Central and Peripheral Nervous System: Functions and Coordination

Central Nervous System (CNS)

The CNS receives information from all over the body. It interprets this information and uses it to control the body's systems. The CNS consists of the brain and the spinal cord. The brain and the spinal cord are surrounded by three membranes called meninges. The CNS is mostly made up of two types of tissue:

• Grey matter: This is mainly neuron cell bodies and dendrites.
• White matter: This is mainly nerves. These are long cables containing axons, covered in a substance called myelin.

Brain

The brain is the control center of the body and has several key parts:

• Cerebrum

  The cerebrum interprets information from the sense organs. It also controls language, memory, and thought. It produces voluntary responses, which are responses we perform by thinking. It is the largest part of the brain.

• Cerebellum

  The cerebellum controls our movements and helps us keep our balance.

• Brain Stem

  The brain stem controls basic movements that keep us alive (heartbeat, breathing, etc.). We perform these automatically, even when we are asleep. It is the part of the brain that is connected to the spinal cord.

Summary of brain functions:

• It processes information from sensory organs.
• It works out responses to stimuli and sends out appropriate commands to effectors.
• It regulates the functions of every part of the nervous system.
• It controls advanced functions like memory, reasoning, intelligence, and conscience.

Spinal Cord

The spinal cord is a very thick nerve protected by the vertebral column. It sends signals to and from the brain. It sends orders so that the effectors carry out involuntary responses or reflexes. These permit us to react quickly and without thinking.

Peripheral Nervous System (PNS)

The PNS is all of the nervous system that is outside of the brain and the spinal cord. It connects the sense organs to the central nervous system and the central nervous system to the effectors. The PNS has three main components:

• Sensory receptors: These sensory organ cells react to stimuli and then convert this reaction into a nerve impulse.
• Sensory nerves: They send the sensory nerve impulse to the CNS, which processes it and orders a motor response.
• Motor response: They transmit the response nerve impulse from the CNS to the effectors to cause a motor action.

Nerve Actions

The neurons in the different parts of the nervous system form many complex nerve pathways. The nerve impulses that circulate through these pathways produce two types of actions:

• Reflexes: These are quick, automatic actions that happen when a rapid response is required, for example, pulling your hand away from fire. Reflexes don't involve the brain; they only involve the spinal cord.
• Voluntary actions: These actions are slower and more elaborate than reflexes. The cerebral cortex has a key role in voluntary actions.

Endocrine Coordination

Endocrine coordination is a mechanism that regulates the actions of many of the body's organs in a slow but prolonged manner. It is carried out by the endocrine system, which is composed of a series of endocrine glands that produce and secrete hormones.

The main glands that form part of the endocrine system are the pituitary, the thyroid, the parathyroid, the adrenal glands, the pancreas, the testicles, and the ovaries.