The nervous system

Question 1

• Neurons

Answer 1

• trasnsmit electrical impulses

- do not physically touch another cell

Question 2

anatomy of neurons

Answer 2

• soma (cell body): house nucleus and other organelles
  
  • dendrites: recieve incoming signals
  • Axon hillock: integrate incoming signal to axon
  • Axon
  • Myelin (optional)
  • snaptic knob: maximizes neurotransmission to next neuron. ensures proper release of signal
  • Synapse: presynaptic terminus + synaptic celft + postsynaptic membrane.
  • Tracts: bundle of axons at PNS
  • Nerve: bundle of axons at CNS
    
    • sensory, motor, or mixed types
  • nuclei: bundle of cell bodies PNS
  • Ganglia: bundle of cell bodies CNS

Question 3

Purpose of Myelin

Answer 3

• prevents signal loss or crossing of signals so to maintain a signal within one neuron.
  - Increases speed of conduction.
  - form nodes of Ranriver

Question 4

what produces myelin sheath

Answer 4

• produced by oligodendrocytes (CNS) or schwann cells (PNS)

Question 5

• Other cells in the nervous system

Answer 5

• Glial / neuroglia:

Question 6

types of Glial cells

Answer 6

• Astrocytes:
  - Ependymal cells
  - Microglia
  - Oligodendrocytes and Schwann cells

Question 7

Function of astrocytes

Answer 7

• support cells for brain tissue
  - form blood-brain barrier
  - most abundant cell in the brain.

Question 8

Function of Ependymal cells

Answer 8

• produces cerebral spinal fluid (CSF)

Question 9

Function of Microglia

Answer 9

• phagocytizes waste products and pathogesn in CNS

Question 10

actions potential facts

Answer 10

• all or nothing messages

- cause release of neurotransmitters

Question 11

what is resting potential

Answer 11

the electric difference across the cell membrane (neurons = 70mV)

Question 12

what are the ions involved, concentrations, manner of movement across plasma membrane, and respective equilibrium potential

Answer 12

• Potassium
  - 140mM inside vs 4mM outside
  - Leak channels facilitate movement out of cell
  - Leaking continually occurs toward negative potential
  - equilibrium potential: movement inside vs outside is balanced at -90mV ( the - value indicates movement out of cell)
  - Sodium
  - 12mM inside vs 145 mM outside
  - movement into cell
  - facilitated by leak channels
  - encouraged by negative value and lower concentration inside the cell.
  - Equilibirum potential: movement is balanced at +60mV (the + value indicates movement into the cell)

Question 13

what is resting potential and why is that

Answer 13

• Resting poteintial is -70mV because of more potassium leak channels than sodium ones.

Question 14

Na/K ATPase facts

Answer 14

• maintain resting potential
  - pumps sodium out of cell
  - pumps potassium into cell
  - utilizes ATP

Question 15

importance of the axon Hillock

Answer 15

• site of summation for multiple singals (excitatory and/or inhibitory)

Question 16

Types of summation

Answer 16

• Temporal
  - multiple signals close to each other in time. (time frame)
  - spatial
  - multiple signals close to each other in space. (space frame)

Question 17

Basic function vs higher function of nervous system

Answer 17

Basic: associated with the senses, movement, and automatic function.

Complicated:associated with cognition, emotion, or consciousness

Question 18

upper motor neuron dysfunction

Answer 18

include hyperreflexia, clonus, hypertonia, and the babinski sign.

Question 19

lower motor neuron dysfunction

Answer 19

include atrophy, hypotonia, hyporeflexia, and skeletal muscle twitches.

Question 20

action potential

Answer 20

Neural information is coded for by the frequency and number of action potentials, not the size of the action potential.

Question 21

difference between nerves and tract

Answer 21

Nerves are collections of neurons in the peripheral nervous system and may contain multiple types of information (sensory or motor).
Tracts are collection of neurons in the central nervous system and contain only one type of information.
Neves may carry more than one type information; tracts can only carry one type of information,.

Question 22

If a chemist wants to make a drug that prevents GABA from binding to its receptor on the postsynaptic neuron. What should be true about this drug?

Answer 22

The drug should have LOWER Km than GABA and an ANTAGONIST for the receptor.

