Central nervous system Flashcards
What forms the CNS?
Brain and spinal cord
What is the function of the brain?
Where afferent neurones are processed and a complete response is co-ordinated through efferent descending tract of neurones
What are the three distinct areas of the brain?
Forebrain, mid brain and hind brain
What is the forebrain?
Cerebral hemispheres. and diencephalon
What is the hindbrain?
Cerebellum, pons and medulla
What forms grey matter?
Cell bodies
What forms white matter?
Nerve fibres (myelinated neurones)
Which tracts decussate at the medulla as they leave the brain?
Dorsal columns
Corticobulbar
Corticospinal
What separates the cerebrum into two cerebral hemispheres?
Longitudinal fissure
What is the cerebral cortex?
Represents the outer layer of the cerebrum, consists entirely of grey matter- cell bodies, dendrites and synapses
What connects the two cerebral hemispheres together?
Corpus callosum (white matter)
What are the four main lobes of the cerebral hemispheres?
Frontal, parietal, temporal and occipital
What is the frontal lobe associated with?
Higher brain functions - emotional responses, planning, reasoning and decision making
Regulating and initiating motor function, language, attention and memory
What is the parietal lobe associated with?
Sensation (touch, pain), understanding spatial orientation and cognition. Sensory aspects of language
What is the occipital lobe associated with?
Controls range of visual functions: shape recognition and colour vision
What is the temporal lobe associated with?
Vision, memory, language, and comprehension
Processing auditory function
What is the limbic lobe associated with?
Amygdala, hippocampus, mamillary body and cingulate gyrus
What is the function of the hippocampus?
Responsible for the consolidation of learning from short term to long term
What is the mammillary body associated with?
Recollective memory
what is the limbic system concerned with?
Memory, emotion, motivation, reward and learning
Where is the insular cortex located?
Located in each cerebral hemisphere, deep within the lateral sulcus
What is the lateral sulcus?
Tissue separating the temporal lobe from parietal and frontal lobes
What is the insular cortex associated with?
Visceral sensations, autonomic control, interoception, auditory processing and visual-vestibular integration
What is visual vestibular integration?
Balance of eye movements
What is interoception?
Internal recognition
What three layers form the meninges?
Dura mater, arachnoid, and pia mater
Where does the subarachnoid space lie?
Between the arachnoid and Pia mater
What layers consist of the dura mater?
Periosteal and meningeal
What is the periosteal layer?
Layer of periosteum, lines internal cranium,
What is the meningeal layer?
Dural, dense fibrous membrane
Thick membrane consisting of dense irregular connective tissue, surrounding the brain and spinal cord.
What is the purpose of the subarachnoid space?
Contains cerebrospinal fluid
What is pia mater?
Thin, translucent & mesh like. Highly vascular membrane, closely adherent to the surface of the brain
Where is CSF produced?
Choroid plexus
Where is the choroid plexus located?
Lateral 3rd and fourth ventricles
Where does the CSF occupy?
Occupies the ventricular system, subarachnoid space, cisterns and central canal of the spinal cord
How is CSF reabsorbed?
Arachnoid villi (granulations) into superior sagittal sinus
Which foramen enables transpiration of CSH to the third ventricle?
Foramen of monroi
What is the foramen Lushcka?
Facilitates movement of the fluid into the subarachnoid space
What are the comparisons between CSF and plasma?
Lower pH, less glucose and potassium
Clear fluid- absent of blood and proteins
How can CSF be used as an indicator for pathological disease?
Protein blood detection in CSF
Which nerves are carried by the posterior ramus?
Visceral motor somatic motor and sensory nerves
Where do nerves emerge through?
Intervertebral foramina
Describe the progression of nerves descending along the spinal cord in respect to vertebrae?
Nerves become more angled between the spinal cord.
Nerves protrude outwards further away from the cord
Further a nerve is, the larger the distance and greater the angle to the corresponding bone
How many pairs of nerves are there?
31 pairs
How many vertebrae are there?
30
What sections divide the spinal cord?
Cervical, thoracic, lumbar, sacral and coccygeal;
How many nerves are associated with cervical?
8
How many nerves associated with thoracic vertebrae?
12
How many nerves associated with lumbar vertebrae?
5
How many nerves associated with sacral vertebrae?
5
How many nerves emerge with coccygeal vertebra?
1
Which nerves emerge above vertebrae?
C1-C7
Which nerves emerges below vertebrae?
C8 - Co1
What does the spinal cord contain?
