Chapter 42 Neuroscience 1: Cells of the nervous system Flashcards
Define:
CNS
central nervous system
consists of the brain and the spinal cord
Define:
PNS
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.
Define
Neurons
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
Define
what are the three types?
Glia-
*supporting tissues to CNS and PNS.
1. Astrocytes
2. Microglia
3. Myelin Sheath
Astrocytes
- 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.
Microglia
participates in immune functions and remove cellular debirs produced by damaged or dying cells.
Myelin Sheath
- 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.
Node of Ranvier
- 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.
Movement of electrical impulses
- what are the functions of a neuron?
- What does an Axon do?
- what do dendrites do?
- Function of neuron is to move electrical impulses
- Axon (away) always carries impulse away from the soma or cell body
- Dendrites carries it towards the soma or cell body.
What is the soma/cell body?
what structures does it contain?
- 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
Dendrites/ dentritic tree
- 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
Axon
- 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
1. how does multiple sclerosis relate to the mylein sheath?
Multiple Sclerosis
2. how do drugs do to help with MS?
- 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
what is the difference between dendrities and axons?
- The Nissl substance extends into the dendrites not the axons
- Denstrities and axons are on opposite sections of the soma.
Axon Hillock
- part of the soma that is closest to the cell body
- important in the generation of the electrical signals that travel along an axon
axon terminals
end of the axons; it conveys electrical or chemical messages to other cells, such as other neurons or muscle or gland cells
definition and how does it help with conduction?
Saltatory conduction
- 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
Sensory neurons
detecting stimulu from outdie/detect internal conditions
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
fill in the blank
Sensoru neurons are ___
afferent, efferent, or neithe?
They are afferent (to bring toward)–> they transmit information from the periphery to the CNS
what does it mean to say that the sensory neurons bypass the soma?
- 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.
- Motos neurons
- They are ____
2nd Q: afferent, efferent, neither?
**cause some kind of response **
* Muscles = causes movement in the muscles
* Glands = cause secretions of hormones from endocrine glands
Efferent (carry from) neurons.
interneurons
- Forms interconnections between other neurons in the CNS
- One end connects to an efferent neurons and the other end connects to an afferent neuron
definition and steps to the reflex arc?
Reflex arc
- 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.
What are some examples of a startle reflex?
- 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-
Resting Membrane Potential
- 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.
resting membrane potentiall
diffusion of ion through membrane channels
- 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
general
Na+/K+- ATPase Pump
- 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
*
more specific
Na+ / K+ ATPase pump
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
protein alternates between 2 conformtations
Na+/K+ ATPase Pump
- 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
E1 conformation
- 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
E2 conformation
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
Switch back to E1 conformation
Release of K+ into cytosol because of lower affinity for the E1
Action Potentials
- 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.
Action Potential- Depolarization
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**
graded potential
not enough to generate an action potential - depolarization
threshhold Potential
- -55mV
- stimulate has to meet -55mV to trigger depolarization.
- If it’s under that, nothing will happen
depolarization (from the threshhold of excittation and the peak action potential)
- 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
repolarization
- 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
when Action potential (AP) occurs, neurons cannot __
neurons cannot be stimulated until the AP is complete and RMP is restored.
All the steps of Action Potential
- RMP = -70 mV
MUST reach Threshold = -55 mV - Depolarization with Na+ channels opening via positive feedback
- Na+ rush in = +30 to +40 mV
- Na+ channels change shape and become inactivated – Na+ stops moving
- Repolarization begins with action of Na+ K+ pumps and opening of K+ channels
- K+ rushing out
- Overshoot RMP and become hyperpolarized = -75 mV before all the K+ channels close
- Na+ K+ pumps bring neuron back to RMP
hyperoikarization
occurs when the cell membrane becomes more polarized, that is, more negative on the inside relative to the extracellular fluid.
