The Nervous System

Vertebrates have a spinal column or backbone. Vertebrates have neurons that are outside that spinal column called Peripheral Neurons and neurons inside the spinal column and head called Central Neurons. i) Peripheral Neurons a) Efferent Nerves (motor nerves) send signals from central nerves to effector organs; b) Afferent Nerves (sensory nerves) send signals from sensory receptor to the central nervous system. ii) Central Nervous System (CNS) is made up of your brain and spinal cord; both are made up of cells called neurons; most neurons are Interneurons, which connect all neurons together; nerves are bundles of neurons Reflex Arc Since your spinal cord is part of your brain, it is able to make quick decisions to ensure the safety of the organism. These decisions are called Reflex Arcs and involve the connection of stimulus to a response through the shortest path. This path is usually: Receptorsensory neuroninterneuronmotor neuroneffector organ Example: pain reflex, pupil reflex, Babinski reflex, Moro reflex Mechanoreceptors Mechanoreceptors detect movement.

Your ears detect movement of air called sound waves. Your skin has mechanoreceptors too. Both ear and skin receptors are implanted in the roots of hairs. As the hair moves, the receptor detects the movement. Ear The ears have tiny hairs in the Cochlea. The cochlear hairs resonate at the same frequency as pitches of sounds. Your brain receives messages from those receptors and interprets the sound. Deafness If the sound vibration is stopped at any point, the Conduction (transmission) of the signal is broken. This is called Conduction Deafness. It occurs because of damage to the auricle and pinna, tympanic membrane, hammer, anvil, stirrup, oval window, on the cochlea. If the acoustic or auditory nerve becomes damaged, deafness also occurs.

This is called nerve deafness. Chemoreceptors We have two types of chemoreceptors. They form our sense of smell and taste. 1) Smell: All chemoreceptors must be bathed in liquid (or mucus) because the chemical being sensed must be in a solution. Olfactory cells are special receptors in the nose, which detect chemicals in the air. 2) Taste: These receptors are on the tongue. They detect only five different chemicals causing taste, they are: bitter, sweet, salty, bitter and picante. Taste receptors are called taste buds. Flavors are a combination of both tasting and smelling at the same time.