Chapter 17: Pathways and Integrative Functions Flashcards
Define ganglion.
Cluster of neuron cell bodies within the PNS
Define center.
Groups of CNS neuron cell bodies with a common function
Define nucleus.
Center that displays discrete anatomic boundaries
Define nerve.
Axon bundle extending through the PNS
Define nerve plexus.
Network of nerves
Define tracts.
CNS axon bundle in which the axons have a similar function and share a common origin and destination
Define funiculus.
Group of tracts in a specific area of the spinal cord
Define pathway.
Centers and tracts that connect the CNS with the body organs and systems
Define decussation.
Cross over from one side of the body to the other so the left side of the brain is processing info from the right side of the body and vise versa
List the components of a typical nerve pathway.
- Pathways conduct either sensory or motor info
- Processing and integration occur continuously along the pathway
- Travel though white matter of brainstem and spinal cord and connect CNS regions with cranial and spinal nerves
- Consist of a nucleus and a tract
- All pathways are composed of paired tracts
- Ascending (afferent) and descending (efferent) pathways
- Some decussate
- Most exhibit a precise correspondence between a specific area of the body and a specific area of the CNS
List the primary sensory pathways. Describe their general function, general structure, and location.
Sensory pathways conduct info about limb position and sensations of touch, temp, pressure, and pain.
2 Types
- Somatosensory Pathways (stimuli from skin, muscles, joints))
- Viscerosensory Pathways (stimuli from viscera)
Receptors detect stimuli and conduct impulse to CNS where the sensory pathway centers within the spinal cord or brainstem process and filter the incoming info to determine if it should be transmitted to the cerebrum or terminated (more than 99% do not reach the cerebral cortex and conscious awareness)
Sensory pathways use 2 or 3 neurons to transmit info from body periphery to brain.
- Primary Neuron (1st order)
- Dendrites are part of receptor that detects stimulus
- Cell bodies in posterior root ganglion (spinal nerves) or sensory glial (cranial nerves) - Secondary Neuron (2nd order)
- Interneuron
- Cell body in posterior horn of spinal cord or brainstem nucleus
- Axon goes to the thalamus and synapses with tertiary neuron - Tertiary Neuron (3rd order)
- Interneuron also
- Cell body in thalamus
List the 3 types of somatosensory pathways and what makes them unique.
- Posterior funiculus-medial lemniscal pathway
- Sensory info: proprioception, discriminative touch, pressure, and vibration - Anterolateral pathway
- Decussation in anterior white commissure
- Conduct stimuli related to crude touch and pressure, pain and temp - Spinocerebellar pathway
- *No tertiary neuron and does NOT go to thalamus
- Proprioceptive info to cerebellum for processing tp coordinate body movement
List the primary motor pathways. Describe their general function, general structure, and location.
- Descending pathways in brain and spinal cord control and regulate skeletal muscles
- Formed from cerebral nuclei, cerebrum, descending tracts, and motor neurons
2 motor neurons in somatic motor pathway:
- Upper Motor Neuron (CNS)
- Lower Motor Neuron (PNS)
Discuss differences between upper and lower motor neurons (location and function).
Upper Motor Neurons (CNS)
- Cell body within cerebral cortex or brainstem
- Excites or inhibits activity of lower motor neuron
Lower Motor Neurons (PNS)
- Cell body within anterior horn or spinal cord or brainstem cranial nerve nucleus
- Always excitatory b/c axons connect directly to skeletal muscles
List and briefly describe the 2 types of motor pathways.
Direct Tracts
- Provide conscious control of skeletal muscle activity
- Originate in the primary motor cortex (3)
1. Corticobullbar (Cranial Muscles: eye movement, tongue, face, neck muscles) originates from facial region of motor homunculus
2. Lateral Corticospinal (Limb Muscles)
3. Anterior Corticospinal (Axial Muscles)
Indirect Tracts
- Provide unconscious control of skeletal muscle activity
- Multisynaptic; high degree of complexity
- Originate in brainstem (4)
1. Rubrospinal (Flexor muscle tone)
2. Reticulospinal (Unskilled posture/balance)
3. Tectospinal (Positional change in response to visual and auditory stimuli)
4. Vestibulospinal (Balance during activity)