Week 1 Flashcards
The main class cells in the nervous system
-Neurons: basic signaling units that transmit information throughout the nervous system
- Glial cells: serve various functions in the nervous system, providing structural support and electrical
insulation to neurons and modulating neuronal activity
CNS 3 types of glial cells
-Astrocytes: Large with round or radially symmetrical forms. They surround neurons and are in close contact
with the brain’s vasculature.
The astrocytes create the blood-brain barrier (BBB) between the tissues of the CNS and the blood
-Microglial cells: These cells are very small and irregularly shaped. They are phagocytes that remove damaged cells. They can proliferate (multiply) even in adults, unlike many cells in the CNS.
-Oligodendrocytes: These glial cells form myelin, a fatty substance in the CNS (Schwann cells in the PNS). They create myelin by wrapping their cell membranes around the axon during development
and maturation.
The blood-brain-area (BBB)
restricts the diffusion of bacteria and hydrophilic molecules in the blood from entering the neural tissue, but allows the diffusion of oxygen, carbon monoxide
and hormones.
protects the CNS from blood-borne agents(pathogenes/chemical
compounds)
Myelin
A good electrical insulator, preventing loss of electrical current across the cell membrane, and thus increases the speed and distance the information can travel along a neuron.
What are neurons
A neuron consists of the standard components found in almost all cells. They have a cell membrane called a soma that encases the cell body.
The neuron itself sits in cytoplasm, a bath
of salty extracellular fluid, which is made up out of a mixture of ions (positive or negative electrical charge; potassium, sodium, chloride and calcium).
Includes Dentrites and Axons
What are Dentrites?
Branching extensions of the neuron that receive inputs from other neurons. Dendrites have specialized processes
called spines, where the input of other neurons is received.
What are Axons?
A single process that extends from the cell body, the output side of the neuron. Electrical signals travel along the axon to the axon terminal (end of the axon), where a signal is transmitted to
other neurons/targets. The synapse is where the transmission occurs, a structure where two neurons come into close contact to that chemical or electrical signals can be passed from one cell to the next. Axons are wrapped in layers of myelin, in which the gaps of myelin are called nodes of Ranvier.
Axon collaterals
Axon branches that transmit signals to more than one cell.
Neuronal Signaling
neurons receiving, evaluating and transmitting information
Within vs Between neuronal signaling
Within Signaling
Information moves from input synapses to output synapses through changes in the electrical state of the neuron (caused by the flow of electrical currents).
Between Signaling
Information transfer across synapses is typically mediated chemically by neurotransmitters
(chemical synapses). Also electrical synapses exist in which signals travel via transsynaptic electrical currents.
The Membrane Potential
-Electrical potentials across the neuronal membrane caused by enegry.
-The difference between the voltage inside the neuron versus outside the neuron
-These two voltages depend on the concentrations of potassium, sodium and chloride ions, as well as on the charged protein molecules both inside and outside the cell
-Resting state of the neuron is negatively charged at -70mV (resting membrane potential) more negatively charged inside than outside.
Ion channels
proteins with a pore through the center, and they allow certain ions to flow down their electrochemical and concentration gradients
Permissibility
the extent to which a particular ion can cross the membrane through a
particular ion channel
Selective Permeability
A property that enables cells to maintain internal chemical stability
Gate ion channels
membrane permeability can change, these neurons are excitable
Non Gated ion channels
unregulated and always allow the associated ion to pass through
Ion pumps (active transport proteins)
use energy to actively transport ions across the membrane against their concentration gradients (from low concentration to high concentration regions)
Action Potential
A rapid depolarization (-55mV) and repolarization of a small region of the membrane. Enables signals to travel for meters with no loss in signal strength, because they continually regenerate the signal at each patch of membrane on the axon.The process begins when synapses on a neuron’s dendrites receive a signal, resulting in the opening of ion channels in the dendrite, which causes the ionic currents to flow. It can regenerate itself by voltage-gated ion channels
Hodgkin-Huxley cycle
Lasts 1ms. The depolarized membrane (-55mV) is the potential value for the threshold for initiating an action potential.
When the threshold is reached the voltage-gated Na+ channels open and the ions flow rapidly into the neuron. This influx of positive ions further depolarizes the neuron, continuing the cycle by causing even more Na+ channels to open
Nuerotransmitter classification?
Amino acids: gamma-aminobutyric acid (GABA), glutamate, and glycine.
biogenic amines: dopamine, norepinephrine, and epinephrine
(these three are known as the catecholamines), serotonin and histamine
Achetylochlorin (Ach) is a neurotransmitter with its own biochemical class
-neuropeptites?
Neuropeptides
slightly larger molecules which are made up of strings of amino acids
- Tachykinins
- Neurohypophyseal hormones
- Hypothalamatic releasing hormones
- Opioid peptides
- Other neuropeptides
Functional Classification of Neurotransmitters
- Excitatory effect: ACh, the catecholamines, glutamate, histamine, serotonin, and some of the
neuropeptides. - Inhibitory effect: GABA, glycine, and some of the neuropeptides.
- Conditional neurotransmitters: act only in concert with other factors, action is conditioned on the presence of another transmitter in the synaptic cleft or activity in the neural circuit.
What is released by the pyramidal cells of the cortex, the most common cortical
neurons and thus the most prevalent neurotransmitter found in fast excitatory synapses in the brain/spinal cord. Different types of receptors bind to it (change in strength). Too much excitation is seen in stroke, epilepsy and neurodegenerative diseases and is associated with toxicity and cell death?
Glutamate (excitatory)
