Chapter 1: Basic Neurophysiology

What is neuroscience?

The scientific investigation of the nervous system, integrating physics, chemistry, and biology.

What are the three levels of analysis in neuro and occupational therapy?

Biological level (cellular, molecular), Systems level (cognitive, motor, sensory), Functional level (ADLs, IADLs, work, school, community).

What are neurons?

Excitable, highly specialized cells that are interconnected and form circuits and networks for processing information.

What is the function of glial cells?

Support and nurture neurons, provide nutrition, myelination, immunity, and clean up debris.

What is the role of the neuron cell body (soma)?

Contains the nucleus and organelles, provides energy, and synthesizes proteins for regeneration and propagation of electrical signals.

What are dendrites?

Extensions from the neuron cell body that receive signals from other neurons and can branch into complex patterns.

What is the axon?

A long extension that transmits electrical signals from the cell body to the axon terminals, which can be wrapped in a myelin sheath.

What are axon terminals?

Fine branches that form communication sites with other neurons, often ending on the dendrites of adjacent neurons.

What are afferent neurons?

Neurons that carry information from the periphery to the central nervous system (CNS).

What are efferent neurons?

Neurons that carry information from the CNS to the periphery.

What is a multipolar neuron?

A neuron with one axon and many dendrites, most abundant in the brain and spinal cord.

What is a pseudounipolar neuron?

A neuron with one process that branches into two, mainly found in spinal ganglia to relay sensory information.

What is a bipolar neuron?

A neuron with one axon and one dendrite, found in the retina and olfactory epithelium.

What is a synapse?

The contact point between two neurons, allowing for communication.

What are the three types of synaptic contacts?

Axodendritic (axon to dendrite), Axosomatic (axon to soma), and Axoaxonic (axon to axon).

What are astrocytes?

Star-shaped glial cells that maintain the neuron's environment, support neurons, and contribute to the blood-brain barrier.

What are oligodendrocytes?

Myelinating cells in the CNS that insulate and protect axons by producing myelin.

What role do microglia play in the brain?

They act as immune cells, removing toxic agents and dead cells, and are involved in synaptic pruning.

What is the function of ependymal cells?

They line the spinal cord and ventricles of the brain, involved in creating cerebrospinal fluid (CSF).

What is the blood-brain barrier (BBB)?

A semi-permeable barrier formed by tightly fitting endothelial cells that protects the brain from foreign substances.

What factors can affect the blood-brain barrier?

Hypertension, developmental abnormalities, radiation, infections, trauma, ischemia, and inflammation.

What is resting membrane potential?

The electrical potential of a neuron at rest, typically around -70 mV, where the inside is negative relative to the outside.

What initiates an action potential in a neuron?

A sufficient stimulus that raises the membrane voltage above the threshold level, leading to depolarization.

What occurs during depolarization?

Gated ion channels open, allowing Na+ ions to rush into the cell, changing the membrane potential.

What is repolarization?

The process where K+ ions move out of the cell after depolarization, restoring electrical balance.

What is hyperpolarization?

A state where the membrane potential becomes more negative than the resting potential due to excess K+ outside.

What is the refractory period?

The time following an action potential during which a neuron cannot fire another action potential until it returns to resting state.

What is the resting membrane potential of a neuron?

-70mV, maintained by Na+, K+ pump and large negative ions inside.

What happens during depolarization in a neuron?

The resting potential moves toward 0 mV, and if it reaches -55mV, an action potential is fired.

What is the 'ALL OR NONE' principle in action potentials?

Once the threshold level is reached, an action potential of a fixed size will always fire.

What defines hyperpolarization in a neuron?

A membrane potential less than -70 mV, which is inhibitory.

What defines depolarization in a neuron?

A membrane potential greater than -70 mV, which is excitatory.

What is synaptic transmission?

The biological process by which a neuron communicates with a target cell across a synapse.

What are the two types of synaptic transmission?

Electrical (transfer of electrical signals through gap junctions) and Chemical (release of neurotransmitters).

What initiates the release of neurotransmitters in synaptic transmission?

An action potential causes calcium gates to open, allowing Ca2+ to enter the cell.

What occurs when neurotransmitters bind to receptors on the post-synaptic neuron?

Post-synaptic channels either open or close, causing depolarization or hyperpolarization.

What is the role of excitatory postsynaptic potential (EPSP)?

It depolarizes the membrane potential, making it easier to reach action potential threshold.

What is the role of inhibitory postsynaptic potential (IPSP)?

It hyperpolarizes the membrane potential, making it harder to reach action potential threshold.

What is summation in the context of synaptic transmission?

The cumulative effect of thousands of synapses on a postsynaptic neuron to elicit a new action potential.

What is the major neurotransmitter in the peripheral nervous system (PNS)?

Acetylcholine (ACh), which activates motor neurons controlling skeletal muscles.

What condition is associated with low levels of acetylcholine?

Alzheimer's disease, where patients have abnormally low levels of ACh.

What is norepinephrine's role in the body?

It is involved in the 'fight or flight' response, increasing heart rate and blood pressure.

What is the primary function of GABA (gamma-aminobutyric acid)?

It serves as a major inhibitory neurotransmitter in the CNS, preventing excessive neural activity.

What is dopamine associated with?

Motor control, reward mechanisms, and positive emotions; low levels are linked to Parkinson's disease.

What is glutamate's role in the brain?

It is the most common excitatory neurotransmitter, critical for learning and memory.

What are the effects of low serotonin levels?

Associated with depression, anger control issues, and various physical ailments.

What are endorphins and their function?

Inhibitory neurotransmitters involved in pain reduction and pleasure, similar to opioids.

What is the function of ligand-gated channels?

They open or close in response to neurotransmitter binding, affecting ion flow in the post-synaptic neuron.

What is the significance of the nodes of Ranvier in myelinated axons?

They allow action potentials to jump from node to node, increasing signal transmission speed.

What is the effect of amphetamines on neurotransmitters?

They cause the release of norepinephrine, dopamine, and serotonin, enhancing alertness and mood.

What is the role of calcium ions (Ca2+) in synaptic transmission?

They trigger the fusion of synaptic vesicles with the presynaptic membrane to release neurotransmitters.

What is the process of neurotransmitter recycling?

Used neurotransmitters are taken up from the synapse and recycled into new vesicles for future use.