The Nervous System Flashcards
Sense Organs Detect Stimuli.
What is Stimuli/Stimulus?
A stimulus is a change in your environment which you may need to react to (e.g. a grizzly bear looking at you.)
You need to be constantly monitoring what’s going on so you can respond if you need to.
What are your sense organs?
Ears, eyes, nose, tongue and skin
What are the receptors that your sense organs have?
Receptors are groups of cells which are sensitive to a stimulus. They change stimulus energy into electrical impulses. Stimulus can be light, sound, touch, pressure, chemical or a change in position or temperature
Eyes have light receptors - sensitive to light.
Ears have sound receptors - sensitive to sound.
Nose has smell receptors - sensitive to chemical stimuli.
Tongue has taste receptors - sensitive to bitter, salt, sweet and sour and savoury things. Chemical Stimuli.
Skin is sensitive to touch, pressure, pain and temperature change.
Define the Central Nervous System
The Central Nervous system is where all the information from the sense organs is sent, and where reflexes and actions are coordinated.
The Central Nervous system consists of the brain and spinal cord only.
Neurones transmit the information as electrical impulses very quickly to and from the CNS
“Instructions” from the CNS are sent to the effectors (muscles and glands) which respond accordingly
Describe what the Sensory Neurones, Relay Neurones, Motor Neurones and Effectors do?
Sensory Neurones: The Nerve cells that carry signals as electrical impulses from the receptors in the sense organs to the Central Nervous system.
Relay Neurones: The nerve cells that carry signals from sensory Neurones to the motor Neurones.
Motor Neurones: The Nerve cells that carry signals from the Central Nervous system to the effector muscles or glands.
Effectors: Muscles and glands are known as effectors - they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones.
Describe how Synapses connect Neurones
The connection between two neurones is called a synapse.
The Nerve signal is transferred by chemicals which diffuse (move) across the gap.
These chemicals then set off a new electrical signal in the next neurone.
What is a reflex?
Reflexes are automatic responses to certain Stimuli, reducing the chances of being injured.
For example, if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye. This stops them from getting damaged.
What is The Reflex Arc?
The passage of information in a reflex, from receptor to effector.
The Neurones in reflex arcs go through the spinal cord or an unconscious part of the brain.
Describe how the reflex arc goes through the CNS.
An example.
1) Bee stings finger
2) Stimulation of pain receptors
3) Message travels along a sensory neurone
4) Message is passed along a relay neurone
5) Message travels along a motor neurone
6) When Message reaches the muscle, it contracts and you pull your hand away.
Because you don’t have to think about the response (which takes time) it’s quicker than normal response
Stimulus, Receptor, Sensory Neurone, Relay Neurone, Motor Neurone, Effector, Response
Stimulus, Receptor, Sensory Neurone, Relay Neurone, Motor Neurone, Effector, Response
What is the Definition of Hormones
Hormones are chemical reactions which travel in the blood to activate target cells
What two places in the body produce Hormones?
The Pituitary gland - this produces FSH and LH which are involved in the menstrual cycle.
Ovaries - (females only) produce Oestrogen which is also involved in the menstrual cycle.
What are the important differences between Hormones and Nerves?
N - Very FAST message
H - SLOWER message
N - Act for a very SHORT TIME
H - Act for a LONG TIME
N - Act on a very PRECISE AREA
H - Act in a more GENERAL way
