Homeostasis and response

• What is internal environment?

  The conditions inside your body
• Define homeostasis


  The regulation of internal conditions of cells to maintain optimum conditions for functioning in response to internal & external changesE.G. body temp is maintained at 37 degrees even if we are in extreme cold/hot environment
• Why is homeostasis important?

  -It is important as your cells need to be in the right condition to function properly
• state three ways in which your external environment may vary

  Changes in:-temperature-levels of sunlight-levels of wind
• What are three internal conditions that are controlled by homeostasis in your body?

  1. Blood glucose concentration2. Body temperature3. Water levels
• Name, define and explain what the three main components in automatic control systems include/do

  1. Receptors- cells which detect stimuli (changes in environment)- they send information through electrical impulses to CNS via sensory neurone2. Coordination centre- areas that receive information from receptors and coordinate a response e.g. CNS-brain, spinal chord- motor neurones carry electrical impulses from CNS to effector3. Effectors- muscle or glands that bring about responses which restore conditions in body to optimum levels- muscles respond to arrival of impulses by contracting & glands respond by secreting chemical substances
• Describe and explain the two types of communication systems in your automatic control systems which regulate the internal environment

  -Nervous communication system- fast electrical impulses sent through nerves which allows us to respond to things very quickly-from nervous system-Hormonal communication system- hormones/chemicals released in bloodstream to bring about a particular change or effect to cell- from endocrine system
• What is the central nervous system (CNS) and what is it made up of?

  -It's a coordination centre where it receives info from receptors and coordinates a response -It is made up of the brain and spinal chord
• What are neurones?

  Nerve cells which send messages all over your body
• What do the sensory and motor neurones do?

  Sensory neurones- neurones that carry info as electrical impulses from receptors to coordination centre (CNS)Motor neurones- neurones that carry electrical impulses from coordination centre (CNS) to effectors
• What is the nervous system made up of?

  -CNS-sensory neurones-motor neurones-effectors
• What is the difference between a neurone and a nerve?

  Neurone: a single nerve cellNerve: bundle of hundred or thousand of neurones
• Evaluate the differences between the nervous communication system and the hormonal communication system

  Nervous communication system:-signal is sent by electrical impulses through neurones-speed of response is faster (allows us to respond to things very quickly)-duration of response is shorter (until nerve impulses stop)Hormonal communication system:-signal is sent by chemicals through bloodstream-speed of response is slower-duration of response is longer (until hormones are broken)
• How do you know if receptors send information to the brain or spinal chord in CNS?

  -information is sent by sensory neurones by receptors to brain if it is closer to brain or to spinal chord if it is closer to spinal chordE.G. if you stepped on broken glass it will go to spinal chord as shorter distance.
• Describe the adaptations of the nervous system

  1. Neurones contain lots of dendrites to make connections to other nerve cells2. Neurones have an axon that carries nerve impulses from one place to another3. The nerve endings/synapse contain lots of mitochondria to provide energy needed to make neurotransmitter chemicals to pass impulses to another cell in body
• Explain what happens in your nervous system when you see a piece of fruit, pick it up, and eat it (6marks)


  -Light receptors in your eye detects a stimulus (fruit). The receptors are then stimulated. Info produced by receptor cells is sent as an electrical impulse along sensory neurone to CNS-brain-The brain receives info from receptors and coordinates a response. Motor neurones then carry electrical impulses (info) from CNS to effectors-Effectors -muscles respond to arrival of impulses by contracting. In this case, muscles in your hand move & pick up fruit.-Your glands respond by secreting chemical substances. In this case, salivary glands produce extra saliva when you see/smell fruit & pancreas releases the hormone insulin when your blood sugar levels goes up after you eat it
• Why is the nervous system important?

  -It enables humans to react to their surroundings and to coordinate their behaviour in response to stimuli.
• Describe the function of the relay neurone

  Only found in the CNS & connects the sensory neurone to the motor neurone
• What does the synapse allow to do

  - It allows nerve cells to pass on their electrical impulse (information) to another nerve cell via chemicals
• Explain what the synapse is and what happens there


  -The gap/connection between 2 neurones is called a synapse-The electrical impulse (information) from a neurone is transferred to next neurone by neurotransmitter chemicals which is released & diffused across the synapse. The chemicals attach to surface of next neurone and sets up a new electrical impulse
• Describe fully what happens when you touch a hot pan and how this brings about a reflex action

  -The receptors in the skin detects a stimulus (hot pan). The receptors are then stimulated-Receptor cells then send info as electrical impulses to CNS-(spinal chord) via sensory neurone -Once electrical impulse reaches the end of sensory neurone it produces neurotransmitter chemicals which is released & diffused across synapse to relay neurone (in CNS) where it detects chemicals & reproduces impulse-When electrical impulse reaches the end of relay neurone it produces chemicals which is released & diffused across synapse to motor neurone where it detects chemicals & reproduces impulse travelling to effector-Once process happens again, impulse passes onto effector-muscle which contracts & moves away handNOTE: RELAY NEURONE IS ONLY INVOLVED IN REFLEX ACTIONS
• What 3 factors affect reaction time?

