Homeostasis and the human nervous system Flashcards
Describe homeostasis?
The maintenance of a constant internal environment in a cell or organism; such as body temperature, water balance, blood glucose levels etc
Identify the key conditions which are essential for the human body to maintain in homeostasis and explain their importance
Blood glucose concentration- not enough and you would lack energy however too much can put a person into a coma.
Body temperature- if you are too hot or too cold then the enzymes in the body cannot control cellular reactions, both can be fatal
Water balance- to little or too much water can also be fatal for humans
Describe the main difference between nervous and hormonal control of homeostasis
Nervous control is quicker than hormonal control because the electrical nerve impulses travel along the neurones much more quickly then hormones can travel through the blood to reach their target organs.
Describe the difference between voluntary and involuntary actions.
Involuntary actions are automatic and occur as a result of receptors sending information to the coordination centers which then send messages to the effectors. You do not know that they are happening. An example would be for the body to increase the production of sweat to lower body temperature.
Voluntary actions require conscious thought; such as deciding to walk, the effectors are still sent messages from the coordination centres.
Describe the central nervous system?
The central nervous system is the brain and the spinal cord.
Explain the term receptor and give examples of where they are located.
A receptor is a cell or group of cells which are at the start of a neural pathway, the detect change and generate an electrical impulse which is sent to the central nervous system
Examples include receptors in the skin, eyes, ears, tongue and nose.
Explain the role of an effector in the nervous system
An effector is a muscle or a gland which brings about a response as a result of an electrical impulse. It either causes movement of a part of the body or results in a gland secreting a hormone.
Explain the role of a neurone in the nervous system
Neurones link both receptors and effectors to the coordination centres.
Describe how messages are transmitted along nerve cells
Electrical impulses travel along nerve cells at speeds of about 120m per second.
They are generated by receptor cells and respond to stimuli often in the sense organs.
In longer nerve cells the impulses are insulated by a myelin sheath.
The central nervous system receives the impulses and generates a response.
The response is sent to effectors which carry out an action or secrete a hormone.
Identify the different senses, their stimuli and the organs which are used.
Sense - organ - stimuli Sight - eyes - light Hearing - ears - sound Taste - tongue - chemicals in food Smell - nose - chemicals in food Touch - skin - touch, pressure, temperature and itching
Describe the different neurones and their role in relaying impulses
- Sensory neurones carry an impulse from a receptor to the central nervous system (CNS)
- Relay neurones carry an impulse within the CNS (brain and spinal cord)
- Motor neurones carry an impulse from The CNS to an effector (muscle or gland)
Identify the pathway of impulses from stimulus to response
stimulus -> receptor -> sensory neurones -> relay neurones -> motor
neurones -> effector -> response
Explain how a synapse allows nerve impulses to be transmitted between nerve cells.
Nerves are not one continuous line but are made of a series of neurones with a small gap between each one.
This gap is called the synapse.
Neurones have branched ends called dendrites which convert an electrical impulse into a chemical signal.
The signal called a neurotransmitter diffuses across the synapse and is picked up by the dendrites of the next nerve cell.
They bind to receptors and trigger another electrical impulse which travels along the neurone to the next synapse and so on.
Explain the term refex arc
The reflex arc is the pathway of neurones in a reflex action
A reflex action is one where the brain is not required to think but happens automatically. Eg moving your hand away from a hot surface.
The initial response is sent from the receptor along the sensory neurones to the spinal cord. However instead of relay neurones taking the signal to the brain the spinal cord sends impulses along the motor neurones directly to the effectors.
This enables us to react more quickly to dangerous situations.
Identify the two types of effector
Muscles and glands
