Synapses & Neural Integration pt 1

Question 1

what are synapses

Answer 1

how neurons communicate with other neurons or with effector organs

Question 2

what are the types of synapses

Answer 2

electrical and chemical

Question 3

how are electrical signals transmitted in electrical synapses, chemical synapses?

Answer 3

through gap junctions; thru neurotransmitter

Question 4

what are the cells involved in electrical synapses

Answer 4

neuron to neuron; neuron to glial cell

Question 5

where are electrical synapses found in the body

Answer 5

retina, brain: cortex, brainstem, hypothalamus, smooth and cardiac muscle, between neuroglial cells

Question 6

what is the speed of communication for electrical synapses, is it uni or bidirectional

Answer 6

faster; mainly bidirectional

Question 7

what is the type of communication for an electrical synapse

Answer 7

excitatory or inhibitory at same synapse due to bidirectionality of gap junction

Question 8

what are the cells involved in chemical synapses

Answer 8

neuron to neuron or neuron to effector (e.g. muscle)

Question 9

what is the speed of communication in chemical synapses, is it uni or bidirectional

Answer 9

slower but fast overall; always unidirectional

Question 10

what is the type of communication for chemical synapses

Answer 10

excitatory or inhibitory since unidirectional

Question 11

where are chemical synapses found in the body

Answer 11

almost everywhere (muscles, glands, tastebuds)

Question 12

what are gap junctions, what are they made from

Answer 12

areas made of connexin proteins that join cells for a passageway for ions and molecules (connect with gap junctions of another cell)

Question 13

what neural structures do chemical synapses involve

Answer 13

axons, dendrites, soma

Question 14

what is a presynaptic neuron

Answer 14

one that sends a signal

Question 15

what is a post synaptic neuron

Answer 15

one that receives a signal

Question 16

describe a axosomatic synapse

Answer 16

axon on soma

Question 17

describe a axoaxonic synapse

Answer 17

axon to axon

Question 18

describe a axodendritic synapse

Answer 18

axon to dendrite

Question 19

what is another name for an axon terminal

Answer 19

terminal/synapse bouton

Question 20

describe the synaptic cleft

Answer 20

a small space between cells that makes a synapse

Question 21

what is a neurotransmitter; where can it be found

Answer 21

a chemical that is released from the axon’s terminal boutons this happens in most synapses; vesicles have NTs

Question 22

how are presynaptic and postsynaptic cells held close together

Answer 22

thru cell adhesion molecules (CAMs)

Question 23

label a chemical synapse

Answer 23

….

Question 24

label the anatomy of a synapse

Answer 24

….

Question 25

describe chemical synaptic communication

Answer 25

- action potential depolarizes axon terminal and voltage-gated Ca+2 channels open - Ca flows down electrochemical gradient into terminal of bouton - synaptic vesicles fuse - neurotransmitter is released to the post synaptic side - response in postsynaptic neuron - neurotransmitter binding is temporary for response until action potentials finish, the NT needs to be cleared thru: enzyme degradation, reuptake/recycle, whole diffusion

Question 26

how much neurotransmitter is released and what does it depend on

Answer 26

based on concentration of calcium in axon terminal which depends on frequency of action potentials in presynaptic neuron

Question 27

what happens if second (or many) action potentials arrive before neurotransmitter clears

Answer 27

action potentials keep bringing in calcium, you won't have enough time for the neurotransmitter clearing which will keep creating a response

Question 28

what is synaptic delay

Answer 28

time between arrival of an action potential and response in postsynaptic cell

Question 29

what is synaptic delay caused by

Answer 29

changes in calcium ion entry, vesicle docking, release of neurotransmitter

Question 30

describe post synaptic potential

Answer 30

change in membrane potential in response to receptor-neurotransmitter binding (graded potential)

Question 31

what happens to the neurotransmitter after it diffuses across the synapse

Answer 31

binds to a specific receptor protein on the postsynaptic membrane; then NT is called ligand which results in opening of chemically regulated ion channels (aka ligand gates)

Question 32

what is EPSP; what is the most common neurotransmitter

Answer 32

excitatory postsynaptic potential; graded depolarization from opening of Na+ or Ca+2 channels; glutamate

Question 33

what is ipsp; what is the most common neurotransmitter

Answer 33

inhibitory postsynaptic potential; graded hyperpolarization from opening of K+ or Cl- channels; GABA

Question 34

summarize excitatory NT action

Answer 34

presynaptic neuron: ap made by axon; ca+ voltage gated channels open; excitatory NT releases postsynaptic neuron: densdrites and cell bodies open ligand gated channels; inward diffusion of na+ causes epsp; localized, decremental conduction of epsp; axon intiial segment opens voltage gated na+ and then k+ channels; axon conducts action potential

Question 35

how do responses in post-synaptic cell occur

Answer 35

thru signal transduction pathways

Question 36

what are the 2 types of signal transduction pathways; are they fast or slow

Answer 36

-channel-linked receptors (ionotropic receptors) are fast -g-protein coupled receptors (metabotropic receptors) are slow

Question 37

describe channel-linked receptors (ionotropic receptors)

Answer 37

NT binds and ions can move bidirectionally but not simultaneously

Question 38

describe direct coupling of g-protein coupled receptors (metabotropic receptors)

Answer 38

NT binds to receptor; G protein activates which opens or closes ion channel

Question 39

describe g-protein coupled receptors via second messenger

Answer 39

NT (first messenger) binds to receptor; G protein activates which activates or inhibits enzyme; a second messenger is produced; 2nd mes. opens/closes ion channels or produces other cell responses (slower acting process)

Question 40

describe the main difference between excitatory and inhibitory synapses

Answer 40

excitatory more likely to produce an action potential (Vm closer to threshold) whereas inhibitory decreases chance of making action potential (Vm away from threshold)