Chapter 42 Neuroscience 1: Cells of the nervous system

Question 1

Define:

CNS

Answer 1

central nervous system
consists of the brain and the spinal cord

Question 2

Define:

PNS

Answer 2

Periphery Nervous System
* All neurons and projections of their plasma membranes that are outside of but connect with the CNS, such as projections that end on muscle and gland cells.

Question 3

Define

Neurons

Answer 3

cells that send and receive electrical and chemical signals to and from each other and other types of cells throughout the body. There are different types of neurons

Question 4

Define

what are the three types?

Glia-

Answer 4

*supporting tissues to CNS and PNS.
1. Astrocytes
2. Microglia
3. Myelin Sheath

Question 5

Astrocytes

Answer 5

• Star shaped cells
• Provide metabolic support for neurons and are also involved in forming blood-brain barrier, which is a physical barrier between blood vessels and most parts of the CNS.
• It provides protection and Certain things cannot pass, and certain things cannot come out.

Question 6

Microglia

Answer 6

participates in immune functions and remove cellular debirs produced by damaged or dying cells.

Question 7

Myelin Sheath

Answer 7

• specialized glial cells that wrap around certain axons to form an insulating layer.
• fatty area that is around the axon
• fat acts as an insulator and allows for a faster conduction of the impulse.
• Not all axons have these. some do and some do not.

Question 8

Node of Ranvier

Answer 8

• non myelinated portion along the axon
• it allows for conduction called saltatorial conduction -jumping
• stimulus is going to jump, allowing for faster condcution of the impulse.

Question 9

Movement of electrical impulses

1. what are the functions of a neuron?
2. What does an Axon do?
3. what do dendrites do?

Answer 9

1. Function of neuron is to move electrical impulses
2. Axon (away) always carries impulse away from the soma or cell body
3. Dendrites carries it towards the soma or cell body.

Question 10

What is the soma/cell body?

what structures does it contain?

Answer 10

• Main part of the cell; nucleated, has a membrane bound cell called a nucleus.
• Function of nucleus- hold DNA
  Nissl substance/bodies
  consists of aggregates of ribosomes, whether they are or attached to ER
  Dendrites/dendritic tree
  *More than one extension off the soma or cell body

Question 11

Dendrites/ dentritic tree

Answer 11

• More than one extension off the soma or cell body
  Has to be at least one, usually more than one
• Electrical and chemical messages from other neurons are received by the dendrites, and electrical signals generated in the dendrites move toward the cell body

Question 12

Axon

Answer 12

• An extension of the cell body that transmit signals along its length and eventually to other cells.
• Only one axon per neuron which may or may not be insulating layer of myelin sheath

Question 13

1. how does multiple sclerosis relate to the mylein sheath?

Multiple Sclerosis

2. how do drugs do to help with MS?

Answer 13

• In the disease, the immune system attacks the myelin sheath
• this causes inflammation and injury to the nerve sheath and ultimately to the nerve fibers that it surrounds.
• it causes scars along the length of the axon. If impulses are not conducted well, it is slowed down or stopped, it affects the muscle movement
• there are drugs to trick the immune system. they help ramp up the immune system to decrease the inflammation and improve neuron function

Question 14

what is the difference between dendrities and axons?

Answer 14

• The Nissl substance extends into the dendrites not the axons
• Denstrities and axons are on opposite sections of the soma.

Question 15

Axon Hillock

Answer 15

• part of the soma that is closest to the cell body
• important in the generation of the electrical signals that travel along an axon

Question 16

axon terminals

Answer 16

end of the axons; it conveys electrical or chemical messages to other cells, such as other neurons or muscle or gland cells

Question 17

definition and how does it help with conduction?

Saltatory conduction

Answer 17

• the way an electrical impulse skips from node to node down the full length of an axon
• With myelin sheath and the nodes of Ranvier, it increases the speed in which electrical signals pass along the axon

Question 18

Sensory neurons

detecting stimulu from outdie/detect internal conditions

Answer 18

bypass the soma
* They detect or sense information from the outside world, such as light, odors, touch, or heat.
* They detect internal body conditions such as blood pressure or body temperature
* Afferent

Question 19

fill in the blank

Sensoru neurons are ___

afferent, efferent, or neithe?

Answer 19

They are afferent (to bring toward)–> they transmit information from the periphery to the CNS

Question 20

what does it mean to say that the sensory neurons bypass the soma?

Answer 20

• They have a long, single axon that branches into the peripheral process and a central process, with the cell body in between.
• This allows for the rapid transmission of a sensory signal to the CNS.

Question 21

1. Motos neurons
2. They are ____

2nd Q: afferent, efferent, neither?

Answer 21

**cause some kind of response **
* Muscles = causes movement in the muscles
* Glands = cause secretions of hormones from endocrine glands
Efferent (carry from) neurons.

Question 22

interneurons

Answer 22

• Forms interconnections between other neurons in the CNS
• One end connects to an efferent neurons and the other end connects to an afferent neuron

Question 23

definition and steps to the reflex arc?

Reflex arc

Answer 23

• allows an organism to respond rapidly to inputs from sensory neurons and consists of only a few neurons
  1. Stimulus from the outside (pin)
  2. Stimulus runs along the afferent neuron – sensory neuron
  3. Bypass the soma and the axon is going to head into the spinal cord
  4. It’s on the dorsal surface of the spinal cord
  It is a Quicker response because we don’t have to go to the BRAIN
  5. Contact with the interneuron – relay neuron
  6. going to connect to the efferent (motor neurons). It’s on the ventral surface
  7. Movement happens
  Movement cannot be stopped; it’s a reflex

can be any stimulus; in the picture it was a pin.

