Lecture 3 Flashcards
The nervous system II : CNS / Brain
What responds to changes in environment
dozens of specialised receptor cells
( most are not neurones but are directly connected to sensory neurones)
when do we sense things ?
when things are changing
getting used to a specific stimulus
sensory adaptation
sensory neurone –> spinal nerve how >?
long myelinated sensory neurone from all over the body ( except head ) enters spinal cord
via dorsal root of spinal nerves
where to neurones send axons when they’re sending precisely localised information?
top of spinal cord ( medulla )
where to neurones send axons when they’re sending poorly localised information?
axons synapse immediately with other neurones
all sensory neurones go together into one inter-neurone which sends signals to brain
where do sensory nerves from head send axons ?
directly into brain via cranial nerves ( eg optic nerve )
what are all signals transmitted via ( from head )
several relay stations
integrated with other incoming signals from ‘lower’ , ‘higher’, and same level processing stages
brain stem has..
hind brain and midbrain
hind brain has
medulla + pons + cerebellum
medulla + pons
where spinal cord enters brain
has lots of nuclei of the autonomic NS
cerebellum
‘little brain’
not part of brain stem
balance , motor learning
midbrain is also called + where is it
mesencephalon
above pons
midbrain function
information from diff sense modalities
direction of attention
forebrain has ( diencephalon part )
thalamus
hypothalamus
thalamus
massive stucture on top of midbrain
centre of brain
main relay station for incoming sensory signals
receives downward going input from higher areas, modulating the relay of sensory signals
hypothalamus
small structure in front of + below thalamus
directly connected to pituitary gland (master gland of endocrine system - controls activity of all other glands )
gateway to ES
- NS can influence ES via hypothalamus - pituitary connection
telencephalon ( the forebrain )
cerebral hemispheres
basal ganglia
limbic system
cortex and corpus collosum
diencephalon
thalamus ( right and left )- to moderate sensory signals
hypothalamus
cerebrum
where do the signals coming from the diencephalon go ?
incoming signals go up to the cerebrum
cerebral hemispheres
divided into two highly similar hemispheres
each covered in cerebral cortex
also has several groups of sub-cortical nuclei
cerebral cortex
( thin layer of neurones covering each hemisphere )
sub-cortical nuclei
tight cluster of neuron’s cell bodies
how do hemispheres receive input and send output ? ( direction )
to the contralateral side of the body
basal ganglia
group of nuclei surrounding the thalamus
motor control process
has globus pallidus, putamen, caudate
what is sometimes considered inside the basal ganglia ?
amygdala closely connected to this system, so its sometimes considered in the basal ganglia - but usually in context of limbic system
putamen and caudate
corpus striatum ( striped body )
limbic system
several interconnected cortical and sub-cortical areas
role in memory + emotion
sub-cortical areas in limbic system
almost complete circle formed by formix and hippocampus , ending in mammillary body and amygdale
what is the limbic system connected to
hypothalamus (septum) and olfactory system - sense of smell
cortical area in limbic system
cingulate cortex directly above corpus callosum (evolutionary older )
Cortex and corpus callosum parts
cerebral cortex
corpus callosum
longitudinal fissure - sulcus
gyrus
occipital lobe
temporal lobe
cerebral Cortex structure
multi layered sheet of neurones cell bodies covering the whole hemisphere
( not just the outside but inner medial surface also )
corpus callosum structure
thick bundle of axons connecting two hemispheres
corpus collosum function
all signal transfer between corticles of the hemispheres does here
gyrus
outward folded areas
highly folded, forming gyri
sucli
inward folded areas
longitudinal fissure
largest sulcus ( shallower groove that surrounds gyrus )
separating left and right hemispheres
smaller sulci used to define boundaries of cerebral lobes
occipital lobe
visual perception
temporal lobe
auditory perception
parietal lobe
somatosensory perception
inter-sensory + sensory motor integration
frontal lobe
planning and motor output
general processing principle
sensory input from right side of body ( of right visual field ) is processed in the left half of the brain
motor output to the right side of the body is generated in left half of brain
sensory signals from diencephalon relayed where ?
relayed to their appropriate primary sensory cortex
how is the way a signal is interpreted depend on ?
on its location
where to visual signals go to ?
visual cortex (occipital lobe)
where to auditory signals go ?
auditory cortex (temporal lobe)
signals from skin, muscles and joints go where ?
somato-sensory cortex ( parietal lobe )
topographic representation
inside specific sensory areas, signals arrive at positions corresponding to the position of the receptor cells
signal transmission and interpretation
somatotopic map
signals from the hand arrive in the hand area of somatosensory cortex
next to the arm area
..which is next to shoulder area
retinotopic map
visual signals from neighbouring retinal positions arrive at neighbouring positions in the primary visual cortex
tonotopic map
auditory signals from adjacent areas of the chochlea arrive at adjacent areas in the primary auditory cortex
why do so many topographic maps exist ?
for each sense modality
direction of signal transmission - transmission + location
neurones transmit signals only in one direction
dendrites –> cell body/soma –> end of axon
direction of signal transmission - receive
some input comes from functionally ‘higher’ processing areas (top down or feed-back)
other inout comes from earlier functionally ‘lower’ processing areas (bottom up or feed forward )
other input comes from neighbouring neuron’s in the same area
cortical motor areas location
in frontal cortex
at boundary of parietal cortex
function of supplementary cortex and pre-motor cortex
involved in planning, monitoring, sensory guidance of movements
primary motor cortex does what ( final execution stage )
its motor neurones send axons directly down the spinal cord
( the pyramidal tract)
what is the cortical motor area connected with ?
2 sub-cortical structures - forming complex motor control circuits
basal ganglia , cerebellum
basal ganglia does what in motor control circuits ?
modulate movements - particularly involves in selective inhibition movements
they selectively inhibit movements
cerebellum does what in motor control circuits ?
involves in maintaining posture + balance
timing of movements
motor learning eg. walk
where do basal ganglia and cerebellum receive their input from?
motor cortex,
sensory cortex,
other sub-cortical structures
