B10 The Nervous System Flashcards
What is homeostasis?
Maintenance of constant internal environment in order to maintain optimal conditions for enzyme and cellular functions
The conditions maintained by homeostasis in the body
Blood glucose concentration
Water levels
Body temperature
What 2 types of responses are used in body control system?
Nervous and Chemical responses
What 3 components do all control systems have
Receptors
Coordination centre
Effector
What is the function of a receptor?
Detect changes in the environments (stimuli)
What is the function of a coordination centre?
obtain and process information from the receptors
What is the function of an effector?
Bring about responses to stimuli
What is the function of the Nervous System?
Allow body to react to surroundings and coordinate an appropriate response
How does a stimulus lead to a response being carried out by the body?
Stimulus is converted into a electrical impulse by the receptors
Electrical impulse passes along sensory neurone to the central nervous system
The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurone to the effector which carries out the response
What sequence of events describes how the nervous system works?
Stimulus —–> Receptor —–> Coordinator —–> Effector —–> Response
What is a reflex action?
Automatic and rapid response which does not involve any conscious input from the brain
Why are reflex actions important?
Aid survival by preventing harm from the body
Describe how a reflex action occurs via a reflex arc
Stimulus is detected by a receptor
An electrical impulse passes along a sensory neurone to the spinal cord
At the synapse between a sensory neurone and a relay neurone a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
The same process occurs at the synapse between a relay neurone and a motor neurone
At the effector an appropriate response is carried out
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway the coordination centre is a relay nueron found in the spinal cord/unconscious parts of the brail. In a conscious pathway, the coordination centre is in the conscious part of the brain
What is the function of the cerebral cortex?
Controls consciousness, intelligence, memory and language
What is the function of the cerebellum?
Controls muscular coordination
What is the function of the medulla?
Controls unconscious activiets eg. breathing , heart rate
Why is the investigation and treatment of the brain difficult?
The brain is a complex and delicate organ
The brain is easily damages and destroyed
Certain membrane prevent drugs from reaching the brain
The exact function of each part of the brain is not known
What methods are used by scientist to determine brain function?
Studying patients with brain damage
Electrical stimulation of the brain
MRI scans
What stimuli are the receptors of the eyes sensitive to?
Light intensity and colour
What are the two main functions of structures found within the eye?
Focusing on near or distant objects
Adaptation to dim light
Describe the structure and function of the retina
The retina is a light sensitive layer found at the back if the eyes
Light stimulates the retinal cells resulting in impulses sent to the brain
Describe the structure and function of the optic nerve
Connects the eye and the brain
It carries impulses to the brain so that and image can be visualised
Describe the structure and function of the sclera
The thought outer ayer of the eye which protects its internal structures
Describe the structure and function of the cornea
Curved transparent layer at the front of the eye
It lets light into the eye and allows light to be focused onto the retina
Describe the structure and function of the iris
A muscle which controls the size of the pupils but contracting or relaxing. this allows the eye to adjust to bright and dim lighting
Describe the structure and function of the ciliary muscles and suspensors ligaments
The ciliary muscles and suspensory ligaments hold the lens on place and control its shape
Describe how the iris alters size of the pupils in both bright and dim light
Bright light: circular muscles contact and radial muscles relax- makes pupil smaller to avoid retinal damage
Dim light: circular muscles relax and radial muscles contract- malke pupil larger so more light can enter the eye
What is accommodation?
The alteration of the lens shape in order to focus on ear or distant objects
How does the eye focus on a nearby object?
Ciliary muscles contract
Suspensory ligaments loosen
Lens becomes thicker and more curved-light rays are refracted strongly
How does the eye focus on a far away object?
Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner- light rays are refracted weakly
What is myopia?
Short-sightedness that usually occurs when the lens of the eye is too curved. As a result light is focused in form go the retina so images appear blurry
How can myopia be treated?
By using glasses with a concave lensw, which spreads out light rays so they can ve focused on the retina
What is hyperopia?
Long sightedness that usually occurs when the lens of the eye is too flat. As a result light is focused behind the retina so images appear out of focus
How can hyperopia be treated?
Using glasses with a convex lense which brings the light rays together so they can be focused on the retina.
What are the two types of contact lenses?
Contact lenses are lenses that are placed on the eye.
There are two types:
Hard- rigid material, last a long time, must be kept sterile
Soft- flexible material, lasts for a shorter time, more comfortable
What is laser eye surgery?
The uses of lasers to fix visual defects in adults. to treat myopia, lasers reduce the thickness of the cornea so light is refracted less strongly. To treat hyperopia, lasers alter the curvature of the cornea so that light is refracted correctly
How can replacement lenses be used to treat visual defects?
Can either implant into the eye ( along with the natural lens) or it may replace the natural lens altogether .
What are the risk of lens replacement?
Risks of lens replacement include retinal damage, cataracts and infections
Where is body temperature controlled in the body?
By the thermoregulatory centre in the hypothalamus of the brain
How is temperature monitored by the body?
Thermoregulatory centre has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature- sends impulses to thermoregulatory centre
What physiological changes occur when the body temperature is too high?
Vasodilation- blood vessels near the surface of the skin dilate- more heat is radiated away
Sweating- evaporation of water takes heat energy form the surface of the skin
What physiological changes occur when the body temperature is too low?
Vasoconstriction - blood vessels near the surface of the skin constrict - less heat radiated away
Shivering - respiration allow muscles to contract. It is an exothermic process, so heat energy is released.
Sweating stops
