Chapter 2 - Quiz 1 Flashcards
2,1 The concept of the Synapse
What did Charles Sherrington discover in 1906? Define it. (2)
-synapses
-a specialized gap as a point of communication between two neurons
2.1 -1 Properties of Synapses
Define reflexes. Define reflex arc. (2)
-automatic muscular responses to stimuli
-a circuit from sensory neuron to muscle response
2.1 -1 Properties of Synapses
Why was Sherrington curious about neurons? How did Sherrington discover synapses? (2)
-the prevailing belief before was that nerve impulses travelled continuously along nerve fibers, but these couldn’t t explain the delay between stimuli and response like a reflex
-tested reflexes in a dog who was strapped into a harness above the ground by pinching its foot. Here he noticed a delay and wanted to know why.
2.1 -1 Properties of Synapses
What three properties did Sherrington find that suggest a junction exists between neurons? (3)
-reflexes are slower than action potentials along a single axon
-several weak stimuli presented at nearby places or times produce a stronger reflex than one stimulus alone does
-when one set of muscles becomes excited a different set becomes relaxed
2.1 -1b Temporal Summation
What did Sherrington refer to as temporal summation? Why does it happen and what does it lead to? What is its purpose? (4)
-Combining signals that arrive at a neuron in a short time.
-Happens when a neuron gets signals in rapid succession from the same source.
-Leads to a stronger or longer response from the receiving neuron.
-Helps the brain process information quickly.
2.1 -1b Temporal Summation
What is an example of temporal summation? Describe what the temporal summation does for the person. Why is it useful? (4)
-You accidentally touch a hot stove with your hand causing pain receptors in the skin to send signals to the brain to alert about the danger.
-this causes rapid signals
-The combined effect of these signals results in a stronger and prolonged perception of pain.
-this prompts you to quickly withdraw your hand to prevent further injury.
2.1 -1b Temporal Summation
What is a graded depolarization known as? Which gates open in the cell? If the depolarization does not cause the cell to reach its threshold, what happens? (3)
-excitatory postsynaptic potential (EPSP)
-sodium gates open
-the depolarization decays quickly
2.1 -1b Temporal Summation
What are the two types of electrical signals in neurons?
-action potentials and graded potentials
2.1 -1b Temporal Summation
What two options can graded potentials be?
-excitatory/depolarizing or inhibitory/hyperpolarizing
2.1 -1b Temporal Summation
What are the characteristics of action potentials? (3)
-always of the same magnitude and duration
-involve rapid depolarization followed by repolarization and often hyperpolarization
-propagate over long distances without losing strength
2.1 -1b Temporal Summation
Describe the function of the action potential (2)
-used for long-distance communication
-transmit info from one part of neuron to another and from one neuron to another
2.1 -1b Temporal Summation
What are the characteristics of a graded potential? (3)
-magnitude and duration depend on the strength and duration of the stimulus
-do not propagate over long distances and tend to weaken over time and space
-can be either depolarizing (excitatory) or hyperpolarizing (inhibitory)
2.1 -1b Temporal Summation
What are the functions of graded potentials? (3)
-serve as short-distance signals, primarily occurring in the dendrites and cell body of neurons
-sums up inputs from multiple sources
-can summate spatially (across different synapses) and temporally (over time) to influence the generation of action potentials
2.1 -1c Spatial Summation
What did Sherrington also discover when he would pinch two points in different areas simultaneously? What concept did this showcase? (2)
-neither pinch alone produced a reflex but together they did
-concept of spatial summation
2.1 -1c Spatial Summation
Do temporal summation and spatial summation work together or independently?
-Temporal and spatial summation often work together. Imagine waves hitting different parts of the shore at different times and strengths.
2.1 -1d Inhibitory Synapses
Describe the experiment in which Sherington discovered inhibitory responses?
-Sherrington’s idea: Pinching the foot sends a message to a spinal cord neuron. This neuron excites muscles in the pinched leg and the other legs’ opposite muscles, while also calming muscles in the pinched leg and the other legs.
2.1 -1d Inhibitory Synapses
What is the temporary hyperpolarization of a membrane called? What does it cause to happen in the cell? (2)
-inhibitory postsynaptic potential (IPSP)
-synaptic input selectively opens the gates for potassium ions to leave the cell or for chloride ions to enter the cell
-IPSP makes the cell’s charge more negative temporarily, lowering the chance of an action potential.
2.1 -1d Inhibitory Synapse
Can an inhibitory message flow along an axon? Why or why not? (2)
-no
-No, inhibitory messages cannot flow along an axon. Axons transmit signals away from the cell body. Inhibitory messages are conveyed across synapses and make it less likely for an action potential to occur in the postsynaptic neuron
2.1 -2 Relationship among EPSP, IPSP and Action potentials
What is a spontaneous firing rate? What increases it and what decreases it? (2)
-a periodic production of action potentials even without synaptic input
-EPSP increase this and IPSP decrease it
-reflects the baseline level of activity of a neuron in the absence of external stimulation
-a neurons spontaneous firing rate could be 10 action potentials per second
2.2 -1 The Discovery of Chemical Transmission at Synapses
What was Loewi’s evidence that neurotransmission depends on the release of chemicals?
