Nerve Physiology Flashcards by Adrian Tiglao

It is a communications and control network that allows an organism to interact rapidly and adaptively with its environment, where environment includes both the external environment (the world outside the body) and the internal environment (the components and cavities of the body)

Nervous System

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It involves the brain and spinal cord

CNS

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It involves nerves and ganglia (group of neurons)

PNS

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These are the 💡major cell type in the nervous system.

Neurons and Glia

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It functions as 💡generation of signals (to be sent to other neurons or effector cells [e.g., muscle cells]) based on an integration of its own electrical properties with electrochemical signals from other neurons.

Neuron

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It is the points where specific neuron-to-neuron communication occurs.

Synapses

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It is critical to neuronal function.

Synaptic transmission

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Nerve glue

Neuroglia/ glia

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It is characterized as 💡supportive cells that sustain neurons both metabolically and physically, isolate individual neurons from each other, and 💡help maintain the internal milieu of the nervous system.

Neuroglia/ glia

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These are the three main cellular compartments of neurons:

Cell body
Dendrites
Axon

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It is the other name for the cell body.

Perikaryon

Soma

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It is the 💡main genetic and metabolic center of the neuron

It possesses a well-developed biosynthetic apparatus for manufacturing membrane constituents, synthetic enzymes, and other chemical substances needed for the specialized functions of nerve cells.

It contains numerous 💡mitochondria and cytoskeletal elements, including neurofilaments and microtubules.

It is also a region in which the 💡neuron receives synaptic input.

Cell body

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These are 💡neuronal biosynthetic apparatus which are stacks of 💡rough endoplasmic reticulum, and a prominent 💡Golgi apparatus.

Nissl bodies

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These are 💡tapering and branching extensions of the soma and are the main direct recipients of signals from other neurons.

They expand and specialize the surface area of a neuron and they account for more than 90% of the surface area available for synaptic contact.

Dendrites

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Two division of dendrites:

Primary dendrites

Higher-order dendrites

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Those that extend directly from the soma

Primary dendrites

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The daughter branches extending from a more proximal branch, in which proximal refers to closeness to the soma.

Higher-order dendrites

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Neuron’s set of dendrites

It can consist of just a few unbranched dendrites or of many highly ramified dendrites.

Dendritic tree

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It is a morphological variation of dendrite which are 💡small mushroom- or lollipop-shaped protrusions from the main dendrite.

These are the sites specialized for 💡synaptic contact (usually, but not always) from excitatory inputs.

Spines

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It is an 💡extension of the cell that 💡conveys the output of the cell to other neurons or, in the case of a motor neuron, to muscle cells as well.

Axon

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Each neuron has only __ axon, and it is usually of uniform diameter.

one

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It is a spray of branches seen in axon which is represented by the four terminal branches and their synaptic terminals

Terminal arborization

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The __, __, and __ of the terminal arborization determine which other cells it will contact.

size, shape, and organization

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It is the the 💡first part of the axon

It is the site where 💡action potentials (spikes) that are propagated down the axon are initiated.

Initial segment

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It is a specialized region where initial segment of the axon arise from the soma/ in the proximal dendrite.

Axon hillock

The axon differs from the soma and proximal dendrites in that it lacks __, __, and __.

rough endoplasmic reticulum, free ribosomes, and a Golgi apparatus.

What makes neuron special?

because of their ability to control and respond to electricity

Dendrites have __ that allow neurons to respond to chemicals released by other neurons, and their characteristic branching pattern allows for integration of multiple input signals.

ligand gated ion channels

Axon typically has a long length and high concentration of __ that allows it to convey electrical signals (action potentials) rapidly over long distances without alteration.

voltage-gated channels

What will happen to axon when they disconnected from the cell body?

They will degenerate because they are metabolically dependent to the soma.

Membrane-bound organelles and mitochondria are transported relatively rapidly by __.

fast axonal transport

Substances that are dissolved in cytoplasm (e.g., proteins) are moved by __.

slow axonal transport

What is the role of calcium in the axonal transport?

It triggers movement of the organelles along the microtubules.

