1. The Human Body
Ch. 35 Nervous System

2. Organization of the Body
The levels of organization in a multicellular organism include cells, tissues, organs, & organ systems.
There are 11 distinct human body systems. (see pages in text)

3. Cells
-A cell is the basic unit of structure & function in living things
-Specialized cells - cells uniquely suited to perform a particular function

4. Tissues
There are 4 basic types of tissue in the human body: epithelial, connective, nervous, & muscle
Epithelial tissue - includes glands & tissues that cover interior & exterior body surfaces

5. Tissues con’t
Connective tissue - provides support for the body & connects its parts
Nervous tissue - transmits nerve impulses throughout the body
Muscle tissue - along with bones, enables the body to move

6. Maintaining Homeostasis
Homeostasis -the process of keeping internal conditions relatively constant despite changes in the external environment

7. Maintaining Homeostasis
Negative Feedback - when a stimulus produces a response that opposes the original stimulus
Ex.) Thermostat regulating room temp, Pancreas releasing insulin

8. Negative Feedback

9. The Nervous System
The nervous system controls & coordinates functions throughout the body & responds to internal & external stimuli

10. Neurons
Messages carried by the nervous system are electrical signals called impulses
Neurons - cells that transmit impulses
Cell Body - largest part of a neuron, contains the nucleus & most of the cytoplasm, where the metabolic activity of the cell takes place

11. Neurons
Dendrites - short, branched extensions, that carry impulses from the environ. or from other neurons toward the cell body
Axon - long fiber that carries impulses away from cell body
Myelin sheath - insulating membrane that surrounds the axon

12. Neurons

13. The Synapse
Synapse - the location where a neuron can transfer an impulse to another cell
Neurotransmitters - chemicals used by a neuron to transmit an impulse across a synapse to another cell

14. Divisions of the Nervous System
The peripheral nervous system (PNS) receives info. from the environ. & relays commands from the CNS to organs & glands
The central nervous system (CNS) relays messages, processes information, & analyzes information
The CNS is the control center of the body, includes the brain & spinal cord

15. The Central Nervous System
Meninges - layers of connective tissue that are wrapped around the brain & spinal cord
Cerebrospinal fluid - bathes the brain & spinal cord & acts as a shock absorber that protects the CNS

16. Brain
The brain consists of the cerebrum, cerebellum, & brain stem

17. Brain Cerebrum - the largest region of the human brain
It is responsible for the voluntary, or conscious, activities of the body

18. Brain Cerebellum - the 2nd largest region of the brain
It is located at the back of the skull
The cerebellum coordinates & balances the actions of the muscles so that the body can move gracefully & efficiently

19. Brain Brain stem - connects the brain & spinal cord
It is located below the cerebellum, it includes 2 regions: the pons & the medulla oblongata
Each of these regions regulates the flow of info. between the brain & the rest of the body
Controls important functions like: blood pressure, heart rate, breathing, & swallowing

20. Brain
The thalamus & hypothalamus are found between the brain stem & the cerebrum
Thalamus - receives messages from all of the sensory receptors throughout the body & then relays the info. to the proper region of the cerebrum for further processing

21. Brain
Hypothalamus - the control center for recognition & analysis of hunger, thirst, fatigue, anger, & body temperature
It also controls the coordination of the nervous & endocrine systems

22. The Spinal Cord
Certain kinds of info., including some kinds of reflexes, are processed directly in the spinal cord
Reflex - a quick, automatic response to a stimulus; it allows your body to respond to danger immediately, without spending time to think about a response
Ex.) sneezing & blinking

23. The Peripheral Nervous System
The sensory division of the PNS transmits impulses from sense organs to the CNS
The motor division transmits impulses from the CNS to the muscles or glands
The somatic nervous system regulates activities that are under conscious control, such as movement of the skeletal muscles

