Chapter 11B Nervous System

Question 1

Describe the similarities and differences between a voluntary action and a reflex action [4] (2012/B10 E)

Answer 1

Similarities:
‐ Both voluntary and reflex actions involve the central nervous systems. [1]
‐ Both voluntary and reflex actions involve the relay and motor neurone. [1]
- Both involve the transmission of nerve impulses.[1]
Differences:
‐ A voluntary action is initiated at the brain and does not involve the sensory neurone while a reflex action is initiated at the receptors and involves the sensory neurone [1].
‐A stimulus is necessary to initiate the reflex action while a voluntary action may be initiated in the absence of a stimulus.[1]
- Voluntary action is under conscious control but reflex action is not under conscious control [1]
- A reflex action is almost immediate while a voluntary action will have a longer reaction time.

Question 2

Describe the pathway of nerve impulses in a named reflex action (2012/B10 E)

Answer 2

1. When a person touches a hot object with his hands, the receptors in the skin detect the change/stimulus [1] and
2. initiate nerve impulses that are sent along the sensory neurone into the spinal cord.[1]
3. The nerve impulses reach the end of the sensory neurone and cross the synapse to the relay neurone [1].
4. Nerve impulses then travel along the relay neurone until it reaches the end, where it crosses the second synapse to the motor neurone [1]
5. Nerve impulse travels along the motor neurone to the effector [1].
   The effector, in this case, is the arm muscles, which will contract, causing the arm to pull back to prevent injury [1]
   +. At the same time, a relay neurone from the spinal cord will also transmit nerve impulses to the brain to bring about the pain sensation.

Question 3

State the relationship between receptors, the central nervous system and the effectors

Answer 3

1. Receptors or sense organs detect a stimulus and are stimulated, generating nerve impulses.
2. Sensory neurones transmit nerve impulses to the relay neurone in the central nervous system (CNS) which consists of the brain/spinal cord.
3. Before transmitting nerve impulses along the motor neurone to the effector (muscles/ glands) to carry out the response.

Question 4

what does the central nervous system consist of and what type of neurons does it made of?

Answer 4

The central nervous system consists of the brain and the spinal cord, which are made up of relay neurons

Question 5

What does the peripheral nervous system consist of and what type of neurons does it made of?

Answer 5

The peripheral nervous system consists of cranial, spinal and peripheral nerves, which are made up of motor and sensory neurons

Question 6

_____ __ _______ (a.k.a. ___________)are regions where the myelin sheath is absent. they speed up transmissions by allowing nerve impulses to jump from node to node.

Answer 6

Nodes of Ranvier, Neurofibril

Question 7

The _____ ___ _____ is the junction between the neuron and the muscle fibre

Answer 7

Motor End plate

Question 8

What is a synapse?

Answer 8

A junction or connection between two neurones (from an axon to a dendron) whereby a nueral signal us transmitted by chemical means through neurotransmitters

Question 9

what is a reflex action?

Answer 9

A reflex action is an immediate involuntary response to a specific stimulus without conscious control.

Question 10

What is a Reflex arc? (self)

Answer 10

The reflex arc is the shortest pathway by which nerve impulses are transmitted from the receptor to the effector. The nerve impulses generated by the receptor are transmitted along the reflex arc.

Question 11

Describe the knee-jerk reaction [3] (self)

Answer 11

1. Tap stimulates the tendon under
   the kneecap.
2. Nerve impulses are generated
   and transmitted along the sensory neurone to the spinal cord and across a synapse to the motor neurone and to the effector (no relay neurone involved).
3. The effector is the thigh muscles which contract, bringing about a sudden kicking of the legs.

Question 12

Explain an example of a voluntary action (holding a hot pan) (self)

Answer 12

Nerve impulses are initiated and generated in the brain.
1. Transmitted via the relay neurone to the spinal cord
2. Across a synapse to the motor neurone and to the effector which is the arm muscles.
3. Arm muscles contract and the hand is withdrawn.