Examination of the sensory system Enas Sabah MSc. Human Physiology

Special sensation Somatic sensation Types of sensations: special senses, are vision, hearing, smell, taste, and equilibrium. Detected only by specialized sensory receptors within large, complex sensory organs in the head.

The somatic senses ("soma" means body) are the nervous mechanisms that collect sensory information from all over the body. detect touch, pain, pressure, temperature, and tension on the skin and in internal organs

All senses are detected by sensory receptors, and after integration and processing in the central nervous system, motor nerves produce a response.

Classification of somatic senses A. Physiologic classification of somatic senses: 1.Mechanoreceptive sensation (touch, pressure, vibration, tickle) 2.Thermoreceptive sensation ( cold and warmth) 3.Pain sensation ( damage to the tissues anywhere) B. Other classification of somatic sensation: 1.Exteroreceptive senses ( from the surface of body) 2.Proprioceptive senses ( body position, joint position, tendon and muscle senses) 3.Visceral senses ( from internal organs) 4.Deep senses ( from deep tissues)

Pathways for transmission of sensory stimuli: Dorsal pathway Anterolateral pathway

Dorsal pathway Its composed of large, myelinated nerve fibers that transmit signals to the brain at velocities of 40 to 110 m/sec. has a high degree of spatial orientation (good localization) Dorsal pathway transmits the following senses: Touch and two point discrimination (1-2 mm on the finger tips and 30-70 mm on the back). pressure position vibration

Anterolateral pathway Its composed of smaller myelinated fibers that transmit signals at velocities ranging from a few meters per second up to 40 m/sec. has much less spatial orientation (poor localization). Anterolateral pathway transmits the following senses: pain thermal tickle and itch sexual sensations crude touch and pressure