This document discusses coordination and response in organisms. It describes how organisms detect changes in their external and internal environments using receptors, and respond through neural and endocrine pathways. The nervous system plays a key role in coordination, with the central nervous system processing sensory information and initiating responses via the peripheral nervous system. This allows organisms to maintain stable internal conditions while living in a changing external environment.

1. CHAPTER 3
COORDINATION AND
RESPONSE

2. 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)

3. 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

4. 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

5. 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)

6. 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)

7. 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

8. Body temperature
Integratin
g centre
(brain)
Effector
(skin and
endocrine
glands)
Response
(Activities to
increase
heat loss
from body
surface)
Normal body
temperature
Stimulus
(high body
temperature)
Receptors
in the skin
By negative
feedback
Lowers body
temperature
Rises due to
excess heat
Changes in body
temperature detected
by

9. 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

10. 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

11. Organisation of nervous
system
 NS is made up of :
1) Central nervous system [brain & spinal
cord]
2) Peripheral nervous system [cranial nerve &
spinal nerve]

12. Central nervous system
 Control centre of the body
 Consists of brain & spinal cord
 Processes sensory information, making
decision and initiating responses

13. 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

14. Structure and function of the
brain
 Brain weighs about 1.4kg
 Consists of:
1. Cerebrum
2. Cerebellum
3. Medulla oblongata
4. Hypothalamus
5. Thalamus
6. Pituitary gland

15. 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

16. 2. Cerebellum
 2nd largest region
 Has two hemispheres
 Coordinates the contraction of the muscles
and helps control BALANCE to produce
precise movements

17. 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

18. 4. Thalamus
 Receives information from all sensory
receptors and then transmits it to the proper
region of the cerebrum for further processing

19. 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

20. 6. Pituitary gland
 Is attached to hypothalamus
 Connects the central nervous system with the
endocrine system
 Produce many important hormones

21. 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

23. Structure of a neurone