1. What 2 structures make up the central nervous system?

Brain and spinal cord

2. Define ganglia.

small masses of nervous tissue-  consisting of neuron cell bodies located outside CNS

3. What are the 3 divisions of the peripheral nervous system?  What does each division do?

   1. Somatic NS (controls voluntary actions)

                                               i.     Sensory neurons that convey information to CNS from:

1.     somatic receptors in head, body wall, limbs

2.     receptors for special senses (vision, hearing, taste, and smell)

3.     Somatic motor neurons that conduct impulses from CNS to skeletal muscles only

b.     Autonomic NS (control involuntary actions)

                                               i.     Consists of sensory neurons that convey information to CNS from autonomic sensory receptors located in:

1.     visceral organs (stomach, lungs)

2.     Autonomic motor neurons that conduct nerve impulses from CNS to smooth and cardiac muscle control

                                              ii.     Motor part of autonomic NS consists of 2 parts:

1.     Sympathetic Division-supports exercise or emergency actions (flight or fight response)

2.     Parasympathetic Division-”rest and digest” activities

Effectors receive nerves from both divisions and the two divisions have opposing actions

Dual innervation

Sympathetic neurons increase heart rate and parasympathetic neurons slow it down

c.     Enteric NS

                                               i.     Controls involuntary actions of GI tract

                                             ii.     “intrinsic NS” – a division of autonomic NS that governs function of gastrointestinal tract

                                           iii.     It used to be considered part of autonomic NS (didn’t have own name)

1.     Many neurons of enteric plexuses function independently of the ANS and CNS

2.     Some neurons do communicate with CNS via sympathetic and parasympathetic neurons

                                            iv.     Consists over 100 million neurons that extend most of length of GI tract

4. What are the 2 divisions of the autonomic nervous system?

   1. Sympathetic Division-supports exercise or emergency actions (flight or fight response)

   2. Parasympathetic Division-”rest and digest” activities

5. What are the 3 functions of the nervous system? 

Sensory, integrative, and  motor

6. What are the parts of a neuron? (cell body, Nissl bodies, neurofibrils, microtubules, Schwann cell, myelin sheath, neurolemma, axon, dendrites, Nodes of Ranvier, axoplasm, axolemma, synapse)

a.     Cell body- Also called “perikaryon” or “soma” Contains nucleus surrounded by cytoplasm that includes organelles (lysosomes, mitochondria)

b.     Nissl bodies Contain free ribosomes (site of protein synthesis) and rER termed

c.     Neurofibrils- provide structure and support

d.     Microtubules assist in moving materials between cell body and axon

e.     Schwann cell

f.      Myelin sheath- Axon is surrounded by multilayered lipid and protein covering

g.     Neurolemma???

h.     Axon- Propagates nerve impulses toward another neuron, muscle fiber, or gland cell

i.      Dendrites - Receiving or input portion of neuron

j.      Node of Ranvier

k.     Axoplasm- cytoplasm of axon

l.      Axolemma- plasma membrane of axon

m.   synapse site of communication between 2 neurons or between neuron and effector cell (ex. muscle)

7. Structural classification of neurons.  Know definitions.

•       Classified by number of processes extending from cell body

1. Multipolar neurons

•       Several dendrites and 1 axon

•       Most neurons in brain and spinal cord, and motor neurons

2.     Bipolar Neurons

•       1 main dendrite and 1 axon

•       Retina of eye

•       inner ear

•       olfactory area of brain

3.     Unipolar neurons

•       Dendrites and 1 axon that are fused together

•       form continuous process that emerges from cell body

•       Dendrites function as sensory receptors that detect sensory stimuli (touch, pressure, pain, or thermal)

8. Functional classification of neurons.  Know definitions.

•       Classified according to direction in which nerve impulse (action potential) is conveyed with respect to CNS

1. Sensory Neurons(afferent neurons)

•       Once stimulus activates sensory receptor:

•       sensory neuron forms action potential in axon and action potential is conveyed INTO CNS

•       Most are unipolar in structure

2.     Motor Neurons (efferent neurons)

•       Convey action potentials AWAY from CNS to effectors (muscles or glands) in PNS through cranial or spinal nerves

•       Most are multipolar in structure

3. Interneurons

•       Located within CNS between sensory and motor neurons

•       Process incoming sensory information from sensory neurons

•       then elicit motor response by activating motor neurons (integrate)

•       Most are multipolar in structure (several dendrites and 1 axon)

9. Name the 4 neuroglial cells of the central nervous system (CNS).  Functions?  Of the neuroglial cells of the CNS, which is the most numerous? astrocytes  Which neuroglial cells form the myelin sheath in the CNS? Oligodendrocytes Which cells are found lining the ventricles in the brain? Endymal cells

Astrocytes

9. Star-shaped cells that have many processes

10. Largest and most numerous

11. Functions:

                                               i.     Support neurons (strength) – contain microfilaments that give them strength and help support tissue

                                              ii.     Isolate neurons of CNS from harmful substances in blood

                                             iii.     Secrete chemicals that regulate growth and interconnection among neurons in brain (embryo)

                                             iv.     Play role in learning and memory by influencing formation of neural synapses

Oligodendrocytes

a. Resemble astrocytes but are smaller and contain fewer processes

b. Processes are responsible for forming and maintaining myelin sheath around CNS axons

