Nervous system Flashcards Preview

Grade 12 LS 2016 > Nervous system > Flashcards

Flashcards in Nervous system Deck (23):
0

Stimulus

  • Any internal or external change
  • To which an organism responds

1

Two types of coordinating system in humans

  • Nervous system
  • Endocrine system (hormones)
  • These two work together.

2

Homeostasis

  • Tendency to maintain a stable equilibrium between interdependent factors.
  • Especially important for organisms that function within a specific range of conditions.

3

Nervous coordination

  • Impulses conducted in nerves
  • For rapid responses

4

Chemical coordination

  • Hormones (chemical messengers) are transported in the blood
  • Relatively slower responses

5

Two main systems of the human nervous system

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)

6

Generalised process of responding to stimuli

Stimulus -> detection -> processing and integration -> response

7

How a stimulus is detected

Receptors detect stimuli and convert them into nerve impulses

8

How a response is actioned

Effectors (muscles and glands)

9

Components of nervous tissue

  • Nerve cells called neurons
  • Connective tissue called neuroglia

10

Main parts of a neuron

  • Dendrites
  • Cell body (cytoplasm and nucleus)
  • Axon (with myelin sheath)
  • Terminal branches of axon (synaptic knobs)

11

Dendrites

  • Conduct impulses to the cell body
  • One or more dendrites may be present in a neuron

12

Axons

  • Carry nerve impulses away from the cell body
  • Forms a number of terminal branches
  • Synaptic knobs at the tips

13

Myelin sheath

  • Nerve fibres outside CNS enclosed by myelin
  • Insulates the nerve fibres and accelerating impulse transmission
  • Formed by specialised Schwann cells
  • these wrap spirally around nerve fibres
  • myelin is a white fatty protein found in the cell membrane

14

Nodes of Ranvier

  • Gaps in the myelin sheath between Schwann cells
  • Speed up transmission as impulses jump from one node to another

15

Neurilemma

  • Outermost membrane of myelin sheath
  • Assist in repairing and regenerating damaged PNS neurons
  • (unmyelinated fibres and axons of the CNS cannot regenerate or be repaired)

16

Neuron structural classification

Depends on number of outgrowths from cell body:

  • Multipolar (more than two)
  • Bipolar (two)
  • Unipolar (one)

17

Neuron functional classification

  • Sensory (afferent) neurons - impulses from receptor to CNS
  • Motor (efferent) neurons - impulses from CNS to effectors
  • interneurons (connector neurons) - neurons of the CNS

18

Synapse

The gap between an an axons synaptic knob and a dendrite

19

How an impulse crosses a synapse

  • neurotransmitter chemicals
  • e.g. serotonin

20

Where neurotransmitters are formed and how they are released

  • synaptic vesicles alongside many mitochondria providing required energy
  • Impulses cause the vesicles to burst at the surface of the pre-synaptic membrane
  • The neurotransmitter is released into the synaptic cleft

 

21

How the nerotransmitter passes on an impulse to the dendrite.

  • The neurotransmitter moves across he synaptic cleft
  • It attaches to the post-synaptic membrane
  • This generates electrric signals that are conducted as nerve impulses to the cell body of the next neuron

22

The significance of a synapse

  • Signals only move in one direction
  • Impulses can be transmitted to many neurons, afecting more than one effector
  • Insignificant stimuli can be filtered out
  • The synapse filters out weak signals, preventing overloading of the CNS