6. Detecting and regulating change

Question 1

What is a receptor?

Answer 1

A structure that is able to detect change in the body’s internal and external environment

Question 2

What is a sense organ?

Answer 2

Receptor cells of a particular type that are grouped together

Question 3

What are thermoreceptors and what do they do?

Answer 3

Respond to hot and cold

In the skin, inform brain to changes outside the body received by the hypothalamus and cerebrum

Question 4

What are skin thermoreceptors?

Answer 4

Are nerve endings and either are sensitive to either hot or cold, not both

Question 5

How is temperature inside the body monitored?

Answer 5

Monitored by thermoreceptors in the hypothalamus, detecting the temperature of blood flowing through the brain

Question 6

How is osmotic pressure determined?

Answer 6

By the concentration of substances dissolved in the water of the blood plasma

Question 7

Where are osmoreceptors found?

Answer 7

In the hypothalamus and are sensitive to osmotic pressure

Question 8

What do osmoreceptors do?

Answer 8

They respond to very small changes, stimulate the hypothalamus so the body’s water content is manipulated within narrow limits

Question 9

Where are chemoreceptors found?

Answer 9

Chemoreceptors are present in the nose (odour sensitivity) and in the mouth (sensitivity to taste)

Question 10

What are chemoreceptors sensitive to?

Answer 10

Internal chemoreceptors are sensitive to the composition of bodily fluids, especially those in certain blood vessels that are sensitive to the pH of the blood and to concentrations of O2 and CO2

Question 11

Where are touch receptors found?

Answer 11

Mainly in the skin

There are different types

Question 12

What are the types of touch receptors?

Answer 12

Close to the surface: sensitive to light touches, occurring in greater concentrations in sensitive areas (lips, fingertips, eyelids etc.)
Nerve endings: At the base of each hair follicle, respond to any light touch that bends a hair
Some are deeper in the skin and are sensitive to pressure and vibrations

Question 13

Do touch receptors adapt quickly or slowly?

Answer 13

Both adapt rapidly and after a short amount of time, you are no longer aware of the touch

Question 14

How are pain receptors stimulated?

Answer 14

Pain receptors are stimulated by damage to the tissues (cut, heavy bump, poor blood flow, excessive heat or chemical stimulation)

Question 15

Where are pain receptors found?

Answer 15

Concentrated mostly in the skin and mucous membranes

Occur in most organs, but not the brain

Question 16

Why are pain receptors essential?

Answer 16

Because it tells us when damage to the tissues are occurring to warn us to take evasive action or seek medical helps

Question 17

Why does pain become worse over prolonged stimulation?

Answer 17

Because they adapt a very little amount so the pain continues when the stimulus is present

Question 18

What is a reflex?

Answer 18

A rapid, automatic response to changes in internal and external environments

Question 19

Characteristics of reflexes:

Answer 19

A reflex is involuntary
A stimulus is required to trigger a reflex
Responses are rapid, involving a small number of neurons
The response is stereotyped occurring in the same way it happens each time

Question 20

Why are most reflexes coordinated by the spinal cord?

Answer 20

Because it creates a quicker response time

Question 21

What is a spinal reflex?

Answer 21

A spinal reflex is when an impulse passes to motor neurons in the cord without touching the brain

Question 22

What is a reflex arc?

Answer 22

A reflex arc is the way an impulse follows from receptor to effector

Question 23

Are spinal reflexes voluntary or involuntary?

Answer 23

Always involuntary, despite involving the contraction of skeletal muscles

Question 24

How are we aware of what is happening if the message is only sent to the spinal cord?

Answer 24

Because a message is only sent to the brain once a response has been initiated

Question 25

Key components to a reflex:

Answer 25

A receptor at each end of a sensory neuron or specialised cell, which reacts to a change in the internal or external environment by initiating a nerve impulse in the sensory neuron Sensory neuron carries impulses from the receptor to the CNS At least one synapse occurs A motor neuron carries the impulse to an effector An effector receives the impulse and carries out the appropriate response

Question 26

What are protective reflexes?

Answer 26

Reflexes that protect the body from injury and have been present since birth.

Question 27

Examples of protective reflexes:

Answer 27

Blinking, sneezing, constriction of pupils in response to light Secretion of saliva in response to food

Question 28

Describe the reflex arc of putting your hand down on a nail

Answer 28

Stimulus: hand is on nail Receptor: pain receptors in skin detect the stimulus and produce a nerve impulse Modulator: Sensory neurons conduct the nerve impulse from the receptor to the spinal cord Information is processed in the CNS. 1-2 interneurons pass the message to the appropriate motor neuron Motor neuron carries a nerve impulse to the effector Effector: The bicep muscles contracts, removing the nad from the stimulus Response: Hands moves away from the stimulus

Question 29

What are innate reflexes?

Answer 29

More complex motor patterns that appear during development, suckling, chewing, following movements with the eyes

Question 30

What are acquired reflexes?

Answer 30

Are learned and include muscular adjustments to maintain balance while riding a bike, slamming on breaks to avoid a crash or catching a ball Learned through constant repetition

Question 31

What is homeostasis?

Answer 31

The process of keeping the internal environment of the body fairly constant

Question 32

Examples of homeostasis occurring in the body:

Answer 32

Temperature control, pH, constant oxygen supply and glucose removal, waste removal, concentrations of dissolved substances, blood pressure, concentrations of metabolic wastes

Question 33

What are the two goals of homeostasis?

Answer 33

Supply the cells needs | Maintain a constant cellular environment

Question 34

What is a dynamic equilibrium?

Answer 34

Where the input and output of materials and energy are balanced

Question 35

What are the main sensory and controlling body systems that operate through feedback loops?

Answer 35

Nervous system | Endocrine system

Question 36

What is a tolerance limit?

Answer 36

The upper and low limits of a variety of factors, controlled through homeostatic procedure

Question 37

What if a tolerance limit has been exceeded?

Answer 37

A rise or fall below the normal range has occurred and dysfunctions will occur

Question 38

What is a feedback system?

Answer 38

A circular situation in which the body responds to a stimuli, with the response altering the original stimulus

Question 39

What is a negative feedback system?

Answer 39

A system where the response causes the stimulus to change in the opposite direction to the original change (Steady state control system) The response has an effect of reducing or eliminating the stimulus that caused it

Question 40

Feedback system for glucose in the blood:

Answer 40

During exercise the muscles use glucose to release the energy required for muscular contraction Muscles absorb glucose from the blood and blood glucose levels fall The liver responds by releasing more glucose to go up, which is the opposite of the fall which initiated the response

Question 41

What is a stimulus in a feedback loop?

Answer 41

The change in the environment that causes the system to operate

Question 42

What is the receptor in a feedback loop?

Answer 42

The receptor is the thing that detects the change

Question 43

What is the modulator in a feedback loop?

Answer 43

Modulators process the information received from the receptor sending information to the effector

Question 44

What is the effector in a feedback loop?

Answer 44

An effector creates a response to counteract the effects of the stimulus

Question 45

What is a positive feedback loop?

Answer 45

It has no role in homeostasis and the response reinforces/intensifies the stimulus, which results in an even greater response

Question 46

How is childbirth an example of a positive feedback loop?

Answer 46

During childbirth: Labour is initiated by the secretion of oxytocin, which causes contractions and pushing the cervix, which sends impulses to the brain and APG to secrete more oxytocin Once the baby is delivered, the cervix is no longer stretched and the positive feedback cycle stops