lecture 4 - brain and cranial nerves part 1 Flashcards
brainstem includes (3)
medulla oblongata, pons, midbrain
main parts of the brain in categories (4)
brainstem
cerebelum
diencephalon
cerebrum
diencephalon (3)
thalamus, hypothalamus, epithalamus
cerebrum (1 = 4)
cerebral hemisphere
- cortex and lobes
- basal ganglia
- limbic system
- ventricles
brain is protected by (2)
cranial bones
cranial meninges
cranial meninges (3)
dura mater
arachnoid mater
pia mater
how does dura mater differ in brain to spinal cord (3)
brain
two layers
- periosteal - superficial
- meningeal - deep
layers are fused except when they separate to enclose venous sinuses
no epidural space around brian
3 extensions of dura mater
falx cerebri
falx cerebelli
tentorium cerebelli
falx cerebri
extension of dura mater
separates cerebral hemispheres (down the middle)
falx cerebelli
extension of dura mater
separates cerebellar hemispheres
tentorium cerebelli
extension of dura mater
separates cerebrum from cerebellum
how does blood flow to the brain
vai internal carotid and vertebral arteries
how does blood flow away from the brain
vai dural venous sinuses that drain into internal jugular veins
blood brain barrier function
protects brain cells by preventing harmful substances in blood from entering the brain
BBB components (3)
tight junctions - seal endothelial cells of brain capillaries
thick basement membrane - surround endothelial cells
astrocytes pressed against capillaries - secrete substances that allow selective passing of molecules from blood to neurons
what can cross teh BBB (3, with examples for each)
lipid soluble substances - alcohol, O2
water soluble substances - glucose
other substances like ions travel very slowly
what cannot cross the BBB/ damage it?
big molecules like proteins cant cross
trauma, inflammation, toxins can breakdown BBB
CSF, what is it?
colourless liquid that bathes the CNS
- composed of water, with a bunch of small things like O2, glucose, proteins etc
how much CSF do we have around the brain at a given time
80-150 ml
CSF functions (3)
mechanical protection - shock absorption
chemical protection - maintain optimal environment for neurons
circulation - medium for exchange of nutrients and waste between blood and nervous tissue
ventricles of the brain (4)
two lateral
third
fourth
all CSF filled
where are the two lateral ventricles located
in each hemisphere of the cerebrum
separated by septum pellucidum
septum pellucidum
separates the two lateral ventricles
where is the third ventricle located
along midline superior to hypothalamus, between left and right halves of the thalamus
where is the forth ventricle located
between the brainstem and cerebellum
interventricular foramen
space where lateral ventricles and third ventricle are connected
where is CSF produced
in the choroid plexuses, by ependymal cells
choroid plexuses
network of blood vessels and cells in ventricles where capillaries are covered in ependymal cells
ependymal cells secrete:
CSF via filtration of blood plasma
what forms the blood CSF barrier
ependymal cells joined by tight junctions surrounding capillaries + endothelial cells inside capillaries
circulation of CSF in detail (
- produced in plexus
(each plexus -> ventricle. eg, CSF produced in third ventricles plexus goes to 3rd ventricle) - flows down ventricles (lateral, 3, 4)
- subarachnoid space
- arachnoid villi of dural venous sinuses
- then to teh heart and lungs
- blood is then sent to the ventricles plexuses, and the process repeats
how is CSF reabsorbed
vai arachnoid granulations
- grape cluster like structure of arachnoid mater that penetrate dural venous sinuses
- 20ml /hour is taken up
hydrocephalus
accumulation of CSF in the brain if drainage is blocked (by tumor, inflammation, etc)
- in babies, this allows expension of the skull due to pressure inside, can cause damage to nervous tissue
- drain can be planted to let CSF flow to veins of the neck of abdomen
medulla oblongata contains
continuation of the spinal cord, so both ascending and descending tracts, and nuclei
integration centres for body function, reflexes, movement
pyramids
white matter form bulges on ventral surface of medulla oblongata
- large motor tracts that pass from cerebrum to cord (corticospinal)
- control voluntary movement of limbs and trunk
- decussate
decussation
crossing
how does decussation affect the brains control of the body
makes it so teh left half of the body is controled by the right side of the brain and vice versa
olives
contain interior olivary nucleus that receives input from cerebral cortex, midbrain, and cord. sends output to cerebellum
- give precision to movements,, controls proprioceptive signals
lateral to pyramids of the medulla oblongata (swelling thing)
nuclei of the medulla control many body functions including:
cardiovascular centre
respiratory centre
reflex centre
other smaller centers include, gustatory, vestibular (balance), and somatic sensation
pons is located
superior to medulla oblongata in the brainstem
pons “bridge” function
connects part of the brain via tracts
- connects right and left sides of cerebellum
the pons contains (
- nuclei that help control breathing
- vestibular nuclei (balance)
- nuclei for cranial nerves 5-8
midbrain is also known as
mesencephalon
mesencephalon extends from what to what
pons to diencephalon
mesencephalon contains
cerebral aqueduct which connects third and forth ventricles
sensory + motor tracts, and auditory/visual nuclei
anterior portion of the midbrain contains: (1)
cerebral peduncles
posterior portion of the midbrain contains (1)
tectum (contains superior and inferior colliculi)
cerebral peduncles location
anterior midbrain
cerebral peduncles
3 paired bundles of axons
- ascending axons carry info to thalamus
- descending run between cerebrum, pons, medulla, and cord
tectum
located in the posterior midbrain
4 rounded nuclei elevations called colliculi
superior colliculi
2 of them
- reflex for visual activities like tracking moving things
- stimulate movement of the head, eyes, and neck in response to visual stimuli
inferior colliculi
2 of them
- part of auditory pathway, relays impulses from receptors to thalamus
- stimulate movement of the head, eyes, and neck in response to auditory stimuli
involved in startle reflex
what part of the brain is involved in the startle reflex?
