nervous system

Question 1

fda

Answer 1

nerve cells communicate ia electrical and chemical signals. immediate response, rapid and specific

Question 2

functions of nervous system

Answer 2

Sensory input
Information gathered by sensory receptors about internal and external changes
Integration
Processing and interpretation of sensory input
Motor output
Activation of effector organs (muscles, glands and adipose) produces a response

Question 3

cns vs pns: afferent vs efferent

Answer 3

The Nervous System can be divided into 2 parts:
Central Nervous System (CNS)
Brain
Spinal Cord
Peripheral Nervous System (PNS)
Sensory (Afferent) Neurons
Motor (Efferent) Neurons
Sensory (Afferent) Neurons: neurons that transmit sensory information to the CNS.
Motor (Efferent) Neurons: neurons that carry signals from the CNS to the target cells and organs.

Question 4

somatic vs autnonomic

Answer 4

somatic motor neurons innvervate: muscles skeletal

autonomic efferent neurons: involuntary functions like cardiac and smooth

Question 5

cells of nervous system

Answer 5

The Nervous System is composed of 2 cell types:
Neurons (or Nerve Cells) – the basic signaling unit; excitable cells that transmit electrical signals and release neurocrines
Glial Cells (or Glia or Neuroglia) – Small, support cells that surround and wrap delicate neurons

Question 6

interneurons

Answer 6

Interneurons (short for interconnecting neurons) are neurons that lie entirely within the CNS
Come in a variety of forms but often have quite complex branching processes that allow them to communicate with many other neurons.
99% of body’s neurons

Question 7

sensory neurons

Answer 7

Sensory neurons carry information about temperature, pressure, light, and other stimuli from sensory receptors to the CNS.
Peripheral sensory neurons are pseudounipolar with cell bodies close to the CNS and very long processes that extend out to receptors in the limbs and internal organs.
Sensory neurons in the nose and eye are much smaller bipolar neurons.

Question 8

types of neurons

Answer 8

Neurons may be classified either structurally or functionally. 
4 Structural categories
Pseudounipolar
Bipolar
Anaxonic
Multipolar
3 Functional categories of neurons:
1.   Sensory (Afferent) neurons
2.   Interneurons
3.   Motor (Efferent) neurons

Question 9

neurons

Answer 9

Cell Body – resembles a typical cell with a nucleus and all organelles. An extensive cytoskeleton extends outward into the dendrites and axon.

Dendrites – thin, branched processes that receive incoming information from neighboring cells.

Axon – transmits outgoing electrical signals from the integrating center of the neuron to the end of the axon. Long axons are called nerve fibers.

Question 10

nerves

Answer 10

Nerve Fibers of both afferent and efferent peripheral neurons are bundled together with connective tissue into cord-like fibers called nerves.

Sensory nerves – nerves that carry only afferent signals
Motor nerves – nerves that carry only efferent signals
Mixed nerves – nerves that carry signals in both directions

Question 11

efferent

Answer 11

Efferent neurons have enlarged axon terminals
Carry signals from the CNS to the target (effector) cells.

Multipolar neurons have many dendrites and branched axons. This structure is commonly used to teach how a neuron functions.

Question 12

neural terminology

Answer 12

The region where an axon terminal meets its target cell is called a synapse.
The neuron that delivers a signal to the synapse is known as the presynaptic cell, and the cell that receives the signal is called the postsynaptic cell.
The narrow space between the two cells is called the synaptic cleft. 30 – 50 nm wide (~1/1,000,000th of an inch)

Question 13

axonal transport

Answer 13

Axons are specialized to convey chemical and electrical signals.
Proteins synthesized in the cell body are moved down the axon by a process known as axonal transport.
Slow axonal transport
Moves material by slow axoplasmic (cytoplasmic) flow at 0.2-2.5 mm/day
Carries components that are not quickly consumed by the cell, such as enzymes and cytoskeleton proteins.
Fast axonal transport

Moves organelles at rates of up to 400 mm/day
The neuron uses stationary microtubules as tracks which transport vesicles and mitochondria with the aid of attached foot-like motor proteins which “walk” via the tracks and using ATP.

