Coordination and Response PDF

## Coordination and Response Organisms have the ability to detect changes in their environments and respond to these changes. This ability is called sensitivity while the change that stimulates the response is known as a stimulus (plural: stimuli). The stimulus is divided into two types, that is, ex...

## Coordination and Response Organisms have the ability to detect changes in their environments and respond to these changes. This ability is called sensitivity while the change that stimulates the response is known as a stimulus (plural: stimuli). The stimulus is divided into two types, that is, external stimulus and internal stimulus. - Stimuli from the external environment include light, sound smell, taste, surrounding temperature, pressure and touch. - Stimuli from the internal environment include changes in blood osmotic pressure, changes in body temperature and changes in blood sugar level. Mammals can detect stimuli via the special sensory cells known as receptors. When a receptor detects a stimulus such as sound, the stimulus is converted to nerve impulses. Nerve impulses are sent to the brain through nerve cells or neurones. The brain is the integration centre that translates nerve impulses and coordinates an appropriate response. Response refers to the way organisms react after detecting a stimulus. The part of the body that responds is called the effector. Examples of effectors are muscles and glands. Figure 12.1 and Figure 12.2 explain the main components and pathways involved in detecting and responding to changes in external and internal environments. ### Main Components and Pathways Involved in Detecting and Responding to Changes in the External Environment - Stimulus from the external environment (example: the sound of phone ringing) - Detected by sensory receptors in the sensory organs and transformed into nerve impulses - Nerve impulses are sent through the sensory neurone to the integration centre - In the integration centre (the brain), nerve impulses are interpreted and a response is triggered - Impulses are sent through the motor neurone to the effector - Effector (hand muscles) produces a response (answering the telephone) ### Receptors and effectors work together to bring suitable changes depending on the stimulus detected. - Coordination is a stimuli detection process by receptors that ends in appropriate responses by effectors. Coordination ensures that the overall activities and systems of an organism function and are synchronised perfectly as a complete unit. The role of coordination and response is conducted by two separate systems, that is, the nervous system and the endocrine system. - Both systems work together to coordinate and control responses. ### Main Components and Pathways Involved in Detecting and Responding to Changes in the Internal Environment - Detected by receptors (baroreceptor) in the aortic arch and carotid artery - Stimulus from the internal environment(example: blood pressure increases during running) - Nerve impulses are sent through the sensory neurone to the integration centre - Integration centre(cardiovascular control centre in the medulla oblongata) - The cardiovascular control centre sends nerve impulses through the motor neurone to the effectors - The effectors react (weakened contraction of cardiac muscles and the expansion of blood vessels' diameter) to reduce the blood pressure to the normal range ### Types of Receptors Sensory receptors found at the end of the nerve fibres detect information in the external and internal environments. The location of receptors will depend on the type of stimulus detected. Each type of receptor is usually sensitive to a specific stimulus. For example, the sensory receptors that detect external stimuli are found in special sensory organs such as eyes, nose, tongue and skin. The sensory receptors that detect internal stimuli are present in specific internal organs such as the pancreatic cells that detect blood sugar level. | Sensory Receptor | Stimulus | | ----------------------- | ------------------- | | Photoreceptor | Light | | Thermoreceptor | Change in temperature | | Chemoreceptor | Chemical substances | | Baroreceptor | Change in pressure | | Mechanoreceptor | Touch and pressure | | Nociceptor | Pain | ### Necessity of Response Why do organisms have to respond to stimuli and internal stimuli? The ability of organisms to detect changes in the external environment and its response to the stimuli is very important for the survival of organisms. For some animals, a sudden change in climate conditions motivates the animals to look for new shelters. The