1. Functional Organization of Nervous Tissue Chapter 11

2. The Nervous System Components: Responsible for… Subdivisions:
Brain, spinal cord, nerves, sensory receptors
Responsible for…
Sensory perceptions, mental activities, stimulating muscle movements, secretions of many glands
Subdivisions:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)

3. Central Nervous System
Consists of brain and spinal cord
The structural & functional center of the entire nervous system which integrates incoming pieces of information & initiates an outgoing response

4. Peripheral Nervous System
All other nerves
All pathways going toward and away from the CNS

5. Nervous System Organization

6. Concept Check
What are the two divisions of the nervous system? What are their parts?
CNS: Brain & Spinal Cord
PNS: nerves
What are the functions of the CNS?
Integrates incoming information & initiates an outgoing response
What is the function of the PNS?
Conducts action potentials to and away from the CNS
What are some functions of the Nervous system?
Sensory perceptions, mental activities, stimulating muscle movement, secretions of many glands

7. Cells of Nervous System
Neurons or nerve cells
Receive stimuli and transmit action potentials
Organization
Cell body or soma
Dendrites: input
Axons: output
Neuroglia cells
Support and protect neurons

8. Types of Neurons Functional Classification
Sensory or afferent: action potentials toward CNS (receives stimuli; could be a special sense organ)
Motor or efferent: action potentials away from CNS (attached to a muscle or gland)
Interneurons or association neurons: within CNS from one neuron to another

9. Myelinated and Unmyelinated Axons
Myelin protects and insulates axons from one another
Not continuous
Nodes of Ranvier
Impulse “jumps” from node to node
Fast impulse
Unmyelinated axons
Slower impulse

10. Electrical Signals
Cells produce electrical signals called action potentials
Transfer of information from one part of body to another
Electrical properties result from ionic concentration differences across plasma membrane and permeability

11. Nerve Impulses
A wave of electrical fluctuation that travels along the plasma membrane; due to changes in chemical concentrations.
Impulse
Resting Potential
“Polarized”
Action Potential
“Depolarized”
Resting Potential
“Repolarized”

12. Resting Membrane Potential
Characteristics
Number of charged molecules and ions inside and outside cell nearly equal
Concentration of K+ higher inside than outside cell- negative proteins in also, Na+ higher outside than inside
At equilibrium there is very little movement of K+ or other ions across plasma membrane

13. Action Potentials
Series of permeability changes when a local potential causes depolarization of membrane
Phases
Depolarization
More positive
Repolarization
More negative
All-or-none principle
Neuron will fire or it won’t

14. The Synapse Junction between two cells
Electrical message transferred across the synapse by chemicals called neurotransmitters

15. Concept Check What are the main parts of a neuron?
Axon, dendrites, myelin sheath, synapse
What are the three types of neurons and what do they do?
Sensory (afferent)- action potential toward CNS , Motor (efferent)- action potential away from CNS, & Interneurons- within CNS from one neuron to another
How does an impulse travel along an axon? What speeds it up?
Jumps from node to node; myelin
How does a synapse work?
Neurotransmitters transfer message across synapse

16. Stimulus Any change in your environment.
Temp, sound, smell
You may or may not respond to a specific stimulus

17. Reflex
A predictable response to a stimulus which may or may not be conscious
A reflex consists of either muscle contraction or glandular secretion
Neurons involved in reflex
Afferent neuron- sensory
Interneuron
Efferent neuron- motor

18. Sensory Receptors
In order for a stimulus to be detected, it must be strong enough to elicit an impulse
It must be at the threshold level- the minimum stimulus to start an impulse
The all-or-none response means that either a neuron will fire or it won’t, there is no partial impulse
Sensation- the brain’s interpretation of what the stimulus is

19. Characteristics of Sensations
Projection- brain refers a sensation to the point of stimulation
Adaptation- loss of sensation even though the stimulus is still applied
Afterimage- persistence of a sensation even though the stimulus is removed
Referred pain- felt in the skin near or around the organ sending the impulse
Phantom pain- sensation of pain in a limb that has been amputated

20. Classification of Receptors
Mechanoreceptors- activated by mechanical stimuli or deformation of the receptor
Chemoreceptor- changing of the chemical concentrations around the body
Thermoreceptors- detect hot and cold
Nociceptors- any stimuli that can cause tissue damage; sensation of pain
Photoreceptors- respond to light

21. Somatic Senses pain, temperature and touch
These sensations can be felt throughout the body, yet they are distributed unevenly through the skin
Exteroceptors- sense receptors located on body surfaces
Proprioceptors- found in the muscles and joints
Visceroceptors- found in internal organs
Nociceptors- pain receptors; free nerve endings

22. Review Meissner’s corpuscles- touch Krause’s End Bulbs- touch
Ruffini’s corpuscles- continuous touch
Pacinian corpuscles- deep pressure

23. The Brain Parts/Functions Left vs Right Brain Activity??
Dissection notes…pre-lab??