Lecture 29 Flashcards
What types of movements are available with somatic control? What links all of these processes?
Reflex movements: A predictable, reproducable automatic response to a particular sensory stimulus.
Voluntary movements: those we choose to do consciously
Automatic movements: Those which occur without major thought e.g chewing, walking, or smiling.
These are all linked by the final common pathway of motor units.
What does a typical reflex arc look like?
has a stimulus and a receptor, the afferent neuron sends the signal from the receptor to an interneuron in the CNS (but not the brain, usually just the spinal cord) and this interneuron synapses with an efferent neuron which sends the signal to perform an action to the effector.
What is the stretch reflex and a common example?
The stretch reflex is a reflex which occurs which muscles, muscle spindles detect an increase in length and cause a reflex arc which triggers the muscle to contract in order to return to its original length. A common example of this is the patella stretch reflex.
What is a monosynaptic reflex?
A reflex arc which involves only a single chemical synapse.
Whats a common effect which occurs in the other limb when a withdrawal reflex occurs?
As one side withdraws the other side stabilises, this typically occurs by the opposite effect in the opposite limb e.g if the left leg withdraws through the contraction of the quadriceps femoris then the right leg will contract the hamstrings.
What are the names for the withdrawing and stabilizing sides of the body in a withdrawal arc?
ipsilateral is the withdrawing side, contralateral is the stabilizing side.
How does the pain which typically occurs with a withdrawal arc reach the brain? Why does this reach us after we have already withdrawn?
interneuron sends an afferent signal to the brain as well as an efferent signal to the effector, the effector signal reaches first. Hence we have moved the effector before the pain reaches us.
What are the two main parts of the motor cortex? What other part of our brain is typically involved in voluntary movement and why?
The primary motor cortex (activates the specific motor units) and the pre motor cortex (plans the movement). The other part which is involved is the prefrontal cortex as it is where we process our goals and hence lets us decide we need to do a movement to achieve our goal.
What is the corticospinal pathway arrangement?
two neurons, a lower and upper motor neuron. The signal starts in the primary motor cortex in the upper moror neuron, this crosses sides of the body at the medulla and then travels down the corticospinal tract in the spinal cord, then is will have an excitatory synapse with the lower motor neuron
(occasionally an interneuron may be involved). The lower motor neuron then activates whatever muscle fibers it synapses with.
What are the two main examples of non corticospinal pathways? What functions do they tend to have?
Reticulospinal tract: excites lower motor neurons to extensors and inhibits flexors.
Rubrospinal tract: Excites the flexors and inhibits extensors.
Both are exclusively involved with automatic movements.
What part does the basal ganglia play in integrating motor and sensory systems?
Continually modifys our movement via a loop system found within the cortex. Helps to select the correct movement for any given situation.
What is the role of the cerebellum in regards to movement?
It compares what movement has occured with what movement is wanted, this is done by checking sensory feedback, also helps maintain posture.
What does procedural memory lead to?
automatic movements and motor programmes (muscle memory.
Which three nuclei does the basal ganglia comprise?
The lentiform, Caudate and amygdaloid nuclei.
What is it that occurs in the basal ganglia which allows us to move?
Inhibition to the basal ganglia causes it to no longer inhibit our motor cortex, hence movement occurs.
