ANSWERS

1. List the functions of the nervous system.
   • To receive information from the external environment.
   • To receive information from the tissues and organs of the animal.
   • Interpretation of the information received from both environment and animal.
   • To send nervous impulses throughout the body of the animal in order to stimulate action.
   • As a whole, the nervous system functions to control bodily functions and respond to the demands of the environment in a co-ordinated fashion.
2. The nervous system comprises 2 parts; can you name them?
   • The central nervous system (CNS) - comprising the brain and spinal cord.
   • The peripheral nervous system - comprising all the other motor and sensory nerves throughout the body.
3. What is the collective name for nerve cells?
   Neurons.
4. What is the name of the connective tissue that runs between the neurons?
   Neuroglia.
5. List the components of a nerve cell.
   • Cell body with nucleus.
   • Dendrites - which allow nervous impulses to enter the cell.
   • Axon - along which the nerve impulse travels.
   • Neurilemma - a sheath of connective tissue surrounding the axon.
   • Nodes of Ranvier - which take in nutrients and oxygen from the surrounding tissues.
   • Nerve endings - which transmit the nervous impulse to the dendrites of the next axon.
6. Some axons are surrounded by a myelin sheath. What is the function of this?
   This fatty substance allows nervous impulses to travel more rapidly.
7. Name the cells which produce myelin.
   Schwann cells.
8. What is meant by the following: unipolar, bipolar and multipolar?
   • Unipolar - a neuron having a connection with only one cell.
   • Bipolar - a neuron having connections with 2 cells.
   • Multipolar - a neuron having connections with many cells.
9. Briefly describe the structure and function of a nerve.
   Many neurons (see Q5) bound together in a connective tissue sheath. Each nerve carries information as an electrical impulse.
10. What is a synapse?
    The termination of an axon with the dendrites of another neuron. Chemical transmitters pass the impulse across the space.
    An impulse can only pass in one direction across a synapse.
11. What is the name given to a collection of neurons and fibres, forming an independent nerve centre, as is found in the sympathetic nervous system?
    A ganglion.
12. What name is given to the organ, muscle or gland where the nerve endings terminate?
    The effector organ/muscle/gland.
13. What is the difference between afferent and efferent nerve fibres?
    Afferent fibres carry sensory information towards the CNS (motor nerve fibres), whilst efferent fibres carry signals away from the CNS (sensory nerve fibres).
14. What is the difference between a somatic motor nerve and a visceral motor nerve?
    A somatic motor nerve takes instructions to the voluntary muscle, whilst a visceral motor nerve takes instructions to the involuntary (smooth or cardiac) muscle.
15. What is the name of a junction between a nerve fibre and a muscle fibre?
    A neuro-muscular junction.
16. Name 2 factors that may cause varying effects on the nervous system.
    • The number of nerve fibres involved.
    • Some of the neurons may be inhibitory rather than stimulatory.
17. What is a reflex arc? Can you give an example?
    A fixed, involuntary reaction to a stimulus as a result of a combination of automatic responses to spinal reflexes. An example is the rapid withdrawal of a paw from a sharp thorn.
18. Explain in 4 steps how a spinal reflex arc works.
    • Pain or heat receptors initiate an impulse in the sensory nerve.
    • The impulse travels up the nerve and enters the spinal cord through the dorsal root of the nerve.
    • An impulse is initiated in the motor nerve and leaves the spinal cord in the ventral root; the relevant muscles are instructed to respond.
    • Information regarding this assault is meanwhile passed to the CNS.
19. What is the name of the extra nerve cell that is often present between a sensory and motor neuron?
    An interneuron.
20. What is the difference between a conditional and an unconditional reflex?
    A conditional reflex may be overcome by a conscious decision, however an unconditional reflex cannot generally be over-ruled (although sometimes they can with practice!).
21. Explain how the brain is divided.
    • Forebrain - comprising the cerebrum (or central hemispheres), the thalamus and the hypothalamus.
    • The midbrain.
    • The hindbrain - comprising the pons, medulla oblongata and the cerebellum.
22. What is the name of the deep groove that divides the hemispheres of the brain?
    The longitudinal sulcus.
23. What are the functions of the following: cerebrum, thalamus and hypothalamus?
    • Cerebrum - receives and processes information from all over the body.
    • Thalamus - relays information to and from the cerebral cortex.
    • Hypothalamus - helps to regulate the autonomic nervous system and pituitary gland.
24. What are the functions of the midbrain?
    • Passes on impulses from the hindbrain.
    • Passes on impulses from the senses of vision and hearing to the forebrain.
