Biology Flashcards
Which cells produce myelin?
Oligodendrocytes- CNS, Schwann cells- PNS
Astrocytes
Nourish neurons and form blood-brain barrier (controls transmission of solutes from blood to brain)
Ependymal Cells
produce cerebrospinal fluid (shock absorber and brain support) in ventricles of brain
Microglia
phagocytic cells-ingest and break down waste/pathogens in CNS
Resting Potential
-70 mV, inside of neuron is negative
Equillibrium potential of Na and K
K= -90 mV, Na= 60 mV (balance between chemical concentration gradient and electrostatic forces)
What maintains concentration gradient in neurons
Na+/K+ ATPase- pumps K in and Na out
Axon Hillock importance
All inhibitory (hyperpolarization) and excitatory (depolarizing) signals adds up-summation– if cross threshold, AP triggered
Temporal summation
multiple signals integrated in short period of time
Spatial summation
additive effects based on time and location of signals- soma vs dendrite for example
Absolute refractory period
Absolutely no AP can occur (Na+ channels inactive)- depolarization time- unidirectional impulse propogation
Relative refractory period
AP can occur but requires greater than normal stimulation since hyperpolarization (Na+ channels deactivated)
Describe an AP for me please
Look at an image
Factors that affect the speed of action potential propogation
Increasing length- more resistence, slow conduction
High cross section area= fast propogation, less resistence (more significant than length)
Myelin- insulator- signal only propogates between nodes
Saltatory Conduction
Myelin- insulator- signal only propogates between each Node of Ranvier- saltatory conduction
How does increased intensity of signal affect AP
Doesn’t change potential difference of AP but increases frequency of firing AP
What triggers exocytosis of neurotransmitters?
AP reaches nerve terminal, voltage gated Ca+ channels open. High calcium concentration triggers exocytosis of neurotransmitters
Three mechanisms to remove neurotransmitters from synaptic cleft
Enzymes break it down- ACh (acetocholine)
Reuptake by preenzymatic neuron- serotonin (5-HT) dopamine (DA) , norepinephrine (NE)
Diffusion out of synaptic cleft- nitrous oxide (NO)
Afferent neurons
Sensory neurons- receptors to spinal cord/brain (ascend)
Efferent neurons
Motor neurons- spinal cord/brain to muscles/glands (exit)
Interneurons
Spinal cord/brain- involved in reflexes also
Supraspinal circuita
Information processing is sent to brain/brainstem for processing
White matter
Axons with myelin sheaths
Grey matter
cell bodies and dendrites
Relative location of white/grey matter in brain and spinal cord
Brain- white matter is deeper than grey
Spinal cord- white matter outside, grey matter inside
Four regions of spinal cord
cervical, thoraric, lumbar, sacral
dorsal root ganglia
cell bodies of sensory neurons- axons from sensory enter from dorsal side
somatic nervous system
sensory and motor neurons in skin, joints, muscles- voluntary (only one neuron from spinal cord to location)
autonomic nervous system
involuntary- regulates heartbeat, respiration, digestion, glandular secretion, regulates body temp (sweating)
contain two neurons in series from spinal cord- preganglionic (soma in CNS) and post ganglionic (axon hits target)
Sympathetic NS
stress-flight and flight- increase heart rate, slow digestion, increases blood glucose, dilate eyes, release epinephrine, orgasm, inhibits bladder contraction
Parasympathetic NS
conserve energy- rest and digest- reduce heart rate, increase peristalsis, constrict bronchi
Which neurotransmitter is used in parasympathetic responses
ACh- acetylcholine. Vagus nerve (cranial nerve 10) is responsible for much of innervation.
