BPK 105 Study Guide - Midterm Guide: Substantia Nigra, Striatum, Cerebral Cortex
27 Apr 2018
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Module 4 - Objectives - Part 7
● Discuss how the basal nuclei and cerebellum regulate motor functions.
basal nuclei: group of functionally related nuclei (figure 8.30).
- Two primary nuclei are the corpus striatum, located deep within the cerebrum, and the
substantia nigra, a group of darkly pigmented cells in the midbrain.
- important in planning, organizing, and coordinating motor movements and posture.
- Complex neural circuits link the basal nuclei with each other, with the thalamus, and with
the cerebral cortex.
- These connections form several feedback loops, some of which are stimulatory and
others inhibitory.
- The stimulatory circuits facilitate muscle activity, especially at the beginning of a
voluntary movement, such as rising from a sitting position or beginning to walk.
- The inhibitory circuits facilitate the actions of the stimulatory circuits by inhibiting
muscle activity in antagonist muscles.
- inhibitory circuits inhibit random movements of the trunk and limbs. Inhibitory circuits
also decrease muscle tone when the body, limbs, and head are at rest.
- Disorders of the basal nuclei result in difficulty rising from a sitting position and difficulty
initiating walking.
- People with basal nuclei disorders exhibit increased muscle tone and exaggerated,
uncontrolled movements when they are at rest.
- A specific feature of some basal nuclei disorders is “resting tremor,” a slight shaking of
the hands when a person is not performing a task.
Cerebellum:
- attached to the brainstem by several large connections called cerebellar peduncles
- The connections provide routes of communication between the cerebellum and other
parts of the CNS.
- involved in maintaining balance and muscle tone and in coordinating fine motor
movement.
- If the cerebellum is damaged, muscle tone decreases, and fine motor movements
become very clumsy.
- Action potentials from the cerebral motor cortex descend into the spinal cord to initiate
voluntary movements.
- Collateral branches are sent from the motor cortex to the cerebellum, giving information
representing the intended movement.
- simultaneously, reaching the cerebellum are action potentials from proprioceptive
neurons, which innervate joints, tendons, and muscles and provide information about
the position of body parts.
- cerebellum compares information about the intended movement from the motor cortex to
sensory information from the moving structures.
- If a difference is detected, the cerebellum sends action potentials to motor neurons in
the motor cortex and the spinal cord to correct the discrepancy. The result is smooth and
coordinated movements.
Document Summary
Discuss how the basal nuclei and cerebellum regulate motor functions. basal nuclei : group of functionally related nuclei (figure 8. 30). Two primary nuclei are the corpus striatum , located deep within the cerebrum, and the substantia nigra, a group of darkly pigmented cells in the midbrain. important in planning, organizing, and coordinating motor movements and posture. Complex neural circuits link the basal nuclei with each other, with the thalamus, and with the cerebral cortex. These connections form several feedback loops, some of which are stimulatory and others inhibitory. The stimulatory circuits facilitate muscle activity , especially at the beginning of a voluntary movement, such as rising from a sitting position or beginning to walk. The inhibitory circuits facilitate the actions of the stimulatory circuits by inhibiting muscle activity in antagonist muscles. inhibitory circuits inhibit random movements of the trunk and limbs. Inhibitory circuits also decrease muscle tone when the body, limbs, and head are at rest.
