midterm 1

Question 1

PNS - afferent division

Answer 1

• somatic senses

- special senses

Question 2

PNS - efferent division

Answer 2

Somatic nervous system
- controls skeletal muscle

Autonomic nervous system

• Sympathetic and parasympathetic
• -> smooth muscle, cardiac muscle, glands
• Enteric
• -> smooth muscle and glands of GI tract

Question 3

Sensory function of NS

Answer 3

Sensory receptors detect external or internal stimuli, and relay sensory information to the brain and spinal cord for integration

Question 4

Integration function of NS

Answer 4

CNS analyzes sensory information, and makes decisions for appropriate responses

Question 5

Motor function of the NS

Answer 5

Motor information is conveyed from the CSN through cranial and spinal nerves of the PNS to appropriate effectors (muscles and glands)

Question 6

Astrocytes

Answer 6

Neuroglia of CNS

• most numerous
• help maintain BBB
• maintain extracellular chemical environment
• guide neurons during development
• play role in synapse formation

Question 7

Oligodendrocytes

Answer 7

Neuroglia of CNS

- form and maintain myelin sheath in CNS

Question 8

Microglia

Answer 8

Neuroglia of CNS

- phagocytes –> removes debris, damaged cells and pathogens

Question 9

Ependymal cells

Answer 9

Neuroglia of CNS

- Produce and assist in the circulation of CSF

Question 10

Schwann cell

Answer 10

Neuroglia of PNS

• form and maintain myelin sheath in PNS
• participate in PNS axon regeneration

Question 11

Functions of the myelin sheath

Answer 11

• Electrical insulation
  increases speed of conduction of action potentials
• Found in both CNS and PNS
  (Schwann cell = PNS)
  (Oligodendrocyte = CNS)
  **makes up white matter

Question 12

Plasticity

Answer 12

what can we do and can we change neurons through different types of adaptations
e.g. can you change size or quantity of muscle fibre composition

ABILITY TO CHANGE THROUGHOUT LIFE

Question 13

Repair

Answer 13

regeneration after damage

Question 14

Regeneration of PNS

Answer 14

occurs if:

• cell body is still intact
• Schwann cell remains active (produces myelin sheath)

Schwann cells form regeneration tube to guide and generate regrowth of axon
*dont always get regeneration, conditional on type of damage

Question 15

Regeneration of the CNS

Answer 15

little to none can occur due to:

• inhibitory proteins from the neuroglia
• absence of growth stimulating cues
• scar tissue formation
• *CNS damage is permanent

Question 16

Basic principles of electricity

Answer 16

1) force generated by the separation of charge = VOLTAGE
- this force has the potential to move charge = POTENTIAL
2) if charge can move then = CURRENT

Question 17

Resting membrane potential

Answer 17

all cells under resting conditions have a potential difference across their plasma membranes
- inside of cell = negative charge compared to outside
(intracellular space/fluid is more negatively charged than extracellular)

**magnitude of potential ranges from -5 to -100mv (always negative) depending on cell type

Question 18

Concentration gradient of cells

Answer 18

Inside of cell:

• more negative
• high K+ levels
• low Na+ levels
• if it can, potassium will always leave the cell

Outside of cell:

• more positive
• high Na+
• low K+
• sodium will always go into cell if poss

Question 19

Ion channels

Answer 19

specialized channels in cell membranes that allow the passage of charged Ionas across the membrane
–> because charged, moves as electrical current generated
(focus on Na+ and K+)

Question 20

Leak ion channels

Answer 20

randomly alternate between open and closed positions

• Na+ pump constantly working to fight but resting potential maintains
• *typically leak channels are for potassium

Question 21

Ligand-gated ion channels

Answer 21

opens or closes in response to a specific ligand (chemical/hormonal) stimulus

• channel stays closed until proper signaller binds to it
  e. g. change in pH from lactic acid buildup will cause some to open (surplus of hydrogen atoms)

Question 22

Mechanically-gated ion channels

Answer 22

opens or closes in response to mechanical stimulation in the form of

• touch
• pressure
• tissue stretching
• vibration
  e. g. found in bladder (stretch is most typical)

Question 23

Voltage-gated ion channels

Answer 23

opens in response to a change in membrane potential (voltage)
- hitting a certain threshold

Question 24

Graded potential

Answer 24

small deviation from resting membrane potential (minor because only 1 or 2 at a time)
localized current changes –> mechanically or ligand gated)
*if strong enough initiates action potential
generated by thermal, chemical, pressure and REQUIRED to cause action potential

Question 25

Depolarizing

Answer 25

makes the membrane potential less polarized | becomes more positive/less negative

Question 26

Hyperpolarizing

Answer 26

makes membrane potential more polarized (more negative) | position ion leaves the cell

Question 27

Action potentials

Answer 27

rapid, large changes in the membrane potential from depolarization to a reversal in polarity to depolarization to hyperpolarization - all or none with same amplitude - used to communicate over long distances * * on membranes with voltage gated channels

Question 28

Absolute refractory period

Answer 28

No stimulus will produce another action potential (regardless the strength) - Na+ channels are inactive - Membrane must depolarize - "No go zone"

Question 29

Relative refractory period

Answer 29

Supratheshold stimulus can produce action potential - membrane is in hyper polarized state - can last up to 10-15ms - stronger stimulus than usual can initiate potential

Question 30

Steps for communication across a synapse

Answer 30

1) action potential 2) voltage-gated Ca channels open 3) Calcium triggers exocytosis 4) Neurotransmitter diffuses and binds to receptor 5) Response in cell (then terminated by removing NT from synaptic cleft) 6) Degradation 7) Reuptake 8) Diffusion