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.
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? 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 semi- circular 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