Physiology Flashcards
Areas associated with the production of voluntary motion: (3)
- Primary motor cortex (precentral gyrus)
- Supplementary motor cortex
- Pre-motor cortex
Additionally, parts of the pre-frontal cortex and the parietal cortex contribute to voluntary motion as well.
A dorsal pathway leaving the occipital cortex and going to the parietal/frontal cortex enables us to:
Complete motor acts based on visual input.
This path allows you to play catch with your friends…
The ventral pathway relays info to the inferior temporal cortex and allows us to:
Process the visual image so that we can copy it if needed and name/recognize it.
Similar or related objects are all coded for in localized regions of the temporal lobe. There is a specialized area for recognizing faces.
When reaching for an object, there are 2 pathways:
Pathway 1: Where the object is located in space.
Pathway 2: Mapping the location of your arms in relation to the object.
Pathway 1
- Multiple areas within the parietal cortex receive the input from the occipital cortex: (4)
- End result:
- V6A
- PEc
- MIP (medial intraparietal area)
- VIP (ventral intraparietal area)
End result: The VIP creates a rough map of the space around you.
Pathway 1
- From the VIP (ventral intraparietal area), the info is sent to:
- End result:
F4 within the premotor cortex.
End result: F4 creates a detailed map of the space around you. Neurons here are particularly excited by proximity.
Pathway 2
- Within the parietal cortex, the initial processing is the same regions (V6A, PEc, AIP), but the info is instead sent to:
- End result:
F2 within the premotor cortex.
End result: F2 constructs a map similar to what we saw in F4, but it contains info about where you are in space.
To grasp an object, visual information is relayed to an area of the parietal cortex that is lateral to what was involved in creating the map of space when reaching for an object. This area is called the: (2)
- Anterior intraparietal area (AIP)
- PFG (parts of the inferior parietal cortex)
The AIP and PFG contain 3 sets of neurons:
- Visually dominant neurons fire when you see an object to grasp.
- Motor dominant neurons fire when grasping an object.
- Visuomotor neurons fire during either condition.
Unlike what we saw when reaching, the object has to be within your reach (not just any graspable object).
The AIP and PFG relay their info to:
What do these neurons encode?
F5 (premotor cortex area)
Encodes the GOAL of the action.
Neurons in F5 (premotor cortex) are involved in determining the ______ of the motor act
Intent
ANY motor action with the same intent activates the F5 neurons REGARDLESS of the physical specifics of the act (grasping top edge of cup vs. handle).
Premotor Cortex
Role of the ventral (lateral) regions (F4 and F5):
Integrate the sensory information required to complete the motion
Premotor Cortex
Role of the dorsal (medial) regions: (3)
- Determine whether it is appropriate to move.
- Identifies the intent of the motion.
- Determines what motion to produce.
2 divisions of the Supplementary motor cortex:
What is the role of each?
- Supplementary Motor Area (SMA) - postural control, multi-joint movements
- Pre-supplementary Motor Area (Pre-SMA) - plans complex motor actions.. active with the thought of motion, NOT with the actual motion
The Supplementary Motor Cortex has 3 main roles:
- Organize motor sequences
- Acquire motor skills
- Executive control (particularly the decision to switch actions/strategies)
Location of the primary motor cortex:
Precentral gyrus
T/F: Regions which do things requiring fine control have the most representation within each of these areas of the primary motor cortex (e.g., fingers, tongue).
TRUE
Cells in the primary motor cortex (precentral gyrus) are arranged in _______, and stimulation produces a ________ ________.
- column
- specific movement
T/F: If we’re in an area that controls a more general motion, stimulation may produce contraction of a GROUP of muscles (e.g., in your back).
TRUE
Only output is via _________ cells - located in one layer of the column (where the pyramidal tract gets its name).
-pyramidal
Layer _ receives sensory (afferent) input (muscle and joint proprioceptors, etc).
