b3.1-The Nervous System Flashcards
b3.1.1-What are the stages in a nervous response?
A stimulus which is a change in environment. The sensory receptors detect the stimulus and a response occurs from the effectors in muscles or glands. Muscles respond by contracting causing movement, glands respond by releasing hormones.
b3.1.1-What do receptor cells detect?
Different receptors detect different stimuli and they change the stimulus into electric impulses that travel along neurones(nerve cells) to the Central Nervous System(CNS). The CNS is made up of your brain and spinal cord.
b3.1.1-How does the impulse travel to and from the CNS?
Sensory Neurones-carry electric impulses from receptor cells to the CNS
Relay Neurones-carry electric impulses from sensory neurones to motor neurones
Motor Neurones-carry electric impulses from the CNS to effectors
b3.1.1-What are all the steps in a nervous reaction?
Stimulus -> Receptor Cells -> Sensory Neurone -> Spinal Cord -> Brain -> Spinal Cord -> Motor Neurone -> Effector -> Response
b3.1.2-What is a reflex action?
A reflex action is an involuntary reaction that takes 0.2 seconds and takes place without thinking. They are different from voluntary reactions as you consciously choose to do them. They usually take place when you are in danger.
b3.1.2-How does a reflex action occur?
It occurs in a reflex arc:
Stimulus -> Receptor Cells -> Sensory Neurone -> Spinal Cord -> Motor Neurone -> Effector -> Response
b3.1.3-Where are the main structures of the eye found?
Cornea—coating on front of eye
Pupil—central hole in the iris
Iris—coloured ring of muscle tissue
Lens—transparent biconvex lens
Ciliary Body—ring of muscle tissue
Suspensory Ligaments—ligament tissue
Optic Nerve—nervous tissue
b3.1.3-What functions do the main structures of the eye carry out?
Cornea—protects eye, refracts light entering
Pupil—allows light to enter
Iris—alters pupil size by contracting or relaxing
Lens—focuses light clearly onto the retina
Ciliary Body—alters the shape of the lens
Suspensory Ligaments—connects the ciliary muscle to the lens
Optic Nerve—carries nerve impulse to brain
b3.1.3-How are images formed?
The cornea refracts light rays providing most of the focus to the incoming light. The light passes through pupil and is refracted again from lens creating a sharp image on the retina. Light sensitive cells produce a nervous impulse when exposed to light which travels down the optic nerve to the brain.
b3.1.3-What does the ciliary muscle do?
When it contracts, your lens becomes more convex(fatter)so you can focus on nearby things.
When it relaxes, your lens becomes less convex(thinner)so you can focus on distant objects.
b3.1.3-What causes long and short sightedness?
Short sightedness is caused by a persons lens being too strong or eyeball being too long.
Long sightedness is caused by a persons lens being too weak or eyeball being too small.
b3.1.3-What are the two types of photoreceptor cells?
Rods-respond to light, allow you to see in low light levels, not responsive to different colours
Cones-respond to different colours and different cones respond to red, blue and green light
b3.14-What is the function of the brain?
The brain processes all the information collected by receptor cells about changes in your internal and external environment and from your hormonal system and produces a coordinated response.
b3.1.4-What do the 5 main areas of the brain do?
Cerebrum—controls complex behaviour such as learning, memory, personality and conscious thought.
Cerebellum—controls posture, balance and involuntary movements.
Medulla—controls automatic actions such as heart rate and breathing rate.
Hypothalamus-regulates temperature and water balance.
Pituitary Gland-stores and releases hormones that regulate many body functions
