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THE BRAIN AND THE SENSES SECTIONS 35-2 and 35-3 What were the divisions of the nervous system? • Central Nervous System a. Brain and Spinal Cord b. Interprets all information from sensory nerves and sends responses to the motor nerves. • Peripheral Nervous System a. Sensory nerves – 5 senses, picks up stimuli and sends to CNS. b. Motor nerves – voluntary or involuntary, carries out response sent by CNS. Neuron types: Sensory, Interneurons, Motor The Brain • Consists of mainly interneurons • Five main structures: 1. Cerebrum – largest section, intelligence, learning and judgment. All voluntary activities. 2. Cerebellum – coordination of voluntary movements. 3. Brain Stem – controls vital functions for life 4. Thalamus – Relay station for incoming sensory info. 5. Hypothalamus – Controls hunger, thirst, fatigue, body temperature. Comparing Human, Dog and Rat Brains Cerebrum • Two hemispheres • • • • • connected by the corpus callosum Four Lobes: Frontal – movement, problem solving, rational, personality Parietal – sensations and perceptions Occipital – vision Temporal – hearing, language, memory Functions of the Cerebrum Brain Stem Three sections: 1. Midbrain 2. Pons 3. Medulla Oblongata –regulates heart rate, blood pressure, respiration, coughing, sneezing, vomiting, swallowing Spinal Cord • Thick rope of interneurons • Main communication line to brain • 31 pairs of spinal nerves • Herniated disc – swelling of intervertebral discs, pinches spinal nerves Paralysis is when movement in lost. Depends on where the cord/nerve is injured. Reflexes Rapid, automatic responses to specific stimuli. Their purpose is to preserve homeostasis. Only a few neurons are needed. Why do doctor’s test reflexes? What is the advantage of having reflexes? THE SENSES Section 35-4 The Senses • Part of the PNS – sensory division • Five types of sensory receptors: 1. Pain receptor 2. Thermoreceptor 3. Mechanoreceptor 4. Chemoreceptor 5. Photoreceptor • 5 organs for sensory perceptions Where in the body are these receptors located and what type of stimulus do they respond to? The Skin 1. Touch and Pressure (mechanoreceptors) - Light and strong receptors 2. Temperature (thermoreceptors) - Warm and cold free nerve endings 3. Pain Receptors (nociceptors) - Respond to all types of stimuli The Eye • Rods and cones are the • • • • photoreceptor cells Located in the retina Rods – peripheral and low light vision Cones – color vision and greatest acuity Optic nerve sends signals to brain; no photoreceptors Where are all the parts of the eye? Their functions? The Ear • Mechanoreceptors are ciliated cells • Function: hearing and balance • Hearing comes from cochlea - vibrations in air are conducted to the: tympanum to ossicles to cochlea to auditory nerve to brain • Balance come from semicircular canals - bending or rotating of head moves fluid in canals Eustachian tube – equalizes pressure, connects with throat Smelling Chemoreceptors – stimulated by chemicals Olfactory cells – sensory cells for smell Low threshold (only a few molecules needed to detect) Watery mucus lines cells to act as solvent. Olfactory bulb sends impulses to olfactory cortex region of brain. • Anosmia – loss of sense of smell • Helps with taste perception. • • • • • Taste • Chemoreceptors – picks up chemical • • • • stimuli Molecules must be dissolved in a solvent to activate receptors. Saliva is the solvent! Taste receptors are called “gustatory cells” Gustatory cells found in taste buds all over tongue/mouth • So, a single taste bud has many gustatory cells. • 5 main tastes: salty, sweet, sour, bitter, umami