Lakhmir Singh Test: Control & Coordination - Class 10

Pituitary gland is called master gland because it controls the secretion of all other endocrine glands.

Cerebral is centre of thinking, will power, reasoning and memory, experience and learning knowledge and articulate speech.

The cerebellum is located behind the brain stem. While the frontal love controls movement, the cerebellum " fine - tunes " this movement. This area of the brain is responsible for fine motor movement, balance and thr brain's ability to determine limb position.

The cerebrum, the large, outer part of the brain, controls reading, thinking, learning, speech , emotions and planned muscle movements like walking.

Synapse, also called Neuronal junction, the site of transmission of electric nerve impulses between two nerve cells or between a neuron and a gland or muscle cell.

Olfactory means related to smell hence olfactor receptors help to respond to smell.

The central nervous system (CNS) controls most functions of the body and mind. It consists of two parts: the brain and the spinal cord.

The brain is the center of our thoughts, the interpreter of our external environment, and the origin of control over body movement. Like a central computer, it interprets information from our eyes (sight), ears (sound), nose (smell), tongue (taste), and skin (touch), as well as from internal organs such as the stomach.

The cerebrum is a large part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system. The prosencephalon is the embryonic structure from which the cerebrum develops prenatally.

Motor Neurons- Motor neurons carry impulses from the CNS to effector organs Motor neurons are also called efferent neurons. The cell bodies of motor neurons are inside the CNS.

The distal end of the axon terminals have swollen ends to form “ bulbs” which store chemicals called neurotransmitters. These are responsible for passing the impulse from one neuron to another or from a neuron to a tissue. (Acetylcholine is an important neurotransmitter.)

Nodes of Ranvier are microscopic gaps found within myelinated axons. Their function is to speed up propagation of action potentials along the axon via saltatory conduction. The Nodes of Ranvier are the gaps between the myelin insulation of Schwann cells which insulate the axon of neuron.

Afferent neurons carry signals towards the CNS – afferent means “towards”. They provide information about the external environment and the regulatory functions being carried out by the nervous system.

An afferent neuron has a receptor at its ending that generates action potentials in response to a particular stimulus. These action potentials are transmitted along the length of the axon towards the spinal cord (which is part of the CNS).

Myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier that occur between the myelinated internodes. It is by this restriction that saltatory conduction propagates an action potential along the axon of a neuron at rates significantly higher than would be possible without the myelination of the axon (150 m/s compared to 0.5 to 10 m/s). As sodium rushes into the node it creates an electrical force which pushes on the ions already inside the axon. 

Brain cells remain in the beginning stage of interphase of cell reproduction for their life and never divide and instead develop by forming new synapses with other neurons. They lack cellular machinery for cell division. 

Schwann cells are a variety of glial cells that keep peripheral nerve fibres (both myelinated and unmyelinated) alive. In myelinated axons, Schwann cells form the myelin sheath. The sheath is not continuous. During peripheral nerve regeneration, 9-O-acetyl GD3 is expressed by Schwann cells.

Myelinated and unmyelinated nerve fibers are the two forms of nerve fibers that are found in the nervous system. The main difference between myelinated and unmyelinated nerve fibers is that myelinated nerve fibers contain a myelin insulation whereas unmyelinated nerve fibers do not contain a myeline insulation.

The longest part of a motor neuron is the axon. The axon is an extension that comes out of the cell body and travels long distances to reach a muscle or gland. Axons allow electrical signals to travel long distances quickly and deliver action potentials to trigger for example the muscular contraction.

The basal ganglia is found in the white matter. The cerebrum is divided in to left and right hemispheres. The left half controls the right side of the body and the right half controls the left side of the body. A mass of nerve fibers known as the corpus callosum connects the two hemispheres and allows communication between the two. The surface of the cerebrum is made up of gyri and sulci.

Coordination of Movement-the cerebellum controls the timing and pattern of muscle activation during movement.

Anatomical Lobes

There are three anatomical lobes that can be distinguished in the cerebellum; the anterior lobe, the posterior lobe and the flocculonodular lobe. These lobes are divided by two fissures – the primary fissure and posterolateral fissure.

The box enclosing and protecting the brain is called as the cranium. The cranium is the part of the skull, that encloses the brain. It is sometimes called as the braincase.

The four cavities of the human brain are called as ventricles. The two largest are the lateral ventricles in the cerebrum. These first and second ventricles present in two cerebral hemispheres is called as the paracoel.

All the body's voluntary actions are controlled by the motor cortex in the frontal lobe of the cerebrum.