1. Unit #7 Nervous System:
Neurons

2. Maintaining homeostasis
Two systems of communication
Nervous system
Rapid response
Uses action potentials
Endocrine system
Slower response
Uses hormones released into blood stream
Controlled by the NS

3. Did You Know?
Many types of mental illnesses are related to imbalances in chemicals that transmit messages between neurons

4. Organization of the nervous system
Central nervous system: Brain and spinal cord
Peripheral nervous system: all nervous tissue outside the CNS- nerves going to organs and muscles

5. Tortora
Fig 9.1 pg 254
Divisions of the PNS
I. Somatic (SNS): sensory neurons send information into to brain via somatic receptors
II Autonomic (ANS) sends messages from internal organs to brain. Sends messages to smooth and cardiac muscles & glands from the brain. Under involuntary control
III. Enteric (ENS) the “brain of the gut” controls digestion, peristalsis, secretions of GI tract organs. Involuntary control

6. Endocrine system
Master glands- hypothalamus and pituitary- located in brain
Communicate with other e. organs by hormones
Regulates growth, development, metabolism, and homeostasis in the body

7. Functions of the nervous system
I. Sensory function-Detect and transmit information to the brain
Sight
Hearing
Touch
Taste
Smell

8. Functions of Nervous System
II. Integrative
The NS processes sensory information
Analysis
Storage (memory)
Decisions
Responses

9. Functions of Nervous System
III. Motor
Once info. is integrated, a motor response is generated by activating effectors
(muscles and glands).
Stimulation causes muscles to contract and glands to secrete.

10. Neurons: cells of the nervous system
3 distinct areas
Cell body (soma)
Dendrites
Axons
Messages travel from the dendrites towards the axon

11. Neuron organelles Nucleus Typical cell organelles No mitotic spindle.
Will the cell divide? .

12. Dendrites surrounded by neuroglial cells.
Usually short and thick.
Usually highly branched.
Receives impulses.
Conducts impulses towards cell body.
Dendrites surrounded by neuroglial cells.

13. Axon surrounded by neuroglial cells
Tortora 256
Axons
Neurons have a single axon.
Usually long and very thin.
Can be branched (collaterals)
Axon terminals contain vesicles.
Vesicles contain neurotransmitters.
Axon surrounded by neuroglial cells

14. 3 types of neurons:
Multipolar
Bipolar
Unipolar

15. Multipolar: have several dendrites, 1 axon- brain, spinal cord neurons
Bipolar: 1 main dendrite, 1 axon- retina of eye, inner ear, olfactory area of brain
Unipolar: dendrites & axon are fused together, cell bodies off to the side (in ganglia)- sensory receptors (touch, pain, thermal)

16. Functional classification
Sensory, Motor, and Connecting Neurons
Sensory are referred to as afferent.
Motor are referred to as efferent.
Connecting are referred to as association

17. Organization of Nervous System
Somatic Vs Autonomic
Somatic is voluntary
Sensory nerves and motor nerves.
Autonomic is involuntary
Mostly motor nerves leading to smooth muscle, cardiac muscle, and glands.

18. Neurons found in the spinal cord.
Neurons and neuroglia
Two different types of cells
Neurons conduct impulses.
Neuroglial cells support and protect neurons.
Neurons found in the spinal cord.

19. Neuroglia cells Smaller than neurons. Outnumber neurons 5 to 50 times.
Function: support, protect neurons
make cerebrospinal fluid, create the myelin sheath
Glioma: brain tumor made of glial cells : malignant

21. Myelin sheath structure
Speeds impulse along axon.
Insulates axon .
Composed of neuroglial cells. (PNS)
Schwann cells produce myelin (lipoprotein) in PNS
Nodes of Ranvier are gaps in myelin sheath.
Myelin sheath structure

22. White and gray matter
White matter is myelinated: axon is surrounded by a myelin sheath
Gray matter is unmyelinated- axon (not wrapped)

23. Nerve Impulses Nerve impulse
An impulse is a change in the electrical charge (potential) on the membrane of the neuron.
Due to ions moving into and out of the neuron.

24. Nerve Impulses Ions move through very selective membrane channels.
Tortora
Pages
Ions move through very selective membrane channels.
Channels are transmembrane proteins.
Voltage gated channels pass pulse down the axon to the terminus

25. Nerve Impulses Membrane Potentials Resting potential - no impulse.
Tortora
Pages 261
Membrane Potentials
Resting potential - no impulse.
Positive outside
Negative inside.
Action potential.
Positive inside.
Negative outside.
Potentials are due to ions.
Na + K+
Large negative ions (proteins)

26. Creating An Impulse Along An Axon
Nerve Impulses
Tortora
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Resting potential
No impulse.
Positive outside neurolemma
Negative inside.
30x more K+ inside.
15x ore Na+ outside.
Large negative ioins trapped inside.
Sodium - Potassium pump creates these conditions.
Membrane is “polarized”.
Creating An Impulse Along An Axon

27. Continuous and saltatory conduction

28. Caffeine & the Nervous System

29. Conduction Across Synapses
Impulses are sent to:
Glands
Muscles
Other neurons.
Impulse must bridge the synapse for the message to be sent

30. Conduction Across Synapses
Synapses have ability to transmit impulses or inhibit impulse transmission.

31. Conduction Across Synapses
Presynaptic neuron
Synaptic vesicles
Neurotransmitter
Role of calcium ions
Synaptic cleft
Postsynaptic neuron.
receptors
Voltage gated channels
Na+/K+
Pump
Conduction Across A Synapse

32. Synaptic disruptions
Most brain disorders involve disruption of synaptic communication.
Toxins can block both the transmission and reception of neurotransmitters.

33. What is a nerve? Nerves are groups of neurons.
Mixed contain dendrites and axons.
Motor contain axons only. (Efferent)
Sensory contain dendrites only. (Afferent)

34. REGENERATION OF NERVOUS TISSUE
Neurons have limited powers of regeneration.
Neurons ability to reproduce is lost at 6 months of age.
A destroyed neuron is lost.
PNS neurons can repair.
CNS neurons cannot repair.
Axon regeneration