Chapter 8 Unit Notes
Lesson 1: The Nervous System
brain stem controls involuntary functions
central nervous system made of the brain and spinal cord
cerebellum coordinates voluntary muscle movement and regulates balance and posture
cerebrum controls memory, language, and thought
nervous system gathers, processes, and responds to information
neuron basic functioning unit of the nervous system
peripheral nervous system sensory and motor neurons that transmit information between the central
nervous system and the rest of the body
physical relating to material things
spinal cord tube-like structure of neurons
stimulus change in an organism’s environment that causes a response
synapse gap between two neurons
A. Functions of the Nervous System
1. The part of an organism that gathers, processes, and responds to information is the nervous
system.
2. A(n) stimulus is a change in an organism’s environment that causes a response.
3. Because people are constantly reacting to changes in their environments, the nervous
system helps maintain homeostasis, or the regulation of their internal environment.
B. Neurons
1. The basic functioning units of the nervous system are neurons.
2. Nerve cells have the following three parts: Dendrites receive information from another
neuron or from another cell in your body; the cell body processes information; and the
axon sends information to other cells in the body.
3. Sensory neurons send information about the environment to the brain or spinal cord.
4. Motor neurons send information from the brain or spinal cord to tissues and organs in
the body.
5. Interneurons connect sensory and motor neurons. The gap between two neurons is called a(n)
synapse.
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reflex automatic movement in response to a stimulus
C. The Central Nervous System
1. The central nervous system has two parts: the brain and the spinal cord.
2. The CNS (central nervous system) receives, processes, stores, and transfers
information.
3. The part of the brain that controls memory, language, and thought is the cerebrum.
4. The part of the brain that coordinates voluntary muscle movement and regulates balance
and posture is the cerebellum.
5. The area of the brain that controls involuntary functions is the brain stem.
6. The spinal cord is a tube-like structure of neurons. It sends information back and forth
between the brain and the rest of the body.
D. The Peripheral Nervous System
1. The peripheral nervous system has sensory neurons and motor neurons that transmit
information between the CNS and the rest of the body.
2. The somatic system of the PNS (peripheral nervous system) controls skeletal
muscles.
blood vessels and the beating of the heart. It also controls cardiac muscles and
smooth muscles.
E. Nervous System Health
1. Physical injuries are the most common way the nervous system can be damaged.
2. Paralysis is loss of muscle function and sometimes loss of feeling. The injured nerves
can no longer send and receive signals.
3. An automatic movement in response to a stimulus is a(n) reflex.
4. Many drugs affect the nervous system by speeding up or slowing down the
communication between neurons.
F. The Nervous System and Homeostasis
1. The body maintains homeostasis by receiving information from the environment and
responding to it.
2. The nervous system senses changes in the environment and signals other systems to make
adjustments.
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3. The autonomic system of the PNS regulates involuntary actions such as dilating
Lesson 2: The Senses
eardrum thin membrane between the outer ear and the inner ear
receptor special structure within the sensory system that detects stimuli
retina area at the back of the eye that contains photoreceptors
rod photoreceptor in the eye that distinguishes shapes of objects
sensory system part of the nervous system that detects or senses the environment
wave disturbance that transfers energy without transferring matter
A. You and Your Environment
1. The sensory system is the part of the nervous system that detects the environment.
2. A human uses five senses—vision, hearing, smell, taste, and touch—and detects his or her
environment.
3. All parts of the sensory system have special structures called receptors that detect stimuli.
B. Vision
1. The lens and cornea of the eye work together to focus light onto the retina.
2. The retina is an area at the back of the eye that has two types of cells with
photoreceptors—rod cells and cone cells.
a. Rod cells detect shapes and low levels of light.
b. Cone cells detect color and bright light.
3. The retina takes information about objects the eye sees and sends it as electrical signals
through the optic nerve to the brain.
4. The brain uses information from the eye and creates a picture of what the person is seeing.
5. Glasses or contacts can be used to correct vision problems by correctly focusing light on
the retina.
C. Hearing
1. The vibration of matter creates sound waves, which can travel through air and other
substances.
2. The outer ear collects sound waves that make the eardrum vibrate.
3. The eardrum is a thin membrane between the outer ear and the middle ear.
4. The inner ear converts sound waves into messages that are sent to the brain.
5. Fluid-containing parts of the inner ear, the semicircular canals, help maintain balance.
D. Smell
1. Humans have hundreds of receptors for detecting smell.
2. Odors are molecules that can be detected by chemoreceptors in the nose.
E. Taste
1. Chemoreceptors on the tongue are called taste buds.
2. Chemoreceptors in the nose and mouth work together to produce the sense of taste.
F. Touch
1. Touch receptors in the skin can detect temperature, pain, and pressure.
2. Touch receptors send messages to the brain for processing.
G. Senses and Homeostasis
1. The five senses collect information about the environment. The brain responds to this
information and activates the body to maintain homeostasis.
2. Responding to the information received from the nervous system, the brain activates
the body to maintain homeostasis.
Lesson 3: The Endocrine System
endocrine system consists of organs and tissues that release chemical messages into the bloodstream
hormone chemical produced by an endocrine gland in one part of an organism and carried in the
bloodstream to another part
negative feedback control system where the effect of a hormone inhibits further release of the
hormone
positive feedback control system in which the effect of a hormone causes more of the hormone to be
released
A. Functions of the Endocrine System
1. The endocrine system consists of groups of organs and tissues that release chemical messages
into the bloodstream.
2. Endocrine tissues that secrete chemical messages are glands.
3. A(n) hormone is a chemical message produced by an endocrine gland. The
bloodstream carries these messages to other parts of the organism.
4. The messages sent by the endocrine system are transmitted less rapidly than messages
sent by the nervous system.
B. Endocrine Glands and Their Hormones
1. Hormones affect the functions of organs and tissues. A hormone message is produced
for a specific target cell.
2. After a hormone finds the target cell, it binds to a receptor protein in the cell and delivers its
chemical message. The target cell responds with the appropriate action.
3. Hormones secreted by the pituitary gland regulate body functions, control other endocrine
glands, and cause growth.
4. The thyroid gland controls how the body uses energy.
5. The two adrenal glands release hormones that enable the body to respond to stress and react
quickly.
6. The hypothalamus receives information from the nervous system and controls the activity of the
pituitary gland.
7. The four parathyroid glands regulate the release of calcium into the blood.
10.The two testes in males are responsible for releasing testosterone and producing sperm cells
for reproduction.
11.The two ovaries in females are responsible for releasing estrogen and producing egg cells for
reproduction.
C. The Endocrine System and Homeostasis
1. Glands help maintain homeostasis by releasing hormones, which change the function of
tissues and organs.
2. Negative feedback is a control system where the effect of a hormone inhibits further
release of the hormone. The endocrine system uses negative feedback and controls the
amount of hormone that a(n) gland releases.
3. Positive feedback is a control system in which the effect of a hormone causes more of
the hormone to be released.
4.Whereas negative feedback helps maintain homeostasis, positive feedback does
not.
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8. The thymus gland signals the immune system to produce cells to fight infections.
9. The pancreas secretes insulin and glucagon, which regulate the level of sugars in the blood.