Chp. 10 Flashcards
Cillary muscles
Controls shape of lens to refract light in mammals and birds
A class of interneurons in the retina that receive info from rods & cones and pass them along to retinal ganglion cells
Bipolar cells
Class of cells in retina whose interneurons form optic nerve
Ganglion cells
Specialized retinal neurons that contact both the receptor cells and the bipolar cells
Horizontal cells
Uses rods, works in dim light
Scotopic system
Uses cones that permit color vision
Photopic system
Photon
A quantum of electromagnetic light in the range of wavelengths we call light
The central portion of our vision packed with the most photoreceptors and therefore the center of our gaze
fovea
Range fractionation
Cell specialize in specific ranges of light intensity
photo pigment in eye that splits into two
rhodopsin = opsin & retinal
Region of retina devoid of receptor cells because ganglion cell axons and blood vessels exit the eye ball there
optic disk
Cones vs. rods
Rods packed about 20 degrees on other side of the fovea,
Part of schotatic system.
Many rods are linked to one ganglion cell so high sensitivity but low acuity
Neurons inhibit their neighbors to enhance borders
Lateral inhibition
Part of the thalamus that receives info from the optic track and sends it to visual areas in the occipital cortex
lateral geniculate nucleus
Axons that start in the lateral geniculate nucleus and terminate in the primary visual cortex of the occipital lobe
Optic radiations
Visual cortex outside of the primary visual cortex, V2, V4 and the inferior temporal area
Extrastriate cortex
Respond best to an edge or a bar that has a particular width, edge and orientation
Simple cortical cells
A model of pattern analysis that emphasizes Fourier analysis of visual stimuli
Spatial-frequency filter model
Textures, illusionary contours
What features does area V2 respond to?
Concentric, radial stimuli and sinusoidal frequency gradings
What does area V4 respond to?
What area responds to motion
Area V5 or the medial temporal area
A region of cortex in which one eye or the other provides a greater degree of synaptic input
Ocular dominance column
A slab of visual cortex, about 0.5 mm wide, in which the neurons of all layers respond preferentially to one eye
Ocular dominance slab
The point at which two optic nerves meet
Optic Chiasm
Non-preferred stimulus
A stimulus that falls within a cell’s receptive field, but only affects its firing rate a little bit, if at al
Anti-preferred Stimulus
The stimulus that inhibits a neuron the most.
Visuotopic map
Each hemisphere of V1 contains topographic map of the contralateral hemifield
Organization of Lateral Geniculate Nucleus
Composed of six layers – ipsilateral eye: 2,3,5 – contralateral eye: 1,4,6
• Layers 1 & 2 are called “magnocellular” due to their large cell bodies
• Layers 3-6 are called “parvocellular” due to their small cell bodies
How do On-center bipolar cell function?
INHIBITED by glutamate (via a metabotropic glutamate receptor) so they become depolarized (disinhibited) when light hits the photoreceptor
How do Off-center bipolar cells function?
EXCITED by glutamate so they become hyperpolarized (less excited) when light hits the photoreceptor
How does amplitude work?
Propagation of small displacements of air molecules vs. large displacements
Equation of pitch
P = 1/frequency
Eardrum sci name
Tympanic membrane
Ossicles- names and functions
Malleus- hammer
Incus - anvil
Strapes- taps against soft membrane in the cochlea wall called the oval window
Condition where patients can perceive light and movement
They cannot verbally report if a visual object is shown, but if asked where the object is they may guess the object’s location better than expected by chance.
