homeostasis and response

• homeostasis is the regulation of the internal conditions for a cell or organism to maintain optimum conditions for function in response to internal and external changes.
• 3 internal conditions that homeostasis regulates:

  blood glucose concentration, body temperature, water levels
• internal conditions refer to the conditions inside the body, such as body temperature. external conditions refer to the conditions outside the body, such as room temperature.
• a receptor detects stimuli (a change in the internal or external environment)
• coordination centres (such as the brain, spinal cord and pancreas) receive and process information from receptors
• coordination centres are located in the:

  brain, spinal cord, pancreas
• effectors, such as muscles or glands, bring about responses which restore optimum levels.
• what are the 2 types of effectors and what do they do when stimulated?

  1. muscles - contract 2. Glands - secrete hormones
• the nervous system is a complex network of nerves that carry messages from the brain and spinal cord to and from various parts of the body.
• the nervous system enables humans to react to their surroundings and to coordinate their behaviour
• the endocrine system is made up of glands that release hormones. these hormones act as chemical messengers that allow communication throughout the body
• your automatic control systems keep your internal environment stable using a mechanism called negative feedback. when the level of something, e.g temperature, gets too high or too low, your body uses negative feedback to bring it back to normal.
• the nervous system uses electrical signalling (neural impulses) whilst the endocrine system uses chemical signalling (hormones, produced by glands)
• what type of cells make up the nervous system?

  Neurones (nerve cells)
• what is the central nervous system (CNS) composed of?

  Brain and spinal cord
• what passes along nerve cells?

  Electrical signals
• what is the gap between nerve cells called?

  Synapse
• how does a synapse transmit an electrical signal?

  when an electrical impulse reaches the end of a neurone, it causes the release of chemicals (neurotransmitters). these chemicals then diffuse across the synapse and stimulate the next neurone to carry another electrical impulse.
• a reflex is an automatic response to a stimulus
• reflex actions are fast because they are automatic and don't involve conscious parts of the brain
• it is important for reflexes to be rapid and automatic to protect us from harm
• stages of a reflex arc:

  stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
• what is the role of a receptor?

  to detect a stimulus
• what is the role of a sensory neurone?

  to transfer a signal from a receptor to the CNS
• what is the role of a relay neurone?


  to transfer a sign from a sensory neurone to a motor neurone
• what is the role of a motor neurone?

  to transfer a signal from the CNS to an effector
• the two main types of effectors are :

  muscles , glands
• the nervous system enables humans to react to their surroundings and to coordinate their behaviour
• information from receptors passes along the neurones as electrical impulses to the central nervous system. the CNS coordinates the response of effectors, which may be muscles contracting or glands secreting hormones.
• ohhhhhhhhhh who am I gonna call?

  who's gonna catch me when I- who's the one your sleeping with? DONT U SIT INFRONT OF ME AND WAIT FOR ME TO TALK U CAN CALL ME UP THE PHONE WORKS TWO WAYS YOU KNOW.
• the internal conditions of your body needs to be regulated to maintain the right conditions for cells to function properly and for enzymes to work (enzyme action)
• a reflex action is a rapid and automatic response to a stimulus, that doesn't involve the conscious part of the brain.
• someone touches a hot pan. a reflex reaction causes him to immediately move his hand away. describe the pathway of the reflex from stimulus to effector:

  the heat stimulus is detected by receptors in the hand, which send impulses along a sensory neurone to the CNS. the impulses are transferred to a relay neurone. they are then transferred to a motor neurone and travel along it to the effector (muscle - causing it to contract)
• the cerebral cortex is the wrinkly, outer layer of the brain and is responsible for the higher-level processes of the human brain, including:


  consciousness, intelligence, memory, language, reasoning, decision-making, senses
• the cerebellum is responsible for muscle coordination, balance and posture , and is located in the back of the brain.
• the medulla controls unconscious activities such as breathing and heart rate. it exists within the brain stem.
• the hypothalamus has a role in homeostasis, such as regulating our temperature and water levels
• 3 ways scientists can study the brain:

  1)studying patients with brain damage. 2)electrically stimulating different parts of the brain. 3)MRI scans
• why is treating the brain so difficult?

  1)it is complex 2)it is delicate 3)it is encased with a skull, so hard to access 4)there a huge range of things that can go wrong - like infection, trauma, mental illness, tumours
• the eye is a sense organ containing receptors sensitive to light intensity and colour