bio 37 midterm 1

how heavy is the average brain?

2.5 lbs

how much cerebrospinal fluid is there on the outside/inside of the brain?

½ of a cup

how many neurons? how many inputs does each have? how many glial cells per neuron? what is the diameter of each one?

1) 10^12 neurons

2) thousands of inputs, up to 150k

3) 20 glial helper cells per neuron

4) diameter = 8-80 micrometers

how many miles of axons in a brain? how fast do they conduct signals?

100k miles of axons conducting at 200 mph

how much of the body’s blood flow and energy does the brain use?

20%

what percentage of human genes are expressed in the brain?

25%

dementia — is it a group of disorders? or just 1

group of disorders that affects memory, thinking, and interferes with daily life

is a majority of dementia disorders reversible or irreversible? stats?

most are irreversible (85%-95%)

around 5%-15% are reversible

examples of irreversible dementia (6)

1) alzheimers

2) dementia with lewy bodies

3) fronto-temporal dementia

4) vascular dementia

5) parkinsons disease dementia

6) traumatic brain injury

examples of reversible dementia (5)

1) depressive pseudodementia

2) metabolic problems

3) medication side effects

4) infections

5) dementia b/c of structural lesions

what is the most common type of dementia?

alzheimers

is dementia increasing in the population?

yes, elderly population growing so more old people = more dementia

hydrocephalus

water on the brain — enlargement of ventricles with CSF

• crushes brain tissue causing variety of symptoms

microcephaly — what is it and what issues can it lead to

essentially super small brain — can lead to seizures, developmental delay, intellectual disability, problems with movement and balance, feeding problems, hearing loss, and vision problems

anencephaly

born with no brain — individuals usually die upon birth

what connects the brain to the spinal cord?

medulla (goes through pons first)

the medulla is a part of the….

brainstem

order of communication amongst diff types of neurons in the brain?

sensory neurons (get info) —> interneurons (makes sense of it) —> motor neurons (create movement)

• motor neurons go to effector cells in body

sensory neurons — function, monitors what?

receives information from environment (touch, pain, temperature, light) and relays it to the central nervous system

• monitors conditions important to bodily homeostasis of blood pH and o2 levels

interneurons — function

associates sensory and motor activity in CNS — makes sense of all the information collected, and does computational stuff to work out what the information is conveying (what does the body need?)

motor neurons — function

comes out from brain/spinal cord and sends signals from these places to the muscles — allows mvmt!

what are the different ways you can cut up the brain?

1) sagittal

2) coronal

3) horizontal

sagittal plane of brain

divides into left and right sections

coronal plane of brain

dorsal ventral split (essentially like sliced into front vs back sides)

horizontal plane of brain

divided into top and bottom — straight through the middle horizontally

central nervous system composed of?

brain + spinal cord

peripheral nervous system composed of?

nerves and ganglia

nervous system coordinates… and also forms…

movement, touch, pain, senses

• also forms emotions, thoughts, consciousness

how does the spinal cord convey info from the brain to the PNS?

spinal nerves

nerves

neurons send info to spinal cord/brain through these — tough/long strands of tissue w/ neurons

effector cells

the cells in glands/muscles that receive signals from motor neurons

spinal cord basic organization

bone surrounding spinal cord to protect the fragile tissue, and spinal nerves stem out from the middle

each vertebrate contains how many clumps of nerves? what are the names of each one and their function?

2 clumps

1) dorsal (back) clump receives sensory information

2) ventral (front) clump sends signals to muscles

different sections of the spinal cord (4)

1) cervical

2) thoracic

3) lumbar

4) sacral regions

cervical part of the spinal cord

top 8 segments that innervate back of head, neck, shoulders and arms

thoracic part of the spinal cord

12 segments below cervical region that innervate thorax and upper abdomen

lumbar part of the spinal cord

5 segments below thoracic region that innervate pelvic girdle and legs

sacral region of the spinal cord

5 segments below lumbar region that innervate urogenital and perianal structures + back of legs

dermatomes

regions of skin that a specific spinal nerve innervates

• horizontal slice across body

  • ex) c2 corresponds to the 2nd cervical nerve

what nerves innervate the face? how many are there?

