Nervous system/Pupil reflex Flashcards
What do Schwann cells do?
Secretes lipid based substance (myelin) that’s used for myelin sheath that insulates the axon
Benefits of myelination
-Protects the neuron from damage
-Speeds up rate of nerve impulses
-Allows impulse to travel more efficiently without interference from neighboring neurons
Name of the uninsulated sections of the axon
Node of Ranvier
Nervous system has 2 main parts, what are they?
1)Central nervous system (brain and spinal chord)
2)Peripheral nervous system (nerves that branch off from the spinal chord and extend to all parts of the body)
Peripheral nervous system can be split into what systems?
Autonomic (involuntary)
Somatic (voluntary)
What does sympathetic system control?
The fight or flight response, active and alert.
Speeds up activity by activating effectors.
What does parasympathetic system control?
Regulates the rest and digest functions. Slows down activity by inhibiting effectors.
What antagonistic muscles control how much light enter the eye via the pupil?
Circular and radial muscles
Where do optic nerves pass information from and where does it end up?
From receptors in the retina to the brain
Pupil dilation 3 steps:
1)Low light intensity = impulses sent at low frequency by optic nerves to brain
2)Impulses sent down sympathetic motor neurons to radial muscles of iris
3)Radial muscles contract and pupil dilates
Pupil constriction 3 steps:
1)High light intensity = impulses sent at high frequency by optic nerves to brain
2)Impulses sent down parasympathetic motor neurons to circular muscles of iris
3)Circular muscles contract and pupil constricts
Why do myelinated axons conduct impulses faster than unmyelinated axons?
Saltatory conduction, impulse jumps from one node of Ranvier to another
Depolarisation can’t occur where myelin sheath acts, impulse doesn’t travel whole axon length
3 factors that affect speed of conductance:
-Myelin sheath
-Temperature
-Axon diameter
How does larger axon diameter increase speed of conductance?
Less resistance to flow of Sodium and Potassium ions
Differences between Sensory and Motor neuron:
1) Sensory neuron has cell body in middle, Motor has one at the end
2)Sensory has shorter axon
3)Sensory has longer dendron
4)Sensory doesn’t have motor end plate, Motor neuron induces muscle contractions
