Neuroscience Quiz: Action Potentials and Synapses

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Questions and Answers

What occurs during the depolarization phase of an action potential?

K+ flows into the cell, making it more negative.

Na+ flows into the cell, depolarizing it towards zero. (correct)

Na+ channels inactivate and K+ channels begin to open.

Ligand-gated Na+ channels open in response to neurotransmitters.

What is the membrane potential value at the action potential threshold?

-55 mV (correct)

-60 mV

-70 mV

-50 mV

Which of the following statements accurately describes the refractory period?

It occurs only during the depolarization phase.

It prevents Na+ from entering the cell during repolarization.

It ensures one-way transmission of the action potential. (correct)

It allows both forward and backward transmission of action potentials.

What is the function of the Na+/K+ ATPase pump after an action potential?

To restore the resting membrane potential after an action potential. Signup and view all the answers

During which phase of the action potential do K+ ions mainly move out of the cell?

Repolarization Phase Signup and view all the answers

What occurs during the Absolute Refractory Period of an action potential?

Voltage-gated Na channels are inactive and unable to trigger action potential Signup and view all the answers

What characterizes the Relative Refractory Period?

It occurs after the Absolute Refractory Period and requires a stronger stimulus to reach threshold Signup and view all the answers

What is the primary mechanism of signal transmission at a chemical synapse?

Release of neurotransmitters into the synaptic cleft Signup and view all the answers

Which of the following is NOT a step in the transmission of a signal within a chemical synapse?

Neurotransmitters diffuse through axoplasm Signup and view all the answers

What triggers the release of neurotransmitters from the presynaptic neuron?

Opening of voltage-gated Calcium channels Signup and view all the answers

Which method does NOT remove neurotransmitters from the synaptic cleft?

Blocking receptors on postsynaptic neurons Signup and view all the answers

What happens when neurotransmitters bind to ligand-gated ion channels on the postsynaptic membrane?

Depolarization occurs if Na+ channels open Signup and view all the answers

What is NOT true regarding electrical synapses?

They require the release of neurotransmitters. Signup and view all the answers

What is the primary consequence of injury to the cribriform plate?

Loss of sense of smell Signup and view all the answers

Which step in a reflex arc involves the transmission of impulses from sensory neurons to the central nervous system?

Sensory neuron transmission Signup and view all the answers

Which type of reflex arc contains only one synapse between sensory and motor neurons?

Monosynaptic reflex arc Signup and view all the answers

Where are the cell bodies of the preganglionic neurons located?

In the lateral horn of the spinal cord Signup and view all the answers

Which of the following structures is NOT part of the autonomic reflex pathway?

Sensory neuron Signup and view all the answers

In somatic reflexes, the signal to the effector is carried by how many myelinated neurons?

One Signup and view all the answers

What characterizes the sympathetic chain in the autonomic nervous system?

String of ganglia for neuron synapse Signup and view all the answers

Which type of reflex typically operates under voluntary control?

Somatic reflex Signup and view all the answers

What is one of the primary functions of Cerebral Spinal Fluid?

Shock absorption Signup and view all the answers

Which vessels are responsible for draining blood from the brain?

Dural Sinuses Signup and view all the answers

What does the Blood Brain Barrier primarily restrict?

Toxins Signup and view all the answers

In the cervical spinal region, how many pairs of spinal nerves exist?

8 pairs Signup and view all the answers

Where is the target location for a lumbar puncture?

At or below L1/L2 Signup and view all the answers

What unique feature do the dorsal root ganglia possess?

Contains only sensory cell bodies Signup and view all the answers

Which pair of arteries primarily supplies blood to the spinal cord?

Anterior Vertebral and intercostal Arteries Signup and view all the answers

Which of the following is excluded by the Blood Brain Barrier?

Antibiotics Signup and view all the answers

What is the primary function of the VII: Facial nerve?

Both sensory and motor, including taste and facial expressions Signup and view all the answers

Which cranial nerve is responsible for hearing and balance?

Vestibulocochlear Nerve Signup and view all the answers

What is the modality of the II: Optic nerve?

Sensory Signup and view all the answers

Which of the following cranial nerves has its function extend inferior to the head and neck region?

Vagus Nerve Signup and view all the answers

Which cranial nerve innervates muscles of mastication?

Trigeminal Nerve Signup and view all the answers

What is the cranial nerve responsible for intorsion of the eye?

Trochlear Nerve Signup and view all the answers

What structure can shear the fila olfactoria during a traumatic event?

Cribriform Plate Signup and view all the answers

What modality is associated with the XI: Accessory nerve?

Motor Signup and view all the answers

Which pathway allows the preganglionic neuron to synapse at the same level within the sympathetic chain?

Grey ramus communicans pathway Signup and view all the answers

What is the primary function of the sympathetic nervous system?

Trigger fight or flight responses Signup and view all the answers

Which type of membrane channel is activated by touch?

Mechanically gated ion channels Signup and view all the answers

Which description best relates to special senses?

