Topic 4 - Anatomy of the Nervous System Flashcards
Motor Unit
- Muscle fibre
- Motor end plate
- Efferent neuron
4 Types of Somatosensory Receptors
Movement Related:
- Muscle Spindles (muscle)
- GTO (tendons)
- Cutaneous receptors (skin)
Nocireceptors:
- heat, chemicals, touch -> pain
Fxn of MUSCLE SPINDLES and neurons associated
Tell us about muscle length
Ia and II afferent neurons
Fxn of GTOs and neurons associated
Tell us about muscle FORCE / rate of change in length
Ib afferent neurons
Fxn of cutaneous receptors
Tell us about skin deformation / stretch
Fxn of NOCIREDEPTORS
Tell us about pain
2 Types of Efferent Neurons
- Alpha MNs
2. Gamma MNs
Alpha MNs
Innervate extrafusual muscle fibres
Main contributer to movement
Gamma MNs
Innervate intrafusal muscle fibres
Tune somatosensory information from muscle spindles (Ia afferent)
Even though they’re efferent, large role in sensory info
Grey Matter
Cell bodies & unmyelinated axons
Communication & synapses
White Matter
Myelinated axons
Neural tracts & pathways (where info ascends & descends)
3 Components of Brain Stem
- Midbrain
- Pons
- Medulla
Corpus Callosum
Interhemispheric communication
Lots of myelinated axons (tracts) -> white matter
Layers of the Cerebral Cortex
- Molecular
- External Granular
- External Pyramidal
- Internal Granular
- Internal Pyramidal
- Multiform
Molecular Layer
Local communication
Lots of basket cells (multipolar neurons w/ lots of axonal & dendritic trees)
External Granular Layer
INPUT from other cortical areas
Ex. Somatosensorty cortex to motor cortex
Other hemispheres or the same one
External Pyramidal Layer
OUTPUT to cortical areas (layer 2) and layers 4&5
Internal Granular Layer
Input from thalamus (especially sensory)
Internal Pyramidal Layer
Output to SC, BG and brain stem (leaves cortex)
Descending pyramidal neurons
Mulitform Layer
Output to thalamus
Monosynaptic Relay
One synapse
Ex. Tendon tap reflex
Direct activation of alpha motor neuron
Oligosynaptic Relay
2-3 synapses
Slight longer latency that monosynaptic
Polysynaptic Relay
4+ synapses
Voluntary movements are always polysynaptic
Where do synapses occur? Whitenor grey matter?
Grey
What kind of cells are in the dorsal root ganglion
Cell bodies of pseudo-unipolar cells
Cerebellum
Receives sensory input from SC and motor information from cerebrum
Planning, timing, and adaptation/learning of movement
Role in posture and coordination of eye and hand movements
Midbrain
Smaller role in limb movements
Larger role in eye movements via superior colliculus
Pons
Involved in relay between cerebrum and cerebellum
Role in movement, especially posture
Medulla
Influenses postural responses and reflexes
Potential role in startile-elicited responses
- ex. Pre-programmed responses (not entirely voluntary or involuntary)
Somatotopic Organization of SC from lat to med
Cervical (neck and arms) Thoracic (trunk and arms) Lumbar (hips and legs) Sacral (legs and genitals) Cauda equina (horse tail)
2 parts of Dorsal Column
- Gracile Fasciculus (medial)
- lower body somatosensory - Cuneate Fasciculus
- upper body somatosensory