The Peripheral Nervous System

1. The Peripheral Nervous System

2. The Peripheral nervous system • This nervous system includes the somatic nervous system and the automatic nervous system. The motor nerve fibers that connect the spinal cord to the straited muscle and sensory nerve fibers compose the somatic nervous system. The motor system serving the smooth muscles is the automatic nervous system. • The two main divisions that compose • Sympathetic system • Parasympathetic system

3. Sympathetic system – consist of a group of nerve fibers running longitudinally along both sides of the spinal cord and adjacent to the thorax and lumbar regions. • Parasympathetic system – is the day-to-day control of the individual functions of bodily organs. It is compose of cranial nerves in the brain stem and sacral nerves below the lower back.

4. Nervous system Peripheral Nervous System Central Nervous System Somatic division Autonomic Division Brain Spinal cord Sympathetic (emergency activation) Parasympathetic (After Emergency)

5. The reflex • Reflex responses which are chains consisting of a sensory organ and three nerve cells are produced automatically by the body and they serve to protect the organism and preserves its life. Examples of these are knee jerk, pupil constriction, withdrawal of the body or any of its parts from a very hot or cold object, scratching, breathing, and stretching. All reflex behavior involves a similar chain of events. Stimulus activates a receptor cell. The receptor cell sends a nerve impulse through a sensory neuron to a place of control. A motor neuron receives a response impulse from the place of control and carries it to an effector .

6. In this respect, the reflex behavior is similar to more complex behavior patterns. However, the reflex differs in two ways: First the reflex circuit operates fairly automatically; second, in most cases the center for processing the impulses of reflex stimulation is in the spinal cord, not in the brain. The circuit through which nerve impulses travel is called the reflex arc. When the brain is not involved in a reflex response, the process is called a spinal reflex and the circuit is called sensorimotor arc. Brain controlled reflex permit more complex and variable combinations of responses than those controlled by the spinal cord.

8. Summary of the major functions of the nervous system • Central Nervous System • Brain and spinal cord – Receives impulses from the sensory nerves, provides interneuron connections, transmits impulses to motor nerves. • Peripheral Nervous System • Somatic (sensorimotor nerves) – Transmit impulses from receptors to brain and spinal cord, transmit impulses to striated muscles from brain and spinal cord. • Autonomic Nervous System • Sympathetic and parasympathetic divisions – Transmit impulses from brain to smooth muscles.

9. It can be seen from the above that eash system serves the other. One system cannot function without the other; hence, they are said to be interacting systems. Thus, in psychology, discussions of behavior are not limited to the activity of the brain, the spinal cord, the sense organs, or the muscles and glands. Behavior is regarded as a function of the whole organism. • (Thank You………….)