CH 7, Part 1-4

Question 1

Central Nervous System (CNS)

Answer 1

Made up of brain and spinal cord

Question 2

Peripheral Nervous System (PNS)

Answer 2

Nerves

Question 3

Structural Classes of a Neuron

Answer 3

• inside of nerves are neurons
  (1) Motor Neurons
  
  • “efferent neurons”
  • send info in form of electrical impulses from CNS outwards, towards periphery of body (heart, skin, muscles, etc.)
    (2) Sensory Neurons
  • “afferent neurons”
  • send info from periphery of body back towards CNS

Question 4

Motor Neurons

Answer 4

(1) Somatic
- conscious control over when neurons pass info from CNS to periphery
- all go to skeletal muscle fibers which allow body to move
(2) Autonomic
- goes to organs throughout body and generates electrical impulses on their own
- do NOT have conscious control over
(a) Sympathetic
- causes fight or flight response (prepare for physical activity)
- release norepinephrine -> heart rate and respiratory rate increase, digestion decreases
(b) Parasympathetic
- part of rest and digest nervous system
- activated during relaxation
- heart rate and respiratory rate decrease, digestion increases

Question 5

Anatomy of a Neuron

Answer 5

DENDRITE
- thousands of extensions that come off of cell body
- receive info, send info to axon hillock

AXON
- one long projection

AXON HILLOCK
- beginning of an axon
- receives info from dendrites and decides if action potential will happen or not

AXON TERMINAL
- branches of an axon

AXON TERMINAL BUTTON
- filled with vesicles containing neurotransmitters
- pass info to another neuron’s dendrites

STRUCTURAL ORGANIZATION
- Nucleus: collection of neuronal cell bodies in CNS
- Nerve: bunch of axons bound together in PNS
- Ganglion: collection of cell bodies within a nerve

Question 6

Myelin Sheath

Answer 6

• wrapping of fat (fatty acids) that exist around the axons
  
  • elongated plasma membrane of cell wrapped around an axon of a neuron
  • allows action potentials to propagate significantly faster
  • most of myelinated neurons’ axons are wrapped
• Oligodendrocytes: creates myelin sheath around neurons in CNS
  
  • can create multiple sections of myelin sheath around multiple different neurons
• Schwann cells: creates myelin sheath in PNS
  
  • only creates one section of myelin sheath around one neuron

Question 7

Resting Membrane Potential

Answer 7

• every cell in body is negatively charged
• interior of a neuron is -70 mV
• difference in voltage across the plasma membrane

(1) Chemical Driving Force
- diffusion gradient
- high –> low
(2) Electrical Driving Force
- inside of cell negatively charged so will pull ions with positive charge towards it
- fluid must be charged
- will pull ions with opposite (positive) charge towards it

• Equilibrium Potentials (Ek): When chemical and electrical driving forces are equal
• Cells are significantly more permeable to K+ than Na+
• the more permeable the membrane is to an ion, the closer mV will be to that ion’s Ex

Question 8

Action Potentials

Answer 8

• electrical wave of changes in the voltage across a membrane
• occur in membranes of excitable cells in response to graded potentials that sum together to reach a threshold
• not decremental, so can be propagated long distances without a decrease in amplitude

Question 9

Neuron Repolarization

Answer 9

• Neurons can generate around 2,000 action potentials in 1 second
  
  • So must get regions of +30 mV back to -70 mV so that one can occur