Control and Coordination Chapter 21 Control and Coordination

Section 1- The Nervous System Homeostasis The regulation of steady, life-maintaining conditions inside an organism, despite changes in its environment. Neurons Working unit of the nervous system; a nerve cell Neurons consist of a cell body, axons, and dendrites. Dendrite Part of neuron; they receive messages and send them to cell body. Axon Part of neuron; it carries messages away from cell body. Synapse Small space between neurons

Types of Nerve Cells Motor Neurons Sensory Neurons Interneurons Conduct impulses from brain or spinal cord to body parts Sensory Neurons Receive info. and send impulses Interneurons Relay impulses to motor neurons

The Brain Coordinates all of your body activities. Cerebrum Cerebellum Thinking takes place Largest part of your brain Interprets impulses from the senses Cerebellum Part of the brain that coordinates your muscle movement. Helps maintain balance. Brain stem Connects brain to the spinal cord Includes the midbrain, pons, and the medulla Medulla- involuntary actions (heartbeat, breathing and digestion) Midbrain & pons- acts as pathways that connect various parts of the brain with each other

Spinal cord Controls reflex responses Ex. Withdrawing your hand from a hot stove, your foot from a sharp piece of glass, putting your hands out in front of you to stop a fall.

Central Nervous System (CNS) Peripheral Nervous System (PNS) Made up of the brain and spinal cord Peripheral Nervous System (PNS) Made up of nerves outside the central nervous system. Connects the brain and spinal cord to other body parts. Sensory neurons send impulses to the brain or spinal cord. 2 Major Division of PNS 1) Somatic 2) Autonomic Somatic- Voluntary Actions Autonomic- Involuntary Actions Reflex Involuntary, automatic response to a stimulus Stimulus Change that causes a response in your body

What steps happen when you run an iron over your hand accidentally? 1. You aren’t paying attention when you run the iron over your hand. 2. Sensory neurons in your hand send messages to interneurons. 3. Interneurons relay impulses to motor neurons 4. Motor neurons relay impulses to muscles of your hand. 5. Muscles of your hand contract, responding to the impulses. 6. You pull your hand away from the iron and scream.

Drugs and the Nervous System Caffeine is a stimulant A drug that speeds up the activity of the central nervous system. Increases heart rate Causes restlessness and insomnia Causes kidneys to produce more urine Alcohol is a depressant A drug that slows the activities of the central nervous system. Impairs judgment Destroys brain and liver cells

Section 2- The Senses Sense organs intercept different forms of energy, which are then converted into impulses by the nervous system. Your senses work together Maintain homeostasis within your body. Senses 1) Vision 2) Hearing 3) Smell 4) Taste 5) Touch

Vision How do you see???? Light enters the eye – cornea Next passes through the lens Lens directs light into the retina Tissue at back of eye that is sensitive to light energy Rods (respond to dim light) and cones (respond to bright light and color) are found in the retina. Light energy stimulates an impulse Optic Nerve- Carries impulses from the retina to the brain. http://glencoe.mcgraw-hill.com/sites/dl/free/0078617022/161752/00053402.html

Rods and Cones Lens Cornea Optic Nerve Retina

Hearing Sound energy is to hearing as light energy is to vision. When an object vibrates, sound waves are produced. Outer Ear Intercepts sound waves and funnels them into the ear canal

Middle Ear Eardrum vibrates Contains hammer, anvil, and stirrup Inner Ear Cochlea- fluid-filled structure in the inner ear Causes electrical impulses to be sent to the brain by a nerve

Smell Olfactory cells Nerve cells in the nose stimulated by molecules Kept moist by mucus

Taste Taste buds Major sensory receptors on the tongue In order to taste something, it has to be dissolved in water. Saliva begins this process. Smell and taste are related! Olfactory cells are stimulated through the back of your throat.

Other Sensory Receptors Skin sensory receptors are located throughout your skin. (Fingertips) You can tell whether an object is smooth or rough, hot or cold, hard or soft.