Answers and tips
(1) Discussion of problems
If your finger is pricked by a sharp prick on the plant, you quickly retract your hand, then feel the pain, and then you realize that your hand is pricked.
discuss:
1. How does this process occur? Which structures of the nervous system are involved?
Answer: The fingers are punctured, the receptors in the skin are stimulated, and the resulting excitement is transmitted to the center of the spinal cord, and the central response is transmitted to the muscles of the upper limbs through the efferent nerves, and the coordinated contraction and relaxation of the muscles cause the hand to retract. At the same time, the spinal cord sends signals to the cerebral cortex, creating a feeling of pain and realizing that the hand is pierced.
2. What is the significance of adapting to the hand reduction movement in front and feeling the pain in the back?
Answer: Shrinking your hand in front of you can make the body quickly avoid harmful stimuli and avoid damage to the body. After the generation of feelings, it helps the body to judge and identify the advantages and disadvantages of the stimulus, and can make the body more flexible and predictable to respond to environmental changes, so as to better adapt to the environment.
(2) Thinking and discussing
1. Can a complete reflex activity be done by a single neuron?
Answer: No. Complete reflex activity requires at least two types of neurons, afferent and efferent. In most cases, the involvement of interneurons is also required
2. What are the components of the reflex arc of the hand reduction reflex and the knee jump reflex?
Answer: They are all composed of receptors, afferent nerves, nerve centers, efferent nerves and effectors.
3. Combined with life experience, can you give other examples of the role of the spinal cord in reflexes?
Answer: For example, the lower center of the urinary reflex is in the spinal cord.
(3) Practice and application
Concept detection
1. The reflective arc is the structural basis of reflection. Determine whether the following relevant statements are correct.
(1) The reflex arc is composed of neurons. (×)
(2) All organisms can respond to stimuli and therefore have reflexive activity. (×)
(3) As long as the structure of the reflective arc is intact and appropriate stimulation is given, reflex activity can occur. (×)
2. If the afferent nerve and nerve center innervated in the left leg are intact and the efferent nerve is damaged, then the left leg (c)
a. Can move, acupuncture has a feeling
b. Can move, acupuncture does not feel
c. Inability to move, acupuncture has a feeling
d. Inability to move, no sensation of acupuncture
3. There are non-reflexes and conditioned reflexes, and the following description of them is wrong (d)
a. Both help the animal adapt to the environment
b. Conditioned reflexes are based on unconditioned reflexes
c. Conditioned reflexes can be resolved, and unconditioned reflexes are generally permanent
d. The formation of both conditioned and unconditioned reflexes requires the participation of the cerebral cortex
Expand your applications
1. Scientists use frogs that remove the brain but retain the spinal cord (called spinal frogs) as a material for reflex activity experiments, please answer questions related to this.
(1) Gently stimulate the toes of the left hind limb of the ridge frog, and the flexion leg reflex can be observed in the hind limb. The reflection arc composition of the reflection is.
(2) After destroying the spinal cord with a needle, the toe of the left hind limb of the frog is stimulated, and the hind limb undergoes a leg flexion reflex; if the stimulation is an efferent nerve, the hind limb undergoes a leg flexion reflex (filled in "can" or "can not").
(3) From this experiment you can draw the conclusion that it is.
(4) From the above experimental results, the conclusion that "the flexion reflex of the frog's hind limbs is not controlled by the brain" (fill in "can" or "can't").
Answer: (1) Receptors (toe skin), afferent nerves, nerve centers (located in the spinal cord), efferent nerves, effectors (hindlimb muscles).
(2) Can not no (can complete the leg flexion reaction, but lack of a complete link of the reflex arc, without the participation of the central nervous system, does not constitute a reflex).
(3) The reflex needs to go through a complete reflex arc, and without the nerve center, the reflex cannot be completed.
(4) No. (Tip The experiment did not reflect the brain's control of the leg flexion reflex, but only showed that the leg flexion reflex can still be done without a brain.) ）
2. If you have a cat or dog at home and want it to defecate in a fixed place, how do you train it?
Answer: Through rewards or punishments, cats and dogs can establish a conditioned reflex of urinating and defecating at a fixed point. For example, when a cat or dog is about to defecate, it is transferred to a fixed place to defecate, and a certain reward is given after the defecation is completed; if it is free to defecate, a certain punishment is given. Repeat several times until the conditioned reflex is established.