Layer 4
Layer _ becomes the output for the corticospinal (pyramidal) tract via pyramidal cells.
Layer 5
T/F: Compared to the sensory cortex, motor cortex has expanded layer 5 and compressed layers 2, 3, and 4.
TRUE
There appears to be 2 sets of neurons in each column:
- One set STARTS the movement
- The other set MAINTAINS the movement
There are also 2 types of columns:
- One supports the onset and offset of motion in the agonist muscle
- The other set supports the onset and offset of motion in the antagonist muscle
T/F: Neighboring columns control related motions, NOT neighboring muscles.
TRUE
Roles of the cerebellum: (4)
- Sequence complex actions
- Correct force/direction
- Balance and eye movements
- Learning of complex actions
Functional divisions of the cerebellum: (3)
- Spinocerebellum
- Cerebrocerebellum
- Vestibulocerebellum
2 regions of the spinocerebellum and their roles:
- Central - postural control
- Either side of the vermis - force and direction
Roles of the cerebrocerebellum (lateral regions of cerebellum): (2)
- Plan complex motions
- Sequence motions
Roles of vestibulocerebellum: (2)
- Balance and eye movements
- Being planned in the future, not necessarily what’s happening at that moment
Outputs from cerebellum are via the ____ __________ ______.
-deep cerebellar nuclei
Deep cerebellar nuclei: (4)
- Dentate nucleus
- Fastigial nucleus
- Globose
- Emboliformis
Note: The globose and emboliformis nuclei are sometimes lumped together as the ____________ nucleus.
-interpositus
Job of Vermis (spinocerebellum):
Control of axial musculature and posture
Inputs to Vermis (spinocerebellum): (3)
- Vestibular
- Visual and auditory
- Efferent copy (what the motor neurons are telling the muscle to do)
Outputs from Vermis (spinocerebellum): (3)
- Interpositus
- Fastigial nucleus
- To Rubrospinal tract via red nucleus
Functions of spinocerebellum (region lateral to the vermis): (2)
- Control of the force and direction of motion… if damaged, intention tremor will result
- Controlling ballistic movements
Inputs to spinocerebellum: (2)
- Efferent copy (what brain thinks is happening) via the ventral spinocerebellar tract
- Muscle afferents* (muscle spindle, Golgi tendon, etc…) via the dorsal spinocerebellar tract
Outputs from spinocerebellum: (3)
- Interpositus (Globose and Emboliformis)
- To rubrospinal tract
Functions of the cerebrocerebellum: (2)
Sequencing - especially of rapid learned movements (playing the piano)
- Planning the sequence
- The timing of the movements within the sequence
T/F: The neurons of the cerebrocerebellum are concerned with what WILL be happening, NOT what IS happening.
TRUE
Inputs to cerebrocerebellum: (1+)
Cerebral cortex (all)
- Primary motor area
- Premotor area
- Supplementary motor cortex
- Somatosensory
Outputs from cerebrocerebellum: (2)
- Dentate
- back to cortex through the ventral lateral nucleus of the thalamus
Function of vestibulocerebellum (flocculonodular region):
-Controls eye movement and balance, particularly in future*
Effect of lesions on vestibulocerebellum…
At rest:
In motion:
At rest: balance well
In motion: have trouble maintaining balance
Input to vestibulocerebellum:
Vestibular apparatus (direct or indirect) CN VIII (vestibulocochlear N.)