24. The Peripheral Nervous System
The autonomic nervous system regulates activities that are automatic
Ex.) Heart rate increases as you run
Overall, the PNS transmits impulses from sense organs to the CNS & back to muscles or glands

25. The Senses
Sensory receptors - neurons that react to a specific stimulus such as light or sound by sending impulses to other neurons, & eventually to the CNS
There are 5 general categories of sensory receptors: pain receptors, thermoreceptors, mechanoreceptors, chemoreceptors, & photoreceptors

26. The Senses
Pain receptors are found throughout the entire body, except the brain, & respond to chemicals released by damaged cells
Pain usually indicates danger, injury, & disease

27. The Senses
Thermoreceptors are found in the skin, body core, & hypothalamus
They also detect variations in temperature

28. The Senses
Mechanoreceptors are found in the skin, skeletal muscles, & inner ears
They are sensitive to touch, pressure, stretching of muscles, sound, & motion

29. The Senses
Chemoreceptors are found in the nose & taste buds, & are sensitive to chemicals in the external environ.
Photoreceptors are found in the eyes, & are sensitive to light

30. Vision Eyes are sense organs used to detect light
The iris is the colored part of the eye
The pupil is in the middle of the iris
Muscles in the iris regulate the amount of light that enters the eye

31. Vision
Lens - located just behind the iris, muscles attach to the lens to change its shape, to help you adjust your eyes’ focus to see near or distant objects
Retina - where light is focused onto from the lens; here, light energy is converted into nerve impulses that are carried to the CNS

32. Vision

33. Hearing & Balance
Sound is nothing more than vibrations in the air around us
The ears are the sensory organs that can distinguish both the pitch & loudness of those vibrations

34. Hearing & Balance
Ears contain structures that help your CNS maintain your balance, or equilibrium; they monitor your head in relation to gravity

35. Smell & Taste Taste buds - sense organs that detect taste
Chemoreceptors found in the taste buds are sensitive to chemicals in food

36. Touch & Related Senses The sense of touch is not found in just 1 place
All of the regions of the skin are sensitive to touch
Skin is the largest sense organ of the body
It contains sensory receptors that respond to temp., touch, & pain

37. Drugs & the Nervous System
Drug - any substance, other than food, that changes the structure & function of the body

38. Drugs That Affect the Nervous System
Stimulants - drugs that increase the actions regulated by the nervous system
They increase heart rate, blood pressure, & breathing rate
Includes: amphetamines, cocaine, nicotine, & caffeine

39. Drugs That Affect the Nervous System
Depressants - drugs that decrease the rate of functions regulated by the brain
They slow down heart rate & breathing rate, lower blood pressure, relax muscles, & relieve tension
Includes: Barbiturates, & tranquilizers

40. Drugs That Affect the Nervous System
Cocaine causes the sudden release in the brain of a neurotransmitter called dopamine
Its normally released when a need such as hunger or thirst, is fulfilled
By fooling the brain, cocaine produces intense feelings of pleasure & satisfaction

41. Drugs That Affect the Nervous System
Opiates mimic natural chemicals in the brain known as endorphins, which normally help to overcome sensations of pain
The first doses produce feelings of pleasure & security

42. Drugs That Affect the Nervous System
Marijuana produces a temporary feeling of euphoria & disorientation
Smoking marijuana is more destructive to your lungs than smoking tobacco
Long-term use can result in memory loss; inability to concentrate; & in males, reduced levels of the hormone testosterone

43. Drugs That Affect the Nervous System
Alcohol is a depressant that slows down the rate at which the CNS functions
It slows down reflexes, disrupts coordination, & impairs judgment

44. Drugs That Affect the Nervous System
Fetal alcohol syndrome - a group of birth defects caused by the effects of alcohol on the fetus
Babies born with FAS can suffer from heart defects, malformed faces, delayed growth, & poor motor development

45. Drug Abuse
Drug abuse - the intentional misuse of any drug for nonmedical purposes
Addiction - an uncontrollable dependence on a drug