Lecture 2 - Neuro Introduction

Question 1

what is the main functional unit of the nervous system

Answer 1

neuron

Question 2

What makes up the CNS and PNS

Answer 2

CNS = brain and spinal cord
PNS = peripheral nerves and ganglia

Question 3

why is physiology so intimately associated with anatomy in the nervous system

Answer 3

because neurons really only do 2 things
1. conduct electrical signals (AP)
2. release chemical signals (neurotransmitters)

therefore must of what the nervous system does depends on where these processes occur

Question 4

what are the three functions of the nervous system

Answer 4

1. control of movement and some functions = motor nerves
2. detection of external stimuli = sensory nerves
3. integration of neuronal activity and connections between sensory and motor neurons = interneurons/association neurons (these are neurons within the CNS that are reponsible for behaviour, thought, emotions, etc

Question 5

neurons - parts and their functions

Answer 5

neurons have a cell body from which axons and dendrites project from it

dendrites receive info from sensory receptors and cell it to the nerve cell body

axons deliver electrical signals from the cell body to another neuron or an effect organ (muscle)

Question 6

how does the neuron perform the function of moving information rapidly

Answer 6

by conducting electrical impulses called action potentials from one location to another, then converting the electrical impulse to a chemical signal at a synpase

Question 7

is there more neurons or glia and supporting structures

Answer 7

more glia and supporting structures compared to neurons

Question 8

what are the classifications of neurons (4)

Answer 8

functional = motor neuron vs sensory neuron vs interneuron

structural = unipolar vs bipolar vs multipolar

pyramidal vs non pyramidal

projection neuron vs interneuron

Question 9

structural classification of neurons and common associated type of function

Answer 9

anaxonic = no obvious axon (some CNS neurons)

bipolar = 2 distinct processes from cell body (some special sense)

unipolar = dendrite and axon continuous (most sensory neurons)

multipolar = 1 axon, 2+ dendrites (motor neurons and CNS neurons)

Question 10

functional classification of neurons and how they carry signals

Answer 10

sensory/afferent = carry signals TO the CNS (so PNS–> CNS)

motor/efferent = carry signals FROM the CNS (think E = exit) (so CNS–>PNS)

interneurons = send signals from one neuron to another

Question 11

for sensory/afferent - how does the stimulus arise and get into the nerve?

examples?

Answer 11

via sensory receptors = any structure which upon receiving environmental stimuli, produces an “informative” nerve impulse. Practically speaking, these are composed of cells or modifications of the nerve cell itself that “tranduce” environmental stimuli into AP

photoreceptors, taste and smell receptors, golgi tendon organs, pacinian corpuscles

Question 12

what is an example of a sensory receptor

Answer 12

pacinian corpuscle

Question 13

what are the four types of glial cells

Answer 13

oligodendricytes, schwann cells, astrocytes, microglia

Question 14

where do you find oligodendrocytes vs schwann cells? what do they do?

Answer 14

-formation of myelin within the CNS = oligo

-formation of myelin within PNS = schwann cells.
also protection of unmyelinated axons within PNS (wraps axons without myelinating them)

Question 15

what is myelin, what does it do, what does it surround

Answer 15

-lipid rich non-conductive lipid/protein compound

-surrounds axons of some neurons in a pattern of nodes (not myelinated) and internodes (myelinated)

-facilitates rapid conduction of electrical impulses by saltatory conduction (signal jumps from node to node)

Question 16

where are astrocytes found? what do they do? what do they participate in?
** question on this

Answer 16

-they are found in the CNS and have a star like morphology

-1.provide structural support (scaffold), 2. regulate concentration of potassium (sit around outside of neurons to pick up potassium as needed, we dont want high conc of extracellular K), and 3. reabsorb GABA and glutamate (its detrimental if these concentrations get too high)

-participate in vascular functions = constriction of blood vessels, BBB

Question 17

what is the definition of the blood brain barrier

Answer 17

structural/anatomical feature of the vascular elements of the CNS which restricts solute passage between the blood and nervous tissue. large molecules cant pass easily, nor molecules with a high electric charge, nor poorly lipid soluble molecules

Question 18

what is the BBB maintained by

Answer 18

-astrocytic processes enveloping the capillaries
-a complete capillary endothelium (tight junction and no fenestrations)

Question 19

importance of the BBB

Answer 19

-limits pathogen/toxin entry into CNS
-limits drug delivery to CNS, sometimes a limiting factor in therapy with drugs that cannot easily pass through BBB

Question 20

what do microglia do, what are they, when are they activated, what happens normally vs when misdirected

Answer 20

-principal innate immune cell within the CNS
-tissue macrophages: derived from bone marrow monocytes that migrate into brain during development and possibly after

-have ability to divide in situ to increase numbers

-become activated in infection and injury = phagocytosis, cytokine and prostaglandin release

-normally clear pathogens and resolve infection but can participate in some pathology when overactive or misdirected (cause neuron damage)