Lecture 2

Question 1

endocrine system

Answer 1

-endocrine cells = all glands that secret hormones
-release chemical messengers (hormones) into circulatory system and carried to target cells

Question 2

nervous system

Answer 2

-electrical signal travel in neuron
-release chemicals (neurotransmitters) into space between neuron and target cell

Question 3

neuron communication strategy

Answer 3

electrical signal releases neurotransmitters into synapse to communicate with target (postsynaptic) cell

Question 4

neurosecretory cell communication strategy

Answer 4

release neurohormones into circulation in response to electrical signals and interface between systems

Question 5

endocrine cell communication strategy

Answer 5

release hormones into circulation

Question 6

soma

Answer 6

cell body

Question 7

dendrites

Answer 7

typically receive incoming signal (result in change in membrane potential)

Question 8

axon hillock

Answer 8

-initiate action potentials
-travels along axon to axon terminals and triggers neurotransmitter release
-axon myelinated or unmyelinated

Question 9

ion channel types

Answer 9

-open under different conditions
-ligand-gated channels open when ligands (neurotransmitter) bind
-voltage-gated (VG) channels open when there is a specific change in membrane potential (open at specific stages of an action potential)

Question 10

signal transmission

Answer 10

-signal travels down the axon to the terminals to communicate with other neurons, muscles or other target cells
-the transmitting neuron is presynaptic and the receiving neuron is postsynaptic
-two types of membrane potentials: graded potentials, action potentials

Question 11

graded potentials

Answer 11

-activated by ligand-gated Na+ channel, cause changes in membrane potential
-synaptic potential
-spatially restricted response
-conduction with decrement

Question 12

electrical signals

Answer 12

-graded changes in membrane potential occur in dendrites and cell body
-are spatially and temporally summated
-if combined depolarization exceeds threshold, an action potential is generated
-spacial summation of Ca+ also prevent generation of APs

Question 13

electrical signalling

Answer 13

-when net change in membrane potential at the axon hillock reaches or exceeds threshold (suprathreshold graded potential)
-an action potential is triggered and travels down the axon (non-graded, all-or-none signal transmission)

Question 14

stages of action potentials

Answer 14

-membrane potential depolarized past threshold potential (-55mV)
-rapid depolarization until 30mV
-membrane potential repolarizes
-membrane potential undershoots resting potential
-resting potential is restored

Question 15

two voltage regulated gates:

Answer 15

1. activation gate: opens at threshold
2. inactivation gate: closes at 30mV

also VG K+ channels triggered at threshold (-55mV) but open more slowly than Na+ channels

Question 16

conduction of APs

Answer 16

-Na+ comes in
-induces local depolarization
-opens Na+ channels close by
-Na+ comes in, etc.
-Aps travel down the axon
-only in one direction (absolute refractory period)

Question 17

absolute refractory period

Answer 17

the inactivation gate of the Na ion channel closes at 30mV, and remains closed until resting potential is reistablished - impossible to generate AP at an area where an AP has just occured

Question 18

relative refractory period

Answer 18

during hyperpolarization - possible, but harder to generate AP

Question 19

myelin sheath

Answer 19

a (mostly) vertebrate feature; a highly compacted, fatty substance

Question 20

PNS

Answer 20

Schwann cells wrap axon

Question 21

CNS

Answer 21

oligodendrocytes (OLs) wrap axons

Question 22

Schwann cells/OLs

Answer 22

-produce myelin - acts as insulation, preserving electrical potential
-increases resistance, reduces capacitance - like insulation on an electrical wire

Question 23

signal transmission

Answer 23

increases speed and efficiency of electrical transmission

Question 24

nodes of ranvier

Answer 24

lots of voltage-gated Na+ channels

Question 25

saltatory conduction

Answer 25

APs jump from node to node along the axon

Question 26

graded potentials

Answer 26

-vary in magnitude -vary in duration -decay with distance -occur in dendrites and cell body -caused by opening and closing of many kinds of ion channels

Question 27

action potentials

Answer 27

-always the same magnitude (in a given cell type) -always the same duration (in a given cell type) -can be transmitted across long distances -occur in axons -caused by opening and closing of voltage-gated ion channels

Question 28

cell to cell communication types

Answer 28

1. electrical 2. chemical (ionotrophic and metabotrophic)

Question 29

electrical synapses

Answer 29

gap junctions composed of connexin proteins connect presynaptic and postsynaptic cell membranes (pore allows fast chemical and ionic transmission)

Question 30

ionotrophic receptors

Answer 30

-ligand-gated channels -rapid changes in post synaptic membrane potential

Question 31

metabolic receptors

Answer 31

-signaling cascade opens ion channels -activates intracellular transduction pathway -slower changes in postsynaptic membrane potential -can also modify proteins and gene expression (learning and memory)

Question 32

simple neural networks

Answer 32

sensory information detected by receptor --> signal transmitted from a sensory neuron --> efferent neuron --> effector organ (response)

Question 33

reflex arc

Answer 33

-simple neural circuits that do not involve the conscious centers of the brain -involuntary -simple (2 neurons) or complex (many neurons) -autonomic (e.g. reflex of control of blood pressure) -somatic (e.g. knee-jerk reflex)

Question 34

ancestral form neural network

Answer 34

receptor cell directly innervates an effector cell (little processing, no CNS)

Question 35

monosynaptic neural network

Answer 35

sensory neuron synapses with efferent neuron (e.g. knee-jerk reflex)

Question 36

polysynaptic neural network

Answer 36

at least one interneuron between sensory and efferent neuron (increases processing capacity)

Question 37

convergence

Answer 37

many afferent neurons synapse with one efferent neuron

Question 38

divergence

Answer 38

one afferent neuron synapses with many efferent neurons (allows a single signal to control many independent processes, and it is a way to apmplify the signal)

Question 39

sensitization

Answer 39

an increase in the response to a gentle stimulus after exposure to a strong stimulus -electric shock to tail sensitizes response to siphon stimulation -occurs via facilitating interneurons