Chapter 10 - The human nervous system Flashcards
What do enzymes and cells require to work and how do our bodies help this?
Very stable conditions - they cannot work well if the conditions around them change too much. There are systems our bodies have in place in order to keep internal conditions optimum for cells to function - scientists call this homeostasis.
Homeostasis definition
The regulation of internal conditions in a cell or organism to maintain optimum conditions for function in response to internal and external changes.
What is meant by internal conditions?
E.g. blood glucose concentration, body temperature, water levels - homeostasis is used to keep these constant
What does homeostasis consist of?
Automatic control systems making sure that the internal conditions in the body stay as constant as possible.
What can the automatic control systems in a human body involve?
The nervous system or hormones.
Describe the general features of an automatic control system.
- RECEPTOR cells detect changes in the environment (the body’s internal conditions e.g. concentration of glucose in the blood or external conditions e.g. temperature of skin).
- Scientists call a change to the environment a STIMULUS.
- The receptor cells now pass the information onto a CO-ORDINATION CENTRE (e.g. the brain, the spinal cord or the pancreas).
- The co-ordination centre receives and processes the information from the receptor cells.
- The co-ordination centre now sends the information to an EFFECTOR (a muscle or gland).
- The job of the effector is to carry out the RESPONSE, in other words restore the optimum level.
What are the two parts of the nervous system?
- The central nervous system: the brain and the spinal cord.
- The peripheral nervous system: nerves that branch out of the spinal cord and extend to all parts of the body.
How does homeostasis work in the nervous system?
- Receptors detect a stimulus…
- …and send electrical impulses down neurones (nerve cells) to the central nervous system.
- CNS = co-ordination centre.
- This then sends electrical impulses down other neurones to effectors, which then bring about a response.
What are effectors usually (in homeostasis of the nervous system)?
A muscle that contracts, or a gland that secretes a hormone.
What is a key role of the nervous system?
Enables humans to react to their surroundings and co-ordinate their behaviour.
What is one way that the key roles are carried out?
Through the reflex arc.
What happens when you touch a hot object?
- The stimulus (heat) is detected by a receptor (in the skin).
- Electrical impulses now pass from the receptor along a sensory neurone to the central nervous system. (Remember that sensory neurones are connected to receptors, and receptors allow us to sense our environment).
- At the end of the sensory neurone is a junction called a synapse.
- At the synapse, a chemical is released.
- The chemical now diffuses to a relay neurone in the central nervous system, where it triggers an electrical impulse.
- The electrical impulse now travels across the relay neurone, and reaches another synapse.
- Once again a chemical is released.
- This chemical triggers an electrical impulse in a motor neurone.
- The electrical impulse now passes down the motor neurone to an effector (in this case a muscle).
- The muscle now contracts and pulls the hand away from the heat - the response.
What is different (regarding the brain) in reflex arcs in comparison to most cases of homeostasis in the nervous system?
- As the CNS acts as the co-ordinator, the brain, in most cases, decides what action to take.
- However in the case of reflexes, there is no decision making by the conscious part of the brain.
- This makes reflexes automatic and rapid - because they are rapid, they are able to protect us from danger.
What critical role does the brain take on in the central nervous system and how does it do it?
Controlling complex behaviour, e.g. language. To do that, it contains billions of interconnected neurones.
What is the highly folded, outer part of the brain called?
The cerebral cortex.
What are the functions of the cerebral cortex?
Language, memory and consciousness.
What is that silly little bulge below and to the right of the cerebral cortex called?
The cerebellum.
What are the functions of the cerebellum?
Controls our balance and co-ordinates our movements.
What is the slightly penis shaped, tube-like thing called?
The medulla.
What are the functions of the medulla?
Controls our heart rate and our breathing rate.
Why is studying the brain/treating brain diseases/damage difficult?
- Protected by the skull, so very tricky to access.
- Structures of the brain are extremely complex, so it is difficult to work out exactly which parts of the brain carry out specific functions.
- The brain is extremely delicate and easy to damage.
Three ways scientists investigate the brain:
- Looking at patients who have suffered brain damage: by looking at where the damage has taken place, they can try and link that part of the brain to its function.
- Electrically stimulating different parts of the brain and looking at the effects on the person’s behaviour - allows specific regions to be narrowed down to their functions.
- MRI scanning to see what parts of the brain are most active during different activities (e.g. when someone is looking at images, image processing parts of the brain are most active).
