Reflexes Flashcards
What are reflex actions?
Automatic actions that do not require conscious thought
Why are reflex actions important?
To help protect us from harm
What is the 5 step process that produces a reflex reaction?
- Receptors
- Sensory neuron
- Relay neuron
- Motor neuron
- Effector
Give 2 features of reflexes:
- Reflexes need to be fast
- Electrical signals bypass parts of the brain and travel down a relay neuron to speed up transmission
What does a relay neuron do?
Transfers information from sensory to motor neurons
Name 3 reflexes only observed in babies:
- Palmar reflex
- Moro reflex
- Rooting reflex or sucking reflex
What is an electrical impulse?
An electrical signal that travels along the axon of a neuron
What is a presynaptic neuron?
The neuron that sends the signal across the synapse
What is a vesicle?
A small membrane-bound sac that stores neurotransmitters
What is a neurotransmitter?
A chemical messages released by neurons to transmit signals across a synapse
What is a presynaptic neuron?
The membrane of the presynaptic neuron where vesicles release neurotransmitters
What is a synapse?
The junction between 2 neurons where neurotransmitters are released to transmit signals
What is a synapse?
The junction between 2 neurons where neurotransmitters are released to transmit signals
What is a post-synaptic neuron?
The neuron that receives the signal after it crosses the synapse
What is the post- synaptic membrane?
The membrane of the post-synaptic neuron that contains receptors for neurotransmitters.
What is a post-synaptic receptor?
Proteins on the post-synaptic membrane that bind to neurotransmitters to receive the signal
What is the knee jerk test?
Tapping on the knee stretching the muscle/tendon and the muscle contracts, lifting the leg.
Protects the muscle from overstretching
What is the blink test?
Changing light levels and muscles cause the eye lid to close
Protects eye from potential damage
What is the pupil response to light test?
Increased light and muscles cause the iris to get bigger, causing the pupil to get smaller
Protect the retina from excess light
What is the pupil response to dark test?
Reduced light and muscle cause the iris to get smaller, causing the pupil to dilate
Allows more light to enter the eye, allowing the subject to see in poor light
What is the ankle jerk reflex test?
Tap on the Achilles tendon, stretching the muscle and the calf muscle contracts, extending the door
Protects the calf muscle from overstocking
How is the impulse transmitted? (5)
- An impulse arrives at the end of the presynaptic nerve
- Vesicles move towards and fuse with the presynaptic membrane. This releases neurotransmitters info the synaptic cleft
- The neurotransmitters diffuse across the synaptic cleft (down a concentration gradient)
- Neurotransmitters attach to receptors on the postsynaptic membrane
- This triggers an impulse which travels along the postsynaptic neuron
- The neurotransmitters are recycled or destroyed once an impulse is sent
