Chapter 1 Flashcards
Glia
Responsible for regulating the activity of neurons and the communication between them. In detail, they protect and buffer the central nervous system against chemical changes, provides a immune surveillance, alter the properties of neuronal signalling and nourishes the neurons.
Electric potential
Voltage difference
Membrane potential
Voltage difference between the inside and outside of the cell.
Action potential
Single membrane potential reaching threshold level to start a chain reaction of more membrane potentials
Dendrities
They receive stimuli
Axon terminals/ Terminal boutons
Specialised swellings in the end of axon branches that transmits the signal to a gland, glia muscle or another neuron
Receptors
Protein structures found in the membrane of the tissues that binds to specific chemical transmitters to activate internal mechanism of the cells.
Receptors are also cells that react to physical or chemical stimuli.
Synapses
A small region of close proximity terminal branch of an axon and another cell.
Plasticity
The ability of the brain to constantly delete or make new connections. This is the basis of developmental maturation, learning, memory recovery from injury, every functional adaptation.
Synaptic cleft
A gap of 20 nanometers between axonal bouton and dendroit
Synaptic vesicles
A small sac that caries neuro transmittors
Glutomite
Glutamatergic - CNS excitation
Aspertate
Glutomatergic - Brain and spinal chord excitation
Gamma amino butyric acid
GABAergic - CNS inhibition
Glycine
Glycinergic - Rapid inhibition in spinal chord
Acetylcholine
Cholinergic - muscle activation, attention
Dopomine
Dopaminergic - reward, movement
Nor-adrenaline/ nor-epinephrine
Nor-adrenergic - arousal, smooth muscle control
serotonin
Seratonergic - relaxation, mood, sensory processing
Substance P
Peptidergic - Pain signalling, other functions
Neuropeptide Y
Peptidergic - Appetite control
Opiods
Peptidergic - Pain modulation, satiety
Adenosine tri-phosphate (ATP)
Purinergic - Many functons
What is the length range of axons?
They can be very short or be half the body length of the animal.
What is the size of the cell bodies?
The cell bodies size varies from 10 micrometers to 50 micrometers. Hair is 100 micrometers in width.
What is the basis of most connections within the nervous system?
The firing of action potentials and transmitting through neurotransmitter.
How is an action potential formed?
When the receptors in the dendrites are stimulated, they open ion channels to let the flow of + and - ions across the membrane. The addition of all charge differences inside the membrane has to be higher than a certain level(threshold level) for an action potential to be initiated. If the action potential is initiated, there will be rapid change in membrane potential across the cell, which travels towards the axon terminals.
How are neurotransmitters released?
As the action potential reaches the terminal branches, they activate the release of calcium ions. These calcium ions in turn activate cellular machinery which release small bags of neurotransmitters. These bags or sacs are called vesicles. The vesicles reaches the membrane where the sac breaks and the neurotransmitter is diffused in to the synapse.
How does the neurotransmitter work?
The neurotransmitter diffuses across the 20 nanometer synaptic cleft and binds with protein structures called receptors. The receptors are found on glands, muscles, glia and other neurons. This can cause a wide variety of effect on the the postsynaptic cell.
What are ionotropic receptors?
Ionotropic receptors are receptors that open ion channels to cause change in the charges of the membrane to either initiate or inhibit an action potential.
What are metabotropic receptors?
Metabotropic receptors are receptors that activate cellular machinery to alter the ion channels, to activate gene expression or cause changes in the structure of the neuron.
What are excitatory and inhibitory neurotransmitters?
They are the ones that bind to ionotropic receptors to open ion channels for the initiation or inhibition of action potentials. Excitatory(glutamate and aspartate) transmitters open sodium ion channels causing depolarisation of the cell(positive charge). This promotes the firing of an action potential. Inhibitory(GABA and glycine) transmitters on the other hand, open chloride channels which polarise the cell, inhibiting the firing of an action potential.
What are the different ways neuronal firing is affected?
Action potential-neurotransmitters Gap junction Hormones Composition of extra cellular fluid Feedback from dendrites Activity of nearby glia Distance of the synapse from the axon hillock
How many neurons are there in the brain?
86 billion neurons in human brain. 6 billion in the rhesus monkey and 200 million in the rat brain.
What are gap junctions?
Gap junctions are small opening in the cell membranes that allows neurons to connect to each other. This allows membrane potentials and ions to move across neurons without a physical barrier. In the cortex, inhibitory neurons are often gap-junction coupled.
What are the functions of astrocytes?
Cellular environment Tending synapses Metabolic regulation Signalling and communication Governing capillary flow Providing neurons with preprocessed food
What is gene expression?
Gene expression is the process by which gene blueprints are used to make certain non DNA products, mostly proteins. This can be detected by a number of tests like in situ hybridization.
Is there a clear distinction between-
A) neurons and glia
B) ionotropic and metabotropic receptors
A) No, neurons and glia have some functions that are really similar, blurring the line of distinction.
B) No, ionotropic and metabotropic receptor functions also overlap. Some ionotropic receptors can open calcium channels that can cellular machinery to be activated. Some metabotropic receptors opens ion channels by activating secondary messengers.
How many glial cells are there?
Originally, it was thought to be 10 times more than neurons, but now it is estimated to be around the same number of neurons.
What are ependymal cells?
Ependymal cells are cells that line the ventricles in the brain. They form specialised structures with blood vessels called choroid plexus. This cluster secretes CSF. Some of these ependymal cells have the ability to divide and form new cells and constantly replace old cells in the olfactory bulb and the dentate gyrus of the hippocampus.