Special microtubule-associated motor proteins called __ and __ are required for axonal transport.

kinesin and dynein

It is an axonal transport from the 💡soma toward the axonal terminals. This process involves 💡kinesin, and it allows 💡replenishment of synaptic vesicles and enzymes responsible for the synthesis of neurotransmitters in synaptic terminals.

anterograde axonal transport

It is an axonal transport in the 💡opposite direction, which is driven by 💡dynein. This process returns 💡recycled synaptic vesicle membrane to the soma for lysosomal degradation.

retrograde axonal transport

Clostridium tetani is transported __ in the axons of motor neurons. The toxin can escape into the extracellular space of the spinal cord ventral horn and block the synaptic receptors for inhibitory amino acids. This process can result in tetanic convulsions.

Retrogradely

It is the major non neuronal cellular elements of the nervous system. It includes: CNS: astrocytes, oligodendrocytes, microglia, and ependymal cells PNS: Schwann cells and satellite cells

Glia

Glial cells in the human CNS outnumber neurons by an order of magnitude: there are about __ glia and __ neurons.

10^13 10^12

FUNCTIONS OF Glial Cells:

1. regulation of the microenvironment and myelination of axons 2. important determinants of the flow of signals through neuronal circuits 3. they act to modulate synaptic and nonsynaptic transmission 4. important roles in synaptogenesis and maintenance.

It is a glial cell that help 💡regulate the microenvironment of the CNS, both under normal conditions and in response to damage to the nervous system. They serve to 💡buffer the extracellular environment of neurons with respect to both ions and neurotransmitters. They actively take up K+ ions and neurotransmitters.

Astrocytes

What is the function of foot processes in astrocytes?

help mediate the entry of substances into the CNS

It is found in the cytoplasm of astrocytes that 💡provide mechanical support for CNS tissue.

Glial filaments

These are glial cells critical for the function of axons.

Oligodendrocytes and Schwann cells

It is a 💡spiral multilayered wrapping of glial cell membrane that 💡surrounds the axons

Myelin sheath

It forms the myelin sheath in the 💡CNS.

OLIGODENDROCYTES

It forms the myelin sheath in the 💡PNS.

SCHWANN CELLS

Myelin increases the __ conduction, in part by restricting the flow of ionic current to small unmyelinated portions of the axon between adjacent glial cells, the nodes of Ranvier

speed of action potential

It is a 💡small unmyelinated portions of the axon between adjacent glial cells.

NODES OF RANVIER

What is the difference of oligodendrocyte and Schwann cell?

Oligodendrocyte typically helps myelinate 💡multiple axons in the CNS while each Schwann cell helps myelinate 💡only a single axon in the PNS. Unmyelinated axon are seen in many in the PNS. (Surrounded by Schwann cell processes) Does not form a multilayered covering (i.e., myelin), but instead extends processes that surround parts of several axons.

It is the Schwann cell with its 💡set of unymyelinated axons.

Remak bundle

It encapsulate 💡dorsal root and 💡cranial nerve ganglion cells and regulate their microenvironment in a fashion similar to that of astrocytes.

Satellite cells

These are derived from 💡erythromyeloid stem cells that 💡migrate into the CNS early in development. They play an important role in 💡immune responses within the CNS. When the CNS is damaged, they help remove the cellular products of the damage by phagocytosis.

Microglia

It form the 💡epithelium lining the ventricular spaces of the brain, which contain (cerebrospinal f luid) CSF

Ependymal cells

They secrete CSF

Specialized ependymal cells of the choroid plexuses

Most neurons in the adult nervous system are __.

Postmitotic cells

The cellular elements that give rise to most intrinsic brain tumors in the adult brain are the __.

Glial cells

It provides an 💡interface between the environment and the CNS, both for sensory information flowing to the CNS and for motor commands issued from the CNS. It includes sensory (or primary afferent) neurons, somatic motor neurons, and autonomic motor neurons.

PNS

These action potentials contain information about the sensory stimulus that is conveyed to the CNS via the primary afferent.

Receptor potential

Regions of the CNS containing 💡high concentrations of axon pathways (and very few neurons) because the axonal myelin sheaths of the axons are 💡highly refractive to light..

