Exam 3 Flashcards
What does the vestibular system involve?
The motor system, hippocampus, and cerebral cortices
Name the functions of the vestibular system.
- Provides ability to control body and eyes in relation to the environment
- Helps with balance control programming
- Helps keep fluidity by controlling gaze
Why is the ear important to the vestibular system?
It is a vestibular organ made up of 5 organs
What does the ear do?
Helps understand which way head moves relative to our body and environment
Name the 5 organs making up the ear (vestibular organ).
3 semicircular canals
2 otolith organs
Name the fluid that fills all parts of the vestibular organ
Endolymph
What two parts of the internal ear have cells that respond to linear/translational movement?
Utricle & Saccule
Define linear/translational movement.
Movement shared between head and body, or when head and body move at the same rate
_____ responds to translational head movement and orientation relative to gravity
Otolith organs
What special cells are found in the utricle and sacculae?
Maculae
Define maculae
Special cells that pick up direct movement
Where in the otolith is maculae found?
Utricle & sacculae
The semicircular canals respond to _____ movement.
Rotational
What is the difference between translational/linear movement and rotational movement?
Rotational - head and body move differently
Translational - head and body move together
Name the 3 planes that organize the semicircular canals
Anterior, posterior, lateral
What special cells pick up movement in the semicircular canals?
Ampulla
Name the 5 components of the vestibular system
- Sensory receptors
- Nuclei
- Ocular reflex
- Spinal tract
- Vestibulothalamocortical network
Name the main sensory receptor of the vestibular system.
Hair cells
Where are hair cells in the vestibular system found?
Inside maculae and ampulla
What is found at the top of a hair cell?
Kinocilium
Relate the kinocilium to the vestibular system
Kinocilium makes the hair cells good at detecting movement of endolymph
What 2 liquid movements do the kinocilium detect?
Left to right & Right to left
* towards shortest or longest hair
Describe what occurs when the voltage of the hair cell changes in the direction of the largest hair.
The cell will depolarize, raising the resting potential (-60 mV) towards -20 mV. There is an increase in sharing neurotransmitters and a decrease in the firing rate to 10 spikes/second.
Describe what occurs when the voltage of the hair cell changes in the direction of the shortest hair.
The cell will hyperpolarize, lowering the resting potential (-60 mV) towards -100 mV. There is a decrease in sharing neurotransmitters and an increase in firing rate to 180 spikes/second.
Where are hair cells found?
Otolith & semicircular canals
The difference in firing rate of the hair cells is the brain”s ______.
Understanding of head rotation
Describe the difference in hair cell excitation between turning the head and tilting the head.
When rotating the head, the ampulla will excite in correlation with the direction (i.e. left turn excites left ampulla). When tilting the head, the kinocilium will not correlate with the direction (i.e. left tilt excites right kinocilium).
What movement does the otolith organ respond to?
Linear/Translational - body moves with head
What movement does the semicircular canal respond to?
Rotational - head moves independent of body
Relate the vestibular nuclei to information transmission.
Information detected from firing rate is sent to brainstem via vestibular nerve, then is sent to vestibular nuclei
Name the 4 types of vestibular nuclei
- Superior
- Lateral
- Inferior
- Medial
Name the projections of the vestibular nuclei and name the two most important.
1. Oculomotor nuclei
- Vestibulocerebellum
3. Spinal cord
- Reticular formation
- Thalamus
Name the functions of the vestibular nuclei
- Processes positional & movement info to help control visual & postural reflexes
- Crosses via commissural fibers, which allow info on left/right side of the body to shared
What does the vestibulo-ocular reflex do?
It stabilizes the head during movement
Name the function of the vestibulo-ocular reflex.
Helps control your gaze if there’s head movement
* When head twists, it keeps constant gaze on subject
Name the importance of the vestibulospinal tracts.
It connects the vestibulonuclei with the spinal cord
Name the functions of the vestibulospinal tracts.
- Critical for postural control
- Excites extensor muscles by ensuring you don’t fall over to maintain gaze)
- Coordinates head movements & axial muscles
Name the vestibulospinal tracts.
Lateral & Medial
Describe the vestibulothalamocortical network
It is a set of connections of vestibular nuclei to the thalamus then finally to the cortex
How does the vestibulothalamocortical network function?
Aids in conscious perception of movement and spatial environment
How is the vestibulothalamocortical network important for cognitive function?