Question 14

anterograde, retrograde transport

Answer 14

Fast axonal transport goes in two directions
Forward (or anterograde) transport moves synaptic and secretory vesicles and mitochondria from the cell body to the axon terminal.
Backward (or retrograde) transport returns old cellular components from the axon terminal to the cell body for recycling.

Question 15

neuroglial cells

Answer 15

Outnumber neurons by anywhere between 10-50 to 1
Provide not only physical support for neurons but also communicate with and provide important biochemical support to neurons.
The Central Nervous System has 4 types of glial cells
Oligodendrocytes
Microglia
Astrocytes
Ependymal cells
The Peripheral Nervous System has 2 types of glial cells
Schwann cells
Satellite cells

Question 16

astrocyte, microglia

Answer 16

astrocyte
- Most abundant Glial Cells
Cling to neurons, synaptic endings, and capillaries
Functions include support and brace neurons; play role in exchanges between capillaries and neurons; create blood-brain barrier; guide migration of young neurons; control chemical environment around neurons
Microglia
Act as scavengers and monitor neurons; migrate toward injured neurons
Can transform to phagocytize microorganisms and neuronal debris

Question 17

ependymal cells

oligodendrocytes

Answer 17

ependymal cells
Line the central cavities of the brain and spinal column
Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells
Oligodendrocytes
- Branched cells that form processes which wrap CNS nerve fibers, forming insulating myelin sheaths
can myelinate multiple nerve fibers

Question 18

satellite schwann

Answer 18

satellite cells
Surround and support neuron cell bodies in PNS
Function similar to astrocytes of CNS
schwan
Surround and support neuron cell bodies in PNS
Function similar to astrocytes of CNS. only myelnates one nerve fiber

Question 19

myelin-forming glia

Answer 19

Neural tissue secretes very little extracellular matrix, and glial cells provide structural stability to neurons by wrapping around them.
Schwann cells in the PNS and oligodendrocytes in the CNS support and insulate axons by forming myelin, a substance composed of multiple concentric layers of phospholipid membrane.
Myelin also acts as insulation around axons and speeds up their signal transmission.

Question 20

Basic Electrical Principles

Answer 20

Many of the body’s solutes, including organic compounds such as pyruvate and proteins, are ions and therefore carry a net electrical charge.
Potassium (K+) is the major cation within cells, and sodium (Na+) dominates the extracellular fluid.
On the anion side, chloride ions (Cl-) mostly remain with Na+ in the extracellular fluid.
Phosphate ions and negatively charged proteins are the major ions of the intracellular fluid.
The differences in ion distribution between body compartments also creates a state of electrical disequilibrium.
The cell membrane is an effective insulator.

Question 21

Basic Electrical Principles

Answer 21

(a) An artificial cell filled with molecules that dissociate into (+) and (-) ions. The membrane is impermeable to ions but water can freely cross.
This system is at chemical and electrical equilibrium

(b) An active transporter is inserted into the membrane. This carrier uses energy to move (+) ions out of the cell against their concentration gradient.
The (-) ions attempt to follow but remained trapped because the membrane is impermeable to ions. The (+) ions might try to move back in but also are impermeable.
This creates an electrical gradient

Question 22

resting membrane potential

Answer 22

The active transport of positive ions out of the cell creates an electrical gradient along with a concentration gradient with more positive ions outside the cell than inside = electrochemical gradient.
An electrical gradient between the ECF and ICF is known as the Resting Membrane Potential Difference (or Membrane Potential for short).
The resting part of the name comes from the fact that this electrical gradient is seen in all living cells. In these “resting” cells, the membrane potential has reached a steady state and is not changing.
The potential part of the name comes from the fact that the electrical gradient created by active transport of ions across the cell membrane is a form of stored, or potential energy. When oppositely charged molecules come back together, they release energy that can be used to do work. The work done by electrical energy includes sending signals.
The difference part of the name is to remind you that the membrane potential represents a difference in the amount of electrical charge inside and outside the cell.
Voltage is a measure of potential energy generated by separated charge. Measured between two points in millivolts (mV).
In living systems, by convention, the extracellular fluid is assigned a charge of 0 mV.
For nerve and muscle cells, the voltmeter will record a resting membrane potential between -40 and -90 mV, indicating that the ICF is negative relative to the ECF (0 mV).
(less voltage/potential energy inside vs outside for -40/-90)

