Sensorimotor Nervous System Flashcards
What do sensory pathways do?
Conduct information about limb position and the sensations such as touch, temperature, pressure and pain
Somatosensory pathways process stimuli received from receptors within the skin, muscle and joints
Viscerosensory pathways process stimuli received from the viscera
What do motor pathways do?
Output from the spinal cord to the muscles, supervised by the descending brain pathways, influenced by the sensory inputs
Describe the structure of a nerve
A nerve is made up from a variety of fascicles, each encased by perineurium
Inside the fascicle are a group of axons bathed in endoneurial fluid
Each axon has a insulating layer of myelin
The nerve is then wrapped in the main epineurium
What are the receptors found within the sensory system?
Sensory receptors may be nerve endings, or specialised cells closely associated with nerve fibres
Includes: mechanoreceptors, chemoreceptors, photoreceptors and thermoreceptors
What is the function of a sensory receptor?
To trigger a neuronal response
Environmental changes cause a change in membrane potential
If this reaches threshold it will trigger an action potential- sensory transduction
This information then goes to the brain via ascending fibres, primary then secondary afferent nerve fibres
What is a dermatome?
Spinal nerves have a distinct arrangement
Each pair of nerves receives sensory information from a dermatome- n area of the body surface
The receptive fields of each dermatome overlap
How does the brain control voluntary movement?
The primary motor cortex is located in the precentral gyrus located in the frontal lobe
The somatosensory cortex is located in the post-central gyrus
Axons connect to the brainstem and spinal cord which generate activity patterns to control the muscles
Hoe do somatosensory pathways take the message to the spinal cord and brain?
There are two afferent pathways to the brain- dorsal column for fine touch, vibration and position; spinothalamic for crude touch, temperature and pain
Three neurons synapse in the spinal cord and in the thalamus, cross the midline in the spinal cord and terminate in the somatosensory cortex
How do motor pathways take the message to the spinal cord and muscles?
There are two efferent pathways to the muscles- dorsolateral corticospinal tract goes to periphery; ventromedial corticospinal tract goes to shoulders, neck and trunk
Two neurons synapse in the spinal cord, cross the midline in the spinal cord and terminate at the neuromuscular junction with skeletal muscle
What other areas of the brain act with the motor cortex?
The motor cortex can direct contraction of specific muscles and direct a combination of contractions to produce a specified outcome
Other areas contribute to motor function by allowing the integration of other sensory information:
Posterior parietal cortex- visual information
Sensory motor cortex
What does the prefrontal cortex do?
Response to light, noises and other sensory signals
Calculates predictable outcomes of actions and plans movement accordingly
What does the premotor cortex do?
Active during preparation for movement and receives information about a target in space
Integrates information and position and posture of the body and organizes the direction of the movement in space
What does the supplementary motor cortex do?
Important for organizing a rapid sequence of movements
What does the cerebellum do?
Often associated with balance and coordination
Damage to the cerebellum causes trouble with rapid movement requiring aiming and timing
What does the cerebellar cortex do?
The cerebellum receive input from the spinal cord, from each of the sensory systems, and from the cerebral cortex and sends it to the cerebellar cortex
