Lecture Notes: Nervous System

Question 1

central nervous system

Answer 1

1. Integration
2. Brain
3. Spinal Cord

Question 2

Integration

Answer 2

association of stimuli with output

Question 3

brain

Answer 3

integration of homeostasis, perception, movement, intellect and emotions

Question 4

spinal cord

Answer 4

reflexes + transmits information from skin and muscles to brain

Question 5

peripheral nervous system

Answer 5

1. sensory (afferent)- mechanoreceptors linked to the CNS

2. motor (efferent)- CNS controlling effector cells

Question 6

Voluntary (somatic)

Answer 6

• signals to skeletal muscles in response to stimuli

- reflexes and involuntary

Question 7

Autonomic

Answer 7

• Involuntary

- Parasympathetic and Sympathetic

Question 8

Parasympathetic

Answer 8

activities that gain and conserve energy

-slow heart beat, stimulate digestion

Question 9

Sympathetic

Answer 9

activities that increase expenditure of energy

Question 10

Neurons

Answer 10

transmission of electrical/chemical signals to conduct messages
- sensory, interneurons, motor

Question 11

Sensory neurons

Answer 11

stimulated by receptors triggered by environmental stimuli

Question 12

Interneurons

Answer 12

receive and transmit stimuli from and to other neurons

Question 13

Motor neurons

Answer 13

transmit impulses from CNS to effector cells

Question 14

Neuroglial cells

Answer 14

• do not conduct impulses
• support and orient
• protection
• insulation
• maintain ionic environment
• supply nutrients

Question 15

types of neuroglial cells

Answer 15

1. schwann cells (PNS)
2. ogliodendrocytes (CNS)
3. Astrocytes

Question 16

Ogliodendrocytes

Answer 16

myelin sheath; electrical insulation

increase speed of impulse propagation

Question 17

astrocytes

Answer 17

blood-brain barrier at brain capillaries

Question 18

neurons are excitable cells

Answer 18

• sodium potassium pump maintains a membrane potential
• neurons can change their membrane potential in response to stimuli
• selective opening of gated channels (voltage or chemical)

Question 19

Action Potentials

Answer 19

• rapid (1-2ms) reversal in membrane potential that propagates throughout a cell membrane without changing it’s magnitude.
• APs are only produced by depolarizing stimuli
• “All or nothing principle” must reach threshold

Question 20

all or nothing principle

Answer 20

• once a voltage threshold is reached the AP will occur
• amplitude of AP not affected by intensity of stimulus
• systems distinguishes between weak and strong stimuli based on frequency of AP

Question 21

Resting Phase

Answer 21

1. Sodium Potassium Pump
2. Leak Potassium channels: always open
3. Voltage-gated K+ channels: closed
4. Voltage-gated Na+ channels: closed
5. large negatively charged molecules remain inside
6. membrane potential: about -70 mV

Question 22

phases of an AP

Answer 22

1. depolarization
2. threshold
3. maximum depolarization
4. repolarization
5. hyperpolarization

Question 23

Depolarization

Answer 23

• Voltage-gated K+ channels: closed
• some voltage-gated Na+ channels opened
• –activation gate:open
• –inactivation gate:closed
• influx of sodium, causing membrane potential to decrease ( becomes more positive)`

Question 24

Threshold

Answer 24

• influx of sodium causes voltage gated sodium channels to open, which then causes a membrane potential threshold to be reached
• more voltage gated sodium channels open and there is more influx of sodium
• rapid reversal in membrane potential (inside more positive than outside.

Question 25

Maximum depolarization

Answer 25

1. voltage gated sodium channels begin to close, influx of sodium decrease a. activation gate: open b. inactivation gate: closed 2. voltage gated potassium channel:open a) slower than the voltage-gated sodium channel

Question 26

Repolarization

Answer 26

1. Voltage-gated Sodium channels: closed a. activation gate: open b. inactivation gate: closed 2. voltage-gated potassium channels: open - membrane potential returns to resting stage

Question 27

Hyperpolarization

Answer 27

1. voltage gated sodium channels:closed a. activation gate: closed b. inactivation gate: open 2. voltage gated potassium channels: open - membrane potential becomes more negative than resting potential - ends when voltage gated potassium channels close and cell returns to resting potential

Question 28

Refractory period

Answer 28

- allow AP to travel in one direction - ensure that depolarization and repolarization are completed before new AP - prevents prolonged depolarization of the membrane

Question 29

Absolute (refractory period)

Answer 29

- beginning of depolarization until shortly after repolarization is completed - once an AP starts - while voltage gated sodium channels are closed a. activation gate: open b. inactivation gate: closed - new AP is not possible

Question 30

relative (refractory period)

Answer 30

- during hyper polarization | - a stronger-than-threshold depolarizing stimulus is needed to produce an AP

Question 31

propagation of Action Potential

Answer 31

- strong depolarization of one area, depolarization above threshold in neighboring areas because sodium diffuses inside the axon - AP is regenerated at each new position along the membrane - AP moves in only one direction b/c refractory period

Question 32

speed ( in relation to AP)

Answer 32

increased diameter of axon, less resistance to the diffusion of sodium and increased speed

Question 33

saltatory conduction

Answer 33

- ions cannot cross the myelinated regions of axon - ion channels are concentrated at nodes of Ranvier - AP "jumps" between myelinated regions from one of ranvier to the next

Question 34

synapse

Answer 34

junction between the pre-synaptic cell and a post synaptic cell

Question 35

synaptic cleft

Answer 35

space between pre-synaptic membrane and post-synaptic membrane

Question 36

electrical synapses

Answer 36

- direct transmission via gap junction with connections (protein tunnels) - fast - AP can travel in both directions - no summation of inputs - do not allow for large numbers of synaptic inputs - little plasticity

Question 37

chemical synapses

Answer 37

better at integration of information

Question 38

transmission at chemical synapses

Answer 38

1. neurotransmitter is synthesized and packaged into vesicles at axon terminal 2. Ap arrives at presynaptic terminal, depolarization, gated calcium channels open, influx of calcium 3. acetylcholine vesicles fuse to membrane ane neurotransmitters are releases into synaptic cleft 4. neurotransmitter binds to receptor in postsynaptic membrane a) depolarization: excitatory, open sodium channels b) hyperpolarization: inhibitory, open gated potassium or chloride channels) 5. neurotransmitters are degraded and recycled

Question 39

summation of post-synaptic

Answer 39

- happens at the axon hillock - non-insulated and with many ion channels - input excitatory and inhibitory postsynaptic potentials spread to axon hillock - combination of input postsynaptic potentials may or may not result in AP at axon hillock - can occur spatially (simultaneous inputs) or temporally ( sequential inputs) - mechanism for integration of information