Intro to Homeostatis and the nervous system Flashcards
What is homeostasis and what does it do?
the regulation of the internal conditions of a cell’s or organism in response to internal or external changes.
maintains optimal conditions for enzyme action and all cell functions.
What conditions do homeostasis control?
- blood glucose concentration
- body temperature
- water and ion levels
What type of communication do automatic control systems use?
nervous and hormonal
What do all control systems include?
- cells called receptors, which detect stimuli (changes in the environment)
- coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors
- effectors (muscles or glands) which bring about responses which restore optimum levels.
What does the nervous system allow us to do?
enables humans to react to their surroundings and to coordinate their behaviour
Describe the pathway through the nervous system, starting at the receptor.
- information from the receptors passes to the central nervous system
- the CNS coordinates the response of effectors, ie muscles contracting or glands secreting hormones
What’s the central nervous system?
brain and spinal cord
describes how the body makes a response.
starting at the stimulus
stimulus –> Receptor –> Coordinator –> Effector –> Response
What is a reflex action?
an automatic and rapid response to a stimulus so they can protect the body
they do not involve the conscious part of the brain
How do we detect pain?
1) pain stimulus is detected by receptors
2) impulses from the receptor pass along a sensory neurone to the CNS
3) From the CNS An impulse then passes through a relay neurone
4) A motor neurone carriers impulses to the effector
5) the effector (usually a muscle) responds
What is the role of a sensory neurone?
A sensory neurone carries signals from the receptors to the spinal cord or brain.
What is the role of a relay neurone?
A relay neurone carries messages from one part of the CNS to another
What is the role of a motor neurone?
Motor neurones carry signals from the CNS to effectors.
How are electrical impulses carried between neurones?
Between neurons are junctions called synapses. electrical impulses trigger the release of chemical signals - neurotransmitters. The neurotransmitter diffuses across the synapse where it is then converted back into an electrical impulse.
neurones are not directly connected to each other
What does the brain control and what is it made up of it?
The brain controls complex behaviour.
It is made of billions of interconnected neurones and has different regions that carry out different functions.
What are the main regions of the brain?
cerebral cortex, medulla and the cerebellum
What is the role of the cerebral cortex?
The cerebral cortex is concerned with:
Consciousness
Intelligence
Memory
Language
What is the role of the cerebellum?
The cerebellum coordinates movement and balance.
What is the role of the medulla?
The medulla controls unconscious (automatic) activities such as controlling heartbeat, breathing and the movements of the gut.
Explain why it is difficult to investigate and treat brain disorders.
The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult.
Drugs do not always reach the brain through the membranes that surround it.
investigation of brain function could cause physical damage to the brain or increased problems with brain function
How do scientists use patients with brain damage to study the brain?
the effect the brain damage has on the patient can tell you a lot about what the damaged part of the brain does
How do scientists use electrically stimulating to study the brain?
- by pushing a tiny electrode into the tissue and giving it a small zap of electricity
- by observing what stimulating different parts of the brain does, it’s possible to get an idea of what these parts do
How do scientists use MRI scans to study the brain?
by producing very detailed pictures of the brain’s structure, scientists can use it to find out what areas of the brain are active when people are doing activities
What does the retina do?
what is it?
what does it contain?
contains receptor cells that are sensitive to the brightness and colour of light
allows us to detect light intensity and light colour
What does the optic nerve do?
carries impulses from the retina to the brain
What does the sclera do?
tough supporting wall of the eye
protects the eye from serious damage
What does the cornea do?
transparent outer layer founded at the front of the eye
it refracts light into the eye
What does the iris do?
contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye
What does the ciliary muscles and suspensory ligaments do?
changes the shape of the lens to focus light on the retina
What happens to the eye when the light receptors in the eye detect bright light
- reflex is triggered that makes the pupil smaller
- circular muscles in the iris contract and the radial muscles relax
- this reduces how much light can enter
What happens to the eye when the light receptors in the eye detect dim light
- radial muscles contract
- circular muscles relax which makes the pupil wider
What is accommodation?
the process of changing the shape of the lens to focus on a near or far object
What does the eye do to focus on a near object?
- cilliary muscles to contract
- suspensory ligaments loosen
- lens is then thicker and more curved. refracts light stronger
What does the eye do to focus on a far object?
- ciliary muscles loosen
- suspensory ligaments are pulled tight
- lens is pulled thin and only slightly refracts light rays
What are the two common defects of the eye?
myopia and hyperopia
What is myopia?
how is the eye
short-sightedness
- lens is too curved, so too thick, distant objects appear blurry
- eyeball is too long = light rays focused on a point in front of the retina
What is hyperopia?
how is the eye
long-sightedness
- lens too flat, not thick enough, cannot refract light enough
- eyeball too short = light rays focus behind the eye
How is myopia fixed?
uses glasses with a concave lens
- lens curve inwards to correct it so that the light rays focus on the retina, by partially unfocusing the light before it enters the eye
How is hyperopia fixed?
glasses with a convex lens
- lens refract light rays so they focus on the retina
What are the different types of treatments for the eye?
- spectacle lenses
- hard and soft contact lenses
- laser surgery to shape the cornea and add replacement lens
What happens to the muscle when it detects pain?
it contracts
it becomes smaller
- this moves the muscle away from the object hurting it = protection
