CHAPTER 3COORDINATION AND RESPONSE

3.1 Response and coordination Changes may occur around us or inside of our

body Organisms can detect the changes in the

environment and respond to the changes in certain ways

The external environment- physical & chemical conditions outside an organism and how these conditions affect it(light,sound,smell,etc..)

The internal environment- physical & chemical conditions of the tissue fluid surrounding the tissues of an organism(body temperature, osmotic pressure and blood glucose level)

The need for an organism to be sensitive

The internal environment must be constant for an organism to be healthy or survive

An organism cannot control its external environment, can control internal env. to a certain extent

Being able to respond enables an organism:

To regulate its internal environment Obtain and use resources, grow,

reproduce, and maintain stable internal conditions while living in a constantly changing external environment

Responses of humans, animals and plants to stimuli

Stimulus – changes in the external and internal environment

Receptor – detect the stimulus Afferent neurone – carries the nerve

impulse to the integrating centre(central nervous system) in the brain

Efferent neurone – carries the nerve impulse from brain to the effector

Effector – reacts to cause a response (muscles/glands)

Pathways of information due to external stimuli

Example: Sound of doorbell

Stimulus (sound

of doorbell)

Receptor in the ear

INTERGRATING

CENTRE/CNS(brain)

Effector (muscles in

hand)

Response(open the

door)

Pathway of information due to internal stimuli

Internal stimuli are detected by receptors sensitive to changes within the body

The endocrine system and nervous system control and coordinate functions in the body to maintain a constant internal environment through a negative feedback system

Negative feedback operates to counteract the change in the internal environment to restore it to normal

Body temperatureIntegrati

ng centre (brain) Effector

(skin and endocrine

glands)

Response (Activities to increase heat loss from body surface)

Normal body

temperature

Stimulus (high body temperatur

e)

Receptors in the skin

By negative feedback

Lowers body temperature

Rises due to excess heat

Changes in body temperature detected by

Coordination

Is the process involved in the detection of stimulus and the subsequent response of the organism towards the stimulus

Involve nervous system and endocrine system

3.2 Role of human nervous system

Role of nervous system:- Detect changes by receptors, process the

received sensory information and initiates the response

- Helps us think and act consciously- Stores information and allows us to learn from

past experiences- Adapts the body to changes in the environment- Controls and coordinates the activities of all

other systems in the body

Organisation of nervous system NS is made up of :1) Central nervous system [brain &

spinal cord]2) Peripheral nervous system [cranial

nerve & spinal nerve]

Central nervous system

Control centre of the body Consists of brain & spinal cord Processes sensory information, making

decision and initiating responses

Peripheral nervous system Is responsible for the communication

between the CNS and the rest of the body

Consists of all the nerves that branch out from the CNS and connects it to the rest of the body

Cranial nerves – nerves that carry impulses to and from the brain

Spinal nerves – nerves that carry impulses to and from the spinal cord

Structure and function of the brain Brain weighs about 1.4kg Consists of:1. Cerebrum2. Cerebellum3. Medulla oblongata4. Hypothalamus5. Thalamus6. Pituitary gland

1. Cerebrum

The largest region,divided into the right and left hemisphere

Each hemisphere has folds to increase the surface area

The left H. controls the right side of the body while the right H. controls the left side

Interprets information from receptors and controls movement of skeletal muscles in VOLUNTARY ACTION

Is the site of intelligence and carries out complex mental processes such as learning, remembering and making judgements

2. Cerebellum

2nd largest region Has two hemispheres Coordinates the contraction of the

muscles and helps control BALANCE to produce precise movements

3. Medulla oblongata

Relays information between the spinal cord and the brain

Controls INVOLUNTARY ACTIONS such as heartbeat, breathing and blood circulation

Control reflex centre for heart rate, blood pressure, blinking, sneezing, peristalsis, vomiting, swallowing

4. Thalamus

Receives information from all sensory receptors and then transmits it to the proper region of the cerebrum for further processing

5. Hypothalamus

Control centre for recognition and analysis of hunger,thirst,fatigue, anger and body temperature

Controls the coordination and the nervous system and endocrine system

6. Pituitary gland

Is attached to hypothalamus Connects the central nervous system

with the endocrine system Produce many important hormones

Spinal cord

Is the link between the brain and the peripheral NS

Consists of grey matter in the middle and white matter around it

Spinal nerves arise from spinal cord Each spinal nerve has a dorsal root

(contains afferent neuron) and ventral root (contains efferent neurone)

CONTROL REFLEX ACTION

Structure of a neurone