Movement ( + Textbook Chapter 7 ) Flashcards
Explain THREE things highlighting the relevance of the muscles in the context of biological psychology.
Muscles allow…
- Movement.
- Behavioural expression.
- Response to stimuli.
Define:
The quantal theory of neurotransmitter release.
Neurotransmitters are released from vesicles typically containing a similar number of molecules in each.
Increased stimulation leads to increased release of fixed ‘packages’ (vesicles).
List:
The THREE types of muscle cells.
- Smooth
- Striated
- Cardiac
Striated muscle cells are also known to be skeletal muscle cells.
What function does smooth muscle tissue serve?
Mobility and motility of internal organs.
What function does striated muscle tissue serve?
Support and movement of the skeletal system.
What function does cardiac muscle tissue serve?
Enabling the pumping action of the organ to power blood circulation.
Cardiac muscle cells are similar to striated, but appear more like a tangled network.
True or False:
One neuron can innervate multiple different skeletal muscle cells.
True
True or False:
Each muscle fibre receives information from only one neuron.
True
Because although each neuron can innervate many different fibres for coordinated stimulation, each fibre should only be receiving input from a single source for specialised activation.
State:
Each structural level of skeletal muscle.
In order from smallest unit to largest unit.
- Myofilaments (actin and myosin).
- Myofibrils (bundles of myofilaments).
- Sarcomeres (segments end to end along myofibrils).
- Muscle fibre (sarcomeres end to end).
- Skeletal muscle (group of muscle fibres).
What is the plasma membrane of a skeletal muscle cell more commonly referred to as?
Sarcolemma.
What is the ER of a skeletal muscle cell more commonly referred to as?
Sarcoplasmic reticulum.
Define:
Neuromuscular junction.
Where a neuron synapses with a muscle fibre.
Which neurotransmitter is the most essential for muscle innervation and contraction?
Acetyl choline.
What kind of receptors does acetyl choline typically bind to during muscle contraction?
Nicotinergic (ionotropic) receptors.
These lead to an influx of Na+ into the cell.
Muscle fibre contraction is similar to action potentials in the sense that it is described as…
…an ‘all or nothing’ response.
The fibre will either contract or it won’t.
What role does the sarcoplasmic reticulum serve during muscle contraction?
It releases stored Ca2+, which activates the sliding action of actin and myosin.
Describe:
The sliding filament theory of muscle contraction.
Contraction of a muscle fibre arises when myosin filaments ‘slide past’ actin filaments and shorten the distance between sarcomeres.
Motor neurons from which part of the spinal cord initiate contraction or movement of skeletal muscles.
(i.e. efferent neurons)
The ventral horn.
“Towards the belly”.
Activation of muscle cells always initiates…
…contraction.
Why is it important for the CNS to receive ‘feedback’ from the muscular system?
So that exact positioning may be known and subsequent appropriate activation.
What are the TWO types of ‘sensory organs’ of the skeletal muscle system?
-
Muscle spindle
& - Golgi tendon organs
Describe the role of muscle spindle.
Sends ‘stretch response’ sensory information to the dorsal root of the spinal cord.
This signal then bypasses the brain to activate a contraction response.
An example is seen in the knee-jerk reflex.
Describe the role of golgi tendon organs.
Provide sensory information for a tension response to help prevent over-contraction.
They synapse with inhibitory interneurons of the spinal cord.
Describe:
The two types of muscle reflexes.
- Voluntary: involves conscious thought.
- Involuntary: does not involve conscious thought despite being driven by the nervous system.
There are few ‘purely’ involuntary movements.
List:
TWO key features of ballistic movements.
- Short and rapid.
- Not subject to correction.
(e.g. saccadic eye movements or throwing a ball etc.)
Such movements are typically performed at maximum velocity and acceleration.
List:
TWO key features of guided movements.
- Usually slower.
- Subject to correction.
Note the corrections may be ‘relatively automatic’.
Define:
Fixed motor programmes.
Sequences of movements that are initiated by the brain but then are highly driven by the spinal cord and essentially ‘run on their own’.
They are a fixed routine from beginning to end, and also tend to have a set length.
(e.g. yawning, smiling, frowning).
True or False:
Many brain regions play a role in muscle movement but none directly innervate muscle cells.
True
Lower motor neurons innervate muscle cells directly.
Which TWO brain regions make up most of the motor cortex and crucial interrelated structures for movement?
Frontal and parietal regions.
The somatosensory cortex is vital for knowing one’s positioning and carrying out corresponding actions during movement.
What is the ‘last stop’ for information in the brain before executing a movement?
The primary motor cortex.
Which brain region receives visual and sensory information during movement processes first?
The primary somatosensory cortex.
What unique feature do the primary motor and somatosensory cortices have in common?
They both have representations for each part of the body.
The representations are not scaled according to size but rather relevance or strength of sensation.
Hence the slightly disturbing ‘homunculus’ figures generated from these mappings.
True or False:
The primary motor cortex controls individual muscles.
False
However, complex movements may arise from its stimulation.
List:
The SIX key brain regions comprising the motor cortex.
- Primary motor cortex.
- Primary somatosensory cortex.
- Prefrontal cortex.
- Premotor cortex.
- Supplementary motor cortex.
- Posterior parietal cortex.
Fill-in-the-Blank:
Movements appear to be ‘____ ____’ .
‘outcome driven’.
Variations are made in order to achieve the ‘final result’.
(e.g. picking up a cup of coffee, and adjusting hand positioning etc.)
What is the role of the posterior parietal cortex in movement?
(Hint: TWO key things).
- Monitors positioning in relation to environment.
- Associated with intentions to move.
Some studies involving stimulation of this brain region have shown to cause people to think they’ve moved when they haven’t.
