Chapter 3 Flashcards
Communication between neurons is PRIMARILY ________
chemical
Specialized gap between neurons
synapse
Discovered narrow gap between neurons
Ramon y Cajal
Demonstrated that communication between one neuron & the nxt differs from communication along single axon
Charles Scott Sherrington
Automatic muscular responses to stimuli
Reflexes
Circut from sensory neuron to muscle response
Reflex Arc
Repeating stimuli w/in a brief time have a cumulative effect
Temporal summation
the cell that RECEIVES a msg
Postsynaptic Neuron
Cell that DELIVERS the transmission
Pre-Synaptic Neuron
Graded depolarization; occurs when sodium ions enter the cell; that decays over time & space; Discovered by Eccles
Excitatory Postsynaptic Potential (EPSP)
Synaptic inputs from various locations combine their effects of a neuron.
Spatial Summation
How did Sherrington discover this?
Pinch a dog’s foot; one time=nothing; but several pinches did
Ordinarily Occur together…
Temporal summation & spatial summation
Hyperpolarizes
increases the negative charge w/in the cell, moving it further from the threshold & decreasing the probability of an action potential
Occurs when the synaptic input selectively opens the channel for potassium ions to leave the cell or for chloride ions to enter the cell
Inhibitory Postsynaptic Potential (IPSP)
The importance of Sherrington’s work
led to researcher’s being able to show how nervous system was wired & make a diagram
Peridoic reproduction of action potentials even w/out synaptic input
spontaneous firing rate
1st to suggest that synapses operated by using chemicals (adrenaline) as means of transmitting signals (British)
T.R. Elliot
Won the Nobel Prize for his work w/chemical synapses; 1st to convincingly demonstrate that communicate across the synapse occurs via chemical means (German)
Otto Loewi
Chemicals released by one neuron that affect a second neuron
Neurotransmitter
Acids containing an amine group (NH2)
Amnio Acids
Chains of amino acids
Neuropeptides
Chemical similar to amino acid, except that NH2 group has been replaced by N(CH3) group (one member “family”)
Acetylcholine
Neurotransmitters containing one amine group (NH2), formed by a metabolic changed in certain amino acids
Monoamines
Chemical category that includes adenosine & several of its derivatives
Purines
Nitric Oxide & possibly others
Gases
epinephrine, norepinephrine (adrenaline), dopamine
catecholamines
tiny packets that store high concentrations of neurotransmitters
Vesicles
A chemical that breaks down excess lvls of some neurotransmitters
MAO (monoamine oxidase)
Release of neurotransmitter in bursts from presynaptic terminal into synaptic cleft
exocytosis
Why does a neuron release a combo of neurotransmitters instead of just one?
the combo makes the neuron’s msg more complex, such as brief excitation followed by slight but prolonged inhibition.
Occur at one type of receptor; channels controlled by neurotransmitter are transmitter-gated or ligand-gated channels; begin quickly & last for very brief period of time
Ionotropic effects
Initiates a series of metabolic reactions; slower & longer lasting than inotropic effects;
Metabotropic effects
For vision & hearing, the brain needs rapid, quickly changing info, the kind that this brings
Ionotropic synapses
better suited for more enduring effects such as taste, smell & pain; also important for many aspects of arousal, attention, pleasure, & emotions (functions that arise more slowly & last longer than a visual or auditory stimulus)
Metabotropic synapses
Often described as neuromodulators- have several porperties that distinguish them from neurotransmitters
neuropeptides
chemicals that are secreted by gland or other cell & conveyed by the blood to other organs
Hormones
Glands that produce hormones
Endocrine glands
Consists of anterior pituitary & posterior pituitary
Pituitary gland
after it activates a receptor, it’s broken down by enzyme (acetylcholinesterase) into acetate & choline
Acetylcholine
In certain brain areas, presynaptic neuron takes up most of the released neurotransmitter molecules intact & reuses them
Reuptake (occurs thru transporters)
Detect the amount of neurotransmitter released & inhibit further synthesis & release after it reaches a certain lvl
autoreceptors
special purpose synapses that operate electrically
electrical synapses
contact between membrane of one neuron w/membrane of another
gap junction
