CNS: structure and function Flashcards

1
Q

What are the functions of the nervous system?

A
  • control of the internal environment
  • voluntary control of movement
  • spinal cord reflexes
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2
Q

Describe the peripheral nervous system

A

Neurons outside the CNS

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3
Q

Describe the sensory division

A

afferent fibres transmit impulses from receptors to CNS

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4
Q

Describe the motor division

A

efferent fibres transmit impulses from the CNS to effector organs

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5
Q

What 2 types of input make up sensory nervous system?

A

somatic sensory
visceral sensory

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6
Q

What 2 types of input make up motor nervous system?

A

somatic motor
autonomic motor

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7
Q

What does the axon (nerve fibre) do?

A
  • carries APs away from cell body
  • covered by Schwann cells (forms discontinuous myelin sheath)
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8
Q

What does it mean if the axon diameter is larger or there is increased myelin sheath?

A

greater speed of neural transmission

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9
Q

When a cell is polarised, does it have a positive or negative charge?

A

Negative.
–5 to –100 mv
-40 to –75 mv in neurons

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10
Q

What is the magnitude of a resting membrane potential determined by?

A
  1. Permeability of plasma
    membrane to ions.
  2. Difference in ion concentrations
    across membrane
    * Na+, K+, C, and Ca+2
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11
Q

What ions plays most important role in generating resting membrane potential?

A

Na+ (greater conc on outside of cell) and K+ (greater conc on inside of cell)

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12
Q

How is resting membrane potential achieved?

A

Maintained by sodium-potassium pump
–Potassium tends to diffuse out
of cell
–Na+/K+ pump moves 2 K+ in
and 3Na+out

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13
Q

AP occurs when a stimulus of sufficient strength depolarizes the cell, how?

A

Opens Na+ channels, Na+ diffuses into cell (inside becomes more positive)

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14
Q

What is the all-or-none law?

A

Once a nerve impulse is initiated, it will travel the length of the neuron

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15
Q

What are the 2 ways in which excitatory postsynaptic potentials can promote depolarization?

A

1) Temporal summation - Rapid, repetitive excitation from a single excitatory presynaptic neuron
2) Spatial summation - Summing EPSPs from several different presynaptic neurons.

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16
Q

What do inhibitory postsynaptic potentials cause?

A

Hyperpolarization (more negative resting memb potential)..
- Neurons with more negative memb potential resist depolarization

17
Q

What are the 2 types of mechanoreceptors?

A
  • Muscle spindles
  • Golgi tendon organs
18
Q

Define propriception

A

The sense of the body’s position in space based on specialized receptors that reside in the muscles, tendons and joint.

19
Q

What are proprioreceptors?

A

sensors that provide information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the
limb in space.

20
Q

What do muscle spindles respond to, and consist of?

A

Respind to changes in muscle length.
Consist of:
- Intrafusal fibres
- Gamma motor neurons

21
Q

What is the function of the muscle spindle?

A

To assist in the regulation of movement and maintain posture.

22
Q

What do Golgi tendon organs do?

A

Monitors force development in muscle
- prevents muscle damage during excessive force generation

23
Q

Stimulation of GTO does what?

A

Results in reflex relaxation of muscle
- inhibitory neurons send inhibitory postsynaptic potentials to muscle alpha motor neurons

24
Q

What may the ability to voluntarily oppose GTO inhibitioin be related to?

A

Gains in strength with training due to increased tendon stiffness

25
Q

What is the innervation ratio?

A

Number of muscle fibres innervated by a single motor unit
- low ratio involved in fine motor control
- high ratio in muscles requiring power/less fine motor control

26
Q

What is motor unit recruitment?

A

Recruitment of additional muscle fibres by activting more motor units

27
Q

What is the size principle?

A

The orderly and sequential recruitment of larger motor units during exercise (smaller MU recruited 1st)

28
Q

What 3 components is the brain stem made out of?

A
  • Midbrain
  • Medulla Ob
  • Pons
29
Q

What is ‘spinal tuning’?

A

Refers to intrinsic neural networks within spinal cord that refine voluntary movements after receiving messages from higher brain centres.

30
Q

How do astrocytes prevent prolonged (unwanted) effects at synapses?

A

If more glutatmate released from presynaptic terminal than required, most is removed by astrocytes surrounding synaptic cleft. Glutamate converted to glutamine and then released to neuron which converts back to glutamate and stores it in vesicles ready for next AP.

31
Q

Describe convergence and divergence

A

Convergence - when a neuron receives input from many other neurons
Divergence - when a neuron synapses with many other neurons

32
Q

Can neurons receive multiple presynpatic inputs?

A

Yes! excitatory and inhibitory. Inputs closer to axon hillock have greater effect than those further away