6. Detecting and regulating change Flashcards
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What is a receptor?
A structure that is able to detect change in the body’s internal and external environment
What is a sense organ?
Receptor cells of a particular type that are grouped together
What are thermoreceptors and what do they do?
Respond to hot and cold
In the skin, inform brain to changes outside the body received by the hypothalamus and cerebrum
What are skin thermoreceptors?
Are nerve endings and either are sensitive to either hot or cold, not both
How is temperature inside the body monitored?
Monitored by thermoreceptors in the hypothalamus, detecting the temperature of blood flowing through the brain
How is osmotic pressure determined?
By the concentration of substances dissolved in the water of the blood plasma
Where are osmoreceptors found?
In the hypothalamus and are sensitive to osmotic pressure
What do osmoreceptors do?
They respond to very small changes, stimulate the hypothalamus so the body’s water content is manipulated within narrow limits
Where are chemoreceptors found?
Chemoreceptors are present in the nose (odour sensitivity) and in the mouth (sensitivity to taste)
What are chemoreceptors sensitive to?
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
Where are touch receptors found?
Mainly in the skin
There are different types
What are the types of touch receptors?
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
Do touch receptors adapt quickly or slowly?
Both adapt rapidly and after a short amount of time, you are no longer aware of the touch
How are pain receptors stimulated?
Pain receptors are stimulated by damage to the tissues (cut, heavy bump, poor blood flow, excessive heat or chemical stimulation)
Where are pain receptors found?
Concentrated mostly in the skin and mucous membranes
Occur in most organs, but not the brain
Why are pain receptors essential?
Because it tells us when damage to the tissues are occurring to warn us to take evasive action or seek medical helps
Why does pain become worse over prolonged stimulation?
Because they adapt a very little amount so the pain continues when the stimulus is present
What is a reflex?
A rapid, automatic response to changes in internal and external environments
Characteristics of reflexes:
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
Why are most reflexes coordinated by the spinal cord?
Because it creates a quicker response time
What is a spinal reflex?
A spinal reflex is when an impulse passes to motor neurons in the cord without touching the brain
What is a reflex arc?
A reflex arc is the way an impulse follows from receptor to effector
Are spinal reflexes voluntary or involuntary?
Always involuntary, despite involving the contraction of skeletal muscles
How are we aware of what is happening if the message is only sent to the spinal cord?
Because a message is only sent to the brain once a response has been initiated
Key components to a reflex:
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
What are protective reflexes?
Reflexes that protect the body from injury and have been present since birth.
Examples of protective reflexes:
Blinking, sneezing, constriction of pupils in response to light
Secretion of saliva in response to food
Describe the reflex arc of putting your hand down on a nail
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
What are innate reflexes?
More complex motor patterns that appear during development, suckling, chewing, following movements with the eyes
What are acquired reflexes?
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
What is homeostasis?
The process of keeping the internal environment of the body fairly constant
Examples of homeostasis occurring in the body:
Temperature control, pH, constant oxygen supply and glucose removal, waste removal, concentrations of dissolved substances, blood pressure, concentrations of metabolic wastes
What are the two goals of homeostasis?
Supply the cells needs
Maintain a constant cellular environment
What is a dynamic equilibrium?
Where the input and output of materials and energy are balanced
What are the main sensory and controlling body systems that operate through feedback loops?
Nervous system
Endocrine system
What is a tolerance limit?
The upper and low limits of a variety of factors, controlled through homeostatic procedure
What if a tolerance limit has been exceeded?
A rise or fall below the normal range has occurred and dysfunctions will occur
What is a feedback system?
A circular situation in which the body responds to a stimuli, with the response altering the original stimulus
What is a negative feedback system?
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
Feedback system for glucose in the blood:
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
What is a stimulus in a feedback loop?
The change in the environment that causes the system to operate
What is the receptor in a feedback loop?
The receptor is the thing that detects the change
What is the modulator in a feedback loop?
Modulators process the information received from the receptor sending information to the effector
What is the effector in a feedback loop?
An effector creates a response to counteract the effects of the stimulus
What is a positive feedback loop?
It has no role in homeostasis and the response reinforces/intensifies the stimulus, which results in an even greater response
How is childbirth an example of a positive feedback loop?
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
