Exam 1 Flashcards
Reticular Theory
It was postulated by Joseph von Gerlach in 1871. Said the nervous system was one continuous network. (popularized by Camillo Golgi.)
Cell Theory
All living organisms are composed of one or more cells. The cell is the most basic unit of life. All cells arise from pre-existing, living cells. So, the nervous system (described by the Reticular Theory) was considered an exception to the cell theory.
Early Neuron Doctrine
The nervous system is made up of discrete individual cells (neurons). These units are in close proximity, but separate from one another. Proposed by Santiago Ramon y Cajal. Discovered this when using Golgi staining on bird’s brains.
What was evidence of the Neuron Doctrine?
Individual neurons in the central nervous system. There were gaps in between neuron synapses.
Current Neuron Doctrine
Neural Units (the NS is made of discrete units called neurons), Neurons are cells (discrete units are cells), and Specialization (neurons differ in size, shape, and structure according to their location of functional specialization.)
How many neurons are there?
100 billion neurons
What are the cells of the Nervous system?
Neurons and Glia
What are the 3 types of neurons?
sensory, motor, and interneurons
What are the types of glia cells (5)?
astrocytes, ependymal cells, microglia, oligodendrocytes, schwann cells
Neuron
They carry our major brain functions. They are specialized for reception, conduction, and transmission of electrochemical cells. Convert electrical signals to chemical signals, then back to electrical signals.
What mechanisms do neurons use to communicate?
Chemical neurotranmission (between a neuron and its target) and electrical impulses (within neurons)
What does neurotransmission require?
Requires 2 neurons minimum- one presynaptic neuron (cell sending the singal) and one postsynaptic neuron (cell receiving the signal)
What are the specialized neuronal parts?
Dendrites, soma/cell body, axon, presynaptic terminals
Motor neuron (efferent)
Has its soma in the spinal cord and receives excitation from other neurons and conducts impulses along its axon to a muscle.
Sensory Neuron (afferent)
Is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound).
Interneurons (intrinsice neurons)
Are those whose dendrites and axons are completely contained within a single strucutre. (most within the brain)
Glia cells
Aid and modulate neurons’ activities, approximately 1-5 trillion, and have five major types
Astrocytes
Star shaped, most abundant type of glia, involved in the Blood Brain Barrier (BBB), absorb excess neurotransmitter and release NT, provides nutrients to neurons (glucose, lactate), ionic balance, repair injury (form scar tissue), and in develop they help neurons migrate (radial glia)
Brain Protection?
Brain and spinal cord are the most protected organs in the body. There is physical (skull, membranes, ventricles) and chemical (BBB) protection.
Blood Brain Barrier (BBB)
Involves the selective nature of brain capillaries, small molecules like O2 and CO2 pass with ease, and big molecules have to be fat soluble or have a transporter.
The cellular basis of the BBB
There are tight junctions of blood vessel epithelial cells. There are astrocyte endfeet (endfoot processes). Both of these prevent leaks of cells of molecules from the blood into the brain.
Ependymal cells
Epithelium-like lining of the ventricular system, have cilia which circulate Cerebral Spinal Fluid (CSF) around the CNS, covered with microvilli which absorb CSF, choroid plexus
choroid plexus
a population of modified ependymal cells and capillaries to make CSF
Microglia
Immune defense (macrophage) and scavenge dead neurons, plaques, and pathogens. They eat problematic cells and monitor environment.
Oligodendrocytes
They provide support and insulate the axons through myelination.
Schwann Cells
Myelinate peripheral nervous system neurons
What is the difference between Oligodendrocytes and schwann cells?
One oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1 micron of myelin sheath around each axon. Schwann cells can wrap around only 1 axon.
What does proper neuronal function depend on?
Neurons and glia cells
What are examples of organelles?
nucleus, mitochondria, microtubules, neurofilaments, lysosomes, endoplasmic reticulum (smooth and rough), golgi apparatus, and plasma membrane
Nucleus
stores DNA which is transcribed (through transcription) to RNA then translated (through translation) to a protein
Mitochondria
cellular power plants, consume oxygen and glucose to make ATP, stores and releases Ca++, has its own separate DNA, and has other roles (including membrane potential maintenance, signaling, cellular differentiation, cell death, controls cell cycle and cell growth)
Microtubule
Polymers of a protein called tubulin, involved in maintaining structure of the cell, make up the internal structure of cilia and flagella, cell division (mitosis and meiosis), and provide platforms for intracellular transport (movement of secretory vesicles, organelles, intracellular substances
Neurofilaments
They are the major component of the neural cytoskeleton. They provide structural support for the axon and to regulate axon diameter.
