The Central Nervous System Flashcards
What are the components of the nervous system?
Nervous system can be divided into central nervous system (CNS) and peripheral nervous system (PNS)
What is the CNS?
brain and spinal cord
What is the PNS?
nerves (cranial and spinal) and ganglia outside brain and spinal cord
What is the brain composed of?
forebrain, midbrain, hindbrain
What is the breakdown of the forebrain, midbrain and hindbrain?
Label this diagram. (mid-saggital view)
What does the frontal lobe control?
Regulating and initiating motor function, language, cognitive functions (executive function [e.g. planning], attention, memory)
What is the role of the parietal lobe?
Sensation (touch, pain), sensory aspects of language, spatial orientation and self- perception
What is the role of the temporal lobe?
Processing auditory information
What is the role of the occipital lobe?
Processing visual information
What is the limbic lobe?
limbic lobe includes the amygdala, hippocampus, mamillary body, and cingulate gyrus
Concerned with learning, memory, emotion, motivation and reward
What is the insular cortex?
Insular cortex (lobe) lies deep within lateral fissure
Concerned with visceral sensations, autonomic control, and interoception, auditory processing, visual- vestibular integration (what we see and what our organs feel)
interoception= sensations within the body e.g., hunger
What are the three layers of the meninges?
Dura, arachnoid, pia mater (DAP)
What is the dura?
thick,
composed of 2 layers periosteal - layer of periosteum
meningeal - durable, dense fibrous membrane
What is the periosteum?
the membrane of blood vessels and nerves
What is the arachnoid layer?
thin, transparent, fibrous membrane
What is the pia mater?
thin, translucent & mesh-like
- 2 cells thick
Where is CSF produced?
in choroid plexus of lateral, 3rd and 4th ventricles
What does CSF occupy?
Occupies ventricular system and sub- arachnoid space
How much CSF is there and how much is produced each day?
~125 ml volume and 500 ml produced each day
How is CSF reabsorbed?
Reabsorbed via arachnoid villi (granulations) into superior sagittal sinus
How would you compare CSF and plasma?
Lower pH, less glucose, protein and potassium than plasma
What is the spinal cord anatomy?
Dorsal rootlets
Dorsal root
Dorsal root ganglion
Mixed spinal nerve
Dorsal horn
grey matter
Ventral horn
White matter
Ventral rootlets
Ventral root
Describe the spinal cord.
Composed of segments – each gives rise to a pair of mixed spinal nerves.
Cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1).
Where do nerves emerge through?
intervertebral foramina
What is the relationship between nerves and foramina?
Relationship between nerves and foramina changes between cervical and thoracic regions.
Nerves C1-C7 emerge above vertebrae
Nerves C8-Co1 emerge below vertebrae
What is the posterior and ventral root?
posterior= dorsal root
ventral= anterior
What is the relationship between the spinal cord and spinal column?
The spinal column outgrows the spinal cord
What is cervical enlargement for?
innervation of upper limbs
What are lumbar enlargements for?
Innervation of lower limbs
Why are lumbar spinal cord larger?
due to more muscles
Describe the spinal cord enlargements…
What are the major descending pathways?
Major pathway for voluntary movement 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 major ascending pathways?
Main pathways for sensation are the dorsal column pathway and the spinothalamic tract
Dorsal column pathway is for fine touch, vibration and proprioception (position) from the skin and joints
Spinothalamic pathway is for pain, temperature (and crude touch) from the skin
Describe the spinal cord anatomy.
Descending tracts= motor
Ascending tracts= sensory
Descending= lateral corticospinal tract, ventral corticospinal tract
ascending= dorsal column, lateral spinothalamic tract, ventral spinothalamic tract
What is crude touch?
Less localised touch
What are the motor pathways- corticospinal tract?
Pre-central gyrus
Central sulcus
post-central gyrus
Primary motor cortex
What is somatotopy?
Somatotopy is the point-for-point correspondence of an area of the body to a specific point on the central nervous system
Where is the upper and lower motor neurone?
lower spinal cord
upper in the primary motor cortex
What plane is this?
coronal
Describe the structure of the corticospinal tract.
