Peripheral Nervous System

It’s made up of nerves that link to the CNS to the receptors and effectors of the body. 43 pairs of nerves that include: • 12 pairs of cranial nerves connected to the brain. These may be sensory (afferent) or motor (efferent) or mixed nerves made up of both sensory and motor nerves • 31 pairs of spinal nerves which enter and leave the spinal cord. These are all mixed nerves.

This system has a dual role: • It collects info from receptors and transmits this info by way of impulses along sensory, afferent neurons to the CNS — sensory function • It transmits impulses impulses from the CNS by way of motor, efferent neurons to the effectors to bring about an appropriate response — motor function

•  somatic nervous system that conducts impulses from the CNS to skeletal muscles, controls all voluntary muscular movements • Autonomic nervous system that conducts impulses from the CNS to smooth muscles and glands, therefore controls the functioning of involuntary muscles and glands

The ANS is largely involved in maintaining homeostasis. The ANS is made up of: • sympathetic nervous system • parasympathetic nervous system

• Sympathetic nervous system: works together with adrenaline in emergency situations that require “flight or fight”. Stimulation by these nerves results in more oxygen, glucose and blood being sent to the skeletal muscles where cellular respiration is sped up to release more energy for action • Parasympathetic nervous system enables the body to “rest and digest”. I.e. to recover from the sympathetic stimulation

• speed up or slow down heart and respiratory rate • adjust blood pressure and body temperature • shunts blood to areas where it is most needed • increases or decreases digestive secretions