1. Introduction to the Nervous System Chapter 35
Of all the Nerve!
Introduction to the Nervous System
Chapter 35

2. Organs of the Nervous System
Brain
Spinal cord
Numerous nerves
Specialized sense organs such as eyes and ears
Microscopic sense organs such as those found in the skin

3. Divisions of Nervous System
Central Nervous System
Processing system
Brain and Spinal Cord
Peripheral Nervous System
Connects CNS to limbs and organs
Somatic - Voluntary and
Autonomic - Involuntary
Autonomic = automatic
CNS - Brain, spinal cord
PNS - Nerves that extend to the periphery of body
Autonomic nervous system - involuntary functions (breathing rates, respiratory rates, etc)
Somatic - voluntary functions (motor neurons)

4. Neurons What do they do? 3 parts:
carry the impulses that make things happen.
cell body, branching projections called dendrites and elongated axons.
Axons send signals, dendrites receive signals.

5. Axon is covered in ________________.
Myelin is formed by ____________ __________.
Nodes of Ranvier -
Myelin
Schwann cells
are indentations between adjacent Schwann cells that aid in quick transmission of signals
Compare nerve impulse speed of giant squid to human impulse speed

6. Conduction jumps from node to node, much faster than without myelin to insulate.

7. Nerve Bundle Organization
White matter - has myelin
Each axon in a nerve is surrounded by fibrous connective tissue called endoneurium.
Groups of these axons are called fascicles which are surrounded by perineurium
Epineurium covers whole nerve (fibrous sheath)

8. Reflex Arcs - no brain involvement

9. Nerve Impulses are Electrical
Self propagating wave of electrical disturbance that
travels along the surface of a neuron’s plasma membrane.
Stimulus occurs
Charges across the membrane change from - to +
This change “travels” down the membrane of axon
Synapse occurs at terminal end of presynaptic neuron
Post synaptic neuron receives impulse and carries
on the “message” or signal

10. The connection between the axon of one neuron and the dendrite of another is a SYNAPSE
Space between neurons is called a synaptic cleft.
Because of this gap, the electrical impulse (action potential) cannot be transmitted directly and must be converted into a chemical signal that is then converted back into an electrical signal in the postsynaptic cell. Neurotransmitters are held in vesicles until the impulse causes them to be secreted into the cleft and then recpetors on the postsynaptic cell receive the.
The chemicals that convert the signal across the cleft are called neurotrasnmitters.

12. Action Potential Video

13. Neurotransmitters - There are at least 60 different neurotransmitters
Neurotransmitters - There are at least 60 different neurotransmitters. - One type can trigger many different responses, depending on the postsynaptic cells receptors - list of major ones and their actions: - 2