Lecture 2: organization of nervous system Flashcards
anterior
in front = towards the face
posterior
behind = towards the back
superior
above = towards the head
medial
towards the midline
inferior
below = towards the feet
lateral
towards the edges
dorsal
toward the top of the brain or the back of spinal cord
ventral
toward the bottom of the brain or the front of spinal cord
rostral
toward the front of the brain or the top of spinal cord
caudal
toward the back of the brain or the bottom of spinal cord
ipsilateral
structures on the same side
contralateral
structures on the opposite side
How is mammalian nervous system divided?
CNS = central nervous system and PNS = peripheral nervous system
midsaggital plane
splitting brain into equal right and left halves
horizontal plane
parallel to the ground = split brain into dorsal and ventral parts
coronal plane
perpendicular to ground and saggital plane = split brain into anterior and posterior parts
What comprises central nervous system?
cerebrum, cerebellum, brainstem, spinal cord = encased in bone
cerebrum
mostly rostral; largest part of the brain; spilts in the middle to form 2 cerebral hemispheres seperated by deep saggital fissure => right cerebral hemisphere receives signals and controls the left side of the body
cerebellum
little brain! behind cerebrum; primarily movement control centre -> extensive connections with cerebrum and spinal cord; in contrast to hemispheres -> left side of cerebellum controls movement of left side of the body
brain stem
stalk from which cerebrum and cerebellum sprout; rely of information from cerebrum -> spinal cord and cerebellum (and vice versa); regulates vital functions (breathing, body temperature) = the most primitive and important part of mammalian brain
What if you damage brain stem?
you die
spinal cord
encased in bony vertebral column = attached to brain stem; major conduit of information from skin, joints, muscles
What if you damage spinal cord?
there is lack of feeling in the skin and paralysis of muscles caudal to the injury -> technically muscles CAN function, but cannot be controlled by the brain
dorsal root
axons bring information into spinal cord
ventral root
axons carry information away from spinal cord
peripheral nervous system
can be further divided into somatic and visceral subdivisions; sticks out from the bony structure
somatic PNS
muscles under voluntary control -> somatic motor axons which command muscle contraction, derive from motor neurons in the ventral spinal cord => cell bodies of motor neurons lie within CNS but their axons mostly in PNS; information from sensory axons enters via dorsal root
visceral PNS
involuntary, automatic nervous system -> neurons which innervate internal organs, blood vessels, glands; visceral sensory axons bring infromation about visceral function to CNS -> visceral motor fibres command contraction and relaxation of muscles (intestines, blood vessels), rate of cardiac muscle contraction and secretory function of various glands
afferent axons
carry information TOWARDS sth
efferent axons
carry information FROM sth
corticospinal tract
pyramidal tract, is the major neuronal pathway providing voluntary motor function
spinothalamic tract
sensory tract that carries pain, temperature, touch, and pressure from our skin to the somatosensory area of the thalamus
meninges
3 membranes that envelop the brain and spinal cord = dura mater, archnoid membrane, pia mater
dura mater
'’hard mother’’ -> dura -> leather-like consistency, tough, inelastic bag surrounding brain and spinal cord
archnoid membrane
under dura mater, spider like extensions
subdural hematoma
if blood vessels passing through dura are ruptured, blood can collect in space between dura amter and achnoid membrane
pia mater
'’gentle mother’’; thinnest one, follows all blood vessels into the brain -> adheres closely to the brain
cerebrospinal fluid
subarchnoid space between archnoid mater and pia mater -> brain floats in CSF -> PROTECTION
ventricular system
cerebrospinal fluid-filled caverns and canals inside the brain
choroid plexus
specialized tissue in ventricles that secretes CSF
flow of CSF
cerebrum -> brain stem core -> subarachnoid space -> spacial structures called arachnoid vili absorb CSF
glymphatic system
excretes waste in CSF - pumping
hydrocephallus
'’water head’’ -> when flow of CSF from choroid plexus through ventricular system to subarachnoid space is impaired = swelling of ventricles
CLARITY
new method of visualization of deep brain structures without slicing the brain; soaking brain is solution which replaces light-absorbing lipids with water-soluble gel that turns brain transparent -> transparent brain illuminated to evoke fluorescence from neurons that express green fluorescent protein
computed tomography
computarized x-ray imaging procedure in which narrow beam of x-rays is aimed at patient and quickly rotated around the body, producing signals that are processed by the machine’s computer to generate cross-sectional images (slices)
magnetic resonance imaging
more detailed thatn CT, does not require x-ray radiation, brain slices at any plane desired -> uses information about how hydrogen atoms in the brain respond to perturbations of strong magnetic field -> electromagnetic signals emitted by atoms are detected by array of sensors around the head
How MRI works?
makes proton jump from LOW-energy to HIGH-energy states -> resonant frequency= frequency at which protons absorb energy -> when radio signal is turned off some protons return to low-energy state -> the stronger the signal, the more hydrogen atoms between poles of the magnet
high frequency signals (MRI)
hydrogen atoms near strong side of magnet
low frequency signals (MRI)
hydrogen atoms near weak side of magnet
diffusion tensor imaging
visualization of large bundles of axons in the brain, comparing positions of hydrogen atoms in water molecules at discrete time intervals -> diffusion of water in brain measured -> water diffuses much more readily alongside axon membranes than across them, and this difference can be used to detect axon bundles that connect different brain regions
what are functional brain imagining methods?