ability of organisms to detect changes in the internal environment is also crucial so that the information can be transmitted to the integration centre. The integration centre will then transmit this information to the effectors to respond to the changes. For example, when the body temperature increases above the normal range, this information will be transmitted to the integration centre by a receptor. The integration centre will send nerve impulses to the effectors to decrease the temperature back to its normal range. In conclusion, humans and animals need to respond to adapt to the changes in the environment. ## Nervous System The human nervous system is made up of a network of nerve cells or neurones. This system is divided into two main subsystems: the central nervous system and the peripheral nervous system. ### Central Nervous System - Includes the brain and spinal cord. - The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. - The cranial nerves send nerve impulses from and to the brain. - Spinal nerves send nerve impulses from and to the spinal cord. ### Brain Do you know that the brain is made up of more than 100 billion neurones? The brain is the coordination and control centre for humans. The main components of the brain are the cerebrum, hypothalamus, cerebellum, medulla oblongata and pituitary gland ### Cerebrum - The largest and most complex structure present in the frontal part of the brain. - The surface is folded to increase the surface area to hold more nerves. - It is the centre that controls emotions, hearing, sight, personality and controlled actions. - The cerebrum receives information and stimulus from the receptor. - This information is analysed, integrated and correlated to produce sensory perception. - The response is determined and instructions are given to the effectors. - The cerebrum is also responsible for higher mental abilities such as learning, memorising, linguistic skills and mathematics skills. ### Hypothalamus - Coordinating homeostasis. - It is the control centre that regulates body temperature, water balance, blood pressure, and senses hunger, thirst and fatigue. - The hypothalamus connects the nervous system to the endocrine system through the pituitary gland. - Controls the secretion of a few types of pituitary gland hormones. ### Cerebellum - Maintains body balance and coordination of muscle contraction for body movement. ### Pituitary Gland - Located at the base of the hypothalamus. - The main gland in the endocrine system. - This gland secretes hormones that control the secretion of hormones by other endocrine glands. ### Medulla Oblongata - Located at the anterior of the cerebellum. - Controls involuntary actions such as heartbeat, breathing, food digestion, vasoconstriction, blood pressure, peristalsis, vomiting, coughing, sneezing and swallowing. ### Spinal Cord The spinal cord is contained within the vertebral column and is surrounded by cerebrospinal fluid that protects and supplies the spinal cord with nutrients. The spinal cord is made up of white matter and grey matter. - In a cross section, the grey matter looks like a butterfly or the letter 'H'. Grey matter comprises mainly of cell bodies and is surrounded by white matter. White matter consists of axons covered in myelin sheath and extends up and down the spinal cord. - The spinal nerve extends from the spinal cord through two short branches or roots which are the dorsal root and ventral root. The function of the spinal cord is to: - process a few types of sensory information and to send responses through the motor neurones - control reflex action - connect the brain with the peripheral nervous system ### Peripheral Nervous System The peripheral nervous system consists of the somatic nervous system and autonomic nervous system. - The somatic nervous system regulates all controlled actions. - The autonomic nervous system controls involuntary actions such as heartbeat and contraction of the blood vessel. - The function of the peripheral nervous system is to connect sensory receptors and effectors to the central nervous system. ## Neurons and Synapse The nervous system is made up of millions of nerve cells known as neurones. The basic structure of a neurone consists of a cell body, axon, dendrite, myelin sheath, a node of Ranvier and a synaptic knob. There are three types of neurones which are sensory neurones, relay neurones and motor neurones ### Dendrite - Dendrites are short branches of the cell body. - Dendrite receives nerve impulses from other neurones or the external environment and sends them to the cell body. ### Cell Body - A cell body consists