Unit 3: Behaviour, Populations and

environment

Chapter 26: Organisation of the nervous system

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Higher Human Biology

Learning Intentions

To examine the workings of the brain and the nervous system.

Success Criteria2. Define the terms;

a.Central nervous system

b.Peripheral nervous system

c. Somatic nervous system

d.Autonomic nervous system

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The Nervous The Nervous SystemSystem

Image source: www.drstandley.com

The nervous system is a network of specialised cells that communicate information about an

individual’s surroundings and itself.

It processes this information and causes

reactions in other parts of the body.

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Summary: The Nervous System

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CNS (central nervous system)

PNS (peripheral nervous

system)

Structural Division: The Nervous SystemStructural Division: The Nervous System

Based on the structure and location of the component parts, the nervous system can be divided as shown in the diagram.

Brain Spinal Cord

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Central Nervous System

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Peripheral Nervous System

• Somatic – some involuntary reflex actions, mostly voluntary actions

• Autonomic - involuntary actions

Autonomic (involuntary - muscles)

PNS (peripheral nervous system)Crainial nerves + spinal nerves)

Somatic (mostly voluntary)

Functional Division: The Nervous Functional Division: The Nervous SystemSystem

ParasympatheticSympathetic

ANTAGONISTIC have opposite effects

A further method of dividing up the nervous system is

based on different functions performed by the two

separate branches of the peripheral nervous system as

shown in the diagram 21/04/23 7Mrs Smith Ch26 The Nervous

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The Somatic Nervous SystemThe Somatic Nervous SystemThe peripheral nervous system has 2 branches, called the somatic and the autonomic nervous systems.

The somatic nervous system (including spinal nerves) controls the skeletal muscles. Most movements that it controls are voluntary but it also controls certain involuntary reflex actions (e.g. limb withdrawal).

SENSORY NERVE

C.N.S MOTORNERVE

Brain & Spinal cord - processes informatio

n.

STIMULUS RESPONSE

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The autonomic nervous system (ANS) controls involuntary responses to stimuli by the body, so there is no conscious control, but under exceptional some people can suppress certain autonomic responses intentionally.

The Autonomic Nervous The Autonomic Nervous SystemSystem

The nerves start at the nerve cells in the brain, pass down the spinal cord then emerge at the appropriate

organ.

Autonomic nerves regulates the heart, blood vessels, bronchial tubes, alimentary canal & sweat glands.

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Autonomic Nervous System

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Antagonistic nature of the Autonomic Nervous System

• The sympathetic and parasympathetic systems which make up the autonomic nervous system are described as being antagonistic.

• i.e. They affect many of the same body structures but exert opposite effects on them.

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Image source: www.biocomtech.com

Parasympathetic v SympatheticParasympathetic v SympatheticHomeostasis Response to stressANTAGONISTIC have

opposite effects

•Tries to maintain a stable internal environment

• ‘Flight or flight’ response

Adrenal gland only connected

to sympatheti

c nerves

• Calms the body down after stress

• Helps body conserve resources & store energy

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Harmonious Balance

• The autonomic nervous system is concerned with maintaining a stable internal environment by playing a part in homeostasis.

• The sympathetic and parasympathetic nervous systems are constantly working in an opposite but equal manner (neither wins).

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Fight or flight

In response to a crisis the sympathetic system prepares the body for action and the expenditure of energy by•Increasing heart rate and blood pressure.•Diverting blood to skeletal muscle.•Increasing perspiration.

The hormone ADRENALINE helps to sustain this state till the emergency is over.

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Calming DownWhen the crisis is over, the parasympathetic system briefly takes over by;•Returning heart rate and blood pressure to normal.•Peristalsis in the digestive tract increases.•Blood is diverted away from skeltal muscles and back to the intestine (allowing digestion to resume).

THIS ALLOWS THE BODY TO STORE ENERGY AND CONSERVE RESOURCES.

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Task: Torrance-TYK pg 215 Qu’s 1-4

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Task: Torrance AYK pg215/216 Qu’s 1-4

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