PET, fMRI
positron emission tomography (PET)
radioactive solution containing atoms that emit positrons (positively charged electrons) is introduced into bloodstream -> positrons (emitted wherever blood goes) interact with electrons to produce photons of electromagnetic radiation -> location of positron-emitting atoms are found by detectors that pick up the photons => measurement of metabolic activity in the brain
What are PET limitations?
low spatial resolution, takes several minutes to obtain scan, radiation
fMRI - functional magnetic resonance imaging
oxyhemoglobin (oxygenated from hemoglobin in the blood) has magnetic resonance different from deoxyhemoglobin (hemoglobin that has donated its oxygen) - more active brain regions receive more blood with oxygen -> measuring ration of oxyhemoglobin to deoxyhemoglobin
What are fMRI advantages?
good spatial and temporal resolution, noninvasie
important cranial nerves
olfactory tract and optic nerve = purely sensory (do not move your eyes or nose), vagus (nerve 10, carries parasymapthetic nervous system)
spinal nerves
extend from spinal cordl; innervate skin, joints, mucles
dorsal root ganglia
contain cell bodies of peripheral sensory neurons
from what part of spinal cord come motor nerves?
ventral part of spinal column
from what part of spinal cord come sensory nerves?
from back of spinal column
autonomic nervous system
visceral PNS - sympathetic and parasympathetic division - innervates smooth muscles of internal organs, blood vessels, glands etc
sympathetic division
prepares body for action -> pupil dilation, broncholidation (breathing), cardiac acceleration (heart pumping), inhibition of digestion, piloerection, stimulation of glucose release, systematic vasoconstriction (bringing blood pressure up)
parasympathetic division
prepares body for digestion and rest -> pupil constriction, brochoconstriction, cardiac deceleration, stimulation of digestion, salivation, lacrimation (tears flow), intestinal vasodilation
what are autonomic measures?
measures of emotion, stress and arousal; ECG, skin conductance, plethysmography, respiration
electrocardiogram (ECG)
electrical activity of the heart
skin conductance/resistance
based on change in conductance by swear secretion
plethysmography
vascular flow = blood flow
respiration
respiratory effort, air exchange
gray matter
collection of neruonal cell bodies in CNS; when freshly dissected brain is cut open, neurons appear gray
cortex
any collection of neurons that form thin sheet, usually brain surface; example: cerebral cortex
nucleus
clearly distinguishable mass of neurons, usually deep in the brain; example: lateral geniculare nucleus
substantia
group of related neurons within the brain but usually with less distinct borders than those of nuclei; example: substantia nigra
locus
small, well-defined group of cells; example: locus coeruleus
ganglion
collection of neurons in PNS; example: dorsal root ganglion
the only ganglion in CNS
basal ganglia = lying deep within cerebrum that control movement
nerve
bundle of axons in PNS
What is the only nerve of CNS?
optic nerve
white matter
collection of CNS axons, when dissected brain is cut open, axons apear white
tract
collection of CNS axons having common site of origin and common destination; example: corticospinal tract
bundle
collection of axons that run together but do not necessarily have the same origin and destination; example: forebrain bundle
capsule
collection of axons that connect cerebrum with the brain stem; example: internal capsule
commisure
any collection of axons that connect one side of the brain to other side
lemniscus
tract that meanders through brain like ribbon, example: medial lemniscus
With what layers does embryo begin?
endoderm (internal organs), mesoderm (bones and muscles), ectoderm (nervous system and skin)
What is neurulation?
process by which neural plate becomes neural tube
How does neurulation occur?
From ectoderm, neural plate is formed (17 days after conception), when neural groove starts to appear and folds until canal is formed. This canal forms neural tube.
Why is neural tube important?
Because the entire central nervous system develops from its walls. Moreover, eventually tube will become ventricular system.
