2.84 - 2.85 Nerve impulses and responses

• Nerve impulses pass through the CNS and the effectors create a respons
• Electrical impulses
• Signals/impulses created by the receptors which are send to the coordinator
• Method of transporting information of environmental change from the receptors to the coordinators in order to produce a response 
• Decision making
• When receptors are affected by a change, they sends eletrical signals/impulses through the sensory nerves to the CNS
• The brain then coordinates the response 
• Reflex action

• Very rapid, uncoordinated movement
• Ex: Pulling your leg up after stepping on a lego block in the dark
• Pain receptors detects the lego
• Sensory Nerve sends the electrical signal (Impulse) to the CNS, Brain
• The Motor nerve sends signals to the effector (Skin)
• The effector (Skin) produces a response
• Reflex
• Muscle contracts
• Leg is pulled up

2.83 Central Nervous System (CNS)

• Allows the body to respond to any change in the environment
• Consist of:
• Brain
• Spinal cord
• All the nerves branching out from the cord
•  The CNS refers only to only the brain and the spinal cord
• Impulses from the receptors pass through the sensory nerves til they reach the spinal cord and te brain
• There are two ways in which the CSN handles these changes:
• Response coordinated by the brain 
• Slower
• Reflex action
• Extra rapid responses to stimuli that by-pass the brain

2.82 Communication

• Motor Nerve (Neurone)
• Links coordinators with effectors
• Around a meter long
• Has tiny branches at each end
• Has long fibers at each end
• To carry the electrical impulses from the cell body to the Synaptic  knob
• Connected to the muscle
• Mammals- The axon is surrounded by a scwhan cell
• Contains fat to increase the speed of the nerve conduction
• Endocrine System
• Endocrine Gland 
• Produces hormones
• Can be Proteins/Steroids
• Secreted in to the blood
• Arrives at the "Target organ/tissue"
• May have multiple targets
• May have multiple effects
• Endocrine gland (Adrenal gland) > Blood (Adrenaline) > Target Tissue (Heart)
•                                |Nerves                                    |Hormones                      
  Speed of reaction     | fast                                        |slow                              
  Type of transmission|Chemical signal                       |Electrochemical signal
• Specificity                |Can be a few/many body parts|Affects target cells/organs
  

Receptors

ThermoReceptors-Temperature
GeoReceptors-Gravity
PhotoReceptors-Light
ChemoReceptors-Chemical
MecanicReceptors-Touch

2.77b Thermoregulation

• Receptors-
• Transforms external energy into internal electrical impulses
• Controls body temperature
• Human enzymes:
• Woks best at 37-38 degrees
• Dangers of body temperature
• High: Heat stroke, dehydration
• Death if not treated
• Low: Hyperthermia
• Death if not treated
• The brain monitors the body's temperature
• When too cold/hot, the brain sends nerve impulses to the skin
• Has 3 ways of increasing or decreasing lost heat from the surface of the body
• Hair standing up - 
• Traps more warm air which reduces heat loss
• Less when lying flat
• Capillary network
• allows blood to move further away from skin
• Tiny muscles controls the hairs
• Sweat
• Glands under the skin secret when hot
• increases heat loss through evaporation
• When the body is back at normal temperature, the skin stops secreting
• Capillary network
• allows blood to move closer to the surface skin
• Blood vessels supplying blood to the skin can cause the skin to swell or dilate
• Hot Day-
• Vasodilation
• The blood vessels dilate (widen)
• Hairs are flat
• More heat is carried by the blood to the skin
• Can be lost to the air through sweat
• Cold Day-
• Vasoconstriction
• The blood vessels swell (shrink down)
• Hairs are raised
• Reduces heat loss
• Returns body temp back to normal

2.77a Thermoregulation

• Homeostatis
• Homeo- Same
• Statis- Conditions
• Same conditions
• Homeothermic
• Thermic- Temperature
• Same Temperature

2.76 Sensitivity

• Sensitivity- Response to changes in the environment
• Changes:
• Chemical Level
• Light Level
• Temperature Level
• Characteristics of life:
• Movement 
• Respire
• Senses
• Grow
• Reproduce
• Excrete 
• Nutrition
• Receptors/Effectors in organism
• Receptors- To detect to change
• Effectors- To respond to change
• Response- 
• Organism is able to survive these changes