bio ch 5 nervous system

Question 1

what is the name of the cells that myelinate axons in the PNS and CNS, respectively

Answer 1

Schwann cells meyelinate PNS

Oligodendrocytes myelinate the CNS

CNS has the brain and the brain is very complex and oligodendrocyte is a more complex word than schwann is a way to remember.

Question 2

Dorsal vs ventral

Answer 2

Dorsal is back (DB)

Ventral front (VF engineering)

Question 3

What are the names of the 5 parts to an action potential

Answer 3

1. Resting membrane potential
2. Depolarization.
3. Repolarization
4. Hyperpolarization
   5.Return to resting

Question 4

How many Na and K does the Na/K pump and where does it pump them

Answer 4

3 sodium ions (Na⁺) OUT of the cell.
from the intracellular space

2 potassium ions (K⁺) INTO the cell from the extracellular space

The pump runs all the time, even during an action potential

Question 5

What is the resting membrane potential of an action potential

Answer 5

it is when the neuron is at rest with a potential of about -70 mV. The cell is more negative inside and more positive outside.

Question 6

what is Depolarization of an action potential

Answer 6

when a neuron is stimulated (by another neuron), ligand-gated Na+ channels open, causing the membrane potential to rise. When the membrane potential reaches ~ -50 mV ( a point known as the threshold potential) VOLTAGE-gated Na+ channels open and allow an influx of Na+ from outside the neuron to inside the neuron. The influx of Na+ is depolarization.

Question 7

what is the repolarizaiton of an action potential

Answer 7

Once the action potential has reaches it’s peak of depolarization around ~ +30mV, the voltage-gated Na+ channels close and become inactive for a short period. At the same time, voltage-gated K+ channels open, allowing an efflux of K+ from inside the neuron to outside the neuron ( remember the Na+/K+ pump has been pumping 3 Na+ out and 2 K+ in, so there is a lot of K+in the neuron). The K+ leaving the cell is repolarization.

Question 8

what is the hyperpolarization of an action potential

Answer 8

While the action potential is repolarizing (K+ leaving the cell) the K+ leaves continuously and so the membrane potential goes BELOW the resting potential of -70mV. when the potential is below -70 mV, that is known as hyperpolarization. Once the K+ channels close, the Na/K pump returns the neuron to its resting potential.

Question 9

what is a reflex arc

Answer 9

the neural pathway that a reflex takes in the body.

Question 10

monosynaptic vs. polysynaptic reflexes

Answer 10

monosynaptic - reflex arc consisting of only one synapse between the afferent and efferent neuron

Polynaptic - reflex arc consisting of at least one or more interneurons

Question 11

SAME DAVE

Answer 11

sensory - afferent
Motor -efferent

Dorsale afferent
Ventral -efferent

Question 12

what is a synapse

Answer 12

where 2 neurons meet.

Question 13

what is a neurotransmitter

Answer 13

small chemical messangers whcih get released from the presynaptic neuron, go across the synaptic cleft, then bind to receptor on the postsynaptic neuron

Question 14

difference between temporal and spatial summation

Answer 14

temporal - the additive effects of ONE axon terminal rapidly firing excitatory signals

Spatial - the additive effects of MULTIPLE axon terminals firing excitatory signals toward a single postsynaptic neuron.

Question 15

what is summation in the context of neurons

Answer 15

multiple signals sent into a scynaptic cleft which can add up and form a larger stimulus

Question 16

3 ways to remove neurotransmitters after it binds with postsynaptic neurons.

Answer 16

1. Reuptake - NT is shuttled back into the presynaptic neuron via a transporter.
2. enzymatic degradation - an enzyme breaks down the NT.
3. Diffusion- The NT diffuses out of the synaptic cleft.

Question 17

Absolute vs relative refractory period

Answer 17

Absolute- during depolarization and repolarization, another action potential cannot be initiated because Na+ channels are inactivated.

Refractory- during hyperpolarization, a stronger than normal stimulus CAN initiate an action potential, and only one Na+ channels are reactivated.

Question 18

what role do Ca2+ ions play in action potentials

Answer 18

at the axon terminal, Ca2+ voltage-gated channels are opened at the presynaptic membrane, allowing Ca2+ ions to rush in. Ca2+ triggers synaptic vesicles filled with Neurotransmitters to release their contents into the synaptic cleft via exocytosis.

Question 19

electrical vs chemical synapses

Answer 19

electrical - much less common and mainly found in cardiac cells

chemical- more common way to propagate action potentials

Question 20

excitatory vs inhibitory neurotransmitter

Answer 20

excitatory - will cause a postynaptic neuron to produce an action potential if enough of it is present

inhibitory - prevents postsynaptic membranes from producing action potentials

Question 21

Where are astrocytes found and what do they do

Answer 21

Astrocytes are cells found in the CNS and they:

-provide neurons with nutrients
-form the blood-brain barrier

Question 22

Where are ependemal cells found and what do they do

Answer 22

Found in the CNS and they:
- produce CSF in the ventricles of the brain

Question 23

Where are microglia found and what do they do

Answer 23

Found in the CNS and they:

-phagocytose pathogens and waste products
-derived from monocytes, a type of immune cell, so they play a role in neural immune support

Question 24

Where are Satellite cells found and what do they do

Answer 24

Found in the PNS and they provide structural support as well as general health and well being for neurons in the PNS

Question 25

what is synaptic pruning

Answer 25

the death of an entire neuronal pathway

Question 26

what is synaptic plasticity

Answer 26

the strengthening/weakening of neuronal pathways. More use leads to strengthening, less use leads to weakening. Use it or lose it.