B3.1 Flashcards
What is the function of the central nervous system (CNS)?
Processes information and coordinates responses to stimuli to help us survive.
What do receptor cells do?
Detect a stimulus and convert it into an electrical impulse.
What carries electrical impulses to the CNS?
Sensory neurons
What carries impulses from the CNS to effectors?
Motor neurons.
What is the role of effectors?
Bring about a response — e.g. muscle contraction or hormone secretion.
What is the function of a reflex arc?
To produce a fast, automatic response without involving the conscious brain.
What detects a stimulus in a reflex arc?
Receptors (e.g. thermoreceptors).
What is the path of a reflex arc?
Receptor → Sensory neuron → Relay neuron (CNS) → Motor neuron → Effector.
What is the final result of a reflex arc?
A response — e.g. arm moves away from a hot object.
What is the function of the cornea?
Refracts light into the eye.
What controls how much light enters the eye?
The iris.
What happens in bright light?
Circular muscles contract, radial muscles relax → pupil gets smaller - less light allowed in so it doesn’t damaged retina.
What happens in dim light?
Circular muscles relax, radial muscles contract → pupil gets larger - more light let in
What is the role of the lens?
Focuses light onto the retina.
What does the retina contain?
Light receptors — rods (dim light) and cones (colour).
What connects the eye to the brain?
The optic nerve — carries impulses to the brain.
What causes colour blindness?
A defect or absence of cones in the retina (usually inherited).
What is short-sightedness (myopia)?
Can see near but not far — image focuses in front of the retina.
How is short sightedness treated?
Concave lenses.
What is long-sightedness (hyperopia)?
Can see far but not near — image focuses behind the retina.
How is long sightedness treated?
Convex lenses.
What is the function of the cerebrum?
Controls intelligence, vocabulary, personality, and conscious thought.
What are key features of the cerebrum?
Two cerebral hemispheres - largest part of brain, each half processes info from opposite side of body, grey matter outside (myelinated nerves), white matter inside.
What does the cerebellum do?
Controls voluntary movement and balance.
What is the role of the medulla?
Controls heart rate, breathing rate, and blood pressure.
What is the role of the hypothalamus?
Regulates body temperature and water balance.
What does the pituitary gland do?
Releases hormones like growth hormone into the blood.
Why is investigating brain damage difficult?
Ethical concerns, risk of surgery, limited knowledge, case studies hard to interpret.
Why is treatment of brain damage limited?
CNS cells can’t regenerate well and drugs can’t easily cross the brain’s membranes.
What is the lens?
Transparent biconvex disc - attaches to ciliary muscles by suspensory ligaments
Why is short sightedness formed?
Image focuses in front of retina - eyeball to long or lens too strong
Why is long sightedness formed?
Image focuses behind retina - eyeball too short or lens to weak
How do you focus on nearby objects?
Ciliary muscles contract - lens becomes more convex (fatter)
How do you focus of distant objects?
Ciliary muscles relax - lens less convex (thinner)
What is the peripheral nervous system?
Consists of all the neurones that connect the cns to the rest of the body
