Neurology

Question 1

Types of neuroglia

Answer 1

Astrocytes
Microglial
Ependymal
Oligodendrocytes

Question 2

Astrocytes

Answer 2

Most abundant
Cling to neurons, synapses, capillaries
- Support neurons structurally
- exchange b/w cap and neurons
- chemical environment control

Question 3

Microglial cells

Answer 3

Have Thorny processes that touch and monitor neurons

Migrate toward injured neurons

Phagocytize microorganisms and neuronal debris

Question 4

Ependymal cells

Answer 4

Can be squamous or columnar

MAY be ciliated to circulate CSF

line central cavities of brain and spinal column

Form permeable barrier between CSF in cavities and tissue fluid bathing CNS cells

Question 5

Oligodendrocytes

Answer 5

Process wrap CNS nerve fibers

Form insulating myelin sheaths in thicker nerve fibers - speeds conduction of signaling

Branched cells

Question 6

Major neuroglia in PNS

Answer 6

Satellite cells - similar to astrocytes - surround neuron cell bodies in PNS, structural support and neuron blood connection

Schwann cells (neurolemmocytes) - similar to oligodendrocytes; surrounds nerve fibers and forms myelin sheath in thicker nerve fibers. Imp in regeneration of damaged peripheral nerve fibers

Question 7

What are glial cells

Answer 7

Glial- Helper cells for neurons

Neurons- transmit signals

Question 8

Neuron structure

Answer 8

Large, highly specialized

Mostly amitotic (don’t self divide, last long time)

High metabolic rate - need continuous state of glucose and oxygen

All have cell body and 1+ processes

Question 9

Neuron cell body

Answer 9

Soma/perikaryon

Synthesizes proteins, membranes, chemicals

Has rough ER, nucleus, nucleolus

Plasma membrane is part of receptive region that gets input from other neurons

Most in CNS

• cluster in CNS - nuclei
• cluster in PNS - ganglia

Question 10

Neuron processes

Answer 10

Arm like projections
- CNS: cell bodies and processes
- PNS: chiefly neuron processes

Tracts: bundles of neuron processes in CNS

Nerves: bundles of neuron processes in PNS

two types of processes: dendrites and axons

Question 11

Are cranial nerves part of the CNS or PNS?

Answer 11

PNS!!!!

Question 12

Dendrites

Answer 12

Crlls can have 100s of dendrites

Receptive (input) region; convey incoming messages as graded potentials (short distance signals)

Have organelles, metabolic ability

Contain dendritic spines (have spinky or bulbous ends) in brain/CNS for collecting specific info

Question 13

Axon

Answer 13

Each neuron has 1 axon

Long axons = nerve fibers

Occasional branches called axon collaterals

Profusely branch at terminus

Distal endings called axon terminals

Transport molecules and organelles in both directions
-anterograde: away from cell; enzymes, mitochondria
- retrograde: toward cell. Viruses, toxins, signal molecules

Question 14

Myelin sheath

Answer 14

Myelin is protein-lipid substance

• Protects and electrically insulated axon > inc speed of nerve impulse transmission

Contains most long or large diameter axons

Question 15

Myelin sheath formed by __ in PNS

Answer 15

Schwann cells - one cell forms one segment of myelin sheath, wraps around axon in jelly roll fashion

Question 16

Myelin sheath gaps

Answer 16

Nodes of ranvier

Sites where axon collaterals can emerge

Question 17

Myelin sheath in CNS

Answer 17

formed by oligodendrocytes - each cell can wrap up to 60 axons at once

No perinuclear cytoplasm

Question 18

White matter vs grey matter

Answer 18

White: regions of brain and spinal cord with dense collections of myelinated fibers (usually fiber tracts)

Grey: mostly neuron cell bodies and non myelinated fibers

Question 19

Classification of neurons

Answer 19

Grouped by number of processes
- multipolar: 3+, 1 axon, multiple dendrites. Most common
- bipolar: 2+ (1 axon, 1 dendrite), rare. Retina and olfactory mucosa.
- unipolar: 1 T like process (two axons, or one long one crossing thru).
——-Peripheral/distal processes associated w sensory receptors
——-proximal (central) processes enter CNS

Question 20

Sensory neurons

Answer 20

• Almost all unipolar
• Impulses from sensory receptors toward CNS
• cell bodies in ganglia in PNS

Question 21

Motor neurons

Answer 21

• multipolar
• carry impulses from CNS to effectors
• most cell bodies in CNS (few exceptions in autonomic neurons)

Question 22

Interneurons

Answer 22

Association neurons
- lie between motor and sensory neurons
- shuttle signals through CNS (most are within CNS)
- 99% of our neurons are interneurons

Question 23

What are action potentials?

Answer 23

Long distance neural communications that only occur in muscle cells and axons of neurons

In neurons, also referred to as a nerve impulse

Involve opening of specific voltage gated channels; brief reversal of membrane potential

Question 24

Do APs decay over distance?

Answer 24

No

Question 25

Voltage gated channels with AP

Answer 25

Na and K

Question 26

Generation of AP

Answer 26

Resting state - all voltage gates closed, leakage channels open Each Na channel has two voltage sens gates: - activation gates (closed at rest) and inactivation gate (open at rest) Each K has one: - closed at rest, opens slowly with depolarization na opens, huge rush and depolarization, Na gates inactivate from pos membrane, k channels open > repolarization

Question 27

When does hyperpolarization occur?

Answer 27

Some K channels are open when Na channels reset Excessive K efflux, inside of membrane more neg than resting state > hyperpolarization (slight dip below resting voltage)

Question 28

Do all depolarization events cause an AP?

Answer 28

No - all or none phenomenon. AP happens fully or not at all