What is neural crest?
some neural ectoderm is pinched off and comes to lie lateral to neural tube -> it eventually becomes peripheral nervous system
mesoderm
internal body organized into segments will develop into bones and muscles -> forms prominent buldges on either sides of neural tube called somites = from them spinal column and skeletal muscles develop (somatic motor neurons)
endoderm
gut + internal organs
differentiation
process by which structures become more complex and functionally specialized -> first time it happens when 3 swellings develop = primary vesicles of neural tube
what are 3 primary vesicles of neural tube?
prosencephalon (forebrain); mesencephalon (midbrain); rhombencephalon (hidbrain)
anencephaly
degeneration of forebrain - fatal
spina bifida
failureof posterior neural tube to close
differentiation of presencephalon (forebrain)
telencephalon (sides) and diencephalon (middle part)
telencephalon
forms cerebral hemispheres, olfactory bulbs, basal telencephalon
diencephalon
thalamus and hypothalamus
what are major gray matter systems?
cerebral cortex, thalamus, hypothalamus, basal ganglia, olfactory bulbes
cerebral cortex
analyzes sensory input and commands motor output
thalamus
sensory gateway of the cortex (for every sense EXCEPT olfaction) -> important for regulation of attention -> reciprocally connected to cortex (through internal capsule), conveys sensory infromation from contralateral side of the body
hypothalamus
primitive behaviors (controls automatic and endocrine systems), super thermostat, also directs bodily responses via connections with pitutiary gland
basal ganglia
one of biggest subcortical nucleic group, selects motor outputs, motor impulse, development of habitual sensory-motor behaviors
olfactory bulbes
receive information from cells that sense chemicals in the nose and relay information caudally to part of cerebral cortex for further analysis
What are major white matter systems?
cortical axons -> corpus callosum internal and external capsule, anterior and posterior commisure
corpus callosum
forms axonal bridge that links cortical neurons of 2 cerebral hemispheres, crossing-over spot
internal and external capsule
cortical axons projecting to deep brain structures and periphery = links cortex with brain stem, particularly with thalamus
anterior and posterior commisure
interhemispheric connection to deep brain structures
differentiation of mesencephalon (midbrain)
tectum (=roof) and tegmentum (=covering); axons descend from cortex to brain stem and spinal cord
tectum
2 structures: superior colliculus (visual processing) and inferior colliculus (auditory processing) -> crude but fast reactions, life-saving situations
tegmentum
substantia nigra => dopamine production and red nucleus (control of voluntary movements)
cerebral aqueduct
in the middle (between tectum and tegmentum), CSF-filled
What happens if you damage corticospinal tract?
loss of voluntary movement in opposite side of the body
differentiation of rombencephalon (hindbrain)
cerebellum, pons, medulla oblongata
cerebellum
movement control -> receives massive axonal inputs from spinal cord (body position) and pons (intended movement goals)
What happens if you damage cerebellum?
uncoordinated, inaccurate movements
pons
switchboard connecting cerebral cortex to cerebellum
medulla oblongata
medullary pyramids; axons cross in medulla = explanation why there is contralateral body control in the brain -> it has sensory functions = axons bring information (auditory. touch, taste)
cochlear nuclei
audition; axons project to inferior colliculus
What does decussation mean?
crossing of axons from one side to other
locus coeruleus
synthesis of noreadrenaline
raphe nuclei
synthesis of serotonin
What will you see if you cut spinal cord?
gray matter has shape of butterfly => it is filled with CSF; whitish looking outer area indicates myelination; dorsal horn is located on upper part of butterfly’s wing (sensory inputs); intermediate zone = gray matter between horns; ventral horn is located on lower part of butterfly’s wing (sends information to other body parts)
What consists the ventricular system of the brain?
lateral ventricles, third ventricle, cerebral acqueduct, fourth ventricle
What are neurotransmitters modulating forebrain during development?
acetylcholine, histamine
What are neurotransmitters modulating midbrain during development?
dopamine
What are neurotransmitters modulating hindbrain during development?
noradrenalin, serotonin
What are main differences between human and mouse brain?
In humans, the expansion of cortex is evident = need for sulci, gyri and also there is curvature of NS axis. In rodents, brain is smooth and all vesicles are in linear position. Moreover, in rodents olfactory bulb is really big.
What is mainly added in expansion of the cortex?
connections
What are examples of curvature of NS axis?
hypothalamus under thalamus; midbrain, pons and cerebellum are under telencephalon, lateral ventricle has S-shape
limbic cortex
involved in our behavioural and emotional responses, especially when it comes to behaviours we need for survival: feeding, reproduction and caring for our young, and fight or flight responses
What are two gyri associated with limbic cortex?
gyrus cinguli and gyrus parahippocampus
amygdala
primary role in the processing of memory, decision-making, and emotional responses (including fear, anxiety, and aggression); lies at the edge of hippocampus
hippocampus
episodic memories, interesting stimuli, arousal, sea-horse shaped ->consists of cornu ammonis (CA1, CA2, CA3) and dentate gyrus
What is main difference between hippocampus in humans and rodents?
In humans, the hippocampus needed to be pushed down due to cortical expansion and curvature of NS axis
Why amygdala appears relatively bigger in rodents?
because there is less cortex
What basal ganglia consists of?
caudate nucleus, globus pallidus, putamen