12 cranial nerves (comes out of the brain)

where do cranial nerves originate mainly?

medulla

locked in syndrome — what is it, what does it result from, damages, what part of the body is usually damaged?

neurological disorder that results in complete paralysis of voluntary muscles except eye mvmt

• results from brain injury, strokes, diseases destroying the myelin sheath, or medication overdose

• medulla

individuals with locked in syndrome

conscious with thinking/reasoning but unable to speak/move

• communication can be possible with possible blinking eye mvmt

jean dominique bauby

man who experienced a stroke and suffered locked in syndrome — only able to blink with left eye

• able to write a book by blinking out the letters

how does injecting evans blue into the blood indicate that the brain doesn’t come into contact with blood?

evans blue will dye all other organs but brains remain in similar condition to the control brain w/o dye in the blood

why does blood permeate the brain?

provides oxygen, glucose and removes waste products

why does blood not come in contact with the brain?

brain is sensitive to changes (pH, o2, chemicals), and blood fluctuates dramatically so it would be harmful

• also infections would be able to reach the brain and kill neurons — which cant be regenerated

cerebrospinal fluid

fluid bathing the brain, and is separated from blood via blood brain barrier

blood brain barrier — what is it formed by? what is the purpose? can antibiotics cross?

formed by cells in brain capillaries (astrocytes cells form tight junctions that prevent things from move)

• stops infections/toxins/drugs from reaching brain

• antibiotics too large to cross BBB

why is it difficult to develop drugs for brain disorders?

large molecules don’t cross bbb easily (most drugs (BACE inhibitors) that can treat the pathologies cannot get into brain)

what can cross the BBB and what drugs does this apply to?

small molecules (like oxygen) /LIPID SOLUBLE molecules

• applies to barbiturates (sleeping pills), antidepressants

central canal of spinal cord + ventricles of brain — describe them

hollow & filled with cerebrospinal fluid (150 mL)

how is csf made? what is its function?

made by filtering from the blood (area in ventricles takes fluid away from blood)

• cushions brain/cord

do our brains float in csf? what would happen if they didnt?

yes — neutrally buoyant — w/o csf and buoyancy it would crush itself b/c of density

lumbar punctures — what happens, what is it used for, where is it done and are there complications?

csf can be drawn from spinal column to diagnose disease (cancer, meningitis, or markers for other diseases like alzheimers (certain proteins can indicate this disease)

• also used for delivery of anesthesia to reach cns

  • needle inserted between L3/L4 or L4/L5

  • complications are rare but headaches can be caused

what problem of eukaryotic cells do organelles solve?

euka cells relatively large so it’s difficult to properly diffuse molecules across entire cell, so organelles break up the volume

advantages of compartmentalization in euka cells (2)

1) separating incompatible chemical reactions

2) increasing efficiency of these chem reactions

nucleus — structure & function, what does it produce and where?

double membraned nuclear envelope surrounding it + nucleolus

• function : info storage/processing, containing chromosomes, and ribosomal RNA (rRNA) synthesis (in nucleolus)

rough endoplasmic reticulum — structure & function, continuous with what? what is its interior called?

network of tubes/sacs studded with ribosomes, with an LUMEN interior — rough ER is continuous with nuclear envelope

• protein synthesis (in ribosomes) (MAIN)

• modification occurs in lumen (for secretion or membrane use)

smooth endoplasmic reticulum — structure & function— what is stored here? what is made & broken down here?

no ribosomes

• enzymes make fatty acids/phospholipids + break down poisonous lipids

• reservoir of Calcium ions

golgi apparatus — structure & function, what carries things to this organelle?

series of stacked flat sacs called cisternae

• processes, sorts, ships proteins synthesized in rough er

• vesicles carry materials to and from here

ribosomes — structure & function, are they membrane bound? where are they found?

non membranous - not technically organelles either… w/ large + small subunit w/ RNA and protein — can be attached to rough er or in cytosol floating

• protein synthesis

lysosome— structure & function, how many membranes? in animal or plant cells?

single membrane bound w/ digestive enzymes — in animal cells

• digestion + waste processing

tay sachs — malfunction in what organelle

malfunction in lysosome, results in waste buildup in the brain/neurons

mitochondria — structure & function, how many membranes? has its own ___ and makes its own ____?

two membranes, inner membrane folded into sac like cristae, solution inside cristae = mitochondrial matrix. organelle has own DNA + manufactures own ribosomes

• atp production (energy)

cytoskeleton— structure & function

holds cell tgth, gives it shape/stability

• aids in cell movement and transports materials

• organizes cell and other structures

plasma membrane— structure & function

double layer of phospholipids (amphipathic — hydrophilic heads and hydrophobic tails) that separates outside and inside of cell

