Synapses and brain Flashcards
What did Camillo Golgi do and think
Camillo Golgi (1890): silver chromate salt to reveal the intricate structures of a single neuron. Thought that the nervous system was like the circulatory system, with a branching system of tubes, one unit, not multiple.
what did Santiago Ramón y Cajal think
Santiago Ramón y Cajal: (used Golgi’s method), hypothesized that the functional unit of the brain is the neuron, also known as the ‘neuron doctrine’.
why do neurons have polarity
Neurons have polarity, they go in a direction. Information is collected at one point, then transmitted to another point
what is the Soup vs Spark debat
Soup vs Spark debat:
- Soup - chemicals are used for inter neuron transmission
- Spark - electricity is used for inter neuron transmission
What did Loewi discover
Loewi’s Results
- Electrical stimulation of the vagus nerve attached to heart #1 caused heart #1 to slow don
- After a delay, heart #2 also slowed down
- Loewi hypothesized that electrical stimulation of the vagus nerve released a chemical into the fluid of chamber #1 that flowed into chamber #2
- He called this chemical “Vagusstoff”
- We now know this chemical as the neurotransmitter acetylcholine
what are neuropeptides
Several neuropeptides, relatively short chains of amino acids, also function as neurotransmitters
Neuropeptides include substance P and endorphins, which both affect our perception of pain
what do Opiates do
Opiates bind to the same receptors as endorphins and can be used as painkillers
what do gases do
Gases such as nitric oxide (NO) and carbon monoxide (CO) are local regulators in the PNS
CO/NO are not stored in cytoplasmic vesicles, but is synthesized on demand (note: inhaling CO can be deadly, the vertebrate body synthesizes small amounts of it)
what is a chemical synapse
The presynaptic neuron synthesizes and packages the neurotransmitter in synaptic vesicles located in the synaptic terminal
(most neurons only make one type of neurotransmitters, other make multiple)
The action potential causes the activation of Ca2+ channels
Ca2+ entry triggers fusion of vesicles
The neurotransmitter diffuses across the synaptic cleft and is received by the postsynaptic cell
what are PSPs
- Direct synaptic transmission involves binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell
- Neurotransmitter binding causes ion channels to open, generating a postsynaptic potentials (PSPs)
- Postsynaptic potentials fall into categories
- Excitatory postsynaptic potentials (EPSPs) are depolarizations that bring the membrane potential toward threshold
- Inhibitory postsynaptic potentials (IPSPs) are hyper-polarizations that move the membrane potential farther from threshold
how are neurotransmitters clear
- Diffusion
- enzymatic hydrolysis
- recapture of neurotransmitters by transporters
can a single neurotransmitter bind to only one receptor
- A single neurotransmitter may bind specifically to more than a dozen different receptors, triggering their activation
- A neurotransmitter can excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells expressing a different receptor
What are Ionotropic receptors and Metabotropic receptors
- Ionotropic receptors gate ion flow
- Metabotropic receptors are G-protein couples receptors
- Binding of a neurotransmitter to a metabotropic receptor activates a signal transduction pathway in the postsynaptic cell involving a second messengers (e.g. cAMP, PKC)
- Compared to ligand-gated channels, the effects of second-messenger systems have a slower onset but last longer
what are the four different types of synapse
At electrical synapses, the electrical current flows from one neuron to another through gap junctions
At chemical synapses a neurotransmitter carries information between neurons
Mixed synapses have both
Heterosynaptic interactions involved both types of axon leading into the same cell, and interact with each other
is a single EPSP enough to start an AP
Single EPSP is usually too small to trigger an action potential in a postsynaptic neuron
If two EPsPs are produced in rapid succession, an effect called temporal summation occurs. Which might be enough to start an action potential
what are EPSPs
Excitatory postsynaptic potentials (EPSPs) are depolarizations that bring the membrane potential toward threshold
Driven by excitatory receptors with equilibrium potentials close to 0 mV
what are IPSPs
Inhibitory postsynaptic potentials (IPSPs) are often hyper polarization that move the membrane potential farther from threshold
Driven by inhibitory receptors with equilibrium potentials around -60 to -90 mV
how are EPSPs and IPSPs spatially summed
In spatial summation, EPSPs produced nearly simultaneously by different synapses on same postsynaptic neuron add together
The combination of EPSPs through spatial and temporal summation can trigger an action potential
Through summation, an IPSP can counter the effect of an EPSP
The summed effect of EPSPs and IPSPs determines whether an axon hillock will reach threshold and generate and action potential
what do Glia do
Glia cells, or glia have numerous functions to nourish, support, and regulate neurons; 10 to 50x more than neurons in a given area!
Embryonic radial glia form tracks along which newly formed neurons migrate
Astrocytes induce cells lining capillaries in the CNS to form tight junctions, resulting in a blood-brain barrier (BBB) and restricting entry of most substances into the brain
what type of nervous system did the simples animals have
By the time of the Cambrian explosion more than 500 million years ago, specialized systems of neurons have appeared that enable animals to sense their environment and respond rapidly
The simples animals with nervous systems, cnidarians, have neurons arranged in nerve nets, a series of nerve cells weakly interconnected via gap junctions
what did bilaterally symmetrical animals develop
- Bilaterally symmetrical animals exhibit encephalization, the clustering of sensory organs at the front end of the body
- Relatively simple cephalized animals, such as flatworms, have a central nervous system (CNS)
- The CNS consists of a brain and longitudinal nerve cords
- The peripheral nervous system (PNS) consists of neurons carrying information in and out of the CNS
what kind of nervous system do Annelids and Arthropods have
Are segmentally arranged clusters of neurons called ganglia
have a brain, ventral nerve cord, and segmental ganglia
what type of nervous system do cephalopods have
Most advanced of invertebrates
Have a brain, and two ganglia
Distributed along whole body
Similar amount of neurons to a cat
