4. Forebrain Flashcards
forebrain: define
refers to cerebellar hemispheres & diencephalon
(aka prosencephalon)
what are the 3 components in the diencephalon?
- thalamus
- hypothalamus
- epithalamus
thalamus: function
- major relay for sensory information to the cortex (except olfaction) & between cortical structures
- “egg shaped” bunch of nuclei; many discrete nuclei, diff’t nuclei receive diff’t modality information
- part of diencephalon
hypothalamus: function
regulates homeostasis and influences hormone release
epithalamus: function
influences sleep and wakefulness thru pineal gland
(posterior aspect of diencephalon)
what sensory info does NOT pass through thalamus?
The olfactory nerve (CN 1) travels directly to the frontal lobe through the cribriform plate
- this is the only sense that does not travel to the thalamus before accessing the forebrain.
thalamus:
processes involved
- perception
- timing
- attention
- alertness
- movement
- awareness
- consciousness
how are thalamic nuclei organized/arraged?
in 5 diff’t groups
- anterior
- medial
- ventral
- lateral
- posterior
Cranial nerve 1:
- key characteristics/actions
- sensory/motor
- innervates…
- clinical sign
- only sensory info that goes directly to nuclei in cortex (not thru thalamus)
- SENSORY ONLY
- inn. nasal mucosa to contribute to olfaction/sense of smell
- CC: impaired sense of smell
pathway of sensory info from olfaction
olfactory nerves in nose –> through cribriform plate –>
olfactory bulb –> olfactory tract –> nuclei in cortex
cranial nerve 2
- key characteristics/actions
- sensory/motor
- innervates…
- clinical sign
- optic nerve; originates in RETINA
- SENSORY ONLY
- contributes to vision
- CC: blindness in all or part of visual field
course of optic nerve
retina, where optic nerve originates –>
through optic chiasm –>
optic tract –>
thalamus?
optic chiasm
x-shaped structure where some fibers of optic nerve cross and innervate structures on contralateral side; some continue on and innervate ipsilateral side
hypothalamus: define
group of small nuclei
rostral to brainstem
hypothalamus: how does it regulate homeostasis?
- influences pituitary gland
- regulates food/water intake
- regulates sleep/wake cycle
- regulates Parasymp and symp nervous systems
KEY CONCEPT: hypothalamus has several discrete nuclei involved in homeostatic functions
many discrete nuclei involved in homeostatic functions
what is key role of each THALAMIC NUCLEI?
- anterior
- medial
- ventral
- lateral
- posterior
- anterior - part of limbic system; memory and emotion
- medial - emotional output to prefrontal cortex; awareness of emotions
- ventral - somesthetic output to postcentral gyrus –> signals from cerebellum and basal nuclei to motor areas of cortex
- lateral - somesthetic output to assoc. areas of cortex; contributes to emotional function of limbic system
- posterior - relay of visual signals to occipital lobe and auditory signals to temporal lobe
location of hypothalamus
extends anteriorly from the optic chiasm, to the mamillary bodies posteriorly
what makes up the epithalamus?
- habenula
- pineal gland
pineal gland: function
posterior aspect of diencephalon that contains the pineal gland
gland produces melatonin –> regulates wakefulness
(very hard to dissect, but posterior to THALAMUS)
cerebral hemispheres
largest part of brain; w/ structures duplicated in each hemisphere
- disctinct grooves and folds called sulci and gyri
- divided into lobes, w/ some distinct functions
purpose of folds and grooves (gyri & sulci) in brain?
to increase surface area –> fitting more into less “Real estate”
gray matter is found where in cerebral hemisphere?
found in cerebral cortex & deep nuclei
white matter is found where in cerebral hemispheres?
much of volume of cerebral hemisphere is white matter
- 3 main types of fibers
- internal capsule
3 types of white matter fibers,
& what they do
- projection fibers - sensory connections from the brainstem, and spinal cord and motor connections to brainstem and spinal cord
- association fibers - connections w/in lobes or from one lobe to another
- commissural fibers - connections between hemispheres
four lobes and general functions
- FRONTAL (primary motor cortex)
- cognition, decision-making, judgement, voluntary movement
- PARIETAL (somatosensory cortex)
- touch, proprioception
- OCCIPITAL (primary visual cortex)
- vision
- TEMPORAL (amygdala, hippocampus)
- auditory, olfactory, fear response, learning
frontal lobe (gross)
bordered by central sulcus, and lateral fissure are both folds
pre-central gyrus
part of frontal lobe;
contains primary motor cortex
fxn: area controls execution of movement
primary motor cortex - “motor map”
- distinct areas of primary motor cortex control movement in specific parts of the body
- notice more real estate is given to areas w/ more moving parts
- (accounts for greater amount of the motor cortex)
parietal lobe: boundaries
- bordered by the central sulcus, and lateral fissure
- the posterior border is less well-defined
parieto-occipital sulcus separates which 2 lobes?
between (1) parietal, and (2) occipital lobe
where is the post-central gyrus located, and function
- bordered by central sulcus and lateral fissure
- function: main receptive area for the sense of touch and contains a somatosensory “map” (homunculus)
- the map shows areas that require a more sensitive touch gradient receive more real estate
occipital lobe: borders
- bordered by the preoccipital notch
- contains primary visual cortex; primary visual cortex processes vidual information and creates a map of the visual field
occipital lobe: functions
contains primary visual cortex; which processes visual information & creates map of visual field
Temporal lobe: borders and function
- bordered by lateral fissure and the pre-occipital notch
-
involved in audition
- deeper in the temporal lobe is vertically-oriented gyri which comprise the insula (pain and taste fxns)
which 4 structures make up the DEEP NUCLEI?
- globus pallidus
- caudate
- putamen
- amygdala
which of the deep cerebral nuclei are considered BASAL nuclei?
- caudate
- putamen
- globus pallidus
basal nuclei: function
invovled w/ onset and cessation of intentional movements; esp repetitive ones
internal capsule: definition and functions
- large fiber tract amid the deep cerebellar nuclei
- Incl. axons relaying sensory info from thalamus to cerebral cortex, and axons relaying motor signals to motor neurons from the cerebral cortex to lower neurons
location of deep cerebral nuclei and internap capsule - gross anatomy