• has a bunch of channels/receptors/proteins that regulate things + receive signals

• allows passage of oxygen, nutrients, and waste

animal movements are triggered by electrical signals conducted by…

neurons

neurons — what do they do, how do they do it, and how do muscles respond?

nerve cells transmitting electrical signals in communication — plasma membranes have voltage

• muscles respond to signals by contracting

describe the anatomy of a neuron

CELL BODY : contains organelles

DENDRITES : branched extensions connected to cell body that RECEIVE electrical signals from other neurons

AXON : extension that TRANSMITS signals to other cells at synapses

AXON HILLOCK : axon + cell body junction — where the action potential is generated

• synapse not a part of the neuron but is the gap between axon and another cell

synaptic terminal — what is it and what happens here?

where axon passes info across the synapse using neurotransmitters

is the plasma membrane of the neuron permeable to charged ions? if not, how do they get charged ions across?

impermeable — uses channels and receptors of proteins that let ions over

why are charged ions important to the function of the neuron?

provides electrical energy through flow of charged ions = able to rapidly signal

electrical potential/voltage — when is it present in a neuron?

diff in charge between 2 points

• present in neuron when two sides of plasma membrane do not balance e/o

membrane potential

when electrical potential exists on either side, separation of these charges = membrane potential

Na/K ATPase — how does it work and where are each ion’s concentrations higher?

imports 3 Na+ ions from inside of the cell to outside, using ATP, and then transporting 2 K+ ions from out to in

• conc of K+ higher inside, conc of Na+ higher outside cell

  • ATPase changes shape during the course of this

info is transmitted from a _____ cell to a ______ cell

presynaptic (neuron), postsynaptic (neuron, muscle, gland cell)

what are most neurons nourished/insulated by?

glia

diff types of glia (5)

1) astrocytes

2) ependymal

3) microglia

4) oligodendrocytes

5) schwann cells

astrocytes — how do they support neurons? are they restricted to PNS/CNS or are they in both?

support neurons by giving appropriate chem environment for signaling + form BBB

• restricted to CNS, with a star like appearance

ependymal cells

circulate cerebrospinal fluid

microglia

protects nervous system from microorganisms

oligodendrocytes — cns or pns

forms myelin sheaths around axons in CNS

schwann cells — cns or pns

forms myelin sheaths around axons in PNS

which glia share the same function but diff neuron location?

oligodendrocytes + schwann cells

brain tumors — what are they? what are the two most common types? do they occur on glia or neurons? how can secondary tumors arise?

results from uncontrolled cell division and ends in a mass (malignant (cancer) or benign(non-cancer))

• most are on glia b/c they can divide, but neurons cannot

• main types : gliomas, meningiomas

• secondary ones arise from malignant tumors originating in other parts and metastasizing

during action potential a _______ (inflow/outflow) of sodium ions is followed by an _______ (inflow/outflow) of potassium ions

inflow; outflow

resting potential

membrane potential of a neuron not sending signals

describe the general charges of the outside vs inside of the cell membrane?

outside is more positive, inside more negative

at resting potential what are the concentrations of K+ and Na+ like?

K+ = low outside, high inside

Na+ = high outside, low inside

what maintains the concentration gradients? is it powered by anything?

sodium potassium ATPase — uses ATP

what do the gradients represent?

chemical potential energy

describe the workings of the sodium potassium pump

1) 3 Na+ binds to pump —> atp used to change shape of protein = 3 Na+ released to outside

2) new shape = 2 K+ bind and phosphate group detaches = shape changes back to get 2 K+ inside cell

• causes net negative charge for inside cell b/c releasing more positive charges than gaining

is a majority of the neuron energy utilized by the Na-K pump?

yes

what is the resting membrane potential #?

-70 mv

name the 3 important ion channels for neurons

1) potassium channel

2) sodium channel

3) calcium channel

• all voltage gated

how do voltage gated ion channels open?

opens when depolarization (membrane becomes less negative) occurs

voltage gated potassium channel — purpose? does it open slowly or quickly? depolarization or polarization?

restores membrane potential following depolarization (makes membrane negative again) — opens slowly

• releases potassium to the outside

voltage gated sodium channel — does it open slowly or quickly? depolarization or polarization?

depolarizes membrane (more positive) during action potentials — opens rapidly

• Na+ into cell

voltage gated calcium channels

opens when membrane depolarizes ( near end of axon) — important for synaptic release

• lets calcium INTO cell