Cortical blindness
Unable to attend to the visual field contralateral from the lesion (e.g. ignore left side)
- Eat food only on right side of plane
- Dress/groom only one side of their body
Hemineglect
Brain regions involved in where pathway
Ventral stream
- Medial temporal area (also called v5)
- PP is the posterior parietal area (behind the primary somatosensory cortex in the parietal lobe)
Brain regions involved in what pathway
V4 is associational visual cortex lying near the border of occipital & temporal cortex
– IT is the inferior temporal cortex
Brain area that integrates sensory inputs and directed motor pathways for spatial cognition
Parietal Cortex
Term for the overall pattern of movement in the visual field
Optic flow
Types of optic flow
Translational
Radial
Rotational
Peri-Stimulus Time Histograms (PSTHs)
A peristimulustime histogram is a graph that shows how a neuron responds to a stimulus
• The x-axis of the graph is usually time, with time zero being the moment when a stimulus is turned on
• The y-axis is the response of the neuron, often measure by firing rate (spikes per unit time)
Organization of the medial temporal
MST neurons that respond to translational motion are directionally tuned
• Each MST cell prefers to respond to translational motion in one preferred direction
• Unlike V1 complex cells, MST cell have large receptive fields and respond to any moving stimulus, not just an oriented bar
• MST is topographically organized into directional columns
Face Blindness
Prosopagnosia
External ear
pinna
The ___________ transfer the force of the tympanic membrane’s vibration into vibrations of the membrane of the oval window, sending waves of vibration into the fluid that fills the cochlea
ossicles
Tympanic reflex
there are two muscles (tensor tympani and stapedius) that can damp the vibrations of the middle ear in response to loud sounds, to protect the ear from damage and adjust the gain of hearing
What is the purpose of the round window in the ear?
provides a “release valve” for increases in cochlear fluid pressure that occur when the oval window vibrates
What is the primary functional structure in the inner ear?
The bony labyrinth filled with endolymph
Parts of the bony labyrinth
- The semicircular canals contain the vestibular organs which sense head motion and position
- The cochlea contains hearing organ that senses sound vibration
What is the cochlea and what are its major divisions?
- bony tube rolled up like a snail shell
-The cocheais subdivided into three parallel canals: scalavestibuli,
scalamedia,
scalatympani - separated from scala media by a soft flexible membrane called the basilar membrane
-When the oval window vibrates and sends waves of fluid pressure into the cochlea, the basilar membrane vibrates as well
Organ that sits atop the basilar membrane and contains hairs
organ of the Corti
Sterocilia
hair-like protrusions that transduce mechanical movements into nerve signals
On each hair cell, the tips of different stereocilia are joined to one another by tiny protein strands called _________
tiplinks
Tallest sterocillia
kinocilium
What concentration gradients are different for sterocilia
potassium gradients
What happens to sterocilia when they bend towards the kinocilium and what are the effects of that
Opening the K+ channels produces a graded receptor potential that DEPOLARIZES the hair cell! Why? Because the concentration gradient for K+ is high outside and low inside of the sterocilia
Do hair cells fire action potentials?
Hair cells do NOT fire action potentials!!!!! Depolarization of the somatic compartment opens voltage gated calcium channels, which triggers neurotransmitter release from the base of the hair cell
otoacoustic emissions
sound generated from the inner ear
How is the basilar membrane organized?
The basilar membrane is tonotopically organized, meaning that different parts of the basilar membrane vibrate in response to different sound frequencies • High frequencies vibrate the basilar membrane near its base, whereas low frequencies cause vibrations near the apex
What are spiral ganglion cell?
contains the cell bodies of 1st order bipolar sensory neurons that form the auditory nerve
What are the two parts of the bony labyrinth and what are there functions?
The cochlea - contains sound sensing organs
semicircular canals - contain vestibular organs
Three parallel canals in the cochlea
scala vestibuli
scala media
scala tympani
What is the basilar membrane
The scala tympani is separated from the scala media by a soft flexible membrane called the basilar membrane
Is the relationship between the brain and ear unidirectional or bidirectional and why?
bidirectional because the ear is very sensitive and the brain has to tune its sensitivity based on the ambient amplitude of the stimuli
What is the tectorial membrane?
potassium-rich Gelatin like substance that the top of the steriocillia are embedded in
What happens to the steriocillia when they are bent towards the kinocilium?
