CNS Flashcards
important function of the CNS
communication
ways that the CNS is involved in communication
with the external world - through peripheral CNS receptors eg sensor neurons, somatic and special senses
within the organism - visceral sensation, involuntary movement, somatic movement, higher cognitive functions - blood pressure and pH
what does the afferent division do
bring information to CNS from the receptors (somatic and visceral sensory)
what does the efferent division do
carries motor commands away from the CNS (that are processed and integrated) to peripheral tissues and systems via autonomic and somatic nervous systems
what makes our brain so complex
wrinkles ie gyrus increases the surface area - if cortex unfolded it would be 10x the size
we have the largest number of neurons in the cortex
describe the brain as an onion
has different layers
begin with reptilian brain - basic and instinctive behaviour eg eat, aggression and reproduce
increase complexity with layers - emotions
to primates with frontal cortex which plan and think of consequences
reflected in structure of brain - go from ancient parts to more modern and complex
what does the anatomical description ‘coronal’ mean
across - like a headband
what does the anatomical description ‘sagittal’ mean
through midline
what does the anatomical description ‘caudal’ mean
towards tail
what does the anatomical description ‘ventral’ mean
towards abdomen
what does the anatomical description ‘dorsal’ mean in the brain
superior
what does the anatomical description ‘rostral’ mean in the brain
towards the frontal lobe
what does the anatomical description ‘caudal’ mean in the brain
towards the spinal chord
what does the anatomical description ‘ventral’ mean in the brain
inferior
describe the spinal cord
a column of nervous tissue
protected in vertebral column - stack of vertebrae, hole in middle for spinal cord - allow movement
have holes called foramen - where nerves leave - interface with peripheral nervous system
where do the nerves leave the spinal cord
in cervical section they leave above the vertebrae
one also leaves below C8
after that they leave below the vertebrae
in cervical vertebrae how many nerves and vertebrae
8 nerves 7 vertebrae
sections of the spinal cord in order
cervical thoracic lumbar sacral coccygeal
in thoracic section how mant vertebrae and nerves
12
in lumbar section how many vertebrae and nerves
5
in sacral section how many vertebrae and nerves
5
in coccygeal section how many vertebrae and nerves
1
where does the spinal chord finish
start of the lumbar section
below this there is no tissue, just the emergence of nerves run to find vertebrae to emerge
where do you do a lumbar puncture
in the lumbar cistern - between L3 and 4 or L4 and 5 - safe because there is no nervous tissue, less risk to injure tissue
what is the cauda equina
bundle of fibres in the lumbar area
‘horse’s tail’
what changes throughout the spinal cord
the diameter larger diameter at cervical and lumber level - nerves for hands and legs emerge
what does each segment of the spinal cord correspond to
a part of body
dermatome (area of skin)
myotome (area of muscle)
how do nerves leave the spinal cord
by dorsal and ventral route join to form nerve
communication with sympathetic ganglia - line side of vertebral column
what is the grey matter
where the cell bodies are
why is the white matter white
where the myelinated neurons are
structure of spinal cord
core of grey matter surrounded by funiculi of white matter
describe the horns in the spinal cord
the dorsal and ventral routes travel out of the dorsal and spinal horns where their respective cell bodies are
dorsal horn has sensory neurons
ventral horn has motor neurons
what is the ascending tract of the white matter
axons go up to the brain
what is the descending tract of the white matter
axons go down the spinal cord
they send instructions to muscle
what is the autonomous role of the spinal cord
reflexes
describe the patella reflex
quadriceps are elongated
sensory receptor
signal to grey matter
motor neuron sendsignal for muscle to contract
collateral signals go to brain - you are conscious of the action but it is controlled on the spinal cord
sections of the brain as from embryonic origin
forebrain(prosencephalon): diencephalon - thalamus and hypothalamus, cerebral hemisphere (telencephalon)
Midbrain
Hindbrain (rhombencephalon): brain stem - pons and medulla oblongata, cerebellum
sections of the brain with functional characteristics
Cerebrum: cerebral hemisphere, diencephalon - thalamus and hypothalamus
brain stem(blub): midbrain, pons, medulla oblongata
cerebellum
what is the bulbar tract
it is from the cortex to the brain stem
similarity of things in the brain stem
have a similar function
relationship between spinal cord and brain stem
they are continuous
similar structure of grey and white matter
cranial nerves in brain stem
origen brain stem (nuclei there)
important for breathing, control of heart beat, swallowing and eye movement - lesion in brain stem is fatal
describe the cells in the brain stem
enlargement of brain stem with deposition of pyramidal neurons - motor tracts from the brain stem to spinal cord, this is where they cross - control opposite side of the body
substantia nigra
degenerate in parkinsons
in mid brain
pons
bridge connect brain stem to cerebellum
describe the diencephalon
