insulators.

What is the purpose of the protective meninges?

To stabilize CNS structure and protect against trauma.

What does the communication between neurons rely on?

Action potentials and synaptic transmission.

What facilitates the exit of potassium ions during repolarization?

Voltage-gated potassium channels.

What must happen for an action potential to be generated?

Sufficient depolarization to reach the threshold potential.

What are the important physiological mechanisms during action potential?

Depolarization, repolarization, and hyperpolarization.

What is the significance of the threshold potential in neuronal firing?

It determines whether an action potential will be initiated.

How does the structure of neurons affect their function?

Neuronal adaptations like myelination enhance conduction speed and efficiency.

What type of conduction occurs in unmyelinated axons?

Continuous conduction.

What do Nodes of Ranvier facilitate in myelinated axons?

Saltatory conduction.

What is the function of the CNS as a whole?

To process information and coordinate bodily functions.

How is the brainstem crucial for survival?

It controls essential life functions.

What percentage of the nervous system is the CNS comprised of?

It comprises a significant percentage, as it is crucial for coordination.

What is the role of the cortex in brain function?

Involved in sensory processing and voluntary movement control.

What protective role does CSF serve in the CNS?

Acts as a shock absorber and nutrient transporter.

How do the basal nuclei contribute to brain function?

They assist in the control of voluntary movements.

What can occur if the spinal cord is damaged?

It can affect reflexes and motor control.

What do sensory neurons respond to?

External stimuli such as touch and temperature.

What type of neurons carry signals away from the CNS?

Motor neurons.

How does the myelination of axons affect speed of conduction?

Myelination increases action potential conduction speed.

What is one advantage of having a myelinated axon?

Increased efficiency in signal transmission.

What role does the dorsal root play in the spinal cord?

It contains sensory neurons entering the spinal cord.

What does the ventral root of the spinal cord contain?

Motor neurons exiting the spinal cord.

What is the action potential's propagation along the axon called?

Propagation.

How does the neuron determine if an action potential will fire?

By integrating excitatory and inhibitory inputs.

What are the key components of the Central Nervous System?

Brain and spinal cord.

What are the roles of the different regions of the brain?

Cerebrum: higher functions, Cerebellum: motor coordination, Brainstem: life functions.

What does K+ efflux help to reestablish after an action potential?

Resting membrane potential.

Define hyperpolarization in terms of membrane potential.

A state in which the membrane potential is less than the resting level.

What is the purpose of summation in a postsynaptic neuron?

To integrate various excitatory and inhibitory inputs.

What is the role of chloride ions (Cl-) during synaptic integration?

They may contribute to inhibitory signals.

How does sodium ion influx contribute to action potentials?

It causes depolarization necessary for triggering action potentials.

Why is rapid communication between neurons essential?

It facilitates quick reflexes and coordinated responses.

What is the significance of the axonal hillock in neural signaling?

It's where the decision regarding firing an action potential is made.

Describe the primary protection of CNS against trauma.

Meninges and cerebrospinal fluid act as cushions and protectors.

What is the role of the autonomic system in relation to CNS function?

Regulate involuntary body functions.

What happens at the synapse during neurotransmitter release?

Neurotransmitters bind to receptors on the postsynaptic neuron.

What is the impact of an inhibitory neurotransmitter at the postsynaptic membrane?

It causes hyperpolarization, making the neuron less likely to fire.

What do sensory neurons do?

Transmit signals from sensory receptors to the CNS.

What is the functional importance of the myelin sheaths?

They increase the speed of electrical impulses.

What contributes to the slowing of nerve conduction in unmyelinated neurons?

Uniform distribution of voltage-gated channels.

What is a potential result of neurotransmitter imbalance in synaptic function?

Disruption in neuronal communication and signaling.

How does a neuron 'decide' to fire an action potential?

By integrating the total amount of excitatory and inhibitory signals.

What occurs when an action potential reaches the axon terminal?

Neurotransmitters are released into the synaptic cleft.

What are reflex arcs and their significance in the CNS?

They allow for rapid responses to stimuli without direct involvement of the brain.

What is the role of the spinal cord in reflex actions?

It processes and initiates reflex responses independently of the brain.

What is the importance of the Central Nervous System to overall body function?

It orchestrates a vast amount of bodily operations and responses.

In what condition would a postsynaptic neuron not fire an action potential?

If inhibitory inputs exceed excitatory inputs.

What cellular structures are involved in initiating the action potential?

Voltage-gated sodium and potassium channels.

What is the function of the limbic system?

It is involved in emotion, memory, and behavior regulation.

What role does the thalamus play in the CNS?

It acts as the relay station for sensory information to the cortex.

What does the hypothalamus regulate?

Homeostasis, including temperature, hunger, and thirst.

What is the role of glial cells in the CNS?

They support and protect neurons, aiding in their function.

How does the brain process sensory information?

Sensory information is received and interpreted in designated brain regions.

What is the midbrain responsible for?

It is involved in vision, hearing, and motor control.

What are the primary functions of the parietal lobe?

Processing sensory information and spatial orientation.

What is the function of the occipital lobe?

It is responsible for visual processing.

What does the temporal lobe process?

Auditory information and language comprehension.

What is neuroplasticity?

The brain's ability to reorganize itself by forming new neural connections.