Lesson 1: Introduction

Question 1

The Nervous System

Answer 1

Two major divisions of the
human nervous system are the
Central Nervous System (CNS)
and the Peripheral Nervous
System (PNS)

Question 2

Central Nervous
System

Answer 2

Made up of the brain and spinal cord the CNS receives sensory information and initiates motor control.

Protected by bone (the skull for the brain and the vertebrae for the spinal cord) and surrounded by a protective membrane called the meninges.

The space between the meninges is filled with cerebrospinal fluid to further protect the CNS from impact.

The spinal cord is the vehicle of communication between the brain and the PNS.

In cross – section, the spinal cord contains a central canal (which is filled with cerebrospinal fluid), grey matter and white matter.

Grey matter contains a
concentration of cell bodies and interneurons associated with reflex action.

White matter contains bundles of axons that run between the CNS and PNS.

Question 3

Peripheral Nervous
System

Answer 3

The PNS consists of 2 parts:

1. Autonomic Nervous
   System
2. Somatic Nervous
   System

Question 4

Autonomic Nervous System

Answer 4

The autonomic nervous system is not consciously controlled and is made up of the sympathetic and parasympathetic nervous systems.

Question 5

Sympathetic Nervous System

Answer 5

The sympathetic nervous system sets off the “fight or flight” reaction that prepares
the body to deal with an immediate threat.

When this system is stimulated, heart rate and breathing rate increase and sugar is released from the liver to provide energy.

Question 6

Parasympathetic Nervous System

Answer 6

The parasympathetic nervous system has the opposite effect of the sympathetic
nervous system.

When a threat has passed, the nerves of this system slow heart rate and breathing
rate and reverse the effects of the sympathetic nervous response.

Question 7

Somatic Nervous System

Answer 7

The somatic nervous system is made up of sensory nerves that carry impulses from
the body’s sense organs to the CNS and motor nerves that carry impulses from the
CNS to the muscles.

The somatic nervous system is under some conscious control.

The information from your eyes and ears is processed by the brain and correlated
with information you already have to make a decision that may or may not involve
the movement of muscles.

Decision making can be time consuming, so in some cases the system is designed to
so that certain actions set off specific reactions. This is known as a reflex.

Reflexes do not require a conscious decision.

Question 8

Steps of the Reflex Arc

Answer 8

1. A strong stimulus (heat, pain etc.) triggers nerve endings in the skin. These
   are the dendrites of sensory neurons.
2. The impulse travels along this neuron into the spinal cord.
3. In the spinal cord the signal is passed to interneurons which serve as a link
   between sensory and motor neurons.
4. The signal stimulates a motor neuron which transmits an impulse along its
   axon which triggers the action of the effector (muscle or gland).