-he stimulated nerves to alter heart rates in frogs, collected fluid from around the hearts affected by these stimuli, transferred this fluid to other frogs’ hearts, and observed corresponding changes in heart rate, demonstrating that nerve stimulation released chemicals that could influence heart function.
2.2 -2 The Sequence of Chemical Events at a Synapse
Describe the steps of chemical events at a synapse (7)
-neuron makes neurotransmitters (small chemicals are made in axon terminal and neuropeptides in the cell body)
-action potential travels down the axon enabling calcium to enter the cell at the presynaptic terminal
-calcium releases neurotransmitters from terminals and into the synaptic cleft
-these neurotransmitters diffuse across the space, attach to receptors and change the activity of the postsynaptic neuron
-NT separate from their receptors
-NT may be taken back into presynaptic neuron for recycling or diffuse away
-some postsynaptic cells send reverse messages to control further release of NT by presynaptic cells
2.2 -2a Types of Neurotransmitters
What are the 6 groups of NT?
-amino acids, A modified amino acids, monoamines, neuropeptides, purines, gases
2.2 -2a Types of Neurotransmitters
What is the oddest NT? What does it do? (2)
-nitric oxide
-increases blood flow to area
-also isn’t stored in a vessicle
2.2 -2b Synthesis of Transmitters
What are catecholamines? Which NT? (2)
-contain a catechol group and an amine group
-epinephrine, norepinephrine, dopamine
2.2 -2c Storage of Transmitters
What is MAO? What is its purpose? (2)
-enzyme that converts catecholamines and serotonin into synaptically inactive chemicals called MAOIs
-breaks these NT into inactive forms, preventing their accumulation into harmful amounts
2.2 -2d Release and Diffusion of Transmitters
Does an action potential itself release the NT at the end of an axon?
-no, depolarization opens voltage-dependent calcium gates in presynaptic terminal which causes exocytosis
-exocytosis is a release of neurotransmitters from the presynaptic neuron into the synaptic cleft
2.2 -2e Activating Receptors of the Postsynaptic cell
What are the two effects that can happen when a NT attaches to its receptor? (2)
-receptor may open a channel (ionotropic effect)
-receptor may produce a slower but longer effect (metabotropic effect)
2.2 -2f Ionotropic Effects
What is an ionotropic effect?
-on/off switch where input either produces excitation or inhibition
-synaptic effects that depend on the rapid opening of some kind of gate in the membrane
-like a bag that twists open
2.2 -2f Ionotropic Effects
The channels controlled by a NT (Ionotropic), as compared to the voltage-gated channels sodium and potassium channels are what? Define this term. (2)
-transmitter-gated or ligand-gated
Transmitter-gated/ligand-gated: ion channel that opens temporarily when a neurotransmitter binds to it
2.2 -2f Ionotropic Effects
Which NT do most ionotropic effects depend on for excitatory and inhibitory ionotropic synapses?
-glutamate (excitatory) or GABA (inhibitory)
-glycine as inhibitory and acetylcholine as excitatory as well
2.2 -2g Metabotropic Effects and Second Messenger Systems
Define metabotropic effects. Which NT do they use? (2)
-a sequence of metabolic reactions that produce slow and long-lasting effects at a synapse
-many including dopamine, norepinephrine, and serotonin (sometimes glutamate and GABA too)
2.2 -2g Metabotropic Effects and Second Messenger Systems
What is a G protein?
-protein coupled with guanosine triphosphate (GTP)
2.2 -2g Metabotropic Effects and Second Messenger Systems
What is the result of the metabotropic effect which bends the receptor protein detacthing the G protein?
-the G protein takes its energy elsewhere in the cell and results in an increased concentration of a second messenger
2.2 -2g Metabotropic Effects and Second Messenger Systems
What is the first and second messenger? (2)
-first messenger is signaling molecule like NT
-second messenger relays the signal of the first messenger and communicates to areas within the cell
-the ability of metabotropic synapses to influence much or all activity of the cell over a longer period of time seperates this synapse from ionotropic
2.2 -2g Metabotropic Effects and Second Messenger Systems
Which behaviors or perceptions are ionotropic and metabotropic effects responsible for? (2)
-ionotropic is responsible for vision and hearing where the brain needs quick info
-metabotropic is responsible for taste, smell and pain as these are more enduring effects
2.2 -2h Neuropeptides
What do researchers often refer to neuropeptides as? Why? (2)
-neuromodulators
-because they have properties that set them apart from other transmitters
2.2 -2h Neuropeptides
What are the differences between NT and neuropeptides? Start with neuropeptides. Synthesized? Released from and by? Effects what and where and for how long? (6)
-synthesized in cell body
-released mostly from dendrites and sometimes cell body
-released by repeated depolarization
-effects neighboring cells by causing them to release neuropeptides too
-diffuses to wide area
-duration is minutes
2.2 -2h Neuropeptides
What are the differences between NT and neuropeptides? DO NT. Synthesized? Released from and by? Effects what and where and for how long?