of a nucleus and many cytoplasmic projections called dendrites. - The cell body integrates signals and coordinates metabolic activities. ### Axon - Axon is an elongated branch of the body cell. - Axon carries impulses out of the cell body to other neurones or effectors. ### Myelin Sheath - Myelin sheath is an insulating membrane that coats the axon. - Function of the myelin sheath is to protect neurones from injury, functions as an insulator for electrical impulses, provides nutrients to the axon ### Node of Ranvier - Certain neurones have parts that are not insulated by the myelin sheath at regular gaps along the axon. - This gap is known as a node of - The node of Ranvier helps to accelerate the flow of nerve impulses by allowing the nerve impulses to jump from one node to the following node. ### Synaptic Knob - The synaptic knob is a swelling at the end of the axon branch. - The synaptic knob sends signals to muscle cells, gland cells or other neurone dendrites. ### Sensory Neuron - Present in the dorsal root of the spinal nerve. - Carries nerve impulses from the sensory organ receptors to the central nervous system. - The cell body is found in the dorsal root ganglion. - Dendrites receive nerve impulses from receptors and send them to the cell body. - The nerve impulses are transferred from the cell body through the axon to the next neurone. ### Motor Neuron - Can be found in the ventral root of the spinal nerve. - Receives nerve impulses from the relay neurone of the central nervous system and sends nerve impulses to effectors such as muscles or glands to produce the appropriate response. - The cell body is present in the grey matter of the spinal cord. ### Relay Neuron - Nerve fibres found in the central nervous system. - Connects the sensory neurone to the motor neurone. - The cell body can be found in clusters in the grey matter of the central nervous system. - Sends nerve impulses from the sensory neurone to the central nervous system and from the central nervous system to the motor neurone. ### Structure and Functions of Synapses Information is sent along the neurone through electrical signals known as nerve impulses. Impulses are positively charged waves that flow along the axon to the synaptic knob. There is a narrow gap called synapse that separates the synaptic knob from neurone dendrites that receive the impulses. Electrical signals that carry information must be transferred across synapses for impulses to be transmitted to the following neurone. ### Transmission of Impulse Across a Synapse Impulses are transmitted chemically across synapses. The chemical substances involved are neurotransmitters that are kept in synaptic vesicles that are found at the end of the synaptic knob. Two examples of neurotransmitters found in most synapses are acetylcholine and noradrenaline. Other examples are serotonin and dopamine. The process of transmitting impulses through synapses is slow as it occurs chemically. At first, the electrical signal will be changed to a chemical signal in the form of a neurotransmitter, then the chemical substance is converted again to an electrical signal on the membrane of the receiving neurone. The transmission of impulses across synapses is shown in Figure 12.9. ### Voluntary and Involuntary Actions Responses produced are either voluntary action or involuntary action. | Actions | Similarity | Involuntary Action | | ----------- | --------- | ------------------- | | Voluntary Action | Both actions involve stimulation, impulse, neurone and an effector organ. | Actions that occur automatically and occurs without us being conscious | | Actions that we are conscious of and done on our own will | | Involves the autonomous nevous system | | Involves the somatic nervous system | | Controlled by the medulla oblongata and hypothalamus | | Controlled by the cerebral cortex | | Involves the reaction of the smooth muscle and glands | | Involves the reaction of the skeletal muscles | | | ### Voluntary Actions Involving Skeletal Muscles - Voluntary actions such as walking, talking or brushing teeth are conscious actions. - For example, you can voluntarily raise your hand to answer a question. - The voluntary actions involving the skeletal muscles are controlled by the cerebral cortex. - Since the information reaches the cerebral cortex, that is, our level of consciousness, our - perception of the surroundings can be produced. - The information pathway in voluntary action is demonstrated in Figure 12.10. ### Involuntary Actions Involving Skeletal Muscles: Reflex Response - Several situations require immediate and spontaneous action. - If you accidentally