biology paper 2

• what does the human nervous system contain of


  -CNS: brain and spinal cord

  -PNS: all nerves in body
• what is the pathway through the nervous system

  -stimulus → receptor → coordinator → effector → response
• what is the CNS


  -coordinator that coordinates the response of effectors which may be muscles contracting or glands secreting hormones
• what does the nervous system do 


  enables humans to react to their surroundings and to coordinate their behaviour
• what are the 3 neurones in a reflex arc 


  sensory, relay, motor
• what are the adaptations of these 3 neurones? (what do they do)


  -sensory: carry impulses from sense organs to the CNS

  -relay:  found inside the CNS and connect sensory and motor neurones

  -motor: carry impulses from the CNS to effectors 
• what does a sensory neurone look like


   long and have a cell body branching off the middle of the axon
• what does a motor neurone look like


  -long and have a large cell body at one end with long dendrites branching off it
• what does a relay neurone look like


  -short and have a small cell body at one end with many dendrites branching off it
• what is a synpase

  -the gap between 2 neurones which release a chemical called neurotransmitters

  -in a reflex arc there is a synapse between sensory and relay neurones, and the relay and motor neurones

  -the neurotransmitters are released into the synaptic cleft and diffuse across it
• what is the process of diffusion of a neurotransmitter 


  -impulse arrives at end of presynaptic neurone

  -vesicles move towards + fuse with presynaptic membrane, releases chemical into synaptic cleft

  -neurotransmitters diffuse across synaptic cleft

  -neurotransmitters attach to receptors on postsynaptic membrane

  -this triggers an impulse alone neurone
• what can frequent drugs lead to for ur neurones


   overstimulation of neurones, leading to loss of function or overstimulation of different regions of the brain and body
• why do doctors prescribe drugs as medicine

  can bind to neurotransmitter receptors, triggering impulses in different regions of the brain
• what is reaction time 


  time taken to respond to a stimulus; reactions are usually very quick responses typically taking less than a second to occur
• what can reaction time be affected by 


  age, stress or use of drugs (such as caffeine)
• how do you do the reaction time practical


  -requires 2 people

  -person 1 sits down with an upright posture and places their forearm across a table (dominant arm) with hand overhanging the edge

  -person 2 stands up: holds ruler vertically and the 0cm mark should be between person 1s thumb and first finger

  -person 2 drops the ruler at a random time at the same consistent height while person 1 catches it as fast as they can with thumb + first finger

  -record measurement (level with person 1s thumb) and repeat several time

  -convert results to reaction time using a conversion table
• what are the different variables in the reaction time practical 


  -independent= (change), person having reaction time tested

  -dependent= (measure), reaction time

  -control = (same), starting distance between thumb+ first finger, measure ruler top of thumb, conditions of room the same eg. lighting and background noise
• what are the different regions of the brain

  -cerebral cortex

  -cerebellum

  -medulla
• what does the cerebral cortex of the brain control


  -outer layer of the brain which is divided into two hemispheres. It’s highly folded and is responsible for higher-order processes such as intelligence, memory, consciousness and personality
• what does the cerebellum of the brain control


  -underneath the cerebral cortex and is responsible for balance, muscle coordination and movement
• what does the medulla of the brain control


  - controls unconscious activities such as heart rate and breathing
• what are advantages/disadvantages of carrying out procedures on the brain/nervous system


  a:  improving the quality of someone’s life

  d: permanent damage
• what is body temp monitored/controlled by

  -thermoregulatory centre in the brain

  -contains receptors sensitive to the temperature of the blood

  -skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre
• how does the body respond to body temp


  too low: blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver)

  too high: blood vessels dilate (vasodilation) and sweat is produced from the sweat glands
• how does your body adapt itself when its temperature is too high and needs to decrease

  -heat loss by radiation

  -sweat glands excrete sweat which cools skin as it evaporates

  -vessels dilate to increase blood flow to skin

  -hair erector muscles will relax
• how does your body adapt itself when its temperature is too low and needs to increae


  -hair stands up which traps air around skin

  -trapped air is an excellent insulator

  -hair erector muscles will contract

  -vessels constrict reducing blood flow to the skin
• what is vasodilation


  -happens when the body temperature is too high

  -blood vessels close to the skin get wider (dilate) : allows excess heat to radiate from the blood into the environment
• what is vasoconstriction


  -happens when body temperature is too low

  -blood vessels close to the skin get narrower (constrict) :  reduces heat loss from the blood into the environment
• what is glucose monitored by

  pancreas
• what is type 1 diabetes


  disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels
• what is type 2 diabetes


   body cells no longer respond to insulin produced by the pancreas - the person still makes insulin but their cells are resistant to it and don’t respond as well as they should
• how do you treat type 1 diabetes


  -monitor blood glucose levels

  -injecting insulin throughout the day
• how do you treat type 2 diabetes


  -maintain low carbohydrate diet

  -exercise regularly
• when is insulin produced


  when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored – this reduces the blood glucose level
• when is Glucagon produced


  -when blood glucose falls too low and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the bloodstream – this increases the blood glucose level
• what is the main male reproductive hormone

  -testosterone which is produced by the testes
• what is the main female reproductive hormone

  -oestrogen which is produced by the ovaries
• what are the stages of the menstrual cycle


  -Menstruation – loss of lining from the uterus, occurs at the start of the cycle if no fertilisation has occurred

  -lining starts to thicken

  -ovulation occurs around the middle of the cycle (about day 14), the egg travels down the oviduct towards the uterus

  -lining is maintained ready to accept a fertilized egg
• what are the main hormones in the menstrual cycle

  -FSH

  -LH
• what are the different types of contraception


  -chemical

  -natural

  -barrier

  -surgical