Human Body Systems
•	Organization of the Body (Review)
•	Cells
•	Basic unit of structure and function
•	Tissues
•	Group of cells that perform a single function             (e.g. epithelial, connective, nervous, muscle)
•	Organs
•	Different types of tissues that work together to perform a closely related function (e.g. eye, liver, lungs)
•	Organ Systems
•	Group of organs that perform closely related functions (e.g. circulatory, respiratory, digestive)

•	Homeostasis 

•	Definition: the process by which organisms keep internal conditions relatively constant despite changes in their external environments
•	Requires the integration of all organ systems at the same time
•	Nervous system in conjunction with the endocrine system (hormones) is responsible for this integration

•	Positive feedback – your body’s response results in an increase in the effect of the stimulus, (e.g. the flight-fight response)

Nervous System
•	Recognizes and coordinates the body’s response to changes in its internal and external environments.
•	General Functions of the Nervous System
•	Sensory input – vision, hearing, balance, smell, taste, and touch
•	Motor output – muscle contraction and movement
•	Memory and integration of information

•	Division of Labor 
•	Central Nervous System (CNS)
•	Control center of the body that relays messages, and processes and analyzes information
•	Brain
•	Cerebrum – largest region; right and left hemispheres that are connected by corpus callosum; voluntary activities and higher brain functions
•	Cerebellum – located at the lower back part of brain; coordination and balance
•	Brain stem – connects the brain and spinal chord; two regions: pons and medulla oblongata, control breathing, heart rate and swallowing
•	Thalamus and hypothalamus -  between brain stem and cerebrum
Thalamus: relay station for sensory info
Hypothalamus: most important homeostatic site; hormones, body’s thermostat, fight or flight, thirst, hunger, reproduction

•	Spinal Cord
•	Two main functions: 
•	Processing of simple responses to certain stimuli (reflexes)
•	 Carries info to and from brain to body

•	Peripheral Nervous System (PNS)
•	Receives information from the environment and relays to and from CNS and sensory, motor and gland cells

•	Two divisions:
•	Sensory - Made of sensory neurons that bring info to the CNS
•	Motor  - Made of sensory neurons that convey info from the CNS; two subdivisions
•	Somatic (voluntary): respond to external stimuli
•	Autonomic (involuntary): respond to internal stimuli w/the parasympathetic and sympathetic divisions
•	Sympathetic ↑energy consumption
•	Parasympathetic ↓energy consumption
Autonomic Overview Movie

•	Neurons (Nerve Cells)
•	Specialized cells that carry electrical signals called impulses (Draw Fig. 35-5; pg. 897)
•	3 Types of Neurons:
•	Sensory – carry impulses from the sense organs to the spinal cord and brain
•	Motor – carry impulses from brain and spinal cord to muscles and glands
•	Interneurons – Connect sensory and motor neurons and carry impulses between them
•	Anatomy of a Neuron
•	Cell Body
•	Largest part of the neuron
•	Contains the nucleus and most of the cytoplasm
•	Metabolic activity takes place in the cell body
•	Dendrites
•	Carry impulses from the environment or other neurons to the cell body
•	Axon
•	Long fiber that carries impulses from the cell body
•	Ends in axon terminals that contain vesicles for neurotransmitters
•	Myelin Sheath
•	Insulates the axon
•	Gaps in the myelin sheath allow an impulse to jump from node to node, thus increasing its speed
•	The Nerve Impulse
•	The Resting Neuron
•	At rest, the outside of the cell has a net positive charge and the inside has a net negative charge. This charge difference is called the resting potential. 
(-70mVolts, about 5% of the voltage in AA battery)
•	The charge difference is created by active transport of ions across the cell membrane via the sodium-potassium pump.
•	Sodium ions (Na+) are pumped outside the cell and potassium (K+) ions are pumped into the cell. 
•	The Moving Impulse
•	An impulse begins when a neuron is stimulated by the axon of another neuron or by the environment.
•	Na+  pores open and the flood of Na+ ions makes the inside positive. This reversal of charges, from negative to positive is called a nerve impulse, or an action potential.
•	As the impulse passes, K+ pores open and K+ flows out which restores the resting potential (charge difference) 
•	Nerve Impulse Pathway Overview
•	Impulse is received by the dendrites from the environment or another neuron, then gets rapidly channeled through the cell body to the axon
•	Axon branches out into axon terminals, which contain tiny vesicles filled with neurotransmitters, which are chemicals used by a neuron to transmit an impulse to another cell.  (e.g. acetylcholine, serotonin, dopamine and adrenalin). 
•	Vesicles release neurotransmitters into the open space between neurons called the synapse.
•	The neurotransmitters diffuse across the synapse and attach themselves to receptors on dendrite of neighboring cell
•	Reflexes
•	Reflexes are automatic responses to stimuli
•	Controlled by 5-part reflex arc:
•	Sensory receptors on finger reacts to stimulus (heat)
•	Impulse is carried to the spinal cord by a sensory neuron
•	In the spinal cord, the impulse is transferred by an  interneuron to motor neuron
•	Motor neurons conducts the impulse to an effector (arm muscles)
•	Effector responds to the impulses by contracting (hand gets pulled away from the heat)
•	  The Senses
5 General Sensory Receptors: pain, thermo-, mechano-, chemo- and photoreceptors. Vision
•	Hearing and Balance
•	Smell and Taste
•	Touch
•	  Nervous System Disorders
•	Migraine Headaches  – caused by change in serotonin levels? (affected by caffeine, estrogen, certain foods)
•	Parkinson’s –caused by damage to dopamine transmitters; causes uncontrollable shaking, no cure
•	Tay-Sachs –lack enzyme to break down fatty deposits in the brain; neurological deterioration; death by age 4-5
•	Dementia  - damaged brain cells caused by injury or disease (Alzheimer’s);  memory loss and personality change.

•	Drugs and the Nervous System
•	Stimulants
•	Accelerate HR, BP, and breathing rate
•	Increases the release of neurotransmitters; leads to release of energy and feeling of well-being
•	When effect wears off, brain’s supply is depleted
•	Caffeine
•	Cocaine
•	Methamphetamines 
•	Depressants
•	Slow down HR,  lower BP and breathing rate, relax muscles and relieves anxiety
•	Alcohol
•	Marijuana
•	Sleeping Pills