Coordination & Response Flashcards
Stimulus
A change in the internal or external environment
Receptor
Detects stimuli - groups of cells located in sense organs such as rods and cones
Effector
Cell that brings about a response to stimuli: muscle cells for nervous system, glands for endocrine system
Nervous system
All nerves in body.
CNS
Central Nervous System, brain and spinal cord only
3 types of neurone
Sensory, relay, motor
Reflex arc:
- Receptor detects stimulus
- Sends electrical impulses along sensory neurones to CNS
- CNS passes on message to relay neurone
- Relay neurone relay impulse to motor neurone
- Impulse travels to effector along motor neurone
- Effector responds accordingly
What is needed for coordinated response?
Stimulus, receptor, effector
What do reflexes do?
Prevent injury, don’t wait for brain to decide
Synapse
Connection between two neurones
Neurotransmitters at synapse:
- Impulse comes in and triggers release of vesicle
- Vesicle fuses with synaptic membrane.
- Neurotransmitters released.
- They diffuse across synaptic cleft.
- They bind to complementary receptors.
- Stimulates production of new impulse.
Conjunctiva
Lubricates and protects surface of the eye
Sclera
Tough outer layer that protects the eye
Cornea
Refracts light into eye, transparent, oxygen diffuses as no blood vessels
Iris
Controls diameter of pupil and therefore how much light enters eye
Pupil
Hole in middle that allows light in
Lens
Focuses light onto retina
Retina
Light-sensitive part of eye, covered in rods and cones
Fovea
Area with loads of cones
Optic nerve
Carries impulses from receptors to brain
Reflex in bright light
Circular muscle contracts, makes pupil smaller
Reflex in dim light
Radial muscle contracts, makes pupil bigger
Accomodation for far objects
Ciliary muscles relax, suspensory ligaments pull tight, lens goes thin, refracts light by smaller amount
Accomodation for near objects
Ciliary muscles contract, suspensory ligaments slacken, lens becomes fat, increases amound by which it refracts light