Describe the role of the supplementary motor cortex in relation to movement.
(Hint: TWO key things).
- Planning or organisation of complex movements.
- Corrections and/or inhibition of movements.
Inhibtion would involve deciding the ‘usefulness’ of a movement before engaging in it.
Which cortex is most active before a movement is made?
The premotor cortex.
Which cortex evaluates the outcomes of actions and how to continue from them?
The prefrontal cortex.
Interestingly, many psychiatric disorders involve reduced activity in this region.
Where are the soma of neurons that activate muscles located?
In the spinal cord.
Describe the TWO nerve tracts within the spinal cord.
Lateral and medial tracts corresponding to the positioning of the body part they innervate relative to the midline.
Define:
The pyramids of medulla.
The point at which pyramidal tracts from the spinal cord
It is at the base of the pyramids whereby the fibres decussate (cross).
This allows for contralateral control of movement (i.e. the left-hand side of the brain controls the right leg).
Define:
Pyramidal tracts
Efferent motor nerve fibres of (mostly) the corticospinal tract.
Which brain region makes up only 10% of the organs total mass, but contains ~80% of the neurons?
The cerebellum.
What is the MAIN function associated with the cerebellum?
Fine motor coordination.
More recent studies attribute broader-spanning roles to this region though, such as those involved in learning and memory (particularly movement-related).
Which set of structures are associated with switching between different motor programmes?
The basal ganglia.
Which brain regions make up the basal ganglia?
(There is dispute on which regions/structures exactly constitute the basal ganglia, so the definition used here coincides with the course textbook by Kalat).
- Putamen
- Caudate nucleus
- Globus pallidus (lateral and medial)
- Subthalamic nucleus
- Substantia nigra
What runs through the gap between the caudate nucleus and putamen in humans?
A pyramidal tract.
Which two disorders involve damage or dysfunction in the basal ganglia?
Parkinson’s and Huntington’s disease.
Parkinson’s isreferred to as cerebral palsy when developed early in life (i.e. childhood).
True or False:
Both Huntington’s and Parkinson’s disease have non-motor symptoms as well.
True
These can include…
Parkinson’s: cognitive changes, fatigue, dizziness, pain, anxiety, insomnia, etc.
Huntington’s: attentional defecits, apathy, dysphagia, memory issues, depression falls, insomnia, urinary control issues, etc.
What is Parkinson’s often misdiagnosed as to begin with?
Depression.
This may be contributed to by a loss of control over facial muscles and thus difficulty physically expressing emotions.
What neurophysiological change is associated with Parkinson’s?
Deterioration of dopaminergic cells in the substantia nigra.
How heritable is Parkinson’s?
Although some genetic predispositions exist, many cases have no hereditary history of the disease.
Which type of dopamine receptors of the caudate putamen are involved in the direct pathway of the basal ganglia?
And are they excitatory or inhibitory?
D1 receptors.
These are excitatory.
Which type of dopamine receptors of the caudate putamen are involved in the indirect pathway of the basal ganglia?
And are they excitatory or inhibitory?
D2 receptors.
These are inhibitory.
What is the importance of D1 and D2 receptors of the caudate putamen?
They are excitatory and inhibitory dopamine receptors of the direct and indirect pathways for movement respectively, and thus play a vital role in initiating and stopping actions.
This is why, in diseases like Parkinson’s, sufferers have difficulty beginning or ending motor movements (e.g. hand tremors, difficulty walking).
What is the role of the direct pathway of the basal ganglia?
It allows the thalamus to stimulate the motor cortex by ultimately inhibiting the inhibitory effect of the globus pallidus (GPi) and substantia nigra reticulata (SNr).
What is the role of the indirect pathway of the basal ganglia?
It prevents the thalamus from stimulating the motor cortex by ultimately stimulating the inhibitory effect of the (internal) globus pallidus (GPi) and substantia nigra reticulata (SNr).
It takes a few ‘extra steps’ compared to the direct pathway, which involve the (external) globus pallidus (GPe) and the subthalamic nucleus (STN).
What does SNc stand for?
Substantia nigra pars compacta
These are nuclei associated with dopamine release, with roles in reinforcement learning, reward, and motor control.
What is L-dopa?
A precursor of dopamine that can pass through the blood-brain barrier and is used as a short-term treatment for Parkinson’s disease.
This is because fully formed dopamine cannot pass the blood-brain barrier.
As more dopaminergic cells deteriorate though, this medication becomes less efficable.
Which alternative treatment for Parkinson’s seems to work well, in particular, for severe tremors?
Deep-brain stimulation.
However, this is a very invasive technique, requiring surgery and so is used only in rare cases.
But this can have long-lasting effects and allow patients to live up to years of relatively normal lives.
Other than deterioration of dopaminergic cells, what is ONE other type of dysfunction associated with Parkinson’s?
Reduction in mitochondrial functioning.
Why are stem cell implants not truly effective in treating disorders like Parkinson’s?
Axon pathfinding is determined by cell-signalling during early development.
Therefore, it is difficult to get these implanted cells to fully develop in an appropriate way for the intended function.
At what age range does Huntington’s typically develop?
20s - 30s
True or False:
Huntington’s is entirely genetically determined.
True
It is caused by a single defective and dominant allele on Chromosome 4 which codes for the Huntingtin protein.
What is the key structural change to a brain region that is associated with Huntington’s?
Degeneration and atrophy of the dorsal striatum.
This particularly affects the indirect pathway and so causes issues with inhibition of movements.
Results in involuntary movement increase.
We’re not entirely sure yet why only these cells seem to experience the main effct despite the gene being expressed everywhere.
What are THREE key motor symptoms associated with Huntington’s?
- Jerky movements.
- Facial twitches.
- Speech difficulties.
Eventually all coordinated motor skills are lost.
