Nerves: Bundles of axons
Estimated 100 billion neurons in the human brain
How do they work together to keep info flowing effectively? ORGANIZATION
PERIPHERAL NS (includes somatic and autonomic)
Nerves that connect to voluntary skeletal muscles & sensory receptors. Carry info from
skin, muscles, joints to CNS & vice versa.
Nerves that connect to heart, blood vessels, glands, smooth muscles.
Automatic, involuntary actions. Ex: Digestion, heart rate, emotional
Central NS (includes Spinal cord and brain)
Connects the brain to the rest of the body.
Carries info from brain to peripheral nerves.
Plays a critical role in body movements. (ex: paralysis resulting from spinal
Carries info TO the CNS from periphery of body (ex: hand to spine)
Carries info FROM the CNS to periphery of body (ex: brain to hand)
Get body ready for action/exertion (mobilizes resources). Activates fightor-flight response.
Conserves bodily resources to save energy. (saves and stores resources)
NERVOUS SYSTEM (Handout 2)
(Processes info) Living tissue composed of cells. Glia & Neurons are the 2
main categories of cells making up the nervous system.
GLIA: (Glue) Cells in the nervous system that provide support for neurons.
Nourish neurons. Myelin sheath is made of certain types of Glia cells.
NEURONS: Cells in the nervous system that receive, integrate, & transmit
Soma: Cell body. Contains cell nucleus and chemical material.
Dendrites: RECEIVE info. Bring info to the soma.
Axon: Takes info AWAY from cell body. Transmits signals away from soma to
other neurons or to muscles or glands
Myelin Sheath: Insulating material that encases some axons. Speeds up
transmission of signals. (Note: Multiple Sclerosis (loss of muscle control) is
due to the degeneration of myelin sheaths)
Terminal button: Small knobs that secrete chemicals neurotransmitters.
Neurotransmitters: Chemicals that may activate neighboring neurons.
Synapse: Where info is chemically transmitted from 1 neuron to another.
Synaptic Cleft: Area between 1 neuron’s terminal button & the cell
membrane of another neuron.
NEURAL TRANSMISSION involves electrical and chemical messages.
NEURAL IMPULSE is the electrical message.
Each neuron has an electric charge created by ions in the neuron.
Fluid inside and outside the neuron has positively and negatively
A neuron’s resting potential is a stable negative charge when the
neuron is inactive (no messages are being sent).
When the neuron is stimulated (message is coming in) its cell
membrane chambers open briefly allowing in a rush of positive ions.
The neurons charge becomes less negative to positive, creating an
action potential (brief shift in electrical charge traveling along the
The neuron’s cell membrane channels close up and cannot fire again
for approx. 1 to 2 milliseconds. This “down” time is called the
absolute refractory period.
Ions: Electrically charged molecules and atoms.
All-or-None Law: Neuron either fires or doesn’t.
Purchase answer to see full