White matter

Regions containing 💡high concentrations of neurons and dendrites. (Also axons)

Gray matter

Gray matter exists in two main configurations in the CNS:

Nucleus | Cortex

It is a group of neurons in the CNS.

Nucleus

It is a group of neurons in the PNS.

Ganglion

It is neurons that are 💡organized into layers and usually found on the 💡surface of the CNS

Cortex

In most nuclei and cortices, one can classify neurons into two broad categories:

projection cells and local interneurons.

These are neurons that 💡send their axon to another region and thus are the origins of the various tracts of the nervous system.

Projection cells

They have 💡axons that terminate in the same neural structure as their cell of origin and are involved with 💡local computations rather than conveying signals from one region to another.

Local interneurons

CSF fills the:

Ventricular system (series of interconnected spaces within the brain) Subarachnoid space (directly surrounding the brain)

It reflects the 💡composition of the brain’s extracellular space via free exchange across the ependyma, and the brain “floats” in the subarachnoid CSF to minimize the effect of external mechanical forces.

Intraventricular CSF

The volume of CSF within the cerebral ventricles is approximately __, and that in the subarachnoid space is about __.

30 mL 125 mL

How many mL of CSF is produced each minute?

0.35mL

It is a filtrate of capillary blood formed largely by the choroid plexuses, which comprise pia mater, invaginating capillaries, and ependymal cells specialized for transport.

CSF

The choroid plexuses are located in the __.

lateral, third, and fourth ventricles

These are situated within the 💡two cerebral hemispheres.

Lateral ventricles

Lateral ventricles each connect with the third ventricle through one of the __.

interventricular foramina (of Monro)

It lies in the midline between the 💡diencephalon on the two sides.

Third ventricle

It traverses the 💡midbrain and connects the third ventricle with the fourth ventricle.

cerebral aqueduct (of Sylvius)

It is a space defined by the 💡pons and medulla below and the cerebellum above.

fourth ventricle

CSF escapes from the ventricular system through three apertures or foramina:

a medial foramen of Magendie two lateral foramina of Luschka (located in the roof of the fourth ventricle.)

CSF has a lower concentration of __ but a greater concentration of __ than blood does.

K+, glucose, and protein Na+ and Cl−

The increased concentration of Na+ and Cl− enables CSF to be __ to blood.

isotonic

The pressure in the CSF column is about __ when a person is recumbent.

120 to 180 mm H2O

The rate at which CSF is formed is relatively __ in the ventricles and subarachnoid space, as well as systemic blood pressure. However, the absorption rate of CSF is a __.

independent of the pressure direct function of CSF pressure

Obstruction of the circulation of CSF leads to __ and __, an abnormal accumulation of fluid in the cranium.

increased CSF pressure hydrocephalus

When the obstruction is within the 💡ventricular system or in the foramina of the fourth ventricle, the condition is called a __.

noncommunicating hydrocephalus

If the obstruction is in the 💡subarachnoid space or the arachnoid villi, it is known as a __.

communicating hydrocephalus

The __ is at least partly due to the barrier action of the capillary endothelial cells of the CNS and the tight junctions between them.

Blood-brain barrier

Once a neuron is lost it cannot be __ because, in general, neurons are postmitotic cells.

replaced

Only for the __ has evidence been found for significant levels of neurogenesis in the adult CNS.

hippocampus

It is the process of degeneration where the neuron attempts to repair the axon by making new 💡structural proteins, and the 💡cisterns of the rough endoplasmic reticulum become distended with the products of protein synthesis. The 💡ribosomes appear to be disorganized, and the 💡Nissl bodies are stained weakly by basic aniline dyes. The 💡soma may swell and become rounded, and the 💡nucleus may assume an eccentric position.

chromatolysis

If the axon had been a myelinated axon in the CNS, the myelin sheath would also fragment and eventually be removed by phagocytosis. However, in the PNS the Schwann cells that had formed the myelin sheath remain viable, and in fact they undergo cell division.

wallerian degeneration.

If the axons that provide the sole or predominant synaptic input to a neuron or to an effector cell are interrupted, the postsynaptic cell may undergo __ and even __.

Transneuronal degeneration Death

The rate of regeneration is limited by the rate of slow axonal transport to about __.

1 mm/day