Chapter 21

• Responding to stimuli
• Stimuli is anything that elicits a response
• Homeostasis
• Ensuring that internal conditions stay constant

• Basic functioning unit of the nervous system
• Neurons are cells that receive and carry messages
• Composed of Dendrites and Axons
• Dendrites receive messages and send them to the cell body
• Axons carry messages away from the cell body
• The messages carried by the neurons are called impulses

• Sensory neurons
• Receive information from the external environment and send impulses to the brain
• Motor neurons
• Conduct impulses from the brain to your muscles and glands
• Interneurons
• Relay impulses from the brain to other neurons
• Synapses are areas between neurons
• When an impulse reaches the axon endings, they release chemicals called receptors that cross the synapse and reach the next dendrite

• Made up of the brain and spinal cord
• The brain
• Controls your body
• Made up of 100 billion neurons (10% of the total in your body)
• 3 main parts
• Cerebrum (Pink part)
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Where thinking occurs
Largest part of the brain
• Cerebellum (tan part)
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• Coordinates movement, interprets stimuli
Brain Stem (Blue part)
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Connects parts of brain, and connects brain to spinal cord
Controls involuntary actions

• The spinal cord
• Extension of brain stem
• Carries impulses throughout body

• Made up of all of the nerves outside of the CNS
• Connects CNS to all of the other parts of the body
• Contains 2 systems
• Somatic System
• Controls voluntary actions
• Autonomic System
• Controls involuntary actions (automatic)

• Made up of cardiac tissue
• Contains 4 compartments
• Right/Left Ventricle
• Right/Left Atrium
• Steps
• Blood enters the heart through the Vena Cava to the right atrium
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The right atrium contracts, sending blood into the right ventricle
The right ventricle contracts, sending blood into lungs
• There, blood picks up oxygen
Blood returns to the left atrium
The left atrium contracts, sending blood to the left ventricle
Left ventricle contracts, sending blood out of the heart through the aorta
• It then travels through the body, delivering blood, until it returns through the vena cava

• Arteries carry blood away from the heart
• Veins return oxygen-poor blood to the heart
• Capillaries connect arteries and veins

• Carries oxygen to your cells
• Carries waste products to kidneys for disposal
• Transports nutrients
• Fight infections

• 55% of blood is plasma
• Liquid portion of blood
• Carries nutrients and waste
• 45% is red blood cells
• Contain hemoglobin
• Carries oxygen and carbon dioxide
• Formed in long bones (such as the femur)
• Less than 1% is white blood cells
• Fight pathogens
• Also in blood is platelets which help clot blood

• We are going to talk about the male and female reproductive systems
• I expect you to act as if you are in middle school, not elementary.
• I will remove you from the class if needed.’
• Let me teach, let others learn
• You have been warned!

• Made up of external organs
• The penis
• The scrotum
• Contains the testicles, which produce testosterone and sperm
• Sperm has a head and a tail
• The head contains the DNA, the tail helps them move
• Semen is the combination of sperm and fluids

• Internal structures
• Ovaries store eggs
• Females are born with all of the eggs that they will ever have
• Eggs are released from ovaries during ovulation
• They travel through an oviduct to the uterus
• If the egg is fertilized, the egg will implant in the uterus
• If a fetus develops, the child is born through the vagina, the muscular tube that reaches the outside of the body

• Usually 28 days in length
• Phase 1: Menstrual flow begins
• Blood, tissues form the uterus, and the egg are expelled from the body
• Called the period
• Phase 2: Lining of the uterus is replenished and thickens
• An egg is released and travels to the uterus
• Phase 3: Uterus readies for conception
• If it happens, the uterus is ready to nourish the embryo
• If it doesn’t the cycle begins again
• Most females get their first period around 13.
• Continues until child-bearing years are over, around 45-55 years old

• Zygote formation:
• Sperm and egg fuse, and fertilized egg begins to undergo mitosis, forming an embryo
• The amniotic sac forms, along with the umbilical cord and placenta that will deliver nutrients to the fetus until birth
• After 2 months, the embryo becomes a fetus.
• Around the 3 rd month, the fetus is about 9 cm long
• By the 9 th month, the fetus is ready to be born, including being head-down
• Childbirth
• The first sign is contractions, which are the body preparing to push the newborn out
• Then, the amniotic sac breaks, releasing the contents (called “Water breaking”
• The uterus widens, contractions become more powerful

• Delivery
• The contractions and pushes by the mother force the baby out
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The placenta is also forced out shortly after
Sometimes, a cesarean section is required
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• An incision is made through the abdomen, then through the uterus, and the baby is delivered
The umbilical cord is cut
• Neonatal Stage
• 0-4 weeks
• Newborn’s body begins to function, and gets used to the new environment
• Infancy
• 4weeks-18 months
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Baby becomes more aware of surroundings
At about 8 months, the baby begins to crawl. They can sometimes walk at 10 months

• Childhood
• 18 months-12 or 13 years old
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Child grows, learns to use the bathroom, learns to speak, read, etc.
Reaches puberty around 11-14 years old
• Adolescence
• 12 or 13-18 years old
• Puberty causes changes to the body
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Males: Voice deepens, hair growth,
Females: breasts develop, body hair appears
• Adulthood
• 18-45 to 60
• Growth stops, and body systems stop functioning as efficiently

• Late Adulthood
• 60+
• Decline in body functions
• Bones become more fragile
• Hearing and eyesight deteriorate
• Death
• Currently, the human life span is about 79 years

• Heart disease: 611,105
• Cancer: 584,881
• Chronic lower respiratory diseases: 149,205
• Accidents (unintentional injuries): 130,557
• Stroke (cerebrovascular diseases): 128,978
• Alzheimer's disease: 84,767
• Diabetes: 75,578
• Influenza and Pneumonia: 56,979

• Collects and returns fluids from tissues to the blood system

• Produces and regulates hormones
• Regulates metabolism, growth and development, bodily functions, reproduction, sleep, mood, etc.
• Negative-Feedback System
• When things in the body change, your body must compensate for this.
• Example: When you are cold, your body makes you shiver (move around) to keep warm. If you get too warm, you will begin to sweat. You do these until you are comfortable.