Formative Assessment 24.02.23 Flashcards
How is blood drained from the brain (venous drainage)?
The straight sinus receives venous blood from the inferior sagittal sinus and the great cerebral vein as it is a continuation of these veins
Where are the sinuses located that drain the blood from the brain?
In between the two layers of dura mater: the periosteal and meningeal layers
Where does the cavernous sinus receive blood from?
The orbit
Which sinus reabsorbs cerebrospinal fluid?
The superior sagittal sinus
How is venous blood from the cerebral circulation returned to the heart?
Via the internal jugular veins
Where are the straight, superior and inferior sagittal sinuses found?
In the falx cerebri of the dura mater
Where does the superior and inferior sagittal sinus and straight sinus converge?
At the confluence of sinuses
From the confluence, which sinus (1) continues into the what sinus (2) into the internal jugular vein?
(1) The transverse sinus continues bi-laterally and curves into the (2) sigmoid sinus into the IJV
How does blood travel from the cavernous sinus to the internal jugular vein?
Via the superior and inferior petrosal sinuses
What does the superior cerebral vein drain?
Drains the superior surface, carrying blood to the superior sagittal sinus
What does the superficial middle cerebral vein drain?
Drains the lateral surface of each hemisphere, carrying blood to the cavernous sinus
What does the inferior cerebral vein drain?
Drains the inferior aspect of each cerebral hemisphere, depositing blood into cavernous and transverse sinuses.
What does the superior anastomotic vein do?
Connects the superficial middle cerebral vein to the superior sagittal sinus.
What does the inferior anastomotic vein do?
Connects the superficial middle cerebral vein to the transverse sinus.
Where will the left anterior cerebral artery carry blood to?
The motor cortex of the right leg
What is the middle cerebral artery a direct continuation of?
The internal carotid artery
What is the internal capsule?
The internal capsule is a two-way tract for the transmission of information to and from the cerebral cortex.
What would be a likely stroke if it affected the internal capsule?
It would usually be haemorrhagic as it affects the lenticulostriate artery
What will a stroke affecting one side of the motor or sensory cortex result in?
A contra-lateral neurological deficit
Where does the primary motor cortex occupy?
The pre-central gyrus
What arteries supply the primary motor cortex?
The middle cerebral artery and the anterior cerebral artery
How are muscles of the lower limbs and face represented in the primary motor cortex?
Muscles of the lower limbs are represented medially, whereas the muscles of
the face are represented laterally
Which Brodmann’s area is the primary motor cortex?
4
Where do the corticospinal tracts pass?
They pass between the basal ganglia and the thalamus to then enter the cerebral peduncle and then the internal capsule
Where does the lateral corticospinal tract decussate at?
The medullary pyramids
Where will a stroke have the worst affects - in the motor cortex or the internal capsule?
A stroke affecting the internal capsule will result in a greater neurological deficit than the motor cortex
Which area of the brain produces an abnormal rhythmical output in Parkinson’s disease?
The basal ganglia
Where are axons of the upper motor neurons located?
In the lateral white matter of the spinal cord
Where are cell bodies of the LMNs located?
In the ventral horn of the spinal cord
Where are the cell bodies of the UMNs located (lateral/ventral)?
They pass lateral to ventral at appropriate spinal level
Do LMNs leave the spinal cord anteriorly or posteriorly?
Anteriorly (and ventrally)
Is the lateral and anterior corticospinal tract crossed or uncrossed?
Lateral is crossed as it decussates in the medullary pyramids
Anterior is uncrossed
What does the corticospinal tract control?
Muscle and fine control
What side of the body does the anterior corticospinal tract supply?
Mainly supplies the side of the body contralateral to the originating brain hemisphere
What is the tectospinal tract involved with?
Head turning to visual stimulus (superior colliculus)
What is the vestibulospinal tract involved with?
Balance and posture and keeping head upright an it consists of uncrossed fibres
What does the reticulospinal tract facilitate or inhibit: the ascending or descending tracts/
The reticulospinal tract originates from cells found in the pons and the medulla and may
act to facilitate or inhibit the activity of various descending tracts
Is the rubrospinal tract crossed or uncrossed and is it highly or less skilled?
It is crossed and a less skilled version of the lateral corticospinal tract
How are the fibres of the corticospinal tract organised?
Somatotopically - this means fibres concerned with lower limbs are located laterally and those with upper are located more medially
What are muscle spindles?
- Found in skeletal muscles
- Composed of intrafusal muscle fibres
- Two ends of spindle are contractile and middle is non-contractile
How does the golgi tendon organ function?
Afferent impulses from the Golgi tendon organ result in the inhibition of alpha motor
neurons of the muscle fibres associated with the activated Golgi tendon organ to
regulate muscle tension at a normal range and also to protect the muscle from overload
What does cutaneous and phasic receptors mean?
Some cutaneous receptors are phasic (rapidly adapts) in response and others tonic
(slowly adapts)
- Use this to talk about skin receptors
Is the dorsal column-medial lemniscal system characterised by slow or fast conduction velocities?
Fast conduction velocities
What does the DCML carry information about?
About touch and proprioception
Where does the DCML lie?
In the ventral white matter of the spinal cord (dorsal)
How are fibres in the dorsal columns arranged?
Topographically - spatial relationship between distribution of neural receptors on a body
Where does the DCML decussate?
In the medulla - then goes to thalamus and then the somatosensory cortex
When the plasma membrane is in a resting potential which channels are open?
- More open K+ channels than Na+ so there is a negative resting potential inside with respect to the outside
- The membrane potential at rest is mainly governed by K+ ions
When does an action potential occur?
Occurs as sodium channels open in the membrane resulting in the membrane
potential briefly becoming more positive on the inside with respect to the
outside
When do voltage gated Na+ channels close?
After a particular time not in response to a membrane potential
What is a refractory period?
The relative refractory period is a time during which a second stimulus, needs to be
stronger to produce a second action potential
What are the two refractory periods?
- The absolute refractory period (second stimulus will not excite neurone)
- Then the relative refractory period (a stronger than normal stimulus is needed to elicit neuronal excitation)
What channel causes the release of neurotransmitters?
The opening of calcium channels
