Neurology Foundations Quiz OCCTH 583

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Questions and Answers

What effect do inhibitory neurotransmitters have on the post-synaptic membrane?

They increase the likelihood of an action potential.

They have no effect on the post-synaptic membrane.

They hyperpolarize the membrane, making it more negative. (correct)

They depolarize the membrane, making it more positive.

Which of the following neurotransmitter types includes dopamine and epinephrine?

Peptides

Amino acids

Amines (correct)

Neuropeptides

Which process involves reabsorbing neurotransmitters back into the presynaptic neuron?

Diffusion

Inhibition

Desensitization

Reuptake (correct)

How do drugs classified as agonists affect neurotransmitter activity?

They mimic neurotransmitters and enhance their effects. Signup and view all the answers

What occurs when there is loss of post-synaptic receptors due to drug influence?

More of the substance is required to achieve the same effect. Signup and view all the answers

What characterizes the resting membrane potential of a neuron?

More negative charge inside than outside Signup and view all the answers

What is the primary function of interneurons?

Stimulate tissues through neurotransmitters Signup and view all the answers

Which type of neuron is most commonly found in the nervous system?

Multipolar Signup and view all the answers

What does the term 'membrane potential' refer to?

The difference in electrical charges across a membrane Signup and view all the answers

Which of the following statements about neuronal transmission is true?

Neurons transmit one signal at one strength and speed Signup and view all the answers

What type of charge separation is primarily maintained by the neuronal membrane?

Positive outside and negative inside Signup and view all the answers

Which type of neuron is primarily associated with sensory functions?

Unipolar Signup and view all the answers

What is the role of the phospholipid bilayer in the neuronal membrane?

It creates resistance to current flow Signup and view all the answers

What is the primary function of astrocytes in the CNS?

Regulate the chemical content of extracellular space Signup and view all the answers

Which type of neuroglia acts as macrophages in the CNS?

Microglial cells Signup and view all the answers

What distinguishes oligodendrocytes from Schwann cells?

Oligodendrocytes can contribute myelin to multiple axons Signup and view all the answers

In the context of the nervous system, the autonomic nervous system primarily regulates:

Involuntary body functions Signup and view all the answers

Which of the following glial cells produces cerebrospinal fluid (CSF)?

Ependymal cells Signup and view all the answers

What role do satellite cells play in the PNS?

They surround and support neuron cell bodies. Signup and view all the answers

What is primarily responsible for the 'fight or flight' response in the autonomic nervous system?

Sympathetic division Signup and view all the answers

Which cells fill most of the space between neurons and provide neuroprotective functions?

Astrocytes Signup and view all the answers

What is the resting membrane potential of a neuron?

-70 mVolts Signup and view all the answers

Which type of ion channel opens in response to a change in membrane potential?

Voltage-Gated Signup and view all the answers

What occurs during the depolarization phase of an action potential?

Na+ channels open and Na+ rushes in Signup and view all the answers

What happens during the repolarization phase of the action potential?

The cell becomes hyperpolarized to around -75 mVolts Signup and view all the answers

How does conduction velocity vary among different neurons?

Faster in myelinated axons Signup and view all the answers

What is the primary function of excitatory neurotransmitters?

To enhance the transmission of the chemical message Signup and view all the answers

Which of the following describes synaptic transmission?

Chemical synaptic transmission is more selective and precise Signup and view all the answers

What key role does the sodium-potassium pump play in a neuron?

It restores the resting potential by pumping Na+ out and K+ in Signup and view all the answers

What occurs at the presynaptic terminal when an action potential reaches it?

Voltage-gated Ca2+ channels open allowing Ca2+ influx Signup and view all the answers

Which change in frequency corresponds to a weak stimulus during action potentials?

Lower frequency of action potentials Signup and view all the answers

Study Notes

Course Information

Course name: OCCTH 583
Course title: Neurology Foundations
Instructor: Jennifer Krysa, MSc, Registered Occupational Therapist (AB)
University: University of Alberta

Acknowledgements

Images are obtained from SciDraw (https://scidraw.io/) and Wikimedia Commons.

Objectives

Describe neurons and neuroglia functions
Understand synaptic transmission (electrical and chemical)

Nervous System Review

CNS (central nervous system): brain and spinal cord, the control center
PNS (peripheral nervous system): nerves branching from CNS, carrying information to and from CNS
- Sensory (afferent): sends sensory stimuli to CNS
- Motor (efferent): sends info from CNS to muscles and glands
  - Somatic NS: voluntary muscle control
  - Autonomic NS: involuntary bodily functions (e.g., heart rate, respiration)
    - Sympathetic division: fight or flight response
    - Parasympathetic division: rest and digest response

Cells

Neurons: the actual nerve cells; conductive
Neuroglia (glial cells): support neurons; non-conductive

Glial Cell Types

CNS: Astrocytes, Microglial cells, Ependymal cells, Oligodendrocytes
PNS: Satellite cells, Schwann cells

Astrocytes

Most abundant glial cell type in CNS
Anchors neurons to blood supply
Fills space between neurons
Metabolic and homeostatic support
Regulates chemical content in extracellular space
Neuroprotective (restricts spread of released neurotransmitters)
Stabilizes and regulates blood-brain barrier

Microglial Cells

CNS macrophages
Removes damaged neurons and infectious microorganisms in the brain and spinal cord

Ependymal Cells

CNS
Forms epithelial layer lining ventricles in the brain and central canal of spinal cord
Produces cerebrospinal fluid (CSF) in the choroid plexus and controls CSF flow

