cells, development

what are the two general classes of cells in the nervous system? what are the ranges of estimates for the quantity of each?

neurons (86-200 billion) and glial cells (1/2 - 2x as many as neurons)

function of a neuron

sends messages to other neurons about sensory info and motor activity

parts of a neuron

dendrites, cell body (soma), axon, terminal buttons, synapse

dendrite

message receiver

axon

where the message travels from cell body to terminal buttons

terminal buttons

where neurotransmitters are sent

myelin sheath

cells wrapped around the axon with little gaps called nodes of ranvier. the action potential that needs to travel down the axon jumps in between the myelin sheath on the gaps. without the myelin sheath the action potential would move much slower

types of glial cells

microglia, astrocytes, oligodendrocytes, schwann cells

microglia

waste control. eats trash in brain

astrocytes

star shaped. form blood brain barrier

oligodendrocytes

form myelin sheath in central nervous system

schwann cells

form myelin sheath in peripheral nervous system

differences between oligodendrocytes and schwann cells

1. oligodendroytes are in the central nervous system and schwann cells are in the peripheral

2. one schwann cell forms one small part of the sheath while one oligodendrocyte can myelinate multiple axons of multiple cells

what is the difference in composition between grey and white matter? where is grey matter found in the brain?

grey matter is mostly cell bodies and white matter is mostly axons

grey matter is found mostly in outer areas of the brain surrounding the white matter

what is the relationship between fibers, tracts, and pathways?

fibers can form together to make pathways. pathways can form together to make tracts

what, in general, is multiple sclerosis (ms)?

ms is when a person starts to lose their myelin sheath, specifically oligodendrocytes

what is the proximal cause of multiple sclerosis? what do people think causes that?

ms is an autoimmune disease. most people think it is caused from genetic susceptibility, brought on by some environmental trigger

what categories of symptoms occur in multiple sclerosis?

sensory, motor, cognitive, emotional

can be one or multiple

what are the two possible explanations for emotional symptoms of ms?

could either stem from the disease itself or depression surrounding the diagnosis

what is the prevalence of ms in the us? what is the status of latitude-observation on the incidence of ms across the world? what is the role of ethnic background to the risk of ms?

3/1000 people in the us are diagnosed

higher prevalence in northern countries, but highest prevalence among certain races, not just dependent on latitude

certain groups of people in northern countries may have higher genetic risk to ms

what is the usual age of onset of ms? what is the gender difference?

age of onset: 20-40

gender difference: 3 times as many women

what are the 3 characteristics of ms that get treated?

1. speeding the recovery from an attack'

2. reducing relapses'

3. slowing the progression of the disease

what is neurogenesis? when does it take place?

neurogenesis: creation of new neurons

takes place: early on in embryonic development and into year 1-2

what is migration? when does it happen?

migration: moving cells to their right spots

takes place: starts before birth and continues into childhood, around age 3-4

what is synaptogenesis? when does it start and how long does it continue?

synaptogenesis: creation of new synapses

takes place: starts as embryo and continues throughout whole life

what is myelination? when does it take place?

myelination: creation of myelin sheaths

takes place: starts early pregnancy and continues into early thirties

what is synaptic pruning? when does it take place?

synaptic pruning: getting rid of synapses we don’t need

takes place: starts early pregnancy, continues into teenage years/late twenties

3 layers of embryonic plate?

ectoderm, endoderm, mesoderm

ectoderm

nervous tissue and epidermis

endoderm

linings like gastrointestinal tract and digestive, respiratory, and urinary systems

mesoderm

forms muscles

when does the neural tube close on average at the anterior and posterior pores?

24-28 days after conception

what are the defects that occur when the pore does not close? which type of nonclosure has more serious effects?

anterior: anencephaly (baby has no functioning brain, more serious)

posterior: spina bifida (split spine. nerves are usually fine because vertebrae and meninges are fine

lissencephaly/agyria

issue with migration of neurons. sulci and gyruses never form. smooth brain.

microencephaly

small head. very rare but in news because of zika virus in Brazil. caused by brain development