lecture7: organisation of the CNS Flashcards
*draw a diagram to explain the relationship between the following divisions of the CNS
insert the pic
what are the three main components of the brain stem?
- the midbrain - the pons - the medulla
what are the main functions of the brain stem?
- contains a lot of nuclei which control vital things like respiration and cardiac control - ascending pathways to the brain - descending pathways to spinal cord - cranial nerves which provide sensory and motor innervation for the head region - the reticular activating system controls the level of consciousness
* show a diagram of where the diencephalon is?
INSERT PIC
what are the two main structures in the diencephalon?
- thalamus - hypothalamus
what is the function of the thalamus?
it is a relay station for info going between the cerebral correct and other parts of the CNS (bi directional)
where is the thalamus found?
in the upper area of the diencephalon
what is the function of the hypothalamus ?
controls homeostasis
where is the hypothalamus found?
- found below the thalamus
where is the basal ganglia found?
- found deep inside the cerebral cortex and is one of the main nuclei
what is the function of the basal ganglia?
- needed for movement control - group of nuclei which produce the pattern of movement and work together with the motor cortex
* where is the cerebellum found?
INSERT PIC - found towards the back of the head
what is the function of the cerebellum?
- it doesn’t initiate movement but it coordinates the movement and is important for learning new motor skills
* show a diagram of a brain with the following labelled: - cerebral hemisphere - diencephalon - midbrain - pons - medulla - cerebellum
insert the pic
what are the three main parts of the brain and what do they split into?
the forebrain - cerebral hemispheres and diencephalon the midbrain - the hindbrain- pons medulla and cerebellum
* identify on a digram the cortical lobes and the primary cortical areas:
what are the two main types of cortex?
- primary cortical areas - the basic functions happen here - discrete parts of the brain 2. association cortex - the rest of the brain - higher functions happen here
what are the four main cortex’s?
- primary motor cortex - primary somatosensory cortex - primary auditory cortex - primary visual cortex
what do the following cortex’s do? - primary motor cortex - primary somatosensory cortex - primary auditory cortex - primary visual cortex
- the motor cortex sends axons down a descending pathway to stimulate motor neurones in the spinal cord - the somatosensory cortex receives general sensory information - the primary auditory cortex receives information from the ears - the primary visual cortex receives information from the ears
what is the corpus callous for?
connecting the right and left hemisphere across the midline
what is wernickes area for?
- important for understanding language
what is brocas area for?
- important for speech
* show a diagram of the brain highlighting the different lobes:
INSERT PIC
* show a diagram showing the different parts of the cranial fosse
INSERT PIC
what ventricles are there in the brain?
- there are two main ventricles - they are C shaped - they are called lateral ventricles - they join up in the middle by a midline ventricle called the 3rd ventricle - the 3rd ventricle is located in the middle of the diencephalon - at the base of the third ventricle there is a narrowing which makes a fine channel called the cerebral aqueduct - the aqueduct passes through the midbrain and opens up into the fourth ventricle - the fourth ventricle then lowers again to make a very fine channel called the central canal
what is the composition of the cerebrospinal fluid?
- produced by the ependymal cells which are found in the ventricles called the choroid plexus - the choroid plexus filters the blood and secretes it
what is the difference between blood and CSF fluid?
the CSF fluid has - fewer cells, - less protein and - reduced concentrations of sodium and potassium - higher concentration of magnesium and chloride ions
how is the CSF fluid circulated?
- circulates through the ventricular system - gets to the 4th ventricle where it can exit and move across the brain - the CSF then circulates again in the sub arachnoid space between the meninges - it is then reabsorbed into the venous system by arachnoid villi
what is the function of the CSF fluid?
- to cushion the brain and acts as a shock absorber - to circulate nutrients and filter chemicals from the blood - to remove waste products from the blood
what is the average total volume of the CSF?
150 ml
what is the average flow rate of the CSF?
500 ml a day
what is a epidural haemorrhage?
this is a bleed which is between the skull and the dura - the is caused by the rupture of the middle meningeal artery
what is a subdural haemorrhage?
between the inside of the dura and the brain itself
what is the hydrocephalus?
this is a blockage of the sub arachnoid space caused by the build up of the CSF can lead to stroke if there is bleeding
what are the two types of stroke and what do they mean?
- communicating presents with headaches - non communicating presents with blackouts
how is hydrocephalus treated?
it is treated by using a stunt to divert the CSF or by removing the cause
what are the three membranes which enclose the brain and the spinal cord?
- the dura mater - tough membrane attached to the bone with folds and venous sinuses in the margins 2. the arachnoid membrane - thin membrane attached to the underside of the dura 3. pia mater delicate membrane which is closely adherent to the surface of the brain and the spinal cord
where is the sub arachnoid space?
- this is located between the arachnoid and the pia where the CSF circulates
what is the structure of the spinal cord?
- the spinal cord is a column of neural tissue which is segmental - each segment has one pair of spinal nerves - the core consists of grey matter - there is a wrapping around of white matter - they grey matter is divided into sensory and motor areas
*show a diagram of the cross section of a spinal cord:
insert pic
what are dorsal horns?
dorsal horns of grey matter are sensory centres
where does the soma of the sensory axon lie?
the dorsal root ganglion
where does the axon continue?
the axon continues via the dorsal root and enters the dorsal horn
where is the sensory information carried after the dorsal horn?
the sensory information is then carried up ascending pathways in the white matter to the brain for analysis
what is the ventral horn?
the ventral horn is the motor centre
where do the axons of motor neurones go?
the axons of the motor neurones go out via the ventral roots and to the muscles
what is towards and away from the CNS dorsal ventral
- dorsal - towards the CNS - ventral - away from the CNS
where does the spinal cord lie?
- the spinal cord lies in the vertebral canal in the vertebral column
what are the intervertebral foramina?
along the sides of the vertebral column there are a series of holes called the intervertebral foramina
what are the cervical levels?
C1- C7
what are the thoracic levels?
T1 - T12
what are the lumbar levels?
L1 -L5
what are the sacral levels?
S1 - S5
what is the number of nerves and vertebrae compared to each other?
there is an equal number of nerves and vertebrae except there is an extra nerve above C1 so there are 8 cervical nerves not 7
what is shorter the spinal cord or the vertebral column?
- the spinal cord is much shorter than the vertebral column - this is because the spinal cord finishes growing much earlier in development compared to the vertebral column - the cervical and thoracic segments of the spinal cord are corresponding to the vertebral column levels
what is the lumbar cistern?
this is the area with no spinal cord - it contains CSF fluid and a needle can be inserted to take a sample of the fluid
where are lumbar punctures taken from?
between L3 and L4
where is the area with no spinal cord but many nerves?
- cauda equina
what is the function of the cerebellum?
motor function
- coordinated movement
the function of the brains stem?
- contains nuclei which control our vital functions
- lots of ascending and descending pathways that go through the brain stem
- ascending goes up to the brain stem
- descending goes down from motor cortical regions to the spinal cord to produce movement
function of the diencephalon?
- thalamus is the higher region of the diencephalon
- this is a relay station for info which goes between the cerebral cortex and other parts of the CNS
- the hypothalamus is found inferior to the thalamus and is needed for homeostasis
function of the cerebral cortex?
- lots of nuclei present
- one of the main nuclei is the basal ganglion
- the basal ganglia are the group of nuclei which produce a pattern of movement and work together with the motor cortex.
