1. Human Body Systems

2. The Nervous System
Chapter 21

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

4. Neurons 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

6. Types of Neurons Sensory neurons Motor neurons Interneurons
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

7. The Central Nervous System (CNS)
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)
Where thinking occurs
Largest part of the brain
Cerebellum (tan part)
Coordinates movement, interprets stimuli
Brain Stem (Blue part)
Connects parts of brain, and connects brain to spinal cord
Controls involuntary actions

8. The Central Nervous System (CNS)
The spinal cord
Extension of brain stem
Carries impulses throughout body

9. The Peripheral Nervous System (PNS)
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)

10. The circulatory System

12. The Heart Made up of cardiac tissue Contains 4 compartments Steps
Right/Left Ventricle
Right/Left Atrium
Steps
Blood enters the heart through the Vena Cava to the right atrium
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

13. Blood Vessels Arteries carry blood away from the heart
Veins return oxygen-poor blood to the heart
Capillaries connect arteries and veins

14. Blood Functions Carries oxygen to your cells
Carries waste products to kidneys for disposal
Transports nutrients
Fight infections

15. Parts of Blood 55% of blood is plasma 45% is red blood cells
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

16. The Reproductive System and development

17. Maturity Warning
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!

18. The Male Reproductive System
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

19. The Female Reproductive System
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

20. The Menstrual Cycle 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 years old

21. Human Life Stages 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 3rd month, the fetus is about 9 cm long
By the 9th 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

22. Human Life Stages Delivery Neonatal Stage Infancy
The contractions and pushes by the mother force the baby out
The placenta is also forced out shortly after
Sometimes, a cesarean section is required
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
Baby becomes more aware of surroundings
At about 8 months, the baby begins to crawl. They can sometimes walk at 10 months

23. Human Life Stages Childhood Adolescence Adulthood
18 months-12 or 13 years old
Child grows, learns to use the bathroom, learns to speak, read, etc.
Reaches puberty around years old
Adolescence
12 or years old
Puberty causes changes to the body
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

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

25. Most common causes of death
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

26. Other Body Systems

27. Lymphatic System
Collects and returns fluids from tissues to the blood system

28. The Endocrine 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.