1. Peripheral Nervous System
The Nervous System
Peripheral Nervous System

2. Human Nervous System Central Nervous System Brain + Spinal Cord
Peripheral Nervous System
Nerves (extensions from the CNS)
Provides Basis For Conscious Experience

3. Peripheral Nervous System
Afferent
Efferent
Skeletal - controls voluntary
movements of skeletal muscles
Autonomic - self-regulating, controls glands
& muscles of internal organs (e.g., heart)
Sympathetic
(arousing)
Parasympathetic
(calming)

4. Central Nervous System (billions of neurons & trillions of connections)
Spinal Cord
Conduit between peripheral nervous system
and the brain
Organize certain behaviors without the brain
Conduit Function
- Ascending tract carries sensory info to brain
- Descending tract carries info from brain to muscles
Organization Function
- Governs reflexive actions of muscles

5. Organization of the Nervous System
Central
Nervous System
Peripheral
Nervous System
Brain
Spinal Cord
Somatic
Autonomic

6. Skeletal/Somatic Nervous System
Nerves that connect to voluntary
skeletal muscles and to sensory receptors
Afferent Nerve Fibers
Axons that carry info away from the
periphery to the CNS
Efferent Nerve Fibers
Axons that carry info from
the CNS outward to the periphery

7. Autonomic Nervous System
Nerves that connect to the heart,
blood vessels, smooth muscles and glands
Sympathetic Division
Mobilizes the body’s resources
for emergencies (e.g., stim adrenal gland)
Fight or
Flight
Response
Cannon (1932)
Parasympathetic Division
Generally conserves bodily resources
(e.g., slows heart rate)

9. The Nervous System Peripheral Nervous System (PNS)
Made up of axons and dendrites.
It send messages to and from the CNS.
Central Nervous System (CNS) – brain and spinal cord directs mental and basic life processes.
Autonomic Nervous System (ANS)
Involuntary serves our basic life functions.
Somatic Nervous System (SNS) (Voluntary) sends sensory info to the CNS and motor messages to the muscles.
Sympathetic Nervous System
Readies the body for a threat
Parasympathetic Nervous System
Calms the body down and maintains energy

10. What is a neuron?
Neurons are the individual cells that transfer information throughout the body. One trillion in our bodies.
The Dendrites receive the input from other neurons and sensory receptors.
Cell Body (Soma) receives the information and sends it down the axon.
The Myelin Sheath covers the axon and helps speed up the message.
Glial cells provide structural and nutritional support to the neuron.

11. Different Types of Neurons
Sensory Neurons send info. from the body tissues to the brain.
Motor Neurons take info from the brain and send it to the tissues.
Inter-neurons are our internal highway.

12. Neural Communication Sensory Neurons (few million)
Interneurons (100 billion)
Motor Neurons (few million)

13. Neural Transmission + + + - - - + + +
Action Potential – neural impulses or messages
Ions – chemicals inside and outside the tube.
Resting (polarized) – fluid outside has more + charged ions.
Action potential creates depolarization of the membrane. - charge inside becomes +
Refractory Periods occur after each action potential

14. Nerve Impulses more (+) less (+) Intracellular Extracellular
Protein Molecules (A-) Sodium Ions (Na+)
Potassium Ions (K+) Chloride Ions (Cl-)
- Electrical signal is “Wet”.
- Signal travels via the flow of charged molecules, called “Ions”
- Nerve impulse is caused by a change in the nerve fiber’s PERMEABILITY to Na+ and K+.
- Permeability - the ease with which ions can pass through fiber membrane.
- At Resting Potential, the axon has a LOW PERMEABILITY to Na+.

15. Nerve Impulses Action Potential ...a brief electrical charge
1. Depolarization - Na+ channel open, Na+ rushes in
...a brief electrical
charge
traveling down
the axon,
like a line of
dominos
Depolarization (Steps 1 & 2) take 1/2000th second.
Repolarization (Steps 3 & 4) take an additional 1/2000th second.
(1 msec)
Each De/Re is called an ACTION POTENTIAL.
Each AP takes occurs at successive points along the axon (e.g., dominos).
“Traveling Nerve Impulse” is created by the flow of ions across the membrane.

16. Properties of Nerve Impulses
Once an AP is initiated, it travels down the length of the axon without stopping or changing size.
All or None Response
Stimulus Intensity:
SIZE of nerve firing
RATE of nerve impulse

17. Some Additional Properties
Speed of AP determined by:
Axon Diameter (­ diameter = ¯ resistance)
Myelin Sheath (­ myelin = ­ speed)
Approx 200 mph!
Spontaneous Activity plays a role in perception.
Each neuron is completely separate from other neurons - no physical connections.

18. Synapse is the space between Dendrite and next neuron.
The Synapse
Now I can afford
that hair piece!
Santiago
Ramón y
Cajal
Synapse is the space between Dendrite and next neuron.
Chemical process bridges gap between neurons

19. Neural Transmission Synapse The Synapse – the gap between the neurons
Terminal buttons & synaptic gap
Terminal buttons release neurotransmitters that attach to the membrane of adjacent neuron
Neurotransmitters can be excitatory or inhibitory.
Terminal Button
Presynaptic neuron – sends message
Postsynaptic neuron – receives message
Synapse

21. The Synapse
1. Nerve Impulse reaches Synaptic Vesicles in Terminal Button
2. Synaptic Vesicles release Neurotransmitters
- Neurotransmitters are picked up by next cell body and cause (maybe) a new AP to occur.
Excitatory neurotransmitters raise resting potential above -70mV.
(closer to threshold - more likely to fire)
Inhibitory neurotransmitters lower resting potential below -70mV.
(further from threshold - less likely to fire)
3. Neurotransmitters are Excitatory or Inhibitory

22. Effects of Neurotransmitters
Approx
15,000
Synapses
per
Neuron
- Brain neurons receive inputs from approx. 1 thousand other neurons.
If sum of Inhibitory & Excitatory transmitters is greater than threshold è IMPULSE!

23. Neurotransmitters & Behavior
75 substances are clearly neurotransmitters
Other chemicals may serve similar function
Specific neurotransmitters
work at specific kinds
of synapses
Agonists – excite or mimic neuro.
Antagonist – inhibit by blocking neuro.
Lock & Key

24. Acetycholine (ACh) ACh Motor Neurons Curare and the Black Widow
Voluntary Muscles
ACh
ACh contributes to:
Attention
Arousal
&
Memory Processes
Curare
and the
Black Widow

25. Endorphins (aka Endogenous Morphines) Endorphins Neuromodulators
Entire family of internally produced chemicals
that resemble opiates in structure and effects
Cross Blood-Brain Barrier
and bind to specialized
receptors in the brain
Neuromodulators
Chemicals that modulate activity of specific NTs
(e.g., Decrease NT that delivers pain signals)

26. Endocrine System
Exocrine (outside body/glands) – salivary, tear, sweat
Endocrine (ducts) – release of hormones in the blood
Hormones move more slowly than neurotransmitters, but last longer.
Effect growth, reproduction, metabolism, mood
Increase heart rate, blood pressure
Adrenal Gland
Release hormone (epinephrine)
Increased energy

27. Endocrine System Hypothalamus – control center
Anterior pituitary – growth hormone
Posterior pituitary – raises blood pressure
Thyroid (thyroxin) – increases metabolic rate, growth
Parathyroid – increases blood calcium, decreases potassium
Pancreas (insulin, glucagon) – regulates level of sugar
Ovary (estrogen) – promotes ovulation and sex characteristics
Testes (androgen)– promote sperm production and male sex characteristics