Learning Objectives
• Identify the main structures of the brain
(cerebrum, cerebellum, medulla and
hypothalamus) and state their
functions
Structure of the Brain
• There are four main areas in the brain: – the cerebrum which controls memory,
personality and conscious thought
– the cerebellum which controls balance and co-ordination of movement
– the medulla which controls heart rate and breathing rate
– the hypothalamus which is the regulating centre for temperature and water balance
Structure of the Brain
cerebrum
cerebellum
Medulla
Oblongata Pituitary gland Spinal cord
hypothalamus
Cerebrum
• The cerebrum is split into left and right
cerebral hemispheres.
• Each region is discrete an performs it’s
own function
• The left cerebral hemisphere has
sensory and motor strips in the centre.
Sensory Area
• Each sensory area receives information
from sense organs (receptors)
• Information is passed onto other areas of
the brain to be analysed
• The size of the sensory area allocated to
each region of the body is in proportion
to the relative number of receptor cells
– The more sensitive the body part, the larger
the region of the sensory strip
Motor Area
• Each motor area consists of motor
neurones which send out impulses to
bring about voluntary movements of
skeletal muscles
• The size of each motor area is in
proportion to mobility resulting from the
relative number of motor endings present
– the more mobile the part, the larger the
region of the motor area
Learning Objectives
• Describe the function of the nervous
system
• State the components of the central
nervous system
• Describe a reflex arc and explain its
purpose
The Nervous System
• The nervous system controls our bodies and helps us respond to external stimuli.
• There are two main parts: – Central nervous system – brain and spinal
cord
– Peripheral nervous system – the rest of the nervous system.
• The nervous system works by sending electrical impulses along neurones (nerve cells).
Responding to external Stimuli
• Sense Organs contain receptor cells
detect changes in the environment
• These changes are called Stimuli
• Make a list of receptor cells in the
human body, and write down what
they are sensitive to.
Sensitivity
• Receptor cells can be found in – Eyes
• sensitive to light
– Ears • sensitive to sound
• respond to changes in position and enable us to keep our balance.
– Tongue and nose • sensitive to chemicals, enable us to taste and smell.
– Skin • sensitive to touch, pressure, pain and temperature
The Nervous System
• The information from the sense organs to the central nervous system along neurones
• There are two main parts to the nervous system: – Central nervous system
• brain and spinal cord
– Peripheral Nervous System • A network of neurones
Responding to changes
Receptors
in the
body
detect a
change
inside or
outside of
the body
Central
nervous
system
co-ordinates
the body’s
responses
effectors
cause a
response
by moving
part of the
body or
secreting a
hormone
Reflex Action
(extension notes)
• Some responses to stimuli are
automatic and rapid these are called
reflex actions.
• In a reflex action three types of
neurone are involved sensory, relay
and motor neurones.
• In a reflex action:
– Impulses from a receptor pass along a sensory neurone to the central nervous system.
– At a junction (synapse) between a sensory neurone and a relay neurone in the CNS, a chemical is released which causes an impulse to be sent along a relay neurone.
– A chemical is then released at the synapse
between a relay neurone and a motor
neurone in the CNS. This causes impulses to
be sent along a motor neurone to the organ
(effector), which brings about the response.
– Effector is either a muscle or a gland. A
muscle responds by contracting, a gland by
releasing chemical substances.