Reflex actions (7)

?
Knee jerk reflex definition
A reflex action that straightens the leg when the tendon below the knee cap is tapped
1 of 22
Reflex action definition
A response that does not involve any processing by the brain
2 of 22
What are the 3 neurones that most reflex pathways consist of?
Sensory neurone, relay neurone, motor neurone
3 of 22
What may a reflex be used for?
To get out of danger, to avoid damage to part of the body, to maintain balance
4 of 22
2 examples of a reflex action
Blinking reflex and knee jerk reflex
5 of 22
What does the blinking reflex cause?
A temporary closure of the eyelids to protect the eyes from damage
6 of 22
Why can the blinking reflex be called a cranial reflex?
The nervous pathway for the blinking reflex passes through part of the brain
7 of 22
Why is the blinking reflex a reflex arc?
The receptor and effectopr are in the same place
8 of 22
Blinking may be stimulated by sudden cahnges in the environment such as:
a foreign object touching the eye (the corneal reflex), sudden bright light (the optical reflex), loud sounds, sudden movement clsoe to the eye
9 of 22
What is the corneal reflex mediated by?
A sensory neurone from the cornea, which enters the pons
10 of 22
How does blinking occur?
The sensory neurone connects to the relay neurone by a synapse, which passes the action potential to the motor neurone. The motor neurone passes back out of the brain to the facial muscles, causing the eyelid to blink.
11 of 22
Why is the corneal reflex rapid?
It is a very short and direct pathway (takes approx 0.1 seconds)
12 of 22
How can the reflex be overriden by conscious control?
The sensory neurone passes the action potential to myelinated neurones in the pons, which carry the action potential to the sensory region in the cerebral cortex, informing the higher centres of the brain the stimulus has occurred.
13 of 22
How can infoming the higher centres of the brain that a stimulus has occurred, prevent the formation of an action potential in the motor neurone?
The higher parts of the brain (cerebral cortex) can send inhibitory signals to the motor centre in the pons, much faster than the signals sent from the pons. Therefore, the inhibitory action potentials can prevent the formation of an action potential
14 of 22
How does the optical reflex protect the light-sensitive cells of the retina from damage?
The stimulus is detected by the retina and the reflex is mediated by the optical centre in the cerebral cortex. The optical reflex is slightly slower than the corneal reflex.
15 of 22
What is the knee jerk reflex?
A spinal reflex - the nervous pathway passes through the spinal cord rather than through the brain
16 of 22
Step 1 of the knee jerk reflex?
The muscle at the front of the thigh (quadriceps) contracts to straighten the leg
17 of 22
Step 2 of the knee jerk reflex?
The quadriceps are connected to the lower leg via the patella tendon
18 of 22
Step 3 of the knee jerk reflex?
When the quadriceps are stretched, stretch receptors (muscle spindles) detect the increase in length of the muscle.
19 of 22
What happens if this stretching is unexpected?
A reflex action causes contraction of the same muscle
20 of 22
Why is the knee jerk reflex unusual?
The nervous pathway consists of only 2 neurones (sesnory and motor), so there is one less synapse involved making the response quicker
21 of 22
When the higher parts of the brain are informed of the reflex occurring, how does it inhibit the action potential when no relay neurone is present?
Relies on rapid myelinated neurones carrying the inhibitory action potentials to the synapse before the motor neurone is stimulated.
22 of 22

Other cards in this set

Card 2

Front

Reflex action definition

Back

A response that does not involve any processing by the brain

Card 3

Front

What are the 3 neurones that most reflex pathways consist of?

Back

Preview of the front of card 3

Card 4

Front

What may a reflex be used for?

Back

Preview of the front of card 4

Card 5

Front

2 examples of a reflex action

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Plant and animal responses resources »