mechanically gated K+ channels open, the cell depolarizes, produces a graded potential, Depolarization of the somatic compartment opens voltage gated calcium channels, triggers neurotransmitter release from the base of the hair cell, The neurotransmitter binds to receptors on the afferent vestibular or cochlear nerve
Area of skin innervated by a single spinal neuron
Dermatome
5 sectional of spine + areas they cover
Cervical- arms and back of head Thoracic - back and stomach Lumbar - lower back and front of legs Sacral - buttocks and back of legs Coccygeal - pelvis and groin
Which area of somatosensation enters brain through cranial instead of spinal neurons
Facial somatosensation info
Name of cells that carry info from spinal cord to body and vise versa
Dorsal roots - carry info into spinal cord
Ventral roots - relay commands from spine to muscles
How many pairs of spinal neurons are there
31
What are the two main divisions of grey matter in the spinal cord and what types of neurons to they contain?
Dorsal Horn (contains sensory interneurons) – Ventral Horn (contains motor neurons)
What are the two main ascending tracks in the spinal cord and what information to they relay?
-Dorsal columns relay touch and
proprioceptive information to the brain
– Anterolateral (or spinothalamic) tract relays
pain and temperature information to the brain
What are generator potentials and what causes them?
Stretching of cell membranes (discriminative touch) opens mechanically gated sodium channels and causes excitatory potentials called generator potentials
What are the four main discriminative touch mechanoreceptors and what stimuli do they respond to?
Pacinian Corpuscle - pressure + vibration
Meissner’s Corpuscle - light touch
Merkel’s discs - light touch
Ruffini endings - pressure + vibrations
How are the receptive fields of the four main mechanoreceptors in discriminative touch characterized and how fast do they each adapt to stimuli?
Pacinian Corpuscle - fast, large, vague
Meissner’s Corpuscle - fast, small + sharp
Merkel’s discs - slow, small + sharp
Ruffini endings - slow, large + vague
What stimuli do free nerve endings record and how are their axons (somatosensory afferents) characterized?
temp + pain, unmyleneated, thin fiber (C)
What kind of axon do touch receptors use?
A beta - Second thickest, myelinated
What kind of sensation is relayed by the thickest axon?
Propioception in muscle fibers uses A alpha axons (thick but myelinaded)
What are the two kinds of propioceptors?
-muscle spindle organs (found in muscle) - detect muscle stretch
-golgi tendon organs (found in ligaments)
sense joint angle and position
How does the brain tell the difference between light and firm touches?
Different sensory neurons have different intensity thresholds (“range fractionation”)
What brain regions would process sensory information from the right side of the body?
The dorsal horn -> medulla -> left thalamus -> somatosensory cortex
How is the somatosensory cortex organized?
Forms a somatotopic map of the contralateral side of the body
What region of the brain processes whisker sensation in rodents?
barrel cortex
What kind of receptive fields do neurons in the somatosensory cotex have?
Center-surround (excitatory) center, inhibitory surround
Three main types of nociceptor
-Cool methol receptor - activated by methol, dull pain, low temperatures
-transient vanniloid receptor) is activated by
medium temperatures (and capsaicin!)
- transient receptor potential type M3
is activated by high temperatures
What type of axon do the three nocicpetors use?
CMR1 - c-fibers
TRPV1 - c-fibers
TRPM3 - a - delta fibers
What kind of animal spreads capsaicin seeds and why?
Birds do because their vanniloid receptors are NOT sensitive to capsaicin
What are the three behavioral responses to nocioception and what part of the nervous system regulates each one?
spinal cord - withdrawal
brainstem - innate escape reflexes and distress vocalizations
thalamus & cortex - learned escape + high level coping
What area of the brain processes rejection and nocioception (in addition to the somatosensory cortex) and what neural system is it part of?
The anterior cingulate cortex which is part of the limbic system
How does descending pain modulation work?