Output from vestibulocerebellum:
Fastigial nucleus to Vestibular nuclei to either ascending or descending tracts
Together, the putamen and the caudate nucleus are called the ________.
striatum (also includes the accumbens, but it’s not involved in motor control)
The ________ receives the inputs to the basal ganglia.
striatum
The nucleus within the striatum that is most heavily involved in motor control:
Putamen
Nigrostriatal dopaminergic system
From:
To:
Effects:
From: substantia nigra pars compacta (SNPC)
To: striatum
Effects: D1 (+), D2 (–)
Intrastriatal cholinergic system Location: From: To: Effect:
Location: between nuclei of the striatum
From: neurons of striatum
To: synapse on other neurons of striatum
Effect: excitatory
Striatonigral GABA-ergic pathway "The Direct Pathway" From: To: (2) Effect: Leads to:
From: striatum (putamen + caudate nucleus)
To: substantia nigra pars reticularis (SNPR) and internal segment of globus pallidus (GPi)
Effect: inhibitory
Leads to: initiation of movement
Information leaves the basal ganglia via the ____ and ___.
- SNPR
- GPi
The SNPR and GPi axons project to the ________ and release ____.
- thalamus
- GABA
Nuclei of basal ganglia: (4)
- Substantia nigra (pars compacta & pars reticulata)
- Striatum (caudate and putamen)
- Globus pallidus (internal/external segments)
- Subthalamic nucleus
Neurotransmitter systems of the basal ganglia: (3)
- Dopamine
- Cholinergic
- GABA-ergic
Inputs into basal ganglia received by: (1)
Outputs sent to: (2)
Inputs: substantia nigra pars compacta relays to striatum
Outputs: globus pallidus (internal segment) and substantia nigra pars reticulata send axons to thalamus
-When activated, release GABA at synapses in thalamus… inhibition of thalamus
Basal ganglia
What they do:
How:
What they do: control beginning and the end of the movement
How: inhibition and disinhibition (withdrawal of that inhibition)
-Major dz’s of basal ganglia cause their symptoms by either removing this inhibition (Huntington’s Chorea) or by removing the brakes on the inhibition (Parkinson dz)
The inputs into the striatum include: (6)
- Cortex (all) - via corticostriate track by using EAA
- Centromedian nucleus of thalamus - EAA
- Pars compacta of substantia nigra (SNPC) - dopaminergic input, tonically active**, provides background excitation to striatum
- Within caudate and putamen- two diff sets of neurons
- The Direct Path: direct connection to output nuclei of basal ganglia, D1 receptors, input from SNPC is excitatory
- The Indirect Path: connect indirectly to output nuclei of basal ganglia, D2 receptors, input from SNPC is inhibitory*
“The Direct Pathway”
- To activate, ____ sends dopamine to striatum.
- Dopamine binds (D1/D2) receptors.
- Axons release ____ in GPi and SNPR.
- By inhibiting the SNPR and GPi, (more/less) GABA is released in the thalamus. The thalamus is then free to excite the cortex, allowing the initiation of movement.
- SNPC
- D1 receptors
- GABA
- LESS GABA in thalamus… allows movement
“The Indirect Pathway”
Input from the SNPC is (excitatory/inhibitory) to the striatal neurons that are part of the indirect pathway due to the (D1/D2) receptors
- inhibitory
- D2
T/F: To ACTIVATE the indirect pathway, we must use input from the cortex and the intrastriatal pathway.
TRUE
“The Indirect Pathway”
The striatal neurons synapse on the ___ (GABA) - by activating the striatal neurons, we release (more/less) GABA. Activity in the GPe is (increased/decreased)
- GPe
- MORE
- decreased
“The Indirect Pathway”
The neurons of the GPe synapse in the ___________ _______. Since GPe neurons are less active, there is (more/less) inhibition of the subthalamic nucleus.
- subthalamic nucleus
- LESS inhibition (disinhibition)
“The Indirect Pathway”
Neurons from the subthalamic nucleus synapse in the ____. Since they’re active (less inhibited), (more/less) EAA are released in the SNPR.
- SNPR
- MORE EAA released
The effect of the direct pathway is to:
INHIBIT the neurons in the GPi and SNPR
The effect of the indirect pathway is to:
EXCITE the neurons of the GPi and SNPR
The limbic system is now recognized to control: (2)
- Emotional behavior
- Motivational drives