1. Coordination and Response in Plants and Animals
The Structure and Function of the Brain

2. Receptors, Effectors and the Central Nervous System
Syllabus Objectives
Describe the functions of the main region of the brain
Identify the main sense organs and the stimuli to which they respond

3. Introduction The brain and spinal cord
receive impulses and pass them on to effectors
The overall function of the brain is to
Coordinate and control the activities of the body
It controls all body functions except those under the control of simple spinal reflexes
Size: 1.5 kg
Protected by outer membranes, a layer of fluid and the bony skull

4. The Human Brain The brain is divided in 3 main parts Cerebrum
Cerebellum
Medulla / medulla oblongata

6. Cerebrum Largest part of the brain
Thin outer grey matter (3 mm deep) – cerebral cortex
Contains
deeply packed relay neurons
cell bodies of motor neurons
endings of sensory neurons

7. Cerebrum cont’d
The thick inner white matter is made up of nerve fibres (axon and dendrons)
The cortex is highly folded with deep grooves
One groove divides the cerebrum into right and left hemispheres
Folding increases the surface area of grey matter
More nerve cells and synapses allow more complex behavioural patterns

8. Cerebrum cont’d Control of all voluntary actions take place here
It is also the center of sensory awareness
Other things controlled here:
Memory
Reasoning
Judgment
Intelligence
Speech and language

9. Cerebrum summary The cortex is made up of
sensory areas, which receive impulses from receptors
motor areas where impulses going to effectors originate
Association areas that
Interpret
Integrate
Store information

10. Cerebellum Located beneath the posterior end of the cerebrum
Receives information from the ear and muscles about posture and balance
Controls
Walking
Running
(in birds it is large and controls flying)

11. Medulla/Medulla Oblongata
Located below the cerebellum and merges with the spinal cord
Controls many unconscious processes/involuntary actions
Regulation of body temperature
Blood pressure
Breathing
Heart rate
Swallowing
Vomiting
Coughing
Yawning

12. Medulla/Medulla Oblongata cont’d
It controls the autonomic nervous system which regulates internal activities of which the individual is not aware
e.g.
activities of the sweat glands,
muscles in the gut,
blood vessels and heart,
reproductive tract receives motor fibres from the autonomic nervous system (ANS)

13. Autonomic Nervous System (ANS)
Made up of 2 parts
Sympathetic nervous system
Parasympathetic nervous system
Most internal organs receive fibres from both systems
Their actions are antagonistic
Sympathetic stimulation causes an increase in heart rate; parasympathetic stimulation causes a decrease in heart rate

14. Hypothalamus Situated underneath the front part of the cerebrum.
It is the main control center for the ANS
Centers in the hypothalamus regulates the body activities concerned with homeostasis
It also controls the release of hormones from the pituitary gland

15. Homeostasis
Various processes that operate within an organism to maintain a constant internal environment
Information on the state of a particular internal factor is sent to the hypothalamus
When a change from the norm occurs mechanisms are put in place to oppose the change – negative feedback
Homeostatic responses are either through nervous system, actions of hormones or both