Lecture 7: Central Nervous System Flashcards
What is the CNS composed of?
Brain (cerebrum, cerebellum, brainstem) and spinal cord
What is the brain comprised of?
forebrain, midbrain and hindbrain
What is the forebrain composed of?
- cerebrum
- diencephalon
What is the diencephalon?
posterior part of forebrain containing epithalamus, thalamus, hypothalamus, and ventral thalamus and the third ventricle.
What is the hindbrain composed of?
- pons
- medulla
- cerebellum
What is the brainstem composed of?
- midbrain
- pons
- medulla
What functions does the frontal lobe have?
- regulating and initiating motor function
- language
- cognitive functions
- executive function e.g. planning, multitasking
- attention
- memory
What functions does the parietal lobe have?
- sensation (touch, pain)
- sensory aspects of language,
- spatial orientation
- self-perception
What functions does the temporal lobe have?
processing auditory information
What functions does the occipital lobe have?
processing visual information
What separates the frontal and parietal lobe?
central sulcus
What separates the frontal and temporal lobe?
lateral fissure
What separates the parietal and occipital lobes?
parieto-occipital fissure
What is the limbic system/lobe?
- Collection of nuclei involved in learning, memory, emotion, motivation and reward
- includes: amygdala, hippocampus, mamillary body, and cingulate gyrus
What is the insular cortex?
- Lobe that lies deep within lateral fissure
- concerned w/visceral sensations, autonomic control, and interoception, auditory processing, visual-vestibular integration
What are the 3 layers of the meninges?
- dura (thick, 2 layers)
- arachnoid (thin, transparent, fibrous membrane)
- pia (thin, translucent and mesh-like)
What are the 2 layers of the dura mater?
- periosteal: layer of periosteum
- meningeal: durable, dense fibrous membrane
Where is cerebrospinal fluid produced?
In choroid plexus of lateral, 3rd and 4th ventricles
What space does CSF occupy?
ventricular system and sub-arachnoid space
How is CSF reabsorbed?
via arachnoid villi (granulations) into superior sagittal sinus
What is different between CSF and plasma?
CSF has lower pH, less glucose, less protein and potassium than plasma
What leaves each segment of the spinal cord?
a pair of mixed spinal nerves
Which spinal nerves are conveyed by the dorsal root?
sensory/afferent
Which spinal nerves are conveyed by the ventral root?
motor/efferent
What is a mixed spinal nerve?
afferent and efferent nerves bundled together
What is the dorsal root ganglion?
swelling containing cell bodies of sensory nerve
What is grey matter?
collection of cell bodies (soma)
What is white matter?
tracts of axons
What is the posterior ramus?
smaller version of mixed spinal nerve that innervates muscles and skin down back of spine
What are do the dorsal and ventral roots split into?
dorsal rootlets and ventral rootlets
How is grey matter arranged in the spinal cord?
Shaped like butterfly with dorsal horn and ventral horn
What is the spinal cord composed of?
segments
What are the 5 areas of spinal cord?
- cervical
- thoracic
- lumbar
- sacral
- coccygeal
How many segments are in the cervical section of the spinal cord?
8
How many segments are in the thoracic section of the spinal cord?
12
How many segments are in the lumbar section of the spinal cord?
5
How many segments are in the sacral section of the spinal cord?
5
How many segments are in the coccygeal section of the spinal cord?
1
Where do the nerves emerge through?
intervertebral foramina
Where does the relationship between nerves and foramina change?
cervical and thoracic regions
Where do nerves C1-C7 emerge?
above vertebrae
Where do nerves C8-Co1 emerge?
below vertebrae
How many vertebrae do we have?
30
How many pairs of nerves do we have in the spinal cord?
31 pairs
What are intervertebral foramina?
gaps between vertebrae
What is the cervical enlargement?
widened area of spinal cord that innervates upper limbs
What is the lumbar enlargement?
widened area of spinal cord that innervates lower limbs
What is the major pathway for voluntary movement?
the corticospinal tract
this is a major descending pathway
What is the corticospinal tract composed of?
upper motor neurons in primary motor cortex and lower motor neurons in brainstem and spinal cord
What are the main pathways for sensation?
- dorsal column pathway
- spinothalamic tract
What is the dorsal column pathway for?
-fine touch, vibration and proprioception (position) from skin and joints
What is the spinothalamic pathway for?
- pain, temp and crude touch from skin
How many sets do we have of each ascending and descending pathway?
2 sets, one on each hemisphere of brain
Where is the primary motor cortex located?
On the pre-central gyrus
What is somatotopy?
representing areas on the brain by the region of the body they control (in terms of the systematic set of movements broadly similar in everyone)
Where is the upper motor neurone located?
in the primary motor cortex
Where is the lower motor neurone located?
in the spinal cord
What does the lateral corticospinal tract control?
movement of limbs
What does the anterior corticospinal tract control?
movements of axial muscles (of the trunk)
What do most of the nerve fibres in a nerve tract do?
cross over in medulla (decussate)
What is the corticobulbar tract?
The corticobulbar tract is a descending pathway responsible for innervating several cranial nerves, and runs in parallel with the corticospinal tract
What are the brainstem motor tracts?
- vestibulospinal
- tectospinal
- reticulospinal
- rubrospinal
What does the vestibulospinal tract do?
provides information about head movement and position and mediates postural adjustments
What does the tectospinal tract do?
orientation of head and neck during eye movements
What does the reticulospinal tract do?
control of breathing and emotional motor function
What does the rubrospinal tract do?
innervate lower motor neurons of the upper limb
Where is the primary somatosensory cortex?
in the post-central gyrus
What are the 2 principal ascending pathways?
- dorsal (posterior) column pathway
- spinothalamic pathway
What are the functions of the dorsal column pathway?
mechanical:
- fine discriminative touch
- pressure
- vibration
- proprioception
What is proprioception?
perception or awareness of the position and movement of the body.
What are the functions of the spinothalamic pathway?
mechanical, chemical and thermal:
- crude touch
- pain
- temp
How do fibres enter the ascending dorsal column pathways?
fibres enter via the dorsal horn and enter the ascending dorsal column pathways
How is information conveyed from lower limbs and body (below T6) by the dorsal column pathway?
travel ipsilaterally along gracile tract
How is information conveyed from upper limbs and body (above T6) by the dorsal column pathway?
travel ipsilaterally along cuneate tract
Where do the tracts synapse?
in the medulla
Where is the first synapse of the gracile tract?
in the gracile nucleus
Where is the first synapse of the cuneate tract?
in the cuneate nucleus
Where do second order axons decussate?
in the caudal medulla
What do the second order axons form?
contralateral medial lemniscus tract
Where do the second order axons synapse?
in the thalamus
Where do 3rd order neurons from the thalamus project to?
To the somatosensory cortex
What is the size of somatotopic areas proportional to?
density of sensory receptors in that body region
In which tract of the spinothalamic (anterolateral) pathway do pain and temp sensations ascend?
within the lateral spinothalamic tract
In which tract of the spinothalamic (anterolateral) pathway does crude touch ascend?
within the anterior spinothalamic tract
Where do the neurons synapse?
in dorsal horn
Where do the primary afferent axons terminate?
upon entering the spinal cord
Where do second order neurons immediately decussate?
in the spinal cord and form the spinothalamic tract
Where do 2nd order neurons terminate?
in the thalamus
Where do 3rd order neurons from the thalamus project to?
to the somatosensory cortex