The frontal cortex or periaqueductal gray excite raphe 5 HT (serotonin producing) neurons and they activate inhibitory interneurons in the spinal chord that shut down pain before it reaches the brain
- Sometimes by releasing endogenous opioids
Term for sensing of
odor molecules from the outside air; this
occurs during inspiratory breathing
Orthonasal olfaction
Term for sensing of
odor molecules from the mouth; this
occurs during expiratory breathing
Retronasal olfaction
Sensory organ of smell
olfactory epithelium
Name and structure of hair like receptors that odor molecules bind to
cilia - dendrites of bipolar olfactory sensory neurons
Pathway from olfactory epithelium to brain
bipolar olfactory sensory neurons of the same receptor type converge on glomerulus in the olfactory bulb which synapse with mitrial cells
What growth property makes taste receptors and olfactory receptor neurons special
Stem cells in the taste buds and olfactory epithelium respecivly divide to replace both receptors all through a person’s life
What brain regions are involved in 3rd order odor processing and what are their functions?
Amygdala - attaches emotional valence
Prepyriform cortex - distinguishes odors
Hypothalamus - coordinates hormone response
What brain regions are involved in POST 3rd order odor processing and what are their functions?
medial dorsal thalamus - signals other parts of the brain
-Insular cortex, which integrates olfaction, taste, and
somatosensation to encode flavors
-Orbitofrontal cortex, which allows odors to influence
decisions and behavior
-Entorhinal cortex and hippocampus, which help to weave odors into our episodic memories of past experiences
What organ detects pheromones and do humans have one?
Veronasal organ, humans do not have a functional one
How do newly generated olfactory receptors know which glomerulus to synapse with
olfactory ensheathing cells (OECs) send chemical signals to facilitate appropriate axon growth
Name for a substance that can be tasted
tastant
what are taste buds made of?
hollow sacs with walls made out
of taste receptor cells and holes called taste pores
tastants are dissolved into the saliva and ooze into the grooves surrounding tiny bumps on the tongue called ___________
papillae
How do taste receptors identify tastants?
Each taste receptor cell extends hair-like cilia into the taste bud sac, and each cilium’s membrane expresses one of five types of taste receptor
What are the 5 basic tastes and what do they detect?
Salty taste cells are specialized for detecting
sodium, and to a lesser extent other salts
• Sour taste cells are specialized for detecting
acids
• Sweet taste cells are specialized for
detecting sugars
• Bitter taste cells are specialized for detecting
noxious and potentially toxic substances
• Umami taste cells are specialized for
detecting the savoy flavor of protein rich
foods
How does the salt receptor work?
taste cells express a sodium channel called ENaC (with three subunits called α, β, γ); salt on the tongue causes the extracellular sodium concentration to increase, resulting in an inward chemical force that pushes sodium into the taste cell to depolarize it
How does the sour receptor work?
Sour taste cells express a protein called
PKD2L1 that is thought to function as a
non-specific cation channel (that is, a
channel that is permeable to multiple
cations) which is gated by protons
(hydrogen ions) which are found in acidic
compounds
How do the umami, sweet and bitter taste cells work?
umami has two g-protein receptors : - a metabotropic glutamate receptor (activated by the flavor enhancer monosodium glutamate, or MSG) -A g-protein receptor composed from T1R1 and T1R3 subunits, which is activated by amino acids
Sweet taste cells express a g- protein receptor composed from
T1R2 and T1R3 subunits
Bitter taste cells express a g- protein receptor composed from
~30 different members of the
T2R receptor family
Names of the three cranial nerves that carry taste to brain
- Facial (VII)
- Glossopharyngeal (IX)
- Vagus (X)
Region in thalamus where taste is processed
ventral medial nucleus
two parts of the gustatory cortex
- Anterior insula
• Frontal Operculum
What parts of the brain generates and relays our sense of flavor?
Insular cortex
Which taste cells express the T1R1 and T1R3 subunits?
Umami
Which taste cells express the T1R2 and T1R3 subunits?
Sweet
Which taste cells express the T2R family?
bitter
Name for brain signals that express hunger?
Orexigenic signals
Name for brain signals that suppress hunger?
Anorexigenic signals
Which part of the hypothalamus is orexigenic?
Lateral hypothalamus
Which part of the hypothalamus is anorexigenic?
Ventromedial hypothalamus
What is the name of the pancreatic hormone that converts glycogen back into glucose?
glucagon
Substance synthesized from sugar and deposited in adipose tissue?
glycogen
Scientific name for fatty tissue?
adipose tissue
Three main types of satiety signals?