prick your finger on a sharp pin, you will move your finger immediately without much thought. - This is known as a reflex action. - A reflex action is a fast response a stimulus without being controlled by the brain. - The nerve pathway involved in a reflex action is called the reflex arc - The reflex action of moving the finger from the sharp pin involves three neurones and communication between the neurones in the peripheral nervous system and the spinal cord. ### Three-Neuron Reflex Arc - When a finger is pricked by a sharp pin, the sensory receptor detects the stimulus and triggers a nerve impulse. - The nerve impulse is transmitted along the sensory neurone to the spinal cord. - In the spinal cord, the nerve impulse is transferred from the sensory neurone through the synapse to the relay neurone. - From the relay neurone, the nerve impulse is transferred to the motor neurone. - The motor neurone transfers the nerve impulse from the spinal cord to the effector (muscle tissue) so that the finger can be moved quickly. ### Importance of Reflex Actions - Reflex actions produce spontaneous responses without waiting for instructions from the brain. - The additional time that is needed by the brain to analyse information before triggering a response can lead to serious injuries. - Since reflex actions involve the spinal cord, the brain can focus on higher-level thinking. ### Two-Neuron Reflex Arc Another reflex action is the knee jerk or patellar reflex. This reflex uses the nerve pathway that involves two neurones, that is, the sensory neurone and the motor neurone. The doctor sometimes tests the effectiveness of someone's nerve system by tapping on the knee using a rubber hammer. - When the tendon below the kneecap is knocked, the quadriceps muscle stretches and stimulates the stretch receptors to trigger nerve impulses. - The sensory neurone transmits the nerve impulses to the motor neurone in the spinal cord. - The motor neurone then transmits impulses from the spinal cord to the quadriceps muscle. - The quadriceps muscle contracts causing the leg to jerk to the front. ## Health Issues Related to the Human Nervous System We should be thankful for having a central nervous system that functions well. However, the central nervous system can become damaged and stop functioning efficiently. A few examples of health issues related to the nervous system are given below. ### Multiple Sclerosis - A progressive disease as a result of an abnormality in the immune system that attacks the myelin sheath in the brain and spinal cord. - The damaged myelin sheath prevents the transmission of impulses from and to the brain. ### Alzheimer's Disease - This disease causes the loss of ability to reason and to take care of oneself. - The patient is usually confused, forgetful and disoriented even in a familiar place. - If the deterioration of the brain continues, the patient will lose the ability to read, write, eat, walk and talk. ### Parkinson's Disease - It is the shrinkage of the nervous system that causes tremors in the limbs, jaw, foot and face. - The patient will also have difficulty maintaining body posture and balance. ### Lou Gehrig/Amyotrophic Lateral Sclerosis (ALS) - This disease is caused by the deterioration and death of motor neurones that control the movement of muscles such as chewing, walking and talking. ### Attention-Deficit Hyperactivity Disorder (ADHD) - A type of brain disease that causes someone to become hyperactive, unable to concentrate and gets easily bored. ### Autism - A type of disease related to the development of nerves in the brain. - Autism causes an individual to experience problems communicating and interacting. ## The Effects of Drug and Alcohol Abuse on Human Coordination and Response There are many types of drugs used for medical purposes, for example, marijuana is used by doctors in small quantities to reduce nausea in cancer patients after undergoing chemotherapy treatment. However, drug abuse other than for medical purposes can cause serious side effects and would most likely be fatal. Among the effects of drug abuse on drug addicts are: - Addiction: An addiction that causes withdrawal symptoms such as shivering, sweating and vomiting if the drug is not taken - Table 12.3 shows the effects of drug and alcohol on human coordination and response. | Substance | Effect | |------------|----------------| | Stimulant drugs (stimulants) | - Increases the activity of the central nervous system | - Excessive use causes temporary euphoria which is followed by depression | | Sedative drugs (depressants) | - Delays the transmission of nerve impulses | - Calms