Conversion of specific stimuli into electrical signals for the CNS Signup and view all the answers

How does the parasympathetic nervous system primarily affect heart rate?

Decreases heart rate Signup and view all the answers

When referring to the receptive field, what indicates a high ability to distinguish between stimuli?

High density of neurons Signup and view all the answers

What type of neuron distribution is characteristic of the parasympathetic nervous system?

Craniosacral distribution Signup and view all the answers

What triggers depolarization or action potentials in olfaction?

Odorant chemicals binding to olfactory cells Signup and view all the answers

Study Notes

Nervous System

The central nervous system (CNS) is made up of the brain and spinal cord.
A neuron is the basic building block of the nervous system, categorized by structure into multipolar, bipolar, and unipolar (pseudounipolar).
Multipolar are the most common type of neuron, characterized by multiple dendrites and one axon.
Bipolar neurons have one central dendrite and one axon, and are common in special senses, like relaying information from rods/cones to retinal ganglion cells in the optic nerve.
Unipolar (pseudounipolar) neurons have a single axo-dendritic process that splits into one axon and one dendrite; the soma is adjacent to the axo-dendritic process, which allows the signal to bypass the cell body.

Functional Classification of Neurons

Sensory (afferent) neurons carry signals from the peripheral nervous system (PNS) to the CNS.
Motor (efferent) neurons carry signals from the CNS to effectors (muscles or glands) in the PNS.
Interneurons make decisions based on incoming signals from afferent neurons and transmit the response signals to efferent neurons.

Neuroglia

CNS Neuroglia:
- Astrocytes maintain the blood-brain barrier and provide nutrients to neurons.
- Oligodendrocytes myelinate multiple axons in the CNS.
- Microglia fight off infection and clean up dead cells.
- Ependymal cells line fluid-filled spaces like ventricles and generate cerebrospinal fluid (CSF).
PNS Neuroglia:
- Schwann cells myelinate one segment of one axon in the peripheral nervous system (PNS).
- Satellite cells support and protect the cell bodies in ganglia.

Myelin and Conduction Speed

Myelin increases the speed of signal transduction by insulating the axon.
Larger-diameter axons conduct signals faster than smaller ones.
Myelinated axons are generally faster than unmyelinated.

Polarity and Na+/K+ Pump

Polarity is the separation of charge across a cell membrane; neurons have a resting membrane potential (RMP) of -70mV.
The Na+/K+ ATPase pump maintains the neuron's polarity by actively transporting 3 Na+ ions out of the cell and 2 K+ ions into the cell.

Facilitated vs. Active Transport

Facilitated diffusion requires only a membrane protein for ion movement, down the concentration gradient; no energy is used.
Active transport requires energy (ATP) and a membrane protein to move ions against their concentration gradients.

Graded Potentials

Graded potentials are local changes in membrane potential, often caused by the opening of ligand-gated channels in dendrites or the soma.
They are small deviations from the resting potential and are not large enough to trigger an action potential.

Action Potentials

Action Potential: A rapid, large change in membrane potential that propagates along the axon; caused by voltage-gated sodium channels.
Three main phases: depolarization, repolarization, and hyperpolarization.
Depolarization = Na+ influx making the inside of the membrane more positive.
Repolarization = K+ efflux restoring the negative membrane potential.
Absolute refractory period: another action potential cannot occur immediately after one occurs; relative refractory period: a larger stimulus is needed for an action potential to occur than during normal conditions.

Synaptic Transmission

Chemical Synapses:
- Neurotransmitters are released from the presynaptic neuron.
- Neurotransmitter binds to receptors on the postsynaptic neuron.
- Binding of the neurotransmitter triggers graded potentials or action potentials. (EPSPs and IPSPs.)
- Neurotransmitters are removed from the synaptic cleft by diffusion, enzymatic degradation, and/or reuptake

Blood Brain Barrier

The blood-brain barrier is formed by tightly connected epithelial cells that prevent the passage of many substances into the brain.

Spinal Cord Anatomy and Function

Vertebral levels correlate to spinal nerves. (Cervical, thoracic, lumbar, sacral, coccygeal)
The spinal cord contains grey and white matter, with specific structures like the dorsal and ventral roots, and horns.
Spinal nerves connect the spinal cord to the periphery.

Cranial Nerves

Cranial nerves are nerves that originate in the brain.
Each nerve has a specific function or functions, often involving both sensory and motor aspects.

Autonomic Nervous System

Autonomic reflexes typically involve two motor neurons: preganglionic and postganglionic, with a synapse within the CNS.
Sympathetic nervous system is responsible for the "fight-or-flight" response. The signals travel through a thoracolumbar pathway.
Parasympathetic nervous system is responsible for the "rest and digest" response. Signals travel through a craniosacral pathway.

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Description

Test your knowledge on the action potential, membrane potentials, and synaptic transmission in neuroscience. This quiz covers key phases like depolarization, refractory periods, and the role of neurotransmitters. Get ready to deepen your understanding of how nerve signals are transmitted!