brain anatomy Flashcards
what is the nervous system made of
brain
spinal cord
nerves
ganglia
cognitive neuroscience
cognitive psychology + behaviour neuroscience
understanding the link between the brain and the mind. The ways in which the brain influences how people think, feel and act
role of the human nervous system
control the body’s response to stimuli - both external (react to things going on, on the outside) and internal (coming from you. ie/ an impulse)
contralateral
the opposite side
Ipsilateral
the same side
unilateral
the same side
bilateral
both sides of the brain
proximal
near
distal
far
CNS
encompasses the brain and spinal cord
PNS
comprises neural tissues beyond CNS
brain
receives and processes sensory info, initiates responses, stores, memories generates thougts and emotions
spinal cord
conducts signals to and from the brain, controls reflex activities
relays most sensory and motor info to and from brain
motor neurons
CNS to muscles and glands
send signal from the brain and spinal cord to muscles
involved in innervated muscles
sensory neurons
sensory organs to CNS
bring info to the CNS
ie/ touch receptors in fingether
somatic nervous system
controls voluntary movements
automatic nervous system
controls involuntary responses
sympathetic division
fight or flight
parasympathetic division
rest and digest
enteric division
digetive system
protection of the CNS
brain enclosed in skull
spinal column is enclosed within spinal cord
cerebrospinal fluid
cerebrospinal fluid
ventricles within the CNS contain CSF
the brain floats in CSF which acts as a cushion
nutrients from the blood reach nerve cells through CSF
maintains brains shape
cushion from damage
similar composition to blood minus blood cells - similar to plasma
functions: delivers nutrients, carries away waste, surround the CNS (cushioning and buyancy)
produced mainly in choroid plexus of lateral ventricles
subdivisions of the CNS
spinal cord
medulla
cerebellum
pons
midbrain
diencephalon
cerebral cortex
diencephalon
hypothalamus and thalamus
dorsal section of the spinal cord
receives sensory info
ventral section of spinal cord
conveys motor commands to muscles
receives input from brain and other regions of the spinal cord
medulla
directly superior to the spinal cord
contains many of the cell bodies of the 12 cranial nerves
where most of the motor fibers cross of to the other side of the body (contralateral)
controls vital reflexes such as respiration and heart rate
hours part of the reticular activating system
12 cranial nerves
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vesitibulocochlear
glossopharyngeal
vagus
spinal accessory
hypoglossal
cerebellum
regulates muscle tone and guides motor activity activity
damages results in disrupted balance, equilibrium, and inability to produce precise movement (motor control)
involved in motor learning
learning movements in a fluid way. ie/ golf swing - instead of doing it step by step
pons
acts as a connective bridge from the rest of the brain to the cerebellum
also a bridge between most of the cranial nerves and the brain
controls some types of eye movements and vestibular functions
info from the ears converge, is compared, helps with localization of sound
the midbrain
superior to the pons
contains the nuclei of the cells that form some of the cranial nerves
plays a role in orienting a person to certain sensory stimuli: inferior colliculus (auditory), superior colliculus (visual)
hypothalamus
controls behaviours that help the body satisfy its needs, allowing it to maintain homeostasis. (eating, drinking, temperature, circadian rythms)
does the via relationship to the hormonal system
links the nervous system to the endocrine system through the pituitary gland
secretes hormones and produces factors that regulate activity of additional brain regions that secrete hormones
thalamus
relay center for almost all sensory info coming into the cortex and almost all motor info leaving it
patterns of connections, both to and from the thalamus, are very specific allowing info to be reorganized as it travels from sensory regions to the brain or vice versa
cerebral cortex
primary role in functions such as object recognition, spatial processing and attention
divided into two physically separated halves, each called a cerebral hemisphere
primary motor cortex
the final exit point for neurons responsible for fine motor control of the body’s muscles
motor control and motor homunculus
motor control is contralateral
the map is inverted: dorsal cortex controls the bottom half or the body; ventral cortex controls the top half of the body
the map is distorted such that more cortex is devoted to those regions of the brain for which we have the finest motor control
primary sensory cortices
the first region in the cortex to receive info about a particular sensory modality
each primary cortex is specialized for initial processing, then relays on to other cortical areas
somatosensory cortex
receives info about tactile stimulation, proprioception, pressure and pain sensatios
info sent via two main routes.