Oligodendrocytes

CNS
Produces myelin sheath
Electrical insulation for axons
Contributes myelin to multiple axons

Satellite Cells

PNS
Equivalent of astrocytes
Surrounds and supports neuron cell bodies

Schwann Cells

PNS
Equivalent of oligodendrocytes
Produces myelin sheath
Contributes myelin to a single axon

Neurons

High longevity, the same as your lifespan.
Non-replaceable; they don't divide (amitotic)
High metabolic rate
Require glucose and oxygen

Neuron Structure

Soma (cell body): contains cytosol and cell organelles
Dendrites: receive impulses to the cell body
Axon: transmits impulses away from the cell body to other cells
Neuronal membrane: separates the neuron's interior from the exterior
Associated proteins: function as pumps

Neuron Shape

Unipolar: rare, mostly sensory
Bipolar: rare, specialized sensory (e.g., retina)
Multipolar: most common

Interneurons (Association Neurons)

Exclusively in CNS
99% of all neurons
Multipolar
Stimulate tissues through neurotransmitters
Assemble to form circuits
Involved in higher brain functions (e.g., cognition, perception)

Neuronal Transmission - Electrochemical

Neurons transmit one signal at steady strength and speed
Nerve impulse frequency can vary
Body has equal +ve and -ve charges, but localized areas can be more charged one way (opposing charges attract; same charges repel)

Membrane Potential

Electrical charges separated by the membrane create electrical potential (voltage).
Difference in electrical charges is membrane potential.
Larger difference = higher voltage
Membrane is a phospholipid bilayer
Membranes resist current flow
- Conductors have low resistance
- Insulators have high resistance
Measured in millivolts in the body

Resting Membrane Potential

Resting neuron has more negative charge inside than outside
Difference in electrical charge across a membrane when the neuron is at rest = resting membrane potential
-70mV

Sodium Potassium Pump

Ion pump formed by proteins
Na+ and Ca2+ more concentrated outside the membrane
K+ more concentrated inside the membrane along with negatively charged proteins
Polarized due to negative charge inside the cell

Types of Ion Channels

Ions diffuse across the membrane through ion channels (protein spans the membrane)
- Voltage-gated: open and close at specific membrane potentials
- Ligand-gated: open when a specific neurotransmitter, drug, or hormone attaches to it
- Mechanically-gated: open when the membrane is physically stretched

Action Potential (AP)

Nerve impulse
Brief reversal of resting membrane potential
Stimulus opens ion channels
- Na channels open
Significant stimulus opens voltage-gated channels
- At -55mV, voltage-gated Na channels open
- All-or-none phenomenon
Na rushes into the cell, briefly depolarizing it (+40mV)

AP - Propagation

When a few voltage-gated channels open it causes a cascading effect down the axon
Local current is strong enough to change neighboring gates

AP - Repolarization

Voltage-gated K+ channels open, releasing K+ into extracellular space to rebalance charges
Briefly hyperpolarizes to ~-75mV then Na+/K+ restores balance
Followed by a refractory period

AP - Signals

Strength of AP is always the same
Frequency changes with stimulus intensity
- Weak stimulus = lower frequency
- Strong stimulus = higher frequency
Conduction velocity is variable
- Fastest in myelinated axons (Saltatory conduction via Nodes of Ranvier)

Synaptic Transmission

Electrical: Immediate, via gap junctions; electrical impulses are never converted
Chemical: Slower
- More common
- More selective and precise
- Uses neurotransmitters
- Signal converted: electrical -> chemical -> electrical

Synapses - continued

Presynaptic neuron interfaces with dendrites, axon soma, or another axon at synaptic cleft
AP travels down neuron, activating Na+/K+ channels in presynaptic terminal
Activates voltage-gated Ca2+ channels; Ca2+ enters cytoplasm
Causes synaptic vesicles to fuse with presynaptic membrane; neurotransmitters released into synaptic cleft

Neurotransmitters

Diffuse across synaptic gap and bind to receptor sites on postsynaptic neuron
Binding causes ion channels to open
Neuron excited or inhibited
Neurotransmitters bind to receptors

Excitatory Neurotransmitters

Excite the neuron, transmitting the chemical message to the next cell
Depolarizes the postsynaptic neuron (makes inside more positive)
Closer to threshold for AP

Inhibitory Neurotransmitters

Block or slow further chemical message transmission
Hyperpolarizes the postsynaptic membrane (makes inside more negative)
Pushes further from threshold

Summary/Conclusion about AP

Likelihood of postsynaptic neuron developing an action potential depends on the sum of excitatory and inhibitory influences in that area
Signal is transmitted in the form of neurotransmitters which are released, unbind, reabsorbed, and broken down
Neurotransmitter reuptake at presynaptic membrane

Types of Neurotransmitters

Amino acids (e.g., glutamate, GABA, glycine)
Amines (e.g., acetylcholine, serotonin, dopamine, epinephrine, norepinephrine, histamine)
Neuropeptides (e.g., enkephalins, cholecystokinin)

Drugs & Toxins

Mimic neurotransmitters or block postsynaptic receptors
Promote or inhibit neurotransmitter production/release
Affect neurotransmitter reuptake (accumulate in cleft)
Can lead to loss of postsynaptic receptors (need more of the substance to feel effect).

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Description

Test your understanding of the nervous system, including the roles of neurons and neuroglia, as well as synaptic transmission. This quiz covers both central and peripheral nervous system functions, including sensory and motor pathways. Gain insights into the autonomic divisions for a comprehensive understanding of bodily functions.