Exam 2 Flashcards
fertilization
- occurs when sperm enters egg and they fuse together
- series of steps that leads to a zygote
zygote
- a set of multiple cells that double during each round of division
- zygotic period (few days long) is the early stage of the embryonic period
- zygote is an embryo
- zygote cells can become any cell
gastrula
- multiple divisions of zygote lead to gastrula
- hollow cup-shaped structure with 3 layers of cells (ectoderm, endoderm, mesoderm)
3 layers of gastrula
- ectoderm
- endoderm
- mesoderm
ectoderm
becomes nervous system and brain
mesoderm
- includes notochord
- includes somites (nerves that come out of spinal cord)
notochord
sends signals to the ectoderm to transform into nervous system
steps from ectoderm to nervous system/brain
- ectoderm has neural plate
- notochord sends neurotrophins to initiate neural folding
- neural plate folds creating neural groove
- neural crest cells fuse together creating the neural tube from the neural groove
- neural tube stretches and zippers up at posterior and anterior ends
- the neural tube elongates to create the spinal cord and the brain
forebrain
- prosencephalon
- made up of cortex, basal ganglia, limbic system
midbrain
mesencephalon
hindbrain
- rhombencephalon
- made up of cerebellum, pons, medulla
neurogenesis
- creation of new neurons that fill cortical layers that cause the cortex to undergo rapid growth
- occurs in ventricular zone (lining of ventricles)
cortex
- contains 6 layers
- neurons radiate from ventricular zone outwards to fill out cortical layers by riding on radial glial cells
- radial glial cells must be made and extend to the top of the cortex; neurons that are created use the radial glial cells as a scaffold to climb up and integrate themselves into cortical layers
- cortex layers lower down are thicker
process outgrowth
growth of axons and dendrites
synaptogenesis
formation of synapse extensions emerge from growth cones at the tips of axons and dendrites
synaptic pruning
- synapses are lost and myelination occurs, increasing efficiency of neuronal communication
- leads to reduction of cortical thickness over time (loss of dendrites and cell death)
growth cone
- extension of a developing neuron
- growth cone connects to target forming a synapse and if enough stimulation a larger synapse will occur
filopodia
- tips of growth cone
- make synapses onto dendritic spines
- after growth cone meets target, filopodia makes direct contact
- can retract into lamopodia and extend in different directions
chemoattractants
chemicals that attract lamopodia/filopodia and tell them to grow in their direction
chemorepellants
chemicals that repel growth cones/filopodia and tell them not to grow in their direction
neuronal migration
- filopodia extend and find targets to synapse with
- chemoattractants and chemorepellants direct filopodia
- this process occurs during initial development of NS as seen in neural tube and spinal cord development
- this continues to occur throughout development as shown by cortical development
neurotrophins
- can increase/decrease synaptic pruning
- neurons compete for neurotrophins that the target cells make, and without enough neurotrophins, the neurons die
- help maintain synapses
brain derived neurotrophic factor (BDNF)
- neurotrophin
- supports neuronal survival
- can increase synaptogenesis
- shown to be important in preventing depression
- necessary for inhibiting anxiety
- loss of BDNF can result in shrinking of hippocampus
nerve growth factor (NGF)
- neurotrophin
- affects growth of neurons
schizophrenia
- abnormal prefrontal cortical development
- impairs working memory
- during early adulthood brain goes through synaptic pruning/myelination increase, which can cause onset of schizophrenia
working memory
- the ability to hold information in mind, it’s like concentrating
- working memory deficits in schizophrenics is likely due to the abnormal function of the prefrontal cortex
DISC1
- gene associated with schizophrenia
- DISC1 is important in neuronal migration during early cortical development and plays a crucial role in neuronal communication
- the mutation causes neurons to fill cortical layers incorrectly
evolution
- occurs when there is a change of gene frequency within a population over time
- the change in genes occurs when the next generation inherits genes from their parents
genotype
the set of genes an organism has
phenotype
the physical features of an organism
mutation
error in DNA replication
sex genetic shuffling
introducing new gene combination to offspring
gene flow
when a set of genes is taken from one geographical location to another
genetic drift
when a set of genes is spread throughout most of the population as compared to other sets of genes
natural selection
- a process by which an organism with certain genes that make them better adjusted to the environment have greater chance of surviving, reproducing, and increasing their gene transmission with greater frequency
- relies on:
- variation
- differential reproduction
- heredity
Darwin’s hypothesis
- reproduction will increase a population rapidly unless factors limit it
- individuals of a species are not identical
- some variation is inherited
- not all offspring survive to reproduce
evolution of the brain
- shows size changes both in specific regions and overall
- size of each brain structure is highly correlated with total brain size
- rate of increase in some brain areas can differ between small and large brains
costs and benefits to a large brain
- long gestation period
- prolonged dependence on parents
- high metabolic cost
- complex genes are vulnerable to mutation
social brain hypothesis
- suggests a larger brain is needed to maintain social relationships between similar individuals
- primates show a correlation between clique size and size of the cortex relative to overall brain size
adaptive advantages of a large brain
- increased survival
- ability for group interaction in humans
- innovative behavior, use of tools, and social learning in primates
classification
species genus family order class phylum kingdom domain
“Dear King Philip Came Over For Good Soup”
very similar genomes can produce different brains
- a few crucial genes can have a great effect on development
- small changes in DNA can alter the timing and location of gene expression
5 mechanisms of gene expression
- mutation
- gene flow
- genetic drift
- sex genetic shuffling
- natural selection
evolutionary increase in brain size
- differences in brain size and structure can be due to behavioral adaptation
- novel or strategic food-seeking behavior is correlated with larger brain size
- animals who depend on hearing, vision, or memory for their food develop larger related brain structures
what do hormones do?