Terminology:

• Antagonist = blocker
• Agonist = activator.

Question 23

ependymal cells

Answer 23

line the ventricle of the brain
Produce CSF
form epithelial tissue called ependyma
cellular structure: simple cuboidal

Question 24

antagonists of voltage-gated potassium channels

Answer 24

Will render a neuron unable to repolarize.

Result in alot of neurotransmitter release.

Question 25

bypass the blood-brain barrier.

Answer 25

Since astrocytes form blood brain barrier. you would have to disrupt their tight junctions.

Question 26

Effect of demyelination

Answer 26

Results in slower transmission action potentials, delaying neurotransmitter release.

Question 27

Antagonist of potassium leak channels.

Answer 27

Results to decrease in potassium permeability therefore in PROGRESSIVE depolarization of the neuron as POSITIVE CHARGE builds up inside.

Question 28

Myelin's role in terms of capacitance

Answer 28

To DECREASE capacitance by blocking the accumulation of oppositely charged molecules along the axonal membrane.

Question 29

piloerection (hair standing end)

Answer 29

result of SYMPATHETIC MOTOR NEURON.

Question 30

- types of reflex arc:

Answer 30

- Monosynaptic - No interneuron at CNS b/w sensory and motor neuron - i.e knee jerk reflex - polysnaptic - contains atleast one interneuron between sensory and motor neuron. - i.e withdrawal reflex

Question 31

subdivision of the Autonomic Nervous System

Answer 31

- sympathetic - fight or flight - accelerate heart rate - inhibit digestion - releases epinephrine from adrenal medulla into blood stream ( these cells are derived from neural crest) - Originate in the middle of the spinal cord. - short axon to the synapse of another neuron. From there, there is a long axon to the target neuron. - parasympathetic - conserves energy - increase peristalsis and exocrine secretions - utilizes acetycholine (preganglionic and post ganglionic) - vagus nerve innervates thoracic and abdominal - originate in the brainstem or at the bottom of the spinal cord. - long axons to the synapse of another neuron, then a short axon to the target neuron.

Question 32

- Peripheral Nervous System (somatic and autonomic)

Answer 32

- includes 31 pairs spinal nerves and 10 cranial nerves | - connects CNS to rest of body

Question 33

- Somatic

Answer 33

- has sensory and motor fibers | - motor neuron goes directly from CNS to target tissue

Question 34

- Autonomic

Answer 34

- regulates - involuntary muscles (heartbeat, respiration, digestion and glandular secretions) - body temp - independent of conscious control - motor output has 2 neurons (preganglionic and postganglionic)

Question 35

supraspinal circuits

Answer 35

``` - used during times when a stimuli requires cerebral cortex processing before a response to generated. other times (i.e patellar tendon reflex), sensory stimuli is immediately followed by motor signal ```

Question 36

3 ways to regulate the synapse

Answer 36

- signal degradation (i.e acetycholinesterase - signal reuptake - lateral diffusion

Question 37

- Impulse propagation

Answer 37

- electrical movement of a signal down the axon followed by neurotransmitter release. - A one way direction. - speed factors - ⇡ axon length = ⇣ speed - ⇡ cross-sectional area = ⇡ speed - myelin = ⇡ speed - ⇡ stimulus intesity = ⇡ frequency

Question 38

Neurotransmitter pathway

Answer 38

- calcium influx → fusion of vesicles to membrane → exocytosis → neurotransmitter bind receptors (ion channel or G-protein) → depolarization or hyperpolarization.

Question 39

Sodium ions

Answer 39

- encouraged by negative value and lower concentration inside the cell. - Equilibirum potential: movement is balanced at +60mV (the + value indicates movement into the cell)

Question 40

potassium

Answer 40

- Leaking continually occurs toward negative potential - equilibrium potential: movement inside vs outside is balanced at -90mV ( the - value indicates movement out of cell)

Question 41

Dorsal root Ganglion

Answer 41

afferent (sensory) neurons | contains pseudounipolar neurons

Question 42

Graded potential

Answer 42

they are decremental ( their amplitude diminishes as they travel away from the original site) can also be hyperpolarizing or depolarizing, depending on the stimulus.