the mind | | Hallucinogenic drugs | - Causes the user to hallucinate | - Relief from pain and anxiety | | Narcotic drugs | - Delays the normal functions of the brain | | Alcohol | - Disrupts coordination and thinking | - Delays the transfer of nerve impulses| ## Endocrine System The coordination system of the body needs cooperation between the endocrine system and the nervous system. Both systems play an important role in maintaining homeostasis. Even though both systems have different functions, they interact and complement each other to regulate and coordinate all processes and activities in the body. What is the endocrine system? ### Endocrine System of Humans The endocrine system is made up of glands that secrete chemical substances, that is hormones. The endocrine glands are ductless glands. So, the hormones are secreted directly into the blood flow. Even though the hormones are transported throughout the body in the blood, the hormones only influence and affect specific target cells. The hormones bind with specific molecule receptors on the membrane surface of target cells and produce specific responses. The endocrine system of humans is made up of many glands. The glands secrete different hormones involved in specific physiological processes. The functions of hormones can be divided into three main functions: reproduction, growth and homeostasis. Figure 12.13 shows the endocrine glands. ### Functions of Hormones Secreted by Each Endocrine Gland The pituitary gland is the main gland of the endocrine system because it secretes hormones that control the secretion of other endocrine glands. The pituitary gland is located at the bottom of the hypothalamus in the brain. The pituitary gland is made up of two lobes, which are the anterior lobe and the posterior lobe. Each lobe secretes hormones that have certain functions. ### Posterior Lobe of the Pituitary Gland | Hormone | Target Tissues/Organs | Function | | -------- | -------- | -------- | | Antidiuretic (ADH) | Kidney tubule | Stimulates the reabsorption of | | | Uterine Muscles | Stimulates the contraction of uterine muscles during birth | | Oxytocin | Mammary glands | Stimulates the production of milk from the mammary gland | ### Anterior Lobe of the Pituitary Gland | Hormone | Target Tissues/Organs | Function | | -------- | -------- | -------- | | Luteinizing hormone (LH) | Ovary | Stimulates ovulation, development of corpus luteum, and secretion of oestrogen and progesterone | | | Testis | Stimulates secretion of testosterone | | Growth Hormone (GH) | Soft tissue, bone | Stimulates growth, protein synthesis and fat metabolism | | Adrenocorticotropic hormone (ACTH) | Adrenal cortex | Stimulates the adrenal cortex to secrete hormones | | Thyroid-stimulating hormone (TSH) | Thyroid gland | Stimulates thyroid to secrete thyroxine | | Follicle-stimulating hormone (FSH) | Ovary | Stimulates the development of follicles in the ovary | | | Testis | Stimulates spermatogenesis | The hormone that regulates the secretion of other hormones is known as the stimulating hormone. This includes thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH). For example, TSH stimulates the thyroid gland to secrete thyroxine. Hormones that act directly on target organs include growth hormone, oxytocin and antidiuretic hormone (ADH). For example, GH acts directly on the bone. The hypothalamus secretes gonadotrophin-releasing hormone (GnRH). GnRH stimulates the pituitary gland to secrete FSH and LH into the blood. ### Other Endocrine Glands - **Adrenal Gland:** - Hormone: Aldosterone - Target tissues/organs: Kidney - Function: Increases the reabsorption of salt in kidneys - Hormone: Adrenaline - Target tissues/organs: Muscle tissues, liver and heart - Function: - Increases the level of sugar and fatty acids in the blood. - Increases the respiratory rate and heartbeat. - Increases the rate of metabolism and contracts blood vessels. - **Thyroid Gland** - Hormone: Thyroxine - Target tissues/organs: All tissues - Function: - Increases the metabolism rate. - Increases body temperature. - Regulates growth and development - **Pancreas** - Hormone: Insulin - Target tissues/organs: Liver, muscles and adipose tissues - Function: Reduces blood glucose level and promotes the conversion of excess glucose to glycogen - Hormone: Glucagon - Target tissues/organs: Liver, muscles and adipose tissues - Function: - Increases the blood glucose level. - Promotes the conversion of glycogen to glucose. - **Testis** - Hormone: Testosterone - Target tissues/organs: Gonad, skin, muscles and bones - Function: Stimulates the development of secondary sexual