Lecture 1: Movement & Reflexes Flashcards
Do afferent divisions enter or exit the brain?
Enter
Do efferent divisions enter or exit the brain?
Exit
General brain pathway
- Sensory or visceral stimuli received by afferent division
- Afferent division inputs information to brain
- Processing in brain
- Response through efferent divisions (different types)
Types of efferent divisions
- Somatic nervous system
- acts on motor neurons to move skeletal muscles - Autonomic nervous system
a) sympathetic nervous system
b) parasympathetic nervous system
- both act on smooth & cardiac muscle, exocrine glands and some endocrine glands
c) enteric nervous system
- controls digestive organs
What is rostral to the central gyrus?
Premotor & primary motor cortex
What is caudal to the central gyrus?
Somatosensory cortex & primary parietal cortex
Premotor cortex function
Coordination or complex movement
Primary motor cortex function
Voluntary movement
Somatosensory cortex function
somaesthetic sensation and proprioception
Posterior parietal cortex function
Integration of somatosensory and visual input; important for complex movements
T/F: motor cortex on each side of the brain primarily controls the contralateral muscles
TRUE
Where is the site for initial processing?
Primary somatosensory cortex
Basal ganglia function
- Inhibiting muscle tone throughout the body by initiating inhibitory modulation of moto pathways through the thalamus
- Selecting and maintaining purposeful motor activity
- Suppressing unwanted movement
- Coordination of slow and sustained contractions
What part of the basal ganglia is involved in PD?
Substantia nigra
What part of the basal ganglia is involved in HD?
Caudate and putamen
Basal ganglia includes:
caudate nucleus, globus pallidus, putamen & substantia nigra
Thalamus function
- Reinforces voluntary movement
- Serves as a ‘relay station’ for sensory input
Thalamus in basic sensory interpretation
Capable of crude awareness of sensations but cannot distinguish their location
Cerebellum function
- Learns and executes instructions for movement
- Motor skills through repetitive training
If there is a lesion in or near the midline of the cerebellum, what disorder will result?
Posture disorders
Vestibulocerebellum function
Maintaining balance
Spinocerebellum function
Coordination
Cerebrocerebellum function
Planning & initiation of voluntary behaviour
What does the brain stem consist of?
Mindbrain, pons & medulla
Brainstem function
- Control of CV, respiratory & digestive function
- Regulates postural muscles
- Controls overall cortical alertness
Where do sensory afferents enter the spinal cord?
Through dorsal root (DRG)
Where do motor efferents exit the spinal cord?
Through ventral roots
T/F: afferent & efferent fibres are enclosed together within a spinal nerve
TRUE
Spinal cord functions
- Link between brain and peripheral NS
2. Integration of spinal reflexes
What do Vestibulocerebellum, Spinocerebellum & Cerebrocerebellum work together to do?
Serve functions & instructions for movement & coordination
Lesions in cerebellum cause what kind of injury?
Ipsilateral
Golgi tendon is for
Tension (measures tension)
What do muscle spindles do?
Measure changes in length
Do all intrafusal fibres contract?
NO: they have contractile and non-contractile portions
Do all extrafusal fibres contract?
YES
What motor neurons supply intrafusal & extrafusal spindles?
Efferent motor neurons
What do afferent endings do?
Report how effective contraction was
Where are the primary (annulospiral) endings and what do they do?
Wrapped around central (non-contractile) portion of intrafusal fibres
- Detect changes in muscle length and speed of muscle stretch
Where are the secondary (flower spray) endings and what do they do?
Clustered at end-segments of intrafusal fibres (contractile portions)
- Detect changes in muscle length ONLY
Activity at spinal cord
Afferent info brought in -> may or may not have synaptic activity (at interneuron) -> if IN is stimulated enough (EPSP), causes activation of an effector response
What are simple or basic reflexes?
- Built in and unlearned responses (e.g. knee jerk)
What are acquired or conditioned reflexes?
- Result of practice and learning (e.g. catching a ball)
What are the 2 types of spinal reflexes?
- Monosynaptic
2. Polysynaptic
What are monosynaptic reflexes?
- Stretch reflex; only one synapse in the reflex arc between afferent and efferent neurons
What are polysynaptic reflexes?
- Withdrawal reflex and cross extensor reflex
What are the 5 key components of a reflex arc?
- Receptor
- Afferent pathway
- Integration centre (CNS)
- Efferent pathway
- Effector
How does a reflex arc work?
- Some kind of sensory receptor activated -> significant enough to cause AP along afferent neuron to CNS -> synapses on I-N -> may or may not have stimulation of efferent pathway -> consequence
How does the knee tap reflex work?
Patella tendon stretches -> detected by stretch detectors (muscle spindles) found in quads -> muscle spindles stimulate sensory neuron that travels to spinal cord -> synapses with motor neurons that control contraction of quads -> motor neurons cause immediate contraction of quads to produce leg movement
How does the withdrawal reflex work?
Thermal pain receptor stimulated -> goes through afferent pathway into spinal cord -> nerve fibres that cause contraction of bicep activated + nerve fibres that cause contraction of tricep inhibited -> ascending pathway to brain cause hand to move
How does the cross-extensor reflex work?
- We need to have ipsilateral F away from bottle + contralateral E on the other leg to stop the person from falling over
- Receptor picks up harmful stimulus -> sensory neuron transports electrical stimulus to CNS -> integration centre (we have 2: 1. IN processing info on same side; 2. IN processing info on opposite side) -> motor neuron (we have 2: 1. same side; 2. opposite side -> effector: skeletal muscles on same (hamstrings contract to move foot away) & opposite (quads contract to hold leg down) sides
What parts of the CNS are involved in movement?
Cerebral cortex, basal nuclei, cerebellum, brainstem, spinal cord pathways
What contributes outside the CNS for balance and movement?
Reflexes, spindles, golgi tendons
Repetitive training of motor actions heavily involves the…?
Cerebellum
What is the simplest reflex?
Knee jerk
What is the difference between the withdrawal reflex & crossed-extensor reflex?
Withdrawal: all happens ipsilaterally
CER: has ipsilateral and contralateral components
Both: control 2 lots of muscles (one is just on the same side, other is on both sides)
