Neuro Exam 1

Neuron doctrine

brain composed of independent cells, signals transmitted from cell to cell across gaps (synapses)

Unipolar neuron

single extension branches in two directions, forming a receptive pole and an output zone

biopolar neuron

one axon, one dendrite

multipolar neuron

one axon, many dendrites, most common type

“star” brain cells

neurons

sensory neurons

respond to environment; light, odor, touch (PNS)

motoneurons

contact muscles or glands (PNS)

interneurons

receive input from and send input to other neurons, integration (most neurons in CNS)

glial cells

support the brain, non neuronal, in CNS and PNS, four kinds

astrocytes

glial cells, star shaped, fill spaces between neurons for support, provide blood-brain barrier, regulate composition of the EC.

oligodendrocytes

wrap axons with myelin sheaths inside brain and spinal cord, wrap several axons, form segments of myelin sheath; nodes of ranvier where axon membrane is exposed

multiple sclerosis

glial cells, oligodendrocyte injury from autoimmune attack

microglia

glial cells, cells move around, clean up debris from dying neurons and glia

ependymal cells

glial cell, line ventricles, secrete and absorb cerebral spinal fluid

AIDS encephalitis

brain damage in patient from neurotoxins glutamate and nitric oxide from viral activated microglia (glial cell)

dendritic spines

increase surface area and can CHANGE, they have neural plasticity, number and structure rapidly altered by experience

Synapse

Central Nervous System (CNS)

brain and spinal cord

Peripheral Nervous System (PNS)

cranial nerves, spinal nerves

autonomic nervous system

Sympathetic and parasympathetic nervous system, brainstem and spinal cord

sympathetic nervous system

prepares body for action, spinal cord

parasympathetic nervous system

brainstem and bottom of spinal cord, rests and digests

basal ganglia

movement control, center of the brain, contains the thalamus

limbic system

emotional memory, regulation, olfactory bulb, amygdala, hippocampus, thalamus

cerebellum

very back, lower end of brain, motor coordination and learning

horizontal, separates brain from top to bottom

sagitall, slices brain down the midline

coronal, separates brain from front to back, butterfly

medial

towards the middle

ipsilateral

same side

anterior

head end (FRONT)

proximal

center

dorsal

towards the back

lateral

side

contralateral

opposite side

posterior

tail end

ventral

towards stomach

afferent

carries neural information TOWARDS region of interest (sensory)

efferent

carries neural information AWAY from region of interest (motor)

white matter

composed of axon bundles, appear white because myelin sheaths (white fatty tissue) covers the axons

gray matter

composed of clusters of neuron cell bodies, dark gray appearance

reticular formation

part of mid brain, sleep, arousal, body temperature

meninges

brain wrappings

top arrow

dura mater

second arrow

subdural space

third arrow

arachnoid membrane

fourth arrow

subarachnoid space

fifth (tiny) arrow

pia mater

second to last arrow

artery

last arrow

brain

subdural hematoma

collection of blood between the brain and dura mater, caused by head trauma

cerebral ventricles

make CSF (cerebrospinal fluid)- surrounds and cushions brain

CSF (cerebrospinal fluid) flow

produced inside the brain, circulates around the border from front to back and exits the brain

hydrocephalus

CSF circulation failure, too much CSF, swollen head

white matter tracts

connect brain areas, short and long distance

CT scan

black and white, shows tissue density, whiter means denser, view from above the head

MRI

protons line up in parallel, pulse of radio waves knocks protons over, they reconfigure, emitting radio waves differing by tissue density

PET scan

brain activity, inject radioactive chemicals to map their destinations, few clinical uses

functional MRI (fMRI)

brain activity, detects change in brain metabolism like oxygen use, shows how networks of brain structures collaborate, shows all views of brain (3D)

DTI

images of axons of neurons, showing brain connections, up and down axons are BLUE, front to back of brain axons are GREEN

soma

cell body

rough ER

membranes with ribosomes (rough/bumpy) protein synthesis site, surrounds nucleus

smooth ER

regulates cytoplasm, no bumps on it

Golgi apparatus

stacks of flat membrane compartments, packages products for shipment in cell

neuron membrane

lipid bilayer, surrounds cell and separates cytoplasm from ECF

intrinsic proteins

receptors, ion channels, give neurons the necessary properties for signaling

cytoskeleton

structural support, microtubules, neurofilament, microfilament

microtubules

20nm tubes straight up and down look like hollow circles inside neuron

neurofilaments

10nm twisted cables, static support structures, look like tiny dots

anterograde transport

material moved from soma to terminals along microtubules using kinesis as enabling protein

retrograde transport

material moved from terminals towards soma via dynein as enabling protein

MELAS syndrome

Mitochondrial, Encephalopathy, Lactic Acidosis, Stroke: mitochondrial energy failure

neuron size

matters, larger neurons cover larger distance, more complex, and faster

semipermeable membrane

screen door, only allows certain things through

diffusion

ions flow from high to low concentration along their concentration gradient

electrostatic pressure

causes ions to flow towards OPPOSITELY charged ions. positive and negative go together

inside axon

negative charge

outside axon

positive charge

ion channels

proteins spanning the cell membrane so ions can pass in and out. neuronal cell membrane repels water and ions are surrounded by water so they can only enter through a channel

gated ion channels

open/close in response to voltage change, chemicals, mechanical action

neuron equilibrium

-60mV, negatively charged proteins inside, neurons are most permeable to K+, positively charged potassium (K+) moves into cell through potassium channels

sodium potassium pump

pumps Na+ out and K+ in to maintain -60mV

tetrodoxin

comes from fugu fish, blocks nerve action by blocking pores of sodium channels in neuron membranes, kills you because nerves can’t fire=no breathing or movement

graded potential

occurs in dendrites, as graded potentials spread across membrane, they diminish, bigger stimulus bigger response

action potential

graded potentials can turn into action potentials if the membrane reaches threshold, inside of the cell becomes briefly positive, occurs in the axon hillock- right next to the soma

all or none action potential

neurons fire at full amplitude or not at all

action potential first step

voltage gated Na+ channels open in response to initial depolarization

action potential second step

more voltage gated channels open and more Na+ ions rush in all at once until membrane potential hits +40mV

action potential third step

voltage gated Na+ channels close, action potential is achieved at +40mV

action potential fourth step

because of the Na+ the inside of the cell is more positive so voltage gated K+ channels open

action potential final step

K+ moves out and resting potential is restored

absolute refractory phase

+40mV, maximum, no more action potentials can be produced

relative refractory phase

the period after the absolute refractory phase when only a strong stimulation can produce an action potential, mV is on the decline

Na+ refractory period

inactivation gate locks during absolute refractory period and opens during action potential

nodes of ranvier

gaps in the myelin sheath on the axon, sodium and potassium channels are found

synapse signaling

electrical signal > chemical signal > electrical signal

chemical synapse transmission

action potential travels down axon to axon terminal, calcium channels open halfway down so Ca+ enters, synaptic vesicles fuse with membrane and release transmitter into the cleft

after transmitter is released into cleft

transmitter binds to postsynaptic receptor, causing EPSP or IPSP

EPSP

excitatory, depolarization, pushes cell closer to threshold, results from Na+ ions entering the cell making inside more positive, integrated by axon hillock

IPSP

inhibitory, hyper polarization, pushes cell away from threshold, results from Cl- ions entering cell, makes inside more negative, integrated by axon hillock