Question

Review the functions of the CNS as it controls the physiological processes of the body. Consider the following system

Control of respiration – rate of breathing and depth of ventilation

Answer 1

Nervous system

Nervous system is the part of the body that controls the normal physiological functions occurring throughout the organism. It can be divided into two main parts. The nerve cell or neuron forms the basic unit of nervous system

1. Central nervous system CNS
2. Peripheral nervous system PNS

Central nervous system

CNS consist of the brain and spinal cord. It act as an Control center that regulates the entire bodily activities according to the stimulus.

Brain receives the sensory impulses from different parts of the body and spinal cord through sensory neurons integrates them and responds to these impulses through motor neurons .Responses can be brought about either consciously or unconsciously. Brain is enclosed with in the bony cranium submerged In cerebrospinal fluid and divided into different parts. Brain subdivided into  forebrain, midbrain and hindbrain based on the embryonic development.It consists of three main parts cerebrum, cerebellum and brainstem.  

1. Cerebrum is the largest part divided into right and left cerebral hemispheres which forms the highest centre of speech, memory,learning, emotions and reasoning.
2. Cerebellum forms the remaining part of brain and act as the centre for coordinating voluntary movements.
3. Brainstem mailing act as a relay centre connecting the other two parts of the brain with the spinal cord. Contains higher control centres of autonomic activities such as breathing, heatrate, body temperature,digestion etc.

Spinal cord: is the continuation of the lower brainstem outside the cranial cavity protected by the vertebral column. It helps in conduction of sensory impulses from different parts of the body to brain and also impulses from motor cortex to the effector organs. It also independently Control reflexes.

Peripheral nervous system: is made upon of nerves extending from the spinal cord that runs throughout the body.

Control of Respiration

Respiration is under controlled by both of Neural mechanism and chemical regulation by baroreceptors. Respiration is partly voluntary and mainly involuntary.

Neural Control

• Autonomic control located in pons and medulla
• voluntary control centre located in cerebral cortex.
• The medulla oblongata and the pons of the brain stem are responsible for the control of respiration.
• They maintain the rhythmic Respiration
• Respiratory centres in both of them monitors the level of oxygen and carbon dioxide in blood.
• Medulla oblongata contains the inspiratory and expiratiry respiratory centers
• Pond contain the pneumotaxic and apneustic centre
• Inspiratory centres called as dorsal group controls the inspiration
• Expiratory centres called as ventral group remains inactive during normal respiration and active only during forced Respiration.
• Pneumotaxic centre controls the duration of inspiration and activity of inspiratory centre. They inhibit the activity of apneustic centre
• Apnuestic centre act on the inspiratory centre and control depth and duration of Respiration.

Pathway

Afferent impulses are carried by the glossopharyngeal and vagus nerve to the respiratory centres. Efferent pathway consists of nerves carrying impulses from the respiratory centres to the spinal cord from there to the target , diaphragm and intercostal muscles through effector neurons. Phrenic nerve fibers carry impulses to the diaphragm and intercostal nerve fibers carry impulses to the intercostal muscles.