Ch. 2: Synapses

synaptic delay

reflexes are slower than conduction along an axon

synapse

specialized gap as a point of communication b/n neurons

presynaptic neuron

neuron that delivers the synaptic transmission

postsynaptic neuron

neuron that receives the message

slower

the speed of conduction through a reflex arc is _____ and more variable, sometimes 15 m/s (compared to an average of 40 m/s). the delay occurs at the synapse.

• Sherrington found a difference in the speed of conduction from previously measured action potentials

temporal summation

repeated stimuli over a short period of time

spatial summation

synaptic input from several small stimuli in a similar location

excitatory postsynaptic potential (EPSP)

graded depolarization that decays over time and space

inhibitory postsynaptic potential (IPSP)

temporary hyper-polarization of a membrane

Interneuron in the spinal cord sent an excitatory message to the flexor muscles of one leg and an inhibitory message to the other three legs

What can you conclude/interpret from this observation?

During the reflex, the leg that was pinched retracted while the other three legs were extended.

True

True or False?

Several weak stimuli present at slightly different times (temporal summation) or slightly different locations (spatial summation) produce a stronger reflex than a single stimulus.

False: As one set of muscles becomes excited, another set relaxes (EPSP vs IPSP)

True or False?

As one set of muscles becomes excited, another set becomes excited as a result (EPSP vs IPSP).

1. Synthesis of smaller neurotransmitters such as acetylcholine

2. Action potential causes calcium to enter, releasing neurotransmitter

3. Neurotransmitter binds to receptor

4. Separation from receptors

5. Re-uptake of neurotransmitter by transporter protein

   1. Reabsorbed intact by the presynaptic neuron (re-uptake) OR broken down (inactivation)

6. Postsynaptic cell releases retrograde transmitters that slow further release from presynaptic cell

7. Negative feedback sites respond to retrograde transmitter or to presynaptic cell’s own transmitter

What are the 7 steps for chemical transmission?

presynaptic terminal

most neurotransmitters are synthesized in the _______ ________ near the point of release

monoamine oxidase (MAO)

neurons that release serotonin, dopamine, or norepinephrineB contain _______ ______

• _____ breaks down these transmitters into inactive chemicals to prevent accumulation of harmful levels

• first antidepressant drugs were ____ inhibitors

exocytosis

bursts of release of neurotransmitter from the presynaptic terminal into the synaptic cleft (triggered by an action potential)

one

most neurons release and respond to more than ___ type of neurotransmitter

ionotropic effects

neurotransmitter attaches, immediately opens ion channels

metabotropic effects

neurotransmitter attaches, receptor protein bends, releasing the G protein which acts as a second messenger and reacts with other molecoles

agonist

binds to the receptor and produces an effect

antagonist

binds to the receptor, decreasing activation response to other agonist

hallucinogenic

__________ drugs chemically resemble serotonin (type 2A receptors)

agonist drug

acetylcholine

nicotine stimulates _________ receptors (nicotinic receptors)

• receptors = abundant on neurons that release dopamine

• nicotine increases dopamine release (associated w/ reward)

agonist drug

endorphins

opiates bind to the same receptors as __________

agonist drug

adenosine

caffeine binds to ________ receptors

• when _______ binds to ________ receptors it slows down the activity and you feel drowsy

• caffeine binds to the same receptors and blocks _______ from binding

amphetamine and cocaine, methylphenidate (Ritaline)

What are some stimulant drugs that block re-uptake?

amphetamine, cocaine

________ and _________ inhibit transporters for dopamine, serotonin, and norepinephrine

• decreases re-uptake and prolongs effects of the neurotransmitters

methylphenidate (Ritalin)

_________ is often prescribed for people with ADD/ADHD

• blocks re-uptake of dopamine but as a more gradual rate and ion a lower dose (typically)

gap junction

direct contact of the membrane of one neuron with the membrane of another

• especially helpful with rhythmic breathing and coordinating rapid movement

hormone

a chemical secreted by cells in one part of the body and conveyed by the blood to influence other cells

• produced by endocrine glands

• important for triggering long-lasting changes in multiple parts of the body

anterior pituitary

comprised of glandular tissue

• synthesizes 6 hormones (hypothalamus controls their release

posterior pituitary

comprised of neural tissues (extension of the hypothalamus)

• hypo produces oxytocin and vasopressin

• migrate down axons to _______ _______ which then releases these hormones into the blood