2.3 Control and Communication

Learning Intentions Describe and identify the structures of the brain as the cerebrum, the cerebellum and the medulla and explain their main functions. State that CNS is made up of the brain and the spinal cord. Describe the function of the CNS as processing sensory information and bringing about appropriate responses. Explain that reflexes are rapid responses to environmental changes and are protective in nature. Describe the three types of neuron involved in a reflex arc. Explain the role of sensory, relay and motor neurons in reflexes. State that electrical impulses move along neurons. State that the gaps between neurons are called synapses and that chemicals transfer messages between neurons.

Need for Co-ordination All the body’s organs and systems need to be able to work together to allow the many functions that are essential to life. The body needs to be co-ordinated

Need for co-ordination Physical activity (exercise) is one of the body’s essential functions. information is picked up about where the ball is using the sense organs (in this case the eyes). When a tennis player is about to hit the ball – Example This information is sent to the brain. The brain sends out messages to the correct muscles to move the body in the correct way. There are hundreds of muscles in the body, so this can be a very complex process.

The Nervous System The nervous system is composed of the brain, the spinal cord and nerves. brain spinal cord nerves

The Nervous System The spinal cord is protected by the spine.

The Nervous System The brain sorts out information. The spinal cord sends information to and from the brain. The brain and spinal cord make up the central nervous system (CNS). Nerves carry information from the senses to the CNS. Nerves carry information from the CNS to the muscles. These make up the peripheral nervous system [PNS]

The Nervous System Information from the sensory nerves is sorted out by the CNS. Information from the CNS is then carries by the motor nerves to the appropriate muscles which then contract.

The Brain Cerebrum Cerebellum Medulla Spinal Cord

The Brain Largest part of the brain. Divided into 2 halves (hemispheres – left and right). Each region is concerned with particular functions e.g. sensory area, motor area (movement), hearing, sight etc. The cerebrum is highly developed in humans. Cerebrum Cerebellum Medulla Controls balance and coordination. Controls the rate of breathing and heartbeat.

The Brain sensory area receives nerve impulses from the senses motor area transmits nerve impulses to muscles sight hearing

Reflex actions A reflex action is a rapid, automatic response to a stimulus. e.g. Imagine you accidentally touched a bunsen burner which was still hot from the previous class. How would you respond ??? The stimulus is the heat from the bunsen (pain). The response is that you pull your hand away very quickly. You don’t even have to think about it!!!

Reflex actions Reflex actions happen so quickly that there is often no time for the nerve impulses to reach the brain. Often the impulse only goes to the spinal cord and the brain becomes aware of the action only after it has happened. See shared area for Diving reflex film

Reflex actions Some examples are… pulling a limb away (hand, arm, leg etc) knee jerk reflex eye blink reflex So reflexes protect the body from damage.

The reflex arc CNS muscles contract = movement RESPONSE Skin receptor senses pain = signal sent STIMULUS sensory neurone motor neurone relay neurone white matter contains nerve fibres grey matter contains cell bodies

Which type of nerve does what job? Sensory nerve cells send a message to the spinal cord. A relay nerve connects the sensory nerve to the motor nerve in the spinal cord. A signal to make a muscle contract is sent down a motor nerve.

Synapses Gaps between nerves are called synapses Electrical impulses cannot pass Neurotransmitters released from 1 st nerve Chemicals diffuse across synapse Chemicals bind to receptors of next nerve This triggers electrical impulse

Discovery of Neurotransmitters Vagus nerve stimulated in heart 1 Vagus nerve slows down heart rate Fluid passes from heart 1 container to heart 2 container Heart 2 slows down

Learning Intentions State the function of an endocrine gland. State that hormones are chemical messengers. State that target cells have receptors for that hormone on their surface Explain that only cells that have the receptor for the hormone are affected by the hormone. State that changes in blood glucose levels are detected by the pancreas. Explain that when blood glucose levels increase, the pancreas produces more insulin which in turn activates an enzyme within its target cells (liver) that converts glucose into glycogen.

Introduction to Hormones

Endocrine System  Endocrine System is made up of many glands.  Hormones are specific.  Target tissue contains receptors for hormone  They are slow-acting.  Hormones travel in blood.  These glands produce hormones - chemical messengers hormones-1022/ hormones-1022

Endocrine Glands and Secretions

Control of blood sugar levels mwww.abpischools.org.uk/page/modules/hormones/horm6.cf m The sugar glucose is an important source of energy for the body. Food is metabolised to release glucose, which is converted to CO 2 and water during respiration and used to make ATP. If there is too much glucose in the blood then it is converted to glycogen and stored in the liver until it is needed (it may also be stored as fat). If the glucose levels are low then glycogen is converted back to glucose, which can then be used by the body.

The receptor cells that monitor the changes in blood sugar levels are found in the islets of Langerhans. These are specialised cells in the pancreas that secrete two different hormones in response to changes in concentration of glucose in the blood: – Insulin – Glucagon

Insulin Insulin is secreted when the blood glucose level is high. This hormone catalyses the conversion of glucose to glycogen in the liver. As a result the blood glucose level falls.

Glucagon Glucagon is secreted when the blood glucose level is low. This hormone catalyses the conversion of glycogen to glucose in the liver. As a result the blood glucose level rises. See shared area for film on Insulin

BOO! Your heart starts beating really fast, you are very alert and you suddenly have loads of energy. This is because of adrenaline, a hormone that the adrenal glands secrete to prepare the body for an emergency (e.g. an attack). Adrenaline increases the body's rate of metabolism and influences the concentration of sugar in the blood.

The secretion of adrenaline causes the conversion of glycogen to glucose to provide the body with enough energy to protect itself. When the emergency is over, the adrenaline levels fall and the regulation of blood sugar levels is under homeostatic control again.

Diabetes Mellitus Some people are unable to make enough (or any) insulin to regulate their blood sugar levels. This is a common disorder that is known as diabetes mellitus (or diabetes).

Symptoms of diabetes People who suffer from diabetes have high levels of glucose in their blood as they are unable to convert it to glycogen or fat due to a lack of insulin. This excess sugar is excreted in the urine; other symptoms include rapid weight loss, dehydration and frequent urination. Diabetes is very dangerous and can result in a sufferer falling into a coma and dying if it is left untreated. Fortunately, diabetes can be treated effectively with daily insulin injections and a careful diet.