- Leptin produced by adipose tissue when they are full of glycogen
- PYY hormone made by full intestines
- Insulin produced by pancreas to convert glucose into energy
Two functions of insulin and one caveat
- Helps convert glucose to glycogen to create adipose tissue
- Essential for normal function of glucose transporters that bring glucose into cells in the body
- Caveat: Not needed for glucose transport in the brain
hormone produced by the stomach
when it is empty that acts as a hunger signal
Ghrelin
Region of the hypothalamus that signals to the lateral hypothalamalus and the ventromedial hypothalamus
Arcuate nucleus
Neurons in the arcuate nucleus that act on the lateral hypothalamus
POMC/CART neurons
Name of hormone released by POMC/CART neurons in the arcuate nucleus that inhibits the orexigenic neurons in the lateral hypothalamus
a-melanocyte-stimulating hormone
Neurons in the arcuate nucleus that stimulate appetite
AgRP/NPY neurons
How does AgRP and NPY stimulate appetite
-NPY inhibits the anorexigenic (appetite
suppressing) neurons in the paraventricular
nucleus (PVN)
-AgRP blocks the effects of a-MSH in LH
by acting as a competitive antagonist at its
receptor
Which neurons in the arcuate nucleus are affected by ghrelin and PYY
appetite-enhancing AgRP and NPY are excited by ghrelin and inhibited by PYY, insulin and leptin
Which hormones affect POMC/CART neurons?
- Leptin and insulin excite them.
- Grehlin and PYY have no effect on them
Do obese humans have high levels or leptin or low levels of leptin? why?
high levels because they have more adipose cells and they are leptin insensitive
What class of receptor do salty and sour taste cells express
Ionotropic
The outer segments of the rod cell contains
thin layers of membrane called _______
and these contain the light sensors
lamellae
The base of the rod contains ______________
vesicles full of glutamate that can be
released onto other neurons
Just beneath the outer segment of a rod is an area
filled with _________
mitochondria and other cellular machinery
The nucleus of the rod is between the ____________ and the __________
outer segment made of lamellae and the base full of glutamate vesicles
what is the resting membrane
potential of a photoreceptor in the dark?
-35 mV
When it is dark photoreceptors are ________ polarized and release a lot of __________
They are partially polarized and they release a lot of glutamate
How does a flash of light affect a photoreceptor and what is the name for it?
When a very brief flash of light occurs, it is
followed by a slow hyperpolarization lasting
about 100-200 ms; this is called the receptor
potential
The photoreceptor contains ligand gated _____channels that are _____ in the dark
ligand gated sodium channels that are open in the dark
How does light hyperpolarize photoreceptors?
It prevents cGMP (cyclic guanosine monophosphate) that holds the ligand-gated sodium channels open from binding to the sodium channel
The lamellae membranes of photoreceptors are studded with special light-sensitive proteins called ______
opsins
The opsin in rods is called __________, the opsin in cones is called ___________
rhodopsin, cone opsin
Opsins bind to a molecule called ______
retinal
What happens when light hits the opsin?
The retinal breaks away exposing a a site that can bind to a g-protein complex called transducin
How does transducin binding to opsin close sodium channels?
-The binding triggers an activated subunit of the transducin protein to bind to another protein complex called cGMP phosphodiesterase (PDE).
- When transducin binds to it, cGMP PDE begins breaking down cGMP by converting it to a molecule called 5’-GMP
-cGMP is a ligand that binds internally to open sodium channels?, but 5`-GMP cannot
bind to the sodium channels!
• Consequently, activation of cGMP PDE causes the sodium channels to close
Why do different light wavelengths affect different cones?
Each cone receptor expresses a specific cone opsin that responds best to light of a specific wavelength (S, M, or L)
why are men more likely to be colorblind (dichromates)?
-M and L opsin genes are on the X chromosome, so females have TWO chances to
inherit a good version of these cone opsins
-M is the most frequent mutated cone type
Which are the first neurons in the
phototransduction pathway that fire
action potentials?