The brain is able to combine visual and somatosensory information to make more detailed predictions or imaginations
Name the 3 meninges of the brain
Dura
Arachnoid
Pia
What are the functions of the meninges?
- Cover and protect CNS
- Protect blood vessels
- Contain CSF
- Form skull partitions
Name the function of the subdural and subarachnoid spaces
Have the ability to partition blood, if there is a leakage (e.g. hemorrhaging)
Name the functions of cerebrospinal fluid.
- Buoyancy to prevent crushing
- Contains nutrients
- Contains more immune cells after CNS injury
Where does CSF originate from?
The first & second ventricles in the choroid plexus
Describe the direction of CSF flow
- Made in choroid plexus in lateral ventricles
- To 3rd ventricle
- To 4th ventricle
- Down dorsal spinal cord
- Up ventral spinal cord
- Around cortex and brain
- Drains into sagittal sinus
- Ends in the confluence of the sinus
Name the landmarks of the brain.
Central sulcus
Lateral sulcus
Longitudinal fissure
Corpus callosum
4 lobes (frontal, temporal, parietal, occipital)
Define the central sulcus
Divides frontal and parietal lobes & pre-/post-central gyrus
Define the lateral sulcus
Divides temporal lobe from the frontal and parietal lobes
Define the corpus callosum
A white matter bundle between hemispheres
Describe the functions of the frontal lobe
- Higher cognitive thinking
- Hold & manipulate memory
- Abstract thought
- Goal behavior
Describe the functions of the parietal lobe
- Associative integration center
- Manipulation & coordination of things
- Memory and attention
Define the functions of the occipital lobe
- Visual information
Describe the functions of the temporal lobe
- Perception & memory
- Anything categorical (e.g. faces)
Describe what occurs if there is damage to the corpus callosum
The brain is split, possibly forming 2 personalities
Name the 6 layers of cortex
- Molecular
- External Granular Layer
- External Pyramidal Layer
- Internal Granular Layer
- Internal Pyramidal Layer
- Multiform
Describe the molecular layer of the cortex
Most superficial layer to skull that has short corticocortical association fibers that helps receive & give info to other cortices in the same hemisphere
Describe the external granular layer of the cortex
Has cross-hemisphere fibers and helps connect the hemispheres
Describe the external pyramidal layer of the cortex
Has cross-hemisphere fibers and pyramidal neurons
Describe the internal granular layer of the cortex
Input layer of cortex that receives thalamocortical projects and sensory info
Describe the internal pyramidal layer of the cortex
“Upper motor neurons” that projects pyramidal fibers to subcortex and spinal cord that is important in voluntary movement & where the corticospinal tract begins
Describe the multiform layer of the cortex
It projects to the cortex and thalamus
Describe the appearance and characteristics of pyramidal neurons
They have very long triangular projections and only deal w/ glutamate. They can only be excitatory and make up corticospinal neurons.
Describe the appearance and characteristics of non-pyramidal neurons
They have shorter projections that transmit pyramidal signals to nearby neurons. They are spherical, function as interneurons, and can be both excitatory and inhibitory
Where can you find pyramidal neurons?
Their bodies are in layers 3, 4, & 5, while their axons are in all 6 layers
The pre-central gyrus is dedicated to ____ cortex.
Primary motor cortex
The post-central gyrus is dedicated to _____ cortex.
Primary somatosensory cortex
What occurs with damage to the frontal lobe?
Drastic changes in personality, social cooperation, and managing oneself socially
* e.g. Phineas Gage
Name the two areas of the brain important for speech
Broca’s & Wernicke’s area
Describe the location and importance of Broca’s area
Found anterior to pre-central gyrus & is vital for speech production
Describe the location and importance of Wernicke’s area
Found superior to tempoparietal junction & is vital for speech comprehension
Name the function of the hippocampus
Plays a role in memory and forming new memories
What occurs with hippocampus damage/removal?
Less seizures & inability to form new memories
* e.g. Henry Molaisson
Define the 2 types of amnesia
Anterograde - inability to form new memories post-injury
Retrograde - inability to recall memories pre-injury
In the motor system hierarchy, what contributes to the development of motor development?
Parietal/premotoor/supplementart motor cortices
Primary motor cortex
Brainstem
Spinal cord
In the motor system hierarchy, what refines movement?