Grey matter surrounded by white matter which stems from the medulla oblongata through vertebra
How are spinal nerves attached to the spinal cord?
Dorsal and ventral roots- contain sensory and motor nerve fibres respectively
Where are the cell bodies of sensory neurones located within the dorsal root?
Dorsal root ganglion
Where do motor neurones leave the spinal cord?
Ventral root
What does spinal grey matter contain?
Intermediate nerve cells (relay neurones), with cell bodies of motor nerves whose axons run out into the ventral roots
What is the spinal cord?
Nerve tracts running the length of the spinal cord interconnect the various reflex arcs and the brain.
What is white matter?
Made up of long nerve fibres running the length of the spinal cord.
What is grey matter?
Made up of motor nerve cell bodies and relay neurones
What are relay neurones?
Relays impulse from sensory neurones to motor neurone, not always present.
What is the ventral root?
Carries only motor nerve fibres from the spinal cord into the spinal nerve.
What are motor neurones?
Carries impulses from spinal cord to effector.
What are motor end plates?
Transfers impulse to effector organ.
What is the dorsal root?
Carries only sensory nerve fibres from the spinal nerve into the spinal cord.
What is the dorsal root ganglion?
Contains all cell bodies of sensory neurones
What is the mixed spina nerve?
Carries both motor and sensory fibres
What is cervical enlargement associated with?
Innervation of upper limbs
What is lumbar enlargement associated with?
innervation of lower limbs
What are the major descending pathways?
Corticospinal tract
What is the corticospinal tract?
White matter motor pathway initiating at cerebral cortex terminating on lower motor neurones and interneurones in the spinal cord, controlling movements and motor functions of limbs and trunk
What forms the corticospinal tract?
Upper motor neurones in primary motor cortex
Where does pyramidal decussation occur for the corticospinal tract?
Medulla
Where do corticospinal tract neurones arise from?
Precentral gyrus the primary motor cortex of the frontal lobe, Beta. cells
What are the major ascending pathways?
Dorsal columns
Spinothalamic
What sensations are concerned with the dorsal column pathway?
Fine touch, vibration and proprioception (position) from skin and joints
Where does decussation occur for the dorsal columns?
Medullary, ipsilateral below
What does the spinothalamic pathway associate with?
Pain , temperature and crude touch
Where are the ascending tracts located within the spinal cord?
Dorsal, occupy the white matter
What are upper motor neurone lesions associated with?
Stroke
What are lower motor neurone lesions associated with?
Motor neurone disease
Where does the corticobulbar tract originate from?
Primary motor cortex within the precentral gyrus and anterior part of the paracentral lobule
What is the function of the corticobulbar tracts?
Descending pathway responsible for innervation of the face, tongue, jaw & pharynx through the cranial nerves
Which cranial nerves are associated with the corticobulbar tract?
V (Trigeminal)
VII (Facial)
XI (Accessory)
XII (Hypoglossal)
What is somatotopy?
Point for point correspondence of a bodily region allocated to a specific point on the CNS
What is the vestibulospinal tract?
Provides information concerning head movement and position , mediates postural adjustments
What nucleus is associated with the vestibulospinal tract?
Cerebellum
What is the tectospinal tract?
Concerned with head and neck orientation, during eye movements
What is the reticulospinal tract?
Controls breathing and emotional motor function
What is the rubrospinal tract?
Innervates lower motor neurone of the upper limb
What are the first order neurones?
Cell body is located within the dorsal root ganglion, ascends on the ipsilateral side of the medulla, synapsing with secondary order neurones.
Where are second order neurones located?
Located in the medullary pyramids
Which dorsal column travels ipsilaterally transmitting signals from the upper limb (T6 and above)?
Along the cuneate tract
Which nucleus does the cuneate tract synapse with?
Nucleus cuneatus
Which dorsal column t transmits modalities of sensation from lower limbs (below T6)?
gracile tract
Which nucleus does the gracile tract synapse with?
Nucleus gracilis
Where are third order neurones located?
Thalamus
Where do third order neurones transmit sensory signals to?
From the thalamus to the ipsilateral primary sensory cortex
What sensory modalities are associated with the spinothalamic tract?
Pain, temperature and crude touch
Where does the spinothalamic tract decussate?
Within the spinal cord
What is the relationship between threshold of nerve axon and diameter?
Inversely proportional
Which axons are stimulated first by stimuli?
Largest diameter axons
What factors influence reduced conduction velocity?
Demyelination hypothermia, and increased pressure to the nerve bundle
