Central Nervous System Flashcards
What is the CNS composed of?
Brain: Forebrain - cerebral hemisphere + diencephalon Midbrain Hindbrain - Pons, Medulla + Cerebellum Spinal Chord
Name the lobes in the brain
Frontal Parietal Temporal Occipital Limbic Insular Cortex
Frontal lobe function
Regulate and incite motor function, language, cognitive functions(attention/memory)
Parietal Lobe function
Sensation, sensory aspects of language, spatial orientation and self-perception
Temporal lobe function
Processing auditory information
Occipital lobe function
Processing visual information
Limbic lobe function (and parts of brain it includes)
Includes amygdala, hippocampus, mamilliary body and cingulate gyrus
Concerned with learning, memory, emotion, motivation and reward
Insular cortex position and function
Lies deep within lateral fissure
Concerned with visceral sensations, autonomic control, interoception, auditory processing, visual-vestibular integration
Describe the layers of the meninges
Skin
Bone
Dura - thick composed of periosteal and meningeal (durable + dense) layers
Arachnoid - thin, transparent fibrous membrane
Pia mater - thin, translucent and mesh-like
Cerebrospinal fluid
Production, location, amount, removal, comparison to plasma
Produced in choroid plexus of lateral, 3rd and 4th ventricles
Occupies ventricular system and sub-arachnoid space
125ml volume and 500ml produced each day
Reabsorbed via arachnoid villi into superior Sagitta sinus l
Lower pH, less glucose, protein and potassium than plasma
Describe compositions of spinal chord with regards to nerves
8pairs of cervical nerves 12pairs of thoracic nerves 5pairs of Lumbar nerves 5pairs of Sacral nerves 1 pair of Coccygeal nerves
Nerves emerge through intervertebral foramina
Relationship between nerves and foramina changes:
Cervical nerves 1-7 emerge above vertebrae
Cervical nerves 8- Coccygeal nerves 1 emerge below vertebrae
Which parts of the spinal chord are enlarged and why?
Cervical chord enlargement - due to innervation of upper limbs
Lumbar chord enlargement - due to innervation of lower limbs
What is the major pathway for voluntary movement and what is it composed of?
Corticospinal tract:
Composed of upper motor neurons in primary motor cortex and lower motor neurons in brainstem and spinal chord
What are the major pathways for sensation?
Dorsal Column Pathway - fine touch, vibration and proprioception from the skin and joints
Spinothalamic Pathway - pain, temperature and crude touch from the skin
Difference between Descending and Ascending Tracts
Descending tracts are motor containing lateral corticospinal and ventral corticospinal tracts
Ascending tracts are sensory containing dorsal column, later and ventral spinothalamic tracts
Where are the upper and lower motor neurones located?
Upper motor neurons - primary motor cortex
Lower motor neurons - brain stem (head and neck muscles) or spinal chord (trunk and limb muscles)
Name and describe brainstem motor tracts
Vestibulospinal - provides info about head movement and position and mediate a postural adjustments
Tectospinal - orientation of head/neck during eye movement
Reticulospinal - control of breathing and emotional motor function
Rubrospinal - innervates lower motor neurons of the upper limb
Name the two principal ascending pathways
Dorsal column pathway and Spinothalamic pathway
What is the function of Dorsal column pathway?
Mechanical: Fine discriminative touch Pressure Vibration Proprioception
What is the function of Spinothalamic pathway?
Mechanical, Chemical & Thermal:
Crude touch
Pain
Temperature
Describe the Dorsal Column Pathway route
Fibres enter via dorsal horn and enter the ascending dorsal column pathways
Info conveyed from lower limbs and body (below T6) travel ipsilaterally along gracile tract
Info conveyed from upper limbs and body (above T6) gravel ipsilaterally along the cuneate tract
3 neurones in Sensory pathways
First one has cell body in dorsal root ganglion
Second one has cell body in medulla (gracile/cuneate nucleus)
Third neurone is found in the thalamus
What determines the difference between using the dorsal column pathway and the Spinothalamic pathway?
The second order neurone’s location of their cell bodies
Location of 3rd order neurons
From thalamus project to the Somatosensory Cortex
Somatosensory homunculus
Size of somatotopic areas is proportional to density of sensory receptors in that body region
Describe the Spinothalamic pathway
Pain and temperature sensations ascend within the lateral Spinothalamic tract
Crude touch ascends within the anterior Spinothalamic tract
Primary neurone comes in through the dorsal horn it synapses onto the second order neurone which crosses over onto the opposite side of the body and travels up the contralateral side synapsing on to the third order neurone in the thalamus
Neurone synapses in dorsal horn (in relation to Spinothalamic tract)
Primary afferent axons terminate upon entering the spinal chord and second order neurons decussate immediately in the spinal chord and form the Spinothalamic tract which then terminates in the thalamus
