Question

What constitutes the central and peripheral nervous systems? How are the components of central nervous systems protected?

Answer 1

Central nervous system (CNS):

The CNS consists of the brain and spinal cord.

1) Brain

1. Brain is the complex organ that controls the process of thinking, memory, sensory mechanism, voluntary and involuntary actions.
2. It has three main parts namely, forebrain, midbrain and hindbrain.

Important functions of brain:

1. It helps in processing the sensory impulses.
2. It helps in regulating blood pressure and breathing mechanisms.
3. It controls the activities of the hormonal system.
4. It helps in maintaining the body balance and homeostasis.
5. It takes care of the circadian rhythm, the sleep-wake cycle of the body.

2)Spinal cord

1. Spinal cord carries information between the brain and body.
2. It contains circuits that control certain reflexive responses.

Protection of the CNS:

1. The CNS is the processing centre of the body and consists of the brain and the spinal cord.
2. Both of these are protected by three layers of membranes known as meninges.
3. For further protection, the brain is encased within the hard bones of the skull, while the spinal cord is protected with the bony vertebrae of our backbones.
4. A third form of protection is cerebrospinal fluid, which provides a buffer that limits impact between the brain and skull or between spinal cord and vertebrae.

Peripheral nervous system (PNS):

The peripheral nervous system itself is divided into two parts: the somatic nervous system and the autonomic nervous system.

1)Somatic nervous system:

1. The somatic system is the part of the peripheral nervous system responsible for carrying sensory and motor information to and from the central nervous system.
2. Sensory nerves are unipolar that carry sensory information from sensory organs to the CNS.
3. Motor nerves are multipolar that carry motor impulses from the CNS to effector organs.

2) Autonomic nervous system:

1. The autonomic nervous system is a component of the peripheral nervous system.
2. It controls the involuntary movements of respiration, heartbeat and digestion.
3. It contains three components namely, sympathetic, parasympathetic, and enteric.
4. The sympathetic and the parasympathetic nervous system provide sensory and motor output, respectively, to the CNS.
5. The enteric nervous system is composed of reflex pathways that control the digestive functions.

Nerves in the Peripheral nervous system (PNS):

1)Cranial nerves:

1. The nerves that arise directly from the brain are called cranial nerves.
2. There are 12 pairs of cranial nerves that are special nerves associated with the brain.
3. They can be sensory, mixed or motor.
4. They are concerned mainly with the activities associated with head and neck.

2) Spinal nerves

1. Spinal nerves are the nerve fibers that are connected to the spinal cord and carry information from and away to the spinal cord.
2. They consist of 31 pairs of spinal nerves that connect the spinal cord to the periphery.
3. They are purely mixed.
4. They are concerned with all the body parts, below the neck.