Coordination and control

• homeostasis is the maintenance of a constant internal environment despite changes in the external environment
• the pituitary gland releases hormones and controls several other glands in the body
• the hypothalamus monitors the conditions inside the body
• a negative feedback loop causes a counteracting response if the system deviates too far from the set point
• a positive feedback loop intensifies a response until an endpoint is reached
• vasoconstriction is when the blood vessels near the skin's surface contract to limit the amount of blood near the skin's surface so less heat will be lost
• vasodilation is when the blood vessels near the skin's surface dilate so the heat is able to leave the body, therefore bringing the body's temperature down
• sweating helps regulate body temperature as the heat found in the blood moves to the sweat and it absorbs enough heat until it evaporates, cooling the body down.
• piloerection is when the muscles at the base of your hand contract to cause the hairs to stand up. The hairs trap a layer of insulating air close to the body to prevent further heat loss
• shivering is involuntary contractions of the body's muscles. Whenever chemical reactions happen in the body, heat is produced, warming the body's temperature up.
• hormones are chemical messengers that travel through the bloodstream to the target cell. The target cell will have a specific receptor that the hormones bind to.
• adrenal glands release adrenaline
• adrenaline is a hormone that increases the heart rate and blood pressure to prepare the body to fight the danger or run away from it.
• the pancreas releases glucagon if the glucose levels are too low and insulin when the glucose levels are too high
• glucagon travels to the liver and binds to its receptors. this causes the liver to release the converted glucose from stored glycogen into the bloodstream, increasing the blood glucose levels
• insulin travels to the liver and binds to its receptors. This causes the liver to store glucose as glycogen, decreasing the glucose levels in the body
• the CNS is the central nervous system, which is made up of the brain and spinal cord
• the PNS is all the nerves throughout your body
• the CNS sends and receives messages to and from the PNS
• the PNS receives messages from the CNS to undertake actions and also sends messages to the CNS based on stimuli
• sensory neurons are neurons that transmit messages from the body to the CNS
• relay or interneurons process the information transmitted by the PNS and determine the response
• motor neurons carry messages away from the brain to the effector
• dendrites carry nerve impulses from the neighbouring neurons to the cell body
• the cell body contains the majority of nerve cell's organelles
• the nucleus contains the DNA (genetic information) and controls the cell's functions
• the axon carries the nerve impulses away from the cell body to the axon terminals
• the myelin sheath protects the axon, insulates the axon and speeds up the message
• the node of ranvier speed up the transmission of the nerve impulse by forcing them to jump across the gaps
• the axon terminals contain neurotransmitters that carry the message across the synapse to the next neuron
• receptors detect and recieve the stimulus
• organ - eye

  stimulus - light

  receptor - motor receptor
• organ - earstimulus - sound wavesreceptor - auditory receptor
• organ - skin

  stimulus - pressure

  receptor - pain/pressure receptor
• organ - skin hypothalamus

  stimulus - heat

  receptor - thermoreceptor
• organ - nose

  stimulus - chemicals

  receptor - chemoreceptor
• organ - tongue

  stimulus - chemicals

  receptor - chemoreceptor
• receptors detect the stimulus and send signals to the brain
• effectors is any part of the body that produce a response
• synapse

  1. an electrical impulse travels along an axon
  2. the impulse triggers the pre-synaptic neuron to release chemical messengers called the neurotransmitters out of the vesicles
  3. these chemicals diffuse across the synapse and bind to a receptor on the dendrites on the post-synaptic neuron
  4. this stimulates an electrical impulse in the the second neuron