Lysosomes
cell’s waste disposal system, autophagy, and repair the plasma membrane
Endoplasmic Reticulum (ER)
interconnected network of flattened, membrane enclosed sacs. Made of smooth and rough ER
Smooth ER
Lipid metabolism (membrane formation), metabolism of carbohydrates, drug detoxification, attachment of receptors on cell membrane proteins, steroid metabolism, Ca++ storage and release
Rough ER
Protein synthesis at ribosomes and synthesize (lysosomes enzymes, secreted proteins, membrane bound proteins)
golgi apparatus
packages proteins inside the cell before they are sent to their destination. They are important in the processing of proteins for secretion.
What affects what crosses a plasma membrane?
Size and charge affect the rate of diffusion across a membrane.
How do neurons store energy?
In the form of an electrochemical gradient. (which allows neurons to send and receive signals)
Resting Membrane potential
The imbalance in both concentration of ions and the sum of charges of compounds inside versus outside the neuron. At rest, the membrane maintains an electrical polarization (diff in electrical charge between two locations). The inside of the membrane is slightly negative with respect to the outside (-70mV). The resting potential refers to the state of the neuron prior to the sending of a nerve impulse.
What forces work to maintain the resting potential?
Diffusion (selective permeability), concentration gradient (certain ions are more conc. either inside or outside the cell), electrostatic force (charge difference), and Na/K pump
Selective permeability
Allows some chemicals to pass more freely than other molecules pass. It is due to the opening and closing of ina channels. The membrane is selectively permeable.
Chemical Gradients
Chemicals separate as far from one another as possible. Selective permeability of the membrane leads to the build up of ions either outside or inside the cell. This creates a chemical force to push chemicals DOWN a concentration gradient.
Electrical Driving Force
Opposite charges attract, while the same charges repel. A buildup of charged chemicals (ions) can lead to electrical force.
Sodium Potassium Exchange pump
The Na/K pump pumps 3 Na out of the cell and lets in two K ions. The pump needs ATP to work. This pump maintains the resting membrane potential.
What is necessary for neurons to be able to send the electrical signal down the axon?
The resting membrane potential
Synapse
Junctions where Neurons communicate by transmitting chemicals.
Charles Scott Sherrington
In 1906, he coined the term synapse to describe the specialized gap that existed between neurons. Our teacher said he was one of the fathers of neuroscience.
How do neurotransmitters work?
They bind to receptors, causing changes in ionic concentration in the post synaptic cell.
Receptor receiving neurotransmitter?
The receptors are proteins in the synapse/body of neurons that bind neurotransmitters. They can alter ion channels or even pass ions through the membrane. The can be presynaptic OR postsynaptic.
Two kinds of synapses
excitatory and inhibitory
Excitatory synapse
When opened, an ion channel opens and changes the charge (more +) inside the post synaptic neuron. This increases the change of an action potential. It is usually to the body or dendrite of a neuron. Creates DEPOLARIZATION and is known as the Excitatory Postsynaptic Potential (EPSP).
Inhibitory synapse
When opened, an ion channel opens and changes the charge (more -) inside the postsynaptic neuron. This decreases the change of an action potential. Often located on the cell body or also at terminals that are synapsing with other neurons. Creates HYPERPOLARIZATION and is known as the Inhibitory Postsynaptic Potential (IPSP).
Integration of EPSP and IPSP
They control whether a neuron will respond to the signals. The response could be an action potential.
When does an action potential occur?
An action potential occurs when a threshold voltage is reached The threshold voltage varies from neuron to neuron.
Two types of summation
Spatial and temporal
Spatial summation
multiple signals must be near the same site to help each other alter membrane potential
Temporal summation
The signals must occur within a specific time period to help each other affect membrane potential.