Question

Describe the components and general function of the basal ganglia and limbic system, midbrain, and hindbrain.

Answer 1

Basal Ganglia -

Basal ganglia form the part of extra pyramidal system, which is concerned with motor activities. Basal ganglia include three primary components:
1. Corpus striatum
2. Substantia nigra
3. Subthalamic nucleus of Luys.

Function -

1. Control of muscle tone - Basal ganglia control the muscle tone. In fact, gamma motor neurons of spinal cord are responsible for development of tone in the muscles. Basal ganglia decrease the muscle tone by inhibiting gamma motor neurons through descending inhibitory reticular system in brainstem. During the lesion of basal ganglia, muscle tone increases leading to rigidity.

2. Regulation of voluntary, consious and subconsious movement

3.Control of reflex muscular activity particularly visual and labyrnthine reflex to maintain body posture.

Limbic System -

Limbic system is a complex system of cortical and subcortical structures that form a ring around the hilus of cerebral hemisphere.

Structures of limbic system are classified into four groups

1. Archicortical structures --- Hippocampus and dentate Gyrus
2. Paleocortical structures --- Piriform cortex, Olfactory lobe
3. Juxtallocortical structures --- Cingulate gyrus
4. Subcortical structures -- Amygdaloid complex, Thalamic and hypothalamic nuclei, Caudate nucleus

Function of limbic system -

1. Olfaction- Piriform cortex and amygdaloid nucleus form the olfactory centres.

2. Control of circadian rhythm

3. Role in memory formation

4. Role in emotional state

Mid brain -

Midbrain or mesencephalon is the forward-most portion of the brainstem.
The Structural parts of the midbrain are

1.Tectum -- formed by superior and inferior colliculus

2. cerebral peduncles --- It includes Basal pedunculi, substantia nigra and tegmentum.

Function- It is associated with vision, hearing, motor control, sleep and wakefulness,alertness, and temperature regulation

Hindbrain also called rhombencephalon, is composed of Medulla oblongata, pons, and cerebellum.

The hindbrain coordinates functions that are fundamental to survival

Medulla Oblongata has Respiratory center, Vasomotor center (Blood pressure regulation), Deglutition center, vomitting center, cranial nerve nuclei for 9, 10, 11 and 12 th cranial nerve.

Pons contains cranial nerve nuclei for 5,6,7 and 8th cranial nerve.