P2- Homeostasis and response Flashcards
What is homeostasis?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Two examples of automatic control systems
Chemical (hormonal) and Nervous sytem
Examples of internal body conditions
Body temperature, blood sugar levels, blood pH, water concentration
What are the three main components of the automatic control system?
Receptor, effector and coordination centre
What is a receptor?
A cell that detects a stimulus
What is the coordination centre?
Receives and processes the information and organises a response
What is an effector?
The muscle (nervous) or gland (chemical) that produces a response to restore the optimum level by counteracting the change
What is a stimulus?
A change in environment
What are hormones?
Chemical messengers which are used in the body by the endocrine system, co-ordinate our organs and are produced by the glands.
What is the endocrine system?
Composed of glands which secrete hormones directly into the bloodstream
What is the blood’s role in the endocrine system?
Carry the hormones to a target organ where it produces an effect
Examples of what hormones control
Growth, sexual development, sugar levels, mood, metabolism
Which gland in the brain is the ‘Master Gland’?
Pituitary gland
What is the nervous system?
The nervous system allows us to detect and react to changes in the environment. Humans can react to their surroundings and coordinate their behaviour
What are the 4 parts of the Nervous system?
Central nervous system (CNS), Sensory neurone, motor neurone and effector
What is the role of the Central Nervous (CNS)?
A coordination centre which receives information from the receptor and coordinates a response (which is carried out by the effector)
What is the Central Nervous system (CNS) mad up of?
Brain and spinal cord only
What is the role of the sensory neurone?
Carry information as electrical impulses from the receptors to the CNS
What is the role of the motor neurone?
Carry information electrical impulses from the CNS to the effectors
What is a synapse?
The connection between two neurones where the impulses need to pass through
How does a synapse work?
1) When an electrical impulse reaches the end of an axon entering the synapse, the axon releases a transmitter substance.
2) The transmitter substance (chemicals) diffuses across the gap.
3) These chemicals then set off a new electrical signal in the next neurone
What are reflexes?
Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain
What is a benefit of having reflexes?
They can reduce the chances of injury
Give an example of one of your body’s reflexes that reduce injury
Your pupils automatically get smaller when bright light is shone on them to prevent the pupils getting damaged
What is the Reflex Arc?
The passage of information in a reflex
Stages of the Reflex Arc (full)
1) The stimulus (e.g a pin prick)
2) Pain receptors in the skin are stimulated
3) Nerve impulse travels along sensory neurone
4) Nerve impulse enters spinal cord
5) Nerve impulse passes across synapse into a relay neurone
6) Nerve impulse passes into motor neurone and travels along this, out of the spinal cord
7) When nerve impulse reaches finger, muscle (effector) contracts, pulling the finger away (response)
Stages of the reflex arc (words)
Stimulus- Receptor- Sensory neurone- Synapse- Relay neurone- Motor neurone- Effector- Response
What is reaction time?
The time it takes to respond to a stimulus
Examples that can affect reaction time?
Age, gender, drugs (e.g caffeine)
What is the role of the brain?
It controls complex behaviour, is part of the Control nervous system (CNS), made up of billions of interconnected neurones
Role of the cerebral cortex/cerebrum in the brain?
(Outer wrinkly bit) Responsible for conscious activity like memory, language/speech, thoughts, vision, intelligence
Where is the cerebral cortex/cerebrum located in the brain?
The top of your brain
Role of the cerebellum in the brain?
Resposible for muscle coordination and movement
Where is the cerebellum located in the brain?
Lower back of the brain
Role of the medulla (oblongata) in the brain?
Responsible for unconscious activity like your heart rate and breathing rate
Where is the medulla located in the brain?
Base/bottom part of the brain (connected to spinal cord)
Role of the hypothalamus?
To control the centre monitoring brain and helps maintain homeostasis
Where is the hypothalamus located?
In the brain
Role of the pituitary (master) gland?
Responsible for regulating many body functions and the activity of other glands
Where is the pituitary gland located?
In the brain
3 ways of treatment to study the brain
1) Studying patients with brain damage
2) Electrically stimulating different parts of the brain
3) Using MRI (magnetic resonance imaging) scanning techniques
What is the eye?
The eye is a sense organ containing receptors that are sensitive to light intensity and colour.
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects.
What is the retina in the eye?
A layer of cells at the back of the eye
Role of the retina in the eye
Contains receptors that are sensitive to light intensity and colour
Role of the sclera in the eye
The tough white outer layer of the eye which helps protect the eye from injury
Role of the cornea in the eye
The transparent outer layer at the front of the eye which refracts light (light bends as it enters the eye)
Role of the iris in the eye
Contain muscles which control the diameter/size of the pupil and therefore how much light enters the pupil
Role of the lens in the eye
Focuses the light onto the retina
Role of the ciliary muscles in the eye
Contracts or relaxes to move the suspensory ligaments
Role of the suspensory ligaments in the eye
Pulls the lens thin or allows the lens to widen
Role of the optic nerve in the eye
Carries impulses between the eye and the brain
What are the two types of muscles in the eye?
Circular muscles and radial muscles
Where are the circular and radial muscles found?
Iris
What happens to the eye in dim/low light?
1) Circular muscles in the iris relax
2) Radial muscles in the iris contract
3) Pupil dilates
4) More light enters the eye
What happens to the eye in bright light?
1) Circular muscles in the iris contract
2) Radial muscles in the iris relax
3) Pupil constricts
4) Less light enters the eye
What happens if a person’s lens cannot refract the light by the right amount?
They are either short or long sighted
Long sighted people are unable to focus on…
Near objects
What is the scientific name for long-sightedness?
Hyperopia
What happens in the lens of someone who is long-sighted (hyperopia)?
Their eyeball is too short/ lens cannot be thickened enough. The light rays aren’t refracted enough and the image of near focus objects are brought into focus behind the retina
How is being long-sighted (hyperopia) fixed?
Using convex lenses
How does the eye focus on near objects?
1) Ciliary muscles contract and have a smaller diameter
2) Suspensory ligaments loosen
3) Lens is then thicker, becomes more convergent which refracts light rays strongly onto the retina
Short sighted people are unable to focus on…
Distant objects
What is the scientific name for short-sightedness?
Myopia
What happens in the lens of someone who is short-sighted (myopia)?
Their eyeball is too wide/lens overthickens. The light rays refract too much and focus infront of the retina
How is being short-sighted (myopia) fixed?
Using concave lenses