2. Friday - 3/11/16
Question of the Day
Agenda
In a neuron, what are the functions of dendrites and the myelin sheath?
Microglial cells dispose of debris by using the process of _____.
Review
Nerve impulse notes
Nerve impulse activity

4. Basic functions of the nervous system
Sensory – gathers info
Integrative – information is brought together
Motor – responds to signals, restores homeostasis

5. Organization of the nervous system

7. Organization of the nervous system
Subdivision composed of the brain and spinal cord?
Subdivision of the PNS that controls voluntary activities?
Nervous system subdivision composed of cranial and spinal nerves?
Subdivision of PNS that regulates the activity of the heart and smooth muscle?
Subdivision that interprets incoming information?
Subdivision that carries impulses from the CNS to organs, glands and muscles?

8. Nervous tissue: structure and function
Supporting Cells (Neuroglia)
Astrocytes (anchor to nutrient supply lines, forms blood-brain barrier)
Microglia (dispose of debris)
Ependymal cells (protective cushion (CSF) around CNS – line cavities of brain and spinal cord)
Oligodendrocytes (produces myelin sheath)
Neurons
Nerve cell
Transmits messages (nerve impulses)

10. Structure of a neuron

11. Structure of a neuron Cell body: contains the nucleus
Dendrites: Receive incoming messages (toward cell body) – may have hundreds
Axon: Conducts impulses away from the cell body – 1 per neuron

12. Structure of a neuron
Myelin sheath: wraps the axon to insulate and speed up the rate of nerve impulse transmission
Schwann cells: produce myelin (in the PNS (motor neurons)
Node of Ranvier: gap in insulation, speeds up action potential

13. Structure of a Neuron
Axon terminal: end of axon – has vesicles that holds neurotransmitters
Synapse: junction separating the axon terminal – where NT’s are released into

14. Multiple sclerosis
Multiple Sclerosis

16. Nerve impulse conduction
Na - In (15) Out (150)
K - In (140) Out (5)
Nerve impulse conduction
An inactive neuron is at its resting membrane potential
The inside of the cell is more negatively charged than the outside of the cell (channels are closed)
Na ions outside/ K ions inside
Plasma membrane is relatively impermeable to both Na and K

17. Nerve impulse conduction
When a neuron is stimulated by an action potential (nerve impulse) the permeability of the plasma membrane changes for a short period of time.
Sodium channels open and sodium ions diffuse into the cell = DEPOLARIZATION
Action potential travels length of axon (all or nothing) when threshold is reached

18. Nerve impulse conduction
After sodium ions enter the cell, the permeability changes again and becomes impermeable to sodium, but permeable to potassium
K ions diffuse out of the neuron which restores the electrical conditions at resting membrane potential = REPOLARIZATION
Another action potential cannot be conducted without repolarization

19. Nerve impulse conduction
After repolarization, the sodium potassium pump restores the concentration of Na and K inside and outside of the neuron
Requires ATP

20. Nerve impulse conduction animation
Why does my foot fall asleep?

22. impulse transmission at synapse
Action potential reaches the axon terminal where vesicles release neurotransmitters

23. Impulse transmission at synapse
NT’s diffuse across the synapse and bind to receptors on the membrane of the next neuron
If enough NT is released, the whole series (depolarization…) will occur leading to the nerve impulse traveling down the neuron

24. Neurotransmitters released
Acetylcholine
Epinephrine/Norepinephrine
Dopamine
Serotonin

25. Reflexes

26. Reflexes Rapid and involuntary responses to stimuli
Occur in pathway called reflex arc
2 types
Somatic
Autonomic

27. Reflexes that stimulate the skeletal muscles
Somatic reflexes
Reflexes that stimulate the skeletal muscles
Autonomic reflexes
Regulate activity of smooth muscle, heart, glands, saliva, pupil size, and BP

28. Reflex arc

29. Reflexes
Many reflexes involve only spinal cord neurons and occur without brain involvement

31. Sympathetic Nervous System
“Fight or flight” reaction
Parasympathetic Nervous System
“Rest and digest”