coordination Flashcards
stimulus
a stimulus is a change in an animal’s surroundings
response
a response is a reaction to the stimulus
receptors
receptors are cells/tissues or organs that detect changes in stimuli
the role of receptors
the role of any receptor is to detect the stimulus by changing its energy into the electrical energy of the nerve impulses, this impulse travels down nerve cells (neurons) to the central nervous system and to an effector, the effector creates the response
receptors and type of energy received
- eye (retina)= light
- ear (organ of hearing)= sound
- ear (organ of balance)= mechanical (kinetic)
- tongue (taste buds)= chemical
- nose (organ of smell)= chemical
- skin (touch/pressure/pain receptors)= mechanical (kinetic)
- skin (temperature receptors)= heat
- muscle (stretch receptors)= mechanical (kinetic)
biological name for a nerve cell
neurone
how impulses work
the impulses that travel along a neurone are caused by movements of charged particles (ions) in an out of the neurone.
the nervous system is made of
the central nervous system: brain, spinal chord
nerves made of cells called neurones: sensory neurones, motor neurones, relay neurones
adaptations of a motor neurone
- cell body: contains the nucleus
- long axon: carries impulses long distances
- many dendrite connections: collect information from other neurones
- many nerve endings: sends information to neurones
- myelin sheath: protects and insulates the axon, speeds up the conduction of impulses
multiple sclerosis
immune system attacks the myelin sheath that protects nerve fibres, causes communication problems between the brain and the rest of the body
functions of the human eye
detects light, can form a proper image, can distinguish colors
structure of the retina
the retina contains light sensitive cells called photoreceptors, rods are sensitive to light and dark, cones are sensitive to red, green, and blue
sclera
tough outer coat of the eye, the visible, white part of the eye
forming an image
in order to form an image on the retina, light needs to be bent or refracted. in the eye light is first refracted at the air/cornea boundary, then again at the lens. as a result of refraction at the cornea and lens, the image on the retina is inverted. the brain interprets the image the right way up.
the role of the iris
the role of the iris is to control the amount of light entering the eye, by changing the size of the pupil
the iris muscles
the iris contains two types of muscles: circular muscles form a ring shape in the iris, and radial muscles lie like the spokes of a wheel.
In bright light the pupil is constricted (made smaller) because the circular muscles contract and the radial muscles relax
in dim light the pupil is dilated (made bigger) because the circular muscles relax and the radial muscles contract
the iris reflex
whenever our eyes look from a dim light to a bright one, the iris rapidly and automatically adjusts the pupil size (reflex action). the purpose of the iris reflex is to allow the right intensity (brightness) of light to fall on the retina. Light that is too bright could damage the rods and cones, and light that is too dim would not form an image.
iris reflex route from stimulus to response
stimulus (Light intensity)
retina (receptor)
sensory neurones in optic nerve
unconscious part of brain
motor neurones in nerve to iris
iris muscles (effector)
response (change in size of pupil
the blind spot
there is one area of the retina where an image cannot be formed, this is where the optic nerve leaves the eye. at this position there are no rods or cones, so it is called the blind spot. the retina of each eye has a blind spot but because the brain puts the images from each eye together, the blind spots of both eyes are cancelled. additionally the optic nerve leaves the eye towards the edge of the retina where vision is not very sharp anyways.
when focusing on a distant object
the ciliary muscles relax, the suspensory ligaments are pulled tight, the lens is less convex (flatter)
when focusing on a nearby object
the ciliary muscles contract, the suspensory ligaments slack, the lens is more convex (rounded)
accommodation
the changes that take place in the eye which allow us to see objects at different distances
a reflex arc is
the nerve pathway of a reflex
reflex arc detailed example
the stimulus is detected by temperature or pain receptors in the skin. these generate impulses in sensory neurones which enter the central nervous system through a part of the spinal cord called the dorsal root. in the spinal cord the sensory neurones connect by synapses with short relay neurones, which in turn connect with motor neurones. the motor neurones emerge from the spinal cord through the ventral root, and send impulses back to the muscles of the arm. these muscles then contract, pulling the arm (and thus finger) away from the harmful stimulus.