Ganglion cells
Which neurons are excited by glutamate in photransduction pathway?
Off-center bipolar cells
On-center ganglion cells
Off-center ganglion cells
What mechanism creates on-center off-surround receptive fields and off-center, on-surround
Lateral inhibition by horizontal cells that synapse with photoreceptors and bipolar cells
Where do axons that carry information from each eye’s lateral hemifield cross the midline?
The optic disk
Axons that carry information from each eye’s medial hemifield are processed by which side of the brain?
The ipsilateral side
The RIGHT side of the visual field is processed in which side of the brain?
the left
Why is v1 known as the striate cortex?
-Projections from the two eyes are segregated into
a striped pattern when the cortical surface is
viewed from above
• The stripes are referred to as ocular dominance
columns
Complex cell receptive field
- orientation selective but not position selective.
- Can perceive motion and sometimes a specific direction of motion is preferred and the opposite direction is anti-preferred
When does optic flow detection begin
retina ganglion cells
What structures do the cochlear nucleus on each side of your brain project to and which side do they project to?
Both cochlear nuclei project to both the left and the right superior olive
What design in the brain enables auditory localization?
Sound travels at a fixed velocity and so arrives at each ear at slightly different times. The bilateral project of both cochlear nuclei to each superior olives, allows the brain to detect latency and so identify the location of the sound’s origin
What structure does the superior olive project to and how is that structure organized?
The inferior colliculus which retains the tonotopic map of sound frequencies.
It is located in the tectum (roof) of the midbrain
Where does the inferior colliculus project to and where is it located?
The medial geniculate nucleus located in the thalamus
Where in the brain does the primary auditory cortex reside?
lateral sulcus
Where do the higher auditory areas reside?
superior temporal gyrus
Names for rotation on the three axis
z = yaw, x = roll, y = pitch
What organ in the semicircular canal of the bony labyrinth detects head tilt and linear acceleration in the horizontal plane (x + y)
Utricle
What organ in the semicircular canal of the bony labyrinth detects head tilt and linear acceleration in the vertical plane (z axis)
saccule
Structure of saccula
Top layer - crust of calcium carbonate called otoliths
Middle layer - otolithic membrane which steriocillia are buried in
Bottom layer - cell bodies of hair cells
Hair cells in the utricle are depolarized by what?
backwards head tilts or forward acceleration
Hair cells in the utricle are hyperpolarized by what?
forward head tilts or by backwards acceleration
What is the head tilt illusion and how does it work?
Pilots taking off are accelerating vertically and tilting their head backwards.
They cannot tell how much of each is going on so they sometimes point the nose of the plane down to compensate
Name for animal that generates its own heat
endotherm
In response to cold stress, neuroendocrine cells in the ________ of the hypothalamus produce __________
preopticarea (POA), thyrotropinreleasing hormone(TRH)
What are the 3 physiological responses of cold stress
- metabolism of brown fat (which burns energy and produces heat, just like your car engine cell phone battery can get hot when it burns energy quickly)
– muscle shivering (which also generates heat by burning energy) –
vasoconstriction (blood circulation dissipates heat, to shrinking the diameter of blood vessels prevents heat loss)
3 Sympathetic Responses to Heat Stress
1) accelerated respiration
• 2) perspiration
• 3) vasodialation(expanding the diameter of blood vessles) to dissipate heat
TRH is released into the blood from hypothalamic neuron axons, and travels a short distance through the vessels of the ________ to the ___________
hypophysealportal system, anterior pituitary gland
Neuroendocrine cells in the _______ release a specific tropic hormone called _________ into the bloodstream
anterior pituitary, thyroid stimulating hormone(TSH)
TSH travels through the bloodstream to the _______, where it triggers release of thyroid hormones that increase metabolic rate and sympathetic nervous activity
thyroid gland (in the neck)
How does the hypothalamus initiate a cold response in the body?
- The hypothalamus releases thyrotropinreleasing hormone(TRH)
- The hypothalamus sends axons directly to the spinal cord, where they activate ganglia of the sympathetic nervous system to generate these same heating responses
After how many weeks does an embryo become a fetus?
