Unit 2

Question 1

Endocrine system

Answer 1

• releases hormones that circulate through the body in blood streams
  —exerts influence on distant cells
  — response is slow and widespread

Question 2

Endocrine cells

Answer 2

• organized into endocrine glands

Question 3

Endocrine glands

Answer 3

• ductless
  -release hormones directly into capillaries

Question 4

Target cells

Answer 4

• possess receptor molecules
• recognize hormones and bind the hormone
  — only cells with the receptor can respond

Question 5

Neurons

Answer 5

1. Stimuli received by dendrites
2. Stimuli summed at axon hillock
   - action potential is triggered
3. Potentials conducted to axon terminal
   - cause release of neurotransmitters

Question 6

Resting membrane potential

Answer 6

• -70 mV
• Na/K pumps moves sodium ions out of cell and potassium cells into cell
• potassium channels allow potassium ions to leak out of school
  — results in negative resting potential inside cell (relative to outside)

Question 7

Depolarization

Answer 7

-when neuron is excited, the inside of its membrane become less negative
— if depolarization at axon hillock exceeds threshold voltage, the cell fires an action potential

Question 8

Actions potentials

Answer 8

1. Threshold potential is exceeded
2. Voltage gated sodium rapidly enters cells
   - causes positive spike
   -sodium channels open slowly
3. Voltage rises to 40mV
   - sodium channels close
   - potassium channels remain open
   -membrane becomes more negative
4. Hyperpolarization
   - overshoot of potassium cells leave cell
   -causes refractory period
5. Membrane gradually returns to resting
   - excess potassium ions returned to cell via pumps

Question 9

Refractory period

Answer 9

Period where inside membrane voltage falls below resting potential
- neuron cannot fire second action potential because
— sodium channels are closed and potassium channels are open
-duration of this period varies but limits fastest firing frequency

Question 10

Saltatory propogation

Answer 10

• layers of myelin insulate the axon
  —increases speed of conduction
  -action potentials jump between nodes of ranvier
  — at these nodes, there is a buildup of positive charges inside and negative charges outside

Question 11

Synaptic transmission

Answer 11

1. Depolarization of axon terminals open calcium channels
2. vesicles respond by fusing with pre synaptic membrane
   - releases neurotransmitters into cleft
3. Neurotransmitters bind with receptors on post synaptic cells
   -open channels that allow ions in
4. Neurotransmitters are reabsorbed into presynaptic terminal
   -stored in vesicles until next action potential

Question 12

Sensory transduction

Answer 12

• sensory receptor cells
  — different cells are affiliated with different senses
  — ex. Hearing relies on mechanoreceptors

Question 13

Encoding stimulus strength

Answer 13

Action potential firing rates correlate with the intensity of the stimulus

Question 14

Excitatory vs inhibitory signals

Answer 14

• effects of neurotransmitter binding depends on type of post synaptic cells
  1. Depolarized cell
• potential is excitatory (EPSP)
• opens ligand-gated sodium channels
  2. Hyper-polarized cell
• potential is inhibitory (IPSP)
• opens ligand-gated calcium and potassium channels