Reflex
internueron in spinal cord sends out response to info before signal reaches brain
Monosynaptic reflex arc
only one synapse- between sensory and motor neuron - knee jerk reflex- tap on patellar extends leg- response to potential injury
Polysynaptic reflex arc
At least one interneuron between sensory and motor neuron- ex. withdrawla reflex from like stepping on a nail, maintain balance is polysynaptic but monosynpatiic is moving away
What are organs of endocrine systems called and what are messengers
Glands and hormones (secreted in bloodstream)
Hormones- change gene expression or cellular functioning
Catecholamines and behavior
epinephrine, norepinephrine - fast onset, short lived, G-protein coupled receptors, adrenaline rush
(like peptide hormones)
Triiodothyroxine, thyroxine
thyroxine, triiodothyronine- long term metabolic regulation, slow onset, long duration, bind intracellularly
Compare/contrast peptide and steroid hormones- chemical precursor, location of receptor, mechanism of action, method of travel in bloodstream, speed of onset, duration of action
See notes
Direct hormone vs tropic hormone. Where do tropic hormones usually originate
Direct- acts directly on target tissue- like insulin
Tropic- acts through an intermediary- like GnRH and LH (stimulate production of another hormone, which actually acts on target).
Tropic originate in brain and anterior pituitary gland
Amino acid-derivative hormones
derived from one or two amino acids with modifications
catecholamines (epinephrine and norepinephrine) and thyroid hormones (triiodothyroxine, thyroxine)
Organs of Endocrine System- list and location
See notes for location Hypothalamus, pineal gland, pituitary gland (also called hypophysis) - brain Thyroid- neck anterior Parathyroid- neck posterior Adrenal gland- kidneys Pancreas Ovaries, testes
Kidneys, heart, thymus, gastrointestinal- also play a role in hormone production/release
Paracrine signaling
Cells that are near one another communicate through the release of chemical messengers (ligands that can diffuse through the space between the cells).
This type of signaling, in which cells communicate over relatively short distances, is known as paracrine signaling.
Axial vs appendicular skeleton:
- Axial= skull, vertebra, ribcage, hyoid bone
- Appendicular= lims, pectoral girdle, pelvis
How many of each type of vertebra?
- Cervical (7)
- Thoraric (12)
- Lumbar (5)
Bone marrow type
Located in spongy bone
Red= hemopoietic stem cells
Yellow= fat
Bone matrix- organic and inorganic components. Name of crystals formed.
Organic= collagen, glycoproteins, peptides
Inorganic= calcium, phosphate, hydroxide ions== harden together to form hydroxyapatite crystals
Sodium, magnesium, potassium also stored in bone
Penetrance
population parameter- proportion of individuals in a population carrying allele (with given genotype) who actually express phenotype
Huntington’s- sequence repeats expansion in gene
full penentrance- more than 40 sequence repeats= 100% of individuals with allele show phenotype
high penetrance- fewer sequence re[eats- most show phenotype
reduced, low, and nonpenetrance
Expressivity
individual parameter- varying phenotypes despite indentical genotypes
constant= all individuals with genotype express same phenotype
variable= individuals with same genotype show diff, phenotypes
Gene pool
all of the alleles that exist within a species. genetic variability essential
Silent mutation
change in nucleotide has no effect on final protein synthesized
usually wobble position mutation
Missense mutation
point mutation- results in change in amino acid
nonsense mutation
point mutation- results in stop codon instead of amino acid
Chromosomal mutations (list and describe the 5)
deletion (remove segment)
duplication (copy segments within same chromosome)
inversion (reverse segment)
insertion (segment moved from one chromosome to another)
translocation (segments swapped between two chromosomes)
deleterious mutation- inborn errors of metabolism
defects in genes for metabolsim like PKU- metabolizing AA phenylalanine
toxic metabolites accumulate- but can be treated at birth
genetic leakage
flow of genes between species-
hybrid offspring from individuals from different but closely related species
sometimes can not reproduce since odd number of chromosome but sometimes can- results in leakage
genetic drift
changes in composition of gene pool due to chance (random events that lead to loss of alleles)- more pronounced in smaller pops
extreme cases
- founder effect (small pop in reproductive isolation)
- bottlenecks
reduction in genetic diversity
inbreeding effects
encourages homozygosity- increases prevelance of homozygous dominant and recessive geneotypes
reduction in genetic diversity- inbreeding depression- reduced fitness in population
outbreeding, outcrossing
increased variation within gene pool, increased fitness
introduction of unrelated individuals into a group
test cross
unknown genotype crossed with homozygous recessive