Question 24

What are some examples of a startle reflex?

Answer 24

• Temperature; hot
• Electric shock
• Some vertebrates will cringe, jump, leap, or take flight in response to a loud noise.

-watch video and add more notes-

Question 25

Resting Membrane Potential

Answer 25

* refers to the membrane potential of an unstimulated cell that is not generating action potentials. * it is not sending electrical signals (not generating any action potentials) * Charge = ions * it is -70 mV inside the cell with respect to the outside. * interior of the cell had a more negative charge than the exterior. * more negative on the inside than the outside.

Question 26

# resting membrane potentiall diffusion of ion through membrane channels

Answer 26

* Using sodium potassium pump Na+ K+ Pump NA+ K+ ATPase * Open on one side or the other to let it go through. * it allows for the establishment of ion concentration gradients

Question 27

# general Na+/K+- ATPase Pump

Answer 27

* uses the energy of ATP to transport 2 na+ out of the cell for every 2 K+ it moves into the cell. * it establishes the concentration gradients of Na+ and K+ by continually transporting them acorss the membrane in opposite directions *

Question 28

# more specific Na+ / K+ ATPase pump

Answer 28

Antiport * Couples the export of Na+ and import of K+ [Na+] is lower inside cell and higher out [K+] is higher inside cell and lower out * Active transport of these ions against their [ ] gradients using energy from ATP hydrolysis ATP --> ADP + P Pumps out 3 Na+ Pumps in 2 K+ * Thousands of pumps per cell all maintaining to RMP | antiport- moves two different things moving against each other

Question 29

# protein alternates between 2 conformtations Na+/K+ ATPase Pump

Answer 29

* E1 & E2 * E1 binding sites are accessible from the cytosol Na+ binds tightly; have a higher affinity K+ has a lower affinity * E2 binding sites accessible from the outside (extracellular environment) Na+ has a lower affinity K+ binds tightly

Question 30

E1 conformation

Answer 30

* Open to cytosol * 3 Na+ bind to Na+/K+ ATPase because of their higher affinity * ATP hydrolyzed to ADP + P P covalently binds to pump = phosphorylation

Question 31

E2 conformation

Answer 31

switched to E2 Open to external environment 3 Na+ released outside the cell because they have a lower affinity for the E2 2 K+ bind to Na+/K+ ATPase because of their higher affinity Binding of K+ causes the release of P | from E1 and then it switched to E2

Question 32

Switch back to E1 conformation

Answer 32

Release of K+ into cytosol because of lower affinity for the E1

Question 33

Action Potentials

Answer 33

* Change in amount of electric charge across a neuron’s plasma membrane * Electrical signal travels from axon hillock to axon terminal | watch and add notes from videos.

Question 34

Action Potential- Depolarization

Answer 34

**RMP is -70 mV** PM becomes less polarized (less negative inside compared to RMP) Na+ channels open – Na+ diffuses in and makes membrane potential less negative **Must reach a threshold potential** – a large enough difference to trigger voltage-gated channels to open and the action potential to occur Around **-55 mV** All-or-None Response * *If the threshold is not met, then the neuron goes back to its resting state* * *If threshold is met, then the neuron depolarizes**

Question 35

graded potential

Answer 35

not enough to generate an action potential - depolarization

Question 36

threshhold Potential

Answer 36

* -55mV * stimulate has to meet -55mV to trigger depolarization. * If it's under that, nothing will happen

Question 37

depolarization (from the threshhold of excittation and the peak action potential)

Answer 37

* occurs when the cell membrane becomes less polarized; less negative inside the cell relative to the surroudning fluid. * * Voltage-gated Na+ channels open * Na+ rushes into the cell * Causes further depolarization and more Na+ channels to open POSITIVE FEEDBACK * Trying to approach equilibrium but it is never reached for Na+ * Potential reaches +30 to +40 mV * Sends the signal down the axon

Question 38

repolarization

Answer 38

* Voltage-gated K+ channels open * K+ rush out of the cell to try to reach equilibrium * Goes too far beyond RMP = hyperpolarization occurs briefly *-75 mV* * 4 - overshoot* * All the voltage-gated channels close and Na+ K+ ATPase/pump brings the charge back to RMP

Question 39

when Action potential (AP) occurs, neurons cannot __

Answer 39

neurons cannot be stimulated until the AP is complete and RMP is restored.

Question 40

All the steps of Action Potential

Answer 40

1. RMP = -70 mV **MUST reach Threshold = -55 mV** 2. Depolarization with Na+ channels opening via positive feedback 3. Na+ rush in = +30 to +40 mV 4. Na+ channels change shape and become inactivated – Na+ stops moving 5. Repolarization begins with action of Na+ K+ pumps and opening of K+ channels 6. K+ rushing out 7. Overshoot RMP and become hyperpolarized = -75 mV before all the K+ channels close 8. Na+ K+ pumps bring neuron back to RMP

Question 41

hyperoikarization

Answer 41

occurs when the cell membrane becomes more polarized, that is, more negative on the inside relative to the extracellular fluid.