central nervous system Flashcards
what does the central nervous system consist of?
- brain
- spinal cord
how is information relayed to the CNS?
- by afferent neurones in peripheral nervous system
what does the CNS do with the information?
- collects and processes it
- stores info and responds when appropriate
how and where is information transported out CNS to?
- to effector cells
- by the efferent neurones of the peripheral nervous system
what is the brain divided into?
- two hemispheres
(left and right)
what does the left hemisphere control?
- logic
- numbers
- language
what does the left hemisphere process?
- sensory and motor pathway for the right side of the body
what does the right hemisphere control?
- creativity
- imagination
- rhythm
what does the right hemisphere process?
- sensory and motor pathways of left side of body
what are the two hemispheres joined by?
- neural bridge of nerve fibres known as corpus callosum
- allows communication
where is the corpus callosum seen?
- superiorly by looking down through deep fissure between two halves
- medial view by separating the cerebral hemispheres
what are the different components of the brain?
- forebrain
- midbrain
- hindbrain
what does the forebrain consist of?
- cerebrum
- thalamus
- hypothalamus
is the midbrain divided into more areas?
- no
what does the hindbrain consist of?
- cerebellum
- pons
- medulla
what does the brainstem consist of?
- midbrain
- pons
- medulla
what is the function of the midbrain?
- controls higher functions
- controls eye movement
- controls auditory system
what is the function of the medulla?
- controls very basic, life sustaining functions
- eg. breathing, heart rate
what does the pons have roles in?
- consciousness
- posture
what does the cerebellum consist of?
- two mounds of folded tissue posterior to brainstem
what is the cerebellum connected to the brainstem by?
- three peduncles (bands of neurones resembling a stalk)
what is the role of cerebellum?
- motor functions
- motor learning (riding bike)
what does the cerebellum receive inputs from?
- ascending sensory pathways from body
- descending motor pathways from cerebrum
- other info from brainstem
what is the thalamus?
- relay point
what happens at the thalamus?
- all inputs to cerebrum synapse before ascending to cerebral cortex
what is the main function of the hypothalamus?
- homeostasis
what does the hypothalamus directly control?
- blood pressure
- body temperature
- fluid and electrolyte balance
- body weight
what body processes are controlled by hypothalamus?
- heart rate
- vasoconstriction
- digestion
- sweating
where does the autonomic nervous system originate?
- hypothalamus via inputs to medulla
what does stimulation of pituitary gland cause?
- release of hormones
what does most of the volume of cerebral hemispheres consist of?
- white matter
what does the white matter contain?
- axons
what do the axons connect?
- cell bodies found in grey matter
what does the grey matter make up?
- cerebral cortex
where does grey matter exist?
- surface of hemispheres
what does the cerebral cortex control?
- intelligence
- personality
- interpretation of sensory impulses
- motor function
- planning and organisation
- touch sensation
what is the sulci?
- inholdings of brain
- mark boundary of different functions
what is the gyri?
- sticky out bits between sulci
- areas of functional grey matter
what are the key structures of the brain?
- frontal lobe
- parietal lobe
- temporal lobe
- occipital lobe
- central sulcus
- pre central gyrus
- post central gyrus
- lateral fissure
- corpus callosum
- Pareto-occipital sulcus
what is the primary motor complex?
- pre central gyrus
what is the somatosensory cortex?
- post central gyrus
what is the function of the frontal lobe?
- integrated brain functions (planning)
- emotional responses
what is the function of the parietal lobe?
- movement
- orientation
- recognition
what is the function of the occipital lobe?
- involved with visual cortex
what is the function of the temporal lobe?
- integrating sound and speech
- forming memories
what is the function of the pre-central gyrus?
- location of primary motor complex
- movement
what is the function of the post-central gyrus?
- location of primary somatosensory cortex
- touch
- pain
- temperature
- proprioception
what is the CNS covered by?
- meninges
what is the purpose of the meninges?
- layer of tissues that separates CNS from rest of body
what 3 layers is the meninges made up of?
- pia mater
- arachnoid mater
- dura mater
what is the Pia mater?
- adherent to brain
- dips down into sulci of brain
what is the arachnoid mater?
- middle layer
what is the dura mater?
- outermost
- very tough
what is the CNS bathed in within the meninges?
- cerebrospinal fluid (CSF)
what does the combination of CNS and meninges allow?
- cushioning of brain
- protection of damage
what is CSF produced by?
- specialised epithelium (choroid plexus)
- lines cavities within brain known as ventricles
what does the choroid plexus actively secrete?
- components of blood plasma into ventricles
what does the choroid plexus produce?
- clear fluid
- lower in proteins, cells and ions than the plasma
what does CSF have a higher concentration of than in plasma?
- sodium ions
- chloride ions
- magnesium ions
why does CSF have high conc of these ions?
- chemicals are actively transported by epithelium into the CNS
what does the CSF circulate through?
- ventricles (cavities) within brain before exiting onto surface of brain
- to bathe brain and spinal cord
where is CSF reabsorbed?
- into venous circulation at arachnoid granulations
what are the ventricles of the brain?
- spaces or cavities within brain
- linked by passageways called aqueducts
what do the aqueducts allow?
- CSF to circulate through the brain and open onto surface of CNS
what is the lateral flow of the CNS?
lateral ventricles ->
inter ventricular foramina -> third ventricles ->
cerebral aqueduct ->
fourth ventricle ->
median/lateral apertures ->
central canal
what is the spinal cord covered with?
- meninges
what does the CSF surround?
- spinal cord
where does the CSF also flow through?
- central canal that runs through centre of the cord
where does the spinal cord terminate in adults?
- L1
what does the spinal cord contain below L1?
- spinal nerves
- descend within meninges util they exit at their vertebral level
what is the caudal equina?
- nerves within meninges
- inferior to termination of spinal cord
what is lumbar puncture/spinal tap procedure?
- CSF can be removed from this space with a needle with minimal risk of damaging nerves
what happens if a needle in inserted below L1?
- spinal nerves can float away
what happens if needle is inserted above L1?
- risk of piercing the spinal cord
what layers does the needle pass through to reach the CSF?
- skin
- subcutaneous tissue
- supraspinous ligament
- interspinous ligament
- ligamentum flavum
- extradural space
- dura mater
- arachnoid mater
- subarachnoid space (where CSF is found)
what is the fluid removed to test?
- the health of the CNS
what would indicate an infection like meningitis?
- increased levels of white blood cells
what could indicate brain haemorrhage or stroke?
- increased levels of red blood cells