heterozygous cross ratios to remember
monohybrid 3:1
dihybrid 9:3:3:1
recombination frwuqnecy
proportional to disantance between genes
likely to not be linked and be separated during crossing over with increeasing distance
linked= low recombination frequency
map units= 1% recobiation frquency
Hardy Weinberg Equillibrium conditions
large population= no genetic drift no mutations random mating no migration in or out all genes in population equally successful for reproduction
allele frequency
how often allele appears in population
Hardy weinberg equations
p+q=1
p^2 + 2pq + q^2=1
p^2= frequency of dominant genotype p= frequency of dom allele
2pq= frequency of heterozygous
q= frequency of recessive allele
Natural selection
chance variations exist between individuls and advantageous variation (increase fitness)= reproductive success
survival of fittest
neo-Darwinism/modern synthesis model and differential reproduction
when mutation or recombination resu;ts in change that is favorable, more likely to pass onto next generation— success is called differential reproduction
inclusive fitnesss
success is not only based on number of offspring, but also success in supporting offspring, ability of offsping to support others
surivival of offspring and relatives= appearance of genes later
Punctuated equillibrium
evolution is a very low process with intermittant bursts of rapid evolution
not just constant rate
Stabilizing selection
keep phenotypes in narrow range, excluding extreme (birth weight)
directional selection
moves average phenotype towards one extreme (antibiotic resistance)
disruptive selection
moves population towards two different phenotypes at extremes- can lead to speciation
facilitated by polymorphisms- naturally occuring differences
adaptive radiation
rapid emergence of multiple species from a common ancestor- each of which occupies own ecological niche (specific environment, resources, predators, role)
species
largest group of organisms capable of breeding to form fertile offspring
isolation= no longer able to interbreed= species
Prezygotic reproductive isolation
temporal (diff mating times), ecological isolation, behavioral isolation (diff mating calls, smells, etc), gametic isolation (intercourse can happen but no fertilization), reproductive isolation (incompatibility)
Post zygotic reproductive isolation
hybrid inviability- zygote not develop
hybrid sterility- 1st gen sterile
hybrid breakdown- 2nd gen sterile
Divergent evolution
two species sharing common ancestor become more different- different selection pressures (Y shaped)
Parallel evolution
two species sharing common ancestor evolve in similar ways due to similar selection pressures (pitchfork)
Convergent evolution
two species unrelated (no recent common ancestor) evolve to become more similar due to similar selection pressues (two sep lines meeting)
Molecular clock model
degree of difference in genome between species is related to amount of time since broke off from common ancestor
Positive control
ensure a change in dependant variable when expected. If testing an Alzheimers detection system, positive control= those already known to have AD
Negative control
ensure no change in dependant variable when expected. no AD patients if testing AD detection system
Cohort study
Observational
subjects sorted into groups based on differences in risk factors/exposures and then assessed at various intervals to determine number of subjects with a certain outcome in each grou[
Cross sectional study
observational
subjects categorized into diff groups at a single point in time
case control studies
observational
start by identifying number of subjects w or w/o a certain outcome and look backwards to determine how much subjects were exposed to a particular risk factor
Hill’s criteria
the more of these components exist for an observational study relationship, more likely it is that it is causal
temporality- exposure must happen before outcome
strength- variability in outcome explained by variability in exposure
dose-response relationship- as IV increases, so does response
consistency
plausibility
consideration of alternative explanation- ruled out
experiment (if can be performed)
specificity- change in outcome only made from change in IV
coherence- consistent with scientific knowledge
Types of biases
selection bias
detection bias (may screen obese patients more for diabetes for example- educated professionals who know relationship between two variables)
observation bias/Hawthorne effect- behavior of subjects altered because they know they are being studied (often take steps to improve healh)
Confounding error
incorrect relationship characterized
data analysis error, not bias
distortion that modifies the association between exposure and outcome
appearance of association when not there
morally relevant differences
differences between individuals that are considered an appropriate reason to treat them differently
age- organ transplant
population size impact of study
NOT race, sex orientation, wealth
