Download The human nervous system

The human nervous system
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Learning Activity 1
Review questions: suggested answers
1 The peripheral nervous system is the entire network of nerves outside the central nervous
system (brain and spinal cord).
2 The two main functions of the PNS are to carry information from the sensory organs and
internal organs to the CNS; and to carry information from the CNS to the muscles, organs
and glands.
3 The CNS and PNS are interdependent. For example, you may sense (via sensory receptors in
your fingertips) that the cup of coffee you are holding is too hot for your fingers. The neural
message is sent from the sensory neurons in the fingers (part of the PNS) to the CNS. The
brain organises the message, deciding that the cup is too hot to hold and sends messages
via motor neurons (PNS) to the muscles of the hand to put the cup down.
Learning Activity 3
Review questions: suggested answers
1 a The main functions of the somatic nervous system are to carry sensory messages from
sensory receptors to the CNS and to carry motor messages from the CNS to control
voluntary movements of the skeletal muscles.
b For example, the sensory receptors in your skin may detect that the heat from the sun
entering the car is too hot. Messages are sent to the CNS and the brain responds with
motor messages to move the arm away from the direct heat or to cover the arm to prevent
burning.
2 Writing an answer to a question begins with the planned response. The brain sends
messages via motor neurons to the hand and arm to begin writing. There is visual sensory
information and tactile information from the writing hand as you write and these sensory
messages are sent to the brain. The brain continues to receive sensory messages from the
hand and eyes and to send motor messages to the skeletal muscles regarding the writing
process, until it is completed.
Learning Activity 5
Review questions: suggested answers
1 a The Autonomic Nervous System (ANS) is called autonomous because many of the organs,
glands and processes under its control are self-regulating and not voluntarily controlled.
They generally function independently of the brain.
b It is not really autonomous, as the CNS plays a role in increasing or decreasing the
processes governed autonomically in order to meet the body’s demand. Furthermore,
there are some autonomic processes over which we can take some control. These include
heart rate, blinking and breathing rate.
2 The autonomic nervous system controls breathing rate without our voluntary participation.
But if we wanted to slow our breathing rate (say, to relax or meditate), the CNS is able to
send messages to the muscles involved in breathing, and we can consciously slow down the
rate; that is, we exert voluntary control over a normally involuntary process.
© Macmillan Education Australia 2005. Unauthorised copying prohibited.
Psychology VCE Units 3 & 4
The human nervous system
© Macmillan Education Australia 2005. Unauthorised copying prohibited.
3 Skeletal muscles are part of the somatic nervous system and in the absence of motor
messages from the brain they remain inactive. Visceral muscles, on the other hand, are part
of the Autonomic Nervous System and have in-built mechanisms for generating activity in
order to keep the body functioning smoothly.
4 Because of its role in keeping the vital organs and bodily systems functioning, the ANS
has a greater role in our survival than the CNS. For example, when we are asleep or even
anaesthetised, we must still breathe, and our heart must still pump blood to the body.
The ANS controls these functions, without input from the CNS.
Learning Activity 7
Review questions: suggested answers
1 The main difference between the sympathetic and parasympathetic nervous systems is that
the sympathetic nervous system is responsible for increasing the activity of visceral muscles,
organs and glands, while the parasympathetic nervous system is responsible for decreasing
those functions and for keeping the body in its ‘normal’ state.
2 a The sympathetic nervous system activates internal muscles, organs and glands, to prepare
the body to deal with a stressful or threatening situation. By doing so, it enhances survival.
b As a result of the action of the sympathetic nervous system, heart rate increases, as does
breathing rate and blood pressure.
c As a result of the action of the sympathetic nervous system, salivation decreases as does
stomach contractions and the release of bile from the bile duct (all involved in digestion).
3 a The parasympathetic nervous system keeps the body systems functioning efficiently and
in the absence of threats it maintains the balanced (homeostatic) state of normal bodily
functioning. It also restores the body to a state of calm after the sympathetic nervous
system has been active.
b As a result of the action of the parasympathetic nervous system, heart rate slows,
perspiration production decreases and breathing rate decreases—all of these return the
body to equilibrium after a threatening event. The action of the sympathetic nervous
system to arouse the body to deal with threat is counteracted and calmed by the
parasympathetic nervous system.
4 As a result of the action of the sympathetic nervous system, hormones are released into the
body to enable it to deal with the threat. These remain in the system for some time after the
threat has passed and so it can take some time for the parasympathetic nervous system to
‘slow down’ bodily functions.
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