B5 Homeostasis and response

Describe what is meant by homeostasis.

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

Why is homeostasis important?

Homeostasis maintains optimal conditions for enzyme action and all cell functions.

Homeostasis consists of automatic control systems; ensuring internal conditions of the body are kept as constant as possible.

Enzymes and cells require stable conditions to function.

If the conditions e.g. temperature change a lot, they may not be able to work.

Which conditions inside the human body does homeostasis control?

Body temperature

Blood glucose concentration

Water levels

Describe the general features of an automatic control system.

The automatic control systems may involve nervous responses or chemical responses (hormones).

1) Receptor cells detect change in the environment (this includes the body's internal conditions).

2) Receptor cells pass information onto a co-ordination centre e.g. the brain, spinal cord or pancreas

3) The co-ordination centre receives and processes the information and determines the appropriate response.

4) The co-ordination centre now sends instructions to the effector e.g. muscle or gland.

5) The effector carries out the response and restores the optimum level.

Define stimulus.

A stimulus is a detectable change in the internal or external environment.

What is the function of a receptor cell?

To detect stimuli and convert them into electrical signals, to pass on information to a co-ordination centre.

What is the function of a co-ordination centre?

Receive and process information from a receptor cell and determine appropriate response.

What is the function of an effector?

To carry out the response and restore the optimum level.

What is the function of the nervous system in humans?

The nervous system enables humans to react to their surroundings and to coordinate their behaviour.

How many parts does the human nervous system consist of? Name each.

The human nervous system consists of two parts:

• the central nervous system (CNS)

• the peripheral nervous system (all the other nerves running to and from the CNS)

What does the Central nervous system and peripheral nervous system consist of?

The central nervous system consists of the brain and spinal cord,

while the peripheral nervous system consists of all other nerves running to and from the central nervous system.

What does the central nervous system consist of?

Brain

Spinal cord

Describe the features of the nervous system.

Receptors detect a stimulus;

and send electrical impulses down neurones to the central nervous system.

The central nervous system is the coordination centre.

The CNS sends electrical impulses down other neurones to effectors.

The effectors bring about a response.

Effectors are often a muscle which contracts or a gland that secretes a hormones.

What is the reflex arc?

The reflex arc is the neural pathway involved in a reflex action.

What happens when you touch a hot object?

Stimulus detected by a receptor.;

stimulus is heat and the receptor is in the skin.

Electrical impulses pass from the receptor along a sensory neurone.

Sensory neurones are connected to receptors.

At the end of a sensory neurone, there is a junction named the synapse, at which a chemical is released.

The chemical diffuses across to a relay neurone in the CNS, where it triggers an electrical impulse.

The electrical impulse now passes across the relay neurone and reaches another synapse at which 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 example, the effector is a muscle.

The muscle contracts;

pulls hand away from the hot object

Give the order of the features of an automatic control system.

Stimulus, receptor, coordinator, effector, response

Is conscious decision making involved in reflexes?

No, reflexes are involuntary actions. There is no decision making by the conscious part of the brain.

What is the result of no conscious decision making being involved in reflexes and why is this important?

Reflexes provide a rapid, automatic response to stimuli,

crucial for protection from danger and survival.

What are some key features of the nervous system?

Extremely fast

The effects tend to be short- lived

What is the function of the brain?

The brain controls complex behaviour.

Describe the brain.

The brain is made up of billions of interconnected neurones (nerve cells);

has different regions responsible for carrying out various functions.

What are the parts of the brain that you have to know about for your exam?

Cerebral cortex

Cerebellum

Medulla

Describe the cerebral cortex.

The cerebral cortex is the outer part of the brain

highly folded

responsible for higher-level cognitive functions.

Examples: intelligence, personality, language, memory, consciousness

Describe the function of the cerebellum.

The part of the brain responsible for coordinating movement, and balance (and muscular activity)

Describe the function of the medulla.

Controls unconscious activities

such as: the heart rate and breathing rate.

What is the function of the hypothalamus?

The hypothalamus regulates body temperature and water balance.

Explain some of the difficulties of investigating brain function and treating brain disease/ damage (Higher tier only).

The brain is protected by the skull; difficult to access.

Structures within the brain are very complex; a challenge to figure out exactly which parts carry out specific functions.

Very delicate; easy to damage.

What are the 3 ways that neuroscientists have been using to map the regions of the brain to specific functions?

Studying patients with brain damage by seeing the location of the damage and its impact on the ability to carry out different functions.

Electrically stimulating different parts of the brain and seeing the effects on the individual's behaviour; allows researchers to narrow down specific parts/ regions to their functions.

MRI scanning to see which regions are most active during various activities. I.e. if the person is looking at numbers, there is greater activity in the brain region responsible for numerical processing.

What makes investigating and treating brain disorders very challenging?

The complexity

The delicacy