the inferior colliculi in the tectum of the posterior midbrain
substantia nigra
nuclei in the midbrain
- dark in colour
- release dopamine
- located behind peduncles
red nuclei
nuclei in the midbrain
- axons from cortex and cerebellum synapse here to coordinate movement of the limbs
reticular formation
region throughout brainstem where white and grey matter are in a net like arrangement
reticular formation neurons hace both sensory and motor functions (T or F)
true
Reticular activating system (RAS) is formed by
the ascending part of the reticular formation
RAS stands for
reticular activating system
RAS functions to: (3)
- alert cerebral cortex to sensory signals to awaken from sleep
- maintain consciousness, alertness, and attention with stimuli from ears/eyes/etc
- prevent sensory overload by filtering stimuli
descending axons in RAS function to: (1)
(what do they maintain)
maintain muscle tone
what does the RAS not do?
is does not receive stimuli for the sense of smell
where does RAS project its sensory info?
to teh hypothalamus, thalamus, and cortex
inactivation of RAS results in
sleep
damage to RAS results in
a coma
RAS main function in shorter terms (2)
fight or flight response
sleep and waking
cerebellum contains what % of brain weight and what % of brain neurons
10% weight, 50% neurons
cerebellums surface is
highly folded to increase outer grey matter cortex surface area
special names for grey and white matter in the cerebellum
white - arbor vitae
grey - folia
functions of the cerebellum (main and subdivisions of main)
evaluate how well movements initiated by motor areas in the cerebrum are actually being carried out
- adjusts postural muscles for balance
- fine tunes voluntary/involuntary movements
- stores memories of learned movements
cerebellar hemispheres (left and right) consist of (4)
anterior lobes
posterior lobes
flocculonodular lobe
cerebellar peduncles
anterior and posterior lobes of the cerebellum function to
control subconscious
aspects of skeletal muscle movements
flocculonodular lobe of the cerebellum functions to
maintain equilibrium / balance
cerebellar peduncles function are/function is
white matter tracts that attach the cerebellum to the brainstem
- coordinate muscle movement
has superior, middle, and inferior parts
ataxia
loss of ability to coordinate movement due to damage of the cerebellum
cerebellum trick to remembering function
alcohol affects the cerebellum, think about what a drunk person is like
(posture, balance, memory, finetuning of movement, uncoordination)
diencephalon is located:
between top of brain stem and bottom of cerebrum
diencephalon fully surrounds:
the third ventricle
thalamus makes up waht % of diencephalon
80%
the thalamus is
paired oval masses of grey matter in left and right halves
- connected by interthalamic adhesion in most people
- contains nuclei and tracts
thalamus main function
relay station for sensory and motor function
thalamus sensory functions (2)
- sensory info (-smell) goes through it to the cerebral cortex
- acts as a filter, only passes a small portion of sensory info it gets to cortex
thalamus motor functions
- sends info from cerebellum and corpus striatum to primary motor areas of cerebral cortex
- involved in consciousness, learning, memory, emotions, and cognition
how many thalamic nuclei are there? no need to memorize the names
7
hypothalamus location
inferior to thalamus
how many nuclei does the hypothalamus have across all 4 regions
12 in 4 regions
main functions of the hypothalamus
control of the ANS
hormone production
emotions
regulation of eating
body temp control
circadian rhythms
4 main regions of the hypothalamus
posterior hypothalamic area
intermediate hypothalamic area
anterior hypothalamic area
preoptic area
posterior hypothalamic area L and F
anterior to midbrain
olfaction, feeding reflexes like swallowing
intermediate hypothalamic area L and F
anterior to posterior hypothalamic area
connects to pituitary gland (via infuncibulum)
- controls anterior pituitary gland
anterior hypothalamic area L and F
anterior to intermediate HA
transport ADH and oxytocin to posterior pituitary gland
preoptic area L and F
most anterior part of hypothalamus
regulate certain autonomic activities like body temp
hypothalamus - control of the ANS
axons from it extend to brainstem and cord
- stimulate smooth/cardiac muscle, secretions
- eg, regulation of heart rate, GI tract
hypothalamus - hormone production
release hormones into capillary network to anterior pituitary which stimulates or inhibits anterior pituitary hormone release
hypothalamus - emotions
works with limbic system to express rage, aggression, pain, arousal
hypothalamus - regulation of eating
contains thirst centre, feeding centre, and satiety centre
hypothalamus - body temp control
senses blood temp and restores regular temp via feedback loops
