Control and Coordination

• Synapse


  A minute junction between the nerve endings of one neuron and the dendrites of another neuron where signals are transmitted
• Receptors and effectors

  Receptors are cells in a sense organ sensitive to a stimulus, while effectors are parts of the body that respond to a stimulus according to instructions from the nervous system
• Stimulus


  Any change in the internal or external environment of an organism which generates a response
• How effectors or muscles cause movement

  Neurotransmitters released in neuromuscular junctions from nerve endings of the neuron stimulate muscle cells, causing them to contract due to the movement of special contractile protein filaments. When these filaments return to their original position, the muscle cells relax
• Structure of Neuron

  • Cell Body (Cyton) - It has a well-defined nucleus and granular cytoplasm. It helps to pass the information acquired at the dendritic tip to the axon.
  • Dendrites - Branched projections of the cell body where information in the form of impulse is acquired.
  • Axon - A long process of the cell body with end portions having swollen bulb-like structures storing neurotransmitters. Impulse travels across its length until it reaches the nerve endings where certain chemicals are released into the synapse
• Transmission of Nerve Impulse

  The receptor in a sense organ is in touch with the dendrites of a sensory neuron. When a stimulus acts on the receptor, a chemical reaction is set off which produces an electrical impulse. This impulse travels through the neuron and reaches the nerve endings, causing the release of neurotransmitters at nerve endings which cross the synapse to reach dendrites of the next neuron. This process continues till the electrical impulse reaches the spinal cord and brain
• Types of neurons

  • Sensory neuron
  • Motor neuron
  • Association or relay neuron
• Spinal nerves

  • There are 31 pairs of spinal nerves
• Components of Peripheral nervous system

  • Voluntary
  • Involuntary
• Functions of spinal cord

  1. Conducts sensory impulse from skin and muscle to the brain

  2. Conducts motor responses from the brain to the muscles of the trunk and limbs

  3. Controls reflexes below the neck region

  4. Centre of reflex action
• The meninges cover the brain and help in protecting it. The space between these membranes is filled with cerebrospinal fluid
• Voluntary system is composed of cranial nerves and spinal nerves
• Parts of Human Brain


  • Forebrain
  • Mid Brain
  • Hind Brain
• Reflex action is an unconscious and involuntary response of an effector to a stimulus
• Muscle contraction and relaxation

  Muscle cells contract due to the movement of special contractile protein filaments present in them. When these filaments go back to their original position, the muscle cells relax
• Human brain is a highly complex organ located inside the skull called cranium, mainly composed of nervous tissue
• Cranial nerves

  • There are 12 pairs of cranial nerves. They come out of the brain and go to sense organs and other parts of the head region
• Cranium functions to protect the brain from mechanical shock
• Hormones are chemical substances secreted by glands to coordinate the activities of living organisms and their growth, made inside the body in small amounts
• The spinal cord is a long narrow cable of nervous tissue that extends from the base of the brain till the lower back, protected by the vertebral column, meninges, and CSF like the brain
• Human nervous system can be divided into two parts: Peripheral Nervous system and Central nervous system
• Hormones are made inside the body of an organism in very small amounts
• Glands like pancreas, testes, and ovaries perform functions of both exocrine and endocrine glands
• Hormones in plants affect the growth of the plant and can result in the movement of plant parts like shoot or root
• Various endocrine glands and their secretions/hormones

  • Pituitary gland - Growth hormone (GH) - Stimulates growth of the bones
  • Hypothalamus - Releasing hormone - Acts on pituitary gland to stimulate other glands
  • Thyroid Gland - Thyroxine - Controls general metabolism and growth in the body
  • Parathyroid - Parathyroid hormone - Controls the calcium levels in the body
  • Adrenal gland - Adrenaline - Prepares the body for emergency situations
  • Pancreas - Insulin - Controls blood sugar level
  • Testis (male) - Testosterone - Sperm production, development of secondary sexual characters in males
  • Ovary (female) - Oestrogen - Egg production, development of secondary sexual characters in females
  • Ovary (female) - Progesterone - Maintenance of pregnancy, release of ovum, maintenance of menstrual cycle
• Plants coordinate their behavior against environmental changes by using hormones
• Hormones


  Chemical substances secreted by glands which coordinate the activities of living organisms and their growth
• Types of tropic movements

  • Geotropism - Gravity - Roots of a plant growing downwards (positive geotropism), shoot of a plant growing upwards (negative geotropism)
• Characteristics of hormones

  • The hormones are secreted in very small amounts by endocrine glands
  • They are poured directly into the blood and carried throughout the body by the circulatory system
  • The hormones have their effect at a site different from where they are made
  • The hormones act on specific organs called target organs
  • The hormones coordinate the activities of the body and its growth
• Regulation of hormone production by feedback mechanism

  1. The over secretion or under secretion of any gland causes harmful effects in our body

  2. Feedback mechanism regulates the production and release of hormones
• Tropic Movements


  Movements in plants towards or away from a stimulus associated with growth
• Ethylene

  • Gaseous hormone important for ripening of fruits
• Photonasty


  • Non-directional movement of plant parts in response to light
• At the synapse between two neurons, the electrical impulse triggers a chemical reaction
• Thigmonasty


  • Twining of tendrils around a support
• Walking is a voluntary action, controlled by the brain
• Photonasty is the non-directional movement of plant parts in response to light
• Half of the cells become flaccid due to loss of water when a leaf is touched, causing the leaves to fold and droop down
• Nastic Movements

  1. Non-directional, quick, temporary, reversible movements of organisms in response to environmental stimuli like light, water, touch etc.

  2. May or may not be growth related

  3. Take place due to change in turgor pressure in the cells
• Thigmonasty is the non-directional movement of a plant part in response to touch