Question 23

fdsa

Answer 23

3 k in 2 na out. both cations

Question 24

df

Answer 24

cells have lots of k leak channels. (always open). so slwoly leaking outside. keep leaking until is -90 mV. Equilbirum potential of Kis -90mV. it means it keeps leaking out until -90 which is equilibrium. Ek+= -90 mV. Ena+ = +60 mV. if leaky na channels stops at 60. CASES IF ONLY HAVE ONE OF EACH. our cells have both leak channels at same time. more K leak than NA. -70 mV for many cells is the resting potential. sodium pottassium ATPase counteracts the leaking of 3 k out and 2 na in.

Question 25

resting membrane potential

Answer 25

Resting membrane potential in an actual cell.
Is about -70 mV (depending on cell)
Most cells are about 25-40x more permeable to K+ than to Na+.
As a result, a cell’s resting membrane potential is closer to the EK of -90 mV than to the ENa of +60 mV.

Resting membrane potential is influenced by:

1. Concentration gradient of ions
2. Membrane permeability to those ions

Question 26

what influences the resting membrane potential.

Answer 26

other channels like chemically gated channels can influence the mV of inside cell. -70 is at rest with the leaking channels and the atpase.
also by changing the concentration gradient. if increasing the NA alot more outside then itis more movement inside the cell and become more positive.

Question 27

what are the 4 ions that influence resting membrane potential

Answer 27

k (inside) na (outside) cl (outside) ca (outside)

Question 28

ecf membrane potential

Answer 28

0

Question 29

membrane potential difference

Answer 29

membrane potential difference: Vm difference in mV b/w ecf and icf

Question 30

depolarization

Answer 30

membrane potential becomes more positive or less negative. by moving NA inside as well as CA. if becoming more positive Vm decreases. best way is NAchannels.

Question 31

repolarization

Answer 31

membrane potential goes back down to resting. ATPase puts Na back outside the cell. NA K ATPase.

Question 32

hypolarization

Answer 32

resting potential becomes more negative. move K out or, Cl in. Vm increases. best is CL channels.

Question 33

what depolarizes

Answer 33

entry of CA+ or NA+ depolarizes

Question 34

what hyperpolarizes

Answer 34

entry of Cl- hyperpolarize (and k)

Question 35

Electrical Signals in Neurons

Answer 35

Neurons and muscles are described as excitable tissues because of their ability to propagate electrical signals rapidly in response to a stimulus.
Changes in membrane potential are the basis for electrical signaling.
Ion flow creates an electrical current and voltage changes across membrane

Question 36

change in permability

Answer 36

How does a cell change its ion permeability?
The simplest way is to open or close existing channels in the membrane.
Neurons contain a variety of gated ion channels that alternate between open and closed states.
Mechanically gated ion channels are found in sensory neurons and open in response to physical forces such as pressure or stretch.
Chemically gated ion channels in most neurons respond to a variety of ligands, such as extracellular neurotransmitters and hormones or intracellular signal molecules
Voltage-gated ion channels respond to changes in the cell’s membrane potential. Voltage-gated Na+ and K+ channels play an important role in the initiation and conduction of electrical signals along the axon.

Question 37

change in ion permability

Answer 37

Ion channels are usually named according to the primary ion(s) they allow to pass through them.
There are 4 major types of selective ion channels in the neuron:
Na+ channels
K+ channels
Ca2+ channels
Cl- channels
The ease with which ions flow through a channel is called the channel’s conductance.
Channel conductance varies with the gating state of the channel, for example the K+ leak channels spend most of their time in an open state. Other channels have gates that open or close in response to particular stimuli.