Section 12

 The brain is made up of four separate parts that do different jobs  These are:  The cerebrum  The cerebellum  The medulla oblongata  The hypothalamus

Hypothalamus Pituitary Gland Cerebellum Cerebrum Medulla

 The cerebrum is the largest part of the brain which split into two cerebral hemispheres  Both halves of the cerebrum are involved in conscious thought and decision making processes, as well as controlling your personality, emotions, sight and speech

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Motor StripSensory Strip Front of cerebrum

 The sensory strip is an area of the cerebrum that deals with all incoming information from the senses; ears, eyes, nose, tongue and skin  This information is processed here and then you decided what to do  E.g. You taste cabbage, realise that you do not like the taste and then decide to spit it out!  Areas of the body which are more sensitive have a larger area of the sensory strip devoted to it

 The motor strip is an area of the cerebrum in front of the sensory strip  The motor strip sends information to muscles of the body that we control by conscious thought  If an area of the body has a greater degree of movement, such as the hands, then a larger area of the motor strip is devoted to the hands

Arm Fingers Motor Strip The area of the motor strip devoted to the fingers is much larger than that of the arm. This is because the fingers have much more movement than the arm.

Sensory Strip Chest Lips The area of the sensory strip devoted to the lips is much larger than that of the chest. This is because the lips have much more sensitive than the chest

The diagram above shows how a human being might look if their body was in proportion to the number of motor neurones in the motor strip in the cerebrum The diagram above shows how a human being might look if their body was in proportion to the number of sensory neurones in the sensory strip in the cerebrum

 The cerebellum controls subconscious activities associated with the fine motor control of muscles (co-ordination) and balance  Fact! Cats have a larger cerebellum than humans – this makes them great at balancing!

 The medulla controls most of the basic bodily functions that we need to stay alive. If your medulla stops working, you are considered clinically dead.  The functions of the medulla include:  Heart rate  Breathing rate  Digestion

 The hypothalamus is an organ found just above the pituitary gland, on the underside of the brain  The hypothalamus has many functions, but two important functions are:  Monitoring temperature  Monitoring the osmotic concentration of the blood Hypothalamus

Use the words cerebrum, cerebellum, medulla and hypothalamus to complete the following 1. Centre for conscious thought 2. Needed for co-ordinating our muscles for walking 3. Controls sneezing and coughing 4. Monitors our body temperature 5. Contains the motor and sensory strip 6. Regulates out heart rate

1. Cerebrum 2. Cerebellum 3. Medulla 4. Hypothalamus 5. Cerebrum 6. Medulla

 The brain and the spinal cord make up the central nervous system (CNS)  The CNS controls all areas of the body by sending information to and from the CNS through special cells called neurones

 There are three different types of neurone:  Sensory neurones  Relay neurones  Motor neurones  Sensory neurones pick up information from our senses e.g. information about sound, light, touch, taste or smell  The brain decides what it wants to do with this information and nerve impulses are sent to muscles or glands to bring about the appropriate response  Muscles and glands are known as effectors

 A neurone is the term used to describe a nerve cell  A sensory neurone is a type of nerve cell that passes messages back to the CNS from sense organs Cell Body Nucleus Direction of impulse Skin CNS

 Relay neurones are found in the CNS. They connect (relay) information from sensory neurones to other neurons in the body.

 Motor neurones transmit information to effectors such as muscles  Motor neurones carry nerve impulses from relay neurones in the CNS to effector muscles and glands

Sensory neurone Motor neurone Relay neurone Section of the spinal cord

 A reflex arc is an arrangement, usually of three neurones, that allows a reflex response to take place  The response in a reflex arc is extremely fast because only three neurones are involved in the response  Only the spinal cord is involved in this process which means that you do not use your brain to think of what to do in these situations  E.g. sneezing, coughing, blinking, moving your hand from a very hot object  Reflex reactions are very important – they could save you from danger to your life or damage to your body

Sensory neurone Relay neurone Motor neurone

 Using the diagram on the next slide, describe what is happening using the following words:  Motor neurone  Sensory neurone  Reflex arc  Rapid  Relay neurone  Effector (muscle)  Stimulus

 A harmful stimulus is detected by sensory neurones. This is passed on to the relay neurone in the spinal cord.  The message is then passsed on to the motor neurone which ends in an effector (muscle) to move the hand away from the harmful stimulus. This is an example of a reflex arc because it is a rapid response.

1. What do the letters CNS stand for? 2. Name the two principle types of neurone 3. Which of these two links the CNS with the effectors? 4. Describe three features of reflex actions 5. Give two examples of reflex actions

1. Central Nervous System 2. Sensory and Motor 3. Motor 4. They are quick, automatic and difficult to suppress 5. Coughing and Sneezing

 The hypothalamus is the body’s temperature regulatory mechanism  Thermoreceptors are special cells that detect information about heat and cold  There are thermoreceptors in the skin that convey information about the temperature of the skin surface Hypothalamus

 The hypothalamus also contains central thermoreceptors that detect changes in the temperature of the blood and the body core  If the temperature of the body cores gets too high or too low, effectors trigger responses to get the body temperature back to normal Body Shell Body Core ReceptorsCNSEffectors

 The skin plays a leading role in temperature regulation  The skin acts as an effector in order to correct increases or decreases in temperature using the following mechanisms: i. Increase in rate of sweating ii. Vasodilation iii. Decrease in rate of sweating iv. Vasoconstriction v. Contraction of erector muscles  Temperature Increase Temperature decrease

 Heat energy from the body is used to convert water in sweat to water vapour  When this water vapour evaporates, the core body temperature is lowered and brought back to tolerable limits

 Arterioles leading to skin become dilated (larger)  A large volume of blood is allowed to flow through capillaries near the skin surface, where heat radiation can occur  This loss of heat lowers body temperature

 Decrease in rate of sweating reduces heat loss as water cannot be converted to water vapour  Vasoconstriction is the opposite of vasodilation – here the arterioles constrict, minimising heat lost by radiation

 Contraction of erector muscles – this process is more effective in furry animals than humans  This process works by hairs being raised up from the skin surface, trapping a layer of air which acts as an insulator

Thermoreceptors detect decrease in temperature Cerebrum, which controls conscious decision making becomes aware of cold Appropriate voluntary action taken to increase body temperature The ability to make voluntary responses is an important part of control of body temperature

 All of the mechanisms that you have learned about are to bring the body’s core temperature back to normal levels  This mechanism is called negative feedback control  When a factor increases beyond a set point i.e. above 37 o C, a response is triggered that may cause that factor to decrease to normal levels and vice versa

Normal body temperature (37 o C) Increase in body temperature decrease in body temperature Thermoreceptors in hypothalamus Motor nerve impulses to skin Vasodilation, increased sweating Vasoconstriction, decreased sweating Increase in body temperature decrease in body temperature Thermoreceptors in hypothalamus No change in body temperature (temperature remains at set point)

A Look carefully at the diagram above. Decide whether the response is to cold temperature or hot temperature and describe what is happening at points 1, 2 and 3. Make sure you write in sentences.

B Look carefully at the diagram above. Decide whether the response is to cold temperature or hot temperature and describe what is happening at points 1, 2 and 3. Make sure you write in sentences.

1. What happens to capillaries near the surface of the skin when we are too hot? 2. What must happen to sweat before it has a cooling effect? 3. Which chemicals in our cells are particularly sensitive to temperature change? 4. What term is used to describe the control mechanism that maintains body temperature?

1. More blood is diverted through them to enable the body to lose more heat 2. It must evaporate 3. Enzymes 4. Negative feedback control