-synthesized in presynaptic terminal
-released in axon terminal
-released by single action potential
-has no effect on neighbors
-the effect spreads mostly to receptors on the postsynaptic cell
-takes milliseconds to seconds
2.2 -2j Drugs that Act by Binding to Receptors
Define hallucinogenic drugs. Give an example
-drugs that distort perception
-LSD chemically resembles serotonin
2.2 -2j Drugs that Act by Binding to Receptors
How does nicotine work with NT?
-stimulates a family of acetylcholine receptors known as nicotinic receptors, which are abundant on neurons that release dopamine
2.2 -2j Drugs that Act by Binding to Receptors
What do opiate drugs mimic?
-they bind to receptors for endorphins and relieve pain
2.2 -2k Inactivation and Reuptake of Neurotransmitters
Are neuropeptides inactivated?
-no, they diffuse away
2.2 -2k Inactivation and Reuptake of Neurotransmitters
After acetylcholine activates a receptor, which enzyme breaks it down
-acetylcholinesterase breaks it into two fragments, acetate and choline
-it then recycles it, but this takes time
2.2 -2k Inactivation and Reuptake of Neurotransmitters
Why might a transmission be slowed after a rapid series of action potentials?
-since the presynaptic neuron does not reabsorb every molecule it makes, the NT would be depleted
2.2 -2k Inactivation and Reuptake of Neurotransmitters
What happens to serotonin and catecholamine molecules after they stimulate a postsynaptic receptor? Define reuptake. Define COMT. (3)
-they do not break down at postsynaptic membrane and are either reuptake or broken down by an enzyme called COMT
-Reuptake: reabsorption of a NT at the presynaptic terminal through transporter proteins
-COMT: enzyme that breaks down excess dopamine
2.2 -2k Inactivation and Reuptake of Neurotransmitters
What are transporters?
-special membrane proteins that reuptake NT
2.2 -2k Inactivation and Reuptake of Neurotransmitters
How do amphetamine and cocaine influence synapses?
-They block reuptake of released dopamine, serotonin, and norepinephrine.
2.2 -2k Inactivation and Reuptake of Neurotransmitters
What is methylphenidate?
-ritalin for ADHD
-similar properties for cocaine
2.2 -2I Negative Feedback from the Postsynaptic Cell
What are autoreceptors? What do they provide? (2)
-receptors on a presynaptic neuron that respond to NT by inhibiting further making and releasing of it
-they provide negative feedback
2.2 -2I Negative Feedback from the Postsynaptic Cell
What is a way that postsynaptic neurons provide negative feedback? What are examples of reverse transmitters? (2)
-they release chemicals that travel back to presynaptic terminal and inhibit further release of NT
-examples include nitric oxide, hydrogen ions, anandamide and 2-AG
2.2 -2I Negative Feedback from the Postsynaptic Cell
What do cannabinoids bind to? (2)
-anandamide or 2-AG receptors on presynaptic neurons telling it that the cell got its message so stop sending it
-decreasing action potentials in general
2.2 -2m Electrical Synapses
What is a gap junction?
-when at an electrical synapse the membrane of one neuron comes into direct contact with the membrane of another neuron
2.2 -2m Electrical Synapses
How does electrical synapse work? (3)
-fairly large pores of the membrane of one neuron line up with other pores in membrane
-these pores are large enough that sodium and other ions pass freely (they remain open constantly)
-the two neurons essentially act as one
2.2 -3 Hormones
Define a hormone
-chemical secreted by cells in one part of the body and carried by the blood to influence other cells
2.2 -3 Hormones
What is the difference between a NT and a hormone and a neuropeptide? (3)
-NT is like a telephone signal, it conveys a message from the sender to the intended receiver
-hormones function more like radio station, they convey a message to any receiver tuned to the right station
-neuropeptides are intermediate
2.2 -3 Hormones
What are two important types of hormones that activate a second messenger within the cell?
-protein and peptide hormones
-proteins are longer chains of amino acids and peptides are shorter chains
-they act like a first messenger
2.2 -3 Hormones
What is the posterior pituitary gland composed of?
-neural tissue
2.2 -3 Hormones
What is the anterior pituitary gland composed of?
-glandular tissue
2.2 -3 Hormones
What brain structure produces vasopressin and oxytocin?
-the hypothalamus
2.2 -3 Hormones
Define releasing hormones
-hormone released by the hypothalamus that flows to the anterior pituitary
