Topic 5- Human nervous system Flashcards
What is the function of the nervous system?
The nervous system allows the body to react to its surroundings and coordinate an appropriate response
How des a stimulus lead to a response being carried out by the body?
-Stimulus is converted into an electrical impulse by the receptors
-The electrical impulse passes along sensory neuron’s to the the central nervous system (CNS)
-The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones 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 reflex action?
A reflex action is an automatic and rapid response which does not involve any conscious input from the brain
Why are reflex actions important?
Reflex actions aid survival by preventing harm to the body
Describe how a reflex action occurs via a reflex arc
-The stimulus is detected by a receptor
-An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
- At a 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 a 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 neurone found in the spinal cord/unconscious parts of the brain. 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 activities (eg breathing, heart rate etc)
Why is the investigation and treatment of the brain difficult
-Its a complex and delicate organ
-The brain is easily damaged and destroyed
-Certain membranes prevent drugs from reaching the brain
- The exact function of each part of the brain is not known
What methods are used by scientists to determine brain function?
-Studying patients with brain damage
-Electrical stimulation of the brain
-MRI scans
What stimuli are the receptors of the eye sensitive to
Light intensity and colour
What are the two main functions of structures found within the eye?
Focusing on near or distant objects- accommodation
Adaptation to dim light
Describe the structure and function of the retina
The retina is a light-sensitive layer found at the back of the eye
Light stimulates the retinal cells, resulting in impulses being sent to the brain
Describe the structure an function of the the optic nerve
The optic nerve connects the eye and the brain
It carries impulses to the brain so that image can be visualised
Describe the structure and function of the sclera
The sclera is the though outer layer of the eye which protects its internal structures
Describe the structure and function of the cornea
The cornea is the 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
The iris is a muscle which controls the size of the pupil by contracting or relaxing. This allows the eye to adjust to bright and dim lighting
Describe the structure and function of the ciliary muscles and suspensory ligaments
The ciliary muscles and suspensory ligaments hold the lens in place and control its shape
Describe how the iris alters the size of the pupil in both bright and dim light
Bright light: Circular muscles contracts and radial muscles relax- makes pupil smaller to avoid retinal damage
Dim light: circular muscles relax and radial muscles contract- makes pupil larger so more light can enter the eye
What is accommodation?
Altering the lens’ shape in order to focus on near 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
Myopia (short-sightedness) usually occurs Shen the lens of the eye is too curved. As a result, light focused in front of the retina so images appear blurry
How can myopia treated
Myopia can be treated using glasses with a concave lens, which spreads out light rays so they can be focused on the retina
What is hyperopia
Hyperopia (long-sightedness) usually occurs when the lens of they is too flat. As a result, light is focused behind the retina so images appear out focus
How can hyperopia be treated
Hyperopia can be treated using glasses with a convex lens, 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, last for a shorter time, more comfortable
What is laser eye surgery?
Laser eye surgery is the use 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?
A replacement lens can either implanted into the eye (along with natural lens) or it may replace the natural lens altogether. Risks of lens replacement include renal damage, cataracts, and infections
What are the risks of lens replacement
Risks of lens replacement include renal damage, cataracts, and infections
Where is body temperature controlled in the body
Body temperature is controlled 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 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 away heat energy from 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
Shivering- respiration allows muscles to contract. It is an exothermic process, so heat energy is released
Sweating stops
