1. OCR 21st Century Additional Science
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B6 Brain and Mind
OCR 21st Century Additional Science
W Richards
The Weald School

2. B6.1 How do animals respond to changes in their environment?
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B6.1 How do animals respond to changes in their environment?

3. The Nervous System
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The CENTRAL NERVOUS SYSTEM (CNS) enables us to react to changes in our surroundings (“stimuli”). It consists mainly of the brain, the spinal chord, nerve cells (“neurones”) and receptors.
Types of receptor:
Light receptors in the eyes
Sound receptors in the ears
Taste receptors on the tongue
Smell receptors in the nose
Touch, pressure and temperature receptors in the skin
Changes of position receptors in the ears (balance)

4. Stimulus Receptor Coordinator Effector Response
Nervous Reactions
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When we react to a stimulus our bodies use the following pattern and these signals are sent using electrical impulses:
Stimulus Receptor Coordinator Effector Response
For example, consider a man and a camel:
Oh No!
What are the stimulus, receptor, coordinator, effector and response in this situation?

5. Examples of reactions Stimulus Receptor
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Stimulus
Receptor
(i.e. the thing that detects the stimulus)
Effector
(i.e. the thing that will do the reaction)
Response
(i.e. action taken)
Bright light
Sour taste
Losing balance
Sit on a drawing pin

6. Simple reflexes in humans
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Babies can demonstrate simple reflexes:
Stepping reflex
Startle (or moro) reflex
Grasping reflex
Rooting reflex
Sucking reflex

7. The Iris Reflex
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When the light is bright the radial muscles relax, the circular muscles contract and the pupil increases in size.
When the light is bright the radial muscles _____, the circular muscles _______ and the pupil ________ in size.

8. Reflex Actions in Animals
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Simple animals rely on reflex actions for most of their behaviour:
Stimulus in a simple animal
What is their response?
Feeling hungry
Feeling cold
Feeling threatened

9. Slower responses - hormones
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Nervous impulses are electrical signals and are transmitted quickly through the body. The body can also produce a slower response using chemical messengers called hormones.
Examples of bodily processes that use hormones:
Controlling of water content by the kidneys and the brain:
The menstrual cycle, using hormones from the brain and ovaries:
The development of nervous and hormonal communication systems depended on the evolution of multicellular organisms.

10. B6.2 How is information passed through the nervous system?
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B6.2 How is information passed through the nervous system?

11. Conscious actions
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A conscious action is one where the brain makes a considered response. Here’s what happens:
4) The brain decides to move away the hand
3) Here another sensory neurone carries the signal to the brain
5) This impulse is sent by MOTOR NEURONES to the hand muscles (the effectors) via the spinal chord…
2) The impulse is carried by SENSORY NEURONES to the spinal chord
1) Receptors in your skin detect a stimulus
6) Which then moves the hand away
Stimulus Receptor Sensory Neurone Coordinator
Motor Neurone Effector Response

12. Reflex actions
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Sometimes conscious action is too slow to prevent harm, e.g…
In situations like this the body bypasses the brain to produce a quicker response. Here’s how it works…

13. Reflex actions 3. Relay neurone in the spinal chord 2. Sensory neurone
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3. Relay neurone in the spinal chord
2. Sensory neurone
4. Motor neurone
5. Effector
1. Receptor

14. Types of nerve cell (“neuron”)
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Nerve cells (neurons) are elongated with branched endings to connect to many muscles fibres and aid the transmission of electrical impulses:
Axon – a long extension of cytoplasm surrounded by a membrane
Muscle strands (effector)
Nucleus
Fatty sheath to increase the speed of transmission and to insulate the neuron from surrounding cells

15. The CNS and the PNS
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The Central Nervous System (CNS) is the spinal cord and brain:
The Peripheral Nervous System (PNS) is the collection of neurones connected to the CNS:
There are two types of neurone we need to consider:
1) Sensory neurone
Impulse
These carry impulses from the receptors to the CNS
2) Motor neurone
Impulse
These carry impulses from the CNS to effectors

16. Words – chemical, synapse, neurone, touch, reabsorbed
Synapses
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Neurones never ____ each other – there is a small gap between them called a _____. A signal is sent from one _______ to the next by a _______ transmitter across the synapse (called a “neurotransmitter”). These transmitters are then ________ back into the sensory neurone to be used again. This process only reacts with specific chemicals that bind to the receptor molecules.
Words – chemical, synapse, neurone, touch, reabsorbed

17. Drugs and the Nervous System
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Drugs are classed as “a substance that affects the central nervous system, causing changes in psychological behaviour and possibly addiction”. They do this by affecting the transmission of impulses. Consider Ecstasy for example:
Ecstasy (MDMA) blocks the sites in the brain’s synapses where the transmitter substance serotonin is removed.
Beta blockers and Prozac can also affect the transmission of impulses.

18. The Cerebral Cortex
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The cerebral cortex is the part of our brain most concerned with intelligence, memory and consciousness. By studying the effects (e.g. memory/sight loss) when different parts of the brain are damaged scientists have been able to identify which parts of the brain control which functions.

19. Other techniques of studying the brain
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1) An electroencephalogram (EEG) is a visual record of the electrical activity generated by neurons in the brain. It works by amplifying and detecting the electrical signals from the brain.
2) Magnetic resonance imaging (MRI) scanning is a new technique that produces images of different cross sections of the brain and uses colours to represent activity.

20. Conditioned reflexes - Pavlov’s Dog
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Ivan Pavlov,
I won the Nobel Prize in 1904 and am most famous for investigating “conditioned responses”:
Steak + dog = saliva
Steak + bell + dog = saliva
Bell + dog = saliva
Notice that the final response (saliva) has no direct relation to the stimulus (the bell). Conditioned reflexes can increase an animal’s chance of survival!

21. Reflex actions
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Sometimes the brain can modify a reflex response via a neuron to the motor neuron of the reflex arc, meaning that you could keep hold of a hot object:

22. B6.4 How do humans develop more complex behaviour?
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B6.4 How do humans develop more complex behaviour?

23. Human Brains
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Ug. My chances of survival were made a lot better when my brain got bigger. Notice I can now use simple tools!
Mammals have complex brains with billions of neurons. The interaction between our ancestors and their environment caused neuron pathways to form in the brain.

24. Learning Complex Behaviour
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PET scan showing areas “activated” by doing algebra.
When the brain is asked to do certain tasks different areas are “activated”. New experiences cause new neuron pathways to develop, while pathways that are not used are eventually destroyed. This is why we become better at certain tasks when we practice them more often.

25. Feral children
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Task: to find out what “feral children” are, what has caused their condition and what the consequences are.

26. Memory Our memory is divided into two types: short term and long term.
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Our memory is divided into two types: short term and long term.
Short term memory is capable of storing a limited amount of information for a limited amount of time. Long term memory is when more information is stored over a much longer time.
Ways of improving
short term memory,
e.g. a phone number
Ways of improving
long term memory
e.g. exam revision

27. Using Models to Explain Memory
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We can understand memory better by using models to explain it, for example:
What could cause a model to be limited in explaining how memory works?