#01

Question 1

how do electrical synapses work?

Answer 1

ions or small molecules go
from one cell to another through channels present in the cell
membranes of both cells.

Question 2

chemical synapses can be a or b

Answer 2

Ionotropic: neurotransmitter binds to receptors on the postsynaptic membrane, causing ion channels to open.
 Depolarization of the cell membrane initiates an excitatory postsynaptic potential (EPSP).
 Hyperpolarization of the cell membrane initiates an inhibitory postsynaptic potential (IPSP).
 Effects are direct and rapid.
o Metabotropic: Neurotransmitters that are neuromodulators bind to G-protein coupled receptors and have a slower, indirect effect on ion channels through second messenger systems.

Question 3

The resting membrane potential is established by

Answer 3

 Chemical forces, which tend to distribute each ion evenly inside and outside the cell, by diffusion through non-gated ion channels
 Electrical forces, which tend to equalize the electrical charge inside vs. outside the cell (opposite charges attract, like charges repel), and
 The sodium potassium pump, an active transport protein that uses energy in the form of ATP to move Na+ out of the cell and move K+ into the cell

Question 4

when the neuron is at rest, it is polarized. The inside concentration of a is higher, and on the outside concentration of b is higher

Answer 4

a: K
b: Na

Question 5

The resting membrane potential is established by

Answer 5

 Chemical forces, which tend to distribute each ion evenly
inside and outside the cell, by diffusion through non-gated
ion channels
 Electrical forces, which tend to equalize the electrical
charge inside vs. outside the cell (opposite charges attract,
like charges repel), and
 The sodium potassium pump, an active transport protein
that uses energy in the form of ATP to move Na+ out of the
cell and move K+ into the cell

Question 6

If the postsynaptic potential at the initial segment reaches a
threshold level of depolarization (approximately -55 mV),

Answer 6

voltage-gated Na+ channels will open and Na+ ions will flow into
the cell, rapidly depolarizing the cell membrane and initiating an
action potential.

Question 7

Propagation

Answer 7

advancement of an action potential in a single direction along the length of a membrane. Propagation
typically does not proceed in the opposite direction
because Na+ channels are in a refractory state for a few
milliseconds after they are opened. In a refractory state,
they cannot be influenced by changes in membrane
potential.

Question 8

saltatory conduction

Answer 8

action potential happening at myelinated axons

Question 9

transmission at chemical synapses

Answer 9

o Arrival of an action potential at the presynaptic membrane opens
voltage-gated calcium channels, permitting influx of Ca++ ions
into the axon terminal. This influx of Ca++ triggers the fusion of
synaptic vesicles with the presynaptic membrane.
o Through exocytosis, neurotransmitter is released into the
synaptic cleft, where it diffuses across the cleft and binds to a
receptor on the postsynaptic membrane

Question 10

3 types of neurotransmitters

Answer 10

o Amino acids: Small molecules that are fast acting and either excitatory
or inhibitory
* Examples of excitatory amino acids include
glutamate and aspartate
* Examples of inhibitory amino acids include GABA
(gamma-amino-butyric acid) and glycine
o Amines: Small molecules that are neuromodulators, typically
binding to a G-protein coupled receptor and having a
the slower effect, through second messenger systems
 It can be either excitatory or inhibitory, depending on the
receptor it binds to.
 Examples include acetylcholine, the catecholamines
(dopamine, epinephrine, norepinephrine), serotonin, and
histamine.
o Peptides: Large molecules that also act through a second messenger
systems and can be either excitatory or inhibitory,
depending on the receptor.
 Examples include dynorphin, beta-endorphin, enkephalin
and substance P.

Question 11

Astrocytes two types

Answer 11

Fibrous astrocytes in white matter
Protoplasmic astrocytes in gray matter

Question 12

Astrocytes functions

Answer 12

 Physical and nutritional support for neurons of CNS
 Separate neurons from each other, occupying much of the
space in the CNS.
 Surround all neural elements and form a perivascular
covering around blood vessels
 Control concentration of ions in the extracellular space
 Metabolize extracellular neurotransmitters
 Regulate development, stabilization and functions of
synapses
 Provide a scaffold during development, for newly formed
neurons to migrate to their final destination

Question 13

Oligodendroglia

Answer 13

Most numerous in white matter
forms myelin sheats

Question 14

microglia

Answer 14

resides in substances of the CNS
remove pathogens and cellular debris by phagocytosis after neural damage

Question 15

ependymal cells

Answer 15

The epithelial lining of the ventricles of the brain and the central canal of the spinal cord
possess cilia that help to circulate cerebrospinal fluid