Chapter 8: The Nervous System And Movement

Question 1

• What is the nervous system?
• What is the 3 purposes of the nervous system?
• How are neurones different from other cells?
• Describe the 4 types of neurones according to the number of extensions from the soma.
• Describe the 3 types of neurones according to direction in which they send information.
• What are dendrites?
• What is an axon?
• What is the presynaptic terminal?

Answer 1

• A regulatory system which detects sensation, controls movement, physiological and intellectual functions.
• Receive info from receptors to detect changes in the body and the environment, process info and use effectors to carry out responses.
• They have extensions from the cell body and can transmit nerve impulses along its membrane.
  1. Bipolar: 2 extensions from the soma, 1 axon and 1 dentrite. Eg retina.
  2. Multipolar: multiple extensions from the soma, many dendrite and 1 axon. Found in brain.
  3. Unipolar: 1 extension from the soma, which branches off into a dendrite and a axon. Found in spinal cord.
  4. Anaxonic: many dendrites but no axon. Found in brain.
  1. Sensory (afferent): Sends messages from receptors to CNS.
  2. Motor (efferent): Sends messages from CNS to effectors.
  3. Interneurons: Joins sensory to motor neurons.
• Branches of soma which sends messages to the cell body.
• Long extensions of the soma which send messages away from the cell body.
• A structure at the ends of axon branches that forms junctions with another cell.

Question 2

• What is the 3 different types of receptors?
• What is ganglia?
• The PNS is divided into what 2 divisions?
• The efferent division can be further divided into what 2 divisions?
• The A.N.S can be further divided into what 2 divisions?
• What’s the difference between a somatic reflex and a somatic movement?
• What are muscle spindles?
• What spinal cord region is responsible for sensory and motor control of the arms and legs?
• Whats the 3 functions of the spinal cord?

Answer 2

1.Mechanoreceptors: senses pressure, stretching and movement.
2.Interoreceptors: sense hunger and pain.
3.Proprioreceptors: senses changes in the positions of the body.
-Groups of nerve cell bodies.
-Afferent division: Carries messages from receptors to CNS.
Efferent division: Carries messages from CNS to effectors.
-Somatic division: voluntarily carries messages to effectors.
Autonomic division: involuntarily carries messages to effectors.
-Sympathetic division: raises action of body.
Parasympathetic division: relaxes action of body.
-Somatic reflexes carry messages straight to the spinal cord rather than to the brain. Therefore movement can occur quicker.
-Sensory receptors in muscle. They provide info of amount of muscle tension, position and speed of muscle contraction.
-Cervical and lumbar respectively.
-Pathway for motor info going down from the brain, sensory info traveling up to the brain and coordination centre for reflexes.

Question 3

• What’s the difference between a monosynaptic and polysynaptic reflex?
• What is a motor unit?
• The size of motor units depends on what?
• What is the synaptic cleft?
• What is a chemical synapse?
• Describe an action potential?

Answer 3

• A monosynaptic is a reflex arc where one interneurone connect the sensory neurone to the motor neurone whereas a polysynaptic reflex has multiple Interneurons.
• The motor neurone and the muscle fibres it stimulates.
• Amount of control needed when a muscle is stimulated. Small motor units aren’t strong but precise eg muscles of eye. Large muscle units are strong but less precise eg quads.
• The synapse between a nerve fibre and target cell.
• A neurotransmitter like ACh providing the link to the next cell.
• A stimulus causes the cell body to release Na ions into the axon raising the resting potential to -55mV. This causes the Na channels to open and diffuses the Na ions out as there isn’t as much Na ions inside, and at the same time, raising the resting potential to +30mV and depolarising the cell. At this point there is too much K ions inside compared to outside, so the Na channels close and K channels opens, diffusing the K ions out. While the +ive K ions escapes, inside the membrane becomes less +ive, re-polarising the cell so rapidly that the cell hyper-polarises. Eventually the Na K pump returns the ions back to a level of -70mV.

Question 4

• What is the all or nothing law referencing muscle contraction.
• In muscle fibres, what happens once the certain level of electrical impulse is reached?
• Describe preferential recruitment.
• Describe the 2 types of motor unit recruitment.
• What type of training improves the function of the nervous system?
• When doing plyometrics what 2 things should be considered?
• What are the 3 main differences of the fast and slow fibres?
• Why is slow twitch fibres red?
• What is myosin-ATPase and what type of muscle fibre has more?
• Why is slow twitch fibres more efficient at using oxygen to generate ATP?

Answer 4

• The idea that muscle fibres will only contract if a certain level of electrical impulse is reached. They will contract at the same time and with same force. If it isn’t reached then no response.
• ATP stored in the fibres splits releasing energy and muscular contractions occur.
• If rapid and intense responses is required, white fibres will be recruited first. If a low intensity movement is required, red fibres are recruited.
• Synchronous is when all motor units fire at once for max force but fatigue quick and asynchronous when only some motor units fire delaying fatigue.
• Plyometrics
• Should specific to real movements and should be performed at maximal effort.
• Speed of contraction, endurance and force.
• They contain lots of myoglobin (O2 binding protein)
• An enzyme that speeds up the cross bridge action of the actin and myosin filaments. Fast twitch muscles have more of this.
• They’re highly vascularised and contains lots of mitochondria.

Question 5

• Explain 2 reasons why muscles are adapted to writing.
• Fast twitch fibres get most of their ATP from what process?
• Describe the 2 types of fast twitch fibres.
• Explain how strength and endurance training will affect the 2 types of muscle fibres.

Answer 5

• The muscles associated with writing are of slow twitch fibres so we can write continuously without fatigue and are supplied with small motor units for more precise control.
• Glycolysis: The breakdown of glycogen into lactic acid.
  1. Type 2a: AKA fast oxidative glycolitic as glucose and fats are broken down aerobically. They have greater resistance to fatigue.
  2. Type 2b: AKA fast-glycolitic and are only capable of anaerobic glycolitic metabolism. They have a lower resistance to fatigue so fatigue even quicker.
• Strength training leads to hypertrophy of fast twitch fibres and converting FOG to FG. Fibres will increase in size not increase number of fibres. Number of myofibrils increase. Overall result is increase in strength and speed of contractions

Endurance training: Converts FG to FOG. This training increases size of mitochondria, connection of oxidative enzymes and capillary density (improves O2 transport). Overall results to improvement in the ability to generate aerobic energy.

Question 6

• Demonstrate your knowledge of the following 5 parts of the nervous system by explaining their function to enable the actions of a cricket fielder
  1. Spinal cord
  2. Sensory neurones
  3. motor neurones
  4. brain
  5. motor unit

Answer 6

1. Dendrites of SENSORY NEURONES are stimulated by the sensory receptors in the eye and sends nerve impulses to the brain.
2. BRAIN interprets info and makes decision to ‘reach right arm out’ and sends nerve impulses down to the spinal cord.
3. SPINAL CORD receives info from brain and sends nerve impulses to the correct motor neurone.
4. MOTOR NEURONE sends nerve impulse from spine to effectors via motor units.
5. MOTOR UNITS stimulates muscles to contract to catch ball.