Basal nuclei
In the motor system hierarchy, the cerebellum aids in…
error reduction and accuracy
The primary motor cortex is where ____ is initiated
The motor program for specific movements
Locate the primary motor cortex
Anterior to the central sulcus on the pre-central gyrus
The primary motor cortex dedicates neurons to what parts of the body?
Hands , mouth, & face
If there is damage to the primary motor cortex, what occurs?
Upper motor neuron syndrom
* Commonly associated with stroke
What symptoms occur with upper motor neuron syndrome?
Weakness/paralysis
Hyperactive reflexes
Decreased motor control
Abnormal muscle tone
Name the two other motor-related areas of the cortex
Supplementary motor area
Premotor cortex
Locate and name the functions and projections of the supplementary motor area.
Found in the medial frontal lobe and plays a role in planning a response before execution, receives information from the parietal lobe.
Projects to primary motor cortex, reticular formation, and spinal cord
* Best for preparation and agency
Damage to the supplementary motor cortex can cause ______.
Alien hand syndrome
Describe alien hand syndrome.
Typically occurs in one hand or leg & the limb will act independent from the person’s desires
Describe the role of the premotor cortex
It plays a role in somatotopic organization, movement preparation, and orienting the body for movement. It is important for everything before movement initiation
Why is the corticospinal tract important?
For moving face muscles
Relate the corticospinal tract to the primary motor cortex
The activation of the primary motor cortex will send signals down the corticospinal tract
Which hemispheres control which parts of the face?
Upper face is controlled by both hemispheres
Lower face is controlled by contralateral hemispheres
Describe the path a signal takes down the corticospinal tract
The long neurons activate in grey matter
The axons will pass through the internal capsule
The signal will then descend down the brainstem to the pyramidal decussation
What occurs with damage to the pons?
Locked-in syndrome
Describe the path of the lateral corticospinal tract
It begins in the motor cortex, where 85% to 90% will cross at the pyramidal decussation. It will end in the anterior horn of the spinal cord
Describe the path of the anterior corticospinal tract
It descends in the anterior part of the corticospinal tract, where 10% to 15% descend ipsilaterally to the spinal cord.
Why is the corticospinal tract divided?
To offer a level os system redundancy in case of damage. Despite split, both tracts carry the same info
Define the corticonuclear system.
The cortex that communicates with areas of the brainstem & is dedicated to head and contracting muscles
Name the other brainstem tracts
Vestibulospinal tract
Rubrospinal tract
Reticulospinal tract
Describe the importance of the vestibulospinal tract
The vestibular nuclei are important activating extensors & anti-gravity/postural, and orienting the head & body in space
Describe the importance of the rubrospinal tract
The red nuclei helps controls upper extremities & modify motor performance
Describe the reticulospinal tract
The reticular nuclei involved in postures, pain modulation, & visceromotor activity
Define innervation ratio
Number of muscles innervated by given motor neurons
Relate motor units to force output
Larger motor unit, larger force output
How many fibers are associated with small and motor units?
10 to 100 fibers for small motor units
600 to 1000 for large motor units
Why is the organization of the axons to muscle fibers important?
The distributed pattern allows muscles to act uniformly rather than staggered activation
* e.g.
Define Hennemman’s size principle
The size of cell body is proportional to the size of the muscles it innervates & speed of muscle contraction
Name the 2 ways force is increased
Increasing motor unit recruitment & unit firing rate
As necessary force increases, ______ & ______ increases
Size & voltage
* Bigger size, bigger voltage, bigger force
Define twitch
Force in response to one action potentional
Define tetanus & name the two types of tetanus
The contraction of muscle in response to stimulation
* Fused & Unfused tetanus
Define fused tetanus
Firing rate of action potential exceeds a certain amount, so ceilings are reached for the force output
Define unfused tetanus
Easier to decipher because of clear rise and fall
Name the two types of muscle fibers
Slow twitch (type 1)
Fast twitch (type 2)
Name the characteristics of a slow twitch muscle fiber
Low maximal force
Long contraction time
Fatigue resistant
Produces small force for very long time
* Marathon muscles
Name the two types of fast twitch fibers
Fatigue resistant & Fatiguable
Name the characteristics of fast twitch fibers
High peak force
Fast contraction time
Fatiguable & Fatigue-resistant fibers
* Sprint muscles
