B10 - Nervous System Flashcards
What is homeostasis?
Maintaining a constant internal environment
What is homeostasis?
Maintaining a constant internal environment
• temperature (to ensure enzymes are at optimum)
• water (to maintain our osmotic balance)
• blood sugar (to release energy needed to survive)
Co-ordination (stimulus and response)
• all organisms sense and respond to changes in their environment to increase their chances of survival
• all responses to the environment require a receptor, a coordination and an effector
What is a stimulus?
• signal or change in the environment
What is a receptor?
cells that detect changes in the internal or external environment. These changes are known as stimuli. Receptors may be part of the nervous or the hormonal control systems of the body.
What are the coordination centres?
areas that receive and process the information from the receptors. They send out signals and coordinate the response of the body. They include the brain, which acts as a coordination centre for both the nervous system and parts of the hormonal system, the spinal cord, and some organs such as the pancreas.
What is the effector?
Organ that delivers the response, such as muscles and glands. Response will restore conditions in the body to optimum.
What is the response?
Increases survival chances
Components of the nervous system
• nerve impulses
• electrical signals
• travelling in nerves
• fast
• short - lived
Components of the endocrine system
• hormones
• chemical signals
• travelling in blood
• slow
• long-lasting
Sense/Sense Organ/Stimulus (sight)
• sight
• eye
• light
Sense/Sense Organ/Stimulus - Touch
• touch
• skin
• pressure/temp
Sense/Sense Organ/Stimulus - Hearing
Hearing
Ear
Sound
Sense/Sense Organ/Stimulus - taste
• Taste
• Mouth (tongue)
• chemicals in food
Sense/Sense Organ/Stimulus - smell
Smell
Nose
Chemicals in air
The Nervous System
• Central nervous system - made up of the brain and spinal chord
• Peripheral Nervous system - made up of sensory neurones and motor neurones
Structure of a motor neurone
• From CNS to effectors (muscles/glands)
• axon - transmits electrical impulse
• Myelin sheath around axon
• branched dendrites
• cell body inside branch dendrites area
Structure of a sensory neurone
• from sense organ to CNS
• branched dendrites
• myelin sheath
• cell body (separate from dendrites/smaller)
Myelin sheath function
• insulates axon
Dendrites function
• makes lots of connections with other neurones
Really sir couldn’t make it easier
• receptor
• sensory neurone
• coordinator
• motor neurone
• effector
Describe how a rabbit will respond to the presence of a fox
• Light reflects off the fox (stimulus)
• Eyes detect fox (receptor)
• nerve impulses sent to the brain (sensory neurones)
• brain decides to run (coordinator)
• nerve impulses sent to muscles (motor neurones)
• muscles contract (effector)
• rabbit runs away (response)
What is the purpose of a reflex?
• fast - shorter nervous pathway
• automatic/unconscious - doesn’t involve the brain
• protective response - increases our survival chances
Reflexes order
• stimulus
• receptor
• sensory neurone
• coordinator (relay neurone)
• motor neurone
• effector (muscle)
• spinal chord
• respond (hand moves)
Synapses
• gaps between neurones that electrical impulses cannot pass
• so chemicals called neurotransmitters pass the signal from neurone to neurone
• nerve impulses arrives at first neurone
• neurotransmitter released from vesicle
• neurotransmitter diffuses across synapse
• electrical impulse stimulated in next neurone
Measuring reaction times
• Drop ruler between someone’s fingers
• They catch it as quickly as possible
• measure distance ruler has travelled
• repeat 5 times
• calculate averages
reaction time = average distance / 490 and square rooted
Everyday bodily functions controlled by reflex actions?
• breathing and digestion
