Nervous system

Question 1

Two types of coordinating system in humans

Answer 1

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

Question 2

Homeostasis

Answer 2

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

Question 3

Nervous coordination

Answer 3

• Impulses conducted in nerves
• For rapid responses

Question 4

Chemical coordination

Answer 4

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

Question 5

Two main systems of the human nervous system

Answer 5

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

Question 6

Generalised process of responding to stimuli

Answer 6

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

Question 7

How a stimulus is detected

Answer 7

Receptors detect stimuli and convert them into nerve impulses

Question 8

How a response is actioned

Answer 8

Effectors (muscles and glands)

Question 9

Components of nervous tissue

Answer 9

• Nerve cells called neurons
• Connective tissue called neuroglia

Question 10

Main parts of a neuron

Answer 10

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

Question 11

Dendrites

Answer 11

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

Question 12

Axons

Answer 12

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

Question 13

Myelin sheath

Answer 13

• 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

Question 14

Nodes of Ranvier

Answer 14

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

Question 15

Neurilemma

Answer 15

• 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)

Question 16

Neuron structural classification

Answer 16

Depends on number of outgrowths from cell body:

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

Question 17

Neuron functional classification

Answer 17

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

Question 18

Synapse

Answer 18

The gap between an an axons synaptic knob and a dendrite

Question 19

How an impulse crosses a synapse

Answer 19

• neurotransmitter chemicals
• e.g. serotonin

Question 20

Where neurotransmitters are formed and how they are released

Answer 20

• 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

Question 21

How the nerotransmitter passes on an impulse to the dendrite.

Answer 21

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

Question 22

The significance of a synapse

Answer 22

• 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

Question 23

Stimulus

Answer 23

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