14. Coordination and response

• Nerve impulse: an electrical signal that passes along nerve cells called neurons
• Human control system:

  • central nervous system (brain and spinal cord)
  • peripheral system (eye)
  • coordination and regulation of body functions
• Order of nervous reaction:

  1. stimulus - a change in the surrounding
  2. sensory receptor - detect a stimulus
  3. sensory neurone - conduct the electrical impulse from the receptor to the CNS
  4. CNS - contains brain an spinal cord & processes the information to decide on response
  5. motor neurone - conducts electrical impulse from the CNS to effector
  6. effectors - muscle/gland that carries out a response to make a change
• Reflex arc - occurs quicker than normal reactions in emergency where the impulse would be carried by a relay neurone

  • synapse ensure that impulse travel in one direction
• Voluntary response:

  • make a decision of the action (so start with brain)
  • slow process

  Involuntary response:

  • fast process
  • in an emergency - help minimise damage to the body
  • does not involve brain
• Synapse - a junction between two neurones
• Transfer of impulse between neurones

  A) 1. Neurotransmitter - chemical messenger

  B) 2. Vesicle - storage of neurotransmitter

  C) 3. Synapse - a junction between two neurones

  D) 4. Receptor - binds with neurotransmitter

  
• Transfer of impulse through neuruones:

  • nerve impulse arrives at pre-synaptic neurone
  • neurotransmitter is release into synapse
  • neurotransmitter diffuses across synapse
  • then binds with receptor on membrane of post-synaptic neurone
  • binding stimulate impulse on post-synaptic neurone
• Reflex arc:

  A) 1. Stimulus

  B) 2. Receptor

  C) 3. sensory

  D) 4. Relay

  E) 5. Motor

  F) 6. Effector

  
• Effect of drugs on synapse:

  • inhibit the release of neurotransmitter
  • binds with receptor instead of neurotransmitter (no impulse is stimulated = no action will be carried out)
• Sense organs - groups of receptor cells responding to specific stimuli: light, sound, touch, chemicals and temperature
• Pupil reflex:

  Low light intensity:

  • circular muscles are relaxed
  • radial muscle contract
  • pupil dilated to let more light in

  High light intensity:

  • circular muscle contract
  • radial muscle are relaxed
  • pupil constricted to prevent high amount of light in (prevent damage to retina)
• Distribution of rods and cones:

  • more rod cells than cone cells
  • no rod/cone cell at blind spot as optic nerve is located there
• Fovea - part of retina where receptors cells are pushed most closely together
• Accommodation (adjusting for near and distant objects):

  Near object:

  • ciliary muscle contract
  • suspensory ligaments slack
  • lens become short and fat

  Distant objects:

  • ciliary muscle relax
  • suspensory muscle tighten
  • lens become long and thin
• Hormone - chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
• Adrenaline - hormone secreted in 'fight' or 'flight' response (e.g. bungee jumping, riding a roller coaster)

  • pulse rate, heart rate and pupil diameter increases
  • increase blood glucose concentration for respiration
• Endocrine system:

  • adrenal gland (on top of kidneys that help regulates metabolism, immune system): adrenaline
  • pancreas: insulin and glucagon
  • testes: testosterone (development of male sexual characteristic)
  • ovary: oestrogen (development of female sexual characteristic)
• Homeostasis - the maintenance of a constant internal environment despite changes in the surrounding
• Nervous system:

  • very rapid responses
  • electrical impulse
  • duration: usually within seconds
  • effect usually in one area

  Endocrine system:

  • responses can be slow
  • chemical messengers (hormone)
  • duration: may take years (puberty)
  • widespread response
• Glycogen - stored form of glucose made from connected glucose molecules
• Glucoregulation:

  • receptors detect change in blood glucose concentration
  • insulin: secreted when blood glucose level rises --> extra glucose turns into glycogen in the liver
  • glucagon: secreted when blood glucose level falls --> glycogen converts into glucose in the liver

  Type 1 diabetes:

  • cause by death of cells that create insulin
  • symptoms: dry mouth, blurred vision, feeling thirsty, tired..
  • treatment: eating little/avoiding large amount of carbohydrates, injecting insulin
• Thermoregulation

  • receptors senses change in temperature and sensory neurons send signal to the brain (hypothalamus)

  Warm temperature:

  • vasodilation: arterioles (supply blood to capillaries) dilated to push it near to skin surface to increase heat loss
  • sweating: water evaporates, give cooling effect

  Cold temperature:

  • vasoconstriction: arterioles constrict which allow less blood to be near skin surface to reduce heat loss
  • insulation by fats
  • hairs stand up to create a layer and trap in heat
  • shivering: muscular activity to generate heat
• Negative feedback - a process that acts to reduce the changes of the process itself and restores systems to their original level

  • hypothalamus causes pituitary gland to release TSH
  • TSH stimulates thyroid gland to release thyroxine
  • thyroxine causes metabolic rate to increase -> increase transfer of energy to cells
  • cells now have required amount of energy
• Phototropism - a response of a plant due light (positive: towards/ negative: away)
• Gravitropism - the response of a plant due to gravity (positive: towards/ negative: away)
• Auxin - plant hormones that enables growth towards or away from a stimulus (produce in tip of shoots and roots)
• Positive phototropism:

  • auxin accumulate(concentrated) on shaded side of plant
  • auxin cause cells to be elongated
  • side with auxin increase in length causing shoot to bend towards light
• Positive gravitropism:

  • auxin accumulate on unshaded side of root - shaded side to elongate
  • causes roots to grow downwards
• Vasoconstriction/dilation

  A) Hair

  B) Arterioles

  C) Sweat gland

  
• The Eye:

  A) Cornea - refract light

  B) Iris - control amount of light enetering pupil

  C) Lens - focus light on retina

  D) Retina - contain light receptor (rod & cones)

  E) Optic nerve - carries impulse to brain

  F) Blind spot - no light sensitive cells