Central Nervous System Flashcards
The nervous system can be split into two nervous systems
Central nervous system and peripheral nervous system
What is the CNS composed of
Brain and spinal cord
What is the PNS composed of
Nerves ( cranial and spinal) and ganglia outside the brain and spinal cord
3 sections of the brain
Forebrain
Midbrain
Hindbrain
What is the forebrain made up of
Cerebral hemisphere
Diencephalon
What is the hindbrain made up of
Pons
Medulla
Cerebellum
What does the brainstem consist of
Midbrain
Pons
Medulla
What does the frontal lobe do
Regulate and initiate motor function , language, cognitive functions ( executive function (e.g. planning), attention , memory)
Parietal lobes function
Sensation ( touch , pain) , sensory aspects of language, spatial orientation and self perception
Temporal lobe
Processing auditory information
Occipital lobe
Processing visual information
What does the limbic lobe consist of
Amygdala, hippocampus , mammillary body and cingulate gyrus
What does the limbic system do
Concerned with learning, memory , emotion , motivation and reward
Where is insular cortex located
Deep within the lateral fissure
What does the insular cortex do
Concerned with visceral sensations, autonomic control, and interception , auditory processing , visual vestibular integration ( balance between the sensation from our eyes and the sensation of our balance)
The three layers of the meninges
Dura
Arachnoid
Pia
Arachnoid matter
Thin , translucent, mesh like( 2 cell thick)
Arachnoid matter
Thin , transparent , fibrous membrane
Dura
Thick composed of 2 layers
Periosteum - layer of periosteum
Meningeal- durable, dense fibrous membrane
How is a Dural venous sinus formed
At various points in the brain , the meningeal layer peels away from the periosteal layer to form the Dural venous sinus
Where is CSF formed
In the choroid plexus of lateral, 3rd and 4th ventricles
Where is CSF situated
Occupies ventricular system and the sub arachnoid space
Where is CSF reabsorbed
Reabsorbed via arachnoid villi ( granulation) into superior saggital sinus
Difference between CSF and Plasma
Lower pH, less glucose, protein and potassium than plasma
What is a mixed spinal nerve
Point at which ventral and dorsal rootlets have combined and so the motor and sensory nerves are in the same nerve
Dorsal root ganglion
Contain cell bodies of primary sensory neurons they have endings in skin and joints
White matter
Filled with axons travelling superiorly and inferiorly
Dorsal
Sensory fibres
Ventral
Motor fibres
Are motor fibres towards anterior or posterior side
Anterior as the motor root is in the ventral horn
Spinal cord
Composed of segments – each gives rise to a pair of mixed spinal nerves
Different regions of the spinal-cord
Cervical Thoracic Lumbar Sacral Coccygeal
How many nerves in the cervical region
Eight
How many nerves in the thoracic region
12
How many nerves in the lumbar region
Five
How many nerves in the sacral region
5
How many nerves in the coccygeal region
1
Where do nerves emerge through
Intervertebral foramina
Nerves C1-C7 emerge
Above vertebrae
Nerves C8-CO2 emerge
Below vertebrae
Where are the two places in the spinal-cord where there are enlargements
Cervical enlargement
Lumbar enlargement
Why is there a cervical enlargement
To allow for the innervation of the upper limbs
Why is there an enlargement of the lumbar region
To allow for the innervation of the lower limbs
Major descending pathway
Major pathway for voluntary movement is the corticospinal tract
Corticospinal tract and motor neurones
The corticospinal tract is composed of upper motor neurons in the primary motor cortex and lower motor neurons in the brainstem and spinal cord
What do the lower motor neurons in the brain stem supply
Muscles of the head and neck
What do you motor neurons in the spinal-cord supply
They innervate the rest of the body and limbs
What is the difference between upper and lower motor neurones
The nerves that send messages between the cerebral cortex and the spinal-cord are called upper motor neurones and those that relay messages from the spine to the muscles are called lower motor neurons
What are the two major ascending pathways
Dorsal column pathway
Spinothalamic tract
Dorsal column pathway
Fine touch vibration and proprioception ( position) from the skin and joints, pressure
Spinothalamic tract
Pain temperature (and crude touch) from the skin
Which Part of the spinal-cord does the dorsal column pathway occupy
Posterior aspect
Where is the primary motor cortex located
Precentral gyrus
How many neurons are involved in the corticospinal tract
2( upper motor neurone and lower motor neurone )
Where does desuccation occur in the corticospinal tract
85% of fibres decussate in the medulla
Implications of the decussation of the corticospinal tract
As it Decussates in the medulla (1st neuron Decussates) the damage to the spine is ipsilateral to the symptoms experienced
Corticobulbar tract
Conducts impulses from the brain to the cranial nerves these nerves control the muscles of the face and neck and are involved in facial expression mastication swallowing and other motor functions
Difference between pyramidal and extra pyramidal tracts
Pyramidal tracts for example corticospinal and corticobulbar tract control voluntary control of the musculature of the body and face
Extra pyramidal tracts are responsible for the in voluntary and automatic control of all musculature such as muscle tone balance posture and locomotion
Examples of extra pyramidal tracts
Vestibulospinal
Tectospinal
Reticulospinal
Rubrospinal
Vestibulospinal tract
Provides information about head movement and position and mediates postural adjustments
Tectospinal tract
Orientation of the head and neck during Eye movements
Reticulospinal tract
Control of breathing and emotional motor function
Rubrospinal tract
Innovates lower motor neurons of the upper limb but this has been largely taken over by the corticospinal tract in humans and only becomes active in humans after injury to the corticospinal tract or lesions in the corticospinal tract
Where is the primary somatosensory cortex located
Post central gyrus
What are the two principal ascending pathways
Dorsal column pathway and the spinothalamic pathway
Dorsal column pathway
Fibres enter via the dorsal horn and enter the ascending dorsal column pathway
Information conveyed from the lower limbs and body ( below T6) travel ipsilaterally along the gracile tract
Information Conveyed from upper limbs and body and therefore above T6 travel ipsilaterally along the cuneate tract
How many neurons are involved in the dorsal column pathway
3
Where do the tracts of the dorsal column pathway synapse
First synapse of the gracile tract is in the gracile nucleus of the medulla
First synapse of the cuneate tract is in the cuneate nucleus in the medulla
What happens in the dorsal column pathway after the first synapse has occurred in the medulla
Second order axons or neurons decussate in the caudal medulla they then form the contralateral medial Lemniscus tract which then synapses in the thalamus
What are happens after decussation has happened in the dorsal column pathway
Third order neurons from the thalamus project to the somatosensory cortex the size of the somatotopic areas is proportional to the density of sensory receptors in that body region ( somatosensory homunculus )
Lateral spinothalamic tract
Pain and temperature
Anterior spinothalamic tract
Crude touch
What do the first order neurons do after entering spinal cord in the spinothalamic tract
Primary afferents axons terminate upon entering the spinal-cord . seconds order neurons decussate immediately in the spinal cord and form the spinothalamic tract. So contralateral flow
What happens to the second order neurone in the spinothalamic tract
Terminate in the thalamus
What happened to the third order neurons in the spinothalamic tract which come from the thalamus
Project to the somatosensory cortex