Microglial cells

a. Small cells with slender processes that give off spine-like projections

b. Function as phagocytes-remove cellular debris and phagocytize microbes

Ependymal cells

a.     Line ventricles of brain and spinal cord

b.     Produces cerebrospinal fluid

10. What are the 2 neuroglia cells of the PNS?  Function of each?

Schwann cells

10. Encircle PNS axons

11. Forms myelin sheath of single axon

                                               i.     Single oligodendrocyte myelinates several axons

                                              ii.     whereas each Schwann cell myelinates a single axon

10. Participates in axon regeneration (more easily done in PNS)

Satellite Cells

10. Flat cells surround cell bodies of neurons of PNS ganglia

11. Regulate exchanges of materials between cell bodies and interstitial fluid

11. When a neuron in the PNS is injured, what part of a Schwann cell aids in regeneration to form a new axon? Neurolemma

12. Why is white matter white?  Why is gray matter gray? 

    1. White matter is white because its composed of  fibers who have a protective sheath called myelin

    2. Gray matter is gray because its made up of nerve cell bodies

13. What are the 4 types of ion channels we discussed in class?  Where are each located (discussed in class) and how does each work?

·      Leak channels - Plasma membranes have more potassium (K⁺) ion channels than sodium ion (Na⁺) leak channels

K⁺ channels are also “leakier” than Na⁺ ion channels

            Losing  more positive ions than gaining!

•       Ligand-gated channels- Opens and closes in response to binding of ligand or chemical (neurotransmitters, hormones, ions) signal (neuromuscular junction!)

•       Located: dendrites of some sensory neurons (pain receptors) and dendrites and cell bodies of motor neurons\

•       Ex: acetylcholine opens channels that allow Na⁺ and Ca²⁺ to diffuse in and K⁺ to diffuse out

•       Mechanically-gated channels- Opens or closes in response to mechanical stimulating

in form of vibration (sound), touch, pressure, or tissue stretching

•       Located: dendrites of sensory neurons (touch, pain, and pressure receptors) and in auditory receptors in ears)

•       Voltage-gated channels - This charge depends on the movement of ions

•       If positively charged ions leave the cell (K⁺), then the charge becomes less negative. Stimuli causes change to membrane potential (less negative)

* And it opens the channel

•       Location: all neuron types

14. What is the resting membrane potential of a neuron? (value)

-70mV

15. What 3 factors maintain a negative resting membrane potential?

1.     Unequal distribution of ions in extracellular fluid

2.     Inability of most anions to leave cell

3.     Na+ K+ pumps (primary active pump L->H)

16. What is the threshold potential of a neuron? (value)

-55mV

17. Describe graded potential, hyperpolarizing graded potential, and depolarizing graded potential.

18. Know the different phases to an action potential.  Which channels open and what ions flow in or out of the cell during each phase.

a.     Depolarizing Phase- Negative membrane potential (-70 mV) becomes less negative, reaching 0, then becomes positive

                                               i.     Voltage-gated Na⁺ channels open and Na ⁺ rushes in (more positive)

b.      Repolarizing Phase- Membrane potential is restored to resting state of -70 mV

                                               i.     voltage-gated K ⁺ channels open and K ⁺ flows out (becomes more negative)

c.     Hyperpolarizing Phase- Membrane potential temporarily becomes more negative than resting

                                               i.     Voltage-gated K ⁺ channels remain open after repolarizing phase

19. Describe refractory period, absolute refractory period, and relative refractory period.

Refractory period-time after an action potential begins

19. during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus

Absolute refractory period- even a very strong stimulus cannot initiate second action potential

Relative refractory period -period of time during which a second action potential can be initiated but only by a larger than normal stimulus

20. What is a presynaptic and postsynaptic neuron?

Synapse-regions where communication occurs between 2 neurons or between a neuron and effector cell (muscle or gland)

Presynaptic neuron --nerve cell that carries nerve impulse toward synapse (sends signal)

Postsynaptic neuron-cell that receives signal

21. What is a synaptic cleft?  What does a synaptic bulb contain? What are synaptic vesicles and what do they hold and release?

Synaptic cleft--space that separates neuron and muscle

Synaptic bulb contain synaptic vesicles

Synaptic vesicles store neurotransmitters that excites or inhibits another neuron, muscle fiber, or gland cell

22. What are the steps to a chemical synapse process?  Know the order.  What ions are involved?  See figure.

1.     . Presynaptic neuron – nerve impulse

2.     Depolarization phase. Opens voltage-gated Ca²⁺ channels and Ca²⁺ flows in

3.     Vesicle membranes merge with plasma membrane and neurotransmitters within vesicles are released into synaptic cleft

4.     Neurotransmitters diffuse across cleft and bind to neurotransmitter receptors in postsynaptic neuron’s plasma membrane

5.     Binding of neurotransmitters to receptors on ligand-gated channels:

opens channels and allows ions (Na+) to flow across membrane

6.     As ions (Na+) flow through opened channels:

1.     voltage across membrane changes and is called postsynaptic potential. Depolarization occurs

7.     . When depolarizing postsynaptic potential reaches threshold:

8.     it triggers AP in postsynaptic neuron

23. How are neurotransmitters removed from the synaptic cleft?  There are 3 ways.  Refer to slides.

Diffusion- Away from synaptic cleft and cannot bind with receptor

Enzymatic Degradation- Inactivated through enzymatic degradation

23. Ex. Acetylcholine inactivated by acetylcholinesterase

Uptake by Cells- Actively transported back into neuron that released them