AP Biology

35.2 – The Nervous System

Regents Biology

Objectives §  Describe the components of a neuron and their

functions. §  Describe how an action potential is generated and

propagated. §  Describe how an impulse is transmitted across

synapses.

Regents Biology

Why do animals need a nervous system?

§  Why need a nervous system? §  What characteristics do

animals need in a nervous system? -  fast -  accurate -  reset quickly

http://www.youtube.com/watch?v=bEwo6CG1B44

Regents Biology

Nervous System §  Central nervous system -  brain and spinal chord

§  Peripheral nervous system -  nerves from senses -  nerves to muscles

cerebrum

cerebellum

spinal cord cervical nerves

thoracic nerves

lumbar nerves

femoral nerve

sciatic nerve

tibial nerve

Regents Biology

Neurons

Axon terminals

Myelin sheath

Cell body

Nodes of Ranvier

Axon

Dendrites

Nucleus

Regents Biology

Types of Neurons sensory neuron (from senses)

interneuron (brain and spinal chord)

motor neuron (to muscle)

Regents Biology

Fun facts about neurons §  most specialized cell in

animals §  longest cell -  blue whale neuron

(10-30 meters) -  giraffe axon (5 meters) -  human neuron (1-2

meters)

Regents Biology

Myelin Sheath signal

direction §  Axon coated with insulation made

of myelin sheath §  speeds signal §  Signal gets strengthened from node

to node (330 mph vs. 11 mph)

myelin sheath

Regents Biology

Nerve Impulse §  Resting potential (-60 mV) -  (+) out, (-) in -  K+ diffuses out - Na-K pumps more K+ out than Na+ in

§  Action potential -  stimulus above threshold - Na gate opens, Na+ in à reverses

membrane voltage (depolarization) -  K gate opens, K+ out à restores

membrane voltage (repolarization) -  undershoots resting potential and

eventually comes to resting potential -  nerve impulse self-propagates -  all-of-nothing!

Nerve Impulse http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter8/animation__the_nerve_impulse.html

Regents Biology

Synapse §  Junction between neurons -  impulse arrives at exon terminal -  releases neurotransmitters into

synaptic cleft -  neurotransmitters bind to receptors on

membrane of next neuron… -  neurotransmitters reuptake/broken down

Synaptic Transmission http://bcs.whfreeman.com/hillis1e/

#667501__674237__