Chapter 20:
The Nervous and Endocrine Systems
Pages 546 – 564
Date
Nervous System at Work (pg. 546 – 547)
1. Neurons = nerve cell – working unit of nervous system
1. Made up of a cell body & branches called dendrites & axons
2. Dendrites = receive messages & send them 2 cell body
3. Axon = carries messages away from cell body
1. Branches help carry messages
4. Impulse = messages carried by neurons
1. Sent across a small space (from axon 2 den) 2 another neuron =
synapse
5. Three types of neurons:
1. Sensory = receive info & send impulses 2 brain or spine
2. Motor = conduct impulses from brain/spine 2 muscles or glands
3. Interneurons = relay impulses from sensory 2 motor
Central Nervous (pg. 548 – 549)
Central nervous system (CNS) = brain & spinal cord
2. Peripheral nervous system = all nerves outside of CNS
1. These systems work together 2 coordinate body activities
2. Brain has three major parts:
3. Cerebrum = largest part, divided into hemispheres, memory
is stored, voluntary muscles R controlled, senses are
interpreted
4. Cerebellum = behind cerebrum, maintains balance &
voluntary muscle movements
5. Brain stem = connects the cerebrum to spinal cord, controls
heartbeat, breathing, blood pressure, involuntary movements
3. Brain is made up of 100 billion neurons
1.
Reflexes (pg. 551)
1. Reflex = involuntary and automatic response to a
stimulus
1. Involves a simple nerve pathway called a reflex
arc
2. U touch something hot, sensory receptors in
finger send an impulse 2 spine, impulse passes 2
an interneuron in spine that immediately relays
that info 2 a motor neuron, motor neurons
transmit impulse 2 muscles  U move hand
Drugs and the Nervous System
(pg. 552)
Alcohol is a depressant drug, which slows down the nervous
system (N.S.)
1.
1.
2.
It is absorbed into bloodstream through walls of stomach & small
intestine
Heavy alcohol use can destroy brain & liver cells
Depressant = slows down activities of N.S.: judgment, reasoning,
memory, concentration, muscle functions
2.
1.
Other depressants: marijuana, benzodiazepines
Caffeine is a stimulant drug, which speeds up the N.S.
3.
1.
There is also a physical dependence noticeable once people stop
Stimulant = speeds up activities: heartbeat rate, restlessness,
tremors, insomnia, kidneys produce more urine
4.
1.
Other stimulants: nicotine, cocaine, amphetamines
The Senses (pg. 554 – 556)
Hearing: objects vibrate making air around vibrate, producing sound
waves, which stimulate nerve cells in your ear  impulses travel 2
brain 2 recognize the sound
1.
Outer ear: traps sound waves & funnels them 2 middle ear
Middle ear: vibrations move three bones: hammer, anvil, & stirrup
Inner ear: cochlea  fluid filled structure shaped like a snail shell
1.
2.
3.
1.
When sound waves vibrate this fluid, it stimulates nerve endings
Vision: light enters eye, which the lens & cornea bend toward the
retina = a tissue @ the back of eye that is sensitive 2 light energy
2.
1.
2.
3.
Cones = respond 2 bright light & color
Rods = respond 2 dim light
Light energy creates impulses 2 the optic nerve, which carries them 2
the brain where they are interpreted
Smell & Taste (pg. 558 – 559)
Smell: Things that smell give off molecules into the air, which go
through nasal passageways which contain sensitive nerve cells called
olfactory cells that are stimulated by gas molecules
1.
1.
Taste: taste buds on your tongue are the major sensory receptors for
taste
2.
1.
2.
3.
3.
Then an impulse is sent to brain for interpretation
Four basic taste sensations = sweet, salty, sour, & bitter
Saliva helps with taste as it washes over the taste buds and an impulse is
sent 2 your brain for interpretation
Taste & smell R related  with a stuffy nose, nasal passages R blocked
Your senses help send impulses 2 your brain regarding your
environment, this allows your brain 2 respond & maintain
homeostasis
Endocrine System (pg. 562 – 564)
The endocrine system uses chemicals 2 control your body
1.
1.
Hormones = endocrine chemicals produced in glands throughout
body
Hormones affect target tissues which R usually located in
another part of the body, which makes the endo system slower
than nervous
2.
1.
Ex: pancreas, which produces insulin enables cells 2 take in
glucose
Diabetes is one of the most common diseases worldwide, and it is estimated that about 346
million people suffer from this disease. (WHO, 2011).
All Done!