1. The Nervous System Chapter 6

2. The Nervous system has three major functions:
Sensory
monitors internal & external environment through presence of receptors
Integration
Interprets sensory information
Motor
response to information processed through stimulation of effectors

3. Organization of the Nervous System
Two Anatomical Divisions
Central nervous system (CNS)
Brain
Spinal cord
Peripheral nervous system (PNS)
All the neural tissue outside CNS
Afferent division (sensory input)
Efferent division (motor output)

6. Afferent vs Efferent Afferent Nerves Efferent Nerves Sensory Nerves
Receive Information
Transmit sensory information gathered from the skin, muscles, and joints to the CNS
Motor Nerves
Send information on
Carries information from the CNS out to the muscles and glands

7. Sensory nerve cells: Afferent pathway CNS (brain and spinal cord): Integration centers Motor nerve cells: Efferent pathway

8. Organization of the Nervous System
Brain & spinal cord

9. Cells of the Nervous System
Two types of neural cells in the nervous system:
Neurons
Process, transfer, and store information
Neuroglia – (also called “glial cells”)
Support and protect neurons

10. Structure of a Neuron

12. Most axons of the nervous system are surrounded by myelin
The presence of myelin speeds up the transmission of signals along the axon
Myelin will get laid down in segments along the axon, leaving unmyelinated gaps known as “nodes of Ranvier”

13. ELECTRICITY!!!
Conductivity: the property of neurons that give them the ability to transmit nerve impulses
Electrical impulses (action potentials) are “all-or-none” responses

14. Neurotransmitters are chemical messengers.
Axon terminals do not actually touch the other neuron or muscle. The gap is called the synapse.
Neurotransmitters are chemical messengers.

15. The Structure of a Typical Synapse

16. Classification of Neurons
Structural classification based on number of processes coming off of the cell body
We will talk about three neuron structures:
Multipolar
Bipolar
Unipolar

17. Multipolar neuron
multiple dendrites
single axon
most common type
ALL motor neurons are multipolar

18. Bipolar neuron
two processes coming off cell body
one dendrite
one axon
only found in eyes, ears & nose
Process sensory information

19. Unipolar neuron
single process coming off cell body
dendrites at one end
axon makes up the rest of the process
some sensory neurons in PNS are unipolar

20. Anatomical structure of Nerves
Fig. 14.6

21. Efferent Divisions Somatic Nervous System Autonomic Nervous System
Voluntary
Stimulates skeletal muscles
Stimulates them to contract
Involuntary
Controls cardiac muscle of the heart and smooth muscle of internal organs
2 Categories
Sympathetic
Fight or Flight response
Releases adrenaline
Parasympathetic
Rest and digest response
Day-in-day-out functions

22. Reflexes (Simple, rapid, involuntary, programmed responses to stimuli)
Somatic Reflexes
Autonomic Reflexes
Stimulation of skeletal muscles
Ex: Withdrawing hand from something hot before you even realize it is hot
Fast because doesn’t travel to brain and back (sensory neuron  spinal cord  motor neuron)
Send involuntary stimuli to cardiac muscle of heart and smooth muscle of internal organs
Ex: Digestion, elimination, sweating, blood pressure

24. Nervous System Overview

25. Nerve Impulses

26. Synapses In Detail