10
When does the embryo develop in to three layers? (in days)
18
3 Layers of an embryo
Endoderm grows into the stomach, colon,
liver, pancreas, bladder, trachea, lungs,
intestines.
- Mesoderm grows into muscle, bone,
cartilage, fat tissue, blood vessels
- Ectoderm has two parts: surface
ectoderm (blue) and neural plate (brown).
At ___days, the neural plate
differentiates into two parts
20
At 20 days, the neural plate
differentiates into which two parts?
- Neural crest grows into the peripheral nervous system. - Neural groove will become the neural tube, which grows into the central nervous system
The neural tube develops into which three subdivisions
the forebrain (prosencephalon), the midbrain (mesencephalon) and the hindbrain (rhombencephalon)
The forebrain then develops into
telencephalon (cerebrum)
and the diencephalon (thalamus, hypothalamus, pineal gland).
A birth defect that occurs in about 1 in 1500 babies when the neural tube fails to close at the caudal end of the ectoderm.
Spina Bifida
Spina bifida is reduced in likelihood by which supplement?
folic acid (vitamin b)
What happens in the neurogenesis stage of embryonic development?
• Cells of neural tube divide to produce neurons from nonneuronal cells. • The region of the neural tube that surround the canal is called the ventricular zone • The outer regions of the neural tube (farthest from the central canal) are called the marginal zone • Only cells in the ventricular zone divide to create new cells
What happens in the cell migration stage of embryonic development?
• The new cells migrate from the ventricular zone to enter the marginal zone, where they will form the brain and spinal cord • The central canal becomes the fluid filled cerebral ventricles of the brain and the central canal of the spinal cord.
What happens in the cell differentiation of embryonic development?
• Each cell differentiates to become a particular
type of neuron or glial cell
What factors determine neuronal cell fate?
1) Time of birth: When a cell is born in the ventricular zone
(early or late) can determine its fate by dictating where it will
end up in the brain; cells born early end up in deep layers (near
ventricles) and cells born later end up in superficial layers
(near brain surface).
– 2) Cell-to-cell signaling: Cells can communicate with one
another to influence one another’s fate during development.
• Neurotrophic factors can also influence cell
differentiation
What happens in the synapto genesis stage of neuronal development?
● Neurons grow in size by extending growth cones outward from their cell bodies, which form the long processes that will become the neuron’s dendrites and axons. ● The growth cone exchanges chemical signals with other cells that help to tell it where to go, which cells to form synapses on
What is the growth pattern of the brain over a person’s lifespan?
- Brain quadruples in weight in first 5 years of life
- Reaches zenith in adolescence
- Begins to shrink post adolescence
Names of 3 types of neurotrophic factors
Nerve growth factor (NGF): substance that affects
growth of neurons in spinal ganglia and ganglia of the
sympathetic nervous system
Brain-derived neurotrophic factor (BDNF) and other
members of the neurotrophin family are similar to
NGF
What is stage 5 of neuronal development and what kind of cell is particularly affected?
Neuronal cell death, spinal motor
neurons die off during weeks 10-30
What is stage 6 of neuronal development and what peaks at age 5?
Synapse Rearrangement & Pruning
Number of synapses
Skills that have a critical period early in life
– Language
– Stereo vision
– Social skills
– Virtuosity (musical instruments, sports, etc.)
What causes down syndrome?
Inheritance of extra chromosome 21?
What causes fragile x syndrome?
Fragile X syndrome results from inheriting
extra trinucleotide repeats, repetitions
of the same three nucleotides, in a
particular gene.
Which chromosome causes schizophrenia and what are its neurodevelopmental effects of a mutated version?
