Chapter 7 – The Peripheral Nervous System

Lesson 1 Chapter 7 – The Peripheral Nervous System Unit 7 Study Guide Excluded from reading: Chapter 4: Pages 155 – up to 157 The Peripheral Nervous System Sensation: an impression produced by impulses conveyed by an afferent nerve to the sensorium. Somatic motor function (skeletal muscles) Autonomic function (smooth muscles, cardiac muscles, and glands) Receptors  Spinal Cord  Thalamus  Parietal lobe Basic structural components of the Peripheral Nervous System - Sensory receptors pick up stimuli from inside or outside the body. - Nerves and ganglia: Nerves are bundles of peripheral axons. Ganglia are clusters of peripheral neuronal cell bodies. - Motor endings are axon terminals of motor neurons and they innervate effectors. (Muscles are effectors) 1 Lesson 1 Chapter 7 – The Peripheral Nervous System 2 Four divisions of the Peripheral Nervous System (PNS) - Somatic sensory system are widely spread throughout the body that deal with touch, pain, vibration, pressure, temperature, proprioception, hearing, balance and vision. Somatic motor system deals with voluntary skeletal muscle contractions Visceral sensory system deals with stretching, pain, temperature, nausea, hunger, taste and smell. Visceral motor system deals with the involuntary contraction of smooth and cardiac muscle. This includes the sympathetic division (fight or flight) and parasympathetic division (rest and digest) which include the autonomic nervous system. Afferent division o Sends information from internal and external environment to CNS  Sensory afferent  Somatic (body sense) sensation o Sensation arising from body surface and proprioception  Special senses o Vision, hearing, taste, smell  Visceral afferent  Incoming pathway for information from internal viscera (organs in body cavities) Types of Receptors • Chemoreceptors – • Photoreceptors – • • sensitive to changes to pH and O2 and CO2 Responsive to visible wavelengths of light Mechanoreceptors – Sensitive to mechanical energy – Changes to pressure – Eg. Baroreceptors (carotid, aorta) Thermoreceptors – Sensitive to heat and cold Lesson 1 Chapter 7 – The Peripheral Nervous System Types of Receptors According to Their Speed of Adaptation • Receptors may adapt slowly or rapidly to sustained stimulation – Tonic receptors: Do not adapt at all or adapt slowly – Muscle stretch receptors, joint proprioceptors – Phasic receptors: Rapidly adapting receptors  – Tactile receptors in skin – Phasic: putting clothing on, eventually you won’t notice it. Sensory afferent o Somatic (body sense) sensation  Sensation arising from body surface and proprioception o Special senses  Vision, hearing, taste, smell 3