1. Sensory input: signals conducted
from sensory cells in body (heat,
touch, hearing, balance, vision, smell,
2. Integration: information
interpreted and processed (in brain
and spinal cord).
3. Motor output: signals carried to
muscles and glands.
Central nervous system – processes
information; brain and spinal cord; covered by
protective meninges layers and bathed in
Spinal cord incased in vertebral column;
simple stimuli and responses (reflexes); carries
info to brain.
Human brain divided into forebrain, midbrain,
Forebrain: cerebrum right and left hemispheres
(center of intelligence) connected by corpus
callosum; thalamus (relay station);
hypothalamus (regulates heart rate, bp, temp,
and pituitary hormones).
Hindbrain: medulla (controls heart and
breathing); cerebellum (balance and
coordination); pons (connects cerebellum to
Nervous system cells
1. Neurons – nerve cells made up of
dendrites (receive signals), cell body
(contains organelles), and axons (carries
signals away from cell body).
a. Sensory neurons gather sensory info.
b. Motor neurons carry out action signals.
c. Interneurons integrate input and
Synapses “connect” neurons by electrical
or chemical means (neurotransmitters).
Nervous system cells cont.
2. Supporting cells -- help neurons
function; 10-50 times more than
a. Glial cells found in CNS; form
blood-brain barrier and myelin
b. Schwann cells found in PNS; form
Nerve impulses are electrical signals.
Depends on flow of electrons across the
neuron’s cell membrane.
Neuron at rest has higher numbers of Na+
outside, higher number of K+ inside, and high
numbers of Cl- outside.
Membrane potential is about –70 mV.
Sodium-potassium pump keeps ions in these
concentrations so neuron can be ready to fire.
Nerve impulse cont.
Electrical stimulus at the dendrites causes a shift
in the ion balance as Na+ enters the cell
When membrane potential rises +15-20 mV, the
action potential is triggered.
Na+ continues into the cell and K+ exits the cell
as protein channels open (more depolarization);
total +100 mV change.
Action potential moves like a wave down the
axon to the end of the cell.
Membrane proteins will then reset the Na+/K+
Nerve impulse http://highered.mcgraw-