What does CNS consist of and what is its job?
- the central nervous system’s job is to coordinate the information
- it consists of the brain and spinal cord
How do we respond to things?
- stimulus (a change in your environment)
- receptor
- sensory neuron
- CNS
- motor neuron
- effector (muscle or gland)
- response
What are reflex actions and how do they work?
- reflex actions are unconscious reactions that stop people from getting hurt.
- the conscious brain isn’t involved in the reflex arc.
- the sensory neuron connect to the relay neuron in the spinal cord, which links directly to the right motor neuron.
- stimulus, receptor, sensory neuron, relay neuron, motor neuron, effector, response
What are neurons?
- nerve cells
- neurons transmit information around the body as electrical impulses
What does a typical motor neuron consist of?
- cell body
- nucleus
- axon
- dendrites (branched ending)
- insulating sheath
- synapse
How are neurons adapted to send messages quickly?
- dendrites connect to lots of other neurons
- the sheath acts as an electrical insulator, it causes the impulse to jump (over it), which speeds up the electrical impulse
- the axon (they are) long, one long neuron is quicker that lots of shot ones joined together as connecting with another neuron slows the impulse down.
What is a synapse and how are impulses sent across them?
- a synapse is the connection between two neurons
- the electric impulse triggers the release of neurotransmitter chemicals which diffuse across the gap and bind with the receptor molecules in the membrane of the next neuron.
- this sets off a new electrical impulse
What do depressants work?
-by binding with the receptor molecules on the membrane of the neuron blocking the electrical impulse. This decreases brain activity.
How do stimulants work?
-by increasing the amount of neurotransmitter chemical at some synapses, which increases the frequency of impulses along the next neuron.
What is homeostasis?
maintaining a constant internal environment.
What is negative feedback?
- a response triggered by changes in the environment to counteract the changes, e.g. a rise in temperature cause a response that lowers the body temperature
- therefore the internal environment tends to stay around the norm (the level at which the cells work best)
- if the environment changes too much the it might not be possible to counteract it.
What does our body do if we are too hot?
- hairs lie flat
- lots of sweat is produced (when sweat evaporates it uses heat energy from the skin. This transfers heat from your skin the environment, cooling you down)
- vasodilation (blood vessels close to the skin widen to allow more blood to flow near the surface, to radiate more heat to the surrounding)
What does our body do if we are too cold?
- hairs stand on end to trap an insulating layer of air which helps keep you warm
- very little sweat produced
- vasoconstriction (blood vessels near the surface constrict so less heat is transferred to the surroundings)
- shivering generates heat in the muscles
How is body temperature controlled?
- the optimum temperature for enzymes in the human body is 37.
- there is a thermoregulatory centre in the brain
- it contains blood temperature sensitive receptors and receives skin temperature information from the skin.
- the brain can respond to the changes and change the body temperature using nervous and hormonal systems to initiate temperature control systems.