what are the two main routes of the somatosensory cortex
dorsal regions of the spinal cord: pain, temperature, and crude tactile information
fine touch and proprioception info enter the spinal column and synapse at the medulla, where it crosses over
somatosensory homunculus
like the motor cortex, the map is distorted so that more brain tissue is devoted to bodily regions for which we have the most tactile receptors
primary visual cortex
when looking straight ahead, the info to the right of fixation (the right visual field) projects to the left half of the retinas of both eyes, and vice versa
destruction of the visual cortex results in an inability to perceive light-dark contrast
auditory cortex
processes pressure waves in the air
info received at the right ear projects to both left and right hemispheres and vice versa
the primary auditory cortex is tonotropic
- located in the superior portion of the posterior temporal lobe in an area called Heschl’s gyrus
olfactory bulb
a thin strand of neural tissue located directly below the frontal lobe
olfactory cortex
olfactory bulb
info is projected in two ways
- to the limbic system
- via the medial dorsal thalamus to orbitofrontal regions
the only sensory system where info is solely conveyed ipsilaterally
gustatory cortex
taste comes from taste bud receptors in the tongue and epiglottis
two major branches of info sent to the brain: the limbic system, the primary sensory cortex
located in the anterior portion of the insula
three distinct regions of the frontal lobe
primary motor region, premotor region and prefrontal cortex
frontal lobe
what makes people, people - it is what makes us who we are ie/ personality
associated with behaviour, emotional functioning, judgement, and decision making
damaged often associated with a change in personality
parietal lobe
integrating info from sensory modalities (these can be stores in memory)
about an individuals internal state with with info from the external sensory world
damage can cause alexia, agraphia and or apraxia
temporal lobe
memory
auditory processing
emotion
visual item recognition - damage can cause agnosia (modality specific)
subcortical
below the cerebral cortex
major subcortical systems
basal ganglia
limbic system
basal ganglia
important for motor control
consists of the caudate nucleus, putamen, globus pallidus, and nucleus accumbens
limbic system
a circuit including the amygdala, hypothalamus, cingulate cortex, anterior thalamus, mammillary body and hippocampus
each structure has its own distinct function
integrates and processes emotional info between various parts of the nervous system
two pathways of the olfactory system
- through olfactory tubercle, then thalamus and then to the orbitofrontal cortex. provides our conscious perception of smell
- go directly to the olfactory cortex and limbic system (bypassing the thalamus). helps discriminate odours, results in the connection between smell, memory and emotion
neurons
carry info from one place to another
a combination of electrical and chemical signals
glia
function as support cells
method od support varies based on glial cell subtype
dentritic tree/ dentrites
receives input from other cells
cell body/ soma
made up of the same structures common to all other eukaryotic cells
smooth and rough ER, golgi apparatus, mitochondria
makes proteins and enzymes to that allow cell function
axons
carries info to other cells
varies in length
glia in the CNS
astrocytes, oligodendrocytes, ependymal cells, radial and microglia
interneurons
associate sensory and motor activity in the CNS
in between
mostly located in the brain
astrocytes
maintenance and modifications of the chemical environment between neurons (specifically synapses)
influence communication between neurons by controlling neurotransmitter levels
maintenance of water and ion homeostasis
participation in the environment
contribution to the blood brain barrier
oligodendrocytes
generate and maintain myelin
ependymal cells
involved in creating CSF
form a membrane lining parts of the spinal cord and ventricles of the brain
radial glia
can generate neurons, astrocytes and oligodendrocytes (progenitor cell)
guide neurons into place during development
contribute to neuroplasticity
microglia
remove dead neurons, serve some nutritive needs of neurons and provide structural support - we start with a lot, have extra need to get rid of some as brain develops (only need so many connections)
serve some nutrition needs
protect against injury and disease
what are the PNS glia
satellite cells
schwann cells
satellite cells
regulates the chemical environment around the neurons
delivers nutrition to the neuron and absorbs toxins
schwann cells
myelinates neurons, PNS version of oligodendrites but they sit directly on the axon
one section of myelin
resting potential of neurons
-70 mV
steps of an action potential
- sodium channels open, NA+ rushes in , depolarization
