Motor Control & Somatic Sensation Flashcards
What is the first step of a spinal reflex?
Stimulation of a receptor
What happens after a receptor is stimulated?
Activation of a sensory neuron
What happens after a sensory neuron is activated?
Information processing in the CNS
What happens after information processing in the CNS?
Activation of a motor neuron
What happens after activation of a motor neuron?
Response of a peripheral effector
How are spinal reflexes described?
Organised neural circuit which is contained within the spinal cord and is. reproducible, automatic response to a particular stimulus
What are the two types of reflex?
Stretch and withdrawal
What is the first step of a stretch reflex?
Stimulation of a receptor causes a stretch (receptor= muscle spindle)
What happens after stimulation of a receptor causes a stretch?
A sensory neuron is activated where the stretch occurred
What happens after a sensory neuron is activated where the stretch occurred?
Information processing in the CNS (spinal cord)
What happens after information processing in the CNS (spinal cord)
Activation of a motor neuron attached to muscle spindle
What happens after activation of a motor neuron attached to muscle spindle?
Response of a peripheral effector (contraction)
What is the muscle spindle involved in?
Stretch reflex (shortening of muscle) and posture
What is included in the muscle spindle?
Motor neurons from the CNS which innervate each muscle spindle
What is the first step of the withdrawal reflex?
Painful stimulus
What happens after the painful stimulus in the withdrawal reflex?
To the posterior root ganglion
What happens after the posterior root ganglion in the withdrawal reflex?
Distribution within grey horns to other segments of the spinal cord and to the brain (more than one synapse)
What happens after the distribution within the grey horns to other segments of the spinal cord and to the brain in the withdrawal reflex?
Excitatory effect is relayed to flexors and relax effect is relayed to extensors to cause reciprocal inhibition
What happens in the brain during the withdrawal reflex?
Messages received in the spinal cord may be overridden by what is happening in the brain if there is other consequences of the movement
What is the function of the cerebellum in preparing for and performing movement?
Coordinates muscles guided by sensory feedback, compares intended movement with the actual result, helps maintain posture and gaze and helps learn and automate movements
What happens when preparing form movement in the brain?
The decision made in the frontal lobe is transferred to the premotor cortex and then to the cerebellum
What does the cerebellum do when performing voluntary movement?
Compares sensory feedback about the actual movement to the intended movement and signals adjustments to the primary motor cortex
What happens after adjustments have been signalled to the primary motor cortex?
Messages are conducted down the corticospinal pathway to the lower motor neurons so that motor units can be activated to cause muscle contraction
What can cerebellar deficits cause?
Ataxia characteristic ‘drunken gait’
What are the two types of sensory inputs into the brain?
Special senses and somatic & visceral sensations
What are some special senses?
Vision, hearing, taste, smell (& pheromones) and vestibular (balance)
What are some somatic & visceral sensations?
Touch, pain, warm & cold and body position
What is an example of direct inputs?
Hypothalamic temperature sensing
What is an example of endocrine inputs?
Food intake regulation
What type of neurons are sensory neurons?
pseudounipolar
What is the receipt for somatic & visceral sensation?
The ending of an afferent (somatosensory) neuron
What is the receptor for special senses?
A specialised receptor cell
What is inside the receptor cell?
Vesicles containing a chemical messenger
What is sensory receptors highly sensitive to?
A particular stimulus (modality)
What are the four types of information to describe a sensory stimulus?
MModality, intensity, duration and location
What is meant bu modality?
The type of sensory receptor activated
What is meant by intensity?
The frequency of action potential firing in afferent neuron
What is meant by duration?
Duration of action potential firing in the afferent neuron
What is meant by location?
Location of sensory receptors activated ‘mapped’ in the brain
What controls proprioreception?
Muscle spindle controls muscle length, body position, movement and posture
What are the sensory receptors of the muscle spindle?
The endings of the axon wound around the muscle fibres
What do touch receptors have?
A variety of different forms and special functions
What are some touch receptors associated with?
A single hair, the free nerve endings of pain receptors spread more widely in the skin and can respond to stimulation over a wider area (have a larger receptive field)
What happens when the stimulus is below threshold?
There is no response in the afferent neuron
What happens when there is an increasing stimulus?
Increases the action potential frequency and it is conducted down the axon.
What can stronger stimuli also do?
Activate more receptors sn action potentials in more sensory neurons
What are sensory receptors most sensitive to?
Change
What do sensory receptors often show?
Adaptation
What is adaptation?
Decreased output over time in response to continuous stimulation
What is an example of adaptation?
Thermoreceptors are most sensitive to changes in temperature, some touch receptors are most sensitive to vibration
What are the two types of receptors?
Tonic and phasic
What do tonic receptors do?
Are active all the time and the frequency of action potential increases when the stimulus increases
What is an example of a tonic receptor?
Muscle spindles that monitor and detect muscle length
What do phasic receptors do?
Occur in patches when on or off
What is an example of phasic receptors?
Touch receptors activated by vibration
What is the receptive field?
The region of space in which a stimulus can lead to activity in a particular afferent neuron
What does small fields and dense innervation do?
Gives good discrimination (detailed and accurate information)
Fields can…
Overlap, a strong stimuli may activation more than one
What is modality coded as?
A labeled line
What does a labeled line do?
Say what type the information is and where it has come from
What is in integration?
Cerebral cortex, couscous sensation and perception
What is in afferent neurons?
Peripheral nerve and tract or pathway
What is the sensory receptor?
Sensory stimulus converted into action potentials, TRANSDUCTION
What is the post central gyrus?
The primary somatosensory cortex
What is the parietal lobe?
Somatic sensory association cortex
What is sensation and where does it occur?
Conscious identification of ‘what and where’ occurs in the primary region of the cortex (post central gyrus)
What is perception and where does it occur?
Meaningful interpretation occurs in the association (secondary) region of the cortex- parietal lobe
What do areas of the somatosensory cortex correspond to?
Areas of the body
What occupies large regions of the somatosensory cortex?
Densely innervated areas of the body with small receptive fields
What does the left cortex represent?
The right side of the body and vice versa
