Organization of the PNS (10/10b) [Biomedical] Flashcards Preview

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Flashcards in Organization of the PNS (10/10b) [Biomedical] Deck (40)
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1
Q

Neuron

A

Fundamental functional unit of the nervous system

Has axons and dendrites

2
Q

4 Main Functional Regions of Neurons

A

Input — area of neuron that receives input

Integrative — integrates all inputs coming into the cell body

Conductive — inputs are transmitted to a distant region of the neuron

Output — area of neuron that creates output

3
Q

Types of Neurons

A
Sensory*
Motor* 
Local interneuron
Projection interneuron
Neuroendocrine cell
4
Q

Soma Structure - Soma

A

main integrative unit of neuron, supports basic metabolism of neuron

dendrites receive input from other neurons, soma integrates inputs, and signal is transmitted

5
Q

Soma Structure - Endoplasmic Reticulum (ER)

A

lipid and protein synthesis, biosynthesis and recycling of vesicles

6
Q

Soma Structure - Lysosomes

A

digest compounds, glycogen → glucose, part of axoplasmic transport system

7
Q

Soma Structure - Mitochondria

A

creates energy (ATP) through oxidative phosphorylation

8
Q

Soma Structure - Microtubules

A

axonal transport

9
Q

Soma Structure - Golgi Apparatus (GA)

A

storage of lipids and proteins

10
Q

Axon Functions

A

Transmission of information: propagation of action potential (EX: electric potentials)

Transportation of metabolically important materials to and from the soma to the axonal end (axonal transport system)

11
Q

Axonal Transport - Anterograde

A

from the center of the cell (soma) to the peripheral (axon tip)

12
Q

Axonal Transport - Retrograde

A

from the periphery of the cell (axon tip) to the center (soma)

13
Q

Schwann cells provide what?

A

protection and insulation

14
Q

Myelinated axons

A

In the PNS, Schwann cells myelinate axons by investing them with up to 300 concentric layers to form myelin sheath

15
Q

Unmyelinated axons

A

Do not have a myelin sheath, but are associated with and enveloped by Schwann cells, which provide trophic support

16
Q

How Do Neurons Transmit Information?

A

Cellular Mechanisms

  • resting membrane potential
  • post synaptic potential
  • action potential

Synaptic Mechanisms

  • convergence
  • divergence

Behavioral Mechanisms

  • feedback
  • feedforward
17
Q

Neuronal Cell Membrane

A

Barrier between inside/outside is semipermeable — blocks movement of some ions, allows some ions

Extracellular — more positive than inside, high Na+, high Cl-

Intracellular — more negative than outside, high K+, high proteins

18
Q

Forces that Guide Ion Movement

A

Electrostatic Force — like charges repel each other

Diffusion Force — ions tend to move from higher concentration to lower concentration
- more involved in generation of AP

19
Q

Electrostatic forces want to hold the ions where they are, but the diffusion forces are stronger and want to push K+ ___ and Na+/Cl- ___

A

K+ out

Na+/Cl- in

20
Q

Ion Channels - Overview

A

They are specific to certain ions (EX: potassium channels) and are usually gated

Not really active ion transport systems

Ligand gated, mechanical gated, voltage gated, or leakage

21
Q

Ion Channels - Ligand Gated

A

receptor on one end, when a neurotransmitter comes in contact with receptor site, ion channel opens

22
Q

Ion Channels - Mechanical Gated

A

stress applied to channel, opens the gate

23
Q

Ion Channels - Voltage Gated

A

only opens when there is a specific membrane potential across the membrane

24
Q

Ion Channels - Leakage

A

randomly opens and allows ions out

There are more potassium leakage channels than sodium leakage channels

25
Q

Sodium Potassium Pump

A

Active ion transport mechanism

Transports 3 Na+ ions out, and 2 K+ ions in

1 net negative charge inside the membrane

This transport is against the diffusion gradient of Na+ and K → requires ATP

26
Q

Resting Membrane Potential (RMP)

A

There is a difference in the charges across a membrane, and the inner part is negative

Important to maintain resting potential in order to control responses

27
Q

Mechanisms of RMP

A

PART 1 - POTASSIUM

  • There are many K+ leak channels are more permeable than Na+ leak channels
  • There is more K inside compared to outside.
  • Concentration gradient is strong for K+ to go from in to out
  • Lots of K+ leaves the cell making the inside of the neuron negative

PART 2 - SODIUM

  • Concentration and electrostatic forces forces Na+ to the inside of the cell
  • But the diffusion is slower because there are lesser Na+ channels open

PART 3
- Na+/K+ pumps are active mechanisms at resting membrane

28
Q

Change in RMP — Terminologies

A

RMP - the membrane is polarized carries negative charge on the inside

Depolarization — inside becomes less negative (aka normal polarity is being lost)

Hyperpolarization — inside becomes more negative (aka more polar than normal polarity)

29
Q

Excitatory Postsynaptic Potential (EPSP)

A

inside becomes more positive than resting,

membrane becomes depolarized

30
Q

Inhibitory Postsynaptic Potential (IPSP)

A

inside becomes more negative than resting, the membrane becomes hyperpolarized

31
Q

Action Potential - Generation

A

When EPSP reaches a threshold, it creates an action potential

Has depolarizing and repolarizing phases

Stimulus could be a signal from another neuron

Na+ channels open fast and close slow, K+ channels close and open slow

32
Q

Action Potential - Propagation

A

Action potential must be conducted down the axon

Sodium comes in, starts diffusion to neighboring regions of the axon and makes the regions depolarized

When it reaches the threshold, Na+/K+ channels open and more sodium enters

Further depolarizes down the axon and propagates the action potential

33
Q

Function of Myelin Sheath

A

It acts as an electrical insulator for parts of the axons, thus preventing action potential from developing

It allows accumulation of charge at the nodes of Ranvier (btwn 2 Schwann cells)
- the charge gets sucked in and jumps to the next node of Ranvier

Speeds up the conduction of action potential

Conduction in unmyelinated axon is much slower since you don’t get the accumulation of charge

34
Q

Increased action potential conduction velocity due to

A

Myelination

Larger axon diameter

35
Q

Nerve Fibers - Motor Axons

A

Myelinated, large diameter, muscle control

36
Q

Nerve Fibers - Sensory Axons

A

Myelinated — large diameter, touch, vibration, position perception

Thinly Myelinated — medium diameter, cold perception, pain

Unmyelinated — small diameter, warmth perception, pain

37
Q

Nerve Fibers - Autonomic Axons

A

Thinly Myelinated — smaller diameter, heart rate, blood pressure, sweating, GIT, GUT function

Unmyelinated — smallest diameter, heart rate, blood pressure, sweating, GIT, GUT function

38
Q

Spinal Cord

A

part of the CNS than profusely connects to the PNS

Vital two-way link between the brain and the periphery

Connects to the periphery via 31 pairs of spinal nerves

Spinal nerves are both sensory or motor

Cervical and lumbar enlargements

Longitudinal and Transverse Organization

39
Q

Dorsal vs Ventral

A
Dorsal = posterior
Ventral = anterior
40
Q

Spinal cord - Transverse Organization

A

Spinal segment with grey matter in the middle, surrounded by white matter

Dorsal root = afferent, sensory

Ventral root = efferent, motor