- sleep regulation
- fight or flight response
- pheromones
- anger
- water retention
hormones
- secreted chemicals that are carried throughout the bloodstream
- all hormones begin in hypothalamus
- endocrine cells release hormones
- blood brain barrier helps with hormone regulation
- BBB allows some molecules in and blocks others
- hormones made outside the brain can be blocked or allowed in by the BBB
- only hormones made outside the brain can affect the brain if they pass the BBB
endocrine system
- hypothalamus, pineal gland, pituitary gland (NEUROENDOCRINE)
- adrenal gland (over kidneys; adrenaline)
- thyroid gland (surrounds trachea)
- gonads
- pancreas
- gut
anterior pituitary gland
- ACTH
- controls adrenal cortex and steroid hormone release
- TSH
- increases thyroid hormone release
- FSH
- stimulates egg-containing follicles or sperm production
- LH
- stimulates follicles to form the corpora lutea
posterior pituitary gland
- oxytocin
- involved in reproductive and parenting behavior; also in uterine contraction and the milk letdown reflex
- vasopressin
- important for water retention and increasing blood pressure
capillaries
take hormones to target sites
neuroendocrine axes
- hypothalamic-pituitary-thyroid axis
- hypothalamic-pituitary-adrenal axis
- hypothalamic-pituitary-gonadal axis
cortex of adrenal gland
produces adrenal steroids
medulla of adrenal gland
produces adrenal amine hormones
hypothalamic-pituitary-adrenal axis
- nor/epinephrine made in adrenal medulla is taken into brain by glucose
- glucose released during F or F response
- nor/epinephrine releases glucose into bloodstream
- therefore NE/E enhances attention and increases learning and constricts the blood vesicles to gut and helps send blood to brain and muscles
chronic stress results in…
depression, anxiety, and PTSD
hypothalamic-pituitary-gonadal axis
functions:
females –> FSH and LH result in ovulation
males –> FSH and LH result in sperm production
- release of estrogen/testosterone directly affect the brain, beyond hypothalamus
- estrogen increases neurogenesis (critical in episodic memory)
- testosterone may have neuroprotective effect and help against development of Alzheimer’s
cyclic adenosine monophosphate (cAMP)
second messenger that enhances the transmission of GPCR activation; slower than ionotropic receptor activation
blood brain barrier (BBB)
- testosterone passes the BBB
- allows for fat soluble compounds, like certain steroids, to freely cross the BBB
- estradiol can also pass the BBB
- estradiol is bound to protein a- Fetoprotein
- a- Fetoprotein blocks estradiol from entering the BBB
lordosis reflex
a female rodent will display this reflexive behavior during the late stages of the ovulation cycle
when male puts paws on hind legs of female she arches her back
estrogen and progesterone turn on circuit
stimuli of male rodent placing paws on hind legs of female —> activates circuit —> ventromedial hypothalamus —> periaqueductal gray —> medullary reticular formation —> reticulospinal tract —> spinal cord L1-L6
hyperthyroid activity
- weight reduction, but normal appetite
- weakness and tiredness
- anxiety
- increased feeling of heat and sweatiness
hypothyroid activity
- tiredness
- depression
- weight gain
- hair loss
- reduced attention
F-actin
helps filopodia crawl
neurocrine communication
synaptic transmission
endocrine communication
endocrine cell releases hormone into bloodstream and hormone leaves bloodstream for target cell
neuroendocrine communication
synaptic transmission and hormone is released from neuron into bloodstream and leaves to go to target cell
protein hormone action
hormone binds to receptor and on other side of membrane G proteins are released which in turn release cAMP which cascades and transmits the message of the hormone
steroid hormone action
steroid hormone passes membrane and binds to steroid receptor and enters nucleus to bind to DNA so that some gene products increase production and some decrease production
microtubules
microtubules in neck of growth cone help push growth cones forcefully forward
how hypothalamus sends signals to pituitary
through parventricular nucleus and supraoptic nucleus
hypothalamic-pituitary-thyroid axis
- thyroid is essential for keeping metabolism at optimal levels
- overproduction or underproduction of thyroid hormones could cause:
- hyperthalamic activity
- hypothalamic activity
neurotrophic factor
- a target-derived chemical that acts as if it “feeds” certain neurons to help them survive
- innervating neurons that don’t get enough neurotrophic factor die off