  -Age-Gender-Drugs
• Plan an investigation into the effect of a factor (caffeine) of a human reaction time (6marks)

  1. The person being tested should sit with their arm resting on the edge of the table (to stop them moving their arm during test)2. Hold a ruler vertically between their thumb and forefinger. Make sure the zero end of ruler is level with their thumb & finger. Then let go without giving any warning3. The person being tested should try to catch the ruler as quickly as they can- as soon as they see it fall4. Reaction time is measured by the number on the ruler where it's caught- the further down it's caught (higher number), the slower the reaction time5. Repeat test several time then calculate mean distance ruler fell6. The person being tested should have a caffeinated drink & should repeat the experiment after 10 mins
• What is the brain made up of?

  It's made up of billions of interconnected neurones (neurones that are connected together) that form different regions (medulla, cerebellum, etc) which carries out different functions
• Describe the functions of the cerebral cortex, cerebellum and the medulla in the brain

  Cerebral cortex: concerned with consciousness, memory, language & intelligenceCerebellum: concerned with coordination of muscular activity & balanceMedulla: concerned with unconscious activities such as breathing, controlling heartbeatNOTE: cerebral cortex is the outer layer that lies anywhere on top of cerebrum (brain)

  
• What is meant by the core body temperature?

  The temperature inside your body
• What is the function of the thermoregulatory centre?

  -It monitors and controls body temperature as it contains receptors sensitive to temperature change in blood
• Where is the thermoregulatory centre located in your body?

  -It is in the hypothalamus of the brain
• How have neuroscientists been able to map the regions of the brain to particular functions and why has it been difficult?


  -Neuroscientists have been able to map the regions of the brain to particular functions by:-studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques-The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult
• Describe how electrically stimulating different parts of the brain works to map the regions of the brain to their functions and describe how this surgery is done

  -Scientists remove the top part of the skull & stimulate different areas of the brain-As there are no sensory nerve endings in the brain, this brain surgery is done when patient is conscious -Therefore, patients can feel different emotions when relevant area of brain is stimulated
• Describe how MRI scans have been able to help scientists to develop a much better understanding of how the brain works

  -As if someone develops a tumour in their brain or has a stroke, this will affect their behaviour & an MRI scan will show which areas of the brain is affected -This enables scientists to link certain functions to different parts of brain
• State one reason why the brain cannot be treated with drugs

  -Drugs do not always reach the brain through the membrane which surrounds it
• What is the eye and what is it sensitive to?

  -It's a sense organ containing receptors sensitive to light intensity & colour
• What is the function of the pupil?

  -It allows light to enter the eye
• Where is the sclera located and what is it's function? (describe how it's adapted to it's function)

  -It's the white outer layer of the eye & is tough so the eyeball is not easy to damage

  
• Where is the cornea located and what is it's function? (describe how it's adapted to it's structure)

  -It's the clear (gel-like substance) which refracts the light rays coming into the eye to go through lens & hit retina-They have a curved surface which changes the direction of the light rays coming into the eye (make sure it's focused on retina) & they're transparent

  
• Where is the iris located and what is it's function? (describe how it's adapted to it's structure)

  -It's the coloured bit of the eye which controls size of the pupil-It's made of muscles that contracts or relaxes to change the size of the pupil hence control amount of light reaching retinaE.G. when very bright light, iris makes pupil very small

  
• Explain what needs to happen in order to make the pupil smaller (when it's directed to very bright light)

  -The circular muscles in the iris contract, making the pupil smaller-The radial muscles in the iris relax, so it can be stretched longer (to make pupil smaller)

  
• Explain what needs to happen in order to make the pupil larger (when it's directed to very dull bright)

  -The circular muscles in the iris relax, making the pupil larger-The radial muscles in the iris contract, so it can be stretched shorter (to make pupil larger)
• Where is the suspensory ligaments and the ciliary muscles located and what is it's function?


  -The suspensory ligaments & ciliary muscles holds lens in place (lens is used to refract light even more to create clear image on retina)