25. Which part of the hindbrain contains centres that control the heart and respiration?
    The medulla oblongata.
26. What is the function of the cerebellum?
    The co-ordination of muscular activity.
27. How many ventricles does the brain possess?
    4.
28. What is contained within the ventricles of the brain?
    Cerebrospinal fluid (CSF).
29. In addition to the ventricles of the brain, where else would you find CSF?
    • The spinal canal.
    • The subarachnoid space.
30. What is the name of the structures within the ventricles of the brain which secrete CSF?
    Choroid plexuses.
31. What is the function of CSF?
    To cushion and protect the brain against sudden movement or trauma.
32. State the site from which a CSF sample for diagnostic purposes would be obtained.
    • The cisterna magna (cerebromedullary cistern).
    • This is located between the cerebellum and medulla and is reached via the atlanto-occipital space.
33. What is the collective name of the 3 layers of membrane that cover and protect the brain?
    The meninges.
34. Name the 3 meninges and describe the location of each.
    • Dura mater - composed of 2 layers which line the cranial cavity of the skull.
    • Arachnoid layer - closely attached to the inner layer of the dura.
    • Pia mater - closely attached to the brain.
35. What is the name of the group of nerves sited at the termination of the spinal cord?
    The cauda equina.
36. The nerve on each side of the spinal cord is split into 2 roots. State the function of each.
    • Dorsal root - carries sensory fibres into the spinal cord.
    • Ventral root - carries motor fibres away from the spinal cord.
37. Why are the spinal nerves at their thickest at the levels of the pectoral and pelvic girdles?
    The spinal nerves located here supply the limbs in addition to the trunk.
38. What is the exception to the rule that states that the spinal nerves are named according to the vertebra in front of where they leave the CNS?
    The cervical region since there is an 8th cervical nerve (and only 7 cervical vertebrae) which lies behind the 7th cervical nerve.
39. State the nerves which supply the forelimb and hindlimb.
    • Forelimb - Spinal nerves Ce6 to T2.
    • Hindlimb - Spinal nerves L4 to S2.
40. What is the collective name of the nerves that end or originate within the brain? How many of them are there?
    The 12 cranial nerves.
41. List the cranial nerves.
    • I - Olfactory.
    • II - Optic.
    • III - Oculomotor.
    • IV - Trochlear.
    • V - Trigemenal.
    • VI - Abducens.
    • VII - Facial.
    • VIII - Vestibulocochlear (auditory).
    • IX - Glossopharyngeal.
    • X - Vagus.
    • XI - Accessory.
    • XII - Hypoglossal.
42. Which of the cranial nerves are purely sensory?
    • I - Olfactory.
    • II - Optic.
    • VIII - Vestibulocochlear.
43. Which of the cranial nerves supply motor fibres to the muscles of the eye?
    • III - Oculomotor.
    • IV - Trochlear.
    • VI - Abducens.
44. Which of the cranial nerves is sensory to the skin of the face and motor to the jaw muscles?
    V - Trigemenal.
45. Which of the cranial nerves is motor to the muscles of facial expression?
    VII - Facial.
46. Which of the cranial nerves carries sensory fibres from the tongue and motor fibres to the pharynx?
    IX - Glossopharyngeal.
47. What parts of the anatomy are served by the motor fibres of the vagus nerve?
    The larynx and the thoracic & abdominal viscera (through the gastrointestinal tract down to the colon).
48. Which cranial nerve carries motor fibres to the muscles of the neck?
    XI - Accessory.
49. Which cranial nerve carries motor fibres to the tongue?
    XII - Glossopharyngeal.
50. What is the name given to the visceral motor system of the body which supplies motor nerves to the internal organs and blood vessels (not under voluntary control)?
    The autonomic nervous system.
51. The autonomic nervous system is divided into 2 parts. Can you name them?
    • The sympathetic nervous system.
    • The parasympathetic nervous system.
52. List 6 responses initiated by the sympathetic nervous system which help the body to respond to stressful situations.
    • Increased heart rate.
    • Increased respiratory rate.
    • Dilation of bronchi and bronchioles thus increasing the diameter of the airway.
    • Slower bowel movement & constriction of blood vessels supplying the bowel.
    • Cessation of the secretion of digestive juices.
    • Increased blood supply to skeletal muscles.
    • The parasympathetic system dominates when the animal is relaxed and not fearful.
53. Where do the sympathetic fibres leave the spinal cord?
    Nerves T1 to L4/5.
54. Where do the parasympathetic fibres leave the CNS?
    Cranial nerves III, VII, IX & X.