Control and Coordination Chapter 21 Control and Coordination

Ch 21.1 – The Nervous System A. Your nervous system helps your body make adjustments to changes in your environment 1. Stimulus – any change inside or outside the body that brings about a response 2. Homeostasis – the regulation of steady internal conditions inside an organism

B. Neurons – (nerve cells) made up of a cell body and branches to transmit signals

1. Dendrites – branches that receive messages and send to the cell body 2. Axons – branches that carry messages away from the cell body to the next neuron

3. Messages carried by nerve cells are called impulses

4. There are 3 kinds of nerve cells a) Sensory – receive information and send impulses to brain or spinal cord b) Interneuron – interpret impulse and relay to next cell type c) Motor – conduct impulses from brain to muscles or glands to bring about response

Reflex Arc

5. Nerve cells do not touch each other, yet impulses still pass from one to the next a) Synapse – the space b/w nerve cells b) When an impulse reaches the end of an axon it releases chemicals (Sodium & Potassium) c) The chemical flows across the synapse to relay the impulse to the next dendrite

C. Central Nervous System (CNS) – made of brain & spinal cord 1. Brain - coordinates ALL body activities a) Cerebrum – largest part; interprets impulses from senses, stores memory, controls movements and has outer covering called cortex that allows thinking to take place

Cerebrum (Imagination) (Memory) (Memory) (Tactile Senses) (Emotions, Judgment) (Memory) (Memory)

b) Cerebellum – located behind & under cerebrum; coordinates voluntary muscle movement and maintains muscle tone & balance

c) Brain Stem – part of brain that extends from cerebrum to the spinal cord; made of 3 parts: 1) Midbrain & Pons – pathways that pass signals b/w different parts of brain 2) Medulla – controls involuntary actions such as heartbeat, breathing & BP

Brain Stem

2. Spinal Cord – made of bundles of nerve cells that carry impulses to and from the brain

D. Peripheral Nervous System (PNS) – made of all the nerves that extend from spinal cord to rest of body 1. Somatic division – controls voluntary actions 2. Autonomic division – controls involuntary actions

E. Any injury to the brain or spinal cord can be serious 1. Injury to the spinal cord may result in paralysis 2. Injury to brain may result in a concussion, permanent brain damage or even coma 3. Safety gear in cars and sports is an important preventative measure

E. Reflex – any involuntary, automatic response to a stimulus controlled by brain and spinal cord

G. Drugs have effects on nervous system 1. Alcohol – slows down activities of CNS 2. Caffeine – speeds up activities of CNS

Ch 21.2 - Senses A. Light rays, sound waves, heat, chemicals or pressure that come into your personal territory stimulate your sense organs B. Your body has 5 senses:

1. Vision a) Light enters eye though cornea and pupil and the lens focuses it on the back wall of the eye called the retina

b) The light stimulates rods and cones (cells) on the retina and sends impulses over the optic nerve to the visual area of brain c) The visual area of the cortex interprets the image you “see”

d) Nearsightedness – occurs when light focuses in front of retina; corrected with concave lens

e) Farsightedness – occurs when light focuses behind the retina; corrected with convex lenses

2. Hearing a) When objects vibrate they create waves b) These sound waves are caught by in outer ear and funneled down the ear canal

c) Middle Ear – at end of canal sound waves strike the ear drum and sends the vibrations through 3 tiny bones – hammer, anvil, stirrup

d) Inner Ear – the vibrations pass through a fluid in the cochlea which send nerve impulses to the brain where sound is interpreted

e) Fluid of the cristae ampullaris and maculae of the middle ear help control balance

3. Smell a) Food and other objects give off molecules into the air b) These molecules stimulate nerve cells called olfactory cells in the nasal passage c) These cells send impulses through olfactory nerve to bran where they are interpreted

4. Taste a) Taste buds (about 10,000) in mouth are the major sensory receptors for taste b) When a solution of saliva and food washes over the taste buds impulses are sent to the brain

Umami – 5th taste; Japanese for savory/delicious; associated w/hearty foods like meat cheese and mushrooms (foods w/MSG monosodium glutamate)

5. Touch a) Sensory receptors on nerve cells in the skin and internal organs b) They pick up changes in touch, pressure, pain and temperature and send impulses to brain