Approximately 85% of fibres decussate (cross) in the medulla
What makes up the corticobulbar tract?
Collection of cell bodies that sends their nerve fibres out to muscles of the face
Oculomotor nucleus
Trochlear nucleus
Trigeminal motor nucleus
Abducens nucleus
Facial nucleus
Hypoglossal nucleus
(3,4,5,6,7,12)
What is the role of the nuclei in the corticobulbar tract?
Oculomotor nucleus= extraocular muscles
Trochlear nucleus= extraocular muscles
Trigeminal motor nucleus= muscles of mastication
Abducens nucleus= extraocular muscles
Facial nucleus= muscles of facial expression
Hypoglossal nucleus= muscles of the tongue
What plane section is this? (also look at the placement of the things in the photo e.g., corticospinal tract)
Horizontal
What are the brainstem motor tracts?
Vestibulospinal
Tectospinal
Reticulospinal
rubrospinal
What is the vestibulospinal brainstem motor tract?
provides information about head movement and position and mediates postural adjustments
What is the tectospinal brainstem motor tract?
orientation of the head and neck during eye movements
What is the reticulospinal brainstem motor tract?
preparatory and movement-related activities, postural control
What is the rubrospinal brainstem motor tract?
innervate lower motor neurons of the upper limb
What are the somatosensory pathways?
a complex network of nerves that transmit sensory information
What are the structures involved in somatosensory pathways?
Pre-central gyrus
Central sulcus
Post-central gyrus
primary somatosensory cortex
What are the 2 principle ascending pathways?
Dorsal (posterior) column pathway
Spinothalamic pathway
What is the Dorsal (posterior) column pathway for?
Mechanical:
Fine discriminative touch
Pressure
Vibration
Proprioception
What is the spinothalamic pathway for?
Mechanical, chemical & thermal:
Crude touch
Pain
Temperature
Describe the dorsal column pathway.
Fibres enter via the dorsal horn and enter the ascending dorsal column pathways
Information conveyed from lower limbs and body (below T6) travel ipsilaterally along the gracile tract
Information conveyed from upper limbs and body (above T6) travel ipsilaterally along the cuneate tract
What are the types of sensory neurones and what are their differences?
primary=> comes into the cord
secondary=> crosses over
tertiary=> from thalamus to the brains to the sensory cortex
Where is the first synapse of the gracile tract and cuneate tract?
gracile nucleus
cuneate nucleus
What do the blue bumps mean and what is the difference between fasciculus gracilis/ cuneatus?
4 bumps= arm and leg
2 bump= j leg/ arm
gracilis= lower limbs/ lower extremities/ legs
cuneatus= upper extremities…
What are second order axons?
Second order axons decussate in the caudal medulla
Form the contralateral medial lemniscus tract
Synapse in the thalamus
What are 3rd order neurones?
3rd order neurons from the thalamus project to the
somatosensory cortex
Size of somatotopic areas is proportional to density of sensory receptors in that body region (somatosensory homunculus)
What is the purpose of the spinothalamic (anterolateral) pathway?
Pain and temperature sensations ascend within the lateral spinothalamic tract
Crude touch ascends within the anterior spinothalamic tract
Where do primary afferent axons terminate?
terminate upon entering the spinal cord
When do second order neurones decussate?
Second order neurons decussate immediately in the spinal cord and form the spinothalamic tract
Where do 2nd order neurones terminate?
in the thalamus
What do 3rd order neurones do?
3rd order neurons from the thalamus project to the somatosensory cortex
How is the CNS protected?
meningeal coverings
brain and spinal cord are bathed in cerebrospinal fluid
Enlargements of the spinal cord are associated with what?
innervation of limbs
Give an overview of descending and ascending pathways?
Major descending pathways for voluntary movements, corticospinal and corticobulbar tracts
Major ascending pathway for light touch, proprioception and vibration is the dorsal column pathway
Major ascending pathway for crude touch, pain and temperature sensations is the spinothalamic pathway
