homeostasis

Question 1

what is homeostasis?

Answer 1

• homeostasis is the regulation of the internal conditions of a cell or organism to maintain a stable internal environment in response to internal and external changes
• important as enzymes + cells require stable conditions to work
• Homeostasis maintains optimal conditions for enzyme action and all cell functions

Question 2

what does homeostasis consist of?

Answer 2

• automatic control systems which make sure the internal conditions of the body stay as constant as possible
• automatic control systems in the human body can involve the nervous system or hormones
• for example, there are control systems that maintain the body’s blood glucose conc, body temperature+ water levels

Question 3

what three components are automatic control systems made up of?

Answer 3

• cells called receptors - detect stimuli (changes in the environment) - internal or external environment
• the receptor then pass information to a coordination centre (brain, spinal cord or the pancreas)
• coordination centre receives + processes the info from the receptor cells
• coordination centre now sends instructions to the effector (which is a muscle or a gland)
• effector - job is to carry out the response that restores the optimum level

Question 4

what does the nervous system enable humans to do?

Answer 4

react to their surroundings and coordinate their behaviour

Question 5

what is the nervous system made up of?

Answer 5

• central nervous system - in vertebrates (animals with backbones) this consists of the brain + spinal cord only
• in mammals, the CNS is connected to the body by sensory neurones + motor neurones
• sensory neurones - the neurones that carry info as electrical impulses from the receptors to the CNS
• motor neurones - neurones that carry electrical impulses from the CNS to effectors
• effectors - all your muscles and glands - which respond to nervous impulses

Question 6

how can receptors and effectors form part of complex organs?

Answer 6

• there are different types of receptors - taste receptors on the tongue + sound receptors in the ears
• receptors can form part of larger, complex organs - retina of the eye is covered in light receptor cells
• effectors respond to nervous impulses and bring about a change
• muscles + glands known as effectors - they respond in diff ways
• muscles contract in response to a nervous impulse - but glands secrete hormones

Question 7

what is a synapse?

Answer 7

• the connection between two neurones
• the nerve signal is transferred by chemicals which diffuse across the gap
• these chemicals then set off a new electrical signal in the next neurone

Question 8

what are reflexes?

Answer 8

• rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - can reduce the chances of being injured
• the passage of information in a reflex (from receptor to effector) is called a reflex arc

Question 9

how information flows from receptors to effectors in the nervous system - diagram

Answer 9

stimulus→receptor→coordinator→effector→response

Question 10

how does the reflex arc go through the central nervous system?

Answer 10

• ex. touch something hot
• Receptor in the skin detects a stimulus (the change in temperature)
• sensory neuron sends electrical impulses to a relay neuron - which located in the spinal cord of the CNS - relay neurons connect sensory neurons to motor neurons
• motor neuron sends electrical impulses to an effector
• effector produces a response (muscle contracts to move hand away)
• because don’t have to think about it - which takes time - quicker than normal responses

Question 11

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Answer 11

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Question 12

what is a nerve

Answer 12

a bundle of neurones (nerve cells)