has the thalamus - is bilateral, one either side of the brain
it is in the centre of the brain
info from all afferents - integration for somatic and special senses and projects info to the cortex
involved in appropriate movement, emotional status consciousness and the sleep wake cycle
hypothalamus: integration centre (visceral) . regulates temp, hunger, thirst, hormones and autonomic function
what is a ganglion
a group of cell bodies in the peripheral nervous system
what is a nucleus
group of cell bodies in the CNS
what is the subcortical structure in the cerebral hemisphere
the basal ganglia
what is the function of the basal ganglia
control movement
facilitate voluntary movement
inhibit unwanted or inappropriate movements
fine tuning
main basal ganglia
caudate nucleus - tadpole shape
putamen
together form the corpus striatum because connections between them make stripes
putamen and globus pallidus form lentiform nucleus (shape like a lense)
other structures in basal ganglia
substantia nigra
subthalamic nucleus (in diencephalon)
nucleus accumbens
substantia nigra role
fine tunes movement
suppresses movement
coordinates signals from cortex and cerebellum
describe the cerebral cortex
2-4mm thick
wrinkled in gyrus - only 30% exposed
70% within the sulci
fissures divide the gyri into lobes - central fissure separate frontal and parietal lobe
motor association area
neurons plan program for contraction of muscles required for an action
primary motor cortex
neurons send signals for precise finely coordinated limb movement - contralateral
primary somesthetic cortex
primary somatosensory cortex for touch pain and temperature
somesthetic association area
interprets sensory info eg for hand eye coordination
visual association area
recognise faces
primary visual cortex
receive visual signals
primary auditory cortex
receive auditory signals
auditory association are
recognise signals received as spoken words
primary gustatory cortex
receive taste signals
prefrontal cortex
personality, judgement, interpretation of the world , planning
broca area
motor program for speech
moves tongue and lips
Wernicke area
recognition of spoken word and speech
describe the lamina of the cortex
6 layers
layer where only pyramidal cells
layer where there is only connecting white layer
older parts eg hippocampus - simpler with only 3/4 layers
describe the somatotopic of the cortex
each part of the body is recognised on the brain
face hand and lips a lot of nerve terminals
describe the limbic system
made from different parts of the brain with the same function
mamillary body in midbrain
limbic = edge - arranged around the edge of the midbrain
what is the action of the limbic system
motivation, instinctive behaviour, emotion, memory, fear
parts of the limbic system
amygdaloid body mamillary body hypothalamus anterior group of thalamic nuclei corpus callosum fornix pineal gland cingulate gyrus parrhippocampal gyrus hippocampus
describe the cerebellum
made of 2 hemispheres white matter in the middle grey at the edge have folia - increase SA central vermis attached to brainstem posteriorly with 3 pairs of peduncles
what is the cerebellum connected to
vestibular system for balance
spinal cord and muscles for movement, muscle tone and posture
motor cortex and thalamus for learned movement - disease manifest as ataxia
describe features in the white matter
commissural fibres - connect between 2 hemisperes
association fibre - connect within hemispheres
projection fibres - from cortex to spinal cord through internal capsule and spread out at corona radiata reach many parts of the cortex
describe the cranium
base of skull have different hollows
anterior fossa - frontal lobe
posterior cranial fossa - midbrain and cerebellum
middle cranial fossa - temporal and hypothalamus
fibres through foramen magnum, tiny holes where nerves leave the skull
describe the meninges
dura mater - hard and hass fibres, periosteal connect to skull and meningeal connect to lower meninges -venous
arachnoid mater - connective tissue, hold vessels in place
subrachnoid is where the vessels run, full of CSF - fill ventricles
pia mater - follow the gyrus - more flexible
describe the ventricular system
hollow space in CNS
lateral ventricles: anterior, inferior and posterior horn
joined by interventricular foremen between thalamus
aceduct goes from 3rd ventricle to 4th ventricle, continuous with the central canal
what happens at the choroid plexus
untrafiltration of plasma
CSF produced
network of capillaries line ependymal cells - filtered into the ventricles
how much CSF is produced a day
500ml
how does CSF composition differ to plasma composition
lower glucose, protein, ca and k and pH
higher cl and Mg
how can the CSF give diagnostic information
if high protein shows abnormality eg infection
what is the function of the CSF
it is cushioning, circulates nutrition, removes waste and circulates immune cells
describe the pathway of CSF
made in choroid plexys lateral ventricle through interventricular foramina 3rd ventricle cerebral aqueduct 4th ventricle through lateral and median apertures subarachnoid space arachnoid villi of dural venous sinuses venous blood heart and lungs arterial blood
what happens in aqueduct is blocked
by infection/tumour/malformation
hydrocephalus
enlargement of the ventricle, compression of tissue and can result in enlargement of the whole head