hypothalamus - circadian rhythms
serves as bodys internal clock
- receives visual input from eyes to synchronize to a 24 hour cycle
epithalamus location
superior and posterior to thalamus
epithalamus contains: (2)
pineal gland, habenular nuclei
pineal gland (2)
pea sized
secretes meletonin
circumventricular organs lack (CVO)
structures that border the third ventricle and lack a BBB
circumventricular organs (3)
parts of hypothalamus
pineal gland
pituitary gland
some other nearby structures
CVO functions
- monitor chemical changes in the blood
- allow hormones from hypothalamus to leave brain
supposed site where HIV enters the body
CVOs
due to lack of BBB
cerebrum allows
higher level thinking
cerebrum consists of: (3)
outer cerebral cortex (grey)
inner cerebral cortex (white)
deep grey matter nuclei
cerebral cortex has: (3)
cerebral gyri
cerebral fissures
cerebral sulci
cerebral gyri
rolls of folds of the cortex
“bulges”
cerebral fissures
deepest grooves between folds
- separate lobes
cerebral sulci
shallower grooves between folds
each hemisphere of the cerebrum is divided into:
4 lobes + one mini lobe
each hemisphere of the cerebrum receives sensory and generates motor input to the opposite side of the body because:
of the corpus callosum
lobes of the cerebrum (4+1)
frontal
parietal
occipital
temporal
mini lobe = insula
frontal lobe function
cognitive functions, emotions, voluntary movement
parietal lobe function
processes temperature info, taste, touch, movement proprioception
occipital lobe function
processes visual info
temporal lobe function
processes memories and integrates them with senses
insula function
taste
longitundinal fissure
separates cerebrum into left and right hemispheres
central cerebral sulcus
separates frontal and parietal lobes
lateral cerebral sulcus
separates frontal lobe from temporal lobe
parieto-occipital sulcus
separates parietal lobe from occipital lobe
association tracts (cerebral white mater)
connect and transmit nerves impulses between gyri in the same hemisphere
commissural tracts (cerebral white matter)
connect gyri from one hemisphere to the corresponding gyri of the other
eg. corpus callosum
projection tracts (cerebral white mater)
form descending and ascending tracts that transmit impulses form cerebrum to other brain and cord parts
3 directions of cerebral white mater tracts
between gyri in same side - association
between gyri on opposite sides - commissural
from gyri to other parts of brain and cord - projection
biggest fibre bundle in the brain
corpus callosum
the corpus callosum is a:
commissural tract
corpus striatum
3 nuclei deep within each cerebral hemisphere
functions of the corpus striatum (2)
receive input from cerebral cortex and send output to motor cortex
regulate initiation and termination of movements
limbic system parts (general areas)
bunch of structures from teh cerebrum, diencephalon, and midbrain
how is the limbic system connected
by the fornix
fornix
a white matter bundle that connects the limbic system
limbic system functions (3)
establishes emotional states
olfaction
memory
hippocampus is involved in:
memory storage and retrieval
3 types of areas in the cerebral cortex
sensory
motor
association (control complex integrative functions)
sensory areas of the brain function
reception and interpretation of sensory impulses
sensory areas of the brain (5)
somatosensory
visual
auditory
gustatory
olfactory
all of them have “primary” in front and “cortex” at the end
primary somatosensory cortex
has post central gyrus
- input from touch, pain, tickle, itch
- main function = localization of orgin and intensity of sensation
post central gyrus
gyri directly posterior to the central sulcus
primary auditory cortex
superior part of temporal lobe, near cerebral sulcus
- interprets basic sound charactaristics like pitch and rhythm
primary visual cortex
posterior tip of occipital lobe
- receives impulses that convey info (shape, colour) for vision
primary gustatory cortex
in insula
- receives impulses for taste
olfactory cortex
in temporal lobe on medial side
- receives impulses for smell
motor areas of the brain (4)
primary motor cortex
premotor cortex
brocas area
frontal eye field
sensory homunculus
misshaped map of sensory spots
motor homunculus
misshaped muscle map of the body
why does each region of motor area control skeletal muscles on opposite sides of the body
due to decussation
premotor cortex
anterior to primary motor cortex
- controls complex, learned movements
frontal eye field
partially in and anterior to premotor cortex
- controls voluntary scanning movement of eyes like reading
brocas area
helps to control speech articulation (speaking)
- mainly located in left frontal lobe
what does damage to brocas area result in?
the ability to understand remains, but production of speech is impaired
called brocas aphasia or non fluent aphasia
