Nervous System
-We have 2 parts in our nervous system:
The central nervous system (CNS) is the nerves in our brain and spinal chord.
The peripheral nervous system (PNS) is a network of nerve cells in the rest of our body.
-Our nervous system detects stimuli and allows us to react to them.
-Stimulus: a change, action or occurrence in the environment that can cause an organism to respond. Eg. Light, noise, pressure…
How do we detect stimuli?
-We have sensory organs that detect particular stimuli eg. Skin
What happens after we have detected a stimulus?
1. An impulse (electrical message) is sent from the sense organ receptors to our CNS. This impulse travels along a sensory neurone.
2. The CNS co-ordinates a response and sends an impulse to an effector (organ or gland) that brings about a response. This impulse travels along a motor neurone.
Are we always aware of our responses?
-Some actions are voluntary eg. Calling someone’s name; we are conscious we are doing them and we feel in control of these actions.
-Other actions are involuntary eg. Digestion; we aren’t conscious of doing them and they continue even in our sleep.
Sensory neurones:
-When we detect a stimulus our sense receptors send an impulse along sensory neurones.
-Sensory neurones have branched dendrites and a long axon.
-The axon is insulated by a fatty material called a myelin sheath. It needs insulation because ‘electricity’ goes through it.
-The cell body is found midway along the long axon.
-The direction of movement of the impulse is always from the sense organ to the CNS.
Motor neurones:
-The dendrites of a motor neuron are connected to the cell body at one end of the nerve cell (which is connected to the CNS)
-The long axon (insulated too by myelin sheath) ends at muscle fibres to allow a response
-The direction of movement is always from the CNS to the effector.
Reflex responses:
-They are fast and automatic
-They are defensive (protect your body)
-Reflex arc: the
The central nervous system (CNS) is the nerves in our brain and spinal chord.
The peripheral nervous system (PNS) is a network of nerve cells in the rest of our body.
-Our nervous system detects stimuli and allows us to react to them.
-Stimulus: a change, action or occurrence in the environment that can cause an organism to respond. Eg. Light, noise, pressure…
How do we detect stimuli?
-We have sensory organs that detect particular stimuli eg. Skin
What happens after we have detected a stimulus?
1. An impulse (electrical message) is sent from the sense organ receptors to our CNS. This impulse travels along a sensory neurone.
2. The CNS co-ordinates a response and sends an impulse to an effector (organ or gland) that brings about a response. This impulse travels along a motor neurone.
Are we always aware of our responses?
-Some actions are voluntary eg. Calling someone’s name; we are conscious we are doing them and we feel in control of these actions.
-Other actions are involuntary eg. Digestion; we aren’t conscious of doing them and they continue even in our sleep.
Sensory neurones:
-When we detect a stimulus our sense receptors send an impulse along sensory neurones.
-Sensory neurones have branched dendrites and a long axon.
-The axon is insulated by a fatty material called a myelin sheath. It needs insulation because ‘electricity’ goes through it.
-The cell body is found midway along the long axon.
-The direction of movement of the impulse is always from the sense organ to the CNS.
Motor neurones:
-The dendrites of a motor neuron are connected to the cell body at one end of the nerve cell (which is connected to the CNS)
-The long axon (insulated too by myelin sheath) ends at muscle fibres to allow a response
-The direction of movement is always from the CNS to the effector.
Reflex responses:
-They are fast and automatic
-They are defensive (protect your body)
-Reflex arc: the