A c4 mutation causes excess synaptic pruning in the prefrontal cortex
Three main output pathways from hypothalamus
1) Controls hormone release by the pituitary gland
2) Sends projections to autonomic ganglia in
brainstem & spinal cord
3) Sends projections to multiple regions throughout
the brain
There are two divisions of the autonomic
nervous system that “oppose” one another
for control of body systems:
– The sympathetic division promotes active states that often involve increased metabolism and consumption of the body’s energy – The parasympathetic division promotes resting states that often involve decreased metabolism an conservation of the body’s energy
Neural pathways in the autonomic nervous
system transmit signals mainly via two
neurotransmitters:
– Noradrenalin (especially in sympathetic)
– Acetylcholine (especially in parasympathetic)
Sympathetic trunk
Chains together sympathetic ganglia
Layers of the spinal cord
Dura mater, pia mater, arachnoid mater
Where are parasympathetic nerves found?
The neurons of the parasympathetic nervous system are often found in ganglia that lie near the organs that the ganglia regulate. -Most stem directly from brain rather than the spinal cord
What are the neurological and endocrinal steps in the cold response system?
- Neuroendrocrine cells in the preoptic area of the Hypothalamus releases Thyrotroptin releasing hormone into the hypophyseal portal system.
- The anterior pituitary gland is stimulated to produce more thyroid stimulating hormone
- Thyroid stimulating hormone travels through the bloodstream where it signals the thyroid to produce more thyroid hormones that increase metabolic rate and sympathetic nervous system activity
- The hypothalamus also sends axons directly to the spinal cord, where they activate ganglia of the sympathetic nervous system to generate these same heating responses
Three main osmoreceptors
the subfornicalorgan
organum vasculosumlaminae terminalis (OVLT), and third ventricle
What were the Battleboro rats unable to produce and what was the impact of that deficiency?
-The rat’s kidneys excreted all water as waste and returned no water to the blood (zero water retention via kidneys)
• To make up for this, the rats must drink 70% of their body weight in water every day to hydrate their blood via other routes
Partner preference can be simulated in ________ with the neurotransmitter ________
prairie vole, vassopressin
Which species does vasopressin not cause pair preference in?
montane voles
Steps in the Hypothalamic-Pituitary-Adrenal (HPA) Axis
-Neuroendocrine cells in the pervoventricular nucleus (PV) of the hypothalamus produce Corticotropin releasing hormone
-CRH is released into the blood from hypothalamic neuron axons, and travels a short distance through the vessels of the hypophysealportal systemto the anterior pituitary gland
-Neuroendocrine cells in the anterior pituitary release a specific tropic hormone called adrenocorticotropic hormone(ACTH) into the bloodstream
ACTH travels through the bloodstream to the adrenal glands (on top of each kidney), where it triggers release of glucocorticoid hormones (such as cortisol in humans) that increase metabolic rate and sympathetic nervous activity
Two types of adrenal hormone response to stress
-The adrenal amine response – Fast acting – Triggers the adrenal medulla(inner core) to release amine hormones such as adrenalin and noradrenalin – Activated by projections from hypothalamus to sympathetic ganglia
• The adrenal steroid response – Slower acting – Triggers the adrenal cortex(outer shell) to release steroid hormones, specifically glucocorticoids – Activated by ACTH release from anterior pituitary (which is itself triggered by release of CRH from hypothalamus)
How do steroid hormone acts on target cells throughout the body?
- Steroid hormones act slowly. Their receptors are found within target cells.
- When steroid-receptor complexes form, they alter protein production, producing long-lasting effects.
- The steroid-receptor complex binds to DNA and acts as a transcription factor— controlling gene expression
What does the FKBP5 gene control and what happens when it is mutated?
- There is a “chaperone protein” called FKBP5 that helps the streroid hormone/receptor complex translocate to the nucleus
- Some people have random genetic mutations of the FKBP5 gene, which put them at higher risk for PTSD
Alternate name for posterior pituitary gland
Neurohypophysis
Alternate name for anterior pituitary gland
Adenohypophysis
Muscles that can damp vibrations in the middle ear with loud sounds to protect the middle ear
Tympanic reflex
Two muscles involved in the tympanic reflex
Tensor tampani, stapedius
What are the functions of the inner hair cells versus the outer hair cells
Outer hair cells adjust sensitivity
Inner hair cells vibrate in tune with sound