- potassium channels open, K+ starts to leave cell
- sodium channels close
- potassium channels close
Action potentials
electrical signals are sent from the cell body down the axon
axon terminals make contact with dendrites of another neuron, but leave a tiny space called the synaptic cleft
action potentials cause the presynaptic neuron to release neurotransmitters into the cleft, which bind to (activate) receptors on the postsynaptic neurons
spatial summation
if three EPSPs arrive at three different parts of the dendrite, that may be enough to push the postsynaptic cell to threshold, triggering an action potential
any IPSPs that might arrive will counteract EPSP
temporal summation
even a single synapse may push the post synaptic cell to threshold if many APs arrive in quick succession, providing overlapping EPSPs
signals from the sam source
myelin
provides an insulating, fatty sheath to the axon of neurons
the larger the myelin sheath the greater the speed with which the electrical signal is propagated down the axon
control of timing is essential not only for motor skills and sensory processing but also for higher integrative functions, including cognition
variations in myelin (including internode length) allow for control of the timing of neural inputs, slowing or speeding AP propagation of some axons relative to other axons
node of ranvier
gaps between myelinated sections of an axon
unmyelinated
gates all along axon, signal has to travel the whole length, step by step
myelinated
signal can siip/slide down axon to the next node
gray matter
cell bodies and their dendrites
more outside
40 percent of the brain
serves to process info
fully develops once a person reaches their 20s
white matter
axons and their myelin sheaths
made up of bundles that cnnect various gray matter areas
highways in between
60 percent of the brain
allows communication between grey matter areas and other parts of the body
develops throughout 20s and peaks in middle age
involved in neuroplasticity
white matter tracts
connect parts of the brain by shuttling info between distinct brain regions
corpus callosum - most notable tract
superior longitudinal fasciculus
from: frontal
to: parietal/temporal
occipitofrontal fasciculus
from: occipital
to: frontal
uncinate fasciculus
from: frontal
to: anterior temporal
arcuate fasciculus
from: posterior temporal
to: frontal
cingulum
from: frontal
to: entorhinal cortex
inferior longitudinal fasciculus
from: occipital
to: temporal
vertical occipital fasciculus
from:occipital
to: parietal
steps of neural transmission
- AP reaches axon terminal
- calcium ion channels open allowing for calcium ions in
- calcium causes synaptic vesicles to release from microtubules
- synaptic vesicles fuse with axon membrane at release sites
- vesicles open, releasing neurotransmitters into synaptic cleft
- neurotransmitter binds with receptor
- vesicle material is recycles
- vesicles either return to neuron cell body via retrograde transport or are refilled at axon terminal
Excitatory postsynaptic potential
make the cell’s electric charge more positive
glutamate
has an excitatory effect
15-20 percent of synapses in CNS
too much can cause excitotoxicity which can lead to cell death
inhibitory postsynaptic potentials
make the cell’s electrical charge more negative
GABA
gamma aminobutyric acid
has an inhibitory effect
limits AP’s from firing
40 percent of all receptors in CNS
substances that reduce CNS activity bind to GABA receptors
cholinergic system
neurotransmitter acetylcholine
exicitatory effect on neuronal and mental functiong
plays a role in alertness and paying attention
serotonergic system
serotonin
influences variety of behaviours
many antidepressant medications are serotonin specific reuptake inhibitors
noradrenergic system
noradrenaline or noepinephrine
influences arousal and attention, also linked to both shorter-term and longer-term aspects or memory processing
dopaminergic system
dopamine
nigrostriatal
mesolimbic
mesocortical
nigrostriatal
important in motor control
mesolimbic
linked to reward-related control
mesocortical
influences a variety of mentail functions, including executive function, goal oriented behaviour and working memory
how do astrocytes regulate the environment of the synaptic cleft
they control the formation, maturation, and plasticity of synapses through a variety of secretory and contact-mediated signals
regulate extracellular concentrations of ions neurotransmitter and other molecules through uptake and recycling
when neurons fire APs they release potassium ions into extracellular space
they have high concentration of potassium channels which act as spatial buffers
they uptake potassium at sites of neuronal activity (mainly synapses) and release it at distant contacts with blood vessels
what is the point of having nodes
reboosts signal, since once it reaches its max it slows down
sometimes we want the signal to be slower
