Brain and Nervous System Intermediate 2 Biology
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Brain and Nervous System
Intermediate 2 Biology
The Brain
The brain
• The brain is at the top of the spinal cord and is protected by the skull.
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
The
Cerebral
Cortex
The Brain
Sensory Area Motor Area
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
The sensory homunculus
Body parts
are drawn in
proportion to
their sensitivity
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
The motor homunculus
Body parts
are drawn in
proportion to
their mobility
and fine
motor control
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
• What does your nervous
system do for you?
The Nervous System
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 Arc
Reflex Action a rapid, automatic, involuntary response to a stimulus
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.
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