characteristics in the male and spermatogenesis. - **Ovary** - Hormone: Oestrogen - Target tissues/organs: Gonad, skin, muscles and bones - Function: - Stimulates the development of secondary sexual characteristics in the female and maturity of the follicles. - Repairs and stimulates the thickening of the uterus wall. - Hormone: Progesterone - Target tissues/organs: Gonad - Function: Stimulates the development of the uterus wall and the formation of the placenta. ## Involvement of the Nervous System and Endocrine System in a 'Fight or Flight' Situation Have you ever been in a state of 'fight or flight' situation? For example, when a dog or a goose suddenly chases you? How do you feel in a situation like this? Your heart will beat fast and your palms will sweat. What causes this condition? In an emergency or a 'fight or flight' situation, the hypothalamus transmits nerve impulses directly to the adrenal medulla and the adrenal medulla cells are stimulated to secrete **adrenaline** and **noradrenaline**. These two hormones act quickly to produce the required responses in a 'fight or flight' situation. This includes an increase in: - Heart rate - Respiratory rate - Blood pressure - Blood glucose level - Metabolic activity The heart pumps more oxygen and glucose to the brain and skeletal muscles because additional energy is needed to fight or run quickly. In an emergency, both the endocrine system and the nervous system work together to produce an immediate response to deal with the dangerous situation. When this mechanism manages to control this 'fight or flight' situation, bodily changes that have occurred return to the normal range. What are the similarities and differences between the endocrine system and the nervous system? Figure 12.15 compares and contrasts the two systems. ### Similarities and Differences Between the Nervous System and the Endocrine System | Feature | Nervous System | Endocrine System | |---|---|---| | | | | | Made up of | A network of millions of neurones | Consists of ductless endocrine glands | | Signal | Electrical impulses through neurones | Organic chemical substances, which are hormones, through blood flow | | Duration of effect | Short | Long | | Response | Quick and immediate | Slow and prolonged | | Function | Regulates all activities of the body | Produces responses in several organs| The endocrine system plays a key role in maintaining the homeostasis of the body. However, an imbalance in hormone production can occur in some individuals when the endocrine gland secretes excessive or insufficient hormone. What is the effect of hormone imbalance to the individual? ## Health Issues related to the Human Endocrine System ### Diabetes Mellitus A diabetes mellitus patient does not produce enough insulin or cannot use the insulin produced. As a result, the level of glucose in the blood is high. The patient urinates frequently, is always thirsty, experiences numbness in the soles of the feet, has blurred vision, is tired and their wounds heal much slower. Whereas, the excessive secretion of insulin causes hypoglycaemia where the blood glucose level is too low. Among the symptoms of hypoglycaemia are fatigue, difficulties sleeping at night, disordered thoughts, fear, emotional instability, faints easily and headache. ### Diabetes Insipidus For diabetes insipidus patients, the posterior lobe of the pituitary gland fails to secrete the antidiuretic hormone (ADH). As a result, patients will produce a large amount of urine and often feel thirsty. Since a large amount of water is lost through the urine, the individual will experience dehydration if they do not drink enough water every day. ### Hypothyroidism An adult will experience hypothyroidism if there is inadequate thyroxine secretion. Symptoms include extremely slow heartbeat, extremely sensitive to cold, tiredness and gain weight easily. ### Hyperthyroidism Hyperthyroidism refers to a situation that occurs when too much thyroxine is secreted. Symptoms include excessive sweating, heat intolerance, increased frequency of defaecation, fear, heart palpitations and weight loss. Sometimes, the thyroid gland will grow two or three times larger than its original size. ### Gigantism Excessive secretion of the growth hormone (GH) during childhood causes gigantism which is a condition characterised by the abnormal elongation of bones. The individual grows to become extremely tall. ### Dwarfism Low secretion of the growth hormone (GH) during the period of growth delays the growth of bones and causes a condition called dwarfism. Organs also fail to develop and parts of the body ratio remain as that of a child.