Ch 17 Divisions of the Nervous System and Neural Pathways

Question 1

What is the central nervous system?

Answer 1

The body’s information processing centre.

Question 2

What does the central nervous system do?

Answer 2

The nervous system gathers and analyses
sensory information from the body and the
external environment.

It consists of billions of neurones throughout the body and uses electrical impulses (signals) to communicate information very quickly between neural receptors, the brain via motor pathways to effectors (e.g. muscles and glands).

Some of the information is stored and
decisions are made to ensure appropriate
response and behaviour.

Motor responses are brought about which
either initiate muscular contractions or
glandular secretions.

Question 3

What are neurones?

Answer 3

Neurones are cells responsible for receiving
sensory input from internal and external environment/stimuli and for transforming and relaying the electrical impulses at every step in between (e.g. sending motor commands to muscles to effect movement).

There are approx. 86 billion neurones in your brain alone.

Question 4

What are the functional divisions of the peripheral nervous system?

Answer 4

Peripheral nervous system >

• Somatic nervous system (mostly voluntary movement)
• Autonomic nervous system ANS (involuntary movements) > Sympathetic system
  > Parasympathetic system

Question 5

Sympathetic and parasympathetic systems are antagonistic in action. What does this mean?

Answer 5

They affect many of the same structures but exert opposite effects on them.

Question 6

What movements does the SNS (somatic nervous system) control?

Answer 6

The SNS controls VOLUNTARY movement of skeletal muscles (with a few exceptions)

Question 7

What movements does the ANS (autonomic nervous system) control?

Answer 7

The ANS controls the INVOLUNTARY movement of
skeletal muscles (e.g. cardiac muscle and smooth muscle) and glandular secretions (e.g.
adrenalin and insulin).

Question 8

Somatic nerve pathway

Answer 8

Receptors (eg sense organs) >
> sensory nerves
> CNS
> motor nerves
> effectors (eg muscles and glands)

Question 9

What are the autonomic nervous system responses?

Answer 9

Sympathetic response - fight or flight
Parasympathetic response - rest and digest

Question 10

What is the effect of actions of the sympathetic and parasympathetic system on heart rate?

Answer 10

Sympathetic:
Increased contraction of cardiac muscles - increases cardiac output (the product of heart rate (HR) and stroke volume (SV) measured in liters per minute).

Parasympathetic:
Decreased contraction of cardiac muscles - decreases cardiac output.

Question 11

What is the effect of actions of the sympathetic and parasympathetic system on breathing rate?

Answer 11

Sympathetic:
Smooth muscle wall of bronchioles relaxed- increased
intake of air.

Parasympathetic:
Smooth muscle wall of bronchioles contracted
decreased intake of air.

Question 12

What is the effect of actions of the sympathetic and parasympathetic system on peristalsis?

Answer 12

Sympathetic:
Rate of contraction of smooth muscle in digestive decreased - decreases rate of peristalsis.

Parasympathetic:
Rate of contraction of smooth muscle in digestive tract increased - increased rate of peristalsis.

Question 13

What is the effect of actions of the sympathetic and parasympathetic system on intestinal secretions?

Answer 13

Sympathetic:
Activity of the secretory glands inhibited – decreased
production of intestinal secretions.

Parasympathetic:
Activity of the secretory glands stimulated –increased production of intestinal secretions.

Question 14

Somatic nervous system summary

Answer 14

• Controls the body’s skeletal muscles.
• Involves both motor and sensory nerves
• It also controls certain involuntary reflex actions (eg.
  limb withdrawl) BUT its main function is to control
  voluntary movements of skeletal muscles.
• Sensory neurones carry impulses into the CNS from
  the sense receptors.
• Motor neurones carry impulses out of the CNS along
  the motor pathways to muscles and glands (eg
  cardiac and skeletal muscle).

Question 15

Autonomic nervous system summary

Answer 15

• Works automatically, without conscious thought.
• Associated impulses originate in the medulla in the
  brain.
• It regulates the body’s internal environment and vital
  processes (e.g. heartbeat, blood pressure, breathing).
• It is made up of two systems: sympathetic and
  parasympathetic.
• These two systems are antagonistic in action.
• The sympathetic system prepares the body for fight
  or flight.
• The parasympathetic system prepares the body for
  rest and digest.

Question 16

Peripheral nervous system summary

Answer 16

• The sensory and motor neurones of the somatic
  nervous system (SNS) control the voluntary
  movement of skeletal muscles.
• The autonomic nervous system (ANS) conduct
  involuntary impulses to smooth muscle, cardiac
  muscle and glands through sensory neurones and
  motor neurones.
• The antagonistic action of the sympathetic ‘fight or
  flight’ and parasympathetic ‘rest and digest’ have an
  effect on heart rate, breathing rate, peristalsis and
  intestinal secretions.

Question 17

The autonomic nervous system is responsible for maintaining homeostasis within the body. What is the importance of this?

Answer 17

It keeps the body’s internal environment within a stable state. This self-regulating process allows biological
systems to maintain a balance of tolerable limits and
continue to function whilst adjusting to a change in external conditions (or changes in the body’s rate of activity).

Question 18

Explain negative feedback control in the nervous system.

Answer 18

When the body’s internal environment deviates from its normal, optimum set of parameters (aka the ‘norm’ or ‘set point’), these changes are detected by receptors. The receptors send this information to effectors via nerve impulses and hormones, which results in corrective action being taken to counteract the original
deviation. Thereby, returning the body’s system to its set point, or normal state. This action is referred to as NEGATIVE FEEDBACK CONTROL.