PhySci 107 Lecture 5

What does the cerebellum originate from?

metencephalon

What are the general functions of the brainstem?

1. Connects diencephalon to spinal cord 2. Contains neuronal centers critical for survival, e.g. respiratory center 3. Contains 10 out of 12 cranial nerves

Detail the path of the spinothalamic tract

1. Dorsal root ganglion neurons relay pain and temperature from peripheral receptors and synapse on neurons in dorsal horn of the spinal cord 2. Axons of dorsal horn cells cross to the opposite side of the ventral spinal cord through the ventral commissure, ascend in the lateral funiculus and synapse in the ventral posterior nucleus of the thalamus 3. Axons of thalamic neurons project to the appropriate part of the somatotopically organized somatosensory cortex

Detail the path of the dorsal column pathway

1. Dorsal root ganglion neurons relay touch, pressure, and proprioception from the periphery into the dorsal horn where axons branch; one branch enters the dorsal columns ascends on the same side and synapses in Nucleus Gracilis (hindlimb) or Nucleus Cuneatus (forelimb) in medulla. 2. Axons of neurons in Nucleus Gracilis or Nucleus Cuneatus cross the midline and ascend to the VPL thalamus where they synapse. 3. Axons of thalamic neurons project to the appropriate part of the somatosensory cortex

Detail the path of the spinocerebellar tract

1. Dorsal root ganglion relay muscle position information from proprioceptors that synapse in dorsal horn of the spinal cord 2. Axons of spinocerebellar neurons ascend in the lateral funiculus to the cerebellar cortex and synapse on granule cells

What are the three layers of the cerebellum?

1. Molecular layer 2. Purkinje layer 3. Granular layer

What are the general functions of the spinal cord?

1. Receives somatosensory information (sensory afferents) and provides motor output (motor efferents) to muscles for the entire body, but NOT the head and neck 2. provides a two-way conduction pathway between the body and the brain by way of ascending and descending axon pathways 3. major reflex center

What are the three ascending pathways of neural processing?

1. Spinothalamic tract 2. Dorsal Column Pathway 3. Spinocerebellar tract

Where do efferent projections from the deep cerebellar nuclei project to?

1. Thalamus 2. Reticular foramen 3. vestibular nuclei

What are the functions of the cerebellum?

1. To coordinate smooth body movements 2. Participates in learning skilled voluntary movements 3. Assists with postural control 4. Assists with equilibrium eye movements

What do mossy fibers originate from?

1. vestibular nuclei 2. Receptors in muscles, joints, and tendons 3. pyramidal neurons in the primary motor cortex synapse in the pons

Mossy Fibers

Afferent projections to the cerebral cortex

What type of projection is the spinothalamic tract?

Contralateral Projection (crosses)

What type of projection is the dorsal column pathway?

Contralateral projection (crosses)

What makes up the sensory compartment of the spinal cord?

Dorsal root ganglion neurons (pseudo unipolar cells with no dendrites and one axon with central and peripheral branches

Where are reticular formation neurons found?

In the core of the brainstem, primarily in the pons and medulla

Where do neurons of the ascending reticular activating system terminate?

In the thalamus that is conveyed to the cerebral cortex

What is the function of the reticular activating system?

Increased arousal in response to sensory information, maintains consciousness, and has a role in sleep wakefulness

What type of projection is the spinocerebellar tract?

Ipsilateral (doesn't cross OR crosses twice)

What layer of the cerebellum contains perkinje cells?

Molecular layer

What neurons are within the cerebral cortex?

Perkinje cells and granule cells.

What are potential side effects of a damaged cerebellum?

Possible issues include problems with balance and tremors

Granule cells

Project into molecular layer and form parallel fibers

What makes up the motor component of the spinal cord?

Somatic motor neurons, axons that exit in the ventral root

Conus medullaris

Tip of the spinal cord

What is the function of the spinothalamic tract?

To detect pain and temperature change

What is the function of the Dorsal Column Pathway?

To relay touch, pressure, and changes in proprioception

What is the function of the spinocerebellar tract?

Transmits information about position, movement of muscles

Climbing fibers

afferent projections to perkinje cells

cauda equina

collection of spinal nerves below the end of the spinal cord

purkinje layer

contains neurons that project into the cerebellum. Has enormous dendritic arborization

Filum terminale

filament, tough piece of connective tissue, covered in pia mater. Stabilizes the spinal cord on the inside of the vertebral column

Granular layer

form parallel fibers that synapse with with purkinge cells

Where do climbing fibers originate?

inferior olive

polysynaptic reflex

interneuron facilitates sensory-motor communication. Example is pulling hand away from hot object

perkinje cells

only neurons that project to the deep cerebellar nuclei

Where do deep Cerebellar nuclei neurons project?

out of the cerebellum

myosynaptic reflex

stretch reflex. Fastest of the reflexes, essential for balance and postural control. Example is seen with patella